Water Treatment and Reusewith Electrocoagulation inthe Oil & Gas IndustryAuthor: Mauro Capocelli, Researcher, University UCBM – Rome(Italy)

1.Theme descriptionElectrocoagulation (EC) combines conventional treatment ascoagulation and flotation with electrochemistry. The processdestabilizes soluble organic pollutants and emulsified oilsfrom aqueous media by introducing highly charged species thatneutralize the electrostatic charges on particles andoil/emulsions droplets to facilitate agglomeration/coagulation(and the following separation from the aqueous phase). Incomparison with conventional coagulation processes, thesmallest charged particles have a greater probability of beingcoagulated because of the electric field that sets them inmotion. Moreover, an “electrocogulated” flock tends to containless bound water, is more shear resistant and is more readilyfilterable[1].

EC has been known since 1909 (Aluminium/ iron-basedelectrocoagulation patent by A.E. Dietrich)[2]. Is has been(most commonly) used in the oil & gas, construction, andmining industries to separate emulsified oil, petroleumhydrocarbons, suspended solids, heavy metals from effluents.Particularly in the Oil & Gas sector, the EC is fundamental totreat and reuse (on-site) the water needed for the drillingand fracking processes, minimizing the impact of injectionwells. The application market has not yet exploded due to thehigh costs but changes in regulations and growth in the cited

industrial sectors has recently brought electrocoagulation tothe forefront[3].

2.Principles of ElectrocoagulationBasically, the electrocoagulation apparatus consists of asacrificial anode, producing coagulant metal ions, and acathode made of metal plates (both submerged in the aqueoussolution). The electrodes are usually made of cheap and non-toxic metals such as aluminium and iron. The dissolution (inmass), according to the Faraday’s law, is proportional to theapplied current I and the treatment time ts.

Where z is the valence of ions of the electrode material, M ismolar mass of the metal and F is Faraday’s constant (96485C/mol). Coagulation is brought about by the reduction of thenet surface charge; the colloidal particles (previouslystabilized by electrostatic repulsion) can approach closelyenough for Van Der Waals forces to aggregate. The reduction ofthe surface charge is a consequence of the decrease of therepulsive potential of the electrical double layer by thepresence of an electrolyte having opposite charge (Fig. 1).

Fig. 1. – Conceptual representation of the electrical doublelayer in colloidal particles

[4]

The classical representation of EC dissolution with theinduced separation mechanisms (coagulation, flocculation andflotation) is reported in Fig. 2. The following main reactionstake place during EC.

The metals and other contaminants, suspended solids andemulsified oils are entrained within the floc because of theneutralization of surface charges (destabilization).Destabilization also occurs by “sweep flocculation”, whereimpurities are trapped and removed in the amorphous hydroxideprecipitate produced. Microbubbles (mainly of H2 and O2) adhere

to agglomerates helping to separate and lift the flocs up tothe surface. Depending on the application, the final solidsseparation step can be done using settling tanks, mediafiltration, ultrafiltration, and other methods.

Fig. 2 – Schematic representation of typical reactionsduring the EC treatment

Ferrous iron may be oxidized to Fe3+ by oxygen or anodeoxidation and the formation of active chlorine species canenhance the performances of the EC. Both Fe and Al ions

complexes with OH− ions. The formation of these complexesdepends strongly on the pH of the solution, as shown in Fig.

3: above pH 9, Al(OH)4− and Fe(OH)4− are the dominant species.Anions, such as sulphate or fluoride, affect the compositionof hydroxides because they can participate to side reactions

and replace hydroxide ions in the precipitates. Temperatureaffects floc formation, reaction rates and conductivity. Thepollutants’ concentration affects the removal efficiencybecause coagulation follows pseudo second or first-orderkinetics. In fact, Ezechi et al., showed a second orderkinetic of boron adsorption onto Fe(OH)3 in EC. This workreported a removal efficiency of almost 97% using iron plateelectrode (inter-electrode distance of 0.5 cm, 15 mg/lconcentration of boron in produced water, pH 7.84, current

density of 12.5 mA/cm2) .

Fig. 3 – Concentrations of soluble monomeric hydrolysisproducts of Fe(III) and Al(III) at 25°C[5]

This application does not work properly in case of lowconductivity (i.e. less than 300 μS/cm), low suspended solids(turbidity less than 25 NTU or TSS less than 20 mg/L), nonpolar and monovalent contaminates (aqueous salts of Na, K, Cl,F, etc.), non polar and charged particles.

3.Produced water treatment & reuseThe literature reports many application of EC to watertreatment & reuse. Among them, the treatment of oily wastewater and produced water is relevant for the Oil & Gas sector.Produced water (PW) is the water trapped in the reservoir rocksubsists under high pressures and temperatures and brought upalong with oil or gas during production. Other components arethe salts in relation to the source (seawater and groundwater)as well as dispersed hydrocarbons, dissolved hydrocarbons,dissolved gases (such as H2S and CO2), bacteria and otherorganisms, and dispersed solid particles. PW may also includechemical additives (corrosion inhibitors, oxygen scavengers,scale inhibitors, as emulsion breakers and clarifiers,flocculants and solvents) used in pre-treating, in drillingand generally in producing operations as well as in thedownstream oil/water separation process. These chemicalsaffect the oil/water partition coefficient, toxicity,bioavailability, and biodegradability.[6]

PW is considered an industrial waste and its disposal tosurface waters or its evaporation in ponds is subject tostringent environmental regulations. It should be treated andreinjected for pressure maintenance, replacing aquifer wateror should be reused for irrigation or as industrial processwater. Many companies propose their own EC systems(Watertectonics, F&T Water Solutions, Bosque Systems, etc.)

for the treatment of PW. The conference proceedings of IDA [7]gives some interesting examples of EC pretreatment for waterreuse in the Oil and Gas Industry. A thypical process scheme,

taken from a pilot plant presented in the conference7, isreported in Fig. 4.

Fig. 4 – Process scheme of a water reuse treatment plant(EC/UF/CE/RO/UV) and detail of the RO process scheme

Eames reports the case study of the Oil Field in Colombia MetaProvince is provided with EC/DAF/UF/RO for the wastewaterreuse (3,000 BPD of water for Agricultural Irrigation andSurface; Irrigation (<60 ppm sodium) with the characteristicsin Table below. Piemonte et al. also proposed the processanalysis with energy and material balances of a produced water

treatment train including Vibratory Shear Enhanced Processing(VSEP) membrane system (secondary treatment) and RO destinedto the tertiary treatment to achieve the quality needed forwater reuse[8].

[1] IDA

[2] Kuokkanen et al., Recent Applications ofElectrocoagulation in Treatment of Water and Wastewater—AReview. Green and Sustainable Chemistry, 2013, 3, 89-121

[3]http://www.wateronline.com/doc/a-shocking-approach-to-wastewater-treatment-0001

[4] Mikko Vepsäläinen. PhD Thesis. Electrocoagulation in thetreatment of industrial waters and wastewaters. VTT SCIENCE 19JULKAISIJA – UTGIVARE – PUBLISHER (2012)

[5] Mikko Vepsäläinen. PhD Thesis. Electrocoagulation in thetreatment of industrial waters and wastewaters. VTT SCIENCE 19JULKAISIJA – UTGIVARE – PUBLISHER (2012)

[6] Gomes et al., TREATMENT OF PRODUCED WATER BYELECTROCOAGULATION

[7] IDA (2013) Water Recycling and Desalination in the Oil &Gas Industry. Proceeds to Benefit Water-related HumanitarianProjects.

[8] Piemonte et al., Reverse osmosis membranes for treatmentof produced water: a process analysis. Desalination and WaterTreatment 55, 3, 2015. Reverse osmosis membranes for treatmentof produced water: a process analysis

Process and CatalystInnovations in Hydrocrackingto Maximize High QualityDistillate FuelAuthor: Vincenzo Piemonte, Associate Professor, UniversityUCBM – Rome (Italy)

1.Theme descriptionWorldwide economic growth continues to drive demand fortransportation fuels, and in part

There are several processes presently able to meet individualrefinery needs and project objectives[2]. In particular, UOPLLC Company is one of the most active society in thisfield[3]. The basic flow schemes considered by UOP are single-stage or two-stage design. UOP two-stage Unicracking processflow schemes can be a separate hydrotreat or a two-stage

process as shown in Figure 1. In the separate hydrotreat flowscheme the first stage provides only hydrotreating while inthe two-stage process the first stage provides hydrotreatingand partial conversion of the feed. The second-stage providesthe remaining conversion of recycled oil so that overall highconversion from the unit is achieved. These flow schemes offerseveral advantages in processing heavier and highlycontaminated feeds. Two-stage flow schemes are economical whenthe throughput of the unit is relatively high.

The design of hydrocracking catalyst changes depending uponthe type of flow scheme employed. The hydrocracking catalystneeds to function within the reaction environment and severitycreated by the flow scheme that is chosen.

2.Enhanced Hydrocracking ProcessesDuring the early years of hydrocracking, refiners were mainlyinterested in maximizing production of naphtha for reformingto high octane gasoline. However with advancements inhydrocracking catalyst technology, and the demand formaximizing distillate yields from heavier feedstocks, two-stage design offers a cost-effective option for a largercapacity maximum distillate unit operation.

A major difference between the first and second stagehydrocracking reactor reaction environments lies in the verylow concentrations of ammonia and hydrogen sulfide in thesecond-stage (see figure 2). The first-stage reactionenvironment is rich in both ammonia and hydrogen sulfidegenerated by hydrodenitrogenation and hydrodesulfurization ofthe feed. This significantly impacts reaction rates,particularly cracking reaction rates, leading to differentproduct selectivity and catalyst activity between the two-stages. The catalyst system can be optimized to obtain ahighly distillate selective overall yield structure. Optimum

severity can be set for each stage to achieve catalyst lifetarget with minimum catalyst volume. Overall, the two-stagedesign allows optimization of conversion severity between thetwo stages, maximizing overall distillate selectivity. Newadvances in the two-stage Unicracking process design includeseveral innovations in each reaction section of the design.The pretreating section uses a high activity pretreatingcatalyst that allows hydrotreating at a higher severity,providing good quality feed for the first-stage hydrocrackingsection and enabling maximum first-stage selectivity to highquality distillate. The second-stage is optimized by use ofsecond-stage hydrocracking catalyst that is specificallydesigned to take advantage of the cleaner reactionenvironment. The second-stage catalyst is designed so that thecracking and metal functions are balanced. At the same timethe second-stage hydrocracking severity is optimized so thatmaximum distillate selectivity is obtained from the second-stage of hydrocracking.

Figure 1 – Two-stage Unicracking Process Flow Schemes.

Figure 2 – Two-stage Unicracking Process Flow Schemes.

3.Catalyst DevelopmentDesigning catalysts which can be successfully used forprocessing heavy feeds requires an understanding of theinteractions of many factors. Detailed knowledge isincreasingly important for controlling reaction pathways toachieve specific product types to meet today’s market demands.The key considerations for optimal catalyst design requiregood understanding of the molecular transformations of feed toproduct with respect to catalyst functions and processvariables.

Such consideration involves process severity and its impact onthe extent of secondary cracking in the hydrocracking reactor.The key steps in the mechanism of hydrocracking paraffinsconsists of a sequence of steps beginning with dehydrogenationat metal sites to form olefinic intermediates which are thenprotonated at the acid sites to form the reactive carbeniumions. These, in turn, can isomerize and leave the catalyst

surface without cracking after picking up a hydride ion at themetal sites. Alternatively, they can crack to form smalleralkanes which then leave the catalyst surface as hydrocrackedproducts[4]. This process of isomerization and cracking toprimary cracked products is referred to as “ideal cracking”and therefore it does not involve secondary cracking of theinitially formed product. Secondary cracking often results inthe formation of light ends which are of low value to a unitoperating to make liquid transportation fuels.

Control of this sequence of steps to stop the reactions afterformation of primary products is accomplished by carefulselection of catalyst properties such as the strength anddistribution of acid sites and tailoring the hydrogenationfunction to fit the acidity on the catalyst. In addition,particularly when heavy feedstocks are being processed,elimination of diffusion constraints which contribute tosecondary cracking is accomplished by strict control of poresize and pore geometry of the catalyst to match the moleculardimensions of a given feed. These catalyst properties mustalso be matched to the service environment in which thecatalyst is intended to function, including the recycle gascomposition and the reactor pressure. Thus, detailed knowledgeof molecular types and size in the feed is incorporated intocatalyst selection criteria in order to make criticaldetermination of the appropriate catalytic components to matchfeed for a given unit.

Figure 3 – Second-Stage Unicracking Catalyst Design

Hydrocracking catalysts are typically dual function catalysts,containing an acid-function for cracking and a metal-functionfor hydrogenation. As shown in Figure 3, a good hydrocrackingcatalyst, amorphous or zeolitic, is designed to balance thesetwo functions for optimum performance. In the figure twoarrows indicate the type of functions (acid and metal) and theheight of the arrows indicates the strength of the individualfunctions. A catalyst with proper balance of these twofunctions performs optimally in terms of desired productselectivity and catalyst temperature activity/stability.However if a catalyst, designed for the first-stage sourreaction environment typical of first-stage operation, is putin the cleaner reaction environment of the second-stage, asignificant boost in the cracking function is observed whilethe performance of the metal-function remains basicallyunchanged. Thus, the catalyst that was in good balance for thefirst-stage environment becomes unbalanced for the second-

stage environment resulting in sub-optimal performance. Thisdifference is exacerbated, as the temperature required toachieve desired conversion is reduced. On the other hand thereduction in temperature reduces the metal functionality thusreducing hydrogenation. Therefore, for ideal second-stagecatalyst, it is desired that the acidity of the crackingmaterial is weak with a stronger metal-function so that eventhough the catalyst may appear imbalanced for the first stagesour environment it will be in balance in the second-stagereaction environment. Applying this design approach, UOPrecently developed a new second-stage catalyst achievinghigher distillate selectivity than the current UOP standarddesign.

Enhanced two-stage performance is achieved by optimized first-and second-stage conversion severity and application of thenew second-stage catalyst. This results in significantlyimproved overall C5+ yields and a product slate which is moreselective to a high quality heavy diesel product.

The enhanced two-stage design has improved distillateselectivity and the product slate is diesel selective withlower light-end production resulting in 7-10% lower hydrogenconsumption. The product qualities are similar or better. Theimproved performance is achieved by optimum processingseverity and use of new second-stage hydrocracking catalyst.

[1] Purvin & Gertz Inc., “Global Petroleum Market Outlook:Prices And Margins”, Fourth Quarter 2007 Update

[2] Thakkar V. P. et al, “Innovative HydrocrackingApplications For Conversion of Heavy Feedstocks”, AM-07-47

NPRA 2007 Annual Meeting

[3] Remsberg, Charles and Higdon, Hal, “Ideas for Rent The UOPStory”, p. 326, 1994

[4] Coonradt, H. L. and Garwood, W.E., Mechanism ofHydrocracking Reactions of Paraffins and Olefins, Ind. Eng.Chem. Process Des. Dev., 3 (1964) 38

Waste to Fuel TechnologiesAuthor: Mauro Capocelli, Researcher, University UCBM – Rome(Italy)

1.Theme descriptionThe growing concerns about climate change as well as themanagement of ever increasing liquid and solid wasters highlypushed the R&D in waste-to-fuel conversion[1]. Thetransformation of wastes into fuels can be realized by thedifferent processes represented in Fig. 1 (extending the

classification of 2nd generation of biofuels). The directincineration of waste enables the highest recovery of theenergy content from the thermodynamic point of view. On theother hand, depending on the composition, the emissions of thecombustion process can be characterized by the presence ofpollutants such as HCl, HF, NOx, SO2, VOCs, PCDD/F, PCBs andheavy metals[2].

Fig. 1 – Waste-to-Fuel Conversion technologies

Besides incineration, other thermochemical processes (seeFig.1) such as pyrolysis, gasification and plasma-basedtechnologies, have been developed to selected waste streams.In general, thermal treatments of biomasses (and wastes) allowto get a wide spectrum of fuels (gaseous, liquid and solid)and many chemicals as co-product; the specific treatment ischosen according to the final fuel & chemicals products[3].Many companies are using municipal solid waste (MSW)thermochemical conversion methods: Hitachi MetalsEnvironmental Systems, Ebara/Alstom, Enerkem, Foster Wheeler,Nippon Steel, PKA, SVZ, etc. The first industrial-scale MSW tobiofuel facility opened in Edmonton on 2014 by Enerkemconverts 100000 t/year of municipal waste into chemicals andbiofuels and is able to divert 90% of the residential wastefrom landfills[4].

The multiple synthetic conversion routes of major biofuelsproduced (Biofuel Flow) from first and second-generationbiomass feedstock is represented in Fig 2. Conversion throughbiochemical and physiochemical processes is playing andimportant role in the recent biorefineries. These, followingthe paradigm of zero-waste and zero-emission, allow theextraction of valuable substances processing biomass into a

spectrum of marketable products and energy and are expected toplay a fundamental role in the future low carbon economy[5].Moreover, biorefineries would be very attractive from anemployment creation perspective, resulting in significantlymore jobs per unit of biomass feedstock than conventionalprocesses[6]. A brief review of the processes and technologiescited in Fig. 1 is given in the following.

Fig. 2 – Biofuel flow[7]

2.Thermochemical conversionThe pyrolysis occurs without oxygen at atmospheric pressuresin a temperature range of 250-900°C. Generally, high vapourresidence time favours char production (at lower processtemperature) and gas yield (higher temperatures), whereas

moderate and short vapour residence times favour the liquidproduction. In fast pyrolysis, the heating occurs at amoderate temperature (400-550 °C) with very high heatingvelocities (100°C/s). A successive rapid quenching is requiredto condense the vapors, to minimize secondary reactions andcoalescence or agglomeration (aerosols formation). The heatduty can be recovered from the combustion of part of theproduced syngas. The liquefaction by pyrolysis of solid wasteshas been widely reviewed in the last years, due to theincreasing interest in integrated technologies to derive fuelsand chemicals from solid wastes.[8] A review on processconditions for optimum bio-oil yield in hydrothermalliquefaction of biomass is given by Akhtar and Amin[9].

Municipal plastic wastes, through the cracking and pyrolysis,can produces bio-oil of a good quality, a valid option toplastic recycling or direct combustion[10]. For example,Sharma et al. 2014 repots a study of high-density polyethylenegrocery bags pyrolysis to produce alternative diesel fuels orblend components for the petroleum diesel (saturated aliphaticparaffins) of very good quality (with cetane number andlubricity). Many examples of pyrolysis plants are located inJapan. Mogami Kiko owns a Pyrolysis plant (Capacity of 200

kg/h) that produces 80-100 Nm3/h of gas with LHV of 5000-6000

kcal/Nm3 30-40 kg/h of tar and 20-30 kg/h of char, processingseveral kinds of plastic in a rotary kiln. Environment Systemhave implemented the pyrolysis of thermoplastics waste(without chlorine) in a tank reactor with continuous feedingof scrap film (extruder). Toshiba implemented the continuousfeeding of thermoplastics waste (no chlorine, 40 tons/day)into a rotary kiln (externally heated) producing liquid andgaseous hydrocarbons and 4MW cogeneration. Samshiro et al.described the fuel oil production from MSW in sequentialpyrolysis and catalytic reforming reactors[11]. Wong et al.[12], report alternative solutions to solid waste pyrolysis asfluidized bed and supercritical water. Although microwave-

assisted pyrolysis is another possible solution to theproblem, especially in the treatment of commingled plasticwaste, this relatively new concept requires more feasibilitystudies.

Gasification, operating at high temperatures (>700 °C) withoutcombustion results into solid and gaseous products.. Althoughassociated with lower power production and higher complexity,the gasification of solid wastes can count about a hundred of

operating plants having a capacity in the range 10–250∙103 t/yand represents a valid alternative in the field of wastemanagement[13]. Moreover, gasification-based technologiesenable the reduction of waste amount to disposal in comparisonto the conventional combustion-based WtE units and allowsalternative strategies for the syngas utilization[14].Therefore, gasification of waste has been exploited asalternative to combustion for the waste to energy (WtE)processes in order to improve the performances and thedistributed WtE policy.

By using multiple high-temperature processes, including thebreaking down of organics through plasma arcs, enables theproduction of a mixture of hydrogen and carbon monoxide. Inthis way, metals and other inorganic materials in garbage canbe isolated and recycled; the combination of high temperaturesand an oxygen-poor environment prevents the production ofdioxins and furans; eventually the syngas can either bedirectly burned in gas turbines to produce electricity, or itcan be converted into other fuels, including gasoline andethanol. Enea reported several experimental campaign conductedat lab and pilot-scale devices[15]. Molino et al. investigatedthe steam gasification of scrap tires as a sustainable andcost-effective alternative to tire landfill disposal; steamactivation of the char derived from the tire residues of thegasification process was carried out at constant temperatureand feeding ratio between gasifying agent and char, usingdifferent activation times (180 and 300 min)[16].

3. Physicochemical conversionThese methods are based on the separation of useful chemicalcompounds with physicochemical extraction such as cold pressextraction, supercritical fluid extraction, and microwaveextraction. In the recent years, cavitation assisted (e.g.ultrasound assisted) extraction process has been utilized forthe biomass pretreatment, delignification and hydrolysis,extraction of oil, fermentation and synthesis ofbioalcohol[17]. Transesterification of plant or algal oil is astandardized process by which triglycerides are reacted withmethanol in the presence of a catalyst to deliver fatty acidmethyl esters (FAME) and glycerol. The extracted vegetableoils or animal fats are esters of saturated and unsaturatedmonocarboxylic acids with the trihydric alcohol glyceride(triglycerides) which can react with alcohol in the presenceof a catalyst, a process known as transesterification(according to the following simplified scheme of reactions).

The simplified process scheme is given in Fig. 3. From aneconomic point of view, the production of biodiesel has provento be very feedstock-sensitive. Leung et al., report a reviewon biodiesel production using catalysedtransesterification[18]. Waste vegetable oil (WVO) can also beconverted after refinement. It has a low sulphur content and

it is not associated to change in the land use. Theutilization of waste cooking oils is explained in details inthe review of Kulkarni et al.[19]

Fig. 3 – Simplified process flow chart of alkali-catalyzedbiodiesel production.

4.Biochemical conversion In general, the conversion of biodegradable waste or energycrops, through anaerobic digestion, produces a gaseous fuelcalled biogas (mainly methane and carbon dioxide). Insimilarity, the wastes in landfill generates gases (landfillgases, LFG) that can represent a source of renewable energy.Some examples of commercial conversion processes (typically

run via anaerobic digestion or fermentation by anaerobes) arereported in the table below (extracted from).

Microbial hydrogen production using anaerobic fermentativebacteria is considered a cost effective technology because theprocess can use waste materials or wastewaters. The biologicalproduction pathway of hydrogen and methane (by microorganisms)can be divided into two main categories: by photosyntheticbacteria under anaerobic or semi-anaerobic light conditions,and by chemotrophic anaerobic bacteria[20]. During theprocess, organic matter is converted to volatile fatty acidsthrough hydrolysis and acidogenesis (acidogenic fermentationor dark fermentation). This latter produces fuel gas withhigher rates. Hydrogen yields from various crop substrates isreported by Mei Guo et al.[21] Kurniawan et al. reported astudy on acid fermentation combined with post-denitrificationfor the treatment of primary sludge[22].

Since 1980 US Department of Energy supported the AquaticSpecies Program (ASP) to exploit algae as fuels (mainly oil

from microalgae). The ASP firstly worked on growing algae inopen ponds and on studying the the impacts of differentnutrient and CO2 concentrations. The program ended in 1995 dueto financial issues. In recent years, the energy securityrisks and the advancements in biotechnology (the ability togenetically engineer algae to produce more oils and convertsolar energy more efficiently), has rebirth the R&D in thisfield[23]. Although the issue of low oil productivity peracre, the cultivation of oleaginous microorganisms(microalgae) can contribute to the biofuel production and tothe mitigation of carbon emissions. In this files, furtherimprovements are also needed in the downstream processes andthe light supply systems.

[1] Piemonte, V., Capocelli, M., Orticello, G., Di Paola, L.,2016 Bio-oil production and upgrading in book: MembraneTechnologies for Biorefining, pp.263-287

[2] Bosmans, A., et al., The crucial role of Waste-to-Energytechnologies in enhanced landfill mining: a technology

review, Journal of Cleaner Production (2012),doi:10.1016/j.jclepro.2012.05.032.

Barba D, Capocelli M, Luberti M, Zizza A. Process analysis ofan industrial waste-to-energy plant: theory and experiments.Process Safe Environ 2015;96:61–73.

[3] Mckendry, P., 2002. Energy Production from Biomass (Part2): Conversion Technologies. Bioresource Technology 83, 47-54.

[4]http://cleantechnica.com/2014/06/09/first-industrial-scale-municipal-solid-waste-biofuel/

[5] Industrial Biorefineries and White Biotechnology.

http://dx.doi.org/10.1016/B978-0-444-63453-5.00001-X

Copyright © 2015 Elsevier B.V.

[6] Patricia Thornley*, Katie Chong, Tony Bridgwater. European biorefineries: Implications for land, trade

and employment. Environmental Science & Policy 37 (2014) 255–265

[7] D.King et al., The future of industrial Biorefineries.2010 World Economic Forum.

[8] Isahak, Wan Nor Roslam Wan, Mohamed W M Hisham, Mohd AmbarYarmo, and Taufiq Yap Yun Hin. 2012. “A Review on Bio-OilProduction from Biomass by Using Pyrolysis Method.” Renewableand Sustainable Energy Reviews 16 (8). Elsevier: 5910–23.doi:10.1016/j.rser.2012.05.039.

Bridgwater, A.V. 2012. “Review of Fast Pyrolysis of Biomassand Product Upgrading.” Biomass and Bioenergy 38: 68–94.doi:10.1016/j.biombioe.2011.01.048.

[9] Javaid Akhtar, Nor Aishah Saidina Amin. A review onprocess conditions for optimum bio-oil yield in hydrothermalliquefaction of biomass. Renewable and Sustainable EnergyReviews15 (2011) 1615–1624

[10] Demirbas, Ayhan. 2004. “Pyrolysis of Municipal PlasticWastes for Recovery of Gasoline-Range Hydrocarbons.” Journalof Analytical and Applied Pyrolysis 72 (1): 97–102.doi:10.1016/j.jaap.2004.03.001.

[11] Mochamad Syamsiro et al. / Energy Procedia 47 ( 2014 )180 – 188

[12] S.L. Wong et al. / Renewable and Sustainable EnergyReviews 50 (2015) 1167–1180

[13] Diego Barba, Mauro Capocelli, Giacinto Cornacchia,Domenico A. Matera. Theoretical and experimental procedure forscaling-up RDF gasifiers: The Gibbs Gradient Method. Fuel 179(2016),60–70.

[14] Arena U, Di Gregorio F. Element partitioning in

combustion- and gasificationbased waste-to-energy units. WasteManage 2013;33:1142–50. Arena U, Ardolino F, Di Gregorio A.Life cycle assessment of environmental performances of twocombustion- and gasification-based waste-to-energytechnologies. Waste Manage 2015;41:60–74.

[15] Galvagno S, Casu S, Casciaro G, Martino M, Russo A,Portofino S. Steam gasification of refuse-derived fuel (RDF):influence of process temperature on yield and productcomposition. Energy Fuels 2006;20:2284–8. Portofino S,Donatelli A, Iovane P, Innella C, Civita R, Martino M, et al.Steam gasification of waste tyre: influence of processtemperature on yield and product composition. Waste Manage2013;33:672–8. Galvagno S, Casciaro G, Casu S, Martino M,Mingazzini C, Russo A, et al. Steam gasification of tyrewaste, poplar, and refuse-derived fuel: a comparativeanalysis. Waste Manage 2009;29:678–89

[16] Molino et al., Ind. Eng. Chem. Res. 2013, 52,12154−12160

[17] Amrita Ranjan, Ultrasound-Assisted Bioalcohol Synthesis:Review and Analysis. RSC Advances A. Ranjan, S.

Singh, R. S. Malani and V. S. Moholkar, RSC Adv., 2016, DOI:10.1039/C6RA11580B.

[18] D.Y.C. Leung et al. / Applied Energy 87 (2010) 1083–1095

[19]Waste Cooking OilsAn Economical Source for Biodiesel: AReview. Mangesh G. Kulkarni and Ajay K. Dalai*Ind. Eng. Chem.Res., Vol. 45, No. 9, 2006 Waste Cooking OilsAn EconomicalSource for Biodiesel: A Review

Mangesh G. Kulkarni and Ajay K. Dalai*

[20] Cheong et al., Production of Bio-Hydrogen by MesophilicAnaerobic Fermentation in an Acid-Phase Sequencing BatchReactor. Biotechnology and Bioengineering, 96, 2007

[21] Mei Guo et al., Hydrogen production from agriculturalwaste by dark fermentation: A review. International Journal ofHydrogen Energy (2010) 1-14.

[22] Kurnawian et al., Acid Fermentation Process Combined withPost Denitrification for the Treatment of Primary Sludge andWastewater with High Strength Nitrate. Water 2016, 8, 117;doi:10.3390/w8040117

[23] http://allaboutalgae.com/history/

Waste Heat Recovery in theOil & Gas SectorAuthor: Mauro Capocelli, Researcher, University UCBM – Rome(Italy)

1.IntroductionWaste heat recovery is a process that involves capturing ofheat exhausted by an existing industrial process for otherheating applications, including power generation. Technavioforecasted the global waste heat recovery market in oil andgas industry to grow at a CAGR of 7.6% during the period2014-2019[1]. The sources of waste heat mainly includedischarge of hot combustion and process gases into theatmosphere (e.g. melting furnaces, cement kilns,incinerators), cooling water sand conductive, convective, andradiative losses from equipment and from heated products. Todesign the waste heat reclamation unit, it is necessary tocharacterize the stream in terms of availability, temperature,pressure and presence of contaminants such as particulate andcorrosive gases. There are two main goals of recovering wasteheat from industries: thermal energy recovery (both internallyand outside from the plant) and electrical power generation.

Fath & Hashem compared these two solution for the recovery ofwaste heat in an oil refinery plant located at Bagdad,Iraq[2]. For the overall energy system efficiency, it isnowadays fundamental to improve the utilization of low-temperature heat streams, primarily for thermal applicationslike heating, ventilation, cooling, greenhouses, etc. Oda &Hashem investigated in 1990 the selection of differentstrategies (air conditioning, food industry and agriculturaluses) for an industrial area around including a refinery[3].Nonetheless, also for low temperature sources, someinnovations have been proposed in order to produce electricityfor standalone plants and/or exploiting the resources thatcannot be properly used for direct thermal applications. Inthe following, all these aspects are faced and some from themost recent and interest development in the R&D are reported.

Fig.1 – Estimated U.S. Energy use in 2012.

2. Thermal energyElectrical EnergyTraditionally, waste heat of low temperaturerange (0-120 °C) cannot profitably implemented for electricitygeneration because of the low Carnot efficiency (typicallyending up with 5-7% net electricity). In the field of thermalenergy direct utilization, two main options are available:waste heat recycling within the process (Fig. 2) or recoveringwithin the plant or industrial complex.

Fig 2 – Rotary regenerator on a Melting Furnace

The main utilizations in the industrial systems are thepreheating of combustion air and load or the steam generation.Transfer to liquid or gaseous process streams is also commonin petroleum refineries where the operation (distillation,thermal cracking…) requires large amounts of energy that canbe recovered from exothermic reactions or hot process streamsin integrated systems.

Doheim et al.[4]described the integration of rotatingregenerative heat exchangers in 4 refining processes (twocrude distillation units, a vacuum distillation unit, and aplatforming unit) in order to reduce the current losses (25 to62% of total heat input) to the values of 9.9 to 37.3%. At the

low temperature (<200° C), the best uses are the regenerative(recuperative) heating of feed-stocks (process internalreuse), district heating and LP steam generation. Districtheating (or tele-heating) is a system for distributing heatgenerated in a centralized location for residential andcommercial requirements via a network of insulated pipes(mainly or pressurized hot water and steam). In alternative,low temperature waste heat can be used for the production ofbio-fuel, space heating, greenhouses and eco-industrial parks.In the industrial complexes, requiring large amount offreshwater and located near the sea, a viable alternative isthat of desalinate seawater via thermal processes as MultipleEffect Distillation and Multi Stage Flash Desalination inorder to obtain demineralized, potable or process water.

The generation of electricity from thermal energy should betaken into account if there are not viable options of in houseutilization of additional process heat or neighbouring plants’demand. The most commonly system involves the steam generationin a waste heat boiler linked to a steam turbine in a RankineCycle (RC). Industrial examples can be easily found in theliterature. Steam Energy WHP from Petroleum Coke Plant,located at Port Arthur (Texas), recovers energy from threepetroleum-coke calcining kilnsat temperature higher thant500°C for producing LP steam (to use at an adjacent refinery)and 5 MW of power(saving an estimated amount of 159,000 tonsper year of CO2 emission).

Since the thermal efficiency of the conventional steam powergeneration becomes considerably low and uneconomical whensteam temperature drops below 370 ˚C, the Organic RankineCycle (ORC) utilize a suitable organic fluid, characterized byhigher molecular mass, a lower heat of vaporization and lowercritical temperature than water[5] (silicon oil, propane,haloalkanes, isopentane, isobutane, pxylene, toluene, etc.).

Fig. 3.- T-s diagram of a ciclo- pentane ORC cycle

These enable the utilization of lower temperatures (ifcompared to the RC) and a “better”coupling (lower entropygeneration) with the heat source fluid to be cooled[6]. Thehigher molecular mass enables compact designs, higher massflow and higher turbine efficiencies (as high as 8085%).However, since the cycle works at lower temperatures, theoverall efficiency is only around 1020%. As abovementioned, itis important to remember that low temperature cycles areinherently less efficient than hightemperature cycles. Jung etal., 2014, reported a techno-economical evaluation of an ORCcycle (with pure refrigerant and mixtures of R123, R134a,R245fa, isobutane, butane, pentane) to recover the heat from aliquid kerosene to be cooled down to control the vacuumdistillation temperature[7]. An example of a recent successfulORC installation is at a cement plant in Bavaria (Germany) torecover waste heat from its clinker cooler (exhaust gas @500°C) providing the 12% of the plant’s electricityrequirements and reducing the CO2 emissions by approximately7000 tons/year. Several R&D projects[8]and commercial

plants[9]are reported in the references (footnotes).An exampleof T-s diagram of an ORC with Cyclo-Pentane (MW 70, boilingpoint 49,5°C) developed by GE[10]is showed in Figure 3.Also,ElectraTherm applies proprietary ORC to generate power fromlow temperature heat by utilizing, as fuel in industrialboilers, the natural gas that would otherwise be flared[11].

The Kalina cycle(KC)utilizes a mixture of ammonia and water asthe working fluid (with a variable temperature duringevaporation). It was invented in the 1980s and the first powerplant (6.5 MW, 115 bara, 515 ºC )was constructed in California(1992) and followed by many plants in Japan, Pakistan andDubai.[12]The KC allows a better thermal matching with thewaste heat source and with the cooling medium in the condenserachieving higher energy efficiency.Although the Kalina systemshave the highest theoretical efficiencies, their complexitystill makes them generally suitable for large power systems ofseveral megawatts or greater.

Fig. 4. – H-T energy recovery in the Kalina Cycle11

In addition to these cycles, some advanced technologies in theresearch and development stage can generate electricitydirectly from heat. These technologies include the Stirlingengine[13], thermoelectric, piezoelectric, thermionic, andthermo-photovoltaic (thermo-PV) devices. Although they couldin the future provide additional options for carbon-free powergeneration, nowadays show very low efficiencies. Keeping inmind that a Carnot engine operating with a heat source at150ºCand rejecting it at 25ºC is only about 30% efficient, allthese system shows global efficiencies in the range 1-10%.Asan example, in the piezoelectric power generation(PEPG), athin-film membrane is used to create electricity frommechanical vibrations from a gas expansion/compression cyclefed by waste heat (150-200°C). The temperature change (acrossa semiconductor),inducing a voltage (through a phenomenonknown as the Seebeck effect), is implemented in theThermoelectric generation(TEG)[14].Öström and Karthäuserrecently claimed a method for the conversion of lowtemperature heat to electricity and cooling,comprisingCO2 absorption and an expansion machine[15].

Finally, recent R&D efforts in the use of saline solutions atdifferent concentrations enabled the heat conversion intoelectricity in the lowest temperature range of application.This is possible by making use of heat engine based onSalinity Gradient Energy(SGE) (or Salinity Gradient Power,SGP) technologies.

Salinity Gradient energy is a novel non-conventional renewableenergy related to the mixing of solutions with differentsalinity levels, as occurs in nature when a river dischargesinto the sea. Clearly,when this mixing process spontaneouslyoccurs, the associated energy is completely dissipated duringthe process. Conversely,this energy can be harvested byadopting a suitable device devoted to perform a ”controlledmixing” of the two streams at different salinity (e.g. river

water and seawater).Depending on the device type, differenttechnologies have been proposed so far: the ChemicalEngineering Research group of the University of Palermo,involved in this field of R&D activities[16], recently editeda book[17] where Pressure Retarded Osmosis (PRO), ReverseElectrodialysis (RED) and Accumulator mixing (AccMix) areindicated as the most promising technologies.

When employed within a closed loop,each SGP technology can beused to convert waste heat into electricity. This concept isnamed Salinity Gradient Power Heat Engine (SGPHE) (Figure 5)and consists of two main units:

the SGP unit devoted to mixing two solutions ati.different salt concentration in order to convert theGibbs free energy of the relevant salinity gradient intovaluable power;a regeneration unit which employs unworthy waste heat atii.very low energy levels (i.e. 50-100°C) to separate againthe two streams thus restoring the initial salinitygradient and closing the cycle.

Fig. 5 – Scheme of a SGP Heat Engine

The adoption of the closed loop opens room to a large varietyof advantages and possibilities with respect to open-loop SGPtechnologies. Just as an example, the closed loop does notrequire the need of natural/artificial basins of solutions atdifferent salt concentration in the same area. More important,no pre-treatments are necessary and any kind of solute orsolvent can be employed with the aim of maximizing the powerproduction and the cycle efficiency. In this regard, accordingto recent estimates, it appears that SGPHE (i) can be operatedat very low temperatures where no alternative technologiesexist and (ii) can potentially achieve exergetic efficiencieshigher than any other technology[18].

[1] Global Waste Heat Recovery Market in oil and Gas Industry2015-2019 by Infiniti Research Limited (2015).

[2]H.E.S. Fath, H.H. Hashem. Waste heat recovery of dura(Iraq) oil refinery and alternative cogeneration energy plant.Heat Recovery Systems and CHP 8, Issue 3, 1988, 265-270

[3]Oda & Hashem, 1990. Proposals for utilizing the waste heatfrom an oil refinery. Heat Recovery Systems and CHP, 10, Issue

1, 1990, Pages 71-77

[4]M.A. Doheim †, S.A. Sayed, O.A. Hamed. Energy analysis andwaste heat recovery in a refinery. Energy

Volume 11, Issue 7, July 1986, Pages 691-696

[5]Bahram Saadatfar, Reza Fakhrai and TorstenFransson, JMESVol 1 Issue 1 2013

[6]J. Larjola/lnt. J. Production Economics 41 (1995) 227-235

[7] H.C. Junga, Susan Krumdiecka, , , Tony Vranjes Feasibilityassessment of refinery waste heat-to-power conversion using anorganic Rankine cycle. Energy Conversion and Management.Volume 77, January 2014, Pages 396–407

[8]http://www.lttt.uni-bayreuth.de/en/projects/Fachgruppe-ESuT/

[9]http://www.ormat.com/organic-rankine-cycle

http://www.atlascopco-gap.com/fileadmin/download/brochure/AC-ORC-BRO.pdf

http://www.alfalaval.com/waste-heat-recovery/profiting-on-waste-heat/

[10] Development and Applications of ORegen Waste HeatRecovery Cycle. Development and Applications of ORegen WasteHeat Recovery Cycle

Andrea Burrato

© 2015 General Electric Company. All rights reserved

[11]https://electratherm.com/electratherms-waste-heat-to-power-technology-reduces-flaring-at-oil-well/

[12]http://www.heatispower.org/wp-content/uploads/2013/11/Recurrent-Eng-macwan_chp-whp2013.pdf

http://www.globalcement.com/magazine/articles/721-kalina-cycle-power-systems-in-waste-heat-recovery-applications.

[13] A.V. Mehta, R.K. Gohil ,J.P. Bavarv, B.J. Saradava. Waste

heat recovery using Stirling Engine. IJAET/Vol.III/ Issue I/2012/305-310

[14]https://www.alphabetenergy.com/how-thermoelectrics-work/

[15]US 20130038055 A1Method for conversion of low temperatureheat to electricity and cooling, and system

[16]L. Gurreri et al., 2014. CFD prediction of concentrationpolarization phenomena in spacer-filled channels for reverseelectrodialysis. Journal of Membrane Science, 2014, vol. 468,pag. 133-148.

Tedesco et al., 2015. A simulation tool for analysis and2015.design of reverse electrodialysisusing concentratedbrines. Chem. Eng. Res. Des. 93, 441–456M.

Tedesco et al., 2016. Performance of the first Reverse2016.Electrodialysis pilot plant for power production fromsaline waters and concentrated brines. Journal ofMembrane Science, 2016, 500, 33-45.

Bevacqua et al., 2016.Performance of a RED system with2017.Ammonium Hydrogen Carbonate solutions. Desalination andWater Treatment, in press. doi:10.1080/19443994.2015.1126410

[17]A. Cipollina, G. Micale, Sustainable Energy from SalinityGradients, 1st ed., Woodhead Publishing – Elsevier, 2016,isbn-9780081003121

[18]A. Tamburini, A. Cipollina, M. Papapetrou, A. Piacentino,G. Micale, Salinity gradient engines, Chapter 7 in:Sustainable Energy from Salinity Gradients, 1st ed., WoodheadPublishing – Elsevier, 2016, isbn-9780081003121

In-Situ Remediation of Soil,Sediments, and GroundwaterContaminated by HazardousSubstancesAuthor: Mauro Capocelli, Researcher, University UCBM – Rome(Italy)

1.Theme description

Highly polluted sites are present all over the world andparticularly in countries that, in the last years, have seenuncontrolled and unplanned economic development. They are theresult of earlier industrializationand poor environmentalmanagement practices that caused the alteration of groundwaterand surface water, air quality, the hampering soil functions,and the polluting in general. In Europe there are about 500000contaminated sites and two million of potentially contaminatedsites. These are often made from the retired industrial,extractive and military activities[1].The U.S. Department ofEnergy (DOE) manages an inventory of sites including 6.5trillion liters of contaminated groundwater (equal to aboutfour times the daily U.S. water consumption) and 40 millioncubic meters of soil and debris contaminated withradionuclides, metals, and organics. Some of the maincontamination sources in this field are depicted in Figure1[2].

Remediation represents the set of solutions such as the

treatment, the containment or the removal/degradation ofchemical substances or wastes so that they no longer representan actual or potential risk to human health or theenvironment, taking into account the current and intended useof the site[3]. As described by EPA, any Remediationmanagement plan considers complex systems involving differentpollutants and polluted matrix and should include all theimpacted environmental aspects such as air quality, noise,surface water, soil quality, ground water management, floraandfauna, heritage as well as social, structural and saferaspect. The dispersion of the Non Aqueous liquid phase (NAPL)in Figure 1 depends on the site geotechnical characteristics,the aquifer relative positions and the pollutant chemicalproperties. Sometimes the contamination sources succeeds inreaching the groundwater pollution, such as at solid wastelandfills where chlorinated organic compounds reach thegroundwater due to rainfall water leaching.

Figure 1 – Site contamination sources and mechanisms ofdispersion

2.Techniques and technologiesTypical pollutants in this sector are aromatic hydrocarbons,heavy metals, pesticides as well as biological contaminants.The choice of a contaminated soil remediation technology isbased oneconomic factors, the site-specific characteristicsand of the remediation goal.Remediation technologies can berealized both on-site and off-site and act mainlybyTransformation (degradation of complex organic compounds tosimpler intermediate, possibly up to the full mineralization)

and removal from the contaminated matrix, typically for heavymetals, already in elemental form, which cannotbe furtherdegraded. When these techniques cannot be accomplished or aretoo risky and expensive, immobilizationordinary Portlandcement (OPC), water glass (sodium silicate), gypsum or organicpolymers, for example acrylic or epoxy resins, covering withbentonite or polymeric membrane are the available options toensure the isolation of the polluted site to reduce the waterinfiltration and the possible mobilization and migration ofthe elements.In this brief review, it is complicated toclearly distinguish the methods according to the contaminatedmatrix (being a phenomenon often multi-matrix&multi-pollutant)and to the possibility of realizing them close to the site orfar away in centralized systems.Therefore, thetreatment arepresented in relation to the technological nature of theprocess (physical-chemical, thermic and biological), as listedin Table 1.

Table 1 – Remediation Processes

Due to the recalcitrant nature or the toxicity of the mainpollutants,incompatible with biological systems, it isnecessary to implement chemical methods to neutralize thesesubstances: to convert into less harmful forms, less mobile,more stable and inert) the substances.Injection of chemicalreductants, including calcium polysulphide, has been used topromote contaminant reduction and precipitation withinaquifers. TheIn-situ Oxidation consists in injecting oxidantssuch as hydrogen peroxide (H2O2) into the contaminated aquifer.

Figure 2 – In Situ Oxidation of polluted groundwater

Contaminants that are well suited to remediation using thisapproach include metals with a lower solubility under reducedconditions (e.g. Cr (VI), through reduction to Cr(III) andprecipitation of Cr(III) hydroxides). Advanced oxidationprocesses releasinghydroxyl radicals are the most affordabletechniques to degrade organic recalcitrant pollutants. Theseinclude the use of H2O2, UV, O3, “Fenton reactants”, etc.

Figure 3 – OH attack to the aromatic ring.

The physical treatments mainly consist in the separation ofthe pollutant.Alternatively, it is possible to isolate highlyconcentrated matrix to be eventually treated or sent to thefinal disposal. This solution avoids the addition of chemicalreagents (and secondary pollutant formation) but shouldinclude costs for gas treating and for landfilling, especiallyfor special waste.The air sparging is successfully applicableto volatile compounds (hydrocarbons and chlorinatedsolvents).Physical and geotechnicalcharacteristic of the soilas well as chemical properties of the pollutant arefundamental in the process analysis. The aquifercharacteristic, if present, also influences the process.Natural zeolite has been studied extensively for remediationof heavy metal-polluted soils due to its wide availability andlow cost.

The Pump-and-treatinvolves removing contaminated groundwaterfrom strategically placed wells, treating the extracted waterafter it is on the surface to remove the contaminates usingmechanical, chemical, or biological methods, and dischargingthe treated water to the subsurface, surface, or municipalsewer system. Water from the aquifer is pumped through thewells and piped to the pump-and-treat facilities, wherecontaminants are removed through an ion exchange that relieson tiny resin beads, resembling cornmeal, packed into largetanks or columns. As the water travels through the columns,hexavalent chromium ions cling to the resin beads and areremoved from the water.[4]

Depending on the type of the reactive material andcontaminants, the degradation may be complete ormay producesintermediates with different toxicity by the initialcompounds.Therefore, very often the use of chemical-physicalcombined techniques (e.g. soil washing)could exploit the

advantages of both.

While pump and treat of groundwater mainly include ex-situtreatments, Permeable Reactive Barriers (PRBs)can be used forthe in-situ treatment of the waterscontaminated ground. Asvisible in Figure 4, a PRB consists of a continuous treatmentzone, in its usual configuration, formed by the reactivematerial, installed in the subsoil in order to intercept thecontaminated plume and induce the degradation of thecontaminants from the mobile liquid phase.This technology isenergy-saving since a reactive mediumwith a permeability

higher than that of the surrounding soil has to be used[5],[6].In this way, remediation occurs under the natural gradient ofthe aquifer, without additional energy contribution except thegroundwater hydraulic head.PRBs are defined PermeableAdsorptive Barrier (PABs) when adsorbing material is used asreactive one and contaminant removal is carriedout byadsorption6. Recently, academic research is focusing on theinvestigation of innovative configurations, such asDiscontinuous Permeable Adsorptive Barriers[7], which isarranged as a passive well array with one or more lines at afixed distance one another and filled with adsorbing materials(Figure 5). Comparing Continuous and Discontinuous AdsorptiveBarrier configurations it can be found that thedecontamination of the same volume of groundwater can becarried out by reducing the amount of the barrier volume, andconsequently by reducing remediation cost,if a Discontinuousbarrier is used, highlighting the technology and cost-savinginnovation of this advanced configuration[8].

Figure 4 – Schematic of aContinuous PRB

Figure 5 – Schematic of aDiscontinuous PAB7

The biological remediation methods (BioSparging, Landfarming)are available for high permeable and homogeneous soils for themineralization or conversion of organic contaminants (SVE, BV,

BTEX, light hydrocarbons, non-chlorinated phenols) into lesstoxic forms, or more toxic but less bioavailable. This processprimarily exploit the ability of microorganisms transform thepolluting material part in the biomass and partly into lesscomplex molecules (eventually to minerals, carbon dioxide andwater). These processes have been tried to remove heavy metalsfrom soil as well, using biological leaching (bioleaching) orredox reactions.These methods are also non-invasive and canbring potential beneficial effect on the structure andfertility of the soil.In addition to microorganisms, plantscan accumulate and degrade the contaminants in the so-calledphytoremediation process. This recovery method, calledphytoremediation, takes advantage of the complex interactionbetween root system of plants, microorganisms and soil, andrepresent the most sustainable solution in this sector. Areview is given by Puldorf and Watson[9].A typical plant mayaccumulate about 100 parts per million (ppm) zinc and 1 ppmcadmium. Thlaspi caerulescens (alpine pennycress, a small,weedy member of the broccoli and cabbage family) canaccumulate up to 30,000 ppm zinc and 1,500 ppm cadmium in itsshoots, while exhibiting few or no toxicity symptoms. A normalplant can be poisoned with as little as 1,000 ppm of zinc or20 to 50 ppm of cadmium in its shoots[10]. Phytoremediationhas also been studied for degrading PCBs and PCDD/Fs [11].Somedisposal methods for phytoremediation crops were proposed bySas-Nowosielska et al.[12].The most beneficiary is to usephytoextraction crops for energy production hence pyrolysis,gasification or combustion. The fate of trace elements duringcombustion, pyrolysis, fluidized bed and downdraftgasification were studied in the recent scientificliterature[13].

TheThermal methodscan induce the separation of the pollutantmeansdesorption / volatilization and its destruction orimmobilization by fusion of the solid matrix. In thedesorption of pollutants from contaminated soil, a majorresearch effort has been initiated to characterize the rate-

controlling processes associated with the evolution ofhazardous materials from soils[14]. The P.O.N. ResearchProject DI.MO.D.I.[15] was focused on the treatment of soilscontaminated by hydrocarbons by an innovative device thatcould represent the solution to many logistical problems thatmake difficult the “on-site” treatment. The device (sketchedin Figure 6) developed consists ina mobile unit, installed ontruck, completely self-sufficient, able to permit emergencysafety and remediation in reasonable short times and low costactions. The treatment unit utilizes a dual fluidized bedreactortechnology fed by the hot gas produced by a hot gasgenerator. The upper bed is aimed at soil drying while thelower bed is aimed at soil remediation by thermal desorption.The processes of soil draying anddesorption of volatile andsemi-volatile organic contaminantsoccur by the direct contactair/solid particles promoted by the fluidization technology.The soil requires a pre-treatment based onshredding/pulverizing and dimension separation, in order tofeed the soil with the optimal size for fluidization. Particleremoval from desorption gaseous flow stream is carried out bydust separator units (fabric filter and cyclone).

Figure 6 – Schematization of the DI.MO.D.I.treatment unit

Figure 7 – DI.M.O.D.I.treatment unit

[1]http://www.scientificamerican.com/article/10-most-polluted-places-in-the-world1/

W.W. Kovalick, Jr. Robert H. Montgomery.. Developing a ProgramforContaminated Site Management inLow and MiddleIncomeCountries The World Bank

Ahmad I., Hayat S. and Pichtel J.(2005). Heavy MetalContamination of Soil: Problems and Remedies.SciencePublishers, Inc. Enfield, NH, USA

Van Lynden, G.W.J. (1995). European soil resources. Currentstatus of soil degradation, causes, impacts and need foraction. Council of Europe Press. Nature and Environment, No71, Strasbourg, France.

[2]http://energy.gov/em/services/site-facility-restoration/soil-groundwater-remediation

[3]EPA Guidelines for Environmental management of on-siteremediation

[4]http://energy.gov/em/articles/pump-and-treat-systems-prove-effective-deliver-cost-savings-groundwater-cleanup

[5]U.S. EPA, 1999. Field Applications of In Situ RemediationTechnologies: Permeable Reactive Barriers, EPA, 542-R-99-002.

[6]Erto, A., Lancia A., Bortone I., Di Nardo A., Di Natale,M., Musmarra D., 2011. A procedure to design a PermeableAdsorptive Barrier (PAB) for contaminated groundwaterremediation. Journal of Environmental Management, 92, 23-30.

[7] Bortone, I., Di Nardo, A., Di Natale, M., Erto, A.,Musmarra, D., Santonastaso, G.F., 2013. Remediation of anaquifer polluted with dissolved tetrachloroethylene by anarray of wells filled with activated carbon. Journal ofHazardous Materials, 260, 914–920.

[8] Santonastaso, G. F., Bortone, I., Chianese, S., Erto, A.,Di Nardo, A., Di Natale, M., Musmarra, D., 2015. Applicationof a discontinuous permeable adsorptive barrier for aquiferremediation. A comparison with a continuous adsorptivebarrier. Desalination and Water Treatment, doi:10.1080/19443994.2015.1130921.

[9] Review article Phytoremediation of heavy metal-contaminated land by trees—a review I.D. Pulford*, C. Watson.Environment International 29 (2003) 529 – 540

[10]From US Department of Agriculture Phytoremediation: UsingPlants To Clean Up Soils

[11] Campanella, Bock, C., Schroder, P., Phytoremediation:PCBs And PCDD/Fs Environmental Science and Pollution ResearchJanuary 2002, Vol 9, Issue 1, pp 73-85

[12] A Sas-Nowosielska et al., Environmental PollutionVol.

128, Issue 3, 2004, 373-379.

[13] M. Šyc, M. Pohořelý, M. Jeremiáš, M. Vosecký, P.Kameníková, S. Skoblia, K. Svoboda and M. Punčochář. Behaviorof Heavy Metals in Steam Fluidized Bed Gasification ofContaminated Biomass. Energy Fuels, 2011, 25 (5), 2284–2291.M.Šyc et al., Willow trees from heavy metals phytoextraction asenergy crops. Biomass and BioenergyVol. 37, 2012, 106–113. P.Vervaeke et al., Fate of heavy metals during fixed beddowndraft gasification of willow wood harvested fromcontaminated sites. Biomass and Bioenergy. Volume 30, Issue 1,2006, 58–65.

[14] JoAnn S. Lighty,” Geoffrey D. Silcox, and David W.Pershing. Vic A. Cundy David G. Linz Fundamentals for theThermal Remediation of Contaminated Soils. Particle and BedDesorption Models Environ. Sci. Technol. 1990, 24, 750-757.Marline T. Smith, M.T., Franco Berruti,and Anil K. Mehrotra.Thermal Desorption Treatment of Contaminated Soils in aNovelBatch Thermal Reactor Ind. Eng. Chem.Res.2001,40,5421-5430.

[15] Piano Operativo Nazionale Ricerca e Competitività2007-2013, PON01_00599 “Dispositivo Mobile per DesorbimentoIdrocarburi (DI.MO.D.I.)” – Consortium leader: SecondUniversity of Naples (Scientific Coordinator and PrincipalInvestigator: Prof. Dino Musmarra)

Current Situation of EmergingTechnologies for UpgradingHeavy OilsAuthor: Marcello De Falco, Associate Professor, UniversityUCBM – Rome (Italy)

1.Theme descriptionThe change in the average crude oil quality due to thescarcity of light oil reserves and to the increase of the useof shale oil, oil sand and bitumen is causing significanttroubles to refineries, which are obliged to accept heavierfeeds with very different physical properties (lower APIgravity, higher amount of impurities). This has stimulated thedevelopment of new technology for upgrading the heavy andextra-heavy oils in order to improve their characteristicsand, consequently, the refineries performance.

Heavy oils are classified as oil with a API gravity within therange 10°- 22°, whereas extra-heavy oils have a API gravity <10°. Heavy oils and bitumen reserves geographical distributionis reported in Table 1 [1]: these reserves are continuouslyincreasing, replacing the light oil ones, and Oil&Gascompanies found and developed competitive solutions to extractand treat these oils.

Table 1 – Geographical distribution of heavy oil and bitumenreserves.

Clearly, there is the need to upgrade the heavy oils beforefeeding to the refineries, in order to improve the downstreamproducts quality and to increase the topping distillate flows:the conventional upgrading processes include carbon rejectionand hydrogen addition technologies. But, when the propertiesof the heavy and extra-heavy oils are critical, more effective

solutions are needed to make the oil suitable for refineriesfeedstock. For this reason, researchers and industries areproposing a number of innovative solutions and some of themare already in the full-scale demonstration phase.

In the following, some of these new emerging oil upgradingconfiguration are presented. For a complete list of developedtechnologies, the author suggests the Castaneda, Munoz andAncheyta review paper[2], which includes the description andcomparison of 23 new processes.

2.Heavy-to-Light heavy oilupgrading processThe Heavy-to-Light (HTL) process is patented by IvanhoeEnergy[3], a company recently acquired by FluidOil[4].

The process is based on a circulating transport bed of hotsand to heat the heavy feedstock and convert them to lighterproducts. Then the upgraded products and the sand areseparated in a cyclone and the products are quenched androuted to the atmospheric distillation unit.

The main benefits of the HTL configuration are that it can beintegrated at the well-head and it is simple and cheap. Thedrawbacks are the large dimension of the equipment, the lowvolumetric yield of upgraded crude, the low capacity forextra-heavy oil processing, the high formation of coke and alow sulfur content reduction. At the exit of the upgradingplant, the oil reaches a API gravity of 18-19° and a 100°Ckinematic viscosity of 23 cSt.

The technology development has been completed and IvanhoeEnergy is designing industrial plants in Canada, Latin Americaand the Middle East.

Figure 1 – Ivanhoe Energy’s HTL test facility in San Antonio,Texas[5].

3.HCAT processHCAT is a catalytic heavy oil upgrading technology developedby Headwaters Technology Innovations Group (HTIG)[6]. Theprocess is composed by a catalytic reactor where a moleculesized catalyst is packed, assuring high conversion of theheavy oil. The main benefits of HCAT configuration areconstant product quality, feedstock flexibility and flexibleand high conversion (up to 95%).

Neste Oil Corporation’s Porvoo Refinery at South Jordan, Utah,is the first refinery which implements, in 2011, the HCATheavy oil upgrading technology[7]. More than 500.000 barrelsof heavy oil are processed in their upgrading reactors everyday and a refinery additional capacity of 200.000 barrels perday has been reached.

4.Viscositor processViscositor technology is patented by the Norwegian companyEllycrack AS[8] and it is based on the atomization of theheavy oil by means of a heated sand in a high-velocitychamber. Basically, the process is composed by the followingsteps (refer to the block diagram shown in Figure 2):

sand particles, heated up by coke combustion, arepneumatically conveyed into a collision reactor by meansof the hot combustion gases;pre-heated heavy oil is fed to the reactor and collidewith the sand particles, evaporating and cracking;the solid particles, the coke generated during thecollision process and the oil stream are separated in acyclone. The solid phase is sent to a regenerator whilethe oil stream is fed to a dual condensation system. Thegenerated coke is used to supply the heat duty.

The advantages of the process are the low temperature and thelow pressure required, almost self-sustained thanks to thecoke formation in the reactor and the good quality of thefinal upgraded oil.

Figure 2 – Block diagram of the Viscositor process

5.IMP processIMP configuration[9] is a catalytic hydrotreatment-hydrocracking process of heavy oil at mild operatingconditions, able to achieve high removal of metals, sulfurcompounds, asphaltenes and a large conversion of the heaviershare of the oil stream to more valuable distillates.

The most important characteristic of the IMP process is thelow fixed investment required and the low operating costs,with an attractive return of investment.

The IMP technology can be applied both for conversion of heavyand extra-heavy oils to intermediate oils and as a firstprocessing unit for heavy and extra-heavy crude oils in arefinery. The final properties of upgraded oils, depending onthe heavy oil feedstock, are: API gravity = 22-25°; sulfurcontent = 1.1 – 1.15 wt%; C7 asphaltenes = 4.7 – 5.3.

A first industrial unit application is being analyzed byPetroleos Mexicanos (PEMEX).

6.Nex-Gen Ultrasound technologyNex-Gen is an innovative process for heavy oil upgrading whichuses ultrasonic waves to break the long hydrocarbon chains andsimultaneously adds a hydrogen stream.

Basically, Nex-Gen is a cavitation process: the ultrasonicenergy forms cavitation bubbles in the heavy oil stream; then,the bubbles tends to collapse at high temperature andpressure, causing the breaking of the long chain of heavyhydrocarbon molecules.

The next figure shows a scheme of the Nex-Gen configuration.

Figure 3 – Scheme of NexGen architecture[10].

A first industrial plant is going to be designed to beintegrated near the Athabasca tar sands (Edmonton, Alberta),with a capacity of 10.000 barrels per day. The mild operatingconditions (temperature = 0 – 70°C, pressure = 1 – 5 bar)allows a reduction of energy consumption and operating andmaintenance costs by 50%.

7.Chattanooga processChattanooga process is a continuous process based on a

fluidized bed reactor operating at high pressure andtemperature in a hydrogen environment.

The main equipment of the configuration is the pressurizedfluid bed reactor and associated fired hydrogen heater. Thereactor can continuously convert oil by thermal cracking andhydrogenation into hydrocarbon vapors while removing spentsolids[11].

The energy requirements associated with the Chattanoogaconfiguration are significantly reduced in respect to thetraditional heavy oil upgrading technologies, as well asoperating costs and capital costs.

Figure 4 – Chattanooga technology description11.

[1]http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322014000300001

[2]http://www.sciencedirect.com/science/article/pii/S0920586113002691

[3] Patent No. US 8,105,482 B1 (January 2012).

[4]http://www.marketwired.com/press-release/fluidoil-completes-acquisition-of-ivanhoe-energy-2111300.htm

[5] http://www.albertaoilmagazine.com/2014/04/beyond-diluent/

[6] Patent No. US 7,578,928 B2 (August 2009),

[7]http://www.greencarcongress.com/2011/01/neste-oil-implementing-headwaters-hcat-heavy-oil-upgrading-technology-at-porvoo-refinery.html

[8] Patent No. US 6,660,158 (December 2003).

[9] Patent No. US 7,651,604 B2 (January 26, 2010).

[10] http://www.pedcous.com/business technologyupgrading.html, Heavy to light upgrading project,Revolutionary upgrading technology converting extremely heavycrude oil to light sweet crude oil.

[11]http://www.chattanoogaprocess.com/documents/Chattanooga_Proces

s.pdf

Sealing Materials for WellIntegrityAuthor: Marcello De Falco, Associate Professor, UniversityUCBM – Rome (Italy)

1.Theme description

Well integrity is defined in the NORSOK D-010[1] (a functionalstandard which fixes minimum requirements for equipments ofthe oil and gas production wells) as “application oftechnical, operational and organizational solutions to reducerisk of uncontrolled release of formation fluids throughoutthe life cycle of a well“.

Basically, technologies for well integrity include manyaspects about well operating processes, well services, tubingand wellhead integrity, safety system testing, etc..

Clearly, production tubes have the greatest probability offailure since they are exposed to corrosive elements from theproduced fluids. Moreover, the production tubing consists ofmany connections, which are points of weakness with high riskof leak. International standards impose the installation oftwo well barriers between the reservoirs and the environmentin order to prevent the loss of containment.

In this paper, among the components of the production tubesealing system installed to avoid fluid losses, the innovativesealing materials are assessed and compared.

The most common used sealing material is the cement, which isa fully known and cheap materials. But, there are manyproperties not ideal for handling well integrity issue as, forexample, gas migration through its structure, long termdegradation due to temperature and chemical substancesexposure, shrinking, etc.

The following figure shows the main problem in applying cementas sealing material in well casing[2].

Figure 1 – Cement technical drawbacks in sealing application2:a), b), f) leak paths due to poor bonding between cement and

casing/formation; c) fluids migration due to cement

fracturing; d) leakages occurring for casing failure; e) flowpath through the cement layer due to gas migration during

hardening.

For this reason, alternative materials for sealing are studiedin order to overcome the issues related to the cementapplication.

Such materials have to assure a series of properties, amongwhich:

low permeability;capacity of bonding to the casing and to the borehole;pumpable without excessive costs;chemically inert and not-reactive with chemicalsubstances present in the formation;self-levelling in the well;safe to be handled and cheap.

An exhaustive list of the most interesting alternative

materials is reported in 2. In the following, the mostinteresting ones (ThermaSet, Sandaband and Ultra Seal) arepresented and described.

2.ThermaSet

ThermasetR is a polymeric based resin used to solve a series ofwell integrity issues, as lost circulation, compromisedwellbore integrity, plug and abandonment, and the remediation

of sustained casing pressure[3],[4].

As a liquid, ThermaSet is easily pumped and injected since itnot contains solid particles. However, particles can be added

to accurately modulate the liquid density.

Compared to cement, ThermaSet has a higher compressive andtensile strength, thus improving the sealing materialmechanical properties and its behavior under the variableloads which could be caused by pressure and temperature cyclesthat cause the casing to expand and contract, exerting a forceon the annulus material.

In the following table, the ThermaSet and a typical cement

(class G Portland) properties are compared[5],[6], attesting theimproved characteristics of the innovative material.

Table 1 – Mechanical properties comparison between ThermaSetand Portland cement.

The excellent properties of the material are maintained overtime, without showing significant decays: Figure 2 shows thecompressive strength value after 1 year under a crude oilpressure equal to 500 bar, demonstrating that its value

stabilizes at a value within the range 40-45 MPa6.

Figure 2 – ThermaSet compressive strength evolution over timeafter long-term exposure to crude oil at 500 bar.

Moreover, various experimental tests demonstrated thatThermaSet has, also for long-term test, a low permeability[7].

3.SandabandSandaband is a patented material[8], owned by Sandaband WellPlugging (SWP), consisting of 70% to 80% quartz solids with avariable grain size diameter (between 1 µm and 2 mm)[9]. Therest of the volume is composed by water and chemicals thatmake the material easily pumpable.

All materials composing Sandaband are chemically stable, withno degradation over time or reaction with other chemicals.

An important property is that Sandaband behaves like a Binghamplastic material, characterized by the fact that it needs ashear stress to start flowing and then has a linear dependencebetween shear stress and strain, thus allowing that thematerials quickly form a rigid body as the pumping is stopped

(refer to Figure 3).

Figure 3 – Bingham liquid behaviour compared to a Newtonianfluid.

Sandaband has a series of unparalleled properties, making itexcellent for the application of sealing material for wellintegrity[10]:

Long term integrityBonds to steelRemovableDuctileNon shrinkingCost effectiveChemically inertGas-tightPumpableEnvironmentally safeNo health hazardsVerifiableHPHT resistantNo reservoir damage

Non-erosional

Tests demonstrated the long-term integrity in the temperaturerange -10°C to 250°C, the low permeability under operatingconditions, the absence of effects on the gas- tightness forcasing moving and vibration.

Figure 4 – Sandaband handling.

The innovative materials has been tested on field for aTemporary P&A (Plug and Abandonment) (BP Norway Ula Well 2007)and for a Permanent P&A (Det Norske Oljeselskap).

4.Ultra SealUltra Seal, developed by CSI Technologies[11], is a materialcomposed by a resin and a hardener, modulated to make thesealant pumpable. Resin and hardener are mixed on the surfacein a conventional mixing equipment and clean-up is with aminimal quantity of a methanol and water mixture.

Ultra-Seal R is liquid, thus permitting a more precise mixingthan Portland cement.

The material is characterized by low permeability andexcellent mechanical properties.

Figure 5 – Ultra Seal

[1]https://www.standard.no/en/sectors/energi-og-klima/petroleum/norsok-standard-categories/d-drilling/d-0104/

[2] Dickson Udofia Etetim, ” Well Integrity behind casingduring well operation.Alternative sealing materials tocement”, Norwegian University of Science and Technology,Department of Petroleum Engineering and Applied Geophysics

[3] http://www.wellcem.no/thermaset-sup-sup-

[4] http://www.wellcem.no/diverse/Brochure.pdf

[5] Wellcem AS. ThermaSet Test Report, 2001.

[6]https://www.norskoljeoggass.no/Global/Presentasjoner/PAF%20Wor

kshop/9%20-%20WellCem%20%20-%20Colin%20Beharie.pdf

[7]http://www.diva-portal.org/smash/get/diva2:565974/FULLTEXT01.pdf

[8] U. .S Patent # 6,715,543; U.S. Patent # 7,258,174

[9]http://www.sandaband.com/modules/m02/article.aspx?CatId=56&ArtId=6

[10]http://www.norskoljeoggass.no/PageFiles/10706/7%20Sandaband%20-%20Non%20consolidating%20plugging%20material.pdf

[11]http://csi-tech.net/documents/csi-resin-sealant.pdf#search=”Ultra Seal”

Solar RefineryAuthor: Vincenzo Piemonte, Associate Professor, University UCBM – Rome (Italy)

1.Theme description

The purpose of a solar refinery is to enable an energytransition from today’s ‘fossil fuel economy’ with itsassociated risks of climate change caused by CO2 emissions, toa new and sustainable ‘carbon dioxide economy’ that insteaduses the CO2 as a C1 feedstock, together with H2O and sunlight,

for making solar fuels.

Figure 1 – Scheme of a ‘solar refinery’ for making fuels andchemicals from CO2, H2O and sunlight[1]

On an industrial scale, one can visualize a solar refinery(see Figure 1) that converts readily available sources ofcarbon and hydrogen, in the form of CO2 and water, to usefulfuels, such as methanol, using energy sourced from a solarutility. The solar utility, optimized to collect andconcentrate solar energy and/or convert solar energy toelectricity or heat, can be used to drive theelectrocatalytic, photoelectrochemical (PEC), orthermochemical reactions needed for conversion processes. Forexample, electricity provided by PV cells can be used togenerate hydrogen electrochemically from water via anelectrocatalytic cell.

However, hydrogen lacks volumetric energy density and cannotbe easily stored and distributed like hydrocarbon fuels.Therefore, rather than utilizing solar-generated hydrogendirectly and primarily as a fuel, its utility is much greaterat least in the short to intermediate term as an onsite fuelfor converting CO2 to CH4 or for generating syngas, heat, orelectricity. Reacting CO2 with hydrogen not only provides aneffective means for storing CO2 (in methane, for example), italso produces a fuel that is much easier to store, distribute,and utilize within the existing energy supply infrastructure.

The idea of converting CO2 to useful hydrocarbon fuels byharnessing solar energy is attractive in concept. However,significant reductions in CO2 capture costs and significantimprovements in the efficiency with which solar energy is usedto drive chemical conversions must be achieved to make thesolar refinery a reality.

Figure 2 – Schematic diagram of integrated PV-Hydrogen utilityenergy system

Solar energy collected and concentrated within a solar utility

can be harnessed in different ways: (1) PV systems couldconvert sunlight into electricity, which in turn, could beused to drive electrochemical cells that decompose inertchemical species such as H2O or CO2 into useful fuels (seefigure 2); (2) PEC or photocatalytic systems could be designedwherein electrochemical decomposition reactions are drivendirectly by light, without the need to separately generateelectricity; and (3) photothermal systems could be used eitherto heat working fluids or help drive desired chemicalreactions such as those connected with thermolysis,thermochemical cycles, etc. (see Figure 3). Each of theseapproaches can be used to generate environmentally friendlysolar fuels that offer “efficient production, sufficientenergy density, and flexible conversion into heat, electrical,or mechanical energy”[2]. The energy stored in the chemicalbonds of a solar fuel could be released via reaction with anoxidizer, typically air, either electrochemically (e.g., infuel cells) or by combustion, as is usually the case withfossil fuels. Of the three approaches listed here, only thefirst (PV and electrolysis cells) can rely on infrastructurethat is already installed today at a scale that would have thepotential to significantly affect current energy needs. Infact, the PEC and photothermal approaches, though they holdpromise for achieving simplified assembly and/or high energyconversion efficiencies, require considerable developmentbefore moving from the laboratory into pilot-scale andcommercially viable assemblies.

Figure 3 – Solar-Driven, Two-Step Water Splitting to FormHydrogen Based on Reduction/Oxidation Reactions

2.Carbon Dioxide-derived fuelsThe CO2 concentrations in the atmosphere are still low enough(0.04%) that it would be impractically expensive to captureand purify CO2 from the atmosphere, but other sources of CO2

are available that are considerably more concentrated. Powergeneration based on natural gas or coal combustion isresponsible for the major fraction of global CO2 emissions,with other important sources being represented by the cement,metals, oil refinery, and petrochemical industries[3]. Indeed,a growing number of large-scale power plant carbon dioxidecapture and storage (CSS) projects are either operating, underconstruction, or in the planning stage, some of them involvingfacilities as large as 1,200 MW capacity[4]. While solar PV

energy conversion has the potential to reduce CO2 emissions byserving as an alternative means of generating electricity,harnessing solar energy to convert the CO2 generated by othersources into useful fuels and chemicals that can be readilyintegrated into existing storage and distribution systemswould move us considerably closer to achieving a carbon-neutral energy environment.

Herron et al.[5], in a very recent review, examine the mainroutes for CO2 capture from stationary sources with high CO2

concentrations derived from post-combustion, precombustion,and oxy-combustion processes.

In post-combustion, flue gases formed by combustion of fossilfuels in air lead to gas streams with 3%–20% CO2 in nitrogen,oxygen, and water. Other processes that produce even higher CO2

concentrations include pre-combustion in which CO2 is generatedat concentrations of 15%–40% at elevated pressure (15–40 bar)during H2 enrichment of syngas via a water–gas shift reaction(WGS — see Figure 1) and oxy-combustion in which fuel iscombusted in a mixture of O2 and CO2 rather than air, leadingto a product with 75%–80% CO2. CO2 capture can be achieved byabsorption using liquid solvents (wet-scrubbing) or solidadsorbents.

In the former approach, physical solvents (e.g., methanol) arepreferred for concentrated CO2 streams with high CO2 partialpressures, while chemical solvents (e.g., monoethanolamine -MEA) are useful in low-pressure streams.

Energy costs for MEA wet-scrubbing are reportedly as low as0.37–0.51 MWh/ton CO2 with a loading capacity of 0.40 kg CO2per kg MEA. Disadvantages of this process are the high energycost for regenerating solvent, the cost to compress capturedCO2 for transport and storage, and the low degradationtemperature of MEA. Alternatives include membrane and

cryogenic separation. With membranes there is an inversecorrelation between selectivity and permeability, so one mustoptimize between purity and separation rate.

Cryogenic separation ensures high purity at the expense of lowyield and higher cost. Currently, MEA absorption isindustrially practiced, but is limited in scale: 320–800metric tons CO2/day (versus a CO2 generation rate of 12,000metric tons per day for a 500 MW power plant). Scale-up wouldbe required to satisfy the needs of a solar refinery.

Alternatives, such as membranes, have relatively low capitalcosts, but require high partial pressures of CO2 and a costlycompression step to achieve high selectivity and rates ofseparation.

A very important point to consider about solar refineryreliability is that since carbon capture reduces theefficiency of power generation, power plants with carboncapture will produce more CO2 emissions (per MWh) than a powerplant that does not capture CO2. Therefore, the cost oftransportation fuel produced with the aid of CO2 capture mustalso cover the incremental cost of the extra CO2 capture[6].These costs must then be compared to the alternative costsassociated with large-scale CO2 sequestration. Finally, onealso needs to consider the longer-term rationale forconverting CO2 to liquid fuels once fossil-fuel power plantscease to be major sources of CO2. Closed-cycle fuel combustionand capture of CO2 from, e.g., vehicle tailpipes, presents aconsiderably greater technical and cost challenge than capturefrom concentrated stationary sources.

3.Challenges & OpportunitiesChristos Maravelias and colleagues from the University ofWisconsin have recently modeled and analyzed the energy andeconomic cost of every step and each alternative technologycontained in a solar refinery[7]. The result is a generalframework that will allow scientists and engineers to evaluatehow various improvements in materials’ manufacturing andprocessing technologies that enable carbon dioxide capture andconversion to fuels using solar, thermal and electrical energyinputs would accelerate the development, influence the costand impact the vision of the solar refinery. It will alsoenable evaluation of which alternative technologies are themost economically feasible and should be targeted or highlightthose that even if developed would still be hopelesslyuneconomic and can therefore be ruled out immediately.

The view that emerges from this techno-economic evaluation ofbuilding and operating a solar refinery is one of guardedoptimism. On the subject of energy efficiency, it is clearthat solar powered CO2 reduction is currently lagging farbehind that of solar driven H2O splitting and more research isneeded to improve the activity of photocatalysts and theefficacy of photoreactors. In the indirect process oftransforming CO2/H2O to fuels, it is apparent that if thecurrently achievable solar H2O-to-H2 conversion (>10%) can bematched by solar CO2/H2-to-fuel conversion efficiencies,through creative catalyst design and reactor engineering, thiswould represent a promising step towards an energeticallyviable solar refinery. For the process that can directlytransform CO2/H2O to fuels, improvements in conversion ratesand product selectivity are key requirements for achievingenergy efficiency in the solar refinery.

Economic efficiency is also a key to the success of the solarrefinery of the future. For currently achievable CO2 reduction

rates and efficiencies, the minimum selling price of methanol,a representative fuel, was evaluated by the techno-economicanalysis and turned out to be more than three times greaterthan the industrial selling price analysis, even though thecost of the CO2 reduction step, which is estimated to be quitecostly, was not included in the estimates. Improvement in theactivity of CO2 reduction photocatalysts by several orders ofmagnitude would have a significant impact on the energy andeconomic costs of operating a solar refinery.

It is clear that the cost and energy efficiency of carboncapture and storage is an area where big improvements need tobe made if the solar refinery is to be a success. One otherpoint that is worth highlighting is the availability of water,since in some parts of the world the availability of watercould be a big problem to face up.

To conclude, multidisciplinary teams of materials chemists,materials scientists, and materials engineers across the globebelieve in the dream of the solar refinery and a sustainableCO2 based economy. Anyway it is clear that developing models toevaluate the energy efficiency and economic feasibility of thesolar refinery, and at the same time identifying hurdles whichhave to be surmounted in order to realize the competitiveprocessing of solar fuels, will continue to play a crucialrole in the development of the required technologies.

[1] Reproduced from A general framework for the assessment ofsolar fuel technologies, Energy & Environmental Science, DOI:10.1039/C4EE01958J with permission of The Royal Society of

Chemistry.

[2] Jooss, C. and H. Tributch. “Chapter 47: Solar Fuels”Fundamentals of Materials for Energy and Environmental

Sustainability. D.S. Ginley and D. Cahen, editors. CambridgeUniversity Press. (2011). http://cds.cern.ch/

record/1613941

[3] Carbon Dioxide Emissions. United States EnvironmentalProtection Agency. http://www.epa.gov/climatechange/

ghgemissions/gases/co2.html

[4]http://www.globalccsinstitute.com/projects/large-scale-ccs-projects

[5] Herron, J.A., J. Kim, A.A. Upadhye, G.W. Huber, C.T.Maravelias. “A General Framework for the Assessment of SolarFuel Technologies.” Energy Environ. Sci. (2015). 8, 126-157.

[6] Randall Field, MIT Energy Initiative, personalcommunications.

[7] Energy and Environmental Science, 2014, DOI:10.1039/c4ee01958j

Water Treatment inUnconventional Gas ProductionAuthor: Vincenzo Piemonte, Associate Professor, UniversityUCBM – Rome (Italy)

1.Theme description The average $3 million drilling and fracturing processrequired for each well uses an average of 4.2 million gallonsof water, much of which has traditionally been freshwater. Thevolume of water can vary significantly and is highly dependenton the length of the drilled lateral[1].

More than 99 percent of the fracturing fluid is water andsand, while other components such as lubricants andbactericides constitute the remaining 0.5 percent. Thisfracturing mixture enters the well bore, and some of itreturns as flowback or produced water, carrying with it, inaddition to the original materials, dissolved and suspendedminerals and other materials that it picks up in the shale[2].

Figure 1 – Volumetric composition of process water in shalegas production.

Once in production for several years, natural gas wells canfeasibly undergo additional hydraulic fracturing to stimulatefurther production, thereby increasing the volume of waterneeded for each well. Approximately 10-25 percent of the water

injected into the well is recovered within three to four weeksafter drilling and fracturing a well. Water that is recoveredduring the drilling process (drilling water), returned to thesurface after hydraulic fracturing (flowback water), orstripped from the gas during the production phase of well

operation (produced water) must be properly disposed2.

The recovered water contains numerous pollutants such asbarium, strontium, oil and grease, soluble organics, and ahigh concentration of chlorides. The contents of the water canvary depending on geological conditions and the types ofchemicals used in the injected fracturing fluid. Thesewastewaters are not well suited for disposal in standardsewage treatment plants, as recovered waters can adverselyaffect the biological processes of the treatment plant(impacting the bacteria critical to digestion) and leavechemical residues in the sewage sludge and the dischargewater. Many producers have been transporting flowback andproduced water long distances to acceptable water treatmentfacilities or injection sites. But deep well injection nowalso meeting challenges.

The water disposal challenge has spurred a new water treatmentindustry in the region, with entrepreneurs and establishedcompanies creating portable treatment plants and otherinnovative treatment technologies to help manage producedwater mainly focuses to water reuse.

Figure 2 – Potential beneficial reuses of process water in theoil&gas industry.

2.Water Costs and Quality ConcernsDealing with water scarcity and wastewater (i.e., brine)quality are top priorities in shale and tight gas production.Doing this requires water reuse technology that reduces thewaste stream by efficiently separating out salts, heavy metalsand nutrients to produce recovered water. Effective filtrationmust eliminate suspended solids from salt water going to deepwell injection.

Cost can be an overriding factor in water treatment andprocessing decisions. There certainly are environmentalconsiderations involved in using chemicals to performoperations such as frac- water treatment or salt removal andrecovery. However, the cost of mitigating chemistry also comesinto play. Chemical friction reducers make source water

slicker for faster pumping, and then specialty chemicals likebiocides, which kill microorganisms, and scale inhibitors,which control deposits, are added to the water. Mobileultrafiltration technology can reduce the need for biocides –and the cost of treatment.

Slick water fracturing and horizontal drilling wererevolutionary developments that made it economically viable toextract unconventional gas on a grand scale. Fracturinglowered the cost of moving the gas to the well bore, whilehorizontal drilling – which covered a vastly greater expanseof territory than a single vertical probe – exponentiallyincreased the amount of gas that could be withdrawn. It becamemuch more profitable to put wells into shale gas formations,but the cost of doing that business today depends, in no smallpart, on what ultimately happens to the brine. That, in turn,depends on geography. Chemical treatment is not the challengeso much as affordability; most brine is just discharged todisposal wells, but the fewer of these wells there are, thegreater the production expense incurred, and in some parts ofthe country, geology or the lack of water makes disposal wellsunfeasible.

In geographical areas, like Pennsylvania where there are majorshale gas deposits, where the geology won’t allow disposalwells, the brine has to be trucked out for disposal elsewhereor cleaned for reuse or discharge. Not only is transportationpotentially dangerous, it’s also expensive; trucking the frac-water from eastern Pennsylvania to Ohio for deep well disposalcosts from $1.50 to $2.00 per barrel to dispose of producedwater at the injection well plus getting the wastewater to theinjection well requires many trucks each costing about$100/hour on an estimated six-hour typical trip in easternPennsylvania. Evaporation and crystallization technologies canrecover almost all of the produced water as pure distilledwater and create a salable salt product for uses such as roadde-icing or grey water softening, but that adds another,

higher level of costs. In the West, where water often can beinexpensive but scarce, it makes much more economic sense toclean up the wastewater and then sell it for landapplication[3].

3.Guidelines for technologyselection In order the select the more suitable technology for watertreatment there are issues related to the condition, as wellas the cost, of water that must be addressed. Here are some ofthe principal ones:

Most surface water used for fracking is fresh water, andthis surface water has variable quality, soultrafiltration is an effective way to treat thisinfluent source.Bacteria, corrosion and the buildup of solids in storagetanks are problems for disposal well management tosolve.While technical obstacles involved in salt concentrationcan be overcome through membrane and thermal processes,chemical pre-treatment to remove oil and grease from thebrine before it passes through the membranes is achallenge on a case-by-case basis.Reuse and recovery options make unconventional gasdevelopment sustainable, but they also involve handlingmore wastewater, so integrated discharge watermanagement and reuse solutions are necessary for safeand efficient treatment and recycling.The presence of Naturally Occurring RadioactiveMaterials, or NORMs, in frac flowback and produced watercan contaminate the salt product created bycrystallization. Pretreatment of brine can remove NORMssuch as radium.

Brine disposal into evaporative and wastewater ponds isgetting a great deal of critical attention, so it isimportant to put a cleaner disposal product into theponds or somehow reduce industry dependency upon them.Because industry operators do not just stay in fixedlocations, but frequently move from site to site todrill the most promising gas plays, water treatmentsystems should be mobile[4].

4.Some Research ProjectWhile progress has been made on the water quantity and qualityimpacts of shale gas development, challenges remain, includingthe potential cumulative long-term water impacts of theindustry. Therefore, additional water research andenvironmental policy changes will be necessary in order tofully realize the economic opportunity of the region’s naturalgas wealth while safeguarding the environment.

In the following there are reported some interesting researchproject focused on water reuse.

Project 1: Advancing a Web Based Decision Support Tools (DST)for Water Reuse in Unconventional O&G Development[5]

The objective of this project is the development of databaseand a decision support tool (DST) selecting and optimizingwater reuse options for unconventional O&G development with afocus on Flowback and Produced Water Management, Treatment andBeneficial Use for Major Shale Gas Development Basins.

Funding agency: US DOE-RPSEAStart date: 1/2012End date: 1/2016Funding: $286,984

Project 2: Engineered Osmosis for Advanced Pretreatment of O&GWastewater[6]

The objective of this project is further develop and optimizeengineered osmosis membranes and systems for treatment ofunconventional O&G wastewater (see figure 3). As main projectoutcomes there are:

Field test the engineered osmosis process on drillingand produced waters in the DJ BasinDevelop process design tools and life cycle assessmentFunding agency: US DOE-RPSEAStart date: 9/2011End date: 6/2015Funding: $1,323,805

Figure 3 – Engineered osmosis process scheme

Project 3: Advanced Biological Pretreatment[7]

The objective of this project is the development andevaluation of cost-effective pre-treatment technologies forO&G wastewater with emphasis on biological filtration. The major outcomes and outputs are the substantial removal of

dissolved organic carbon (96%) and chemical oxygen demand(89%) in produced water from the Piceance and Denver-Julesburgbasins

Funding agency: NSF/SRNStart date: 10/2012End date: 9/2017Funding: $1,400,390 to CSM

[1] Yoxtheimer, Dave. “Potential Surface Water Impacts fromNatural Gas Development.” pg.5.http://www.marcellus.psu.edu/resources/PDFs/Halfmoon%208-‐24-‐11.pdf

[2] Hammer, Rebecca and Jeanne VanBriesen. “In Fracking’sWake: New Rules are Needed to Protect Our Health andEnvironment from Contaminated Wastewater,”pg. 11. May 2012.http://www.nrdc.org/energy/files/Fracking-‐Wastewater-FullReport.pdf

[3] July 2011, Journal of Petroleum Technology, p. 50,“Flowback to Fracturing: Water Recycling Grows in theMarcellus Shale”, by Stephen Rassenfoss, JPT Online StaffWriter

[4] https://www.gewater.com/kcpguest/document-library.do/

[5] http://aqwatec.mines.edu/produced_water/tools/

[6] http://aqwatec.mines.edu/produced_water/tools/

[7] http://aqwatec.mines.edu/produced_water/tools/

Thin Film MembraneTechnology: Advances inNatural Gas TreatmentAuthor: Marcello De Falco, Associate Professor, UniversityUCBM – Rome (Italy)

1. Theme descriptionNatural gas (NG) treatments are the processes needed tosweeten and purify the extracted NG before feeding it to thegrid. Such processes are crucial to reach the gas puritytargets and constitute a large fixed and operative costs forthe NG production sector.

The main components to be removed in the NG purificationprocess are the acid gases as carbon dioxide (CO2) and hydrogensulphide (H2S) and, in many cases, the nitrogen (N2).

As reported in the following table, the contents of suchcomponents in the extracted NG stream can be high, leading tochallenging and expensive separation processes.

Groningen

(Netherlands)Laeq

(France)Uch

(Pakistan)

Uthmaniyah(SaudiArabia)

Ardjuna(Indonesia)

CH4 81.3 69 27.3 55.5 65.7

C2H6 2.9 3 0.7 18 8.5

C3H8 0.4 0.9 0.3 9.8 14.5

C4H10 0.1 0.5 0.3 4.5 5.1

C5+ 0.1 0.5 – 1.6 0.8

N2 14.3 1.5 25.2 0.2 1.3

H2S – 15.3 – 1.5 –

CO2 0.9 9.3 46.2 8.9 4.1

Table 1 – Composition of natural gas reservoirs (%vol)[1]

Traditionally, the separation is carried out by means of:

1-Absorption processes, by which the components to beseparated are absorbed on a liquid solvent in a packed columnand then separated in the solvent regeneration step. Theabsorption of the component on the solvent can be chemical(chemical absorption) or physical (physical absorption). Awide applied absorption industrial process is the ammineseparation (MDEA) unit for acid gases removal[2].

2- Adsorption processes, where selected components areadsorbed on the solid surface of specific particles. Then,increasing the solid bed temperature (Thermal Swing Adsorption– TSA) or reducing the pressure (Pressure Swing Adsorption –PSA), the gas is extracted and the solid is regenerated. Themost applied adsorption process is the PSA, used to remove CO2

from natural gas streams by solid materials with a highaffinity to carbon dioxide[3].

3- Cryogenic processes, known as low temperature distillation,which uses a very low temperature for purifying gas mixturesin the separation process exploiting the different gascomponents volatility. It is not applied for the acid gasremoval from natural gas due to the low concentrations neededthat makes the application of this technique noteconomical.But, a growing interest is given to separationprocesses using selective membranes thanks to their ease ofoperation, flexibility, smaller footprint and lower capitalrequirements.Basically, a membrane allows the transfer of

certain components but not of the others, thus leading to aseparation. A schematic layout is reported in Figure 1.

Figure 1 – Conceptual layout of a membrane-based separationprocess, with a membrane selective to component A.

Compared to the other natural gas separation techniques, themembrane process needs a lower energy requirement since itdoes not involve any phase transformation. Moreover, theprocess equipment is very simple with no moving parts,compact, relatively easy to operate and control, and also easyto scale-up and scale-down[4].In order to be applied in anindustrial process, a selective membrane must have thefollowing properties:

high permeability, leading to a high flux of theseparated component through the membrane thickness;high selectivity;high mechanical and thermal resistance at the separationunit operating conditions;the chemical resistance in the environment where themembrane is placed;low cost and long durability.

The permeability increases reducing the selective layerthickness, but at the same time, both the selectivity and themechanical resistance are penalized with thin membranes.Therefore, the membrane design requires an accurateoptimization. Usually, the applied membranes are composite andfabricated depositing a thin selective layer on a support ableto assure the needed mechanical properties (refer to Figure

2).

Figure 2 – Composite membrane architecture

In the following, some examples and applications of membraneapplications for CO2, H2S and nitrogen removal from natural gasare reported.

2.Membrane application for CO2

removalCarbon dioxide is the largest contaminant found in natural gasand, for this reason, a strong effort has been devoted todiscover solutions to apply selective membranes in the CH4/CO2

separation process.Currently, the only commercial membranesapplied for CO2 removal are polymeric, made by celluloseacetate, polyimides, polyamides, polysulfone, polycarbonatesand polyetherimide[5]. The most widely used material iscellulose acetate as used in UOP’s membrane systems: theSeparex membrane system has been applied in a number of large

NG plants installed worldwide (refer to Figure 3)[6],[7].Another widely applied commercial product is the cellulosetri-acetate (CTA) membrane developed by Cameron and calledCYNARA[8]: such a membrane is applied in world’s largest CO2

membrane plant for natural gas clean-up (700 MMcf/d).

Figure 3 – Separex membrane skids installed at an EOR projectin Latin America6.

Also Air Liquide has developed a membrane module for thepurification of NG by removal of CO2, H2S and water steam[9].

The system is called MEDALTM and is able to reach the pipelinespecification of 2 – 5% CO2 and 4 ppm H2S. Moreover, themembrane unit can be also used as a pre-treatment, removingthe majority of CO2 and H2S, followed by a typical amineprocess to further remove carbon dioxide.Another product isproposed on the market by ProSep[10]: the membrane isfabricated in a flat sheet and the arranged into a spiralwound module, then inserted into steel pressure-containingtubes. Such a membrane module has been applied in a number ofplants in U.S.A. and Colombia.

Figure 4 – ProSep membrane skid for CO2 removal installed inTexas.

The polymeric materials lead to a good separation performancebut are poisoned by aromatics, organic liquid and water. Forthis reason, pre-treatment units have to be installed beforethe membrane separation device, leading to an increase of thecosts and of the plant complexity.Some innovative membranetechnologies have been developed and installed. As an example,the CO2 separation membrane provided by Membrane Technology &Research (MTR)[11] is a new polymeric membrane able towithstand the various components of the NG mixture, thusreducing the impacts of the pre-treatments.

3.Membrane application for H2SremovalOn the contrary of the CO2 removal process by means ofmembranes, which now sees many industrial applications, theremoval of H2S is still in a phase of pre-industrial

development. The most interesting technologies are developedand tested by Membrane Technology & Research.MTR develops theSourSep™ systems bulk removal of H2S from pressurized sourgas[12]. The proposed architecture is based on a simple singlestage process, able, thanks to a proper membrane installation,to assure a bulk removal of H2S (>75%). The permeate streamgenerated in very sour and can be re-injected in theextraction well or processed in a conventional Claus unit. Theretentate stream has to be fed to other H2S removal unit (amineabsorption or a scavenger process) to further reduce thesulfur content. Figure 4 shows a SourSep™ installation.

Figure 5 – SourSep™ MTR installation for the removal of H2S.

Another membrane application for H2S removal, always proposedby MTR, is for the achievement of the stringent H2S contenttarget (< 40 ppm) if the NG is fed to an engine or a gasturbine. Such low composition is required to avoid themechanical components corrosion and damage. A scheme of such aprocess, proposed by MTR, is illustrated in Figure 6: afterthe NG compression, a raw gas stream is sent to a first filterand then to the membrane unit, able, also thanks to the highpressure and, consequently, to the large pressure drivingforce through the membrane, to drastically reduce the sulfurcontent.

Figure 6 – Process scheme for H2S removal from NG to reach theinlet feedstock quality targets for engines or gas

turbines[13].

Also UOP has developed and applied a polymeric membrane forthe removal of H2S, testing it in a pilot plant and thusdemonstrating the membrane stability at a wide operatingconditions range and the proper values of permeability andselectivity.

4.Membrane application for N2

removalSelective membranes are proposed also for NG denitrogenationbut, according to the DOE[14], the challenge of developingcompetitive membrane for N2/CH4 separation is not yetovercome.Both glassy polymers (nitrogen-permeable) or rubberypolymers (methane-permeable) membranes can be applied. But,while a nitrogen/methane selectivity of 15 at least isrequired to make the denitrogenation membrane economicallycompetitive, the highest selectivity available with currentpolymers is only about 2-3. Therefore, strong R&D efforts arerequired.Some interesting studies can be found in thescientific literature, as the works published by theUniversity of Massachusetts[15] and the AachenUniversity[16].Currently, MTR and CB&I are the onlymanufacturers of membranes for nitrogen removal. The membrane

module they developed, called NitroSepTM, have been applied forup to 20 MMSCFD NG plants and nitrogen composition up to15%[17] (refer to Figure 7).

Figure 7 – NitroSepTM module application in California[18].

[1] Biruh Shimekit and Hilmi Mukhtar, ” Natural GasPurification Technologies – Major Advances for CO2 Separationand Future Directions”, in Hamid Al-Megren “Advances inNatural Gas Technology”, InTech edition, 2012, p.235-270.

[2] http://www.bre.com/portals/0/technicalarticles/The%20Use%20of%20MDEA%20and%20Mixtures%20of%20Amines%20for%20Bulk%20CO2%20Removal.pdf

[3] Cavenati, S., A. Carlos, et al. (2006). Removal of carbondioxide from natural gas by vacuum pressure swing adsorption.

Energy & fuels, Vol. 20, No. 6, pp. 2648-2659.

[4] Stern, A. (1994). Polymers for gas separations: the nextdecade. Journal of Membrane Science, Vol. 94, No. 1, pp. 1-65

[5]http://www.membrane-guide.com/download/CO2-removal-membranes.pdf

[6] http://www.uop.com/?document=separex-membrane-systems-brochure&download=1

[7] http://www.uop.com/?document=uop-continued-development-of-gas-separation-membranes-technical-paper&download=1

[8]http://www.c-a-m.com/company/technology-works-here/cynara-membrane

[9]http://www.medal.airliquide.com/en/co-membrane/co-membrane-technology.html

[10]http://prosep.com/wp-content/uploads/2014/03/Gas-Membranes-Technology-Sheet-Letter.pdf

[11] http://www.mtrinc.com/co2_removal.html

[12] http://www.mtrinc.com/h2s_removal.html

[13] Pat Hale, Kaaeid Lokhandwala, “Advances in MembraneMaterials Provide New Solutions in the Gas Business”.

[14] http://www.netl.doe.gov/KMD/cds/Disk28/NG8-2.PDF

[15] ttp://www.ecs.umass.edu/che/henson_group/research/membrane/t-04163.pdf

[16]http://www.sciencedirect.com/science/article/pii/S0376738815302374

[17]http://www.cbi.com/technologies/technologies-servicesnitrogen-

rejection

[18]http://www.mtrinc.com/pdf_print/natural_gas/MTR_Brochure_Nitrogen_Removal.pdf