The refining industry is faced withmany challenges that may signifi-cantly affect refinery processing

schemes over the next five years andbeyond. First, the recommendations ofthe European Auto-Oil I and II pro-grammes have resulted in unprecedent-ed gasoline and automotive diesel fuelquality requirements (Table 1).

In 2005, the maximum automotivediesel sulphur level will be reduced to50ppm. Sulphur levels as low as 10ppmwill be the rule in some countries. At thesame time, the specified cetane number,polyaromatics, specific gravity and 95 percent distillation point will also undergochanges. These will directly affect therefinery diesel pool formulation.

The probable reduction of 10°C to20°C of the diesel 95 per cent distillationpoint will impact on the refinery dieseloutput. For example, a 10°C reductionin diesel cut-point will diminish thediesel pool volume by about 5 per cent.

Second, as a result of increasing roadtransport in Europe and the success ofdiesel automobile engines, particularlyin France, the projected demand fordiesel fuel shows an increase of at least18 per cent over the next 10 years, andeven more in some scenarios, while themarket share for naphtha is expected todecline slightly (Table 2).

Jet fuel demand is also climbingrapidly (+40 per cent) due to the expan-sion of air transport. Demand fordomestic fuel oil continues its long-termdecline. European refineries must there-fore adapt their product slate signifi-cantly, considering that dieselproduction capacity is already bottle-necked while the previously projecteddiesel end-point specifications willresult in a 5 to 10 per cent loss of currentproduction.

These long-term trends will compelrefiners to modify their processing con-figurations in order to increase higher-quality middle distillate production. Inthe past, the prevailing market forecastsand economics led refiners to invest inFCC complexes to satisfy the more

immediate gasolineneeds, which is whymost European refineryconversion schemeswere limited to FCCsand visbreakers.

To produce highyields of high-qualitymiddle distillates fromvacuum gasoil (VGO),refiners will have toinvest in hydrocrackersto meet future marketdemand. Although theyare not likely to shutdown FCC operations on the solepremise that FCC units do not producehigh yields of high quality middle distil-lates, they will have to implement somereduction in FCC throughputs. A realis-tic case study will include an FCC unitand a hydrocracker.

Hydrogen management is anotherkey point to consider when comparingtechnical solutions in addressing the dif-ficult problem of diesel quantity andquality. The optimum overall schemewill be one that selectively adds hydro-gen into the diesel pool.

Case studiesThe European refinery case studiesdetailed in this article processes 10megatons/year of a North Sea crude. Therefinery’s bottom-of-the-barrel unitsinclude:

——An FCC plant——A vacuum residue visbreaking unit ——A diesel HDT plant, sized for year2000 specifications (not shown in thefigures that follow).

The residue from the visbreaker isused for production of 40cSt fuel oil.

The effects of adding the follow-ing hydrocracking technologies wereanalysed:—— Mild hydrocracking——High pressure hydrocracking—— IFP hydroconversion technology(Hytail).

The study draws upon informationgathered from over 40 industrial units.The results, primary product distribu-tion, diesel and domestic fuel oil poolconstitution, and main product charac-teristics prior to hydrotreatment, aregiven in Tables 3 to 5.

A hydrocracking strategyfor a competitive market

A description of a novel hydrocracking technology that offers refiners a costeffective way of complying with European 2005 diesel specifications, takinginto account new configurations necessary to meet capacity and quality targets

P Marion D Duée E BenazziIFP

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PPTTQQ SSUUMMMMEERR 22000011w w w. e p t q . c o m

23

11999966 CCuurrrreenntt 22000055((eexxppeecctteedd))

Sulphur, ppm max 500 350 10–50Cetane number, min 49 51 52–54?Polyaromatics, wt% max – 11 1–6?Sp. Gr, max 0.860 0.845 0.825– 0.845?ASTM D-86 – 360 340–350?

95% vol, °C max

Table 1

Diesel oil specifications in Europe

CCuurrrreenntt 22000055 ((eexxppeecctteedd)) 22001100 ((eexxppeecctteedd)) TTeenn--yyeeaarr ddiiffffeerreenncceeMMTTPPAA MMaarrkkeett MMTTPPAA MMaarrkkeett MMTTPPAA MMaarrkkeett MMTTPPAA MMaarrkkeett

sshhaarree,,%% sshhaarree,,%% sshhaarree,,%% sshhaarree,,%%

Naphtha 166 38 171 37 177 37 11 -1.6Jet fuel 41 9 49 11 57 12 16 +2.4Diesel 142 33 156 34 168 35 26 +2.1Domestic 84 20 82 18 80 16 -4. -2.9

fuel oilTotal 433 100 458 100 482 100 49 –

Table 2

European demand and market share for middle distillates

Base caseRefinery’s year 2000 configuration

(Figure 1)The refinery produces slightly morenaphtha and less diesel than Europeandemand. With a cetane number of 49and a sulphur content of 2400ppm, theentire diesel pool must be sent to a deepHDS plant where the specifications of 51cetane and 350ppm sulphur are easilyobtained with the North Sea crude oil.

The domestic fuel oil (DFO) charac-teristics are close to the specifications.To obtain the minimum cetane numberrequired for this stream, one third of thedomestic fuel oil will be hydrotreated.The deep diesel HDS flow is therefore2.82 MTPA for the refinery's crude oilthroughput of 10 MTPA.

Case 1After 2005 (no change in configuration)

The impact of year 2005 specificationson refinery performance was studied.Primarily due to the reduction of dieseloil ASTM D-86 95 per cent point from360°C to 340°C, diesel fuel production isreduced from 30 per cent of the totalnaphtha -p lu s -midd le -d i s t i l l a t e sobtained in year 2000, to 27.9 per centin year 2005.

Considering the market share of 34per cent given in Table 2 for the sameyear, the gap between refinery produc-tion and market need for 2005 will havemore than doubled compared with thatfor the year 2000.

By 2005, with the same refinery con-figuration, the FCC throughput willhave been increased by 12 per cent,which, of course, does not fit well withthe need to increase both diesel poolquantity and quality (Figure 2). Becauseof the increased light cycle oil (LCO)production, the cetane in the pool isalso deeply affected.

Diesel oil cetane number beforehydrotreating is only 47.9, which repre-sents a gap of 4 to 6 points comparedwith the expected 2005 specifications.With this type of feedstock, such anincrease in cetane number requiresextremely severe operating conditionsthat cannot be achieved in the existingHDT plant, even after revamping. In casea minimum cetane number is requiredfor the domestic fuel oil, the entire DFOoil pool must also be deeply hydrotreat-ed. In these conditions, the total middledistillates hydrotreating throughput isincreased by 24 per cent, and a newhigh-pressure HDT must be installed.

The average naphtha pool sulphurlevel will be 270ppm, which impliesadding high-severity, post-treatmentunits to attain the required sulphur lev-els of 10–50ppm. This level of severitywill be accompanied by some octaneloss, which means that, in some cases,

the octane balance could well becometight and will require more investment.

Case 2Mild hydrocracker

Based on preliminary studies, the addi-tion of a high-pressure hydrocrackingunit was not an economic solution due tothe high investment requirement andhigh hydrogen consumption. In the alter-native case, a mild hydrocracker(designed for 30 per cent conversion and

a residue maximum sulphur content of0.05 wt%) is added to the refining schemeupstream of the FCC unit (Figure 3).

The advantages of this configurationon FCC operation are well known:——Reduced FCC coke, slurry and LCOyields in favour of LPG and naphthayields—— Increased LCO cetane number——FCC naphtha sulphur levels reduced to15ppm——Reduction in FCC SOx emissions.

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FFuuttuurree 22000055 wwiitthhFFuuttuurree 22000055 MMHHDDCC aanndd

CCuurrrreenntt FFuuttuurree ((22000055)) wwiitthh MMHHDDCC HHyyttaaiillwwtt%% wwtt%% wwtt%% wwtt%%

DDiieesseell DDFFOO DDiieesseell DDFFOO DDiieesseell DDFFOO DDiieesseell DDFFOOStraight run 78.4 12.0 71.4 13.2 66.1 – 57.0 –dieselKerosene 13.8 73.3 20.2 66.2 11.7 71.6 9.4 60.3LCO – 14.7 – 20.6 – 5.7 – –VB diesel 7.8 – 8.4 – 7.0 – 6.4 –MHDC diesel – – – – 15.2 22.7 - 39.7Hytail diesel – – – – – – 27.2 –Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

Table 4

Diesel and domestic fuel oil pool constitution

FFuuttuurree 22000055 wwiitthhCCuurrrreenntt FFuuttuurree ((22000055)) FFuuttuurree 22000055 MMHHDDCC aanndd

wwiitthh MMHHDDCC HHyyttaaiill**

MMTTPPAA %% MMTTPPAA %% MMTTPPAA %% MMTTPPAA %%Naphtha 3.17 41.0 3.32 43.5 3.07 38.9 3.26 37.3Jet fuel 0.73 9.4 0.82 10.7 0.84 10.6 0.93 10.7Diesel 2.32 30.0 2.13 27.9 2.57 32.6 2.98 34.1Domestic 1.50 19.4 1.36 17.9 1.41 17.9 1.56 17.9fuel oilTotal 7.72 100.0 7.63 100.0 7.89 100.0 8.73 100.0

* Including 1.2 MTPA of imported atmospheric residue

Table 3

Refinery’s product distribution (crude =10 MTPA)

Figure 1 The refinery’s current situation

Adding a mild hydrocracker signifi-cantly increases the diesel-to-naphtharatio and the refinery product slatealmost matches market requirements.

The results from the refinery simula-tion in this configuration show thatmost of the LCO produced by the FCCcan be used to control fuel viscosity.Under these conditions, the cetanenumbers in the diesel and DFO pools aresignificantly increased (Table 5).

With a cetane number of 39 and a sul-phur content of 600ppm, the DFOmeets specifications without furtherhydrotreatment, even in countrieswhere a cetane number of 40 is speci-fied. In this case, a small amount ofcetane booster will be added to the pool.

The diesel fuel, with a cetane numberof 48.2 before HDT, will still requiresevere hydrotreating to attain a mini-mum of 52. The necessary cetane gain of3.8 points cannot be accomplished inthe existing unit without revamping.Depending on the case, the cetane gaincan be achieved in a new high-pressureHDT plant (preferably), or in the mostfavourable cases, in the existing plantafter extensive revamping.

Total HDT throughput is 9 per centlower compared to the current situation.A sulphur level as low as 15ppm in theFCC naphtha will result in a diesel poolwell below the most stringent foresee-able specification of 10ppm, achievedwith virtually no octane loss.

Case 3New technology

Hytail is a new IFP hydrocracking tech-nology specifically developed to solveEuropean refining problems (Figure 4).It is optimised for cracking heavy atmo-spheric gasoils or light vacuum gasoilsthat will be in excess in refineries in2005 after reducing diesel 95 per centpoint specification. Because it operatesunder much milder operating condi-tions than a conventional hydrocracker,and the process flow scheme is muchsimpler, this unit investment cost isremarkably low, and the economics areattractive.

The key feature of this process is thatit operates at pressure levels and requirescapital investment comparable to thoseof a mild hydrocracker, but still offersthe high conversion levels and the highdiesel quality of a high pressure hydroc-racker. If we plot diesel quality (ie, poly-aromatics in this example) as a functionof hydrogen partial pressure for thesame conversion level of 80 per cent, azeolite catalyst can be used, enabling theunit to operate at a 25-bar lower hydro-gen partial pressure, for the same levelof quality (Figure 5).

This is explained by the zeolite’sgreater activity, which requires a much

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FFuuttuurree 22000055 wwiitthhFFuuttuurree 22000055 MMHHDDCC aanndd

CCuurrrreenntt FFuuttuurree ((22000055)) wwiitthh MMHHDDCC HHyyttaaiillDDiieesseell

Sulphur, ppm 2400 2300 2100 1900Cetane 49.1 (spec 51) 47.9 (spec 52) 48.2 (spec 52) 50.7 (spec 52)

DDFFOOSulphur, ppm 2100 2600 600 500Cetane 37.7 37.0 39 40.7

NNaapphhtthhaa ssuullpphhuurr,, ppppmmFCC naphtha 250 250 15 15Naphtha pool 105 110 <10 <10

Diesel HDT overall Base Base + 24% Base – 9% Base – 23%throughput

Diesel HDT Existing Existing plus Existing plus Revampnew HP unit probable new HP existing unit

Table 5

Main product characteristics prior to hydrotreatment

Figure 2 Refinery situation after 2005

Figure 3 Adding a mild hydrocracker

lower operating temperature, and whichin turn favours more efficient hydro-genation. Zeolite catalyst systemsappear as the best choice in Europewhere the emphasis is on maximumquality diesel fuel.

Moreover, selecting a light feedstock(LVGO or HGO) instead of the usualhydrocracking feed (HVGO) makes pos-sible an additional 20- to 25-bar reduc-tion in hydrogen partial pressure.

The result is that, in the Hytail pro-cess, which basically cracks light feed-stocks on a zeolite catalyst, theoperating pressure can be about 50 barlower than in conventional plants. Theprocess offers the same product yieldslate and quality as the HP hydrocrack-er, but with a much lower hydrogen par-tial pressure resulting in a lowerinvestment cost (Table 6).

Another characteristic of this lowinvestment process is that its

flowscheme is simpler than that of anHP hydrocracker. It is similar to a dieselHDT plant with an additional column,the diesel–residue splitter).

The combination of these featuresresults in attractive economics (Table 7).Hytail investment cost is only about 40per cent of the investment of an HPhydrocracking unit, while H2 consumedin the unit is only 28 per cent of the HPhydrocracker.

The last case in this study concernsthe addition of a Hytail plant havingpreviously installed a mild hydrocracker.Feedstock to the Hytail plant is thelighter third of the total vacuum gas oil(TBP cut: 350–410°C), while feedstock tothe mild hydrocracking unit is the 410-565°C cut. Taking into account the con-version in the mild hydrocracker, theFCC throughput is reduced to 55 percent of design. To maintain a minimumFCC feed rate at 70 per cent of design,

an extra 1.2 MTPA of atmosphericresidue was imported.

Owing to the high quality of dieselfuel from the Hytail unit, the diesel pooland domestic fuel oil pool cetane num-bers are increased to 50.7 and 40.7,respectively, before the HDT step. Thedomestic fuel oil meets specifications.With such a high quality level, thediesel fuel can be reasonably upgradedto the sulphur specification by therevamped diesel HDT plant.

Taking into account that Hytail dieselis sent directly to the diesel pool, thenew HDT unit’s throughput is only 77per cent of its original design.

EconomicsTable 8 provides the results of an eco-nomic comparison between a mildhydrocracking unit, a mild hydrocrackerplus a Hytail unit, and an FCC unit plusan upstream high pressure hydrocrackerthat replaces the Hytail and mild hydro-cracking units.

The high pressure hydrocracker con-version level is adjusted in order toobtain a refinery material balance and

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Figure 4 The Hytail process

Figure 5 Comparison of zeolite and amorphous catalyst performance

HHiigghhHHyyttaaiill pprreessssuurree

HHDDCCCrude oil Brent BrentFeedstock TBP 350–410 350–565cut points, °C

Unit capacity, BPSD 23 000 73 000Conversion Full FullOperating pressure, bar P–50 PResidence time, h–1 0.80xBase BaseISBL capital 95 235investment, 106$

H2 consumption, TPA 21 400 75 400

Table 7

Hytail economics

HHiigghh HHyyttaaiill pprreessssuurree

HHDDCCCrude oil Brent BrentConversion Full FullLPG, wt% 3.00 3.10Naphtha, vol% 34.7 35.5Diesel, vol% 77.8 78.3H2 consumption, wt% 1.85 2.05DDiieesseell pprrooppeerrttiieess

ASTM D-86, 340 34095% vol, °C max

Flash point, °C 70 70Cetane number 56 55Sulphur, ppm <10 <10Polyaromatics, wt% <1 <1

Table 6

Product yields and characteristics

product quality pattern equivalent tothose obtained with a mild hydrocrack-er plus a Hytail unit. Because bothHytail and mild hydrocracking unitsoperate at much lower pressures, theinvestment for these two units is lowerthan the investment for a high-pressurehydrocracker of the same capacity.

The hydrogen consumption is muchhigher in the HP hydrocracking casebecause this unit operates at higher pres-sure and hydrogenates the residue thatis sent to the FCC to a high degree. Inthe mild hydrocracking-plus-Hytailscheme, hydrogen is selectively addedto the diesel fuel with as little hydrogenas possible going to the unconvertedresidue being sent to the FCC.

ConclusionHydroconversion, whether or not com-bined with some degree of reduction inthe FCC throughput, is the key optionfor European refineries when their objec-tive is to meet diesel 2005 specificationsand production requirements. Whilediesel sulphur specifications are oftenachievable by revamping existing dieselHDT units, the required cetane level (acharacteristic that is not easily improved)appears as the refinery bottleneck.

Mild hydrocracking is a cost effectiveoption that will solve part of the prob-lem. It also leads to very low sulphurcontent in the FCC naphtha, enablingthe most stringent sulphur specificationin the naphtha pool to be met.

Hytail is a new hydrocracking tech-nology that fits well with the Europeanconstraints. When the mild hydrocrack-

er is combined with a Hytail unit, therefinery’s diesel-to-naphtha ratioincreases to meet the projected Euro-pean yield slate, while the total produc-tion of naphtha, jet, diesel and domesticfuel oil is increased by 14 per cent.

In that case, the diesel oil pool prop-erties attain values that enable them tomeet the 2005 target, using the existingdiesel HDT units, after a moderaterevamp.

The comparison between the com-bined Hytail-plus-mild-hydrocrackingunits and a stand-alone high pressurehydrocracking unit, operating at par-tial conversion and offering the samerefinery material balance and productquality, shows that Hytail-plus-mild-hydrocracking is the more effective solu-tion in terms of capital investment andhydrogen management.

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MMHHDDCC pplluuss SSttaanndd--aalloonneeMMHHDDCC HHyyttaaiill aatt HHPP hhyyddrrooccrraacckkeerr aatt

ffuullll ccoonnvveerrssiioonn 5500%% ccoonnvveerrssiioonn

VGO capacity, MTPA 2.88 3.68 3.68ISBL capital Investment, 106 US$ 119 214 235H2 consumption, t/year 22 000 39 100 59 600

Table 8

Economics“Hydroconversion, whetheror not combined with somedegree of reduction in theFCC throughput, is the keyoption for European refinerieswhen their objective is tomeet diesel 2005 specifications”