51 Biofuel Production

7/28/2019 51 Biofuel Production

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Biofuel Production

Prof. Tony Bridgwater

Bioenergy Research Group

Aston University, Birmingham B4 7ET

AV Bridgwater 2008


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Biomass

Carbohydrates e.g. corn, wheat

Sugarfrom cane or beet

Vegetable oil e.g. rape, palm, soy, jatropha

Lignocellulosics (lignin, cellulose and hemicellulose)e.g. wood, grass, straw, residues

Fertiliser and other inputs have a major impact on thesustainability of crops. Lignocellulosics generally have alower requirement.

There are many agronomical criteria for crop selection ofwhich yield (dry t / ha.y) is important for maximising use

of land


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Biofuels

Oxygenates

Methanol Ethanol

Butanol Mixed alcohols Dimethyl ether

Hydrocarbons Biodiesel Synthetic diesel

Synthetic gasoline Methane (CSNG)Other

Hydrogen

Generation

2G1G & 2G

1G & 2G2G2G

1G2G

2G1G & 2G

1G & 2G

First generation (1G)biofuels are from food suchas:

Ethanol from sugar, corn Biodiesel from rape oil

Second generation (2G)biofuels are from wholecrops such as wood andgrasses:

Synthetic diesel Methanol Ethanol


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Feeds, processes, products

Thermalconversion

Esterification

Ethanol,Butanol,

Chemicals

Biodiesel(FAME,RME)

Chemicals

Synthetic H/C,Ethanol, Butanol

Methanol,Chemicals

Power, Heat

Starch & sugars Oil plants

Biologicalconversion

Residues ResiduesLignocellulose

1G1G2G 2G


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1st and 2nd generation biofuels

First generation biofuels are from foodstuffs such as:

Ethanol from sugar, wheat or corn about 2 t/ha/y inEurope and USA, up to 6 t/ha/y from sugar cane in Brazil

Biodiesel from vegetable oils about 1 t/ha/yThese are important in introducing biofuels and increasingawareness.

Second generation biofuels are from whole crops such aswood, energy crops, residues, such as:

Synthetic diesel about 4 t/ha/y

Methanol about 8 t/ha/y Ethanol about 5 t/ha/yHigher yields and absence of competition with food give

these a longer term future


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Thermalconversion

Esterification

Ethanol,Butanol,

Chemicals

Biodiesel(FAME,RME)

Chemicals


Methanol,Chemicals

Power, Heat



ResiduesLignocellulose

Residues


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Bioethanol 5% limit in gasoline in Europe for cars (E5).

E85 (85% ethanol) is used in USA and E100 in Brazil

Concerns:

Logistical and market compatibility Vapour pressure

Hygroscopicity andlow temperature properties Materials compatibility

Low energy density ~1/3 Fuel compatibility


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Bioethanol technologyBiological processes

Mature technology for 1G from sugar, grain and corn.

Developing technology for 2G from lignocellulosics.

Hydrolysis releases C6 & C5 sugars, separates lignin. C6 sugars fermentation is commercial. C5 sugars fermentation needs to be demonstrated

Lignin needs to be utilised for energy efficiency In 1G technology, more energy is often input than is

derived in the ethanol, and significant improvements are

needed.Thermal processes

Commercial but mixed product with other alcohols.


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2 Generation bio-ethanol

Sugars

Byproducts

ResiduesWastesDistillation

Bioethanol

Hydrolysis

Syngas

Ethanol synthesis

Thermal Gasification

Syngas

Fermentation

Other alcohols

Biomass


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Thermalconversion

Esterification

Ethanol,Butanol,

Chemicals

Biodiesel(FAME,RME)

Chemicals


Methanol,Chemicals

Power, Heat



Residues ResiduesLignocellulose


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Biodiesel

Methyl esters of vegetable oil e.g. rape, soy, palm,sunflower to reduce viscosity and improve otherproperties.

The process is lowtemperature and catalytic:batch, semi-batch, semi-continuous, or continuous

Byproduct glycerine needsto be used

Concerns

Different oil sources result in different quality productsthat is difficult to control

Low temperature performance is variable and poor

Limited to 5% in diesel for vehicles in Europe due tomaterials and compatibility concerns


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Current status 1st generation Bioethanol is attractive as the technology is available

commercially Concerns over properties and energy density

Biological 1G technology from corn has low efficiency Biological 2G has some development challenges Thermal 2G gives mixed alcohol product

Biodiesel is attractive as a motor fuel as it can be readilyblended with diesel The quality is variable Low temperature characteristics are variable and poor Low yields and crops have high energy inputs

Competition of food vs fuel has led to high food price rises; There is also competition for land and sustainability issues


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Thermalconversion

Esterification

Ethanol,Butanol,

Chemicals

Biodiesel(FAME,RME)

Chemicals


Methanol,Chemicals

Power, Heat



ResiduesResiduesLignocellulose


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Synthetic hydrocarbons

Synthetic hydrocarbons include diesel, gasoline, kerosene

They are entirely compatible with conventional fuels in all

proportions, but are much cleaner. At least in the medium term, these are likely to be the

biofuels of choice due to their ease of assimilation into

markets, familiarity by the vehicle industry and consumers,energy density,


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Routes to 2nd G hydrocarbons

1. Thermal gasification

a) + Fischer Tropsch

b) + Methanol synthesis + upgrading by MTG or MOGD2. Pyrolysis + upgrading

a) by hydro-processing

b) by zeolites3. Hydro-processing vegetable oil


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Syngas

1: Biofuels via thermal gasification

Biomass

Solid Biomass Gasification

Fischer Tropsch

MTG

Conventional synthetic gasoline and diesel

Mt synfuelMOGD

Refining

Methanol


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Challenges

The process most commonly considered is thermalgasification to clean syngas and synthesis of hydrocarbonsby Fischer-Tropsch (FT)

Biomass is a widely dispersed resource that must betransported over large distances at significant cost.

Biomass preparation for entrained flow gasification can be:

Torrefaction to render biomass more friable for grinding Liquefaction by fast pyrolysis

Gasification technology is unproven at large scale.

Gas cleaning is a major challenge and unproven The minimum economic size of Fischer Tropsch is widely

considered to be 20,000 bbl/day or nearly 1 million t/y

biofuels requiring nearly 5 million t/y biomass.


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Fischer Tropsch

Syngas

Pretreatment by pyrolysis

MTG

Conventional synthetic gasoline and diesel

Fast pyrolysis

75% wt. liquid

Gasification

Torrefaction

85% wt. solid

Biomass

Mt synfuelMOGD

Refining

Methanol


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Pretreatment Torrefaction is low temperature pyrolysis to dry and

partially devolatilise biomass. The product yield isaround 85% and can be more readily ground like coalfor gasification.

Fast pyrolysis produces a mobile liquid (bio-oil) with upto 10 times the energy density of biomass. The productyield is up to 75%

Liquids are easier to handle, store and transport. Fast pyrolysis can be decentralised and located nearthe biomass resources

Conversion of biomass to a liquid near sourcereduces transport costs, and reduces gasificationcosts.

Pressurised oxygen gasification of liquids is easier

and lower cost than solid biomass


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Pyrolysis + Fischer Tropsch

Gasn.

F-T

Biomass

Biomass

Biomass

Biomass

Biomass


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Capital costs

0

2000

4000

6000

8000

10000

12000

14000

16000

0 2 4 6 8 10 12

Pyrolysis + large FT

Small gasification +small FT

Biomass input million dry t/y

Capital cost, million

Large gasification + FT

Small FTunproven

Large

gasificationunproven

Small pyrolysis& large FT

proven


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Solid vs liquid gasification

Capital cost increase of ~10% due to diseconomies ofscale in small pyrolysis plants

Capital cost reduction of ~15% due to lower feedhandling costs

Capital cost reduction of ~10% due to lower costs infeeding a liquid to a gasifier at pressure compared tosolid biomass

Cost reduction of ~10% from absence of alkali metalsslagging and erosion

Efficiency loss of ~5% due to additional processing step


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Methanol based processes

Methanol well established technology from natural gas.

MTG (Methanol To Gasoline) commercial technologyproven in New Zealand from naturalgas. High yield and high efficiency

MOGD (Methanol to Olefins, Gasolineand Diesel) well researched tech-nology. High yield and high efficiency

Mt synfuel new process via propylene

Methanol, MTG etc are moreselective than FT and potentially giveup to 30% higher yields (from ~50%to ~65% on an energy basis)


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2: Upgrading bio-oil directly

Production of hydrocarbons requires rejection of the oxygen: Hydro-processing rejects oxygen as H2O

C1H1.33O0.43 + 0.77 H2 CH2 + 0.43 H2O

Separate process, requires hydrogen, high pressure Gives projected yield of around 25% naphtha-likeproduct for refining, without H2 or 15% with H2

Zeolite cracking rejects oxygen as CO2 C1H1.33O0.43 + 0.13 O2 0.66 CH2 + 0.34 CO2 Close coupled process requiring constant catalyst

regeneration.

No hydrogen requirement, no pressure Gives projected yield of around 20% aromatics

Feeding to conventional refinery provides quality

control and economies of scale


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Costs of upgraded bio-oil

Yield,wt%

/tproduct

HHV,GJ/t

/GJproduct

/toe

Wood feed (daf) 100 67 20 3 145Pyrolysis oil output 70 147 19 8 331

Diesel (EXCL H2) 23 592 44 13 578

Diesel (INCL H2 from biomass) 13 880 44 20 860

Gasoline 22 453 44 10 443

FT diesel * # 20 1362 42 1395

MTG gasoline * 26 43

Crude oil at $100/bbl - 560 43 15 560

Basis: 1000 t/d daf wood feed at 67 /dry t, 2006 except *# DENA report 2006


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3: Hydro-processing vegetable oil

Bio-diesel (by esterification of crude vegetable oil) iscurrently limited to 5% of conventional diesel.

Vegetable oil can be hydroprocessed to synthetic dieseland Neste have built a 100,000 t/y plant in Finland basedon palm oil and other vegetable oils. Other plants areunder construction

Generation 1 as feed is a foodstuff and product is 2nd

generation equivalent

The hydrogen requirement is much less than fast

pyrolysis liquid, but the vegetable oil productivity,sustainability and food competition issues remain.


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Thermal process summary

Conventional gasoline and diesel

Refining

Methanol

synthesis

MTG MOGD

Syngas

Liquidbio-oil

Mt-

Synfuels

Biomass

Gasification Zeolitecracking

Hydro-treating

FischerTropsch

synthesis

Liquid

bio-oil

Fast pyrolysis


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Challenges Improve crop yields and characteristics Improve 1st and 2nd generation bioethanol technology Improve lignocellulosics pretreatment for 2nd generation

Demonstrate C5 fermentation Demonstrate large scale thermal gasification Demonstrate large scale gas cleaning & conditioning

Demonstrate small scale hydrocarbon synthesis Demonstrate fast pyrolysis liquids upgrading Develop integrated biorefineries Improve catalysts Match catalysts to biomass derived primary products Robustly compare alternative systems Reduce costs


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Thank you

Documents

51 Biofuel Production