Biofuel production via therm al gasification of biom ass By Lasse - - PowerPoint PPT Presentation

Biofuel production via therm al gasification of biom ass

By Lasse Røngaard Clausen Assistant professor Section of Thermal Energy Technical University of Denmark (DTU)

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DTU Mechanical Engineering

W ho am I ?

• Assistant Professor at the Section of Thermal Energy
• Expertise in thermodynamic modeling and energy/ exergy optimization of

complex energy systems – Focus on biofuel production via thermal gasification

• Other research interests:

– Exergy analysis of energy systems – Thermoeconomics – Integration of agriculture in the energy system – nutrient recycling

• Recent projects at the Section of Thermal Energy

– High temperature heat pumps – Low temperature heat to power (ORC, Kalina, other mixtures of working fluids, solar thermal power)

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DTU Mechanical Engineering

Biofuel production via therm al gasification An overview

Biomass Gasifier Liquid fuel Synthesis reactor

Biomass

Syngas (synthesis gas)

• Consist of CO and H2

(the building blocks for chemical synthesis)

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DTU Mechanical Engineering

Agenda

• Gasification of biomass

– Gasifiers developed at DTU

• Biofuel production plants

– Proposed designs

• Biofuel plants based on entrained flow gasification of torrefied

biomass

• Biofuel plants plants based on the Two-Stage Gasifier
• Biofuel plants integrating electrolysis of water

– Future work

• Biofuel plants based on an oxygen-blown Two-Stage Gasifier
• Biofuel plants based on an entrained flow gasifier with

integrated torrefaction of biomass

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DTU Mechanical Engineering

Gasifiers developed at DTU: The Tw o-Stage Gasifier

• Downdraft

fixed bed

• High energy

efficiency (~ 93% )

• No tar and low

CH4 in gas

• Temperature
• ut: 730°C
• Small-scale

plant (max 5 MWth)

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DTU Mechanical Engineering

Gasifiers developed at DTU: The Tw o-Stage Gasifier ( The Viking Gasifier)

• The Viking gasifier

(picture) is 15-20 kWe

• It has been

successfully upscaled to 100 kWe

• A 500 kWe plant is

being built at the moment.

• The Technology is

now owned by the Danish company Weiss.

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DTU Mechanical Engineering

Gasifiers developed at DTU: The Pyroneer gasifier

• 2 fluidized beds
• High tar and CH4 in gas
• Temperature out: ~ 650°C
• Can convert almost any kind of

biomass – Straw – Biogas residue

• The ash can be used as

fertilizer because temperatures are below 730°C

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DTU Mechanical Engineering

Gasifiers developed at DTU: The Pyroneer gasifier

• The Technology is now owned by

the Danish power company DONG Energy

• A 6 MWth demonstration plant is

under operation at the moment (picture).

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DTU Mechanical Engineering

Straw Manure Biogas residue Sewage sludge Other agricult. waste Meat-and-bone meal Wood Etc. Cofiring with coal,

• il or gas into

existing powerplant boilers Indirectly fired gasturbines Large Stirling engines Production of liquid fuels or more valuable chemicals Directly fired gasturbines, combustion engines

• r fuel cells (with gas

cleaning) Industrial waste Household waste

LT-CFB plant

Pyroneer gasifier, or Suitable plant sizes : ~ 5-150 MWth (depending on the fuel and the application)

Reforming of the tar and CH4 in the gas is required

Gasifiers developed at DTU: The Pyroneer gasifier

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DTU Mechanical Engineering

Agenda

• Who am I?
• Gasification of biomass

– Gasifiers developed at DTU

• Biofuel production plants

– Proposed designs

• Biofuel plants based on entrained flow gasification of torrefied

biomass

• Biofuel plants plants based on the Two-Stage Gasifier
• Biofuel plants integrating electrolysis of water

– Future work

• Biofuel plants based on an oxygen-blown Two-Stage Gasifier
• Biofuel plants based on an entrained flow gasifier with

integrated torrefaction of biomass

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DTU Mechanical Engineering

Biofuel production via therm al gasification An overview

Biomass Gasifier Liquid fuel Synthesis reactor

Biomass

Syngas (synthesis gas)

• Consist of CO and H2

(the building blocks for chemical synthesis)

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DTU Mechanical Engineering

1. Biofuel plants based on entrained flow gasification of torrefied biomass

• Shows the potential of state of the art within biofuel plants

2. Biofuel plants based on the Two-Stage Gasifier

• Shows the potential of small-scale biofuel plants
• Economy at this scale is a great challenge – this must be outweighed by the

advantages of small-scale (high-efficiency gasifier, co-production of heat). 3. Biofuel plants integrating electrolysis of water

• Enables full conversion of the carbon in the biomass to biofuel
• Enables conversion of electricity from fluctuating renewables (wind, solar) to

biofuel for the transportation sector.

Biofuel plants: Proposed designs

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DTU Mechanical Engineering

• Very large scale is possible by using torrefied wood pellets as fuel.
• Torrefied wood has increased energy density (~ 20 MJ/ kg), which increases gasifier

energy efficiency.

• Almost all the syngas can be converted to fuel because the syngas contains few

inerts (CH4, N2) – oxygen-blown gasification is used.

DME-RC

59% 100% 90% DME Wood Torrefication 10% Gasification 73% WGS 71% 17% Synthesis 1% Off-gas boiler 11% 2%

Chemical energy Heat

• Modeling shows potential of energy

efficiencies up to 59% (LHV) from untreated wood to DME – 64% including net-electricity.

Biofuel plants: Proposed designs ( 1 / 3 ) Biofuel plants based on entrained flow gasification of torrefied biom ass

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DTU Mechanical Engineering

• Small-scale due to the Two-Stage Gasifier
• High energy efficiency due to high energy efficiency of gasifier
• Modeling shows potential of energy efficiencies up to 58% (LHV) from untreated

wood to DME – no net-electricity.

Fly ash Wet Wood Methanol reactor Gas-liquid separator Gas engine Methanol (97 mol%) Ash gasifier 750 C 1 bar Water Steam 200 C Dry wood + steam Pyrolysis reactor Air 115 C Air 630 C 730 C 200 C 40 C 100 bar 220 C 40 C 400 C ~CO2

Chemical energy Heat

Biofuel plants: Proposed designs ( 2 / 3 ) Biofuel plants based on the Tw o-Stage Gasifier

58% 100% 93% DME Wood 7% Gasification Synthesis 24% Engine 11%

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DTU Mechanical Engineering

• All the carbon in the biomass ends up in the biofuel – therefore no CO2 emission.
• Potential for storing surplus electricity from renewables (wind, solar, etc.)
• Modeling shows potential of energy efficiencies up to 115% from untreated wood to

methanol – with electricity consumption the efficiency drops to 58% .

Water Gas Biomass O2 Gasifier Electrolyser O2 H2 Syngas Typical gas com position from gasifier ( m ol% ) : 29% H2 51% CO 7% CO2 13% H2O.

Chemical energy Heat

Biofuel plants: Proposed designs ( 3 / 3 ) Biofuel plants integrating electrolysis of w ater

115% 100% 90% MeOH Wood Torrefaction 10% 96% 18% 4% Off-gas boiler 22% 99% Electrolysis 30% 24% 69% 45% Synthesis Gasification Electricity

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DTU Mechanical Engineering

W hy integrate electrolysis of H 2O/ CO2 in a biofuel plant?

• If great amounts of fluctuating renewables (wind, solar, etc.) needs to be integrated

in the electricity grid. This is the case of Denmark: – In 2011 28% of the Danish electricity consumption was provided by wind. – In 2020 the official goal is 50% – In 2050 the official goal is a fossil free energy system.

• If the biomass resource shows to be very limited and expensive.

In a recent Danish Study (CEESA), Biofuel plants with integrated electrolysis supplies 44% of the fuel for the Danish transportation sector in the 2050 Scenario (see next slide).

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DTU Mechanical Engineering

The CEESA 2 0 5 0 renew able energy scenario

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DTU Mechanical Engineering

Agenda

• Gasification of biomass

– Gasifiers developed at DTU

• Biofuel production plants

– Proposed designs

• Biofuel plants based on entrained flow gasification of torrefied

biomass

• Biofuel plants plants based on the Two-Stage Gasifier
• Biofuel plants integrating electrolysis of water

– Future work

• Biofuel plants based on an oxygen-blown Two-Stage Gasifier
• Biofuel plants based on an entrained flow gasifier with

integrated torrefaction of biomass

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DTU Mechanical Engineering

The planned future work continues to explore the integration of electrolysis in biofuel plants 1. Biofuel plants based on an oxygen-blown Two-Stage Gasifier + SOEC/ SOFC

• Can reach unprecedented energy efficiencies

(biomass + electricity ⇒ biofuel) 2. Biofuel plants based on an entrained flow gasifier with integrated torrefaction of biomass + electrolysis

• The loss of chemical energy due to torrefaction is eliminated
• High energy efficiency

Biofuel plants: Future w ork

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DTU Mechanical Engineering

Biofuel plants: Future w ork ( 1 / 2 ) Biofuel plants based on an oxygen-blow n Tw o- Stage Gasifier + SOEC/ SOFC

• Work based on the proposed designs: 2 and 3
• Higher energy efficiency due to greater conversion of syngas to biofuel (no N2)
• Integration of a SOEC/ SOFC. Used as SOEC when electricity is cheap – used as

SOFC when electricity is expensive.

Chemical energy Heat

• The project will include both theoretical

and experimental work.

• Partners:

– The Gasification group at DTU – Haldor Topsoe – Danish Gas Technology Centre (DGC)

179% 100% 93% SNG Wood Gasification 7% 42% 142% SOEC Electrolysis 14% 128% Synthesis Electricity

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DTU Mechanical Engineering

125% 100% 80% MeOH Wood Torrefaction 1% 153% 10% 4% Off-gas boiler 24% 91% Electrolysis 27% 64% Synthesis Gasification Electricity

19%

Biofuel plants: Future w ork ( 2 / 2 ) Biofuel plants based on an entrained flow gasifier w ith integrated torrefaction of biom ass + electrolysis

• Work based on the proposed designs: 1 and 3
• The volatiles released during torrefaction is used as a chemical quench in the
• gasifier. This increases gasifier efficiency, and ensures that no biomass is lost in the

torrefaction.

Chemical energy Heat

Milling Oxygen Wood 900 C CO2 Feeding & Pressurization Process heat Slag Entrained flow gasifier 40 bar 1300 C Torrefaction volatiles

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DTU Mechanical Engineering

Biofuel production via therm al gasification

Biomass Gasifier Liquid fuel Synthesis reactor

Biomass

Thank you for your attention

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DTU Mechanical Engineering

extra slides

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DTU Mechanical Engineering

Hurdles to overcom e before biofuel plants are com m ercial

• Cost

– An incentive to use biomass instead of coal is needed

• Subsidy on biomass
• Tax on coal
• Tax on CO2 emission (best option, and also the main hurdle!!)
• Technical

– Up scaling the demonstrated small-scale gasifiers – Using biomass on existing large-scale coal gasifiers

• Environmental

– The biomass used must be sustainable (not replace food/ feed production, net greenhouse gas emissions from land use change, etc.)

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DTU Mechanical Engineering

Biofuel plants Polygeneration

Biomass Gasifier Liquid fuel Synthesis reactor

Biomass

• The total energy efficiency of the

biofuel plant can be increased by co-production of: – Electricity – Heat Fuel Electricity Heat

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DTU Mechanical Engineering

I m portant aspects in the design of BTL plants

Pros Cons Gasification Air Low cost, simple design N2 in syngas ⇒ lower conversion

• f syngas to fuel

Oxygen No N2 in syngas ⇒ higher conversion

• f syngas to fuel

Cost and electricity consumption

• f oxygen plant

Atmospheric Cost of gasifier, simple design High electricity consumption for pressurization of syngas Pressurized Low electricity consumption for pressurization of syngas Cost of gasifier Synthesis Recycle of unconverted syngas (RC) Higher conversion of syngas to fuel Lower electricity co-production Once through synthesis (OT) Higher electricity co-production Lower conversion of syngas to fuel

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DTU Mechanical Engineering

Oxygen WGS reactor Gas cleaning and conditioning 30 C DME reactor Gas-liquid separator 280 C

• 40 C

DME methanol Water H2S, COS Unconverted syngas 60 bar Water CO2 Slag Entrained flow gasifier 40 bar 1300 C 200 C 300 C Biomass Syngas (H2 ,CO) H2 ,CO, CO2, H2O ~CO2

Adjusting the H2/ CO-ratio: CO + H2O → CO2 + H2 DME: 3CO + 3H2 → CH3OCH3 + CO2 Methanol: CO + 2H2 → CH3OH

The processes in a biofuel plant

Generic biofuel plant (DME) showing the important processes

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DTU Mechanical Engineering

Gasifier types

Fixed bed gasifier Fluidized bed gasifier Entrained flow gasifier – Updraft – Downdraft

Sand + biomass particles

Updraft