Combination of coal-to-liquid plants with renewable ... · Folie 14 © Fraunhofer UMSICHT...

Folie 2 © Fraunhofer UMSICHT

Combination of coal-to-liquid plants with renewable hydrogen – electricity grid stabilization and efficient liquid storage

Tim Schulzke, Group Manager Thermochemical Processes and Hydrocarbons Dr. Christoph Unger, Think Tank Energy

© Fraunhofer

Outline

1. Coal Gasification to produce Gases or Liquids (CtG / CtL)

2. Fundamentals of Power-to-Liquids Technologies (PtL)

3. Synergies from the Combination of Synthesis Chemistry and PtL

4. Future Research Demand

5. Outlook

6. Summary

© Fraunhofer

Outline





5. Outlook

6. Summary


General applications for synthesis gas from lignite

lignite

gaseous fuel

thermal processes like ovens / kilns for calcination, dryling, melting, s intering etc.)

gas fired (steam) boilers

power generation with gas engines or gas turbines

incre

asin

g d

em

an

d o

n g

as u

pg

rad

ing

gasification solid fuel gas utilization / application

power generation with fuel cells

Syntheses (SNG or BtL) Impurities: dust, tars, sulfur, chlorine, …


Synthesis reactions

Methane CO + 3 H2 ⇄ CH4 + H2O RH=-206 kJ/mol (3:1)

Fischer-Tropsch-Synthesis n CO + 2n H2 ⇄ (-CH2-)n + n H2O RH=-158 kJ/mol (2:1)

Methanol CO + 2 H2 ⇄ CH3OH RH=-98,7 kJ/mol (2:1)

Ethanol 2 CO + 4 H2 ⇄ C2H5OH + H2O RH=-256 kJ/mol (2:1)

Dimethyl Ether 2 CO + 4 H2 ⇄ H3C-O-CH3 +H2O RH=-219 kJ/mol (2:1)

Methane 2 CO + 2 H2 ⇄ CH4 + CO2 RH=-247 kJ/mol (1:1)

Ethanol 3 CO + 3 H2 ⇄ C2H5OH + CO2 RH=-297 kJ/mol (1:1)

Dimethyl Ether 3 CO + 3 H2 ⇄ H3C-O-CH3 + CO2 RH=-258 kJ/mol (1:1)

H2/CO-ratio in coal gasification: 1:2

(H2/CO)


Exemplary process scheme: methanol

Air Separation Unit

Gasifier

Gas Conditioning

Gas Cleaning

Methanol Reactor

Product Separation

Methanol Storage

Lignite

O2

CH3OH

Ele

ctr

icity G

rid

Pel

CO2

N2

Air

CO2

© Fraunhofer

Outline





5. Outlook

6. Summary


Forecast of Surplus Renewable Power in Germany


Power-to-Liquids as negative controlling power fundamental challenges for Power-to-Liquids (PtL)

finding suitable CO2-sources

production from ambient air is possible, but very energy consuming

coal fired power stations with flue gas scrubbing (carbon capture)

anaerobic digestors (biogas plants) with upgrading to SNG

additional challenges for PtL as negative controlling power

CO2 at coal fired power stations not available in times with surplus electricity alternating operation of power station and PtL-plant

Synthesis reactor needs control range of 0 – 100 % today main difficulty either long start-up period (only long periods with surplus renewable electricity usable) or high energy loss for so-called „hot hold“ in idle mode


Electricity demand and conversion efficiency

Water electrolysis

1 scm H2 needs 4.6 kWhel including losses

Methan synthesis

CO2 + 4 H2 ↔ CH4 + 2 H2O

9.3 kWhel / kg CO2, 363.64 g CH4 / kg CO2 = ̂ Hi=5.05 kWh max = 54.30 %

Methanol synthesis

CO2 + 3 H2 ↔ CH3OH + H2O

7.0 kWhel / kg CO2, 727.27 g CH3OH / kg CO2 = ̂ Hi=4.02 kWh max = 57.43 %

without energetic effort for CO2 supply, without chemical conversion losses!



Methanol Reactor

Product Separation

Methanol Storage

Electrolyzer

O2

H2

CH3OH

Ele

ctr

icity G

rid

Pel

CO2

Water CO2

Option I: CO2 + 3 H2 ↔ CH3OH + H2O

Option II: CO2 + H2 ↔ CO + H2O

CO + 2 H2 ↔ CH3OH

Control Range

0 – 100 %

in Germany: largest installation at biogas plant : 6 MWel

© Fraunhofer

Outline





5. Outlook

6. Summary


Theoretical stoichiometry for synthesis gas products

lignite composition: 66 % C, 5 % H, 28 % O CH0.91O0.318

oxygen gasification (autotherm)

CH0.91O0.318 + 0.6135 O2 ↔ 0.2275 CH4 + 0.7725 CO2 Methan

CH0.91O0.318 + 0.72725 O2 ↔ 0.2275 CH3OH + 0.7725 CO2 Methanol

CH0.91O0.318 + 0.76516 O2 ↔ 0.1516 C2H6O + 0.8483 CO2 Ethanol/DME

steam gasification (allotherm)

CH0.91O0.318 + 0.9696 H2O ↔ 0.7123 CH3OH + 0.2876 CO2

requires external energy supply, in biomass gasification usually by combustion

yields additional CO2 in separate gas stream; good for stand alone CtL-plant

but overall carbon balance remains the same

autothermal gasification with steam moderated temperature control

CH0.91O0.318 + 0.443 O2 + 0.379 H2O ↔ 0.417 CH3OH + 0.583 CO2

_ _ _

_ _ _


Example: Berrenrath HTW-gasifier (demoplant)

Outline data

Capacity: 27 t/h lignite

autothermal steam/oxygen gasification, HT-Winkler-gasifier, 123 MWth

Maximum product quantity: 12.5 t/h Methanol (300 t/d)

Minimum byproduct: 24 t/h CO2 (576 t/d)

Potential

complete conversion of CO2 requires electrolyzer with 168 MWel

complete conversion of CO2 produces 17.5 t/h Methanol (420 t/d)



Air Separation Unit

Gasifier

Gas Conditioning

Gas Cleaning

Methanol Reactor

Product Separation

Methanol Storage

Electrolyzer

O2 Storage

Lignite

O2

O2

O2

H2

CH3OH

Ele

ctr

icity G

rid

Pel

Pel

CO2

Water

N2

Air

CO2

Control Range

50 – 100 %

CtL

PtL

Steam


Air Separation Unit

Gasifier

Gas Conditioning

Gas Cleaning

Methanol Reactor

Product Separation

Methanol Storage

Electrolyzer

O2 Storage

Lignite O2

CH3OH

Ele

ctr

icity G

rid

Pel

CO2

N2

Air

CO2

Nominal Load

50 %

Steam

Operating status: no surplus electricity


Operating status: surplus electricity available

Air Separation Unit

Gasifier

Gas Conditioning

Gas Cleaning

Methanol Reactor

Product Separation

Methanol Storage

Electrolyzer

O2 Storage

Lignite O2

O2

H2

CH3OH

Ele

ctr

icity G

rid

Pel

Pel

CO2

Water

N2

Air

CO2

Load

up to 100 %

Steam


Operating status: increased electricity demand in grid

Air Separation Unit

Gasifier

Gas Conditioning

Gas Cleaning

Methanol Reactor

Product Separation

Methanol Storage

Electrolyzer

O2 Storage

Lignite

O2

O2

CH3OH

Ele

ctr

icity G

rid

Pel

CO2

N2

Air

CO2

Nominal Load

50 %

Steam


Synergies through combination of CtL and PtL

Synergies

costs of PtL are dominated by electrolyzer only slight saving through cheaper reactor volume

omission of a dedicated CO2 supply reduces energy demand increased conversion efficiency of PtL process chain

synthesis reactor for PtL needs no control range from 0 – 100 % substantial improvement of operating control shortened start-up time, thus shorter periods with surplus renewable electricity usable, higher annual operating hours for electrolyzer substantial reduction of idle losses

increase of profitableness of the synthesis plant by use of electrolysis by-product O2

even offering positive controlling power is possible by dedicated derating of air separation unit

increase of carbon efficiency of the synthesis plant during feeding of additional hydrogen

© Fraunhofer

Outline





5. Outlook

6. Summary


Research Demand: Ideal Injection point for Hydrogen

Gas Cleaning

Gas Conditioning

Methanol Reactor

CH3OH

CO2

H2

Reverse Water Gas Shift

CO2+ H2 CO + H2O

O2

Lignite

Steam


Research Demand: Ideal Injection point for Hydrogen

Gas Conditioning

Methanol Reactor

CH3OH

H2

Reverse Water Gas Shift

CO2+ H2 CO + H2O

RWGS Reactor H2

H2

Tar Reforming Sulfur Removal CO2 Removal

CO2

O2

Lignite

Steam


Research Demand

optimal feeding point for additional hydrogen

feeding into freeboard of gasifier partially or completely?

combined with recycle of CO2 as gasifying agent to the gasifier?

reverse water gas shift reactor between gasifier and CO2 removal partially or completely?

feeding into methanol reactor CO2-tolerant catalyst?

© Fraunhofer

Outline





5. Outlook

6. Summary


Outlook

source: JB. Hansen, IEA Bioenergy Conference, Berlin, 2015

PEM / Alkali electrolysis: SOEC (at 500 °C) 4.6 kWh / scm H2 3.2 kWh / scm H2


Outlook

Air Separation Unit

Gasifier

Gas Conditioning

Gas Cleaning

Methanol Reactor

Product Separation

Methanol Storage

Electrolyzer

O2 Storage

Lignite

O2

O2

O2

H2

CH3OH

Ele

ctr

icity G

rid

Pel

Pel

CO2

Water

N2

Air

CO2

Control Range

50 – 100 %

Steam

PEM / Alkali electrolysis: 4.6 kWh / scm H2

SOEC (at 500 °C): 3.2 kWh / scm H2


Outlook

Gasifier

Gas Conditioning

Gas Cleaning

Methanol Reactor

Product Separation

Methanol Storage

SOEC

Lignite

O2

H2

CH3OH

Ele

ctr

icity G

rid

Pel

CO2

Steam CO2

whole system: Control Range 50 – 100 %

Steam

PEM / Alkali electrolysis: 4.6 kWh / scm H2

SOEC (at 500 °C): 3.2 kWh / scm H2

© Fraunhofer

Outline





5. Summary


Summary

Combination of lignite-based synthesis plant with PtL

increases carbon efficiency of synthesis plant

improves operating control of PtL plant

offers controlling power in a scale relevant for transmission grid Example Berrenrath up to 168 MW negative controlling power by electrolyzer ( 4 MW positive controlling power by derating of air separation unit)

research demand identified for development of optimized strategy for hydrogen feeding

with development of SOEC technology and high availability of renewable electricity further efficiency improvement is possible in future


Fraunhofer UMSICHT Department Biorefinery & Biofuels

Фотография: photocase.de

Thank You for Your kind attention!

Contact: Fraunhofer UMSICHT Osterfelder Strasse 3, 46047 Oberhausen, Germany E-Mail: [email protected] Internet: http://www.umsicht.fraunhofer.de/en

Dipl.-Ing. Tim Schulzke Telephone: +49 208 8598 1155 E-Mail: [email protected]

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