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Combining coal and renewables
Dr Stephen Mills
IEA Clean Coal Centre,
London
International Power Summit, Munich,
19-21 February 2014
Introduction and content
• Introduction and background
• Reasons for coupling coal use with REs
• Growing level of renewables and their impacts
(with particular emphasis on biomass and wind)
• Gasification and co-gasification
• Hybrid energy-producing schemes
• Summary
Global energy demand and supply
Coal will still be used widely
• biggest use now is for
electricity generation
By 2040, world population of ~9 billion
Global energy demand 30% higher than now
Largest individual proven national coal
reserves (Mt)
electricity generation
(42% of world’s electricity)
• provides >30% of global
primary energy
• global coal consumption has
increased for 12 successive
years
• production has soared in some
non-OECD countries
0
50,000
100,000
150,000
200,000
250,000
Global increase in renewable energy
Wind:
• latest additions of ~45 GW/y
• global wind capacity now >280 GW
• around 70 countries have >10 MW of
capacity
• ten biggest players = 87% of total
capacity
• includes China, the USA, India,
Germany, UK, Canada
Biomass:
• can take many forms
• uptake for energy production
increasing in many countries
• often environmental and economic
considerations
• frequently supported by incentives
0
200
400
600
800
Mtoe
EU 27 gross energy consumption
Why the growth in renewable energies?
• depletion of energy resources
• diversification of sources
• possible climate change linked to the use of
fossil fuels
Perceived advantages of VREs
• capital costs high, but operating costs may be low
• ‘fuel’ costs may be negligible or even zero
• no pollutant emissions from day-to-day operation
• similarly, no direct CO2 emissions
The rise of intermittent renewables
• the use of such technologies will
increase further - particularly wind
and solar power
• increasingly, they will form part of
networks or grids that also include
thermal plants (coal and gas)thermal plants (coal and gas)
• because they operate in a different
manner, their variable output can
have a number of impacts on thermal
plants
Impacts on other power plants
When input from renewables is high, thermal
stations may be expected to operate at part load
or cycle
Hard coal Lignite Natural gas
Energy production using combinations
of coal and renewables
mmm
Wind power
• Forest residues
� thinning operations
� logging
� fire prevention
� downstream processing
Biomass
Various ways to combine the use of coal, biomass
and intermittent renewables have been proposed
� downstream processing
• Energy crops
Advantages and disadvantages
of biomass use
Pros:
• use unwanted wastes
• minimises landfill
• reduce fossil fuel use
• extend life of fossil fuel reserves
• reduce conventional emissions
• reduce CO2
Cons:
• can be expensive to harvest and produce
• may tie up land and other resources
• seasonal limitations
• some residues retained in situ for ecological reasons
• low CV - may need large amounts
• physical properties – grinding, pulverising
• chemical properties (alkalis, chlorine)
The World’s forests
Where and how much?(1000 ha)
• Africa 675,000
• Asia 593,000
• Europe 1,005,000
• Americas 1,570,000
Total >4,000,000
Top five most forested countries:
Russian Federation > Brazil > Canada > USA > China
Gasification
• versatile and well proven for power generation,
chemicals, fuels, and fertilisers
• virtually any carbon-based material can be
gasified
• coal most widely used; but also some biomass• coal most widely used; but also some biomass
• different gasifiers - many variants available:
� entrained flow
� fluidised bed
� fixed bed systems
Coal and biomass gasifiers
Typical biomass gasifiers much smaller than coal
Coal Biomass
2500 - 15,000 t/d 25 - 200 t/d
Air- or oxygen-
blown
Mainly air-blown
Great Plains, USA JY biomass gasifier, China
Coal/biomass co-gasification
Advantages
Coal Biomass Co-gasification
High energy content May be low cost waste or
residue
Large coal gasifiers – economies of scale
- high efficiency, better economics
Widely available Lower emissions Allows biomass access to well-
established processes
Large reserves High availability in some
countries
Smooths out seasonal biomass
availability
Less prone to price
fluctuations
Reduces impacts of variations in biomass
properties
Usually costs less than Reduces coal plant emissions; possibly Usually costs less than
biomass
Reduces coal plant emissions; possibly
credits for the use of renewable fuel
Well proven in large-
scale processes
Some biomass catalyses coal reactions;
synergetic effects observed
Disadvantages
Production-related
impacts
Lower energy content Storing, feeding, blending arrangements
may be more complex
Conventional pollutant
emissions
Variable properties
CO2 emissions Harvesting, transport and
pre-treatment costs
Seasonal availability
Tar, alkali issues
Co-gasification projects
IGCC power plants
Plant Capacity (MWe) Gasifier Biomass used
Buggenum,
Netherlands
284 Shell Dried sewage sludge, chicken litter,
sawdust
ELCOGAS,
Spain
335 Krupps-
Koppers
PRENFLO
Olive wastes, almond shells, waste wood,
vineyard wastes, MBM
Polk plant, USA 250 GE Bahia grass, eucalyptus
Chemicals production
Berrenrath, Methanol HTW fluidised MSW, dried sewage sludge, loaded cokesBerrenrath,
Germany
Methanol HTW fluidised
bed
MSW, dried sewage sludge, loaded cokes
Schwarze
Pumpe,
Germany
Methanol Combination
of BGL, FDV,
GSP
Demolition wood, sewage sludge,
plastics, MSW
Sasol, S. Africa Various Sasol-Lurgi Bark, wood pulp/bark
ZAK + PKE,
Poland
300 MWe + MeOH,
chemicals
na na
Combined gasification and renewable
energy concepts
Organisation Technologies proposed Status
NREL, USA Gasification/
co-gasification +
electrolysis (wind)
Various studies under way. Concepts include:
• combining wind power and biomass gasification
• combining biomass gasification and electrolysis
• combining coal and biomass co-gasification
Several gasification-based hybrid systems being examined
NETL, USA Coal gasification +
electrolysis (wind)
Systems to produce SNG, electricity and biodiesel.
3000 t/d plant proposed.
Unconverted coal from gasifier fed to oxy-combustor
CRL Energy,
New
Zealand
Coal/biomass
co-gasification +
electrolysis (wind)
Syngas could be used to produce low-carbon FT chemicals, synfuels
Oxygen from electrolysis fed to gasifierZealand electrolysis (wind)
Oxygen from electrolysis fed to gasifier
Hydrogen - enrich product gas, stored, transport fuel, fuel cells
Leighty
Foundn, USA
Coal/bio. co-gasification
+ electrolysis (wind)
Oxygen from electrolysis fed to gasifier
Univ. Lund,
Sweden
Biomass (wood) gasifier
+ electrolysis (wind)
Oxygen from electrolysis fed to gasifier
Elsam/DONG
Denmark
Biomass gasification +
electrolysis (wind, solar)
Various co-generation concepts to produce power, heat, transport
fuels examined.
Hydrogen added to syngas. Oxygen for biomass gasification
Lausanne,
Switzerland
Wood gasification +
electrolysis
Several processes examined for SNG production
China Various: Gasification +
electrolysis (wind)
Oxygen from electrolysis fed to gasifier.
Hydrogen fed to syngas.
Mainly for SNG, methanol, ethylene glycol production
Water electrolysis
Electrolysis is a means for separating water into gaseous hydrogen and oxygen
Only inputs are feed water and low voltage direct current
Hydrogen and oxygen production by
water electrolysis
Several different types of electrolyser are available commercially:
• proton exchange or polymer electrolyte membrane (PEM) electrolysers
• alkaline electrolysers
• solid oxide electrolysers
• electrolyser efficiencies between 56 and 73%, but RD&D is
improving this;
• electricity supply from any source but to be viable, must be • electricity supply from any source but to be viable, must be
low cost;
• despite intermittent output, wind currently the lowest-cost
renewable.
Several factors determine the cost of hydrogen and oxygen:
• capital cost of the electrolysis plant
• its overall efficiency
• the cost of the electricity input
Large scale electrolysis
Examples of commercial scale electrolysis facilities
NEL Hydrogen Technologies
Lurgi electrolyser
Possible uses for gases produced
Hydrogen
Syngas Fuel cells Transport fuel Gas turbines
Hydrogen
Oxygen
Industrial applications Coal/biomass gasifier Oxyfuel combustion
Hybrid systems incorporating renewables
USA Several studies of hybrid systems for SNG, electricity, transport fuels.
Includes gasification and electrolysis, and coal/biomass co-gasification
with CCS
Denmark REtrol Vision (REnewable energy + petrol) - cogeneration + transport fuels.
Biomass gasification, electricity from renewables, water electrolysis,
+ CO2 from post-combustion capture
Sweden Biomass gasification + wind power. Oxygen from electrolysis fed to gasifier
Examples of studies – based on coal, biomass, coal + biomass
Sweden Biomass gasification + wind power. Oxygen from electrolysis fed to gasifier
New
Zealand
CRL Energy – coal/biomass co-gasification + wind energy for electrolysis.
Oxygen fed to gasifier; hydrogen to enrich syngas.
Production of FT liquids and other products
China Various studies combining coal gasification + renewables.
Wind energy for electrolysis. Oxygen fed to gasifier.
Hydrogen used to enrich syngas. Syngas used for methanol production
Switzer-
land
Biomass gasification + electrolysis. Oxygen fed to gasifer.
Hydrogen used to enrich SNG then fed into natural gas grid
Germany RWE Power-to-gas project (Niederaussem) will couple wind electricity,
Siemens PEM electrolyser, CO2 from power plant flue gas, to produce SNG
APS demonstration plant, New Mexico, USA
• H2 and O2 from wind-
powered electrolysis
• H2 to gasify >3000 t/d of
coal
• produces SNG, fed to grid • produces SNG, fed to grid
or power plant
• unconverted coal fed to
oxygen combustor to
generate 41 MWe
• 90% CO2 capture from
power production - fed to
an algae farm for
biodiesel production
Summary 1
• many schemes proposed, but fossil fuels will remain vital
- combine these with renewables such as biomass and wind
Growing global population and rapidly rising energy demand
Incentives to develop novel energy-producing systems
- combine these with renewables such as biomass and wind
• each individual power source has its own pros and cons
- but combining these may overcome many shortcomings
• to be a runner, systems need to be practical, economically
viable, and environmentally benign
Summary 2
Gasification • both coal and biomass gasified individually
• many technology variants available for each
Coal/biomass
co-gasfn.
• can provide advantages; overcome some problems
• can be environmentally and economically beneficial
• possibilities for producing a range of different products
(SNG, chemicals, transport fuels)
• a number of routes being pursued
Gasification
+ renewables
combinations
• examined some of the more promising concepts being
developed
• particular emphasis on co-gasification coupled with wind-
powered electrolysis (H , O )powered electrolysis (H2, O2)
• many projects still at early stage in their development
• some propose to incorporate CCS
Co-gasification + renewables
Some further advanced - some parts well established (co-gas) – other parts
being trialled (commercial demo of H2 production from wind, and advanced
electrolysers).
If economics can be made to work, several concepts that combine coal,
biomass and intermittent renewables look promising.
Thank you for your attention
Dr Stephen Mills
IEA Clean Coal Centre, LondonIEA Clean Coal Centre, London
Email: [email protected]