environmental profiles of gasification technologies … · environmental profiles of gasification...
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ENVIRONMENTAL PROFILES OF GASIFICATION TECHNOLOGIES
GTC REGULATORY WORKSHOPGTC REGULATORY WORKSHOP
April 25, 2012
Steve Jenkins
Topics
•Air emissions
•Water consumption and wastewater discharges
• Solid and other byproducts
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• Solid and other byproducts
Large-scale Coal/Pet Coke Gasification Plants
Southeast Idaho
Energy- Fertilizer
Duke Energy
Edwardsport IGCC
Hydrogen
Energy – IGCC
Wabash River
IGCC
Taylorville Energy
Center IGCC
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Energy – IGCC
and Fertilizer
Texas Clean
Energy Project-
IGCC &
Fertilizer
Mississippi
Gasification -
SNG
TECO – Polk
Power Station
IGCC
Eastman
Chemical -
chemicals
Indiana
Gasification - SNG
Mississippi
Power Co.
Kemper County
IGCC
Kentucky NewGas -
SNG
Cash Creek IGCC
Coffeyville
Resources -
Fertilizer
Lake Charles
Gasification-
Methanol
Biomass and MSW Gasification Plants
Taylor Biomass
Energy –
Biomass/MSW to
Power
Oak Ridge
National Labs –
biomass to steam
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Enerkem Pontotoc
– MSW to Alcohols
Univ of South
Carolina – biomass
to power/steam
MaxWest –
biosolids
drying/thermal
energy
BFC Gas & Electric
– biomass to
power
Plasco Energy –
Univ Northern BC
– biomass to
central heating
Biomass and MSW Gasification Plants
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Univ of British
Columbia –
biomass to
power/CHP
Enerkem – MSW
to alcohols
Plasco Energy –
MSW to Power
Overall Environmental Profile for Gasification Facilities
•From Gasification 101, you learned that:
– Gasification is very different from combustion
– Contaminants are typically removed prior to combustion or downstream use for conversion to fuels, chemicals, fertilizers
– Gasification systems can have significantly lower water use
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– Gasification systems can have significantly lower water use than combustion-based systems
– By-products can be commercially saleable
– CO2 can be more easily captured for use than with combustion-based systems
•Overall smaller/cleaner environmental profile
Air Emission Points Large-scale Gasification Plants
•Unique emission points depend on technology and technology provider
– Coal or biomass dryer vents
– Gasifier startup stacks
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– Gas turbine exhaust stack
– Flare
– Sulfur Recovery Unit tail gas thermal oxidizer
– Sulfuric Acid Plant stack
– CO2 vent stack
Mercury Removal from Syngas
•Pre-sulfided activated carbon beds
•>94% removal of vapor-phase mercury proven at Eastman Chemical
•Typical design basis for new gasification
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•Typical design basis for new gasification plants
Source: Eastman Chemical
Sulfur Removal Process
•Gasification occurs in an oxygen-starved
environment
• Sulfur in the feedstock is converted to H2S,
not SO2
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not SO2
– Sulfur compounds are removed by refinery industry
technologies to levels ≥99%
– Recovered as molten sulfur or sulfuric acid by-product
Source: Linde
NOx Reduction (IGCC Gas Turbines)
•Controlled by moisturizing the syngas and diluting the syngas with N2
– cools the flame and reduces thermal NOx
•Gas turbines use diffusion burners vs. the
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•Gas turbines use diffusion burners vs. the dry low NOx (DLN) burners used with natural gas
• Selective Catalytic Reduction (SCR) may be an option for additional NOx reduction
Source: Siemens Energy
Diffusion Burner
DLN Burner
Water Consumption
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Water Consumption – Major Users
• Water requirement for slurry-feed gasifiers to
produce slurry of about 65% solids that is
pumped to the gasifier
• Syngas coolers have pure water needs for
producing steam
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producing steam
• Water required for water shift reaction to
convert CO to CO2
• HRSG/steam turbine requires purified water
• Cooling tower makeup
•For an IGCC plant:
– 2/3 of the power generation is from the gas turbine-generators, and only 1/3 from the steam turbine-generator
– Condenser cooling water make-up needs are decreased by ~2/3 compared to a coal-fired plant, where all of the power
Water Consumption for IGCC Plants
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~2/3 compared to a coal-fired plant, where all of the power generation is from the steam turbine-generator
Wastewater Discharges
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Wastewater Production –Sources of Contaminants
•Ash in the feedstock
•Chlorides in the raw water and feedstock
• Sulfur in the feedstock
•Compounds formed in the gasification process
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•Compounds formed in the gasification process
– Ammonia
– Sulfides
– Formates
Water and Wastewater Discharges
•Gasification plant designs include significant re-use and recycling of process streams
•Dry ash removal systems help to reduce need for wastewater treatment systems
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•Zero liquid discharge systems are common design basis
– Vapor recompression systems
– Evaporator-crystallizers
– Output is a brine cake for disposal
Solid Byproducts
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•Ash is removed in molten form, then quench-cooled to form glassy, inert slag
Ash and Slag
Molten slag
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Slag Use
•Used for making
– Cement
– Asphalt filler
– Roofing shingles
– Sand-blasting grit
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– Sand-blasting grit
Other Commercial Byproducts
• Sulfur
– Recovered in molten form
– Transported by rail or truck
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• Sulfuric acid
– Various concentrations can be produced, depending on local markets
– Transported by rail or truck
Biomass/MSW Gasification
•Wide range of feedstocks
•Environmental advantages over biomass combustion:
– Concentrates ash contaminants in the gasifier, so that the boiler, recip engine
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gasifier, so that the boiler, recip engine or gas turbine burns syngas, not the biomass
– Ash/slag can be a usable by-product
Gasification vs. Incineration
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Mass-burn Incineration
• Incineration literally means to render to ash
– Incineration uses MSW as a fuel
– It burns with large amounts of air to form heat and CO2
– Hot gases are used to make steam, which is then used to generate electricity
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generate electricity
– Emissions can only be removed after combustion
MSW Gasification
•MSW is not a fuel, but a feedstock for the gasification process
•The MSW itself is not combusted
•Gasification converts MSW to a usable syngas
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•Gasification converts MSW to a usable syngas
– The MSW reacts with little or no oxygen and is converted to syngas
– The syngas (not the MSW) can be combusted
– Or the syngas can be used to make higher valuable commercial products such as transportation fuels, chemicals, and fertilizers
MSW Gasification
•Gasification does not compete with recycling, it actually enhances it
• Metals and glass are removed from the waste stream prior to being sent into the gasification process
• Many plastics and cardboard boxes cannot by recycled, and
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• Many plastics and cardboard boxes cannot by recycled, and would otherwise end up in a landfill
– They make excellent high energy feedstocks for gasification, reducing the amount that would end up in a landfill
Dioxins and Furans
• Large organic molecules (like plastics) are decomposed into syngas in the high temperatures of a gasifier
• Dioxins/furans need sufficient oxygen to form, and the atmosphere in a gasifier does not provide the environment needed for that to occur
• Dioxins need fine metal particulates in the gas to reform; syngas from gasification is typically cleaned of particulates before being used
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gasification is typically cleaned of particulates before being used
• When syngas is used to produce fuels, chemicals and fertilizers, the syngas is quickly quenched, so that there is not sufficient residence time in the temperature range where dioxins/furans could re-form
• When the syngas is primarily used as a fuel for making heat, it can be cleaned as necessary before combustion; this cannot occur in incineration, which requires post-combustion clean-up
Summary of Environmental Profile
•Lower air emissions and water consumption than other forms of coal-based energy production
•Recycling of process streams/zero liquid discharge
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•Commercially usable by-products
•Biomass gasification provides process and environmental advantages over combustion
•MSW gasification has many environmental advantages over mass-burn incineration
Questions??
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