Southern Company Biomass Cofiring Research

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Southern Company Biomass Co-firing Research
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Southern Company Participants
Doug Boylan Steve Wilson Southern
Company Bill Zemo Alabama Power Kathy
Russell Georgia Power
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Switchgrass Co-firingSponsors and Participants

• Southern Company
• Auburn University
• EPRI
• Southern Research Institute
• Wilson Farms
• Sunbelt Expo
• U.S. DOE
• McBurney

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Plant StaffGadsden and Mitchell
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Biomass Co-firing Technologies

• Co-milling - mix biomass with coal and introduce
  into the furnace through the coal handling system
• Simple procedure
• Reduced capital cost
• Reduced transport cost
• Considerable system experience

• Direct injection - introduce ground biomass
  pneumatically into the furnace through dedicated
  burners
• Higher co-firing percentages
• Direct biomass control

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Co-Milling Switchgrass and Coal

• Coal does not flow when mixed with low
  percentages of grass

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Pellet Co-firing Potential Advantages

• Improved efficiency
• Reduced plant capital
• Reduced transportation
• Reduced labor
• Reduced dust

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Cubing Setup - Switchgrass farm in Lincoln, AL
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• Cubes sensitive to
• Moisture
• Binder type and percentage
• Grass type and rate

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Mitchell Cube Combustion

• One week of testing completed
• Cubes handle and burn fairly well
• Serious bunker issues Rat-holing

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Switchgrass Co-firing Schematic
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Gadsden Co-Firing Facilities
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Gadsden Co-Firing Facilities
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Switchgrass Co-firing and Boiler Efficiency
(Full Load - 7 by heat input)
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Cement and Ash Tests

• ASTM specifications exclude biomass ash with coal
  ash for cement
• Conducted tests with University of Alabama in
  Birmingham to evaluate effect of wood ash on
  cement properties
• Coordinating efforts with ASTM

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SCR Catalyst Effects

• SCR (Selective Catalytic Reduction) is NOx
  emission control device
• Catalyst is affected by biomass ash
• Pilot study at Plant Gadsden with EPRI

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Grass Co-Firing Energy CostPresent
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Grass Co-Firing Energy CostFuture
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Conclusions

• Direct injection with grass was technicalsuccess
• Co-firing reduced emissions,but was a little
  less efficient
• Cubes have problems
• Grass co-firing cost predictions were
  about2.6/kWh to 3.0/kWh higher than coal power
• Results suggest a subsidy will be required to
  make grass co-firing viable for an RPS
• Biomass cannot be co-fired at some units for
  technical and cost reasons at this time
• Research is on-going at Southern Company to
  address these issues

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Questions?