Proceedings - Biomass South 2008
Tom Johnson, Southern Company Services
Tom Johnson has over 30 years experience in Southern Company’s Research and Environmental Affairs Department. During his career he has been Project Manager on several alternative fuel development efforts. He has directed projects on direct coal liquefaction, coal gasification, and advanced coal cleaning. Most recently, he has been responsible for managing Southern Company’s Renewable Energy Technology Program, including evaluation of the use of biomass for power generation in existing and future plants. Mr. Johnson holds a Bachelor of Chemical Engineering degree from Auburn University and is a member of the American Institute of Chemical Engineers.
Biomass Power: Co-firing
The presentation will describe Southern Company’s experience with biomass co-firing in selected pulverized coal units. Major results will be discussed with particular regard to impacts on pulverized coal boiler fuel handling, feeding, boiler efficiency, emissions, and economics. Southern Company has also initiated a study to examine the feasibility of generating electricity from 100 percent biomass, in contrast to co-firing. The overall goal is to learn if this process can generate power on a cost-effective basis. Preliminary study results will be discussed.
Notes:
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Direct injection and co-milling
- Advantages – lower capital costs, emissions reductions from coal
- Disadvantages – lower energy density, compatibility with existing technology
- Switchgrass, sawdust, woodchip, and small wood chips (1/2” or less)
- Chopped switchgrass greater volume/Gtu than green chips
- Switchgrass bales into tub grinder to boiler – 5-10% energy into range direct injection
- Plant cadsden 0 co-firing sawdust no problems, 1-2” chips (pulp & paper size) clogged system move to small wood chips (precision husky) ½” worked well
- Found grind only to get the chips right, regrinds resulted in clumps
- Mixing occurred in bunker
- Issues to address effect of biomass on NOx
- Current ASTM specs exclude ash-coal and biomass ash from cement
- Old rate switchgrass $60/ton
- 50~100 miles plant material radius
Key Quotes
- “It depends on price and price only, renewable aside.”
Summary
- Direct injection of switchgrass into coal facilities works, need to know when and where to inject in system
- Co-firing of sawdust and small less than ½” wood chips worked through system
- Co-firing standard pulp & paper wood chip size plugged system if you try to regrind chips material clumped together
- Direct injection requires more infrastructure, but enables larger biomass energy percentages
Thanks to Sarah Ashton, Rachel Cook, Lindsey Hannum, James Jeuck, Liwei Lin, James McCarter, Susan McIntyre, and Mark Megalos for providing notes and summaries for presentations.
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