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In 2001, the Gas Technology Institute (GTI) entered into Cooperative Agreement DE-FC26-01NT41108 with the U.S. Department of Energy (DOE) for an Agenda 2020 project to develop an advanced biomass gasification-based power generation system for near-term deployment in the Forest Products Industry (FPI). The advanced power system combines three advanced components, including biomass gasification, 3-stage stoker-fired combustion for biomass conversion, and externally recuperated gas turbines (ERGTs) for power generation. The primary performance goals for the advanced power system are to provide increased self-generated power production for the mill and to increase wastewood utilization while decreasing fossil fuel use. Additional goals are to reduce boiler NOx and CO{sub 2} emissions. The current study was conducted to determine the technical and economic feasibility of an Advanced Power Generation System capable of meeting these goals so that a capital investment decision can be made regarding its implementation at a paper mill demonstration site in DeRidder, LA. Preliminary designs and cost estimates were developed for all major equipment, boiler modifications and balance of plant requirements including all utilities required for the project. A three-step implementation plan was developed to reduce technology risk. The plant design was found to meet the primary objectives of the project for increased bark utilization, decreased fossil fuel use, and increased self-generated power in the mill. Bark utilization for the modified plant is significantly higher (90-130%) than current operation compared to the 50% design goal. For equivalent steam production, the total gas usage for the fully implemented plant is 29% lower than current operation. While the current average steam production from No.2 Boiler is about 213,000 lb/h, the total steam production from the modified plant is 379,000 lb/h. This steam production increase will be accomplished at a grate heat release rate (GHRR) equal to the original boiler design. Boiler efficiencies (cogeneration-steam plus air) is increased from the original design value of 70% to 78.9% due to a combination of improved burnout, operation with lower excess air, and drier fuel. For the fully implemented plant, the thermal efficiency of fuel to electricity conversion is 79.8% in the cogeneration mode, 5% above the design goal. Finally, self-generated electricity will be increased from the 10.8 MW currently attributable to No.2 Boiler to 46.7MW, an increase of 332%. Environmental benefits derived from the system include a reduction in NOx emissions from the boiler of about 30-50% (90-130 tons/year) through syngas reburning, improved carbon burnout and lower excess air. This does not count NOx reduction that may be associated with replacement of purchased electricity. The project would reduce CO{sub 2} emissions from the generation of electricity to meet the mill's power requirements, including 50,000 tons/yr from a net reduction in gas usage in the mill and an additional 410,000 tons/yr reduction in CO{sub 2} emissions due to a 34 MW reduction of purchased electricity. The total CO{sub 2} reduction amounts to about 33% of the CO{sub 2} currently generated to meet the mills electricity requirement. The overall conclusion of the study is that while significant engineering challenges are presented by the proposed system, they can be met with operationally acceptable and cost effective solutions. The benefits of the system can be realized in an economic manner, with a simple payback period on the order of 6 years. The results of the study are applicable to many paper mills in the U.S. firing woodwastes and other solid fuels for steam and power production. |
