Biomass Utilization in Cofiring Scenarios with a Gas Turbine Integrated Combined Cycle System

There are several ways to utilize biomass in a cofiring scenario with a gas turbine combined cycle system that uses natural gas as the primary fuel to generate power. In light of the current market conditions (i.e., low natural gas prices, utility deregulation, etc.), biomass cofiring projects are the best opportunity for near-term growth in biomass utilization for power generation. Despitebiomass being a very different fuel in may respects, it is a logical choice for cofiring in a natural gas combined cycle system for several reasons. Electricity generation from natural gas in combustion turbines and combined cycle plants is expected to increase significantly during the next 15 years. Many factors will contribute to this increase such as the low cost of natural gas, the fact thatit is a cleaner burning fuel than coal or oil, and the incremental increases in efficiency and power output from gas turbines. Also, gas fired units have a lower initial capital cost and a shorter construction time than other electricity generating systems. In addition to its potential environmental benefits, biomass may, in select cases, offer fuel flexibility or a supplemental low-cost fuelfor use in a gas turbine combined cycle system. Many opportunities exist for developing a biomass/natural gas cofiring system such as repowering an existing coal boiler, retrofitting an existing power plant, or constructing a new power plant. A detailed site specific analysis for any of the biomass/natural gas coprocessing schemes should be performed to determine the economics at a givenlocation because each electricity generating system has unique considerations. The effects of system modifications and changes in operating parameters on the overall system performance should be examined including a comparison of design and off design performance for part load operation. The unique concept of a biomass/natural gas combined cycle system has not been examined extensively by othersso several conceptual power plant configurations were developed that integrate biomass technologies in the form of combustors, boilers, and gasifiers with natural gas-fired gas turbines. A discussion and an evaluation of systems employing these three biomass technologies is presented as well as advantages, disadvantages, and application for each biomass/natural gas combined cycle system.