201802_Renewable Energy

20/24

A.T. Biopower Co., Ltd,Thai SPP Uses CENTUM CS 3000 to Improve Efficiency of Biomass Power PlantExecutive SummaryIn 2005, A.T. Biopower Co., Ltd. built a biomass power plant in Pichit, Thailand. Using ground rice husks as its fuel, this plant generates 22.5 MW of electricity, of which 20 MW is sold to the Electricity Generating Authority of Thailand (EGAT). The plant was built with the support of the Thai government’s Ministry of Energy, which is promoting the construction of power plants by small power producers (SPP) that utilize hydro, biomass, or thermal cogeneration technology. In addition to promoting the use of renewable energy sources, this policy aims to reduce the country’s dependence on imported fuel. At present, about 90% of the electricity generated in Thailand comes from power plants that rely on non-renewable fossil fuels, namely, oil, coal, and natural gas. If no effort is made to find and develop new energy sources, it is estimated that the country’s coal and natural gas reserves will be completely exhausted in the next 30 years. The use of modern technology to generate power from rice husks and other kinds of agricultural waste will not only contribute to the country’s energy independence, but will also help reduce environmental pollution and provide employment opportunities for the local community. For A.T. Biopower’s biomass cogeneration power plant, Yokogawa Thailand successfully installed the CENTUM CS 3000 production control system, field instruments, and a continuous emission monitoring system (CEMS).The Challenges and the SolutionsStable combustion controlThe burning of the ground rice husks in the boiler’s furnace chamber is a complex process that must be carefully controlled. Fuel oil-fired burners heat the combustion chamber. Once this chamber reaches 700-800 degree C, ground rice husks are fed from a service silo to a fuel-air mixing system, where this mixture is compressed by air from a primary service fan and blown through the burners into the center of the combustion chamber. Adjustable vanes on the burners circulate the fuel-air mixture to maintain optimum combustion at 800-900 degree C. At the same time, compressed outside air that has been drawn in by a forced draft fan and heated in an economizer is directed into the lower part of the combustion chamber in order to keep the ground rice husks in a suspended state and ensure complete combustion. Once the ground rice husks are burning steadily, the supply of fuel oil to the burners is gradually reduced and then stopped completely. With the pressure inside the combustion chamber in balance with the outflowing flue gases, the heat from the flue gas generates 480 degree C steam that drives the steam turbine. The flue gases are then released through the economizer to recover the remaining heat. Steam from that has passed through the turbine is cooled down by a condenser as a condensate. This condensate is transported as drops of water back to the boiler to be recycled as steam. Meanwhile, the heated cooling water that was used to condense the steam is cooled down in a cooling tower for reuse. This system is thus a closed-circuit type cooling system.Plant InformationLocation: Pichit Province, ThailandCapacity: 22.5 MWFuel: Rice husksCompletion: 200517Success Story CollectionRenewable EnergyBiomass