BIOMASS CFB GASIFIER CONNECTED TO A 350 MW TH STEAM BOILER FIRED WITH COAL AND NATURAL GAS-THERMIE DEMONSTRATION PROJECT IN LAHTI IN FINLAND

The successful experience in developing the advanced Foster Wheeler Energia Oyʹs (former Ahlstrom Pyropower) Circulating Fluidized Bed combustion system subsequently led to the development of the CFB Gasification Technology in the early 80 s. The driving force for the developing work was the dramatically increase in oil price during the oil crises. The primary advantage of CFB gasification technology is that it enables the substitution of expensive fuels e.g. oil or gas with cheap solid fuels. These cheap fuels are typically different types of waste woods, bark or other biofuels. In the CFB gasifier these solid fuels are converted to gaseous fuel which can be used instead of other expensive fuels. In some cases this also solves a waste disposal problem, providing a secondary economic and environmental benefit. Foster Wheeler Energia Oy has supplied four commercial scale atmospheric CFB gasifiers in the mid 80 s to the pulp and paper industry with capacities from 17-35 MW based on fuel input. These applications utilize waste wood as feedstock and the units are still successfully operational today. Lahden Uimp6voima Oy is a Finnish power company producing power and district heat for the city of Lahti. The company is 50% owned by the city of Lahti and 50% by Imatran Voima Oy, which is the largest utility power company in Finland. Lahden Liimp6voima Oy operates the Kymijiirvi power plant locating nearby the city of Lahti in Southern Finland. To keep the energy prices as low as possible, Lahden Liimp6voima is continuously looking for the most economical fuel sources, and simultaneously, trying to improve the environmental acceptability of the energy production. At the moment, about 300 GWh/a different type of biofuels and refuse fuels are available in the Lahti area. On an annual basis, the available amount of biofuels and refuse fuels is enough to substitute for about 15% of the fuels burned in the main boiler equaling max 30% of coal. The aim in this Lahden Liimp6voima Oyʹs Kymijiirvi power plant gasification project is to demonstrate the direct gasification of wet biofuel and the use of hot, raw and very low-calorific gas directly in the existing coal-fired boiler. The gasification of biofuels and co-combustion of gases in the existing coal-fired boiler offers many advantages such as: recycling of CO2, decreased SOz and NO, emissions, efficient way to utilize biofuels and recycled refuse fuels, low investment and operation costs, and utilization of the existing power plant capacity. Furthermore, only small modifications are required in the boiler, possible disturbances in the gasifier do not shut down the power plant.