The Foster Wheeler biomass gasification experience

The successful development of the advanced Foster Wheeler Circulating Fluidized Bed combustion system subsequently led to the development of the CFB, Gasification Technology in the early 80s. The driving force, at that time, was the substitution of the high priced oil and Gas with lower cost biomass fuels. Today, the strong emphasis on CO2 reduction and the renewable energy obligation have opened a new market for the gasification technology. Foster Wheeler Energia Oy from Finland has supplied six commercial-scale atmospheric Fluid bed gasifiers with capacities from 15 to 70 MWth based on fuel input. Additionally Foster Wheeler Energia Oy has one 50 MW CFB gasifier project in Belgium in delivery. These plants utilize biomass and in one case recycled wastes as feedstock. All of the old units are in successful operation today. The experience of most recent units Lahden Lampovoima and Corenso Oy is presented in this paper. Lahden Lampovoima Oy (LLV) is a Finnish power company producing power and district heat for the city of Lahti. The LLV 70 MW CFB gasifier started its operation in 1998 and it demonstrated in commercial scale the direct gasification of non-dried biomasses co-fired with 40% recycled fuel (REF). The hot, raw and low calorific syngas gas is directly fired in the existing coal fired boiler, substituting about 15 % of fuels burned in the PC boiler. The unit for Corenso Oy, Varkaus, Finland, is gasifying the reject from a liquid packaging board recycling facility. The board contains thin layers of plastic and aluminum that are enriched in the reject. The 40 MWth gasification plant is designed to gasify 18 000 t/a of the plastics and to recover the aluminum, 2100 t/a. Commercial operation was started in autumn 2001. The concept of co-firing biogas in an existing utility boiler, as in the Lahti plant, provides the following main advantages compared to a stand-alone biomass power plant: substantially lower investment costs the specific investment/MWe is much lower for a utility size unit than a small stand alone biomass power plant higher power output / biofuel input a utility cycle efficiency versus a biomass power plant efficiency low operational cost no extra personnel needed; allows for substitution of gas and coal with bio waste fuels The gasification of biomasses, and co-combustion of the syngas in the existing coal-fired boiler also offers such advantages as: the biomass CO2 benefit, decreased SO2 and NOx emissions and an efficient way to utilize local biomasses and recycled refuse fuels. Furthermore, only small modifications are required at the utility boiler, and possible disturbances in the gasifier do not shut down the whole power plant. The experiences from this concept have been excellent. The availability of the plant has been good, and the results, with regard to the product gas quality, gasifier bottom ash, main boiler filter ash, and the emissions after the main boiler fulfill the expectations. Foster Wheeler Energia Oy is further developing the gasification process towards increased use of classified industrial and municipal waste fuels. The content of alkaline, chlorine and heavy metals in the waste fuels requires a cleaning of the product gas before being fired in the utility boiler. The cleaning process contains of gas cooling and filtration. The aim is to achieve a cost effective reliable process providing a clean enough gas to enable filing in an utility power boiler. Gas purity required for gas turbines or engines is not targeted as it would require a very expensive complex system. The gas cleaning process has been tested in Foster Wheeler Energia Oy's R&D center, where a 3 MW pilot CFB gasifier is equipped with gas cooler and gas filtration equipment.