Small Decentralised Thermal Power Stations For Refuse-derived Fuel

We discuss a solution to bringing down energy costs and to making a contribution to climate protection. Small decentralised thermal power stations for RDF with a thermal capacity of 35 MW have some advantages in comparison to large plants. The required amount of RDF (approx. 70,000 t/a) is mostly locally available, which reduces the transport costs considerably. The produced electrical energy (up to 8 MW) and the waste heat from the thermal power station can be used in an industrial plant. An industrial plant and a refuse company founded a joint venture and built a thermal power station for RDF in Bremen. They replaced the old coal fired power station with a RDF-plant. Increasing energy costs are replaced by revenue for RDF. The industrial plant is now using the “cheap” energy from the RDF. The refuse company has a reliable customer and stable prices for its waste for long years: a typical win-win situation. After a 3-year operating time the experiences of the RDF thermal power station are positive without exception. The specified emissions are far below the limits. Furthermore, due to the fact that RDF contains a high proportion of biomass (approx. 45%) by changing the fuel from coal to RDF, a contribution to climate protection can be made. If the same amount of biogene content would be land filled, a large amount of methane, which is one of the more dangerous greenhouse gases, would be produced. The RDF thermal power station is built up modularly. The individual components are standardized so that the plant can be built fast and costeffectively. The specific investment costs per ton of RDF are comparable to large plants (>100 MW). Due to the handling of RDF in a closed hall, there is no smell outside the plant. The RDF is burnt at over 870° degrees Celsius to eliminate all pollutants completely. The steam is led through a back-pressure turbine and then used in the industrial plant. The modern flue gas treatment plant shows the expected consumption of additives. Since the initiation, the emission limits are constantly considerably below the requested limits of the EU-DIRECTIVE 2000/76/EC. www.witpress.com, ISSN 1743-3541 (on-line) © 2008 WIT Press WIT Transactions on Ecology and the Environment, Vol 109, Waste Management and the Environment IV 63 doi:10.2495/WM080071 1 Alternative energy supply through RDF heat power plants When municipal solid waste is deposited in landfills, methane is generated due to the anaerobic decomposition of the biogene content of waste. Methane is a strong greenhouse gas and about 21 times more powerful at warming the atmosphere than carbon dioxide (CO2). According to the EU landfill directive (99/31/EC) all member states have to reduce their proportion of the waste for land filling considerably in the following years. They have to sort the waste before land filling and to separate out energy-rich fractions for energetic utilization. Currently most of the waste is still being land filled in the EU. A lot of the EU-member states initially invest in mechanical biological treatment plants. A utilization of the separated middleand high caloric fractions often does not exist. Due to the high investment costs it is often not possible to finance an energetic utilization. But due to the highly increased energy costs the usage of these fractions as fuel is getting more and more interesting. This especially applies to industrial companies with a high year-round consumption of steam, in particular from the paper-, foodor chemical industry. This method of cheap and efficient power supply through decentralised small RDF-power stations is increasingly used in Germany. Small decentralised thermal power stations for RDF with a thermal capacity of approx. 35 MW have some advantages in comparison to large plants. The required amount of RDF (approx. 70,000 t/a) is mostly locally available, which reduces the transport costs considerably. The specific investment costs per ton of RDF are comparable to large plants (> 100 MW). -80 € -60 € -40 € -20 € € 20 € 40 € 0 2 4 6 8 10 12 14 16 18 20 supplied thermal capacity [MW] co st s p ro fit p er to n R D F 5,00 ct/kWh heat price Figure 1: Costs or profit per ton RDF according to the heat supply and price. www.witpress.com, ISSN 1743-3541 (on-line) © 2008 WIT Press WIT Transactions on Ecology and the Environment, Vol 109, 64 Waste Management and the Environment IV