The flagship and most important innovation of the Güssing model is the biomass plant, which uses a special fluidized bed steam gasification technology. The process developed at the Vienna University of technology (Univ. Prof. Dr. Hofbauer) offers some advantages as compared to conventional combustion processes, especially in combined heat and power applications. For the realization of the project several partners cooperated within the competence network RENET: REPOTEC plant technology, Vienna University of Technology, EVN, and the Güssing district heating utility.
The plant, which started operation in 2001 has a rated fuel capacity of 8 MW and produces 2,000 kWh electric power as well as 4,500 kWh heat for district heating at a feed rate of 2,300 kg wood per hour. The plant currently operates for 8,000 hours per year.
The vital component of the plant, i.e. the fluidized bed gasifier consists of two fluidized bed systems that are connected with each other. Biomass is gasified, together with steam, at a temperature of approx. 850°C in the gasifying zone. Using water vapor instead of air as gasifying medium results in a nitrogen-free, low-tar product gas with high calorific value.
Part of the residual char is conveyed, by the circulating bed material (sand), which also serves as heat storing medium, to the combustion zone and is burned there. The heat transferred to the bed material is needed to maintain the gasification reactions. The flue gas is then separated and the heat contained therein is used in the district heating system.
The product gas has to be cooled down and cleaned for use in the downstream gas engine. Heat recovered in the cooling process is, again, used for the district heating system. A special technology permits to recycle all residuals, which means that the gas cleaning process generates neither waste nor effluent.
The gas engine converts chemical energy contained in the product gas into electricity. Again, waste heat from the engine is fed into the district heating system. This approach results in very high efficiencies: electric efficiency ranges between 25 and 28 %, overall efficiency (power and heat) is approx. 85 %.
On account of the favorable properties of the product gas (no nitrogen, high hydrogen content), there is a broad range of possible uses, such as the generation of fuel gas, synthetic gas, gasoline and diesel, methanol as well as hydrogen.
The various research projects currently conducted in Güssing address topics such as the generation of hydrogen, fuel cells, the production of methane and fuels, cooling and district heating systems and aim to test and implement new technologies. The overall objective consists in the development of energy centers meeting the demand of the region, and which are able to produce heat, electricity, gaseous and liquid energy carriers from a variety of energy-rich biogenic raw materials and residue matter using an approach called polygeneration. The quantities produced of the various resources will depend on the needs and the size of the respective region. The relative proportion of the various by-products cannot be changed infinitely, it is true, but modifications should be possible within certain limits.
The experience gained in the biomass plant Güssing gave rise to a number of research projects, which were realized in cooperation with various Austrian and international partners in the fields of science and industry (e.g. Volkswagen, Daimler Chrysler, Volvo, EDF, and BP). Some of the projects have already been realized in Guessing, others are at the stage of planning or on the verge of implementation. The strategy for the period between 2007 and 2013 aims to implement the concept of “polygeneration”.
