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The fixed-bed lab-scale reactor is an unique device for fundamental investigations concerning the thermal decomposition, pyrolysis, gasification and combustion behaviour of various biomass fuels. It consists of a cylindrical retort, which is heated electrically up to about 800 °C and is controlled by two separated PID-controllers. The fuel is put in a cylindrical holder (100 mm height, 95 mm inner diameter). Both parts are made of fibre-reinforced silica carbide (SiC)-ceramics to avoid reactions of the product gases and ash with the wall. The mounting and vessel for the fuel bed are placed on a scale which is used to determine the weight loss of the sample during the thermal decomposition process. With this setup it is possible to continuously measure the mass reduction of the sample during the pyrolysis/gasification/combustion process. The sample, which typically weighs 100 to 400 g (depending on the density), is introduced into the pre-heated reactor and therefore, a rapid heating can be achieved. Fuel bed temperatures are measured at 5 different positions in order to observe for instance the propagation and the velocity of the combustion front.
Continuously working FT-IR, ND-IR, FID, CLD and heat conductivity analysers are applied in order to determine the concentrations of O2, CO, CO2, H2O, H2, OGC, NO, NO2, HCN, NH3, HCl, SO2 as well as of various hydrocarbon compounds during the conversion steps. Moreover, discontinuous tar sampling and subsequent analyses can be applied. With the set-up it is possible to comprehensively monitor the thermal conversion process and additionally to gain information about e.g. the release of relevant NOx-precursors from the fuel. Moreover, by analysing the initial sample and the residues remaining after the conversion process, information about the release of easily volatile ash forming elements e.g. S and Cl as well as of semi volatile ash forming elements (K, Na, easily volatile heavy metals like Zn and Pb) can be gained.
With the fixed bed laboratory reactor fundamental studies on thermal decomposition, pyrolysis, gasification and combustion can be carried out for different biomass fuels. The equipment focuses on fuel beds. A cylindrical sample holder (100 mm height, 95 mm inner diameter) contain typically 100 to 400 g of fuel (depending on the density). The sample holder for the fuel bed is located on a scale that is used to determine the weight loss of the sample during the thermal decomposition process. With this setup, it is possible to continuously measure the mass reduction of the sample during the pyrolysis / gasification / combustion process. Furthermore, fuel bed temperatures are measured at 5 different positions, to determine the temperature distribution (e.g., spread and the velocity of the combustion front or progress of pyrolysis) in the fuel bed.
Continuously working FT-IR, ND-IR, FID, CLD and thermal conductivity analysers are used to determine concentrations of O2, CO, CO2, H2O, H2, OGC, NO, NO2, HCN, NH3, HCl, SO2 and various hydrocarbon compounds during the conversion processes. The measurement methods to determine the product gases are dependent on the conversation process applied. In addition, a discontinuous tar sampling can be applied with subsequent analysis of the tars. In the case of combustion processes, a comprehensive determination of the thermal conversion process is possible and in addition, the tests can provide information about, for example, the release of relevant NOx precursors from the fuel bed. Moreover, by analysis of the fuel and the residues after conversion process, information on the release of S and Cl and of volatile ashes visual elements (K, Na, volatile heavy metals) can be obtained. During pyrolysis or torrefaction processes a characterization of the resulting product gases, the tars and the solid residues is possible. For these applications, a determination of the release of volatile inorganic elements can also be carried out.
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In carrying out experiments with the fixed-bed lab-scale reactor various conversion processes (e.g. pyrolysis, gasification and combustion) can be carried out on a laboratory scale. The big advantages are the controlled experimental conditions in the laboratory scale. Moreover, the effort for the tests is also only a fraction compared to large scale systems.
So far, a variety of various biomass fuels with respect to their combustion behaviour were characterised. The main parameters of these experiments are the decomposition behaviour, resulting flue gas components, the release of NOx precursors from the fuel bed and the release of relevant aerosol forming elements. Based on this data conclusions on the combustion behaviour of the fuel used in large-scale plants are possible. With this reactor specific biomass fuels mixtures and the influence of mineral additives on the combustion behaviour were studied. The set-up has proven its applicability regarding these investigations and can make a significant contribution to the selection or preparation of design fuels.
The reactor was also successfully used for the characterisation of pyrolysis and torrefaction processes. Again, relevant process parameters can be obtained, which can be transferred to real scale processes.
Brunner, T.; Biedermann, F.; Kanzian, W.; Evic, N.; Obernberger, I.; Advanced biomass fuel characterization based on tests with a specially designed lab-reactor. Energy Fuels 2013, 27 (10) , pp. 5691 – 5698
Sommersacher, P.; Brunner, T.; Obernberger, I.; Kienzl, N.; Kanzian, W.; Application of novel and advanced fuel characterization tools for the combustion related characterization of different wood/Kaolin and straw/Kaolin mixtures. Energy Fuels 2013, 27 (9), pp. 5192–5206
Sommersacher, P.; Brunner, T.; Obernberger, I.; Kienzl, N.; Kanzian, W.; Combustion related characterisation of Miscanthus peat blends applying novel fuel characterisation tools. Fuel 2015, 158, pp. 253–262