A NEW METHOD FOR QUANTIFICATION OF FLUIDIZED-BED AGGLOMERATION TENDENCIES - A SENSITIVITY ANALYSIS

A new method for quantification of fluidized bed agglomeration tendenc ies for different fuels has been developed and evaluated. A bench scal e fluidized bed reactor (5 kW), specially designed to obtain a homogen eous isothermal bed temperature, is used. The method is based on contr olled increase of the bed temperature by applying external heat to the primary air and to the bed section walls, In addition, temperature ho mogeneity is secured by switching from normal fuel feeding to a propan e precombustor. The initial agglomeration temperature is determined by on- or off-line principal component analysis of the variations in mea sured bed temperatures (four values) and differential pressures (four) . To determine potential effects of all the process related variables, an extensive sensitivity analysis was performed. Experiments were per formed according to a statistical experimental design to evaluate the effects of eight different process analytical variables on the determi ned agglomeration temperature of a biomass fuel. The results showed th at for a given fuel, the amount of bed material, heating rate, fluidiz ation velocity, and air to fuel ratio during both ''ashing'' and heati ng did not influence the determined agglomeration temperature. Only as h to bed material ratio, the ashing temperature, and the bed material particle size had significant effects on the agglomeration temperature , but still the effects were relatively small. The agglomeration tempe rature of the fuel could be determined to 899 degrees C (avg) with a r eproducibility of +/-5 degrees C (SD). The inaccuracy was determined t o be +/-30 degrees C (SD). Based on the results, the method was standa rdized with respect to ash to bed material ratio, bed material particl e size, and ashing temperature. Relative agglomeration temperatures of different fuels, fuel, and additive combinations can thus be determin ed with a high precision.