Application of pulse flow to a fluidized bed for combustion and gasification of wheat straw – A possible way to mitigate agglomeration

• Application of a pulsed flow to the reactor can reduce the agglomeration tendency in fluidized bed combustion of wheat straw. • In fluidized bed gasification of the straw, the effect of the pulsed flow is similar to the combustion with respect to agglomeration. • Among the parameters studied, pulsation duty cycle exhibits the most significant effect on reducing agglomeration tendency. • Application of a pulsed flow shows a negligible impact on combustion behavior. Agglomeration may cause severe operational problems in fluidized beds for biomass combustion and gasification. Application of external forces is a common way for improving fluidization quality, which may act as a potential countermeasure to mitigate the agglomeration problem. In this work, a pulsed flow is applied to a fluidized bed reactor to examine its effect on mitigating agglomeration in combustion and gasification of wheat straw. The influence of the pulsation parameters, including flow ratio of pulsation/total flow, pulsation frequency and pulsation duty cycle, on the agglomeration tendency were studied in a lab-scale bubbling fluidized bed reactor using silica sand as bed material. The results reveal that application of a pulsed flow to the reactor can reduce the agglomeration tendency in fluidized bed combustor and gasifier. The maximum reduction of agglomeration tendency has been achieved under a condition with pulsation flow ratio of 0.4, pulsation frequency of 1.5 Hz and pulsation duty cycle of 25/75. Among the parameters studied, pulsation duty cycle exhibits the most significant effect on reducing agglomeration tendency, while pulsation frequency in the studied range shows the smallest impact. Moreover, the results show that the combustion performance is not affected by application of the pulsed flow.