Powder compression is essential in the storage and transportation processes. The compression characteristics of pulverized coal, rice husk and lignocellulose were compared under mechanical and gas pressurization respectively. The experimental results showed that the descending order of relative packing density was lignocellulose > rice husk > pulverized coal under mechanical pressurization, while an opposite trend was observed under gas pressurization. The effect of cohesion properties on compression results, such as inter-particle adhesion force and powder bed cohesion, was also investigated. For mechanical pressurization, the powder bed of cohesive biomass had higher void fraction, which was directly linked to larger relative packing density. On the contrary, gas permeated easily into the biomass powder bed, and the lower pressure drop decreased the compression capacity of gas pressurization. In addition, a model for predicting the relative packing density was proposed with an error of ± 5%.

In this paper, the relationship between the conveying pressure drop and the gas velocity were firstly characterized based on pressure signal analysis. The critical gas velocity was obtained to classify the transfer bottle into stationary station and motion state, and pressure fluctuation characteristics in each state were determined. Further, derived from the traditional additional pressure drop method, the model for pressure drop prediction was developed. The gas pressure drop was further divided into four terms, including those in the conveying pipe, through the sudden contraction from the pipe to the head of the transfer bottle, through the sudden expansion from the end of the transfer bottle to the pipe, and through the gap between the bottle and the pipe. The solid-phase friction pressure drop was determined based on correctly estimation of the dynamic friction coefficient.The model can satisfactorily predict the pressure drop, giving errors mostly smaller than ±10%.

The force exerted on particles is of great significance to the flow and reaction characteristics of particles in gasifier. In this study, the unbalanced thrust, especially its magnitude, of a single char particle induced by chemical reactions during combustion process is investigated numerically, based on the random distribution of active sites. It is revealed that the nonuniform distribution of active sites directly leads to the nonuniform release of gaseous products, which accounts for the net induced thrust of particles. The effects of active site ratio, ambient gas temperature and particle diameter on the induced thrust of reaction particle were investigated. The results show that the induced thrust on particles could be equal to the magnitude of particle gravity. The induced thrust decreases with the increase of active area and particle diameter. And it is enhanced with the increase of ambient temperature.