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%.