Characteristics of Gas-Solid Flow in an Intermittent Countercurrent Moving Bed

The calculation equations of pressure drop and solid flow rate are given in an intermittent countercurrent moving bed with multiple optimized structures. The flow fields are investigated by experimental methods under different conditions, e.g., ratio of position of the gas distributor to the bed width (r(p) = 0.5 similar to 1.5), gas superficial velocity (u(g) = 0 similar to 0.1591 m/s), solid outlet diameter (D-o = 5 similar to 25 mm) and cone angle (alpha = 0 similar to 60 degrees). It is found that when r(p) >= 1.0, the flow field in the bed is little affected by r(p). Flow patterns are divided into three modes: continuous discharging, intermittent discharging (synchronous, asynchronous) and particle bridging. During continuous discharging, the calculation formula of the solid flow rate, which is closely related to D-o and gas-solid slip velocity v(slip), is established by referring to the modified De Jong and Beverloo formulas, and its error <= +/- 12.5%. The pressure drop of the total bed consists of the pressure drops of the granular bed and the solid outlets, which are affected by D-o, v(slip) and alpha; it is built by referring to the Ergun formula, and its error <= +/- 17.0%. As the solid flow rate and pressure drop influence each other through v(slip), an iterative algorithm is proposed to enhance the computation accuracy.

Automated summary

This study presents the calculation equations of pressure drop and solid flow rate in an intermittent countercurrent moving bed with multiple optimized structures. The flow fields were investigated experimentally under different conditions. It was found that the flow field in the bed is little affected by the ratio of position of the gas distributor to the bed width when it is greater than or equal to 1.0. The flow patterns were classified into continuous discharging, intermittent discharging (synchronous, asynchronous), and particle bridging. The study also established calculation formulas for the solid flow rate and pressure drop and proposed an iterative algorithm to enhance the computation accuracy.