Abstract：In order to determine the critical speed of the actual model, a simulation model, including a single particle and a double spiral vertical screw conveyor was presented, whose screw diameter was 400 mm and pitch was 330 mm. The simulation model was established by EDEM, Recur Dyn and ADAMS.2.First, the range of critical speed was obtained through simulation.Then, using the bisection method, the range was narrowed gradually. Finally, the simulation was terminated until the critical speed was obtained. The simulation model of particle swarm were established and simulated based the same method by EDEM, whose height was 0.3 m and filling rates were 20%, 40%, 60%and 80%. The results show that the types of contact between particle and spiral surfaces and inner surface of the shell are verified. The critical speed is about 70 r/min when there is only one particle. The critical speed for four filling rates are 75, 81, 91 and 100 r/min. The critical speed which is obtained by single particle theory is 82 r/min, and the value is close to the simulation results of one particle and particle swarm with 20% and 40%filling rates. But the value is smaller than the results of particle swarm with 60% and 80% filling rates. So single particle theory is only applied to the vertical screw conveyor with small filling rate.

Keywords: vertical screw conveyor; critical speed; single particle; particle swarm