To investigate the characteristics of the flow field of high solids in solid state fermentation reactor with mechanical agitators and optimize the design parameters of mechanical agitators

computational fluid dynamics (CFD) method was used to simulate the flow field of five types of mechanical agitators

and parameters such as ratio of impeller diameter and stirring speed were analyzed quantitatively through the indexes of stirring power

mixing time

mixing energy

and the percentage of dead zone. Simulation results show that the high solids had a small range of disturbance and a large percentage of dead zone

indicating that it cannot be effectively mixed through double blade and turbine agitator. The high solids had the largest range of disturbance

the smallest percentage of dead zone

and the biggest stirring power through double helical agitator. For the impeller diameter of the double helical agitator

the dead zone decreased with the increase of the ratio of impeller diameter

and when the ratio of impeller diameter increased to 0.75

it no longer decreased

while the stirring power increased with the increase of the ratio of impeller diameter all along. With regard to the stirring speed of the double helical agitator

the stirring power increased linearly with the increase of the stirring speed

the mixing time decreased along a parabolic curve

and the mixing energy gradually increased. Considering a balance of mixing performance and mixing power

the double helical agitator with a stirring speed of 20 r/min and the ratio of impeller diameter of 0.75 was the best agitator design in this reactor.