The turbulent flow field inside an industrial cement kiln was calculated via the finite volume method. The calculation domain includes multistage cyclone preheater, pre-calciner, and a part of rotary kiln. The primary air is supplied through a rotary cement kiln which is connected to the pre-calciner. The steady state velocity field showed that a strong circulating flow pattern was formed in the first and second stage cyclone preheaters. To analyze the blocking effect of solid particles in the pipes attached the cyclone bottom part, the case without the connecting pipes was compared with the reference case with the connecting pipes. As the blockage ratio changes depending on the operating conditions, the simulation results for the two cases provide valuable information for the two extreme situations where the reference case represents non-blocking and the modified case represents complete blocking. To simulate the variable blocking effect of solid particles in the connecting pipes, a part of pipes was filled with porous medium. The effect of viscous resistance of the porous medium on the flow field was numerically investigated.