| Because of the behindhand facilities and technology of coal combustion, there are certain problems such as low combustion efficiency, serious pollution problems or costly fuel cost in a large number of regular boilers (including pulverized-coal-fired boilers, chain grate stoker boilers, oil-burning boilers) in our country. One of solutions to above problems is to retrofit those boilers to CFB ones. Gas-solid separator plays a vital role during the process. To this case, a new kind of cyclone, the horizontal square cyclone, has been presented in this paper.There are three parts in this paper. In the first part, the development of cyclones has been summarized, including capability criterions for cyclone evaluation, factors about separation capability and development of flow field within cyclones and several classical cyclones. Then the horizontal square cyclone has been introduced for boiler retrofit.In the second part, based on the elementary configuration-optimization test on the horizontal square cyclone, the experiment about separation efficiency and pressure drop has been done. The results shows that, for the particle which diameter is larger than 100 u m, the separation efficiency of the cyclone is higher than 90%, while its pressure drop lower than 1500 Pa; dc50 is about 50μm (while v = 18 m/s, P = 0.8 kg/m3), In addition, by analyzing these data, two empirical regressing formulae have been put forward upon separation efficiency and pressure drop.In the last part, FLUENT is used to calculate the trajectory of particles, which have different sizes. Then some information about flow field has been obtained besides the particle trajectories. The result shows that two clear vortexes exist in the cyclone, strong swirling vortex round the exit pipe and weak one near back wall of the half-tilted cone.
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