Aspects of multi cyclone design at limited space

U. Muschelknautz*, MK Engineering, Germany

Multi cyclones for gas-solids separation, i.e. systems of many parallel cyclone cells within a common housing having a common solids hopper, are generally used to increase the separation efficiency beyond the level which is achievable by a single cyclone. Principally increasing the number of parallel cyclone cells and decreasing at the same time their size can improve the efficiency of a multi cyclone without changing its pressure drop, provided a uniform distribution of gas and solids feed into each single cyclone cell can be achieved and bypass flows through the solids discharge openings from one cyclone cell to the other within the common housing can be avoided.

In many cases multi cyclones use standard reverse flow cyclone cells with an axial inlet, also called swirl tubes, Fig. 1 left. Analogously multi cyclones can be made from uniflow cyclone cells, Fig. 1 right. Often those devices are used in space limited applications, e.g. as third stage separators in fluid catalytic cracking (FCC) processes. In both cases axial inlets with swirl vane inserts for vortex generation are used. The main difference between both cyclone types is that in swirl tubes the gas flow reverses its direction and pure gas and collected particles are leaving the device at opposite sides, whereas uniflow cyclones have gas and particles passing through them in only one direction exiting at the same end of the device. Due to those design differences unifow cyclones can be built much more compact and can easily be integrated into pipe lines. However, generally their efficiency for separating a specified gas-solids flow at a given pressure drop is slightly lower than the efficiency of standard cyclones.

Fig. 1: Multi cyclones consisting of 16 standard cyclone cells (left) and of 36 uniflow cyclone cells (right) using about the same cross sectional area for the housing.

Often space for a dedusting unit is limited in an industrial plant. The question arises whether under the restriction of limited space a multicyclone made from uniflow cyclone cells may be more favorable than its standard cyclone counterpart. The background of this question is that due to their compact design more uniflow cyclone cells can be packed into a given volume than standard cyclone cells would have place in it. Thus, since efficiency increases with increasing number of cyclone cells it seems to be possible that – under certain conditions regarding geometry any operation data – a multi cyclone based on uniflow cyclone cells can achieve a comparable or even higher efficiency than a standard cyclone solution, when those devices are subject to the restriction of limited space. The present investigation addresses this question by...

Session: G11 - Short Oral + Poster Presentations II
Day: 14 March 2018
Time: 14:45 - 16:45 h

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