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How to divide a Pneumatic Conveying Stream

Pneumatic Conveying Lines

How to divide a Pneumatic Conveying Stream

Splitter for continuous distribution of bulk solid material during pneumatic conveyance - dimensioning, calculation, operating behaviour. Worldwide, a great number of so-called splitters are in operation as elements of pneumatic conveying lines, in order to continuously distribute the conveyed bulk material to several receiving stations. These splitters have taken an important position within the pneumatic conveying systems and are applied in different designs. But there is not much literature available dealing with the phenomenon “splitter”, and providing assistance regarding application possibilities, dimensioning, selection and experiences during operation. The available literature mostly deals with answers to specific questions, like for example pressure losses in various ramifications, etc.
(ed. wgeisler - 31/5/2017)
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As can be seen from Fig. 14, the distribution of the material is very even and the conveyance is relatively quiet. The O2 content, which is also shown, and the boiler load show a good burning and increase of load.


Fig. 14: Measurement plots of the pneumatic conveyance with a four-fold splitter                               

A silo dosage station can be coupled to each pipe if needed, so that there is no exclusive dependence on the silo-truck. The silos are also transportable. The big advantage of this solution is the clean handling without interferences through pollution, etc. Experience during operation has been markedly positive after the start of the operation.

A third example, presented in Figs. 15 to 17, shows a pneumatic supply system for injecting a flyash-lime mixture into a reactor. The purpose is to supply the reactor with 23 tons per hour of the aforementioned mixture with a volume flow of air of 2000 m3 per hour. The material is stored in a single silo. 


Fig. 15: Pneumatic injection system with two eightfold splitters for supplying a reactor with   
a flyash-lime mix                                                                                                                    

The challenge was to distribute evenly distribute this mass flow onto 16 injectors at the reactor. For this purpose the silo was designed with a twin outlet, which supply two eightfold splitters which in turn supply the injectors. The plant was installed and brought into operation in August 2015 and has worked to the satisfaction of the operator since then.


Fig. 16:  16 Injectors supplied by two 8-fold pneumatic conveying lines         

Fig. 17: Two splitters, supplying eight pneumatic injection lines each                  

5   Conclusion

Splitters in pneumatic conveying plants require a careful design and calculation. Not all splitter types are ideal for each and every application.

Specific characteristics, dependent on geometry and material, were depicted in the example of a dilute phase splitter for fine grain bulk material. Frequently asked questions were responded to. Furthermore the general calculation and layout, including operation behaviour and integration into the plant environment was discussed.

Examples of established splitters were introduced and the specific case of application was explained.

References

[1]   Morimoto, T., A. Yamamoto, and T. Nakoo: ,On the Behaviour of Air-Solids Mixture in a Pipeline for Pneumatic Conveyance with Single or Double T-Branches. Bull. J.S.M.E., Vol. 20 (1977), pp. 600–606A.
[2]   Selves, T.P., and R.N. Bames: Review of in-line splitting techniques used in pneumatic conveying; Trans. Inst. Eng. Aust. Mech. Eng. VME 18 (1993) No. 1, March, pp 51–56.
[3]   Low, H.T., S. Kar, and S.H. Winoto: Pneumotransport of Solid Particles through Manifold System; Proc. Third Asian Congress on Fluid Mechanics, Tokyo, (1986) pp. 630–639.
[4]   Morikawa, Y. et al.: Pressure drop and solids distribution of air-solids mixture in horizontal unsymmetrical bends; Journal of Multiphase Flow, Vol. 4 (1978), pp 397–404.
[5]   Lempp, M.: Die Stroemungsverhaeltnisse von Gas-Feststoff-Gemischen in Verzweigungen pneumatischer Foerderanlagen; AT Aufbereitungstechnik 7 (1966), pp. 81–91.
[6]   Thomas, G.: Verteilungsmessungen an einem 16-fach Staubverteiler; LCS-Steinmueller, 1986

Patents

[7]   OS DE 28 29 867; Ruhrkohle AG, Inventors: Schroer, Schedbauer, Zilles­sen.
[8]   OS DE 28 32 846; Rockwell International Corp; Inventors: Oberg et al.

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