Conveying system design

Fly ash comes from the combustion of pulverised coal in a boiler. The resulting ash is mostly carried over with the combustion gases. The coarse ash soon drops out of suspension 

Conveying air velocity is clearly important and that at the material feed point into the pipeline is critical. A problem comes in evaluation of this velocity, for compressors are specified in terms of a given quantity of air being delivered at a given pressure, and the reference point for each is different. The volumetric flow rate of the air delivered, Vo, is that at free air conditions (standard atmospheric pressure and temperature) and this will generally be close to that at the pipeline exit. The delivery pressure will be close to that at the pipeline inlet. Compressibility, therefore, must be taken into account. 

The inclusion of the characteristic gas constant, R, in this equation means that this equation can be used for any gas. Nitrogen, carbon dioxide, superheated steam and many other gases are often used for pneumatic conveying. The following equations, however, are derived in terms of air only. If any other gas is employed the equations will have to be re-worked with the appropriate value of R. 

This applies for any gas and is essentially a continuity equation for the conveying system and pipeline. 

The volumetric flow rate of the air (or any other gas) at any point can be obtained from  

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V.K. Agarwal, M.D. Bharathi and D. Mills. An Experimental Investigation into the Influence of Material Properties on Pneumatic Conveying System Design for Fly Ash. Proc. The Asian Symposium on Multiphase Flow 99. Osaka. Oct./Nov. 1999. 

M. V. Arastoopour, M. V. Modi, D. V. Punwani, and A. T. Talwalker,M Keview of Design Equations for Dilute Phase Gas-Solids Hori ntal Conveying Systems for Coal and Belated Material, Powder and Bulk SoHds Conference, Philadelphia, 1979. 

Perkins, Don E., Wood, Jim E., Design and Select Pneumatic Conveying Systems. Hydrocarbon Processing, March 1974. 

Design conveying system to convey captured contaminants away (separate tree). 

If the conveying velocity is a critical parameter, then the designer of a pneumatic conveying system should also consider the expansion effect caused by the pressure drop along the conveying line. The resulting increase of the gas velocity can be accounted for by increasing the pipe diameter. 

These problems in turn were hampering the successful design and/or operation of long-distance pneumatic conveying systems and hence, the future potential of this method of transport to a wide variety of industries. 

Pan, R., and Wypych, P. W., Design of Economic Pneumatic Conveying Systems, MECH 94, Int. Mech. Eng. Congress Exhibition, IEAust, Proc, 2 137-141, Perth, WA (1994)... 

Wypych, P. W., and Hauser, G., Design Considerations for Low-Velocity Conveying Systems Pipelines, Pneumatech 4, Int. Conf. on Pneumatic Conveying Technology, pp. 241-260, Glasgow, Scotland, Powder Advisory Centre, UK (1990)... 

Conveying data presented in this form clearly show the capability of pneumatic conveying systems and the inter-relating effects of pressure, material concentration and pipeline bore, as well as air flow rate when designing a system to convey a material at a given flow rate, over a specified distance. Since there is generally a limit on air supply pressure, a compromise has to be made between solids loading ratio and pipeline bore. 

E.A. Knight, M.G. Jones, P. Marjanovic, On-site measurement for troubleshooting pneumatic conveying systems, Proceedings of die Bulk Design Seminar, Sutton Coldfield, UK, December 1998. 

Experiments were conducted to determine quantitatively the amount of particle deposition in the pipeline of a specially designed pneumatic conveying system [17,18], A schematic layout of the rig is shown in Fig. 7. Briefly... 

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