Pressure Balance During Standpipe Operation

If the gas flow from the lower bed increases, the pressure drop across the upper bed distributor increases to Apd(new)- The pressure balance then calls for an increase in standpipe pressure drop. Since in this case the standpipe length is 

A standpipe commonly used in the petroleum industry is the underflow vertical standpipe with slide valve at the lower end. In this case the standpipe generates more head than is required and the excess is used across the slide valve in controlling the solids flow. Such a standpipe is used in the fluid catalytic cracking (FCC) unit to transfer solids from the reactor to the regenerator. 

Readers wishing to learn more about solids circulation systems, standpipe flow and non-mechanical valves are referred to Kunii and Levenspiel (1990) or the chapters by Knowlton in either Geldart (1986) or Grace et al. (1997). 

Design a positive pressure dilute-phase pneumatic transport system to transport 900 kg/h of sand of particle density 2500 kg/m and mean particle size 100 gm between two points in a plant separated by 10 m vertical distance and 30 m horizontal distance using ambient air. Assume that six 90° bends are required and that the allowable pressure loss is 0.55 bar. 

In this case, to design the system means to determine the pipe size and air flow rate which would give a total system pressure loss near to the allowable pressure loss. 

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Figure 8.18 Pressure balance during operation of an underflow standpipe effect of increasing gas flow through fluid beds... 

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