Hello
In one of the columns (Deethaniser) in my refinery (not commissioned) there is a butterfly valve at the inlet of the hydrocarbon line. The note for the valve says that
"Valve to allow operator to throttle the inlet pressure to the thermosyphon to achieve optimum performance. Downstream pressure gauge shall be readable from the valve".
As per my understanding thermosyphon operate by the difference in density of the inlet liquid hydrocarbon and outlet mixture of liquid and vapor hydrocarbon. The driving force for the liquid to flow through the reboiler is the liquid head from column to the inlet of reboiler and the density difference. Generally in other units I have seen that if there is a valve at the inlet of the thermosyphon reboiler, it is fully open to minimise pressure drop. Now my question is:
If the valve is throttle to control downstream pressure, how would it affect the performance of the reboiler? Instead the liquid level in the coulmn shall increase to provide more head for the hydrocarbon flow.
Please correct if my analysis is wrong. A copy of the P&ID is attached for reference.
regards
rabindra