pressure drop across a vessel

[gundee]

I am just starting back as an engineer and am a bit rusty. A new vessel is being installed and we know that the pressure drop across the vessel is 30 psi. The exchanger this lines feeds depends on constant flow and the existing line pressure. What is the best way to maintain the flow and increase the pressure?

 

[reena1957]

Dear Gundee, How do you achieve the pressure drop of 30psi across the vessel: Does it have some packing /trays /catalyst /liquid level? Do you You have a control valve in the circuit? Pl give more details of the Process flow.

 

[sshep]

Is this a liquid full system, or vapor? A bit more process description would be helpful.

If pressure and flow are critical then a system of back pressure (w. transmitter at point of interested) and flow controls (may already exist) are indicated. If this is a liquid full system then I will preempt the suggestion that back pressure control in series with flow control is impractical by saying that I see it working quite often- both with two control valves, and one control valve + variable speed pump.

good luck,
sshep

 

[gundee]

The vessel does contain a catalyst and several gate valves entering and exiting, thus the pressure drop. The line is high pressure and a gas. I am checking the lines for back pressure and flow controls.

 

[sshep]

Is the gas a recycle from a compressor, or once through from an upstream process?

 

[reena1957]

Dear Gundee, You have to come out with more details like what is the system, reactor, liquid, recycle gas, make-up compressors( like sshep asked), feed/reactor effluent exchanger, cooler, allowable pressure drop across the catalyst bed(30psi is a bit too high), etc. Give more details to get a reasonable suggestion.

 

[gundee]

The gas is a once through from an upstream processs. The gas is coming from a compressor. The problem is that other lines enter and exit this line before it hits the catalyst vessel. We want to maintain line pressure, so that the other lines to other parts of the plant are not effected.

 

[djack77494]

Your compressor control system would normally "be responsible" for maintaining the correct pressure. It's still not clear to me what may be changing/staying the same. If you are keeping the same flowrate everywhere and just want to increase system pressure, then your problem is simple. The compressor & its controls can do the job or not. If you want higher pressure in some places but not others, then you must increase the system pressure and regulate pressure going to the low pressure users. Let me know if I've missed the point.
Doug