Q & A > Question Details
In DHDT unit, RGC anti-surge control valve is opened at around 13-15 %, at this opening deviation from surge line is 0.14-0.20. The design molecular weight of Recycle gas considered is 2.94 whereas actual Recycle gas molecular weight is in the range of 2.25-2.4. Suction temp/ Pres:63 deg C /110 kg/cm2;Discharge temp/ Pres:90 deg C /131 kg/cm2
1.0 Can we fully close the anti-surge valve in order to increase energy efficiency of RGC ?
2.0 what other actions can be taken to minimize RGC anti-surge opening ?
3.0 By Incorporating the actual recycle gas molecular weight in anti surge controller block and compression suction flow transmitter, will there be any improvement in deviation from surge line ?
26/03/2014 A: Narendra Naidu, Bapco, nbpnnaidu@gmail.com
Firstly we need to understand the entire set up
1. Do you have a flow control valve at the Inlet to the Feed/Reactor effluent exchanger where the recycle gas is mised with feed?
2. Do you have a variable speed recycle compressor is there room for increasing the speed?
3. Do you have room to reduce the Suction gas temperature of Recycle gas compreesor? if it is coming from a Amine scrubber, check the Lean Amine temperature.
4. Do you bleed some gas from you recycle gas suction system to keep the purity of H2 in system?
5. What is the Delta P across the Reactor beds?
If you get the answers for these then it should help you in using the right solution to get the Antisurge valve closed .
The one lever i would use first is increasing the speed of the compressor if you have room in your speed control of machine and also heater.
30/11/2013 A: Cesar Marcano, Pequiven , cesarmarcano73@gmail.com
If you are close to safety line , the MW of gas can create a Head reduction then the compressor try to open the ASV to increase the head, mainly you can try to adjust the process upstream to improve the MW because if you speed up the compressor to reduce the deviation the suction pressure reduce also the the Compressor will surge finally shutdown it..
In a CO2 compressor for urea plant with H2 leakage from ammonia plan is imminent the effect , but in your case I recommend to adjust the process side to adjust the expected value 2.94.
Another operational change is reduce the temperature to improve the density but probably is not enough