Reasonableness of dry gas seal configuration in propylene compressors
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When starting up and shutting down the plant, is it sufficient to use low-pressure nitrogen at 0.6 MPa as the primary seal gas for the dry gas seal? Is it okay to use propylene gas at 0.6 MPa as the primary seal gas under normal operating conditions? I would appreciate the insights of experts on this matter.
Yes, here we use nitrogen at 0.7 MPa as the primary sealing gas when starting up the machine; this pressure is reduced to 0.12 MPa through a pressure regulator for sealing purposes. Once everything is operating normally, propylene gas from the three-stage outlet (i.e., the high-pressure cylinder) is used as the primary sealing gas.
If propylene flashing causes high system pressure, is there any risk in using 0.7 MPa of nitrogen as the primary sealing gas during startup?
No, the flash pressure of propylene is not high either.
This post was last edited by wgqmqez on 2015-11-19 01:18. Yes, due to high system pressure and low pressure in the nitrogen pipeline network, and although there are check valves, the risk still exists. It can be replaced with medium-pressure nitrogen, using a pressure regulator to reduce the pressure.
At first, nitrogen was used due to unstable operating conditions; during normal production, it was switched to propylene
When starting up and shutting down the plant, is it sufficient to use low-pressure nitrogen at 0.6 MPa as the primary seal gas for the dry gas seal? Is it okay to use propylene gas at 0.6 MPa as the primary seal gas under normal operating conditions? I would appreciate the insights of experts on this matter. Answer: For the propylene compressor in a cracking unit, 0.6 MPa of low-pressure nitrogen is sufficient to meet the requirements. The setting for the pressure of the primary seal depends mainly on the pressure in the unit’s sealing chamber. Sealing gas must have a pressure difference to be injected into the sealing chamber.
1. It is necessary to know the type of dry gas seal, how many stages it consists of, whether a buffer gas is provided, and issues related to the pressure on the exhaust flare. 2. It is necessary to know the compressor outlet pressure. Once the compressor is operating properly, it usually switches to the propylene outlet gas as the source of gas for the dry gas seal; if the outlet pressure is below the normal level, there may be issues with insufficient flow rate or pressure.
Under normal conditions, just monitor the operating pressure and use the outlet process gas directly