Questions regarding the pure gas-phase start-up of the propylene compressor in the ethylene plant
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Is a pure gas-phase start-up of the propylene compressor in an ethylene plant possible? How to ensure that the outlet does not trigger a high-temperature interlock? What are the things to keep in mind? Please help, experts
bk13.jpg My plant has a capacity of 1.8 million tons per year for the production of olefins from methanol; for olefin separation, propylene-based refrigeration compressors are used, which provide coolant temperatures of 7°C, -24°C, and -40°C. To start up the propylene plant, first pressurize it with gaseous propylene, and then introduce liquid propylene! How to control the outlet temperature at the start-up in a pure gas phase?
Now the management requires starting the operation in a purely gas phase without any liquid phase, which is quite problematic
Now the management requires starting the operation in a purely gas phase without any liquid phase, which is quite problematic
Without using rapidly cooled propylene for cooling, and with nitrogen remaining in the system, it is easy to experience overheating and overpressure as the rotation speed increases; this is particularly difficult to achieve in a purely gas phase environment. But nothing is absolute; if there is an adequate supply of gaseous propylene, thorough system purging, and sufficient pre-cooling. By gradually increasing the rotational speed, condensation of the liquid-phase propylene can be achieved through the water cooler at the outlet, thus resolving the problem; however, this method of starting up has never been put into practice. Because our propylene unit has a large critical range, trans-critical operation poses a significant problem.
Also, I’m not sure whether your propylene unit is equipped with a propylene tower; if it is, system fluctuations will be greater during startup. It is also necessary to determine whether the outlet temperature is equipped with interlocking.
With a series of flares, it’s not sure whether it’s possible to gradually increase the rotational speed
At the critical speed, there is a sudden rise in temperature; even when a liquid phase is present, if nitrogen (leaking into the system from the dry gas seal before it is switched to propylene gas) is not completely removed, the temperature rise beyond the critical point becomes very large. In such cases, it is necessary to use the liquid phase to rapidly cool the propylene. Therefore, this can be said to be difficult to achieve, but it can still be tried. The original poster posted this last year; I wonder if the testing was successful by now? I have time to share my test-driving experiences with everyone.
Theoretically, as long as there is an adequate supply of gaseous propylene, thorough displacement, and sufficient pre-cooling. It is possible to start the propylene unit in a pure gas phase. But so far, no one has been heard of using this method to drive.