Method for precooling centrifugal pump used for transporting low temperature ethylene

Abstract

The invention discloses a method for precooling a centrifugal pump which is used for transporting low temperature ethylene, comprising the following steps: using mini-flow low temperature liquid phase ethylene to constantly precool a back-up centrifugal pump, a liquid-in pipeline and a liquid-out pipeline and obtain gasified ethylene, constantly rolling the pump in the precooling and gasifying process, discharging gaseous phase ethylene into a low pressure gaseous phase ethylene system when the pressure of gaseous phase ethylene in the pump reaches 1.5-1.7MPa, continuously discharging for 20-30min to lead the temperature of the pump and the liquid-in and liquid-out pipelines to be up to -40 to -20 DEG C, by now, closing corresponding hand stop valves of liquid phase ethylene entering pipe and gaseous phase ethylene discharge pipe and then opening corresponding hand stop valves on the liquid-in pipeline and the liquid-out pipeline, adopting liquid phase ethylene at the temperature of -40 to -20 DEG C to pour into the back-up centrifugal pump, successfully starting the back-up centrifugal pump by once, and closing the operation of the centrifugal pump at the moment. By adopting the method, the switchover of the centrifugal pump can be easily realized, the safe and stable continuous operation of an ethylene purification device can be ensured, and the production cost can be lowered.

Description

technical field [0001] The invention relates to a precooling method for a centrifugal pump used for conveying low-temperature ethylene. Background technique [0002] At present, in the ethylene purification step, a centrifugal pump is used to transport low-temperature liquid-phase ethylene, and the temperature of the liquid-phase ethylene is generally -40 to -20°C. Referring to the accompanying drawings, there are two centrifugal pumps, one on and one on standby (that is, one is in operation and the other is in standby). Between centrifugal pump A and centrifugal pump B, there is a common inlet main pipe 10 for liquid-phase ethylene, a common outlet main pipe 5 for liquid-phase ethylene, and a minimum circulation pipeline 11 for liquid-phase ethylene. A liquid inlet line with a manual shut-off valve at the liquid inlet is installed on the liquid inlet of each centrifugal pump, and a liquid outlet pipeline with a manual shut-off valve at the liquid outlet is installed at the...

AI Technical Summary

Problems solved by technology

Because the standby centrifugal pump and its inlet and outlet pipelines are at normal temperature, low-temperature liquid-phase ethylene will gasify when it encounters the pump body and two pipelines of the standby centrifugal pump at normal temperature, while gas-phase ethylene is difficult to pass through. The two pipelines mentioned above are discharged, so when the standby centrifugal pump is running, there will be air binding (that is, the standby centrifugal pump is idling), causing the standby centrifugal pump to fail to work normally (sometimes the standby centrifugal pump cannot be successfully started for 1 to 2 hours) In addition, when the pump is pumped, the gas-phase ethylene that is difficult to discharge can easily flow back into the running centrifugal pump through the liquid inlet line of the standby centrifugal pump, causing the running centrifugal pump to fail to work, and the ethylene purification unit is forced to stop, affecting the production of ethylene Continued normal operation will bring great losses; moreover, the long-term operation of the spare centrifugal pump in the air-bound state will cause heat damage to the mechanical seal of the pump body, causing a large amount of ethylene leakage, which will increase the production cost on the one hand, and on the other hand. pose a major safety hazard

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