Improved process for recovering non-methane hydrocarbon in polyolefin tail gases by adsorption method

Abstract

The invention discloses an improved process for recovering non-methane hydrocarbon in polyolefin tail gases by an adsorption method. According to the process, each adsorption tower is sequentially subjected to steps such as low-pressure adsorption, uniform pressure rising, pressure rising, high-pressure adsorption, uniform pressure dropping, replacing, reverse releasing, evacuation and pressure rising in a circulating mode, or each adsorption tower is sequentially subjected to steps such as low-pressure adsorption, pressure rising, high-pressure adsorption, uniform pressure dropping, replacing, reverse releasing, evacuation and uniform pressure rising. The improved process has the advantages of being low in energy consumption, simple to control, easy to operate and the like, and the vacuum-pumping pressure is in a range of 10-15KPa (absolute), so that non-methane hydrocarbon product gases with the concentration higher than 90% can be obtained finally.

Description

technical field [0001] The invention relates to the recovery and treatment process of tail gas discharged under different pressures in the polyolefin production process, and is an improvement to the existing high and low pressure adsorption treatment process of polyolefin tail gas. Background technique [0002] Polymerization tail gas containing 9% to 65% ethylene (weight percentage, the same below) is produced in the production process of polyethylene. The main impurity is nitrogen. The polymerization tail gas containing 50% to 65% ethylene is mainly sent to the olefin factory for recycling, and a small amount is discharged. To the torch pipe network, while the rest of the polymerization tail gas has a high nitrogen content, which is unacceptable to the olefin plant, and all of it is discharged to the torch pipe network; the ethylene concentration of the residual gas discharged from the membrane separation of the polyethylene device is about 5%, and the discharge gas pressu...

AI Technical Summary

Problems solved by technology

Due to the adsorbent used, it is difficult to desorb high-carbon hydrocarbons such as hexane, and high energy consumption must be consumed to make the vacuum pressure of the evacuation step reach 1-8KPa (absolutely) to desorb high-carbon hydrocarbons such as hexane, otherwise high-carbon hydrocarbons such as hexane Hydrocarbons accumulate into liquid in the adsorption tower, and the device cannot operate normally

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