A system and method for recovering carbon dioxide in refinery dry gas by combined absorption method

Abstract

The invention provides a recovering system and a method of C2 in refinery dry gas by a compound adsorption method. The recovering system comprises a compressor, a pretreatment unit, a refinery dry gas cooling unit, a compound adsorption unit and a rectification unit. The adsorption unit comprises a gas-liquid separating tank, a C2 adsorption tower, and a methane desorption tower. The rectification unit comprises a C2 removing tower and an ethylene rectification tower. The refinery dry gas, after being compressed, pretreated and cooled, is subjected to gas-liquid separation to obtain a gas phase and a liquid phase. The gas phase is fed into the C2 adsorption tower and subjected to C2 adsorption by using a C4 mixture or a C5 mixture as an absorbent. The liquid phase is fed into the methane desorption tower, and subjected to methane desorption through stripping. The mixed adsorption oil at the bottom of the C2 adsorption tower and desorption gas at the top of the methane desorption tower are returned to the gas-liquid separation tank after being mixed and cold with the refinery dry gas. Tower bottom of the methane desorption tower is cooled and fed into the C2 removing tower and the ethane rectification tower to be rectified to obtain an ethylene product and an ethane product. The method provided by the invention adopts moderate operating conditions. The ethylene and the ethane both have the high recovering rate and the high purity.

Description

technical field [0001] The invention relates to a technology for recovering carbon dioxide in refinery dry gas, specifically, the invention relates to a system and method for recovering carbon dioxide in refinery dry gas by a combined absorption method. Background technique [0002] Refinery dry gas is a by-product of the petroleum refining process, mainly containing ethylene, ethane and hydrogen, of which ethylene and ethane are the main components. Ethylene is the basic raw material of petrochemical industry, and ethylene output has become a symbol of a country's petrochemical industry; ethane is a high-quality raw material for ethylene production, and its cyclic cracking ethylene yield is as high as 80wt%, and the composition of ethane cracking products is relatively simple, and subsequent separation is easier ; Hydrogen is a valuable resource in refineries. At present in our country, refinery dry gas is mainly used as fuel gas, which is an important chemical resource. E...

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Problems solved by technology

[0008] In order to solve the main problems of the existing method for recycling refinery dry gas, such as low carbon dioxide recovery rate, low purity of recovered ethylene, limited scope of application, high energy consumption and adverse effects on the device, the invention provides a combination The system and method for recovering carbon dioxide in refinery dry gas by absorption method realizes high recovery rate of ethylene and ethane (both greater than 95%), and the recovered ethylene and ethane have high purity

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