Method for recycling ethylene gas from tail gas and water alkaline washing tower thereof

Abstract

The invention discloses a method for recycling ethylene gas from tail gas. The tail gas from a buffer tank (1) enters the lower section through a gas inlet (14); after finishing exchange and absorption with water, the tail gas enters the middle section through a bypass gas pipe (8); after finishing exchange and absorption with an alkaline liquid with concentration of 1-3% at the middle section, the tail gas enters the upper section through a bypass gas pipe (9) to perform exchange and absorption with water again; after being purified, the tail gas is delivered to a gas cabinet (7) through a gas outlet (15); the water from a water circulation tank (3) enters the upper section through a water inlet (16); after finishing exchange and absorption, the water enters the lower section through a bypass water pipe (10); after finishing exchange and absorption, the water returns to the water circulation tank (3) through a water outlet (17); the alkaline liquid with concentration of 1-3% from an alkaline liquid circulation tank (5) enters the middle section from an alkaline liquid inlet (18); and after finishing exchange and absorption, the alkaline liquid returns to the alkaline liquid circulation tank (5) through an alkaline liquid outlet (19). Through the method, the content of ethylene gas can be increased from 89.5% to 96.43%, and the content of VAC can be decreased from 9.49% to 2.57%.

Description

1. Technical field [0001] The present invention relates to gaseous ethylene recovery process and equipment, more specifically a method for recovering ethylene gas from tail gas discharged in the production of polyvinyl acetate-ethylene copolymer emulsion by medium pressure method and its water-alkali washing tower. 2. Background technology [0002] In the production process of polyvinyl acetate-ethylene copolymer emulsion using the medium pressure method, the raw material ethylene gas cannot fully participate in the reaction, and after the reaction cycle ends, it will be decomposed from the emulsion product with a small amount of impurity gas by degassing under reduced pressure , these gases are called defoaming gas, commonly known as tail gas, the tail gas is characterized by containing CO, CO 2 , aldehydes, VAC, VAE emulsion and other impurities, the ethylene gas content is about 90%. [0003] In the existing process for recovering gaseous ethylene from the tail gas, the ...

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Problems solved by technology

[0003] In the existing process for recovering gaseous ethylene from the tail gas, the tail gas is only washed with a single water, and only a small amount of impurities in the tail gas are removed, while a large amount of CO, CO 2 , aldehydes, VAC, VAE emulsion and other impurities have not been completely removed, the recovered gas contains high impurities, and the ethylene content is correspondingly low (88-90%), and the recovered gas will be processed in the subsequent treatment process It brings many problems to equipment and pipelines, and even affects the quality of ethylene products

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