Research Of Recovering Catalytic Dry Gas Of The Refinery To Produce Ethylene Gas

Catalytic cracking plant is the most important secondary processing plant of the refinery in China in increasing crude oil processing depth, a large amount of by product - dry gas shall be produced during the processing. Among the secondary processing plant of the refinery in China, the total refining capacity of the catalytic cracking plant ranks the first, its gas yield is the highest, and its olefin content in the gas is the largest. At present most of the catalytic dry gases are used as industrial and civil fuels, the utilization value is very low. In abroad, the olefin extracted from catalytic dry gas has been widely used as an important raw material source for olefin production.In China, recovery and utilization of catalytic dry gas has been started, the ethylene component extracted from it has been studied and commercial production has been put into operation. The pressure swing adsorption technology is adopted in 30000Nm3·h-1 dry gas concentrated ethylene plant of Sinopec Beijing Yanshan Company to separate each component of the catalytic dry gas, to extract the component over C2 so that the concentrated ethylene gas product is obtained, and it is sent to ethylene plant as raw material. The ethylene recovery rate of catalytic dry gas by this technology can reach over 85% , ethylene content of the product is 43 %～45 % , ethane content is 27 %～30 % , propylene content is 15%～18% . Ethylene is obtained through cracking of ethane in the product, propylene is separated and sent to propylene plant as raw material, and thus economic value of catalytic dry gas is greatly increased.The concentrated ethylene gas obtained from pressure swing contains impurities like H2O,H2S,CO2,O2 and H3As, the existing of these impurities is a great harm to operation of ethylene plant, it shall be removed through refining process. The dry gas concentrated ethylene plant utilizes the advanced technology like adsorption and sulphur removal by lean liquid, adsorption and arsine removal by arsine removal agent, oxygen removal by catalytic, CO2 removal by alkaline washing, and water removal by temperature swing adsorption, thus harmful impurities in the concentrated ethylene gas can be removed and qualified ethylene product gas to meet ethylene demands can be obtained.