| The catalytic dry gas is a kind of by-product of catalytic cracking,composed of C1 and C2 produced during catalytic cracking,CO and CO2 produced by coke combustion,and air etc.Light hydrocarbons and hydrogen in the dry gas is of high usable value.Excessive amount of C3+in dry gas will greatly affect the total fluid of the device and also be harmful to the economic benefits of refineries and bring adverse effects to the operation of styrene device.In Qingdao refining catalytic cracking unit,the dry gas is commonly with C3+due to the shortage of absorptive capacity of absorption tower.In order to reduce the content of C3+in catalytic cracking unit dry gas,the investigations,including the processing technology of absorbing tower and desorption tower,the system renovation based on the ASPEN simulated operating condition,are necessary.Instead of original design that all crude gasoline flow into the absorption tower from the 36th layer tray,we let 30%crude gasoline flow into the absorption tower from 36th layer tray and other 70%from the 17th layer tray and the supplement absorbent still flow into the absorber from41layer tray.We changed the tray opening rate of 1st to 10th layer to 11.7%;11th to 41st layer tray remains unchanged;11th to 17th layer to 9.5%according to the change of flow intensity;18th to 41th layer to 7.3%.Desorption tower improve the structure of double overflow relief form and increase the total length of the side weir and dam in general to achieve the purpose of better desorption.Through the actual operation situation,we found that after modification C3+volume fraction reduced to 2.3%from 4.9%（control target of 3%）.The modifications fully meet the requirement of high load and high standard operation. |
