Study On Process Technical Modification Of Dehydration From Acetylene Gas In PVC Production

Dehydration from acetylene gas in PVC production is an important industrial process.It is hard for the current process to reduce the water content in acetylene gas to less than 600ppm,which results into the acid fog,corrison in pipe and equipment,catalyst coking and shorter life time.Thus,in this thesis,we perform the study on process modification for dehydration from acetylene gas.We compared two dehydration technologies systematically,i.e.,coupled dehydration process and John-Brown dehydration process.It was observed that John-Brown technology can more effectively remove the water in acetylene gas with lower cost and without waste acid.The orginial dryer tower,with maxium absorption of 0.032t/H,can not meet the requirement for water removal.Thus,we designed and added a new cooling pre-dehydration unit to control the acetylene gas in the range of 0-5?,and a new on-line-switch de-fogger.To solve the problem of molecular sieve carbonization in John-Brown process,we re-screened the more suitable 3A molecular sieve,with pore size of 2.3-2.6 A,bulk density?0.68 g/ml,compressive strength?114,water absorption ratio>21.7%and static absorption of ethylene<1.4%,which solve the problem of molecular sieve selection and life time.The industrial results of the dehydration process in three-year-continuous operation indicate that,compared with coupled dehydration process,John-Brown process can save the operation cost of 3.5544 million yuan/a,reduce the heavy-component waster of 360t/a and the waste acid of 2190m3/a.This technical modification brings a remarkable economic profit and reduces the environment problems.