Removal of ethylene oxide from waste gases by absorption

Abstract

Ethylene oxide (EtO) is an organic compound, which is used as a starting material in the production of polymers and as sterilizing agent for thermolabile materials. Although ethylene oxide is not common as an organic pollutant, its removal from numerous emission sources (e.g., ethylene oxide production plants or food and pharmaceutical sterilizing units) is of crucial importance because of its mutagenic, teratogenic and cancerogenic effects on human health. The objective of this paper is the experimental investigation of ethylene oxide (EtO) absorption in diluted aqueous solution of sulfuric acid in order to evaluate the applicability of this procedure as well as to obtain project parameters for industrial plant realizetion. It was found that absorption is suitable as the fist step in the purification treatment of high EtO concentrations in the emission gases. According to the literature data, the basic parameter that defines the scrubber efficiency is the contact time, i.e. the ratio of packing height in the scrubber to the velocity of the gas mixture. To investigate the characteristics of wet treatment in a broad range of contact time, parts of the experimental studies were conducted in a system with two and with three scrubbers in series. The obtained experimental results show that the high degree of EtO removal can be achieved (>98%) when the contact time is sufficiently long (about 25s). The process is effective until the concentration of formed glycol in the solution reaches a value of about 20%. The process is safe and there is no danger of ignition and explosion of air and EtO mixture, although at the entrance to the scrubber EtO concentrations are significantly above the lower explosive limit.

Predmet ovog rada je istraživanje mogućnosti uklanjanja etilen-oksida (EtO) iz otpadnih gasova apsorpcijom u razblaženim vodenim rastvorima sumporne kiseline sa ciljem da se ocene mogućnosti primene ove tehnologije za projektovanje industrijskog sistema. Apsorpcija je naročito pogodan postupak kao prvi stepen prečišćavanja u slučajevima kada je emisiona koncentracija EtO visoka. Eksperimentalno je ispitan uticaj širokog opsega vremena kontakta na efikasnost uklanjanja EtO. Ulazne koncentracije EtO su varirane od 4 do 40 vol.%, a vremena kontakta od 4 do 40 s. Apsorcija je izvođena u rastvoru sumporne kiseline (H2SO4) pri čemu dolazi do hidrolize EtO u etilen-glikol. Efikasnost apsorpcije EtO opada sa povećanjem koncentracije etilen-glikola u apsorpcionom rastvoru. Rezultati eksperimentalnih ispitivanja su pokazali da se može postići visok stepen efikasnosti uklanjanja EtO (> 98%) pod uslovom da je vreme kontakta dovoljno dugo (oko 25s).