Experimental Study On Treatment Of Acrylonitrile Wastewater By High Gravity Air Stripping Technology

Acrylonitrile wastewater is toxic and difficult to treat. Incineration is widely used in theindustry at present. This method is characterized with the complete treatment, secondarypollution and high treatment cost. Therefore, exploring an efficient and practical acrylonitrilewastewater treatment method becomes an urgent problem. Among many methods, airstripping technology has an unparalleled advantage in the treatment of wastewater containingvolatile organic compounds, which is simple and easy to operate.Packed tower, plate tower and aeration tank etc. are commonly uesded as air strippingequipments. Acrylonitrile removal rate is low (less than20%) since that the gas-liquid masstransfer process is limited in traditional equipments. With the purpose of intensifing thisprocess and accordingly improving wastewater treatment efficiency, high gravity technologyis proposed in this paper.Firstly, mass transfer characteristics for high gravity air stripping process were studied.The influence factors were high gravity factor β, gas-liquid ratio R, liquid spray density U andinitial concentration Cinin the experiments. The correlations of mass transfer coefficients Kxaand mass transfer unit height HOLwere established. The average relative errors of correlationswere6.109%and5.356%respectively. Secondly, pressure drop characteristics were studied.The correlation of pressure drop was established, and the average relative error was4.179%.Then the treatment process of acrylonitrile wastewater by high gravity air strippingtechnology was carried out. In terms of the acrylonitrile removal rate, the most significantinfluence factor was gas-liquid ratio R, followed by liquid spray density U, and high gravityfactor β was the least. The appropriate operating conditions were ambient temperature,atmospheric pressure, high gravity factor β of50.14, gas-liquid ratio R of1300m3/m3and liquid spray density U of1.60m3/(m2·h). Under the above conditions, for the initialconcentration of （3000±100）mg/L, the single stage and three stage acrylonitrile removal rateη were69.7%and97.1%respectively, and the gap between the equilibrium concentration was2.9%. The correlation of acrylonitrile removal rate η was established and the average relativeerror was3.356%. Finally, high gravity air stripping and conventional technologies werecompared. Introducing high gravity air stripping technology, acrylonitrile removal rate η were2.6times and13times higher than traditional air stripping and stirring method. The packedlayer volume in rotating packed bed was nearly5orders of magnitude lower than that instripping column. The mass transfer coefficients Kxa increased by8times. The mass transferunit height HOLand pressure drop Δp reduced by about63times and10times respectively.Consequently, with high gravity air stripping technology, the gas-liquid mass transferprocess is intensified, thereby removal rate is improved and the volume of air strippingequipment is reduced. Gas pressure drop is decreased simultaneously. Therefore, the highgravity air stripping technology in the treatment of acrylonitrile wastewater has greatindustrial application prospects.