Study On Hydrogen Sulfide Removal By Rotating Packed Bed From Viscose Fiber Waste Gas

Viscose fiber,one kind of renewable celluloses,has been widely applied in apprel industry due to its excellent breathability,hygroscopicity,dyeability and spinnability.Because carbon disulfide is used as solvent,a large amount of hydrogen sulfide(H2S)is generated from the production process of viscose fiber.Large emission of H2S not only causes environmental pollution,but alsois harmful to human's health.However,H2S can be recycled as a kind of resource to generate sulfur-containing chemicals,which eases the environmental problems and offsets the shortage of sulfur resource in China.Therefore,it is necessary to investigate the treatment technology of the waste gas from viscose fiber production.Nowadays,packed towers are widely used for waste gas scrubbing from viscose fiber production,But this device mainly suffers from the drawbacks of large equipment size and low treatment capacity per unit of devic,and many interprises are faced with a shortage of space when upgrading equipments to meet increasingly stringent emission standard.Rotating packed bed(RPB)has many advantages in enhancement on mass transfer and micromixing,and has been widely adopted for acid gas treatment process.In this work,Na2S solution was used for H2S absorption to prepare sodium hydrosulfide(NaHS)and elemental sulfur.In order to obtain NaHS product,a two-step desurfulization process was established,which treated with 2%H2S and 1000ppm respectively.The effects of operation conditions,including rotation speed,liquid flow rate,gas flow rate and liquid composition,on removal efficiency were systematically investigated.The experimental results showed that,during the primary desulfurization,a liquid product containg 0.25%Na2S and 18.8%NaHS can be obtained under the conditions:initial Na2S concentration of 15%,liquid-gas ratio of 10 L·m-3,temperature of 308 K,rotation speed of 1200 rpm,H2S inlet concentration at 2%.Under these conditions,the pH of liquid is 13 and H2S concentration in RPB outlet can be lower than 1000 ppm.During the secondary desulfurization process,a mixed solution containg Na2S and NaHS was used to absorb 1000ppm H2S,and H2S concentration in RPB outlet can be lower than 10 ppm under the conditions:liquid-gas ratio of 8 L·m-3,temperature of 308 K,rotation speed of 1200 rpm.In the aim at preparing elemental sulfur,the effecs of operation conditions,mainly including rotation speed,liquid flow rate,NaHS concentration,gas flow rate and H2S concentration,on removal efficiency and overall gas-phase volumetric mass-tranfer coefficienct were systematically investigated.The order of significance of aboved conditions on regeneration performance was further explored.Results show that:both removal efficiency and KGa first increase and then become constant with an increase in rotation speed,liqud flow rate and NaHS concentration,but decrease with increasing gas flow rate and H2S concrntration;however,KGa first increase and then become constant and removal efficiency decreased with an increase in gas flow.Removal efficiency higher than 99%can be obtained under the optimal conditions for preparing element sulfur:sodium sulfide concentration of 10 g·L-1,rotation speed of 1400 rpm,liquid gas ratio of 8 L·m-3,and temperature of 308 K.The order of significance of regeneration are:regeneration time,liquid flow rate,gas flow rate;additionally,a empirical correlation of KGa was obtained using multivariate linear regression method on the basis of experimental data,and the calsulated results agree well with experimental data with a deviation within ±15%.Finally,we designed a desulfurization process for treating viscose fiber waste gas with a treatment task of 8.0×104 Nm3·h-1.Meanwhile,material balance and heat balance were performed,and a design of RPB devices was also given.