Test And Optimization Of Spray Absorption-Fenton-Photocatalysis Combined Process In Vocs Removal

In order to effectively purify the volatile organic compounds?VOCs?in the air,a company in Shenzhen has proposed a combined process consisting of absorption method,Fenton method and photocatalytic method,and made an engineering prototype.In this study,typical water-soluble VOCs acetone and non-water-soluble VOCs toluene were treated as objects.The performance test and analysis of the combined process were carried out,and the existing problems were optimized.Then the purification performance of the optimized combined process was tested.The existing engineering prototype system was used to investigate the removal effect of combined process and single process on toluene and acetone,and the problems found in the combined process were analyzed.?1?The Tween 20 aqueous solution has a poor absorption effect on toluene,and a large amount of foam is generated during the absorption process to cause adverse effects such as secondary pollution.?2?The iron filings in the electric Fenton spray tower generate a large amount of rust during use and cause the H₂O₂ to decompose ineffectively,and the spray tower is not suitable as a Fenton reactor for treating water-insoluble toluene.?3?The amount of catalyst in the photocatalytic device is small,and the reaction residence time is short.In order to solve the problems existing in the combined process,an optimization scheme is proposed.?1?An absorbent with good absorption effect is prepared.After comparing and selecting sodium citrate,Tween 20,sodium dodecyl benzene sulfonate,LF901 and X80 in a small test device,based on the LF901 aqueous solution A new absorbent?10%LF901+1%n-hexanol+89%water?has been formulated.The absorbent has a saturated absorption of 0.40 mg/g for toluene under the conditions of toluene concentration of 100 ppm,absorbent volume of 100 m L,and intake air flow of 200 m L/min.?2?Use the traditional Fenton method instead of the electric Fenton method.Through a small test spray tower,the molar ratio of Fe²⁺ to H₂O₂ concentration is 1:4 when the treatment effect of 200 ppm of acetone reaches 94.1%.Using a small test bubble column to treat toluene waste gas,under the conditions of Fe²⁺ concentration of 1.2 mmol/L,H₂O₂ concentration of 6.0 mmol/L,p H of 3,and flow rate of 200 ml/min,the maximum removal effect of 100 ppm toluene is 91.9%.?3?A highefficiency photocatalyst plate was fabricated and its performance was investigated in a small photocatalytic device.At a flow rate of 200 ml/min,an oxygen concentration of 21%,a humidity of 75%,a toluene concentration of 10 ppm,a catalyst When the amount is 15 tablets,the degradation rate and mineralization rate of toluene reach 92.6% and 79.6% respectively,which is 11.5% and 13.4% higher than the catalyst in the original photocatalytic device.The purification performance of the optimized single process and combined process for toluene and acetone was tested.?1?The new absorbent is used in the absorption process.Under the conditions of air volume of 500 m³/h,liquid-gas ratio of 5 L/m³ and absorbent of 300 L,the removal rate of 100 ppm toluene is up to 78.2% It is about 50% higher than before optimization,and the absorbent will not generate a lot of foam during use.?2?Fe SO₄ and H₂O₂ were added according to the molar ratio of Fe²⁺ to H₂O₂ concentration of 1:4.When the p H of the spray solution was 3,the dosage of FeSO₄ was 10 kg,the dosage of H₂O₂ was 15 L,the air volume was 500 m³/h,and the liquid-gas ratio was 5 L/m³,the Fenton spray tower had an The highest removal rate was 93.0%,which was 19.2% higher than the removal rate of pure water absorption.Under this condition,its toluene removal effect reached nearly 26.5%.?3?3 self-made catalyst plates are added to the photocatalytic device.Under the conditions of air volume of 500 m³/h,toluene concentration of 15 ppm,and acetone concentration of 50 ppm,the removal rates of toluene and acetone by the photocatalytic device are 11.2% and 5.6%.Compared with before optimization,the improvement is lower,1.9% and 1.4% respectively.?4?The combined process treats the mixed waste gas of toluene and acetone under the optimal conditions of each process,and the removal rate can reach up to 83.9%.Compared with before optimization,the treatment effect was improved by 28.7%.