Experimental Study On Recovery Of Dimethyl Butane From Waste Gas By Molecular Sieve Adsorption Method

As a key development area of the chemical industry,the silicone material processing and petroleum smelting industries often need to produce and process large amounts of dimethylbutanes,which can also easily lead to excessive emissions of typical VOCs such as dimethylbutane,methyl chloride and aromatic hydrocarbons.Among them,the amount of dimethylbutane is large and the harm is serious.It is necessary to find an efficient and economical target waste gas treatment method,otherwise,in the context of"winning the battle to defend the blue sky",the atmospheric environment would be deteriorative and the dimethylbutane would be lost,which is not conducive to the healthy development of silicone materials and petroleum smelting enterprises.As a green and environmentally friendly treatment method,the adsorption recovery method is one of the hotspots in current research and is widely used in the field of environmental governance and industrial impurity removal.In this paper,the exhaust gas containing 2,2-dimethylbutane in a certain enterprise was regarded as the research object,and the adsorption and recovery effect of 6 kinds of adsorbent on 2,2-dimethylbutane in exhaust gas is compared through experiments,and the best adsorbent was selected;through the single factor static adsorption test,orthogonal test and dynamic adsorption test were carried to determine the best adsorption parameters;then,four recovery methods for the dimethyl butane were analyzed and compared,the service life and loss status of molecular sieve were discussed.The main results of this article as follows:?1?Screening of 2,2-dimethylbutane molecular adsorption materialsThe adsorption efficiency of 2,2-dimethylbutane molecules by six materials was compared.The results showed that the adsorption performance was M-13X>Porous resin>13X>activated carbon>3A>4A.M-13X molecular sieve was the best adsorbent.Under the circumstance of 60%filling ratio,20 min adsorption time,0.05 MPa adsorption pressure and 50?,it can ensure that 2,2-dimethyl Butane molecular adsorption efficiency reached 42.72%.The adsorption efficiency of M-13X molecular sieve for 2,2-dimethylbutane gradually increased with the increase of temperature and basically stabilized at 70?;its adsorption efficiency gradually increased with the increase of adsorption time,at28min The adsorption efficiency is basically stable;its adsorption efficiency gradually increased with the increase of adsorption pressure,and basically stabilizes at 0.20MPa;its adsorption efficiency gradually increased with the increase of the filling ratio,and basically stabilizes at a filling ratio of 60%.?2?Determination of the optimal adsorption parameters of M-13XThrough Box-Behnken design orthogonal test of 29 groups with 4 factors and 3levels,the results showed that the optimal adsorption process parameters were 70?,60%adsorbent filling ratio,30min adsorption time,and 0.2 MPa adsorption pressure.The removal rate of 2,2-dimethylbutane reached 58.33%?Design Expert model simulation value was 58.15%?.The study finished the first dynamic adsorption curve of the original M-13X molecular sieve,which is based on the optimal combination of adsorption conditions?70°C temperature,60%filling ratio,30min adsorption time,0.2MPa adsorption pressure?,and the effective action time is 28min;In addition,combined with the calculation of molecular sieve saturation adsorption capacity formula,it can be known that the saturation adsorption capacity of M-13X molecular sieve for2,2-dimethylbutane is 10.8mg/g.?3?Recovery of dimethylbutane and regeneration of M-13XThe four regenerative recovery methods sort the recovery efficiency of dimethylbutane as follows:ultrasonic alcohol washing and hot baking method>hot air blowing method>high temperature heating method>variable pressure desorption method.The parameters of the best recovery method are:15%ethanol mass fraction,20?elution temperature,10 min elution time,40%ultrasonic power.The recovery efficiency of this method can reach 94%,and the adsorption performance of molecular sieve is superior;through the"adsorption-regeneration-adsorption"test,it is found that M-13X is subjected to"alcohol washing and drying".After regeneration,the number of reusable times is about 26;in terms of molecular sieve regeneration loss,the overall mass loss is about 0.38 g/g.The cause of the loss may be the collision caused by the ultrasonic vibration during the alcohol washing of the molecular sieve,and the material damage that may be caused during the high temperature drying process.?4?Construction of molecular sieve adsorption processThe research designed the bypass adsorption purification process,which is based on the"hot air pump-alkali-modification system-adsorption tower-regeneration device"process,it could control the temperature,packing ratio,adsorption pressure and adsorption duration;Bypass purification process designed for the secondary adsorption unit,6 adsorption towers constructed three parallel adsorption routes,two for using and one for preparation;the modification liquid of this process consists of NaOH solution?4.5 mol/L?and NH₃·H₂O solution?0.5 mol/L?.Which is prepared by alkali modification system according to the volume ratio of 1:1.The modification system contained a high temperature hot drying device;both ultrasonic cleaning and hot drying could achieved by the recovery device,and the best recovery liquid percentage is 15%,which could achieve the recovery of dimethyl butane and molecular sieve regeneration.