Research On VOCs Regenerative Catalytic Combustion Process

Volatile organic compounds（VOCs）are a kind of important pollutants emitted in industry and are harmful to the environment and human health.According to some policies issued by the state,effective treatment of VOCs is an important part of controlling environmental pollution.At present,the use of thermal storage catalytic combustion reactors to mineralize VOCs is a kind of relatively common technology.However,the thermal storage catalytic combustion equipment cannot detect the temperature of the catalytic section VOCs gas and the catalyst solids.The effects of"flying temperature"and"extinguishing"on the reactor cannot be eliminated.In this paper,a combination of thermal storage catalytic combustion experiments and mathematical models is used to study the process of VOCs thermal storage catalytic combustion.The experiment provides the basis for the model and the model optimize experiment data.Optimal reactor operating conditions are explored.Firstly,experimental research is conducted on the thermal storage catalytic combustion of VOCs.In this part,inert pellets loaded with precious metals of platinum and palladium are used as catalysts.Ceramic balls are used as heat storage material in the heat storage section.The removal rate curve of the thermal storage catalytic combustion equipment under single VOCs intake and mixed intake and the axial temperature change curve of the bed are investigated in detail.The experiment mainly investigated the effects of different switching cycles and treatment flows on the catalytic combustion of ethyl acetate.It is determined that the switching period of the thermal storage catalytic combustion equipment is 120 minutes and the processing flow rate is 20 L/min as the optimal operating conditions.Under these conditions,the VOCs removal rate reached99%.The bed temperature is around 500℃,which will not cause catalyst sintering deactivation.The self-heating rate of the reactor was calculated,and it was proved that the reactor can run self-heating without supplemental heat.Under the optimal conditions,the thermal storage catalytic combustion of xylene and methyl ethyl ketone is studied.The removal rate reached above 95%,and the bed temperature reached about 400°C.Three kinds of organic compounds mixed catalytic combustion show that the removal rate is97%,and a good removal effect is also achieved.Subsequently,the model research of the thermal storage catalytic combustion reactor is carried out.According to the structure and reaction characteristics of the thermal storage catalytic combustion reactor,a mathematical model of the reactor was established.The accuracy of the model is verified first.Afterwards,the influence factors such as the inlet concentration of ethyl acetate and xylene,the preheating temperature,the length of the heat storage section of the reactor and the length of the catalytic section are modeled.The results show that under the conditions of 0.85 to 1 times the original,the removal rate of ethyl acetate gradually increased up to 99%.The pre-heating time is gradually shortened to save energy.The optimal intake concentration of xylene is Y₀=6680 mg·m^-3.The temperature of the solid catalyst is below 550℃.The catalyst does not sinter.The reactor is capable of stable operation.When the concentration of ethyl acetate is 0.5 times of the original,the preheating temperature range is 100～180℃.The concentration is 0.7 times of the original,and the preheating temperature range is 100～125℃.The removal rate reach about 99%with the increase of temperature.The xylene gas concentration is 0.5times the original preheating temperature at 100～350℃.The concentration is 0.7 times,and the preheating temperature is in the range of 100-280℃.The temperature increased,and the removal rate was above 95%.When the fixed length of the reactor is 2 m,the optimal distribution of ethyl acetate is 0.5～0.6 m in length of the heat storage section.When the length of xylene heat storage section is 0.4～0.5 m,the removal rate is 95%～99%.The temperature is between 400～450℃.The catalyst will not be deactivated by sintering.It is also the optimal temperature for the reaction.This paper provides a more accurate quantitative standard and theoretical basis for the industrial application of thermal storage catalytic combustion treatment of VOCs.