Study On Activated Carbon Hot Nitrogen Cycle Desorption VOCs In Coating Industry And Regeneration Characteristics

In order to solve the problem of VOCs emission control in small and medium-sized coating industry,chinese environmental protection departments have greatly reduced the cost of enterprise VOCs treatment through the regeneration mode of"decentralized collection and centralized treatment"of activated carbon.The process of hot nitrogen recycling-catalytic combustion has a good effect on activated carbon regeneration,but there are still some problems,such as unstable desorption concentration of activated carbon and short regeneration life.In order to solve these problems,industrial reagents were used to prepare adsorbants.Through pilot experiments simulating actual working conditions,the law of coating VOCs in activated carbon hot nitrogen cycle desorption and changes in its regeneration characteristics were studied,so as to provide reference for the practical engineering design and application of hot nitrogen cycle desorption coating VOCs.The trend of desorption concentration and rate of coating VOCs from activated carbon hot nitrogen recycling desorption was studied under different desorption temperatures.The results found that:within the desorption temperature range and time that fit the actual working conditions,toluene can achieve relatively stable concentration desorption by adjusting the heating mode,while o-xylene and mesitylene which have the higher boiling point,can also achieve relatively stable concentration desorption under this condition,but the desorption rate is not as good as toluene;however,esters are less controlled,the desorption effect of esters can reach the desorption balance at a lower desorption temperature and a short time.Meanwhile,presudo-1^st-order kinetic model,presudo-2^nd-order kinetic model and Bangham kinetic model were used to fit the experimental data of activated carbon desorption.It was found that the Bangham kinetic model had the best fitting effect whether it was fixed temperature desorption or stepped warming desorption,which can provide some reference for engineering design of hot nitrogen cycle desorption process.Based on the step-heating model,the performance changes and pore structure changes during the multiple cycles of activated carbon regeneration were studied,and the influence of pore structure on the regeneration performance was analyzed.The results showed that the optimal number of hot nitrogen cycle regeneration of activated carbon was 10 times,during which a high-temperature ageing was needed after 5 times of regeneration to maintain its high regeneration performance.When activated carbon recycles the coating VOCs,the maximum effective pore diameter of adsorption process is about 11 times that of toluene,and the maximum effective pore diameter of desorption process is about 10 times that of toluene.Meanwhile,TPD test of initial activated carbon and regenerated activated carbon were carried out,and the results showed that some components in coating VOCs had chemical adsorption on activated carbon,and these components could not effectively desorption under the process conditions of practical engineering application.As the regeneration times increased,they gradually accumulated on activated carbon,eventually leading to the gradual decline of the adsorption-desorption performance of activated carbon.Besides,the desorption activation energy of coating VOCs on the activated carbon which was used in this study is low,which proves that the mesoporous structure is more conducive to the cyclic desorption regeneration of adsorption materials.