Research And Development Of VOCs Adsorption Process

In the process of petrochemical production,VOCs(volatile organic compounds)are usually produced.If they are not treated,they will pollute the environment and threaten human health.They are not in line with the concept of green development in the current society and are not conducive to the construction of an environment-friendly society.Therefore,how to effectively manage VOCs has become an important issue in today's society.Adsorption is one of the most widely used and common methods nowadays.The cost of VOCs treatment by adsorption is low,the adsorption effect is good,and it is not easy to generate by-products in the adsorption process.It is of great significance to simulate and optimize the adsorption process.Aspen Plus is a general large-scale simulation software at present.There are a large number of models which can be applied to various process simulation,but it still lacks some unit operation models,such as adsorption process.Adsorption process is a dynamic process,there is no suitable software to calculate at present.In this study,the adsorption model is established,and the software is programmed,embedded in Aspen calculation software,which is convenient for users to use.In this paper,the adsorption process is simulated and optimized.The raw material is 10000 Nm~3/h paint factory waste gas.Based on the user 2 module of Aspen Plus,the VOCs adsorption model is compiled by VBA language,and the flow field of the adsorber is simulated.The adsorption model can calculate the relationship between VOCs outlet concentration and time from the transfer equation by setting parameters such as bed,adsorbent,temperature,pressure,feeding conditions,Langmuir adsorption isotherm data,which is the breakthrough curve.In the VOCs adsorption process,the bed height and diameter of the model are set as 10m and 1.35M respectively.The adsorption results are calculated.After 5 days of adsorption,the VOCs concentration at the outlet of the bed is 48 ppm for p-xylene,28 ppm for formaldehyde,7 ppm for toluene and 3 ppm for benzene.According to the national exhaust emission standard,the model has met the emission requirements.The adsorption efficiency was 98.2%for p-xylene,82.3%for formaldehyde,95.9% for toluene and 95.7% for benzene.Therefore,under the recommended equipment parameters,the adsorption operation cycle of the process is set as 5 days.The temperature of the exhaust gas of the paint factory is relatively high,generally 250?,and the adsorption should be carried out under the condition of 25?,so it is necessary to add a heat exchanger to reduce the temperature before adsorption.Aiming at the heat exchanger in this process-plate heat exchanger,this article uses C#language to develop the general design software of plate heat exchanger in Visual Studio development environment.In this process,the temperature of the exhaust gas at250?is reduced to 25?,calculated by the designed plate heat exchanger:8 channels,total heat transfer area 1063.1 m~2,total heat transfer coefficient 560.2 W/(m~2·K),pressure drop 48.2 kPa.In order to find a better adsorption effect and a more suitable adsorption parameter,this paper optimizes the velocity field and pressure field with the particle size as a variable,using the flow field simulation software Fluent for the VOCs adsorber.The simulation results show that when the particle size of adsorbent is 2 mm,the gas flow is the most uniform,and a distributor on the top of the adsorber can effectively improve the problem of uneven gas distribution in the adsorber,and improve the adsorption efficiency.Under this condition,the average flow rate is about 0.28 m/s.