A Study On Dynamic Adsorption Of VOCs On Activated Carbon In The Production Of PTA

Much attention has been paid to the harmful substances, as Volatile Organic Compounds (VOCs), to prevent human beings and the environment. In this thesis, the adsorption of VOCs on activated carbons (ACs) was studied, where the VOCs were methyl acetate, acetate acid and p-xylene from the exhausted gas of pure terephthalic acid (PTA) production. The research mainly focused on the dynamic adsorption performance of three organic compounds on ACs. Dynamic gas-mixing and adsorption devices were built in this thesis. Gas chromatography was used for the quantitative analysis of organic gases, with the initial gas concentration determined by the weighting of adsorption column. The effects of concentration, flow and temperature to the adsorption performance for the VOCs on Calgon AC were investigated from the breakthrough time, adsorption capacity and shape of breakthrough curve. The competitive adsorption of binary gases was also studied. The results showed that the adsorption capacity of p-xylene on Calgon AC was more than that of acetate acid while methyl acetate was the least. The dynamic equilibrium data of methyl acetate on Calgon AC could be correlated by Freundlich equation.In the thesis, three kinds of homemade ACs were compared with Calgon AC. Under comparative conditions the dynamic adsorption of methyl acetate on these four adsorbents were compared from the shape of breakthrough curve, the breakthrough adsorption capacity and the bed use ratio. The experimental results showed that the microporous distribution had a great effect on the adsorption performance.Water vapour purge and heated nitrogen purge were used to study the desorption performance of AC. The influence of water vapour flow on the regeneration of water vapour purge was discussed, and temperature and nitrogen flow were the factors of influencing the regeneration of heated nitrogen purge. The desorption experiments for binary gases showed that methyl acetate could be desorbed easier than acetate acid while p-xylene was the most difficult to do so.Dynamic adsorption model based on the pore diffusion was built to numericallysimulate the breakthrough curves of methyl acetate under different conditions and the results were in agreement with the experimental data. It showed that the model could give the information about the design of the industrial adsorption process.