Study On Adsorption And Desorption Of VOCs With Activated Carbon

Toluene, Ethyl ketone, Ethyl acetate and N,N-Dimethyl acetamide are the most widely used solvent in China. VOCs (Volatile Organic Compounds) is volatilized into ambient air during their application, which do harm to human's health and environment seriously. It is necessary to deal with or reclaim these VOCs vapor.The adsorption and desorption of several different boiling point VOCs, such as Toluene, Ethyl ketone, Ethyl acetate and DMAC with GAC (Granular Activated Carbon), and following condensation recover process are researched in this thesis. The basic data of adsorption and desorption for various contamination on GAC are acquired in this study, which provide reliable design criterion for the adsorption and desorption process in industry. Mensuration of the High Temperature adsorption isotherm is one of the brightness in this study, for there is few reports on the test of higher temperature adsorption isotherm, and the higher temperature adsorption isotherm is important to desorption process.The results of study on the dynamic adsorption of the four VOCs shown that, with the settled input concentration and superficial velocity, the shape of breakthrough curves are similar in general. With the larger input concentration and the higher superficial velocity, the breakthrough curve slope in center of the MTZ (Mass Transfer Zone) is larger, the breakthrough time is shorter. Ordinarily, the higher the boiling point of the VOCs, the higher the GAC adsorption capacity, the shorter of the MTZ. The GAC adsorption capacity of DMAC, is about 0.40, the highest in the test, toluene is about 0.16-0.24, Ethyl ketone or Ethyl acetate is about 0.08-0.18. The MTZ height of Ethyl ketone or Ethyl acetate, toluene anf DMAC is about 8～14cm, 6～10cm and 5～8cm respectively. The adsorption capacity decreases with increasing temperature, toluene adsorption capacity is 0.17～0.23 in 50℃, 0.08～0.14 in 100℃, 0.05～0.07 in 150℃. The adsorption isotherm can be representeded by Frundlich or Langmuir equation and it can be deduced by adsorption potential theory.Hot air purge is used to study the desorption performance of GAC to VOCs, which shown better desorption performance. For toluene or Ethyl acetate, the operation parameters for 150g GAC is applied 10.5m~3/h recycle gas flux more than 120min at 120℃. The desorption gas containing middle or high boiling point VOCs can be recovered easily by condensation. It is more economical to burn the desorption gas containing low boiling point VOCs. Finally, a solvent recovery system of 65000m~3/h was designed and evaluated, in which energy consumption is optimized by pitch analysis technique.