Carbon-based Meterals For Adsorption And Electro-thermal Desorption VOCs

Volatile organic compounds(VOCs) is received more and more attention after the SO2 and NOX atmospheric pollutants, which form photochemical pollution by reacting with NOX and smoke,which is the main cause of haze and other complex atmospheric pollutants in the city.The adsorption is a widely used technique in the industry to eliminate VOCs for its operation simply, low cost, high efficiency currently.Activated carbon is the widely used adsorbent at present, but its development has been limited by some drawbacks such as fire risk, pore clogging, hygroscopicit y and a lack of regenerative ability. Therefore,The activated carbon fiber as a new type of carbon-based adsorbent for its high specific surface area, large pore volume, pore rich and conductivity gained more and more applications in VOCs governance.First, the effect of adsorption conditions such as VOCs,concentration, bed temperature and different humidity on adsorption ability were investigated over The activated carbon fiber ACF1,ACF2,ACF3. The results showed that ACF2 which own high specific surface area and large entrance have best performance for thoseVOCs, adsorption capacity of toluene can be achieved 318.3 mg/g.Concentration drove greatly on the adsorption of VOCs, which under high concentration reached 434.8mg/g of toluene. The adsorption of toluene on activated carbon fiber is less affected by temperature which still had 288.3 mg/g adsorption capacity at 60℃.Secondly, the adsorption equilibria of ethanol vapor onto activated carbon fiber and activated carbon were investigated by the dynamic adsorption method at the temperature of 303 K, 318 K and333K and calculated the heat of adsorption by model fitting adsorption isotherm. The results showed that: ① The adsorption process of two kinds adsorbents adsorbing toluene is both rapidly rising at low pressure region because of their rich microporous, but activated carbon fiber showed better performance at low-temperature high-pressure region. ② The heats of adsorption from Clansius-Clapeyron equation show that the heats of activated carbon fiber are lower than that of activated carbon fiber which can effectively prevent the adsorption bed runaway, more security. ③The Yoon-Nelson model is good to fit the breakthrough curves of granular activated carbon and activated carbon fiber, and the model parameters obtained from the experimental data not only could describe the adsorption process but also predict the breakthrough curves correctly.There are many problems in water vapor regeneration ofactivated carbon fiber desorption such as slow heat transfer, long desorption time, we consider the resistance of the activated carbon fiber itself, joule heat generated by the current, so that activated carbon fiber heating regeneration itself. Thesis investigated performance of electro-thermal desorption activated carbon fiber under different voltage. The results show that, the greater the voltage, the faster the activated carbon fiber heating rate, the higher the desorption efficiency, What’s more, 100 min later toluene can fully desorption. At the same time activated carbon fiber still has good adsorption performance, saturated adsorption amount still can reach more than 80% of the original adsorption quantity after four cycles.