Behavior Research On Adsorption Of VOCs By Activated Semi-coke

Gas-solid adsorption is widely used in industrial production and waste gas treatment. Most of absorption material in this field is activated carbon, relatively, few for semi-coke. Semi-coke is the pyrolysis product of coal in the temperature range of 600～700℃. Compared with the coke, semi-coke's uncompleted pyrogenation products have well-developed porous structure and better organic gases adsorption capacity. However, the gas adsorption capacity of original semi-coke is limited, so it is necessary to improve its adsorption properties by physical and chemical treatment. This process is known as the activation of semi-coke.The technology of gas-solid adsorption was not usually used in a simple component (adsorbate) absorbption, but for the mixture of several gases. So the design of the adsorption process would take into account the adsorption amount of each gas component and the total components. It is so complicated if the equilibrium data have to be experimental determination for each adsorption process. It is necessary to set up a theoretical prediction model for multi-component adsorption. In this paper, three types of prediction models on gas adsorption had been used to calculate the equilibrium data for two-component systems and three-component systems. The mixture of gas was made up of n-hexane, toluene and xylene. One of the models is Extended Langmuir (E-L) model, which is representative for extension of pure component isotherm. The other one is Ideal Adsorbed Solution Theory (IAST), which is representative for the classical thermodynamic theory. The last one is Dubinin-Radushkevich (D-R) model, which is representative for the adsorption potential theory. The adsorption amounts of calculation were compared with the experimental data. The kinetic models about the activated semi-coke adsorption for volatile organic compounds were established. Furthermore, the activity of VOCs adsorption on the activated semi-coke can be studied and semi-coke adsorbent was evaluated.The research results showed that:the adsorption curves of two components or multi-component of n-hexane, toluene and xylene were changed significantly compared to the single component. Because of competition and interference of components, the outlet concentration happened to jump up at a certain degree which related to polarity and input concentration of each component. The weaker polarity it was, the higher outlet concentration jumped up. And the higher input concentration it was, the lower level jumped up. Moreover, the jump up phenomenon decreased obviously, even disappeared, when the input concentration of the component surpassed the superior level. Generally, the total capacity calculated by three models was good fit with the conclusions of experiments. The minimum average relative error (ARE) was 5.12 percentages, which happened to mixture gas of n-hexane and toluene calculated by E-L model. The maximum ARE was 15.23 percentages, which happened No. c experiment of three components calculated by D-R model. No matter for the two-component or three-component gas adsorption system, the prediction of E-L model was the best as a whole, but there was a large error in the results of IAST and D-R model prediction. Form the error analysis of the calculation data, it can found that the error of component's prediction had a decreasing tendency with its input concentration increasing.