| Thermal effect during dynamic adsorption process widely exists in the real industrial adsorption. Since the actual operating environment is closed and difficult for heat dissipation, the heat of adsorption can cause a dramatic increase in the temperature of adsorption bed, so as to give a negative impact on adsorption and the safety of the equipment. Hypercrosslinked polymeric resin which has good adsorption, desorption properties, is one of the important adsorbent for VOCs adsorption treatment. In this paper, The commonly used organic solvents 1,2-dichloroethane was selected as adsorbate to study the thermal effect during dynamic adsorption on hypercrosslinked polymeric resin and its mitigation measures. The results are as follows:(1) In the adiabatic adsorption experiments, the temperature increment of the adsorption bed composed of hypercrosslinked polymeric resin NDA-150 was obvious, and the maximum temperature rise reached 50.0℃ when the inlet concentration of 1,2-dichloroethane was 200 mg/L. Within the scope of the inlet concentration in this study, there was a good linear relationship between the highest temperature rise and inlet concentration, and the linear correlation coefficient was 0.96. Compared the adiabatic adsorption experimental data with the data of isothermal adsorption, it is found that the temperature rise in the process of adsorption had obvious inhibitory effect on the adsorption process. Under the condition of different inlet concentration of 1,2- dichloroethane, the adsorption capacity of adiabatic adsorption process all had varying degrees of decline when compared to the adsorption capacity of isothermal adsorption. When the inlet concentration of ethylene dichloride was 50mg/L, 100mg/L, and 200mg/L, the adsorption capacity was decreased by 2.4%,17.0%, and 30.6%, respectively. At the same time, the adsorption rate constant also fell.(2) The thermal effect of different resin combination during the adsorption process was carried out. The results showed that the adsorption heat caused by resin NDA-1800 was much less than that caused by resin NDA-150 and the resin NDA-1800 could relieve the temperature rise surrounding, so the temperature increment of the resin NDA-150 closed to resin NDA-1800 was less than that of the resin NDA-150 without resin NDA-1800 nearby. And the more evenly two kinds of resin mixed, the greater relief of the thermal effect it caused. Piled up in the condition of pile up and down, stacked one by one, all mixed pile, the adsorption process of highest temperature were 40.6℃,40.1℃ and 37.6℃, the adsorption capacity followed by 260 mg/g,285 mg/g and 305 mg/g, and the adsorption rate constant were 0.119 min-1,0.122 min-1 and 0.134 min-1.(3) The influence of initial moisture content to exothermic effects during the adsorption process was studied. As the initial moisture content of 0%,9.1%,16.7%, 23.1%,28.6%, and 33.3%, the highest temperature of adsorption process were 45.7℃,18.2℃,12.2℃,7.3℃,4.8℃, and 5.4℃, respectively. This relief of temperature increment in the adsorption process was due to desorption and evaporation of the initial water. Through the fitting of Yoon-Nelson equation for the breakthrough curve, it was found that with the increasing of moisture content, breakthrough adsorption capacity and adsorption rate constant showed an initial increase before the reduction, When the initial moisture content was 16.7%, the highest adsorption rate constant reached 0.254 min-1. When the moisture content was 23.1%, the highest adsorption capacity was 600 mg/g. The results showed that the initial moisture content could relieve the temperature increment caused by the adsorption heat, on the other hand, water molecule also occupied the adsorption sites of 1,2-dichloroethane and hindered its adsorption. |
PDF Full Text Request