Vacuum Pressure Swing Adsorption For The Treatment Of Acetone Vapor On Hypercrosslinked Polymeric Resin

Nowadays adsorption for gas separation and recovery of volatile organic compounds (VOCs) has been recognized as a preferred method due to its simple process, low investment and resource recovery. Temperature swing adsorption with steam and pressure swing adsorption process are two most commonly used techniques for VOCs adsorption. Compared to temperature swing adsorption with steam, pressure swing adsorption process can recovery water-soluble VOCs by condensation process, with low energy consumption and none secondary pollution. With stable mechanical strength, controllable pore structure and excellent adsorption-desorption performance, hypercrosslinked polymeric resin has gained more attention in the adsorption of VOCs. In this paper, hypercrosslinked polymeric resin HCP-001 was selected as an adsorbent and acetone which was commonly used industrial water-soluble organic solvent was selected as adsorbate. The performance of pressure swing adsorption was carried out on hypercrosslinked polymeric resin. The main contents and results are as follows:(1) Column adsorption-desorption apparatus was used to study the isothermal pressure swing adsorption performance of acetone on hypercrosslinked polymeric resin HCP-001. The results showed that the adsorption amount of acetone on HCP-001 increased with the increase of the inlet concentration of acetone and decreased with the increase of adsorption temperature. There were some important factors affecting the efficiency of vacuum desorption including vacuum degree, desorption temperature and the inlet concentration of acetone. The higher degree of vacuum, the higher desorption efficiency was. The desorption efficiency at 98kPa of vacuum pressure was 25.3% higher than at 90kPa. High desorption temperature is conducive for acetone desorption.The desorption efficiency at 60℃ reached 85.3% and increased 53.3% compared to the desorption efficiency at 30℃. The higher the initial inlet concentration of acetone, the higher desorption efficiency was. Because the adsorption of low inlet concentration acetone mainly located in the micropores of HCP-001 while higher inlet concentrations of acetone not only located in micropores but also mesopores. Due to the stronger adsorption potential of micropores, the acetone adsorbed in mesopores was easier to be desorbed compared to micropores which led to the higher desorption efficiency of the resin with higher inlet concentration of acetone. The time interval between two operations of adsorption and desorption had a certain impact on the desorption that the longer time interval, the lower desorption efficiency was, mainly because the acetone adsorption on the resin HCP-001 was mainly controlled by the pore diffusion. The acetone molecules adsorbed in the resin continued to diffuse to the adsorption sites of micropores with stronger adsorption potential and strong adsorption potential led to decreased desorption efficiency and desorption rate. In addition, the comparative study of the desorption characteristics of purging nitrogen was carried out. When the amount and temperature of purge gas increased, the desorption efficiency and desorption rate would be higher. Hot purging nitrogen got higher desorption efficiency than vacuum desorption, but the concentration of acetone desorbed was low that was not conducive to the subsequent condensation recovery.(2)The adiabatic pressure swing adsorption apparatus was used to study the adiabatic pressure swing adsorption performance of acetone vapor on hypercrosslinked polymeric resin HCP-001. The results showed that higher adsorption acetone concentration led to shorter the breakthrough time and higher temperature rise in fixed bed. During the vacuum desorption process the desorption efficiency was lower when the higher concentration of acetone was adsorbed, which was due to the temperature in the fixed bed during the desorption process would be lower when the higher concentration of acetone was adsorbed. The higher the degree of vacuum, the higher the desorption efficiency and the higher the concentration of the desorbed acetone were. Furthermore, the desorption characteristics using the purging nitrogen was studied. When the amount and temperature of purging gas increased, the desorption efficiency would be higher. However, compared to the vacuum desorption, desorption using purging nitrogen would get higher desorption efficiency, but the concentration of desorbed acetone was lower which was not conducive to the subsequent condensation recovery.(3) For improving conventional vacuum pressure swing adsorption process, vacuum pressure swing adsorption with purging gas and heat exchanger was carried out, respectively. The results showed that the improved process combined purging gas with vacuum pressure swing could enhance the adsorption-desorption process. The desorption efficiency of "vacuum desorption with intermittent purging nitrogen ","First vacuum+ After purging" and "First purging +After vacuum" was higher than vacuum desorption. The "vacuum desorption with intermittent purging nitrogen" got the highest desorbed acetone concentration and the highest desorption efficiency, and the desorption efficiency was 28.91% higher than vacuum desorption. During the experiment with heat exchanger, the heat exchanger in fixed bed improved the efficiency of adsorption and desorption that the maximum temperature rise in adsorption reduced 3.8℃ with the heat exchanging of 20℃ cooling water cycling and the adsorption breakthrough adsorption capacity of HCP-001 increased. With the cycling of 60℃ hot water during the desorption, the desorption efficiency increased about 10% compared to no heat exchanging desorption.