Research On Adsorption To Recover Ethylene From Off-gas Of Ethylene Oxide Plant

For the purpose of recovering ethylene from industrial off-gas of ethylene oxide equipment by pressure swing adsorption (PSA), three different adsorbents, activated carbon, self-made NJ and NK adsorbent were researched. The research focused on the adsorptive capacity for ethylene, selectivity for ethylene/ethane separation, effect of each main component on the PSA performance for ethylene of different adsorbents and regenerative performance of the adsorbents.Static adsorption isotherms of each monocomponent of the industrial off-gas were measured on the NK adsorbents by OMNISORPTION 100CX surface and voidage measuring instrument. It showed that the adsorption amount for C₂H₄ on the adsortent(NK) is 1 ml ? g^-1. The adsorption equilibrium data of ethylene and ethane could be properly fitted by the models considering respectively physical adsorption and chemisorption. It had good consistency between model calculated value and experimental result.A single-column measurement equipment for dynamic adsorption was set up to study the PSA performance of the adsorbents by simulating the composition of industrial off-gas.It showed from the dynamic adsorption experiments for multicomponent gas mixture that if under the same condition, the adsorbed amount of ethylene on activated carbon was the most, but its selectivity for ethylene was the lowest among the three, which was under 1.0. The NK adsorbent had a better selectivity for ethylene than the other two adsorbents did. Also, the stability of the NJ adsorbent for PSA cycles was the best. The feasibilities for industrial application of the two complexation adsorbents, NJ and NK, on recovery of ethylene from ethylene oxide off-gas by PSA were studied. As we could see from the results that the adsorbed amount of ethylene from industrial off-gas on these two complexation adsorbents was almost the same, while the NK adsorbent had greater PSA stability, pressure swing regenerative performance, and higher gas concentration by desorption, which was better for industrial application. The NK adsorbent could be successfully regenerated by purging of inert gas.According to the experimental results, the methodology for recovery of ethylene from the off-gas of ethylene oxide equipment was initially designed to select the appropriate PSA operation flowchart. It showed from the feasibility study for industrial application that the recovered ethylene was pure enough and the percent recovery was high. Compared to other methods, the recovery of ethylene by PSA had a marked economic effectiveness.