Absorption Of Carbon Dioxide And Hydrogen Sulfide Into N-methyldiethanolamine In A High-Throughput Microchannel Reactor

Equipment miniaturization and process integration, which are the direction of future science and technology development, meet the demands of sustainable development and high-tech development. Microtechnology as a kind of novel process intensification technology has become a research focus in chemical engineering discipline, which will have broad applications in the fields of chemical industry, energy and environment and other fields. Studies have shown that microchannels with micron scale characteristics have a high gas-liquid interfacial contact area, which is at least one or two orders of magnitude higher than those in the conventional gas-liquid contactors. This greatly intensified the gas-liquid mass transfer process. Therefore, mass transfer and reaction process of gas-liquid phases in microchannels has wide development prospects. However, to date, it is still a huge challenge to realize industrialization of microreactor because of its small production capacity. In view of this, metal tube-in-tube microchannel reactor (MTMCR) with a high throughput (at lease one or two orders of magnitude higher than traditional microreactors), which was designed and developed by our group, was adopted as an absorption platform in this work. Alcohol amine chemical absorption method was utilized with methyldiethanolamine (MDEA) bind as absorbent to intensify the absorption of acidic gases of CO2and H2S commonly used in the industry. The absorption mechanisms coupled with reaction for single absorption of CO2and selective absorption of H2S. The main research contents and results are as follows:1、In the CO2absorption process, MDEA-CO2liquid mass transfer coefficient was firstly derived. And the effects of solvent concentration, additive concentration, the liquid flow rate, gas flow rate, temperature of solvent, the mean micropore size and the annular channel width of MTMCR on the CO2removal efficiency and the volume mass transfer coefficient were explored in detail. The results indicated that the volume mass transfer coefficient and CO2removal efficiency reached1.70s-1and97%, respectively, at a flow rate of100L/h and5.32L/h for the gas and liquid respectively, with alkanolamine solutions containing10wt.%MDEA and4wt.%PZ. CO2removal efficiency increases with the increase of liquid flow rate and the decrease of gas flow rate. There is a small temperature effect on the removal efficiency when the liquid-gas ratio is higher. However, removal efficiency obviously increases with the increase of temperature at a lower liquid-gas ratio. The mass transfer coefficient has an obvious increase trend in the290-315K. The mass transfer coefficient increases first and then remains unchanged with the increase of liquid flow rate, while rises with the increase of gas flow rate. CO2removal efficiency and mass transfer coefficient increase with the decrease of the size of the micropore and annular channel of MTMCR. However, the annular channel width has a greater effect both on CO2removal efficiency and mass transfer coefficient than the micropore size.2^In the MDEA-H2S selective absorption process, the effects of absorbent concentration, the liquid flow rate, gas flow rate, absorbent temperature, the mean micropore size and the annular channel width of MTMCR on the removal efficiency and H2S selectivity were investigated. The results indicated that H2S removal efficiency can reach more than99%when the concentration of MDEA was15%. H2S removal efficiency increases with the increase of liquid flow rate. But owing to the gas film control, the H2S removal efficiency has no obvious change at a liquid flow rate of higher than6L/h, while H2S selectivity decreases. With the increase of gas flow rate and gas-liquid ratio, H2S removal efficiency decreases, while H2S selectivity rapidly increases. In addition, as temperatures rises, H2S removal efficiency and selectivity of decreased with the increase of temperature. Therefore, the low temperature is beneficial to the absorption of H2S. H2S removal efficiency increases with the decrease of the micropore size and annular channel width of MTMCR. But the micropore size has a more obvious effect.