Absorption Of Nitric Oxide In A Microporous Tube-in-Tube Microreactor

The emission of nitric oxide (NO) leads to a number of problems like ground level ozone formation, particulate matter problem and global warming, which has given harmful effects on the environment and human health. At present, many methods have been used for NO removal process. Among them, wet denitration has received extensive attention. Transition metal complex compounds are widely used as an absorbent to remove NO owing to their high reaction rate with NO and good regeneration ability. However, NO absorption rate is strongly affected by mass transfer limitation of NO and Fe(Ⅱ)EDTA solution in traditional reactors. In this master thesis, the microporous tube-in-tube microreactor (MTMCR) was adopted as an intensifiedgas-liquid mass transfer reactor for NO removal with ferrous chelate solution (Fe(Ⅱ)EDTA) and ammoniacal cobalt(II) (Co(NH3)6Cl2) solution as absorbents. The main contents were as followed:1. Fe(II)EDTA was used as absorbent to remove NO in the MTMCR. The effects of design and operating parameters such as micropore size, annular channel width, liquid flow rate, gas flow rate, gas-liquid flow rate ratio, pH and concentration of the absorbent and absorption temperature on NO removal efficiency were explored. Reducing the micropore size and the annular channel width would be beneficial to denitrification. The optimum pH of the absorbent was determined as 7. NO removal efficiency increased with the increase of the absorbent concentration and liquid flow rate, as well as the decrease of the absorption temperature, the micropore size and annular channel width. NO removal efficiency reached 95% under the optimum operating conditions (C=0.04 mol/L, G/L=32, T=293 K, dm=10μm, da=250 μm).2. Ammoniacal cobalt(Ⅱ) was further used as absorbent to remove NO in the MTMCR. The effects of design and operating parameters such as micropore size, annular channel width, liquid flow rate, gas flow rate, gas-liquid flow rate ratio, pH and concentration of the absorbent and absorption temperature on NO removal efficiency were also explored. The research indicated similar absorption rules with Fe(Ⅱ)EDTA system. However, NO removal efficiency only reached 85% under the optimum operating conditions (C=1.0 mol/L, G/L=32, T=293K, dm=10 μm, da=250 μm), lower than Fe(Ⅱ)EDTA system..3. Gas-liquid mass transfer characteristics in the MTMCR based on the overall volumetric mass transfer coefficient (KLa) were investigated with Fe(Ⅱ)EDTA solution as absorbent. The effects of design and operating parameters such as micropore size, annular channel width, liquid flow rate, gas flow rate, gas-liquid flow rate ratio, pH and concentration of the absorbent and absorption temperature on KLa were explored. The increase of liquid or gas flow rate could greatly intensify the gas-liquid mass transfer. Reducing the micropore size and the annular channel width would lead to a higher mass transfer rate. KLa increased with the increase of the absorbent concentration, as well as the decrease of the absorption temperature, the micropore size and annular channel width. In addition, KLa increased with increasing gas-liquid flow rate ratio and gas flow rate.