A Noval Denitration Technology By A Rotating Packed BED

In view of the continuously stringent emission standard of nitrogen oxide (NOx) in China, developing new technologies for NOX removal or updating the existed NOx removal system is very urgent. This work introduces a novel technology by using a rotating packed bed (RPB), which have the advantages of good mass transfer effect, small volume, and low cost, as the reactor for NOx removal. As a wet process denitration technology, a one-stage RPB was used for the absorption experiments by selecting urea+oxidant as absorbent. The effects of oxidants and operation conditions on the removal efficiency and the feasibility of cobalt sulfonated phthalocyanine (CoSPc) used as the liquid phase oxidation catalyst were studied. According to the consideration of gas oxidation degree and absorbent, a stirred tank combined with a RPB was to be a series system used for denitration and the effects of operation conditions were investigated. Experimental results are as follows:(1) In the one-stage RPB denitration system, by conducting experiments to evaluate various oxidants and comparing different concentrations of urea, 10% urea+0.10 mol·L-1 oxidant (NaClO2 and KMnO4) is selected as the liquid absorbent and the NOX removal efficiency of the simulated flue gas can reach about 55%. The effects of RPB rotational speed, gas-liquid ratio, inlet NOx concentration, and absorbent pH on NOx removal efficiency were studied. And pH is the key factor to influence the NOx removal efficiency. The optimum condition of urea+KMnO4 absorption system is as follows:RPB rotational speed 1600 r·min-1,gas-liquid ratio 50, pH 7, and room temperature. The optimum condition of urea+NaC102 absorption system is as follows:RPB rotational speed 1600 r·min-1, gas-liquid ratio 50, pH 7-9, and room temperature.(2) The feasibility studies of a new kind of aqueous solution containing CoSPc catalyst, used as absorbent for wet-process denitration, is studied. Experimental results showed that the simulated flue gas oxidation degree has a significant impact on total NOx removal efficiency when using the aqueous solution containing CoSPc catalyst as the absorbent. Compared with 10% urea +0.10 mol·L-1 NaClO2, the aqueous CoSPc absorbent displayed similar oxidation ability. Meanwhile, the catalytic activity of CoSPc can keep much high for a long time. It has the potential used in the RPB wet-process denitration.(3) For stirred tank and RPB combined wet-denitration process, total NOx removal efficiency can reach more than 80%. The stirred tank plays a major role to adjust the flue gas oxidation degree, and 0.04 mol·L-1 NaClO2 is selected as the optimum oxidant concentration, which can make the gas oxidation degree be up to more than 90%. The volume of liquid in the stirred tank is 5 L, which can maintain the gas oxidation degree at a high level for a long time. The aqueous solution containing CoSPc catalyst is used as absorbent in the RPB reactor. And various influencing factors are researched, mainly including CoSPc concentration, RPB rotational speed, gas-liquid ratio, and pH value. The pH value is a key factor for affecting the total NOX removal efficiency and it is best to be controlled under the condition of pH^12. The optimum condition of the aqueous solution containing CoSPc is as follows: CoSPc concentration is 10 mmol·L-1, RPB rotational speed is 1600 r·min-1, gas-liquid ratio is 50, and room temperature.