Removal of SO_2 from Flue Gas by Sodium Humate Solution

摘要

A novel process of flue gas desulfurization (FGD) by sodium humate (HA-Na) solution was developed. Experiments were carried out to examine the effect of various operating parameters, such as the HA~Na concentration, pH, temperature, gas flow rate. O_2 concentration, SO_2 inlet concentration, and NO_2, on the SO_2 absorption efficiency and desulfurization time in a lab-scale bubbling reactor. The experimental results indicate that the HA-Na concentration significantly influences the desulfurization time but has little effect on the SO_2 absorption efficiency. The desulfurization time increases with the HA-Na concentration reaching 0.06 g/mL, and after this value, it begins to decrease. The SO_2 absorption efficiency maintains 99% when pH is above 4.5. A low gas flow rate and low temperature are favorable to SO_2 absorption. The increase of the SO_2 inlet concentration improves the mass transfer of SO_2 and accelerates the SO_2 consumption rate. NO_2 coexisting with SO_2 can promote SO_2 absorption because it may speed up oxidation of sulfile to sulfate. HA-Na solution shows great performance in SO_2 absorption, and the SO_2 absorption efficiency can be maintained above 98% for 1.5 h with 100mL of HA-Na solution (0.06 g/mL), at the condition of 25 ℃, gas flow rate of 0.14 m~3/h, and inlet SO_2 concentration of 2000 ppm. Moreover, the desulfurization products can be made into the humic acid (HA) compound fertilizer, and recycling water can be obtained in this desulfurization process.