SIMULTANEOUS REMOVAL OF NO AND SO2 IN PACKED SCRUBBERS OR SPRAY TOWERS

Nitric oxide and sulfur dioxide can be removed from flue gas by scrubbing with a lime slurry containing ferrous EDTA. Tests in a 0.90m diameter column with several commercial packings gave 99 to 99.9 percent SO2 removal and 10 to 60 percent NO removal. The absorption of NO is controlled by the liquid-film resistance, and the number of transfer units varies with the square root of the ferrous EDTA concentration, the 0.4 to 0.6 power of the liquid rate, and the - 1.0 power of the gas velocity, in agreement with predictions. The height of a transfer unit for NO absorption, corrected for end effects, was 10 to 15m, about 30 times the estimated values for SO2 absorption, which is gas-film controlled. The spray tower gave lower removal rates for both gases, but the ratio of transfer units was about the same as for the packed columns.