Simultaneous removal of NO and SO 2 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 SO 2 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 SO 2 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.