Simultaneous removing SO2 and NO by a new system containing cobalt complex.

Absorption and catalytic oxidation of nitric oxide can be achieved by using cobalt(III) ethylenediamine (Co(en)2(3+)). When simultaneous absorbing SO2 and NO, the precipitation of Co2(SO3)3 will be yielded and the NO removal will be decreased. A new catalyst system using Co(en)3(3+) coupled with urea has been developed to simultaneous remove NO and SO2 in the flue gas. NO is absorbed and catalytically oxidized to nitrite and nitrate by Co(en)3(3+). The dissolved oxygen in scrubbing solution from the feed stream acts as oxidant. Urea restrains the precipitation of Co2(SO3)3 by oxidizing SO3(2-) to SO4(-) as CoSO4 is more soluble in water. The experimental results proved that nearly all SO3(2-) can be oxidized to SO4(-2) and the high NO and SO2 removal could be obtained with the new system. The NO removal is influenced by gas flow rate, the concentration of Co(en)3(3+) and urea in the absorption solution, the temperature of the scrubbing solution and the content of oxygen in the flue gas. The low gas flow rate is favorable to increase the NO removal. The experiments proved that the NO removal could be maintained at more than 95% by the system of 0.02 mol/L Co(en)3(3+) and 1% urea at 50 degrees C with 10% O2 in the flue gas.