Zhou Chun-Qiong, Deng Xian-He, Pan Zhao-Qun
School of Chemical and Energy Engineering, South China University of Technology, Guangzhou 510640, China.
J Environ Sci (China). 2006;18(3):567-71.
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.
使用乙二胺钴(III)（Co(en)2(3+)）可实现一氧化氮的吸收和催化氧化。同时吸收二氧化硫和一氧化氮时，会生成Co2(SO3)3沉淀，导致一氧化氮去除率降低。已开发出一种使用Co(en)3(3+)与尿素耦合的新型催化剂体系，用于同时去除烟气中的一氧化氮和二氧化硫。Co(en)3(3+)将一氧化氮吸收并催化氧化为亚硝酸盐和硝酸盐。进料流洗涤液中的溶解氧充当氧化剂。尿素通过将SO3(2-)氧化为SO4(-)来抑制Co2(SO3)3沉淀，因为硫酸钴在水中的溶解度更高。实验结果表明，几乎所有的SO3(2-)都可被氧化为SO4(-2)，该新型体系能实现较高的一氧化氮和二氧化硫去除率。一氧化氮的去除受气体流速、吸收液中Co(en)3(3+)和尿素的浓度、洗涤液温度以及烟气中氧气含量的影响。低气体流速有利于提高一氧化氮去除率。实验证明，在50℃、烟气中氧气含量为10%的条件下，0.02 mol/L Co(en)3(3+)和1%尿素的体系可使一氧化氮去除率保持在95%以上。
