Nelli C H, Rochelle G T
Department of Chemical Engineering, University of Texas at Austin 78712-1062, USA.
J Air Waste Manag Assoc. 1998 Sep;48(9):819-28. doi: 10.1080/10473289.1998.10463728.
At conditions typical of a bag filter exposed to a coal-fired flue gas that has been adiabatically cooled with water, calcium hydroxide and calcium silicate solids were exposed to a dilute, humidified gas stream of nitrogen dioxide (NO2) and sulfur dioxide (SO2) in a packed-bed reactor. A prior study found that NO2 reacted readily with surface water of alkaline and non-alkaline solids to produce nitrate, nitrite, and nitric oxide (NO). With SO2 present in the gas stream, NO2 also reacted with S(IV), a product of SO2 removal, on the exterior of an alkaline solid. The oxidation of S(IV) to S(VI) by oxygen reduced the availability of S(IV) and lowered removal of NO2. Subsequent acidification of the sorbent by the removal of NO2 and SO2 facilitated the production of NO. However, the conversion of nitrous acid to sulfur-nitrogen compounds reduced NO production and enhanced SO2 removal. A reactor model based on empirical and semi-empirical rate expressions predicted rates of SO2 removal, NO2 removal, and NO production by calcium silicate solids. Rate expressions from the reactor model were inserted into a second program, which predicted the removal of SO2 and NOx by a continuous process, such as the collection of alkaline solids in a baghouse. The continuous process model, depending upon inlet conditions, predicted 30-40% removal for NOx and 50-90% removal for SO2. These results are relevant to dry scrubbing technology for combined SO2 and NOx removal that first oxidizes NO to NO2 by the addition of methanol into the flue duct.
在袋式过滤器处于典型工况的情况下，该过滤器接触到用水进行绝热冷却的燃煤烟道气，将氢氧化钙和硅酸钙固体置于填充床反应器中，使其暴露于含有二氧化氮（NO₂）和二氧化硫（SO₂）的稀释加湿氮气流中。先前的一项研究发现，NO₂很容易与碱性和非碱性固体的表面水反应，生成硝酸盐、亚硝酸盐和一氧化氮（NO）。当气流中存在SO₂时，NO₂还会与碱性固体外部的SO₂去除产物S(IV)发生反应。氧气将S(IV)氧化为S(VI)，降低了S(IV)的可用性，也降低了NO₂的去除率。随后，由于NO₂和SO₂的去除导致吸附剂酸化，促进了NO的生成。然而，亚硝酸转化为硫氮化合物降低了NO的生成，并提高了SO₂的去除率。基于经验和半经验速率表达式的反应器模型预测了硅酸钙固体对SO₂的去除率、NO₂的去除率和NO的生成率。将反应器模型的速率表达式插入到第二个程序中，该程序预测了通过连续过程（如在布袋除尘器中收集碱性固体）对SO₂和氮氧化物的去除情况。根据入口条件，连续过程模型预测氮氧化物的去除率为30%-40%，SO₂的去除率为50%-90%。这些结果与用于联合去除SO₂和氮氧化物的干式洗涤技术相关，该技术首先通过向烟道中添加甲醇将NO氧化为NO₂。
