外文题名 Simultaneous removal of sulfur dioxide and nitric oxide
关键词大气污染 废气处理 酸雨 一氧化氮 脱硫脱硝
According to the idea of nitric oxide oxidation in aqueous solutions, two novel methods were invented to retrofit the wet desulfurization technique to realize the simultaneous removal of sulfur dioxide and nitric oxide. The researches on these two methods were made as follow:
A liquid catalyst for nitric oxide oxidation may be made up by dissolving cobalt (Ⅱ) and Iodide salts into aqueous ammonia solution. The hexamminecobalt (Ⅱ) ions produced by cobalt (Ⅱ) ions complexing with ammonia act as catalysts and iodide ions act as cocatalysts. The oxidant is the oxygen in flue gas. The couple of cobalt (Ⅱ) recycle and I〓 recycle realized by photocatalysis keeps the active constituent-hexamminecobalt (Ⅱ) ions constant. The oxidation and absorption of nitric oxide can be carried out simultaneously, so is the absorption and oxidation of sulfur dioxide. Nitric oxide removal may be over eighty percent at the concentration between 250ppm and 800ppm and sulfur dioxide removal is 100 percent at the concentration between 800ppm and 2500ppm. Such method is superior to hydrogen peroxide and Fe (Ⅱ) -EDTA. Therefore, the ammonia desulfurization technique can be modified by such method to implement the simultaneous removal of SO〓 and NO. The sulfite oxidation workshop section can be left out and the process can be simplified. Hence the capital expenditure can be reduced and cost of operation can be cut down. The valuable fertilizer ammonia sulfate is also produced.
According to the results of the experiments carried out, the optimal cobalt (Ⅱ) to iodide ratio was 4: 1. The topgallant temperature for nitric oxide removal was 50℃. The highest nitric oxide removal may be attained when the oxygen concentration was 5. 2％. The more the sulfur dioxide there is. the higher the nitric oxide removal. The nitric oxide absorption reaction can be regarded as instantaneous when nitric oxide levels are ppm ranges. The gas-liquid reaction become gas film controlling as the Co (NH〓) 〓 concentration exceeds 0.02M. The rate of the nitric oxide chemical absorption is independent of Co (NH〓) 〓 concentration and the flow of the liquid phase.
Cobalt ethylenediamine basic solution is also able to carry out the oxidation and absorption of nitric oxide simultaneously. The cobalt ethylenediamine ion acts as a catalyst and the oxygen in exhaust gas acts as an oxidant. Simultaneous removal of NO and SO〓 can be achieved by dissolving calcium oxide into cobalt ethylenediamine basic solution. Compared with hydrogen peroxide and Fe (Ⅱ) EDTA, this method can keep higher NO for a longer time. Over 90％ nitric oxide removal can be obtained at the concentration between 400ppm and 1000ppm if the absorption condition is favorable. Sulfur dioxide removal is kept at 100 percent at the concentration between 800ppm and 2500ppm.
In terms of the experiments, the increase of oxygen partial pressure can speed up the oxidation and absorption of nitric oxide. The pH value ought to be kept greater than 9. The higher the pH values in the solution, the higher the NO removal. The gas-liquid reaction between NO and cobalt ethylenediamine can be regarded as instantaneous at the ranges of nitric oxide and cobalt ethylenediamine concentrations studied in the research. The gas-liquid reaction becomes gas film controlling as the cobalt ethylenediamine concentration surpasses 0.02M. The removal of nitric oxide has nothing to do with the sulfur dioxide concentration in gas phase if the calcium oxide in the cobalt ethylenediamine solution is sufficient.