SO2和NO同时吸收过程的研究

2019-01-25 02:22:56

The PPM NO oxide nitric









中文题名SO2和NO同时吸收过程的研究

 





副题名 





外文题名 Simultaneous removal of sulfur dioxide and nitric oxide 





论文作者龙湘犁   





导师袁渭康  肖文德教授   





学科专业化学工程   





研究领域\研究方向化学反应工程   





学位级别博士 





学位授予单位华东理工大学   





学位授予日期2002   





论文页码总数122页   





关键词大气污染  废气处理  酸雨  一氧化氮  脱硫脱硝   





馆藏号BSLW

/2003

/X701

/12 





【中文摘要】

    本文根据NO液相催化氧化的观点,利用有关钴络离子与NO和氧作用的性质,以对已有湿法脱硫工艺的改进,实现同时脱硫脱硝的目的,独创性地提出并研究了两种同时脱除SO〓和NO的方法,研究结果表明:
   1.在氨水加入可溶性钴盐和碘、溴等卤素的阴离子可构成NO的液相复合催化体系,钴和氨络合成的Co(NH〓)〓离子为主催化剂,I〓为助催化剂,烟道气中的O〓作氧化剂,利用紫外光的催化作用实现Co〓和I〓离子两个循环的藕合,保持溶液中活性组份Co(NH〓)〓离子的稳定,实现NO的液相催化氧化和回收,并且能同时实现SO〓的吸收和氧化,NO的脱除率在浓度为250~1000ppm的范围内,可达80%以上;SO〓的脱除率在浓度为800~2500ppm的范围内,可达100%。和过氧化氢和Fe-EDTA法相比,本方法脱NO的效果具有持续时间长、效率高等优点。用该法对现有的氨法脱硫工艺进行改进,可实现同时脱硫脱硝,而且可省去氨法脱硫工艺中的亚硫酸根氧化工段,简化流程,节省投资,降低成本,副产氨肥,变废为宝。
   根据本实验的研究结果,对Co(NH〓)〓/I〓体系,当摩尔比Co〓/I〓=4∶1,50℃、氧含量为5.2%时能取得最高的NO脱除率:并且SO〓含量越高,NO的脱除率也越高。Co(NH〓)〓离子与NO的气液反应,在NO浓度为ppm级时,可看作飞速不可逆反应,当Co(NH〓)〓浓度大于0.02M时,过程为气膜控制,继续增大Co(NH〓)〓浓度和液相流率对NO吸收速度的提高不大。
   2.在碱性溶液中加入乙二胺合钴也可以实现NO的氧化和吸收同时进行,乙二胺合钴离子是氧化催化剂,氧化剂是废气中的氧气,该方法的实施能使NO的脱除工艺简化;在该溶液中再加入生石灰可以同时脱除SO〓。和Fe-EDTA和双氧水法相比,本法具有效率高、持续时间长的优点。NO脱除率在含量为250~1000ppm的范围内,条件控制适当能长时间保持90%以上;SO〓脱除率在浓度为800~2500ppm的范围内,可达100%。
   根据本实验的研究结果,氧的分压越大,越有利于NO氧化和脱除;乙二胺合钴溶液的pH值应维持在9以上,高的pH值有利于NO的脱除;在50℃时可取得最佳的NO吸收效果。在所研究的乙二胺合钴和NO浓度(ppm级)范围内,NO与乙二胺合钴的反应可看作飞速不可逆反应,当乙二胺合钴的浓度大于0.02M时,过程为气膜控制。当氧化钙的加入量增加到一定程度后,气体中SO〓浓度的提高不会对NO的脱除率产生明显的影响。











【外文摘要】

 Abstract
   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.