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Transformation Mechanisms of NO_x into N_2O and Its Depression in Coal Combustion and De-NO_x Process

燃煤脱NO_x过程中NO_x向N_2O的转化机理及其抑制

基本信息

批准号：
03452128
负责人：
OHTAKE Kazutomo
金额：
$ 4.54万
依托单位：
Toyohashi University of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-03452128/
关键词：
Pulverized Coal Combustion Bubbling Fluidized Bed Coal Combustion Reaction Mechanisms of Nitric Oxide and Nitrous Oxide Non-Catalytic Selective Reduction of Nitric Oxide by Ammonia Injection 気泡式石炭流動層燃焼一酸化窒素・亜酸化窒素反応機構

项目摘要

Nitrous oxide (N_2O) has been arrested the attention as one of environmental pollutants produced from coal combustion. In this study, characteristics of N_2O formation/destruction in both turbulent pulverized coal combustion (high temperature combustion) and bubbling fluidized bed coal combustion (low temperature combustion) are discussed experimentally and theoretically.In case of turbulent pulverized coal combustion, during the volatile matter combustion region, N_2O concentration increases. The maximum N_2O concentration becomes higher, if the temperature gradient gets gentler. Finally, at the exit of furnace, N_2O reaches quite low value. The influence of non-catalytic selective reduction (NCSR) of NO by NH_3 injection on N_2O formation/destruction depends on the combustion atmosphere where NH_3 is supplied.In the bubbling fluidized bed coal combustion, N_2O concentration increases with decreasing temperature and with increasing the combustion stoichiometry. The difference of N_2O … More concentration due to coal types can be explained by the difference of N-contained species evolved together with the volatile matter. HCN is found to contribute more to N_2O formation than NH_3. In case that the coal particles are directly supplied onto the bed surface, N_2O is mainly formed in the freeboard of combustor. In case of bottom feed experiments, on the other hand, N_2O is rapidly formed just above the air distributor. In the experiments of N_2O decomposition through the beds of several kinds of particles, char, CaO and oxidized stainless steel particles can catalytically contribute to the N_2O decomposition. In the char combustion experiments, the tendency of N_2O formation characteristics is similar to that of the combustion of volatile matter.From the numerical model for single coal particle combustion, N_2O is mainly produced during the volatile combustion. The reactions by way of NCO, NH and N_2 contribute to N_2O formation. On the other hand, H radical becomes one of the important species for N_2O reduction. The modeling could explain well the experimental results. Less

一氧化二氮（N_2O）作为煤炭燃烧产生的环境污染物之一而受到人们的关注。本研究从实验和理论上讨论了湍流煤粉燃烧(高温燃烧)和鼓泡流化床煤燃烧(低温燃烧)中N_2O的形成/破坏特征。在湍流煤粉燃烧的情况下,在挥发分燃烧区域,N_2O浓度增加。如果温度梯度变得更平缓，则最大N_2O浓度变得更高。最后，在炉子出口处，N_2O达到相当低的值。 NH_3喷射非催化选择性还原(NCSR)对N_2O生成/破坏的影响取决于供给NH_3的燃烧气氛。在鼓泡流化床煤燃烧中,N_2O浓度随着温度的降低和燃烧化学计量的增加而增加。煤种引起的N_2O浓度差异可以通过与挥发物一起演化的含氮物种的差异来解释。发现 HCN 对 N_2O 形成的贡献大于 NH_3。当煤颗粒直接供给床面时，N_2O主要在燃烧室的干区形成。另一方面，在底部进料实验中，N_2O 在空气分配器上方快速形成。在几种颗粒床分解N_2O的实验中，焦炭、CaO和氧化不锈钢颗粒对N_2O的分解有催化作用。在焦炭燃烧实验中,N_2O的生成特征与挥发分燃烧的趋势相似。从单煤颗粒燃烧的数值模型来看,N_2O主要是在挥发分燃烧过程中产生的。 NCO、NH和N_2的反应有助于形成N_2O。另一方面，H自由基成为N_2O还原的重要物种之一。该模型可以很好地解释实验结果。较少的