共查询到18条相似文献,搜索用时 203 毫秒
1.
为了研究H 2O对燃料N向NO转化各个阶段的影响,采用可沿程取样的沉降炉反应器,研究了一种烟煤在1273 K温度下,O 2/N 2、O 2/CO 2以及O 2/CO 2/H 2O气氛下燃烧的燃尽与NO生成的情况.并通过在停留时间为0.2、0.3、0.5、1.1 s与O 2浓度为5%、21%及30%情况下的实验来研究H 2O对NO生成的影响.实验结果表明,相对于O 2/CO 2气氛,H 2O的添加抑制了NO的生成,且该影响主要集中在燃烧初期挥发分N的氧化过程.随着O 2浓度的增加,H 2O添加对oxy-coal燃烧方式下NO生成影响加大. 相似文献
2.
在模拟燃煤热烟气为热源和介质条件下,以准东褐煤为原料,通过一维沉降炉进行炭化活化(一步法)制备粉状活性焦,考察了活性焦对Hg 0的吸附能力,探索了SO 2、H 2O、O 2、CO 2、H 2O+O 2、SO 2+O 2及H 2O+SO 2+O 2气氛对活性焦吸附Hg 0的影响机理。结果表明:一步法获得的活性焦对Hg 0具有较高的吸附性能。N 2气氛作对比,H 2O、H 2O+O 2、CO 2和SO 2气氛下抑制活性焦对Hg 0的吸附;O 2、SO 2+O 2和H 2O+SO 2+O 2促进活性焦对Hg 0的吸附。通过Hg 4f的XPS分析证明了不同气氛组成对活性焦吸附Hg 0的抑制和促进机理。H 2O覆盖在活性焦活性位上和堵塞孔隙而抑制活性焦对Hg 0的吸附;SO 2与Hg 0在活性焦上发生竞争吸附而抑制对Hg 0的吸附;CO 2 吸附在活性焦微孔上而抑制对Hg 0的吸附;O 2气氛下主要形成了HgO, SO 2+O 2气氛下Hg 0被氧化成HgSO 3,进一步氧化成HgSO 4; H 2O+SO 2+O 2气氛下,Hg 0被氧化成HgO和HgSO 4。 相似文献
3.
燃煤锅炉烟气中SO 3能对锅炉设备、大气环境造成包括低温腐蚀、粘污和蓝烟等一系列的危害。因而,对烟气中SO 3主要影响因素及其影响规律的研究对于预测和控制烟气中SO 3浓度以满足不断增长的节能减排标准有重要意义。基于文献中的C/H/O/N/S化学动力学模型的优化、整合建立了化学动力学模型,对烟气中SO 3主要影响因素及其影响规律进行计算研究。还基于自主设计搭建了全混流反应器测量装置,对上述计算工况中的SO 3浓度进行测量。研究发现,烟气中SO 3浓度主要受SO 2、O 2和H 2O的浓度,以及温度和反应停留时间等影响。SO 3浓度受烟气中CO、NO的影响也较为显著,但是受CO 2的影响不大。另外,随着反应停留时间的增加,烟气中SO 3浓度先后经历了3个不同阶段:急剧增加,增长趋势逐渐减缓和逐渐减少。 相似文献
4.
采用自行研究设计的介质阻挡-电晕放电等离子体反应装置在模拟烟气中进行NO、SO 2的脱除研究。考察了O 2、CO 2、水蒸气等气体组分对脱除NO、SO 2的影响,并进一步探讨了添加剂CH 3COONH 4对脱除NO、SO 2的影响及作用机理。实验结果表明:O 2、CO 2和水蒸气浓度的增加对NO脱除有抑制作用,而引入CH 3COONH 4后,这些抑制作用会被减弱,使NO的脱除率得到大幅度提升,但这些抑制作用不会完全消除。在引入CH 3COONH 4后,气体组分和输入电流的变化对脱除SO 2的影响不明显,SO 2脱除率可达到94%左右。在N 2/O 2/CO 2/H 2O/NO/SO 2体系中加入0.27%的CH 3COONH 4后,NO初始浓度不变的条件下,SO 2含量较少时,对NO的脱除影响不明显,随着SO 2浓度的增加,NO的脱除率不断下降,增加CH 3COONH 4的添加量可消除SO 2的影响;另一方面,在SO 2初始浓度恒定的条件下,随着NO含量的增加,SO 2的脱除率保持在94%左右。在N 2/O 2/CO 2/H 2O/NO/SO 2体系中加入0.51%的CH 3COONH 4后,输入电流2.5A时,NO的脱除率达到72%。 相似文献
5.
在小型紫外光-鼓泡床反应器中,对UV/H 2O 2氧化联合Ca(OH) 2吸收同时脱除燃煤烟气中NO与SO 2的主要影响因素[H 2O 2浓度、紫外光辐射强度、Ca(OH) 2浓度、NO浓度、溶液温度、烟气流量以及SO 2浓度]进行了考察。采用烟气分析仪和离子色谱仪分别对尾气中的NO 2和液相阴离子作了检测分析。结果显示:在本文所有实验条件下,SO 2均能实现完全脱除。随着H 2O 2浓度、紫外光辐射强度和Ca(OH) 2浓度的增加,NO的脱除效率均呈现先大幅度增加后轻微变化的趋势。NO脱除效率随烟气流量和NO浓度的增加均有大幅度下降。随着溶液温度和SO 2浓度的增加,NO脱除效率仅有微小的下降。离子色谱分析表明,反应产物主要是SO 42-和NO 3-,同时有少量的NO 2-产生。尾气中未能检测到有害气体NO 2。 相似文献
6.
采用自行设计的介质阻挡耦合电晕放电等离子体反应装置进行了模拟烟气同时脱硫脱硝的研究,分别考察乙醇胺(HOCH 2CH 2NH 2,MEA)在不同模拟烟气体系中对NO、SO 2脱除的影响,深入探讨了MEA在放电过程中与NO的作用机理。结果表明:在N 2/O 2/SO 2/NO体系中,0.56% MEA的加入可以显著消除O 2对NO脱除的抑制作用;在N 2/CO 2/SO 2/NO体系中,MEA会吸收进入体系中的部分CO 2,以减弱CO 2对NO脱除的抑制;在N 2/O 2/CO 2/H 2O/NO/SO 2体系中,0.56% MEA的加入既可以有效减弱H 2O的影响,也可以使NO的脱除率达到71.28%,继续将MEA的体积分数增大至1.20%时,可将该体系下NO脱除率提高到81.25%;同时,MEA可以在短时间内高效吸收体系内的SO 2,且几乎不受其他气体成分的影响,SO 2脱除率保持在95%左右。 相似文献
7.
选择性催化还原(SCR)技术由于脱硝效率高、选择性好而被广泛应用于烟气氮氧化物排放控制;然而,目前广泛采用的钒钛系SCR脱硝催化剂会使烟气中SO 2氧化成SO 3,烟气中过高的SO 3对电厂安全运行会造成严重影响,也会对环境造成污染。以典型V 2O 5-WO 3/TiO 2催化剂为研究对象,系统研究了SCR脱硝过程中烟气流量、温度、O 2浓度、SO 2浓度等对催化剂表面SO 3生成特性的影响,并进一步对SO 3生成的反应动力学特性进行了分析。研究表明:催化剂表面SO 3生成反应中SO 2的反应级数为0.59,当O 2浓度大于3%时,O 2的反应级数为0,该反应的表观活化能为70.39 kJ/mol;实验条件下,烟气中SO 2浓度增加会使SO 3生成的反应速率提高;O 2浓度对催化剂表面SO 3生成影响并不显著;烟气温度对催化剂表面SO 3生成具有显著影响,高温会促进SO 3的生成。 相似文献
8.
目前燃煤烟气活性炭脱汞技术已经很成熟,但机理方面的相关研究甚少或不全面,为了探讨汞与活性炭在燃煤烟气中的反应路径,本文在固定床上对商业活性炭(FAC)和1% NH 4Br改性活性炭(NBAC)进行了汞吸附实验,分别考察了O 2、SO 2、CO 2、NO及其混合烟气组分对吸附剂汞吸附的影响,然后利用程序升温脱附(temperature programmed desorption,TPD)技术分析了烟气组分对汞吸附的影响机理。固定床测试结果表明溴化铵改性可显著增加活性炭汞吸附性能,O 2、CO 2及NO可促进NBAC对汞的吸附,其中NO最好,而SO 2抑制NBAC对汞的吸附。TPD结果表明,溴素改性促进NBAC表面负载的溴与Hg 0结合生成HgBr 2,O 2存在促进了Hg 0的氧化生成HgO,NO存在显著增加了Hg 2(NO 3) 2的生成。SO 2与Hg 0对活性炭表面的官能团存在竞争吸附的关系,生成C-S,与Hg 0反应生成HgS。CO 2对NBAC吸附Hg 0的反应机理影响不大。 相似文献
9.
在模拟水泥预分解炉装置上研究污泥燃烧过程中还原性气体的产生及其对NO的还原,并系统研究了O 2浓度(体积分数为0~5%)对还原性气体产生及NO还原的双重影响。TG-FTIR特征分析表明,污泥燃烧产生的还原性气体主要为HCN、NH 3、CO和CH 4。进一步实验研究发现O 2浓度对HCN和NH 3的产生有明显影响,HCN和NH 3在O 2体积分数为3%时产生速率最大。同时,O 2浓度对污泥燃烧还原NO有较大影响。在污泥燃烧温度为900℃,烟气中CO 2体积分数为25%、NO浓度为600mg/m 3、SO 2浓度为200mg/m 3、O 2体积分数为3%时,NO还原率可达到最大(55.8%)。通过还原性物质(NH 3、CO、CH 4和污泥焦)对NO的还原实验研究进一步发现,NH 3和CO是污泥燃烧过程中NO还原的关键物质,且NH 3对NO的还原随着O 2浓度的增加而增加,而CO对NO的还原受O 2浓度的限制。综合分析表明,O 2浓度对污泥燃烧NO还原的影响主要是由NH 3的产生速率差异、NH 3和CO对NO的还原起主导作用且受O 2浓度影响较大等多种因素综合导致。采用污泥作为还原剂进行NO还原是一种高效的方法,在水泥生产中可通过控制O 2浓度获得较高的NO还原率。 相似文献
10.
对某台使用尿素为还原剂的100 t·h -1循环流化床锅炉的SNCR性能进行了CFD数值模拟,分析了温度、氨氮摩尔比等影响因素对SNCR脱硝效率、氨泄漏以及N 2O浓度的影响规律。结果表明,SNCR最佳温度窗口的范围为850~1050℃,且随着氨氮比的增大,温度窗口范围变宽;随着温度的升高,氨逃逸量明显下降,当温度超过940℃后,氨逃逸量基本可以忽略不计,而N 2O的生成量则呈现出先增大后减少的趋势。随着氨氮摩尔比的增加,脱硝效率逐渐增大,980℃左右达到峰值;氨泄漏随氨氮摩尔比的增加而增大;N 2O浓度与脱硝效率呈正比关系,最大生成量约为30 μl·L -1。 相似文献
11.
A reliable method to continuously monitor NH 3 in a gas stream containing CO—NO—O 2 and H 2O has been developed. The method is based on a quantitative oxidation of NH 3 to NO on a Pt catalyst. The extent of this reaction is affected by temperature, excess oxygen present, and space-velocity. There is a significant effect of inlet O 2 concentration on extent of various reactions in the CO—NO—O 2—H 2O system on a Pt/γAl 2O 3 catalyst. At fixed space-velocity and catalyst temperature, and for fixed reactor inlet concentrations of CO and NO. there is negligible CO—NO reaction either in the absence of oxygen or in the presence of excess oxygen. However, short of the stoichiometric amount of O 2 required for CO oxidation, there is appreciable CO—NO (and possibly also CO—NO—H 2O) reaction whose extent increases with increasing oxygen concentration. This increase is especially dramatic in a narrow window of O 2: concentrations near the stoichiometric point. Interestingly enough, near the stoichiometric point, self-sustained isothermal oscillations in the outlet CO and NO concentrations are also observed (Subramaniam and Varma. submitted for publication) 相似文献
12.
为探究以海水作为脱硫剂在喷射鼓泡塔上的脱硫特性,通过改变废气流量、海水温度、浸液深度、SO 2进口浓度和O 2浓度等操作参数,在自主设计和搭建的喷射鼓泡塔实验平台上进行了船舶模拟废气的脱硫实验。实验结果表明:在喷射鼓泡塔上,海水对SO 2的吸收容量为3.682 mmol·L -1,约是去离子水的3.92倍;脱硫效率随废气流量、海水温度和SO 2进口浓度的升高而降低,随浸液深度和O 2浓度的升高而升高,与脱硫时间呈线性下降关系。液相总传质系数随废气流量和海水温度的增加而增加,其中废气流量的影响幅度较小,仅为3.16%。增加O 2浓度可显著提高海水对SO 2的吸收容量,O 2浓度从0%增至12%时,海水的吸收容量从3.682 mmol·L -1增至7.463 mmol·L -1。 相似文献
13.
Combined effect of H 2O and SO 2 on V 2O 5/AC the activity of catalyst for selective catalytic reduction (SCR) of NO with NH 3 at lower temperatures was studied. In the absence of SO 2, H 2O inhibits the catalytic activity, which may be attributed to competitive adsorption of H 2O and reactants (NO and/or NH 3). Although SO 2 promotes the SCR activity of the V 2O 5/AC catalyst in the absence of H 2O, it speeds the deactivation of the catalyst in the presence of H 2O. The dual effect of SO 2 is attributed to the SO 42− formed on the catalyst surface, which stays as ammonium-sulfate salts on the catalyst surface. In the absence of H 2O, a small amount of ammonium-sulfate salts deposits on the surface of the catalyst, which promote the SCR activity; in the presence of H 2O, however, the deposition rate of ammonium-sulfate salts is much greater, which results in blocking of the catalyst pores and deactivates the catalyst. Decreasing V 2O 5 loading decreases the deactivation rate of the catalyst. The catalyst can be used stably at a space velocity of 9000 h −1 and temperature of 250 °C. 相似文献
14.
The selective catalytic reduction of NO+NO 2 (NO x) at low temperature (180–230°C) with ammonia has been investigated with copper-nickel and vanadium oxides supported on titania and alumina monoliths. The influence of the operating temperature, as well as NH 3/NO x and NO/NO 2 inlet ratios has been studied. High NO x conversions were obtained at operating conditions similar to those used in industrial scale units with all the catalysts. Reaction temperature, ammonia and nitrogen dioxide inlet concentration increased the N 2O formation with the copper-nickel catalysts, while no increase was observed with the vanadium catalysts. The vanadium-titania catalyst exhibited the highest DeNO x activity, with no detectable ammonia slip and a low N 2O formation when NH 3/NO x inlet ratio was kept below 0.8. TPR results of this catalyst with NO/NH 3/O 2, NO 2/NH 3/O 2 and NO/NO 2/NH 3/O 2 feed mixtures indicated that the presence of NO 2 as the only nitrogen oxide increases the quantity of adsorbed species, which seem to be responsible for N 2O formation. When NO was also present, N 2O formation was not observed. 相似文献
15.
Hydrophilic ceramic membranes would be potential candidates for membrane gas absorption if they could be applied to appropriate separation processes. This study highlights a novel concept for the practical implementation of SO 2 absorption in hydrophilic ceramic membrane that exhibits outstanding thermal and mechanical stabilities. With this aim, we investigated experimentally the performance of SO 2 absorption into aqueous sodium hydroxide (NaOH) solution in a hydrophilic alumina (Al 2O 3) membrane contactor in terms of SO 2 removal efficiency and SO 2 mass transfer flux, and compared the performance with that in a hydrophobic one. A series of experiments were performed at various conditions over a NaOH concentration range of 0-1.0 mol·L -1, a liquid flow rate range of 30-180 ml·min -1, a gas flow rate range of 120-1000 ml·min -1, an inlet SO 2 concentration range of 400-2000 μl·L -1, and a temperature range of 10-35℃. It was found that the hydrophilic membrane was more competitive when using a NaOH concentration higher than 0.2 mol·L -1. Furthermore, it can be inferred that the hydrophilic α-Al 2O 3 membrane exhibited exceptional long-term stability under 480 h continuous operation. 相似文献
16.
The effect of the support oxide, Pt precursor and reactant gas composition on the catalysis of soot oxidation was investigated using carbon black as a model soot and simulated exhaust gases. The Pt precursors used were Pt(NH 3) 4(OH) 2, H 2PtCl 6·6H 2O, Pt(NH 3) 4(NO 3) 2, and Pt(NH 3) 4Cl 2. The support metal oxides used were SiO 2, Al 2O 3, and ZrO 2. Pt/SiO 2 prepared from Pt(NH 3) 4(OH) 2 showed the highest carbon oxidation activity. It had much higher activity in the condition of N 2+O 2+H 2O+NO+SO 2 than without NO and SO 2. 相似文献
17.
简述了NH 3和NO在催化剂表面吸附、转化活化和反应历程及H 2O和SO 2对以上反应行为的影响。分析表明,NH 3氧化脱氢进而与NO反应是决定NH 3反应性和最终产物的关键。NO以气态(Eley-Rideal机理)或硝基类物质等吸附态(Langmuir-Hinshelwood机理)形式参与选择催化还原(SCR)反应。提高催化剂酸性和氧化还原循环性能,利于NH 3和NO吸附和转化及相互间反应。高温时,H 2O影响轻微,而SO 2增强催化剂酸性,提高脱硝活性。低温时,H 2O和SO 2抑制NO吸附和转化活化,导致硫铵盐累积和活性位转变为硫酸盐使催化剂失活。因此,提高抗H 2O、抗SO 2性能是低温脱硝催化剂研发的重要方向。而发展在线升温等再生工艺以解决硝酸盐或含硫化合物导致的失活问题,对保障低温脱硝系统长期稳定运行具有重要意义。 相似文献
18.
Cu 2+ ion-exchanged pillared clays are substantially more active than Cu 2+-ZSM-5 for selective catalytic reduction (SCR) of NO by hydrocarbons. More importantly, H 2O (or SO 2) has only mild effects on their activities. First results on Cu 2+-exchanged TiO 2-pillared montmorillonite were reported by this laboratory (Yang and Li, Ref. [1]), that showed overall activities two to four times higher than Cu 2+-ZSM-5. A delaminated pillared clay was subjected to Cu2+ ion-exchange and studied for SCR by C2H4 in this work. The Cu2+ ion-exchanged delaminated Al2O3-pillared clay yielded substantially higher SCR rates than both Cu2+-exchanged TiO2-pillared clay and Cu2+-ZSM-5 at temperatures above 400°C. The peak NO conversion was 90% at 550°C and at a space velocity of 15,000 h−1 (with O2 = 2%). The peak temperature decreased as the concentration of O2 was increased. The macroporosity in the delaminated pillared clay was partially responsible for its higher peak temperatures (than that for laminated pillared clays). At 1000 ppm each for NO and C2H4, the NO conversion peaked at 2% O2 for all temperatures. H2O and SO2 caused only mild deactivation, likely due to competitive adsorption (of SO2 on Cu2+ sites and H2O on acid sites). The high activity of Cu2+-exchanged Al2O3-pillared clay was due to a unique combination of the redox property of the Cu2+ sites and the strong Lewis acidity of the pillared clay. The suggested mechanism involved NO chemisorption (in the presence of O2) on Cu2+OAl3+-on the pillars, and C2H4 activation on the Lewis acid sites to form an oxygenated species. 相似文献
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