共查询到18条相似文献,搜索用时 78 毫秒
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为了更深入地了解废旧橡胶热解机理,运用分子动力学的方法,对应用广泛的丁苯橡胶的热解过程进行了模拟,并结合模拟结果和密度泛函数对其气相产物的反应路径进行推测计算。模拟结果表明:热解过程主要分为两个阶段,第一个阶段,主要发生丁苯橡胶链断裂形成短链和单体,第二阶段主要发生单体进一步生成气体。在第一个阶段,主要产物为1,3-丁二烯,还有部分苯乙烯,反应为放热反应,其中苯乙烯的形成不利于1,3-丁二烯后续生成H_2、■的热解反应;在第二阶段,1,3-丁二烯热解的主要气相产物为■,中间C—H键上的H原子更容易被夺去;苯乙烯热解的主要气相产物为H_2,乙烯基与苯基结合处的H原子最容易被夺去。此外,还会产生■等气体。这将为废旧橡胶热解得到特定的气相产物提供理论依据。 相似文献
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利用固定床实验系统,在800~1 500℃的反应温度范围内进行了NH_3还原NO实验,分析不同气氛条件下反应温度、氨氮摩尔比以及组分浓度对脱硝效率的影响。实验结果表明:氧化性气氛下最佳脱硝温度约为950℃,温度继续升高时脱硝效率开始下降,而还原性气氛下NH_3对NO的还原存在一个临界温度(约1 000℃),低于临界温度时,NH_3对NO没有脱除效果,反而会额外生成NO,超过临界温度后,脱硝效率随着温度的升高迅速跃升至最大,氨氮摩尔比为2.0时最大脱硝效率可达95%,且在1 200℃以上的高温条件下保持稳定;修正后的GADM98模型对NO浓度的预测与实验结果符合较好,活性基团对NH_2的消耗是高温氧化性气氛下脱硝效率下降的重要原因。 相似文献
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NH3选择性催化还原烟气中NO的反应动力学 总被引:3,自引:0,他引:3
采用自行研制的V2O5-WO3-MoO3/TiO2催化剂在微型积分反应器上对NH3还原NO的反应进行了微观动力学试验,考察了温度、空速值对NO转化率的影响,并得出反应的微观动力学方程,确定了相关的动力学参数.通过小型试验台的试验,考察了反应气体在催化剂内部的传质、扩散过程对反应速率的影响,建立了催化剂有效因子的计算模型和宏观反应速率方程.试验结果表明,用该模型计算得到的理论值和试验数据具有良好的一致性. 相似文献
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在固定床反应器中,利用瞬态响应技术和程序升温技术研究了低温时NH3选择性催化还原(SCR)NO的瞬态动力学及V2O5-WO3/TiO2催化剂活性的影响因素,试验结果表明:O2的体积分数增大,NO转化率增大;H2O的存在抑制了NO的转化率;SO2的存在提高了NO的转化率.低温时,SCR反应遵循Eley-Rideal机理,... 相似文献
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运用热分析仪器研究固体热分解特性和反应动力学是目前较为流行的方法。本文在自制的加压热重分析仪上,研究了在惰性气体(N2)环境下,压力(101kPa~1317kPa)对煤的热解过程的影响规律,测得了不同压力下煤粒挥发份的析出过程,以及煤粒粒径对煤热解时挥发份析出过程的影响。同时,在前人的基础上得出了煤加压热解动力学方程,并以此建立了加压煤热解模型。利用该模型进行了分析计算,其计算结果与实验结果符合得很好。 相似文献
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采用固定床反应器对水煤浆及其制浆原煤在惰性气氛下,制浆原煤在水蒸气气氛进行热解试验,研究HCN、NH3的释放特性。结果发现,制浆原煤和水煤浆HCN的释放量,随温度增加变化缓慢,趋于稳定;而制浆原煤在水蒸气气氛下,HCN的量随温度变化增加迅速,析出量远远超出制浆原煤及水煤浆的释放量。制浆原煤NH3释放量随温度升高先增加后有下降,在l000℃左右出现一个峰值,温度继续升高,NH3的量不再增加反而开始降低;水煤浆中NH3析出的量随温度增加,虽变化缓慢.但是仍比制浆原煤释放出的N心量要多;制浆原煤在水蒸气气氛下,随温度的升高,NH3的量一直呈增加趋势,温度到达1000℃后,增加更加迅速,释放量大于制浆煤和水煤浆的NH3释放量。综合考虑HCN和NH3的释放量以及燃料的着火、燃烧.显然水煤浆燃烧要优于煤粉的单独燃烧和煤粉喷水蒸气燃烧。 相似文献
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选择性催化还原(SCR)技术被广泛应用于大型燃煤机组烟气氮氧化物脱除中,脱硝效率达到90%以上。烟气温度下降会导致SCR系统的催化剂受损,在停机之前会停止向SCR系统喷氨,导致此期间的NO_x排放超标。采集并计算了某电厂停炉过程中排放NO的数据,实验发现NO排放量在此过程中仍会有不同幅度的降低。运用密度泛函理论(DFT)基于V_2O_5团簇模型研究了NO和NH_3在催化剂不同吸附位上的吸附机理。研究结果表明:NO不会稳定吸附在催化剂的表面;NH_3既能吸附在钒基表面的Lewis酸性位,又可吸附在Br?nsted酸性位,而且更稳定。由此可知,停机后由于吸附在催化剂表面的NH_3与烟气中的NO反应,使得出口处的NO量降低。 相似文献
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生物质在实验室环境与实际生产环境下的热解特性存在较大差别。以30mm长玉米秸秆为对象,在管式炉中模拟移动床热解炉中实际传热环境,研究热解温度、热解时间对热解进程的影响规律,同时研究了生物质在实验室环境下的热解特性。研究结果表明,实验室环境下生物质热解温度超过580℃后,提高热解温度对生物质挥发分残留率的影响可以忽略,但在实际生产环境下,由于传热传质条件的变化,在合理的经济时间内,生物质热解温度超过580℃后生物质的挥发分仍有较高的析出速率,移动床热解炉的工艺参数确定应该以实际生产环境下的热解特性为理论基础。 相似文献
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《International Journal of Hydrogen Energy》2022,47(40):17778-17787
As a marine engine fuel of great concern, ammonia needs to be mixed with another high reactive fuel to improve its combustion performance. In this work, the combustion performance of NH3/NH4NO2 and NH3/H2 was compared under different boundary conditions (excess air coefficient, initial temperature, pressure and mixing ratio). The numerical simulation of compression combustion is carried out under different power loads. The addition of ammonium nitrite decreases the ignition requirement of ammonia and shortens the ignition delay time of the mixture fuel. The boundary conditions of compression ignition can be reduced by mixing hydrogen and mixing ammonium nitrite, but it is not enough to achieve compression ignition under NH3/H2 mode. The addition of 30% ammonium nitrite can reduce the intake temperature to 300–360 K, which makes the compression ignition of the mixed fuel feasible. Meanwhile, in order to reduce the high in-cylinder combustion pressure and improve the combustion performance of the mixed fuel, the fuel injection strategy was proposed to achieve constant combustion pressure of 30 MPa under the premise of less power loss, which is a potential solution for the combustion of ammonia fuel. 相似文献
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《能源学会志》2020,93(4):1511-1518
WO3/CeO2 catalysts with different support morphologies were fabricated by incipient wetness technique and applied to selective catalytic reduction of NO by NH3 (NH3-SCR). WO3/CeO2 rod (WCR) displayed higher catalytic activity and resistance to SO2 and H2O compared with WO3/CeO2 polyhedron (WCP) and WO3/CeO2 cube (WCC). N2-BET, XRD, Raman, H2-TPR, TEM, HRTEM, NH3-TPD, XPS and in situ DRIFTS were conducted to investigate the physicochemical properties of the catalysts and the adsorption of NH3 and NOx species on the catalytic surface. These characterization results demonstrated that the larger BET surface area, the smaller CeO2 particle size, the higher surface acidity, the more oxygen defects, the better redox performance, and the higher Ce3+ and Oα ratios of the catalysts played critical functions in obtaining more outstanding NH3-SCR catalytic performance. All of these characterization results were also closely related to the CeO2 morphology. The results of the in situ DRIFTS showed that the WCR had the highest intensities of the adsorbed NOx and NH3 species among these three catalysts. The reactions between adsorbed species attributed to NOx and NH3 on the catalyst surface can also be a key factor in the NH3-SCR catalytic performance enhancement. 相似文献
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采用程序升温还原(TPR)和X-光电子能谱(XPS)技术研究了稀土钙钛矿型催化剂LaBO3上氧种的化学势、B位元素的平均价态及催化剂氧种的分布及种类,同时分析了N2O的分解反应机理。实验结果表明,B位离子平均价态升高,氧离子的化学势增大,反应能力增强,催化活性较好;在LaBO3化合物上有两类氧种,即低能位的吸附氧和高能位的晶格氧,催化剂表面吸附氧对N2O分解有阻抑作用,CH4的加入能与表面吸附氧反应,提供氧空位,促进反应进行;N2O在钙钛矿型化合物LaBO3上的分解反应属于表面上的催化过程 相似文献
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二甲基醚/甲醇双燃料均质压燃低温氧化反应机理数值模拟 总被引:1,自引:0,他引:1
应用零维详细化学反应动力学模型,研究了二甲基醚(DME)/甲醇双燃料均质压燃低温氧化反应机理,考察了初始温度、甲醇浓度和二甲基醚浓度对低温氧化反应的影响.结果表明,甲醇改变了二甲基醚低温反应途径,二甲基醚的低温和二次加氧过程受到抑制,CH3OCH2直接裂解(β-scission)起主导作用,二甲基醚与甲醇高温反应几乎同时进行.温度升高,高温脱氢反应和β-scission增强;低温脱氢反应速率增大,反应时刻提前,高温脱氢反应速率先增大后减小,加氧反应速率随着DME浓度增大而增大,β-scission反应速率先增大后减小;甲醇浓度增大,DME低温脱氢反应速率降低,高温脱氢反应速率先增大后降低,β-scission反应速率随甲醇浓度增大而减小,加氧反应速率则随甲醇浓度增加而升高. 相似文献
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The distribution of nitrogen oxides (NOx) flux within the cross-section area in front of ammonia injection grid (AIG) under different operating conditions was obtained by computational fluid dynamics (CFD) method. Weight of NOx flux in the sub-zone corresponding to each of the ammonia (NH3) injection branch-pipes of AIG system was analyzed and the sensitivity of which against the plant power load was figured out. A number of “critical” ammonia injection branch-pipes were determined with regard to the weight sensitivity analysis. The selected “critical” branch-pipes were changed to be controlled by the automatic valves, and an intelligent tuning strategy was proposed. The NOx/NH3 mixing stoichiometry over the cross-section area in front of AIG system was significantly modified for the high utilization ratio of ammonia. A case work was launched on the selective catalytic reduction (SCR) system of a 660 MW plant. As a result, the ammonia consumption rate (ACR) was found to be reduced by 6.44% compared to that under previous control system, and was 9.31% lower than that of the unapplied system. The methodology for determining the “critical” branch-pipes and intelligent tuning strategy of ammonia injection notably saved the ammonia consumption of SCR system, and the formation of ammonium bisulfate (ABS) were greatly confined. 相似文献