尿素为还原剂燃煤烟气脱硝技术的研究与应用

尿素由于运输、储存安全性较高,作为还原剂进行脱硝备受关注。从工艺原理、系统组成和工程应用等方面,对尿素制氨选择性催化还原技术（SCR）、选择性非催化还原技术（SNCR）和尿素法三种脱硝方法进行了综述。分析了不同技术运用过程存在的问题,并提出解决措施。     

SNCR-SCR烟气脱硝技术及其应用

SNCR-SCR烟气脱硝技术是结合了SCR技术高效、SNCR技术投资省的特点而发展起来的一种新型、成熟的工艺.详细介绍了混合SNCR-SCR工艺的特点,并结合台湾某电厂的运行资料,将这种工艺与单一SCR和SNCR工艺进行了技术经济比较.     

氨水还原剂在燃煤锅炉SCR脱硝中的应用

目前氨水作为脱硝还原剂用于燃煤锅炉SCR脱硝国内尚未普遍使用,尤其在大机组上的应用经验较少。通过对实际应用案例的分析,总结了运行经验,为氨水还原剂在大机组SCR的脱硝应用提供参考。     

燃煤电站SNCR脱硝系统喷射还原剂介质对锅炉效率的影响

以燃煤电厂1台600MW机组配套SNCR脱硝系统为例,分别介绍了采用尿素、液氨为SNCR脱硝还原剂时,各还原剂的喷入量对锅炉效率和燃煤成本的影响。结果发现,以设计煤种Qnet,ar=11766.7kJ/kg计,当浓度5%的尿素溶液喷入时,有1.67%的燃煤发热量被水蒸发所吸收,导致排烟损失增加0.6659%。假设其他损失不变,不计固体尿素的升温、分解热反应等的影响,尿素溶液的喷入对锅炉热效率的影响在0.6659%左右,燃煤成本约增加900多万元/a;在喷入氨空混合气情况下,约0.2%的燃煤发热量被混合气所吸收,导致排烟损失增加0.02%。假设其他损失都不变,不计分解热反应等的影响,混合气的喷入对锅炉的热效率的影响亦即在0.02%左右,燃煤成本约增加30万元/a。从节能的角度看,液氨为还原剂应作为优选。     

选择性非催化还原烟气脱硝技术在流化床锅炉上应用的探讨

对选择性非催化还原（SNCR）烟气脱硝技术与选择性催化还原（SCR）烟气脱硝技术在流化床锅炉上应用的适应性进行了对比分析。分析结果显示,相对于SCR技术,SNCR技术更适于流化床锅炉,指出了SNCR技术在流化床锅炉上应用存在的问题,N2O难以去除。     

火电厂降低NOx排放的技术研究

NOx是燃煤电厂烟气排放三大有害物（SO2、NOx及悬浮颗粒物TSP）之一。从污染角度考虑的氮氧化物主要是NO和NO2,统称为NOx。介绍了NOx的生成机理,即热力型NOx和燃料型NOx,前者由参与燃烧的空气中所含的N2生成,后者由燃料本身的氮元素生成。分析了低氮燃烧技术、SCR烟气脱硝技术、SNCR烟气脱硝技术及SCR＋SNCR组合式等NOx控制技术。其中,在燃烧过程中降低NOx生成的主要手段是采用分级燃烧,降低燃烧区域的氧浓度和降低火焰温度;在燃烧后可采用烟气处理技术降低烟气中的NOx含量。     

火电厂烟气脱硝技术及其设备国产化建议

对目前主流的选择性催化氧化还原法(SCR)、选择性非催化氧化还原法(SNCR)脱硝工艺特点和设计要求进行了较为详细的论述，并结合苏源环保公司在FGD装置国产化方面的经验，对烟气脱硝技术自主化、装备国产化提出了若干建议。     

烟气脱硝工艺及其化学反应机理

概述了工业固定源NOx的控制措施，包括燃烧过程控制和燃烧后减少NOx排放。介绍两种主要的烟气脱硝工艺SNCR和SCR的特点、布置及所要求的温度范围，正在商业化应用的SCR工艺的催化荆组成、活性组分及其他组分的作用。提出了这一催化体系中还需要进一步澄清的某些化学机理。     

宁海电厂烟气脱硝控制技术介绍

随着燃煤火力发电厂的大量新建和投产,节能减排的工作日益重要,对燃煤电厂的环保要求也越来越高.概述了烟气脱硝的主导工艺--选择性催化还原(SCR)法在燃煤电厂的应用,重点介绍了脱硝过程自动控制的特点和配置情况.     

嵩屿电厂烟气SCR脱硝工艺及特点分析

介绍了厦门嵩屿电厂4×300MW燃煤机组烟气选择性催化还原法(SCR)脱硝工程所选用的工艺,分析了SCR脱硝系统的主要技术特点,为日益增多的同类型脱硝装置的工艺设计与设备选型提供一定的借鉴。     

Variability of nitrous oxide and carbon dioxide emissions continuously measured in solid waste incinerators

Nitrous oxide and carbon dioxide were continuously measured and variability of emission factors (EFs) was evaluated in five municipal waste incinerators (MWIs) and four industrial waste incinerators (IWIs) from 24 to 86 days between 2008 and 2011. N₂O EFs were calculated by Monte Carlo simulation and mean N₂O EFs were 7.1, 107, 127, 219 g N₂O/ton waste combusted in MWIs with selective catalytic reduction (SCR) for NOx control, MWIs with selective non-catalytic reduction (SNCR), IWIs with SNCR, and a MWI using fluidized bed with SNCR, respectively. Climate-relevant CO₂ EFs ranged from 0.45 to 0.72 ton CO₂/ton waste combusted in MWIs. Maximum values of upper limit for 95% confidence intervals (CIs) of N₂O EFs estimated in each MWIs with SCR, MWIs with SNCR, IWIs with SNCR were 185, 94, 101% of mean N₂O EFs, respectively. Meanwhile, maximum values of upper limit for 95% CIs of CO₂ EFs were much lower as between 18 and 36% in those facilities. 84% CIs of mean N₂O EFs in MWIs with SNCR and IWIs with SNCR were overlapped indicating those values are not significantly different.     

Effect of mixing on NO removal in the selective noncatalytic reduction reaction process

The effect of mixing of NH₃ and NO on the selective noncatalytic reduction (SNCR) reaction was investigated using a bench-scale reactor. Three different experimental conditions were compared for the removal of NO in the bulk gas with NH₃, a reducing agent, by means of mixing and contacting. The temperature that gave the highest NO removal efficiency was about 800°C when NH₃ was injected with air or NH₃ was premixed and air was injected. It is suggested that control of mixing of the reducing agent and the injection conditions could be a good way to increase NO removal efficiency as well as to lower the reaction temperature. When NH₃ was injected with air, the NO removal efficiency increased with increasing injected air flow if the initial NO concentration was low, whereas for high NO concentrations, the NO removal efficiency slightly increased up to an injected air flow rate of 100 ml/min. A proposed mixed-flow model can be used as a prediction tool for the NO removal efficiency covering various conditions of the real SNCR process.     

Nitrous oxide (N2O) emissions from waste and biomass to energy plants.

Following the Kyoto protocol with respect to reducing emissions of greenhouse gases emissions, and EU energy policy and sustainability in waste management, there has been an increased interest in the reduction of emissions from waste disposal operations. From the point of view of nitrous oxide (N2O) emissions, waste incineration and waste co-combustion are very acceptable methods for waste disposal. In order to achieve very low N2O emissions from waste incineration, particularly for waste with higher nitrogen content (e.g. sewage sludge), two factors are important: temperature of incineration over 900 degrees C and avoiding the selective non-catalytic reduction (SNCR) de-NO(X) method based on urea or ammonia treatments. The more modern selective catalytic reduction (SCR) systems for de-NO(X) give rise to negligible sources of N2O.     

选择性非催化还原烟气脱硝工艺在利港电厂4×600MW机组上的应用

介绍了选择性非催化还原脱硝技术（SNCR）在利港发电股份有限公司4×600MW机组脱硝工程上的应用情况,分析了SNCR工艺的反应原理、工艺流程、特点以及系统调试和运行情况。     

CFD simulation of MSW combustion and SNCR in a commercial incinerator

A CFD scheme was presented for modeling municipal solid waste (MSW) combustion in a moving-grate incinerator, including the in-bed burning of solid wastes, the out-of-bed burnout of gaseous volatiles, and the selective non-catalytic reduction (SNCR) process between urea (CO(NH₂)₂) and NO_x. The in-bed calculations provided 2-D profiles of the gas–solid temperatures and the gas species concentrations along the bed length, which were then used as inlet conditions for the out-of-bed computations. The over-bed simulations provided the profiles of incident radiation heat flux on the top of bed. A 3-dimensional benchmark simulation was conducted with a 750 t/day commercial incinerator using the present coupling scheme incorporating with a reduced SNCR reduction mechanism. Numerical tests were performed to investigate the effects of operating parameters such as injection position, injection speed and the normalized stoichiometric ratio (NSR) on the SNCR performance. The simulation results showed that the distributions of gas velocity, temperature and NO_x concentration were highly non-uniform, which made the injection position one of the most sensitive operating parameters influencing the SNCR performance of moving grate incinerators. The simulation results also showed that multi-layer injections were needed to meet the EU2000 standard, and a NSR 1.5 was suggested as a compromise of a satisfactory NO_x reduction and reasonable NH₃ slip rates. This work provided useful guides to the design and operation of SNCR process in moving-grate incinerators.     

烟气脱硝技术的研究

氮氧化物(NOx)的污染危害是一个不容忽视的问题.目前,我国燃煤电厂排放烟气的SO2治理已逐步走向正轨,新建的燃煤电厂基本都安装效率较高的脱硫装置.因此,控制NOx的排放将是下一步的主要任务.对选择性催化还原法(SCR)、非选择性催化还原法(SNCR)、电子束或电晕放电脱硝法、光催化氧化法等烟气中NOx控制技术的机理、现状、发展趋势和主要优缺点进行了详尽的论述.通过对各种工艺技术的脱除效率、应用条件、经济性等方面的分析、比较和总结,提出了未来脱硝技术研究工作的重点.基于我国的实际情况提出了烟气脱硝的可行方案,从而为工业废气脱硝技术的进一步开发和研究提供参考.