NOx control in large-scale power plant boilers through superfine pulverized coal technology

Superfine pulverized coal technology can effectively reduce NO _x emission in coal-fired power plant boilers. It can also economize the cost of the power plant and improve the use of the ash in the flue gas. Superfine pulverized coal technology, which will be widely used in China, includes common superfine pulverized coal technology and superfine pulverized coal reburning technology. The use of superfine pulverized coal instead of common coal in large-scale power plants will not only reduce more than 30% of NO _x emission but also improve the thermal efficiency of the boiler. __________ Translated from Journal of Shanghai University of Electric Power, 2006, 22(4): 333–337 [译自: 上海电力学院学报]     

Comparison of combustion characteristics of petroleum coke and coal in one-dimensional furnace

The effect of primary air fraction f₁, outer secondary air swirl strength and excess oxygen coefficient on the combustion characteristics of petroleum coke, Hejin lean coal and Shenmu soft coal are researched on a one-dimensional furnace using a dual channel swirl burner. The results show that with the increase in primary air fraction f₁, the NO_x emission concentrations of both Hejin lean coal and petroleum coke increase, and the combustion worsens in the earlier stage, but the burn-out rate of Shenmu soft coal is improved. The NO_x emission concentration obtains a minimum value with an increase in f₁. The ignition and burn-out rate of petroleum coke and Shenmu soft coal are optimal when Ω_dl is minimum and Ω_dl=0.87, respectively. However, both the NO_x emission concentration of petroleum coke and Shenmu soft coal are minimum when Ω_dl=1.08. The increase in excess oxygen coefficient delays the ignition of petroleum coke, worsens the combustion condition and increases the NO_x emission concentration, but it greatly decreases the NO_x emission concentration of Shenmu soft coal.     

温度对超细煤焦再燃还原NO效率的影响

以超细煤粉制作的煤焦作为再燃燃料,用N2、O2、CO2、NO配制模拟烟气,在立式管式携带炉中,研究了温度对再燃降低NO效率的影响。结果表明,在实验温度范围内,随着再燃区温度的增加,再燃还原NO效率增大,化学动力学是控制超细煤粉再燃还原NO化学反应速率的重要因素;提高再燃区温度可以适当缩短停留时间,但不能低于0.6 s,否则NO还原效率会大幅度下降,同时燃尽率也会下降;在煤粉再燃过程中,煤焦再燃还原NO占有重要地位。     

燃煤电厂全过程低碳节能技术路径探讨

  目的  燃煤电厂的低碳节能路径是缓解我国能源危机与环境污染的重要策略。  方法  文章评述了当前燃煤电厂在燃料供应设计阶段和节能运行维护阶段的低碳节能技术以及低碳技术潜在的发展方向。  结果  对于电厂燃料供应设计阶段的低碳技术应优化生物质/氨与煤的掺烧比例,良好的掺烧比例有利于炉内充分燃烧,降低碳排;电厂节能运行维护阶段吸收技术、吸附技术和气体分离技术是碳颗粒捕集的常用手段,同时储能技术、深度调峰技术、柔性直流供电技术对于CO₂减排具有重要作用。  结论  对电厂低碳技术发展进行展望,认为采用综合互补低碳协同方式,并结合电厂运行过程中的监管反馈调控措施,将是促进电厂可持续能源发展的重要发展方向。     

低低温电除尘及高效电源协同烟气处理技术的应用

为研究低低温电除尘及高效电源协同烟气处理技术的应用效果,以一循环流化床锅炉为研究对象,通过试验方法,对协同烟气处理技术投运前后烟气中的粉尘颗粒特性及排放质量浓度进行了测量及对比,并对该技术投运后的经济性进行了分析。结果表明:协同烟气处理技术投运后,机组排放的粉尘质量浓度由49.5 mg/m³降低至10.7 mg/m³,可显著提高除尘器的除尘效率;可降低机组供电标煤耗2.835 g/(kW·h),年节煤量1473.5 t;可进一步减少CO₂,SO₂,NO_x及粉尘等污染物的排放;可节约用电160 kW·h/h,每年节约电量6.16×10⁵ kW·h。     

超细煤粉燃烧氮氧化物释放特性的研究

通过试验和数值模拟，对超细煤粉在一维热态煤粉炉内燃烧时煤粉粒度、炉膛温度、过量空气系数、煤种等因素对NOx释放特性的影响规律进行了研究。研究结果表明：超细煤粉NOx的排放浓度低于常规粒度煤粉；NOx的排放浓度，随过量空气系数的增加而明显增加；煤种不同，NOx释放规律不同，煤粉超细化后，龙口褐煤的排放量明显减少，晋城无烟煤则变化不大；NOx的排放浓度随温度的升高而升高，但温度升高到一定值后，NOx的排放浓度却呈现下降趋势。以超细煤粉作为再燃燃料，NOx的还原率将比常规粒度煤粉再燃有所提高，褐煤作为再燃燃料时，效果更明显。模拟计算与试验结果较为吻合。图6表2参2     

Assessment of cleaner electricity generation technologies for net CO2 mitigation in Thailand

The choice of electricity generation technologies not only directly affects the amount of CO₂ emission from the power sector, but also indirectly affects the economy-wide CO₂ emission. It is because electricity is the basic requirement of economic sectors and final consumptions within the economy. In Thailand, although the power development plan (PDP) has been planned for the committed capacity to meet the future electricity demand, there are some undecided electricity generation technologies that will be studied for technological options. The economy-wide CO₂ mitigations between selecting cleaner power generation options instead of pulverized coal-thermal technology of the undecided capacity are assessed by energy input–output analysis (IOA). The decomposition of IOA presents the fuel-mix effect, input structural effect, and final demand effect by the change in technology of the undecided capacity. The cleaner technologies include biomass power generation, hydroelectricity and integrated gasification combined cycle (IGCC). Results of the analyses show that if the conventional pulverized coal technology is selected in the undecided capacity, the economy-wide CO₂ emission would be increased from 223 million ton in 2006 to 406 million ton in 2016. Renewable technology presents better mitigation option for replacement of conventional pulverized coal technology than the cleaner coal technology. The major contributor of CO₂ mitigation in cleaner coal technology is the fuel mix effect due to higher conversion efficiency. The demand effect is the major contributor of CO₂ mitigation in the biomass and hydro cases. The embedded emission in construction of power plant contributes to higher CO₂ emission.     

O2/CO2粉煤燃烧技术的过程分析及烟气排放控制Q

目前减少CO2排放潜力较大、可行性较好的CCS、IGCC都离不开CO2的捕集技术。新型O2/CO2粉煤燃烧技术可以将排放烟气中的CO2浓度提高到95%,并使高温烟气回流,减少热量损失,同时又减少SO2、NOx等污染物的排放。与传统的O2/N2煤燃烧技术相比,O2/CO2粉煤燃烧技术增加了空气分离装置和烟气循环回流工艺。燃烧反应器中的主要反应包括有机物的燃烧反应、矿物质的氧化反应、脱硫剂的硫化反应等。高温烟气循环代替空气参与煤的燃烧反应能够减少能量损失,但减少的部分并不等于原有工艺排放的高温N2所带走的热损失,模型求解为Q=QA-QB。O2/CO2粉煤燃烧技术的主要优势体现在CO2高浓度捕集和液化储存环节,液化电耗约只有3%的下降,而传统技术液化电耗则可下降约27.8%左右,再加上减少的热损失,其经济性更加明显。O2/CO2粉煤燃烧技术可以对O2流量进行控制,使得不同质量的煤都得到充分燃烧。同时能够根据要求控制反应过程中排放的CO2、SO2、NOx中任意单个污染物的摩尔百分含量,通过求解目标函数f=f（XCO2,XSO2,XNOx,XCO,XH2O,…）,使其达到最优值。     

一维火焰燃烧过程过程中SNCR脱硝试验研究

试验研究了一维火焰燃烧炉内不同条件下选择性非催化还原法(SNCE)的脱硝特性,探讨了结构参数和运行参数对脱硝的影响,在试验基础上得出了SNCR的脱硝规律。试验表明:液氨与尿素作为还原剂时,液氨的脱硝效率稍高,温度窗口的选择至关重要,试验中适宜的窗口温度在900℃～1 000℃之间,NH3/NOx的最佳比例在1.0～1.6之间,停留时间在1s左右。     

积极开展核电研究开辟能源新途径

核电是一种安全、低碳、功率密度高、可大规模利用的能源,具有高效和CO2等化学气体零排放的优点.从中国核电站建设政策推进,核电站安全性,核电技术特别是中国"华龙一号"和小型多功能模块式压水堆ACP100"玲龙一号"核电站技术的建设、运营和效益等各方面在内陆建站的概况,利用核电和H2对有关产业实现CO2超低排放和零排放的影...     

高温低氧气氛下煤粉燃烧低NOx排放特性研究

燃煤工业锅炉作为NOx的主要排放源之一,减排刻不容缓。介绍了煤粉燃烧过程中燃料型NOx、热力型NOx和快速型NOx的生成机理,并对煤中挥发分N及焦炭N对NOx的还原机制进行了探讨。同时,开展了工业锅炉高效低NOx液态排渣煤粉清洁燃烧技术的研究和工程应用实践。结果表明,在高温低氧气氛下,煤粉燃烧过程中能有效抑制NOx生成,并促使NOx还原成N2的有利因素,能够实现NOx排放低于150 mg/m^3的目标。     

An expert system for startup optimization of combined cycle powerplants under NOx emission regulation and machine lifemanagement

This paper proposes an expert system which optimizes the startup schedule for gas and steam turbine combined cycle power plants. The speed-up and load-up pattern of the plant is automatically optimized through an iterative process. Plant dynamics models representing quantitative knowledge and fuzzy rules representing qualitative knowledge are alternately used in the optimization process to modify the schedule parameters. The rules represent expertise on causal relations between modification rates of the schedule parameters and operational margins for constraints, i.e. NO_x emission and machine thermal stresses. Simulation analysis with a three pressure staged reheat type 235.7 MW rated capacity plant shows that the system provides quick and economical plant startup under NO_x emission regulation and reliable machine life management. Startup energy loss is reduced due to the reduction in startup time. Furthermore, optimum operating conditions are quickly reached with the expert system     

粉煤加压气化小型试验研究

煤气化技术是燃煤联合循环发电、煤化工、综合利用系统、近零排放系统中的核心技术。干煤粉加压氧气气化技术是煤气化技术发展的一个主流方向。介绍了国电热工研究院的干煤粉加压气化试验系统,以及干煤粉加压气化试验研究的过程和结果。试验结果达到了预期的目的,得到干煤粉加压气化过程的规律,并验证了试验系统在高压下的稳定性。     

Combustion technology developments in power generation in response to environmental challenges

Combustion system development in power generation is discussed ranging from the pre-environmental era in which the objectives were complete combustion with a minimum of excess air and the capability of scale up to increased boiler unit performances, through the environmental era (1970–), in which reduction of combustion generated pollution was gaining increasing importance, to the present and near future in which a combination of clean combustion and high thermodynamic efficiency is considered to be necessary to satisfy demands for CO₂ emissions mitigation.

From the 1970s on, attention has increasingly turned towards emission control technologies for the reduction of oxides of nitrogen and sulfur, the so-called acid rain precursors. By a better understanding of the NO_x formation and destruction mechanisms in flames, it has become possible to reduce significantly their emissions via combustion process modifications, e.g. by maintaining sequentially fuel-rich and fuel-lean combustion zones in a burner flame or in the combustion chamber, or by injecting a hydrocarbon rich fuel into the NO_x bearing combustion products of a primary fuel such as coal.

Sulfur capture in the combustion process proved to be more difficult because calcium sulfate, the reaction product of SO₂ and additive lime, is unstable at the high temperature of pulverized coal combustion. It is possible to retain sulfur by the application of fluidized combustion in which coal burns at much reduced combustion temperatures. Fluidized bed combustion is, however, primarily intended for the utilization of low grade, low volatile coals in smaller capacity units, which leaves the task of sulfur capture for the majority of coal fired boilers to flue gas desulfurization.

During the last decade, several new factors emerged which influenced the development of combustion for power generation. CO₂ emission control is gaining increasing acceptance as a result of the international greenhouse gas debate. This is adding the task of raising the thermodynamic efficiency of the power generating cycle to the existing demands for reduced pollutant emission. Reassessments of the long-term availability of natural gas, and the development of low NO_x and highly efficient gas turbine–steam combined cycles made this mode of power generation greatly attractive also for base load operation.

However, the real prize and challenge of power generation R&D remains to be the development of highly efficient and clean coal-fired systems. The most promising of these include pulverized coal combustion in a supercritical steam boiler, pressurized fluid bed combustion without or with topping combustion, air heater gas turbine-steam combined cycle, and integrated gasification combined cycle. In the longer term, catalytic combustion in gas turbines and coal gasification-fuel cell systems hold out promise for even lower emissions and higher thermodynamic cycle efficiency. The present state of these advanced power-generating cycles together with their potential for application in the near future is discussed, and the key role of combustion science and technology as a guide in their continuing development highlighted.     

中心大速差射流降低NOx排放量的实验研究

在实验室的卧式煤粉炉中，对中心大速差射流是否能降低ＮＯｘ排放量进行了实验研究。实验表明：中心大速差射流不仅能明显降低ＮＯＸ排放量，而且可使煤粉提前着火，从而提高了煤粉燃烧的稳定性。该方法若用于煤粉锅炉的最上一层的燃烧器，则可望在降低ＮＯＸ排放量的同时不影响锅炉的燃烧效率。     

某电厂220t/h锅炉煤粉燃烧器改造设计方案

为提高某电厂220t/h煤粉锅炉燃烧器低负荷稳燃能力，拟采用浓淡燃烧技术对该炉燃烧器进行改造；下层燃烧器采用水平浓淡燃烧器，上层燃烧器采用上下浓淡燃烧器；为保证低负荷时的主蒸汽温度，上层燃烧器为摆动式燃烧器。     

蓄热式热氧化技术在煤制气低温甲醇洗尾气治理中的应用

通过蓄热式热氧化(RTO)技术在煤制气低温甲醇洗尾气治理项目中的实际应用,证明采用RTO技术处理低温甲醇洗尾气可稳定可靠地达到GB 31571—2015《石油化学工业污染物排放标准》的排放要求,且NO_x排放值极低,说明RTO技术能够有效控制高温氧化过程中NO_x的生成;RTO技术可实现极高的热回收效率,从而通过余热回收利用副产蒸汽,实现项目的正收益。     

锅炉氧煤无焰燃烧技术分析

氧煤燃烧是一种全新燃烧方式,将氧煤燃烧器的表观氧气浓度从30％提高到50％、将O2/CO2混合气改变为纯氧气与再循环CO2烟气分离、将喷嘴速度从50m/s左右提高到200 m/s左右组织炉膛烟气形成高倍率内循环,从而在炉膛内实现高温低氧的氧煤无焰燃烧状态,氧煤无焰燃烧技术能实现煤粉高效燃烧和较低NO浓度排放的统一,锅炉...     

四角切向燃烧锅炉煤粉射流逆向稳燃技术的研究开发

本文首次提出并分析了四角切向燃烧锅炉煤粉射流逆向稳燃技术的设计思想。根据炉内三维湍流流场的数值模拟，优化设计了本项技术应用于焦作电厂Ｎｏ．３炉的燃烧器改造方案。计算结果及现场应用证实，采用煤粉射流逆向稳燃技术能够大幅度延长一次风射流中煤粉颗粒在着火初期的停留时间，改善煤粉气流的着火条件，同时能够有效地削弱炉膛出口气流的残余旋转，从而减轻烟温偏差，并能改变煤粉颗粒的切圆运动轨迹，从而缓解了炉膛燃烧器区域水冷壁的结渣与高温腐蚀。     

双强少油煤粉点火燃烧技术在600 MW锅炉上的应用

鹤壁丰鹤发电厂2×600 MW机组引进了双强少油煤粉点火燃烧技术,经试运行以来的多次试验证明,改造优化后锅炉燃烧投粉的时同提前,锅炉启动稳燃及节油效果相当明显,提高了电厂的经济效益.改造应用经验可为同类型机组的改造及经济运行提供参考.