Experimental Study on Ammonia Co-Firing with Coal for Carbon Reduction in the Boiler of a 300-MW Coal-Fired Power Station

To reduce CO_(2) emissions from coal-fired power plants,the development of low-carbon or carbon-free fuel combustion technologies has become urgent.As a new zero-carbon fuel,ammonia(NH_(3))can be used to address the storage and transportation issues of hydrogen energy.Since it is not feasible to completely replace coal with ammonia in the short term,the development of ammonia-coal co-combustion technology at the current stage is a fast and feasible approach to reduce CO_(2) emissions from coal-fired power plants.This study focuses on modifying the boiler and installing two layers of eight pure-ammonia burners in a 300-MW coal-fired power plant to achieve ammonia-coal co-combustion at proportions ranging from 20%to 10%(by heat ratio)at loads of 180-to 300-MW,respectively.The results show that,during ammonia-coal co-combustion in a 300-MW coal-fired power plant,there was a more significant change in NO_(x) emissions at the furnace outlet compared with that under pure-coal combustion as the boiler oxygen levels varied.Moreover,ammonia burners located in the middle part of the main combustion zone exhibited a better high-temperature reduction performance than those located in the upper part of the main combustion zone.Under all ammonia co-combustion conditions,the NH_(3) concentration at the furnace outlet remained below 1 parts per million(ppm).Compared with that under pure-coal conditions,the thermal efficiency of the boiler slightly decreased(by 0.12%-0.38%)under different loads when ammonia co-combustion reached 15 t·h^(-1).Ammonia co-combustion in coal-fired power plants is a potentially feasible technology route for carbon reduction.

SO_2 emission characteristics from co-firing of petroleum coke and coal in circulating fluidized bed

Combustion and sulfur retention experiments of mixed fuel of petroleum cokeand coal were conducted on a pilot-scale circulating fluidized bed (CFB) combustor with the thermalinput of 0. 6 MW. The effects of several parameters, such as the primary air percentage, excess aircoefficient, bed temperature, Ca/S molar ratio and mass ratio of petroleum coke to coal on SO_2emission were verified. Experimental results show that when the ratio of petroleum coke to coal inthe mixed fuel increases, the SO_2emission increases. The maximum SO_2 emission appears when purecoke burns. The SO_2 concentration in flue gas reduces with the increase in the primary airpercentage, excess air coefficient and Ca/S molar ratio for all kinds of fuel mixtures. Therangebetween 830 t and 850 t is the optimal temperature for sulfur retention during co-firing ofpetroleum coke and coal with the mass ratio R of 1 and 3 in CFB.

Co-firing of coal and biomass in oxy-fuel fluidized bed for CO2 capture: A review of recent advances

The co-firing of coal and biomass in oxy-fuel fluidized beds is one of the most promising technologies for capturing CO2.This technology has attracted wide attention from academia and industry in recent years as a negative emission method to capture CO2 produced by carbon contained in biomass.In the past decades,many studies have been carried out regarding experiments and numerical simulations under oxy-fuel combustion conditions.This paper firstly briefly discusses the techno-economic viability of the biomass and coal co-firing with oxycombustion and then presents a review of recent advancements involving experimental research and computational fluid dynamics(CFD)simulations in this field.Experimental studies on mechanism research,such as thermogravimetric analysis and tube furnace experiments,and fluidized bed experiments based on oxy-fuel fluidized beds with different sizes as well as the main findings,are summarized as a part of this review.It has been recognized that CFD is a useful approach for understanding the behaviors of the co-firing of coal and biomass in oxyfuel fluidized beds.We summarize a recent survey of published CFD research on oxy-fuel fluidized bed combustion,which categorized into Eulerian and Lagrangian methods.Finally,we discuss the challenges and interests for future research.

Waste biomass from production process co-firing with coal in a steam boiler to reduce fossil fuel consumption:A case study

Waste biomass is always generated during the production process in industries. The ordinary way to get rid of the waste biomass is to send them to landfill or burn it in the open field. The waste may potentially be used for co-firing with coal to save fossil fuel consumption and also reduce net carbon emissions. In this case study, the bio-waste from a Nicotiana Tahacum （NT） pre-treatment plant is used as the biomass to co-fire with coal. The samples of NT wastes were analysed. It was found that the wastes were of the relatively high energy content which were suitable for co-firing with coal. To investigate the potential and benefits for adding NT wastes to a Fluidised Bed Combustion （FBC） boiler in the plant, detailed modelling and simulation are carried out using the European Coal Liquefaction Process Simulation and Evaluation （ECLIPSE） process simulation package. The feedstock blending ratios of NT waste to coal studied in this work are varied from 0% to 30%. The results show that the addition of NT wastes may decrease the emissions of CO2 and SOx without reducing the boiler performance.

Flame Morphology and Characteristic of Co-Firing Ammonia with Pulverized Coal on a Flat Flame Burner

Ammonia as a new green carbon free fuel co-combustion with coal can effectively reduce CO_(2)emission,but the research of flame morphology and characteristics of ammonia-coal co-combustion are not enough.In this work,we studied the co-combustion flame of NH_(3)and pulverized coal on flat flame burner under different oxygen mole fraction(X_(i,O_(2)))and NH_(3)co-firing energy ratios(E_(NH_(3))).We initially observed that the introduction of ammonia resulted in stratification within the ammonia-coal co-combustion flame,featuring a transparent flame at the root identified as the ammonia combustion zone.Due to challenges in visually observing the ignition of coal particles in the ammonia-coal co-combustion flame,we utilized Matlab software to analyze flame images across varying E_(NH_(3))and X_(i,O_(2)).The analysis indicates that,compared to pure coal combustion,the addition of ammonia advances the ignition delay time by 4.21 ms to 5.94 ms.As E_(NH_(3))increases,the ignition delay time initially decreases and then increases.Simultaneously,an increase in X_(i,O_(2))results in an earlier ignition delay time.The burn-off time and the flame divergence angle of pulverized coal demonstrated linear decreases and increases,respectively,with the growing ammonia ratio.The addition of ammonia facilitates the release of volatile matter from coal particles.However,in high-ammonia environments,oxygen consumption also impedes the surface reaction of coal particles.Finally,measurements of gas composition in the ammonia-coal flame flow field unveiled that the generated water-rich atmosphere intensified coal particle gasification,resulting in an elevated concentration of CO.Simultaneously,nitrogen-containing substances and coke produced during coal particle gasification underwent reduction reactions with NO_(x),leading to reduced NO_(x)emissions.

Effects of Co-Firing Biomass and Pulverized Coal on NO Reduction in Cement Precalciner

With increased awareness of the large-scale CO_(2) emissions from the cement industry,there has been growing focus on greenhouse gas reduction strategies.Among all these strategies,fuel substitution using biomass fuel is extensively used to achieve CO_(2) zero-emission in cement production.Due to the avoidable high-temperature-generated thermal nitrogen oxides during cement production,research on the impact of biomass application on nitrogen oxide emissions shall be carried out.Three types of biomass fuel and bituminous coal were used to investigate the NO reduction characteristics under different O_(2) concentrations on experimental benches.It was found that the change in oxygen concentration from 9% to 1% increased the reaction time in the reactor from 555 s to 1425 s,which means the increase in oxygen concentration can lead to shorter reaction time,and correspondingly,the existing time of nitric oxide in the flue gas is also shortened,but the peak value of nitric oxide rises,during the process of O_(2) concentration changing from 1% to 9%,the peak NO concentration in the flue gas increased from 5.4×10^(-5) to 1.05×10^(-4).An increase in O_(2) concentration greatly reduces the total reduction of NO and the minimum change in NO concentration.The peak NO concentration during the combustion process of corn stalk is 4.56×10^(-4),which is approximately 7 times higher than that of coal,and it is caused by the high amount of N in corn stalk.The addition of raw meal has an inhibitory effect on the reduction of NO:after adding raw meal,the effective reduction time of NO by fuel decreased by about 20%,but adding raw meal raises CO_(2) concentration of fuel gas in the early stage of reaction.

Simulation analysis of ammonia distribution in methanol production from coal water slurry gasification

Aspen plus software was employed to simulate process. The system concludes gasification scrubbing system the opposed multi-burner gasifier （OMB） methanol production and purification shift system. The distributions of ammonia con- centration in streams were obtained. The study demonstrates that ammonium crystallization problem caused by ammonia ac- cumulation, and if the process has ammonia exports its concentration will greatly reduced and the ammonia salt problem will effectively alleviate. Aspen plus simulation is a useful tool strengthening the ammonia recycling use and reducing pollutant for improving water quality, maintaining stable production, emissions.

Wood Pellet Co-Firing for Electric Generation Source of Income for Forest Based Low Income Communities in Alabama

Alabama imports coal from other states to generate electricity. This paper assessed the direct and indirect economic impacts of wood pellet production to be co-fired with coal for power generation in Alabama. Four sizes of wood pellet plants and regional input-output models were used for the analysis. The results showed that the economic impact increases with the size of the plant. Wood pellet production will have a multiplier effect on the economy especially, forest-related services, retail stores, the health service industry, and tax revenue for the government. Domestic wood pellet production can reduce the use of imported coal, allow the use of local woody biomass, and create economic activities in Alabama’s rural communities. Policies that support the production of wood pellet will serve to encourage the use of wood for power generation and support the rural economies.

双碳背景下燃煤电站掺氨燃烧研究进展与展望

在“双碳”背景下,选择低碳燃料氨对燃煤电站的改造显得尤为重要。该文首先介绍氨的基本物性及其掺烧的优势,随后针对氨煤掺烧技术的新应用,按照燃煤设备的输出功率分类,从微/小型掺氨燃烧器、千瓦级燃煤掺氨燃烧系统、兆瓦级燃煤掺氨燃烧系统,大型燃煤电站掺氨燃烧系统,介绍当前的研究进展。最后,对燃煤电站掺氨燃烧的前景进行分析与展望。燃煤电站掺氨燃烧可大幅降低碳排放,但可能带来NO_x排放问题,通过空气分级、氨预分解、调节氨掺入位置和比例等手段,可以有效控制NO_x排放;目前,仍需解决煤/氨气固两相燃料反应性差异大、NO_(x)浓度高、缺乏大容量高比例燃烧器技术,以及突破“大型给氨+清洁燃氨+灵活运行”的关键技术。

基于初始氨覆盖率寻优的燃煤电站SCR脱硝系统机理建模

随着新能源发电大规模并网,燃煤机组工况快速变化,选择性催化还原(SCR)反应器入口氮氧化物(NO_(x))浓度剧烈波动。传统PID控制已无法满足NO_(x)的超低排放标准,需要建立准确的模型对出口NO_(x)浓度进行预测,以实现快速准确的喷氨量控制。然而,在机理建模的过程中,氨覆盖率这一关键数据因无法测量而缺失,直接影响模型精度。为了解决氨覆盖率缺失的问题,提出了一种名为初始氨覆盖率寻优的方法。采用改进的粒子群优化(IPSO)方法,通过燃煤电厂运行数据对机理模型反应常数和初始氨覆盖率进行校准。结果表明:经过初始氨覆盖率寻优,机理模型预测的出口NO_(x)浓度精度得到了显著提升,典型工况下,测试集平均绝对百分比误差下降了17.1%。

氨煤混燃气相中NO生成的化学反应动力学分析

氨煤混燃涉及复杂的化学反应过程,是否会加剧氮氧化物的生成是倍受关注的问题。通过化学反应动力学计算方法,研究了氨煤混合燃烧的气相反应中NO生成和还原的反应路径,以及不同因素对NO生成的影响。结果表明:温度T=1300℃、过量空气系数α=0.84时,相较于纯煤燃烧,掺氨比例为0.3时能够降低反应器出口NO体积分数96.5%,原因是此工况下氨分解产生大量的NH_(2)和NH等自由基,其还原反应的反应速率更快,从而使含N基元向N_(2)转化;T=1300℃下,掺氨比例为0.3时较为合适,此时反应器出口的NO和NH_(3)体积分数均较低;小比例掺氨燃烧会增大NO的生成速率和NH_(3)的分解速率,导致反应器出口NO体积分数增大,且温度越高,该现象越明显;α<1的还原性气氛和较低的温度(T≤1300℃)能够有效降低NO的排放。

煤气化细渣水热合成多孔材料及对氨氮的吸附性能研究

为了拓展煤气化细渣高值化利用途径,采用碱溶水热法制备多孔复合吸附材料。通过调控碱浓度、水热时间、温度、搅拌时间等因素探究其对复合材料结构性能的影响规律,并通过分析不同制备条件下复合吸附材料的物相组成、表观形貌、孔隙结构,明晰复合材料与其对氨氮吸附能力的构效关系。结果表明:复合材料生成了以P型沸石为主要晶相的沸石结构。当碱浓度为2 mol/L、水热时间为30 h,水热温度为100℃,搅拌时间为10 min制备的复合材料的氨氮吸附量最高,当氨氮初始浓度为100 mg/L、吸附时间为5 h时,复合材料对氨氮的平衡吸附量达到15.65 mg/g。吸附材料对氨氮的等温吸附特性符合Langmuir方程,且反应过程符合准二级动力学方程。热力学分析表明煤气化细渣对氨氮的吸附为自发、吸热及熵增反应。

低碳氨燃料生命周期碳排计算和应用前景探究

文章梳理了低碳氨的燃料属性和特点,测算了目前技术水平下低碳氨生命周期碳排因子,对低碳氨与煤制氨的成本进行了分析,指出随着技术进步成本进一步下降,风光发电制低碳氨燃料经济性将逐步体现,未来具有发展空间。低碳氨生命周期碳排因子生产环节排放占90%以上,生产环节中碳排基本上是制氢和制氮用电导致,因此降低碳排主要方向是减少生产环节用电量和尽可能增加绿电使用量。

分级空气高速射流对煤掺氨燃烧中氨预分解与NO_(x)生成影响

氨作为零碳清洁燃料,对碳减排有重要作用,但其燃烧过程中NO_(x)生成倾向大。针对煤掺氨燃烧NO_(x)生成控制问题,以某50 kW一维试验炉系统所用旋流燃烧器为原型,提出一种内置高速空气射流阵列结构的新型煤掺氨旋流燃烧器结构,以实现炉内氨预分解后燃烧和分级燃烧。进一步用CFD燃烧数值模拟探究空气分级比、过量空气系数及氨燃料喷口尺寸对氨煤掺烧火焰结构及NO_(x)排放影响,优化新型燃烧器结构及运行参数。结果表明,相比于原型燃烧器,采用空间分散高速三次风射流会导致燃烧区域滞后,加深空气分级,减小主燃烧区域局部过量空气系数,抑制氨过度氧化形成NO_(x),也降低火焰温度峰值,利于抑制热力型NO_(x)产生。同时通过调控总过量空气系数使氨热解发生区域沿炉膛轴向逐渐延伸,火焰前部高温欠氧区增大,促进氨受热预分解为N_(2)和H 2,进一步减少氨中燃料氮直接转化形成NO_(x)。空气分级比20∶22∶58时,NO_(x)生成体积分数由原燃烧器的3309×10^(-6)降至新型燃烧器的1069×10^(-6),降幅达67.69%。增大过量空气系数,或过量空气系数不变、控制一次风率不变而增大三次风率将促进上述效应,进一步减少NO生成。氨管内径变化范围仅考虑5~9 mm,氨喷射速度和分散高速三次风带来的协同效应有待进一步研究。

典型高碱煤灰对氨煤混燃中氨氧化反应特性的影响

氨能作为一种零碳燃料,取代部分煤炭混燃可有效降低电厂原有污染物排放,促进燃煤电厂向煤氨混燃电厂的转型。但由于氨能中含氮量过高,导致NO_(x)排放问题备受关注。在复杂的氨煤混燃过程中,有必要探索NO_(x)排放与煤灰之间存在的关联性。燃煤电厂中高碱煤作为一类开发应用前景广阔的煤种,其中高含量的金属氧化物对氨氧化反应的排放特性却鲜有研究。为探讨氨煤混燃过程中不同种类高碱煤灰对氨氧化反应排放特性的影响,通过搭建立式管式炉氨氧化反应试验平台进行变工况分析,对比不同温度下各类煤灰表面NH_(3)转化率及NO生成率两大指标,从试验结果和反应机理2个层面阐述了煤灰中各类金属氧化物对氨氧化反应排放特性的影响。结果表明:煤灰中主要金属氧化物CaO、MgO及Al_(2)O_(3)可促进氨煤混燃过程中煤灰表面气固氨氧化反应的进行,提高NH_(3)转化率。400~600℃,煤灰对NH_(3)转化率的促进作用依次为:HM-2>HM-1>CJ>AKS>EERDS,与煤灰中CaO含量由高到低的排列顺序对应,与MgO排序基本吻合。且这3类金属氧化物均可促进NH_(3)向NO定向转化,以CaO催化效果最显著,其中,Ca含量最高的HM-2对NO生成的选择性相较于空白组而言可提高67.86%。CaO和MgO可促进NH_(3)和NO在催化剂表面氧化,有利于N_(2)O快速产生,使N_(2)O生成温度提前,而Na_(2)O和Fe_(2)O_(3)的存在则抑制NH_(3)氧化,促进NH_(3)还原NO。

变换冷凝液汽提装置的作用及优化分析

介绍了变换冷凝液汽提装置在保证气化和变换运行稳定性中的作用,并结合项目实践分析了汽提装置运行中的痛难点。针对某大型IGCC煤气化项目的优化,提出了一体式闭式汽提流程有助于解决变换汽提装置运行的问题,实现气化和变换水系统氨氮含量的有效控制,同时起到良好的节能降耗效果并降低业主运行维护的成本。

煤炭掺氨燃烧基础研究与技术应用研究进展

能源安全和“双碳”目标影响着全球能源产业链供应链,对我国能源电力系统的安全高效和绿色低碳转型提出了迫切的要求。为保障能源安全,煤电在未来相当长一段时间内仍是我国电力供应安全及可再生能源消纳的重要支撑。为实现碳中和,能源系统逐渐从主要依赖化石能源转向以可再生能源为主,但可再生能源的间歇性、随机性、波动性特点使得电力系统调节更加困难,系统平衡和安全问题更加突出。在这种情况下,以氨为代表等零碳燃料在处理可再生能源的间歇性方面发挥着不可或缺的作用,其既可作为长时大规模储能的载体来实现可再生能源大规模消纳,又可灵活地用在锅炉等动力设备中直接替代燃用。然而,由于零碳燃料与化石燃料在理化性质上的差异,导致零碳燃料在燃用过程中存在如火焰稳定性差、易生成氮氧化物等问题,给氨燃料的大规模利用带来了挑战。为此,从煤炭掺氨燃烧的可行性、经济性和必要性出发,对氨煤共燃的化学反应动力学、燃烧特性(着火、稳燃)和污染物生成特性(NO_(x)、飞灰颗粒物和碳烟生成)进行了全面综述,并讨论了以无量纲准则数为基础的燃烧器模化放大准则,详细探讨了现有工业级氨煤燃烧器高效稳定燃烧控制策略,C—N燃料分级、空气分级及其联合控制均有效降低NO_(x)的排放,未来融合人工智能、大数据及数字孪生等信息化技术,有望从源头为下一代面向双碳战略的新型绿色动力发电系统的研发提供科学支撑和路径参考。

煤粉掺氨空气分级燃烧排放特性及炉内过程烟气特性试验

以往针对氨煤掺烧研究多集中在数值模拟及小型试验炉,大型试验炉上多为技术可行性的点工况试验。在一台50 kW自持燃烧下行试验炉中在不同工况下针对燃煤掺氨燃烧产物的排放和过程分布特性展开研究,重点分析了不同掺氨比例、燃尽风率及运行氧量的影响。为充分了解氨与煤燃烧过程中对NO生成的贡献,针对纯氨燃烧进行一系列试验。试验结果表明,空气分级燃烧可大幅降低燃煤掺氨燃烧NO的排放,掺氨比例为10%~90%时NO排放质量浓度在170~215 mg/m^(3),同纯煤燃烧NO排放质量浓度处于同一水平;最佳燃尽风比率维持在38%附近,继续增大燃尽风比率不会进一步降低NO排放,反而会导致燃烧不充分等负面影响。纯氨燃烧利用空气分级技术可以很好地控制出口NO浓度,但纯氨燃烧稳定性远不及氨煤掺混燃烧,运行氧浓度较低时易出现氨逃逸现象。燃煤掺混氨燃烧既可解决氨燃烧困难、出口NO排放浓度过高的问题,又可减少燃煤CO_(2)排放,是一项极具潜力的技术路线。

厌氧氨氧化处理煤化工酚氨废水的研究进展

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