Mercury Emission From Coal-fired Power Plants in China

燃煤是最大的人为汞排放源之一，燃煤电厂的汞排放控制问题也越来越为人们所关注。该文将目前公布的中国电厂的汞排放数据进行筛选汇总，得到18个电厂的汞排放数据，通过对比和分析，总结出了符合我国燃煤电厂特点的一般性汞排放规律。结果表明：与美国煤种相比，我国的燃煤具有低氯、高灰的特性，这不利于汞的排放控制；循环流化床燃烧可能会因燃尽率的不同而较煤粉炉燃烧易获得较高的Hgp；空气污染控制设备的使用能够有效地减少汞排放，选择性催化还原＋静电除尘器／布袋除尘器＋石灰石-石膏湿法脱硫（SCR＋ESP／FF＋WFGD）组合的平均脱汞率可达71．48％；SCR的大规模应用可能会将汞大量转移到飞灰和脱硫石膏中，带来二次污染的问题。

Sliding Mode Predictive Control of Main Steam Pressure in Coal-fired Power Plant Boiler

Since the combustion system of coal-fired boiler in thermal power plant is characterized as time varying, strongly coupled, and nonlinear, it is hard to achieve a satisfactory performance by the conventional proportional integral derivative (PID) control scheme. For the characteristics of the main steam pressure in coal-fired power plant boiler, the sliding mode control system with Smith predictive structure is proposed to look for performance and robustness improvement. First, internal model control (IMC) and Smith predictor (SP) is used to deal with the time delay, and sliding mode controller (SMCr) is designed to overcome the model mismatch. Simulation results show the effectiveness of the proposed controller compared with conventional ones.

Study on Coal Consumption Curve Fitting of the Thermal Power Based on Genetic Algorithm

Coal consumption curve of the thermal power plant can reflect the function relationship between the coal consumption of unit and load, which plays a key role for research on unit economic operation and load optimal dispatch. Now get coal consumption curve is generally obtained by least square method, but which are static curve and these curves remain unchanged for a long time, and make them are incompatible with the actual operation situation of the unit. Furthermore, coal consumption has the characteristics of typical nonlinear and time varying, sometimes the least square method does not work for nonlinear complex problems. For these problems, a method of coal consumption curve fitting of the thermal power plant units based on genetic algorithm is proposed. The residual analysis method is used for data detection;quadratic function is employed to the objective function;appropriate parameters such as initial population size, crossover rate and mutation rate are set;the unit’s actual coal consumption curves are fitted, and comparing the proposed method with least squares method, the results indicate that fitting effect of the former is better than the latter, and further indicate that the proposed method to do curve fitting can best approximate known data in a certain significance, and they can real-timely reflect the interdependence between power output and coal consumption.

Formation and emission characteristics of VOCs from a coal-fired power plant

On-site measurements of volatile organic compounds(VOCs)in different streams of flue gas were carried out on a real coal-fired power plant using sampling bags and SUMMA canisters to collect gas samples,filters to collect particle samples.Gas chromatography-flame ionization detector/mass spectrometry and gas chromatography-mass spectrometry was the offline analysis method.We found that the total mass concentration of the tested 102 VOC species at the outlet of wet flue gas desulfuration device was(13456±47)μg·m^(-3),which contained aliphatic hydrocarbons(57.9%),aromatic hydrocarbons(26.8%),halogen-containing species(14.5%),and a small amount of oxygen-containing and nitrogencontaining species.The most abundant species were 1-hexene,n-hexane and 2-methylpentane.The top ten species in terms of mass fraction(with a total mass fraction of 75.3%)were mainly hydrocarbons with a carbon number of 6 or higher and halogenated hydrocarbons with a lower carbon number.The mass concentration of VOC species in the particle phase was significantly lower than that in the gas phase.The change of VOC mass concentrations along the air pollution control devices indicates that conventional pollutant control equipment had a limited effect on VOC reduction.Ozone formation potential calculations showed that aromatic hydrocarbons contributed the highest ozone formation(46.4%)due to their relatively high mass concentrations and MIR(maximum increment reactivity)values.

Performance of water-based foams affected by chemical inhibitors to retard spontaneous combustion of coal

The micelle generating process of the sodium dodecyl sulfate(SDS) solution with the addition of chemical inhibitors was elucidated using phase separation model, and the descending order of the capacity for the selected chemical inhibitors to reduce the critical micelle concentrations of the solution are Mg Cl_2, Ca Cl_2,NH_4HCO_3 and NH_4Cl. The data to quantitatively describe the foam decay process, including foaming ratio,foam life and decay behaviors, was obtained by pressure measuring system. The results indicate that chemical inhibitors can improve the solution foamability. The capacity of the inhibitors to enhance the solution foamability is sorted as NH_4 Cl, NH_4HCO_3, Mg Cl2 and Ca Cl_2 which can distinctly improve the foam stability as well. The capacity of the inhibitors to enhance the SDS foam stability can be arranged as Mg Cl_2, NH_4 Cl, NH_4HCO_3 and Ca Cl_2. It is observed that the gravity drainage plays a leading role in the increase of proportion of diffusion drainage. The oxidation dynamic parameters of the coal samples treated by inhibition foams were investigated using thermal analysis technique, and their synergistic effects on inhibiting coal oxidation were explored.

Numerical Modeling of Pulverized Coal Combustion at Thermal Power Plant Boilers

The paper deals with development and application the numerical model for solution of processes at combustion chamber of the thermal power plant boiler. Mathematical simulation is based on solution of physical and chemical processes occuring at burning pulverized coal in the furnace model. Three-dimensional flows, heat and mass transfer, chemical kinetics of the processes, effects of thermal radiation are considered. Obtained results give quantitative information on velocity distributions, temperature and concentration profiles of the components, the amount of combustion products including harmful substances. The numerical model becomes a tool for investigation and design of combustion chambers with high-efficiency and reliable operation of boiler at thermal power plants.

Development of Sensible Heat Storage Materials Using Sand, Clay and Coal Bottom Ash

In this paper, the mechanical and thermal properties of a sand-clay ceramic with additives coal bottom ash (CBA) waste from incinerator coal power plant are investigated to develop an alternative material for thermal energy storage (TES). Ceramic balls are developed at 1000°C and 1060°C using sintering or firing method. The obtained ceramics were compressed with a compression machine and thermally analyse using Decagon devise KD2 Pro thermal analyser. A muffle furnace was also used for thermal cycling at 610°C. It was found that the CBA increased the porosity, which resulted in the increase of the axial tensile strength reaching 3.5 MPa for sand-clay and ash ceramic. The ceramic balls with the required tensile strength for TES were selected. Their volumetric heat capacity, and thermal conductivity range respectively from 2.4075 MJ·m-3·°C-1 to 3.426 MJ·m-3·°C-1 and their thermal conductivity from 0.331 Wm-1·K-1, to 1.014 Wm-1·K-1 depending on sand origin, size and firing temperature. The selected formulas have good thermal stability because the most fragile specimens after 60 thermal cycles did not present any cracks. These properties allow envisioning the use of the ceramic balls developed as filler material for thermocline thermal energy storage (structured beds) in Concentrating Solar Power plants. And for other applications like solar cooker and solar dryer.

Mercury emissions and partitioning from Indian coal-fired power plants

In India coal combustion is the single largest source of emission of mercury which is a widespread persistent global toxicant,travelling across international borders through air and water.As a party to the Minamata convention,India aims to monitor and reduce Hg emissions and stricter norms are introduced for mercury emissions from power plants(30μg/Nm 3 for flue gas in stack).This paper presents the results obtained during the experimental studies performed on mercury emissions at four coal-fired and one lignite-fired power plants in India.The mercury concentration in the feed coal varied between 0.12-0.27 mg/Kg.In the mercury mass balance,significant proportion of feed coal mercury has been found to be associated with fly ash,whereas bottom ash contained very low mercury.80%-90%of mercury was released to air through stack gas.However,for circulating fluidised bed boiler burning lignite,about 64.8%of feed mercury was found to get captured in the fly ash and only 32.4%was released to air.The mercury emission factor was found to lie in the range of 4.7-15.7 mg/GJ.

A Fuzzy Homogeneous Combustion Control System

This paper presents the scheme of the Fuzzy Homogeneous Combustion Control System (FHCCS) and its practical use on site. The operating results of the system show that FHCCS can not only operate normally, but also guarantee the homogeneous combustion in each level of burner and at optimal air coal ratio of each burner. Some engineering problems about FHCCS implementation are discussed in this paper.

燃烧热测定实验的课程思政设计——农林废弃物的热值测定

燃烧热测定是一个经典的物理化学实验。本案例将燃烧热测定与农林废弃物燃烧发电对接,对实验内容进行了适当调整,让学生了解燃烧热测定对保障发电厂安全运行的重要意义,以及农林废弃物燃烧发电对服务“三农”、乡村振兴和“双碳”战略的重要意义,提高了学生学以致用的能力,激发了学生的学习兴趣,引导学生关心国家能源安全、环境保护、可持续发展和人民的生命健康,对提升学生的能力和素质发挥了良好作用。

煤矿热动力灾害防控研究现状及趋势综述

为分析煤矿热动力灾害防治理论及技术相关研究现状,提高对煤自燃、瓦斯爆炸及诱发耦合灾害等方面的认识,系统总结了当前煤矿热动力灾害研究的成果,分析研究领域国内外进展及不足。研究结果表明:当前热动力灾害基础理论方面需深入多灾种耦合复杂致灾机理及影响机制的研究,防治技术方面需着力发展精细化、低碳化、智能化防治技术及装备,管理方面需以科学理论为基础,制定合理可行的监管监察防灾治灾临界指标。研究结论为煤矿热动力灾害防治理论及技术进一步发展提供参考。

软测量技术赋能燃煤电厂碳排放计量的研究进展

火力发电企业作为我国能源结构的重要组成部分,长期以来是我国碳排放的主要来源,在我国和全球加速推动低碳经济发展的宏观环境下,火电企业积极响应国家“能耗双控”向“碳排放双控”转变的战略部署。在此背景下,精确计量燃煤电厂的碳排放量变得至关重要。在燃煤电厂碳计量中,烟气流量影响燃煤发电中在线监测法的精度,而燃煤消耗量、燃煤元素碳含量以及飞灰碳含量共同决定核算法的可靠性。目前,大多数燃煤发电企业只对流量和燃煤消耗量进行实时监测,在现场恶劣的环境中对燃煤元素碳含量以及飞灰碳含量进行短周期、高频次的直接监测需要花费较大的人力以及物力,流量监测设备也易受烟道环境影响。而软测量技术以其高效和低成本的特点,可为传统碳排放计量过程中关键参数的监测提供一种替代方法。鉴于此,首先阐述了软测量模型的建立过程,包含数据预处理、辅助变量选择、软测量模型建立以及模型校正。数据预处理能够确保数据质量,提高建模效率;辅助变量选择是从大量潜在的变量中筛选出对目标变量的辅助变量,进一步提高建模效率;软测量模型建立主要是基于机理建模和数据驱动建模,是实现目标变量预测的核心;模型校正通过实际的离线或在线数据,对模型进行进一步优化,提高模型的预测精度。其次,针对碳计量相关参数,分析了烟气流量、燃煤消耗量、燃煤元素碳含量和飞灰碳含量监测存在的问题,论述了软测量技术在上述碳计量关键参数的国内外研究进展和应用,评估了机理建模和数据驱动建模技术的有效性、准确性和实用性。其中,机理分析建模主要基于电厂锅炉进出口的能量平衡以及烟风质量守恒等原理,有着确定的数学物理关系式,具有高度可解释性和稳定性,但是建模过程复杂,预测精度较低;数据驱动建模主要是利用各种机器学习方法,基于电厂分布式控制系统(Distributed control system,DCS)丰富的运行数据,对碳计量关键参数进行“黑箱建模”,克服了机理分析建模复杂的过程分析,精度相对较高,但是建模过程不明确,且模型对于不同机组的泛化能力较差。最后,对于软测量技术在碳排放计量领域的发展应用进行了总结与展望。对电厂各参数之间的时序结构、电厂自身计算能力的限制以及机理分析融合数据驱动方法的发展提出相关建议,并对国外二氧化碳预测性排放系统结合软测量技术在国内外燃煤电厂的应用进行展望。

电厂热控仪表故障及预防措施研究

电厂热控仪表用于监测和控制各种热控参数,确保电厂的安全运行和高效发电。然而,由于长期使用和环境影响,热控仪表存在故障风险。为确保热控仪表运行的稳定性,以电磁流量计、压差流量计等热控仪表的常见故障问题为例,分析故障的原因和检修处理措施,并提出具体的故障预防措施。期望该研究为相关从业人员提供参考与借鉴,进而保障电力系统的可靠性和稳定性。

煤电机组耦合储热系统的灵活性调峰特性研究及其性能评价

“双碳目标”背景下,煤电机组将长期作为主力调峰电源,保障电网安全稳定。储热是提升煤电机组灵活性的重要手段,但煤电耦合储热系统的运行特性尚不明确,不同储热技术与煤电机组耦合适应性亟待研究。为此,该文构建600 MW煤电-90 MW显热/潜热/热化学储热3种耦合系统,详细考察系统储/释热过程调峰能力及热力学性能,并基于优劣解距离法(technique for order preference by similarity to an ideal solution,TOPSIS)综合评价,明确最优耦合方案。研究发现,储热过程,Ca(OH)_(2)/CaO热化学储热的调峰容量、调峰深度及?效率均优于热水及熔融盐储热,而释热过程熔融盐储热性能最优;通过TOPSIS综合评价法确定热储热方案均为抽取主蒸汽作为热源,最佳释热方案均为以#2高加进水为冷源,同时确定煤电耦合熔融盐储热为最佳系统耦合方案。相关研究结论可为构建煤电耦合储热调峰系统提供一定的理论和数据支撑。

基于再热蒸汽抽汽-熔盐储热的火电系统分析

提出了一种基于再热蒸汽-抽汽熔盐储热的火电联合系统,通过建立仿真模型对系统的运行过程及效率进行了分析。为了使熔盐放热过程匹配主蒸汽温度,需要在抽汽充热过程之后再配置电加热器对熔盐提温,在此基础上研究了充热过程平均换热温差、放热过程夹点温差、低温储热温度对系统性能参数的影响。结果表明:充热过程中维持10 K平均换热温差,放热夹点温差从5 K增加至15 K会导致最高等效往返效率从88.2%降低至85.0%,同时最佳储热温度从314℃升高至324℃;放热过程中维持10 K夹点温差,充热过程的平均换热温差从5 K增加至15 K时,最高等效往返效率从89.5%降低至85.8%;2个温差均在10 K时,机组的最高等效往返效率为87.1%,该条件下运行时机组最低负荷可从30%下调至24.3%。

大型火电机组风机性能在线智能监控和实时预警系统研究及应用

针对当前大型燃煤机组深度调峰背景下监测预警迟滞易导致风机失速的问题,本文从热力学角度出发,重点评估风机实时运行状态;结合风机热态性能修正实验数据;利用C#语言框架搭建了一套完善的信息采集和在线智能检测实时预警平台;并在某330 MW亚临界机组上完成现场试验验证。平台运行结果表明:改进后的多点矩阵式测量设备可实现宽截面非稳态含尘流场的精准可靠测量,误差低于10%;同时可通过显示实时开度、安全裕量、流量偏差及阻力曲线综合评判当前风机运行性能,实现及时预警,为现场运行人员提供准确的数据指导,具有推广价值。

火电机组碳排放量及碳敏感性通用矩阵模型

为实现火电机组碳排放量的简便准确计量及掌握运行因素对机组碳排放强度的影响,在排放因子法技术上,参考传统q-γ-τ矩阵结构形式,根据求解火电机组碳排放量的需要,并掌握运行参数对发电碳排放强度的影响,建立了火电机组碳排放量及碳敏感性通用矩阵模型,确定了矩阵填写规则。采用热平衡法结合物料衡算法验证了模型的准确性,并与排放因子法核算结果对比;核算了某火电机组24 h的碳排放量,分析了排烟氧量、主蒸汽温度和压力波动时的发电碳排放强度的扰动量ΔM CO_(2)。结果表明:相较于排放因子法,本文所提模型缩短了碳排放量核算的时间跨度,且能提高碳排放量核算的精度;该机组24 h的碳排放量为5780.644 t;当排烟氧量降低0.1%时,ΔM CO_(2)为1.7726 g/(kW·h);当主蒸汽温度升高0.5 K时,ΔM CO_(2)为3.0206 g/(kW·h);当主蒸汽压力增加0.2 MPa时,ΔM CO_(2)为0.3788 g/(kW·h)。

电厂热控系统中热控保护装置故障研究

热控保护装置是电厂热控系统的重要组成部分,在多重因素的影响下,可能出现误动或拒动、软件程序故障等问题,严重影响电厂的安全、稳定运行。基于此,针对热控保护装置的常见故障,分析故障原因并提出具体的处理措施。此外,为确保热控保护装置性能稳定,还提出了定期检测维修、完善故障报警系统等保护措施,以期为相关从业人员提供借鉴与参考。

2011—2022年煤矿热动力灾害事故特征及发生规律分析

基于2011—2022年全国煤矿热动力灾害事故的统计结果,采用数据统计法,按照煤矿企业性质、事故类型、事故等级和发生地区等4个方面进行综合分析,通过趋势图、柱状图及百分比图对煤矿热动力灾害事故的规律和特点进行总结,并对煤矿热动力灾害发生的原因进行深入分析。分析结果表明:近12年我国煤矿热动力灾害事故逐渐减少,以瓦斯爆炸类型为主,多以较大事故和重大事故的形式发生;乡镇煤矿企业和国有煤矿企业伤亡损失严重,情况严峻;西南地区和东北地区为事故多发地区。根据分析结果,从政策、经济、监管、企业及技术层面提出了相应的预防措施。

基于化学团聚技术强化脱除细颗粒物的试验研究

燃煤机组经过超低排放改造后,除尘器对粉尘的脱除效率大大提升。然而,除尘器对PM_(2.5)等细颗粒的捕获能力有限,导致许多细颗粒通过烟囱排入大气,降低了周边空气质量。基于化学团聚技术,在国内某600 MW燃煤电站开展细颗粒物排放控制示范试验研究,旨在通过系统的采样测试探究化学团聚技术对PM_(2.5)排放的控制效果。基于固定污染源采样标准(ISO 23210-2009)开展现场采样测试。对化学团聚技术投运前后细颗粒物排放质量浓度进行检测,依托样品表征方法对颗粒样品进行测试分析,综合评价化学团聚技术对燃煤细颗粒排放的控制作用。结果表明:团聚吸附剂喷射后,静电除尘器(electrostatic precipitator,ESP)入口粉尘的平均粒径由57.3μm增大至69.6μm,平均粒径增大21.5%;团聚后,ESP入口PM_(1),PM_(2.5),PM_(10)质量浓度分别由124.2 mg/m^(3),359.5 mg/m^(3),947.7 mg/m^(3)减小至85.6 mg/m^(3),240.6 mg/m^(3),492.0 mg/m^(3),团聚效率分别为31.1%,33.1%,48.1%。飞灰粒径筛分结果表明:团聚后,粒径在38μm以下的飞灰质量分数由32.7%减小至9.2%,而粒径在38μm~75μm范围内的飞灰质量分数由29.7%增大至62.8%;最终,在团聚吸附剂作用下,湿法烟气脱硫(wet flue gas desul furization,WFGD)出口总粉尘质量浓度由1.32 mg/m^(3)降低至1.09 mg/m^(3)。综上,化学团聚技术对燃煤电站细颗粒物团聚效果显著,PM_(2.5)脱除效率显著提升。