电站锅炉用煤常规结渣指标的模糊综合评判

运用常规结渣指标在判别电站锅炉用煤结渣特性时存在着较强的主观性,导致判别结果分歧较大.为此,提出了常规结渣指标的模糊综合评判方法,并将之用于8个煤种的结渣特性判别,所得评判结果与实际结渣状况相符.文中还强调了隶属函数的建立及权重集的选择对模糊综合评判的影响.     

气氛条件对典型煤种结渣特性影响的实验研究

燃煤锅炉受热面结渣问题一直是困扰电站锅炉安全和经济运行的重要因素.因b选取三种不同的煤种在不同气氛条件下进行灰熔融性试验的基础上对煤种的结渣特性作出分析.分析结论为还原性环境气氛可显著降低煤灰熔融温度,从而使煤灰结渣特性增强;单一评判法与多指标综合评判法对煤灰结渣特性进行判定,为避免锅炉受热面结渣提供理论依据.在锅炉实际运行中,因保证炉内受热面周边氧化性气氛,降低煤灰结渣特性,减少锅炉受热面结渣的可能性.     

锅炉结渣原因分析及预防措施

锅炉结渣是个复杂的物理化学过程,至今还没有能定量描述结渣过程的数学模型.锅炉结渣是困扰着电力行业的一个主要问题.主要从燃料燃烧及燃烧动力学方面论述了锅炉结渣的原因,并介绍了目前国内外判断锅炉结渣的几种方法.最后,针对灰渣形成的过程和锅炉结渣的原因从燃料选择、入炉燃料加工、锅炉负荷工况调整及检修维护方面提出了对避免锅炉结渣应采取的措施,以指导锅炉设计及锅炉运行.     

基于OEW的混煤结渣特性的评判探讨

首先对煤的2个结渣特性单一评判指标进行了变换,获得新的评判指标,接着利用客观熵权算法对所选取的煤的结渣样本进行了归类处理,依据所提出的评判界限,删除了不符合规则的样本,获得了煤的结渣样本以及类心向量。将本方法应用于某集团公司热电厂锅炉混煤结渣特性的预测评判中,结果表明该方法能够准确的对该混煤的结渣特性做出评判,由此证明了本方法是合理可行的。     

防结渣技术在360t/h锅炉上的应用

介绍锅炉结渣的机理以及控制炉内结渣过程的主要因素,用数值模拟方法对某电厂360t/h锅炉结渣问题进行分析,并提出了改造该锅炉切实可行的措施.通过对该锅炉第二次改造后运行实践的检验,得出了与防结渣技术相关的一些结论.     

基于退火支持向量的燃煤锅炉结渣特性预测

应用支持向量机算法对燃煤锅炉结渣问题进行数学建模,并利用模拟退火算法对支持向量机模型参数进行了优化,最终获得最优参数组合。模型将煤的软化温度tSt、硅铝比w(SiO2)/w(A12O3)、碱酸比J和硅比G以及锅炉的无因次切圆直径t和无因次实际切圆直径d作为输入变量,以结渣程度作为输出,用试验数据对模型进行了校验和参数的寻优,利用优化后的模型对15台锅炉结渣特性进行预测评判,有14个正确,评判准确率为93.33%,由此表明此方法是合理有效的。同时为了配合该模型,采用高级语言编程开发出了相应的预测评判系统。     

基于模糊C均值聚类和支持向量机算法的燃煤锅炉结渣特性预测

应用基于模糊C均值聚类算法预处理的支持向量机算法对锅炉结渣特性进行预测建模,将煤的软化温度、碱酸比、硅铝比和硅比以及无因次炉膛烟气平均温度和无因次实际切圆直径作为模型的输入变量,结渣程度作为输出变量,利用优化后的模型对10台锅炉的结渣特性进行评判.结果表明:该模型能够减小训练样本的过拟合度,具有较强的泛化能力;本试验中FCM-SVM预测模型预测结果的正确率为100%,可以实现对锅炉结渣特性的精确预测.     

燃煤锅炉炉膛结渣原因及预防措施的探讨

针对燃煤锅炉炉膛结渣的问题,阐述了锅炉运行中炉膛结渣的过程和机理,通过分析炉膛结渣的影响因素及提出减少炉膛结渣的措施,提高了锅炉运行的经济性和可靠性.     

软计算方法在煤灰结渣特性评判中的应用

基于软计算理论,提出了一种煤灰结渣特性的神经-模糊评判模型。此模型来源于实际观测数据,可靠性高,能够更有效的判别锅炉炉膛结渣特性。     

锅炉干排渣系统运行调整

自大港电厂一期机组试运投产以来,锅炉炉底干排渣系统多次出现严重积渣、堵渣现象。直接造成锅炉超温、效率降低、甚至限负荷运行,给锅炉的安全、稳定运行造成了相当大的影响。文中通过对锅炉运行稳定性、锅炉结焦防范、大渣冷却等运行技术进行研究,分析并得到了干排渣系统结渣、堵渣的原因以及渣量对负荷变化的影响。针对本厂机组,采取了一系列控制措施应对大渣量对锅炉机组造成的影响,以及结渣、堵渣后的处理方法。实践表明,干排渣系统运行良好,有效的保证了锅炉机组的运行。     

煤的结渣特性磁力分析的研究

从煤的物理特性研究煤灰结渣特性,煤中所含各类物质中,铁化合物具有最低的熔化温度,易在炉膛内燃烧中产生结焦。本文提出了一种根据磁铁对煤的磁力吸附百分比来判别不同煤种煤的结渣倾向的新方法,并对这种方法的机理和应用进行了深入分析。这种方法实现了煤的结渣特性的现场快速测量。     

Design of solid biofuels blends to minimize the risk of sintering in biomass boilers

Biomass with high concentration of alkali/alkaline and silica components can lead to slagging/fouling, and sintering of the ash deposits, causing corrosion and erosion of the boilers. There are several methods to predict bed agglomeration such as slagging/fouling indexes. However, these indexes are developed to be used for coal ashes, which shows a different behaviour than biomass fuels. The aim of this work was to determine the suitable percentage of different species found in biomass blends in order to reduce the risk of slagging and sintering. We studied the ash behaviour of 24 blended biomass samples using two slagging indexes: the alkali index, and the % of bases in ashes index, and we validated these two indexes with the Bioslag test, and with the Hardness Index (%D₁). There is low risk of slagging in most of the samples, as well as a low sintering risk. However, some samples present moderate risk of sintering possibly due to SiO₂. The Bioslag test and the %D₁ test support our results. Samples showing risk of sintering exceed 25% of the total accumulated ash weight percentage ac%_1P>25%, and show a hardness of %D₁ > 0.7. These validations can be considered as useful tools for estimating slagging and sintering of woody biomass fuels in domestic pellet boilers.     

Innovative experimental study for slagging diagnosis based on vibration signal of the superheater tube panels in coal-fired boilers

Slagging on the exchanger surfaces in boiler in power plants is still a serious issue that reduces thermodynamic efficiency and threatens the operation of the generation unit. In this paper, an innovative slagging diagnosis method based on the analysis of vibration signal of the exchanger tube panels is proposed to monitor the slagging condition. We build a scaled-down tube panel according to the actual structure of the superheater panel in laboratory to study the relationship between vibration signal and varied slagging conditions and air speed. Root Mean Square (RMS) in time domain and wavelet packet decomposition in frequency domain are employed to extract the features from vibration signals and predict the slagging condition without shut-down in the future. It is found that RMS value of the tube panel signals decreases with the increase of slagging weight, especially at a low air speed. Relative signal energy in a certain frequency band will experience significant change after tube panel slagged. In order to verify the experimental result on the feature changes of the tube panel vibration signals with varied slagging conditions, we successfully demonstrate our laboratory result via analysis of vibration signals of a superheater tube panel in Banshan Power Generation (Hangzhou). It indicates that the vibration signals of tube segment between the header and furnace wall of the superheater panel can be collected and used for slagging diagnosis in a running pulverized coal boiler. Our study is promising for prediction of slagging and furtherly reduce the risk induced by slagging of exchanger panel in the boiler.     

一种评判煤灰结渣特性的新方法

针对煤灰结渣特性单一评判指标的预测精度普遍偏低的问题,基于偏最小二乘算法（PLS）和交叉验证理论建立了煤灰结渣特性预测模型,该模型有4个输入变量,即煤灰的软化温度、碱酸比、硅比和硅铝比,1个输出变量,即结渣程度．提出了指标的同向性和异向性的概念,依据所提出的概念对各单一指标对煤灰结渣特性的作用进行了定性分析与讨论,结合拟合方程,给出了煤灰结渣特性的评判依据．通过对测试样本进行检验,结果表明：所提出的PLS预测模型的预测精度远高于单一评判指标的预测精度,所建模型是合理可行的．     

3种型号W火焰锅炉结渣特性的数值模拟

采用结渣模型耦合气固两相流动燃烧模型,对3种不同型号W火焰锅炉的结渣特性进行了多工况数值模拟,结合实际运行状况,对结渣位置、程度及原因进行了对比分析.结果表明:在燃用结渣倾向相同的煤时,不同型号锅炉的结渣特性有明显差异,这是由于炉膛结构尺寸、下炉膛热力参数、燃烧器类型、分级二次风配风方式等不同造成的;切停侧边燃烧器、降低锅炉负荷和燃用结渣倾向低的煤都能有效减轻侧墙结渣,显著改善锅炉结渣特性.为此,提出了防止W火焰锅炉结渣的措施.     

双区燃烧技术应用于降低NO_x的数值模拟研究

双区燃烧是降低Nox排放,防止炉内结渣的一项新技术.利用CFD软件平台,采用数值模拟方法对其某电厂200 mm四角切圆锅炉改造前后炉内燃烧过程进行研究.计算结果表明:采用双区燃烧技术使炉膛中形成了温度,组分和颗粒相参数显著不同的中心区和近壁区.由于附壁射流的作用,使得高温区集中在炉膛中部,有效的防止了锅炉结渣;改造后炉内有比常规燃烧方式锅炉更大的还原气氛区域,抑制了Nox的产生,使其排放降低34.6 %.     

Assessing slagging propensity of coal from their slagging indices

Energy production by coal combustion is the most commonly used energy technology. At this time, the correlation between the existing coal slagging indices and the actual observations made in most conventional boilers is poor. Some of the conventional test results and empirical ratios frequently offer misleading information, especially, when their use is extended to other coals or blends. For better understanding of the coal properties related to slagging problems, here a multi-variable regression (MR) analysis equation to predict slagging propensity and new models based on multi-resolution wavelet neural network (MWNN) and vague sets are proposed. Coal samples collected from a wide range of Chinese power plants are evaluated. The results of predictions correlate well with the reported field performance of the coals and the new models offer better predictive capability for understanding the field slagging observations than the conventional indices. The methods proposed here provide an encouraging development towards the search for a generic technique of assessing the slagging potential of pulverized coals/blends in boilers.     

600MW超临界煤粉炉燃烧过程数值模拟

四角切圆煤粉锅炉是我国较为普遍适用的燃煤锅炉的炉型之一,炉膛结渣是影响锅炉圆燃煤锅炉膛内的湍流流动,传热和燃烧过程进行了三维数值模拟,得出炉膛内温度场和速度场分布。通过灰污层外表面平均温度与煤灰的变形温度DT进行比较,能够较为准确地判断结渣区域,为安全运行提供有效依据。     

锅炉受热面的结灰机理和吹灰器的设置

主要对炉膛结渣的成因进行了分析,并提出了对煤结焦和沾污特性的判别方法;同时,对炉膛结焦及积灰的危害性和对电厂运行的经济性的影响进行了分析。     

采用旋流煤粉燃烧方式的1 025 t/h锅炉结渣原因的工业试验

针对采用旋流煤粉燃烧方式燃用贫煤的1025 t/h锅炉结渣问题,进行了冷、热态工业试验．结果表明,采用双调风旋流燃烧器的锅炉中、下层燃烧器区域结渣；高负荷结渣严重,低负荷结渣情况有所减缓,但掉渣更加频繁；锅炉前墙燃烧器区温度高于后墙．双调风旋流燃烧器和中心给粉燃烧器都具有大且稳定的回流区,并有较大的扩展角；下层燃烧器采用中心给粉旋流煤粉燃烧器可有效避免结渣．