纯烧准东煤循环流化床锅炉设计与运行研究

准东煤中碱金属和碱土金属含量高,在燃烧过程中极易引起受热面结渣沾污,影响锅炉的安全稳定运行。根据准东煤的煤质特点,分析准东煤燃烧过程中的结渣沾污机理,提出纯烧准东煤循环流化床锅炉设计方案,通过调整受热面的布置方式,使对流受热面避开碱金属蒸气的易结渣沾污温度区间,并开展工程验证。结果显示：不同负荷下锅炉能够稳定运行,且效率均超过93%。在锅炉纯烧准东煤6个月后,受热面表面仅有松散浮灰,表明锅炉可长期纯烧准东煤且不会产生结渣沾污现象。     

准东煤掺烧煤矸石安全性与经济性分析

高岭土与低钠煤可以有效抑制燃用准东煤时炉内的沾污结渣问题,但由于其价格升高,为降低电厂燃煤成本,因此提出将煤灰成分相似的煤矸石作为准东煤防结渣添加剂。分析煤矸石作为添加剂抑制炉内沾污结渣的可行性,根据入炉煤灰中折算Na₂O含量低于3.0%,确定掺烧比例,并在某150 MW机组上进行实炉掺烧试验。通过掺烧试验分析可见,煤矸石掺烧比例不宜过大,否则煤粉细度变粗,入炉煤热量降低,影响锅炉带负荷能力;掺烧煤矸石锅炉能够安全稳定运行,并可有效抑制炉内结渣,同时还可节约标煤,为电厂带来一定经济效益。     

300MW循环流化床锅炉准东高碱煤掺烧高岭土运行特性研究

准东高碱煤具有灰分低、挥发分高、燃烧反应性好、结渣沾污性强等特点。向准东高碱煤中掺烧一定比例的高岭土,可起到减轻沾污的作用。为研究循环流化床(CFB)锅炉准东高碱煤掺烧高岭土实炉运行特性,在1台300 MW CFB锅炉上开展了高岭土实炉掺烧试验,获得了不同高岭土掺烧比例下锅炉主要运行参数、环保参数及飞灰特性。结果表明:当高岭土掺烧比例达到30%时,CFB锅炉燃用准东煤整体上能够稳定运行;当高岭土掺烧比例不超过25%时,锅炉效率变化较小;实际运行中掺烧高岭土可有效抑制尾部烟道的结渣沾污现象,当高岭土掺烧比例达到15%后,飞灰特性已经趋于稳定。     

350MW机组锅炉准东煤掺烧试验研究

准东煤具有极易着火、极易燃尽的特性,燃烧性能优异,但具有严重的结渣、沾污特性。对某电厂350 MW机组锅炉进行了不同负荷段掺烧准东煤的试验,对不同负荷时燃用不同比例准东煤时锅炉炉膛及过热器、再热器管壁结渣及沾污情况进行了对比分析。通过试验掌握了锅炉在不同负荷段对掺烧不同比例准东煤的适应能力,为准东煤在电站锅炉的应用提供参考。     

燃用高钠煤350MW超临界锅炉概述

新疆准东地区某些煤种碱金属含量高,已引发锅炉严重沾污、结渣问题,影响锅炉安全运行。特变电工350 MW超临界锅炉为国内首台针对高钠煤所设计的锅炉。该锅炉通过合理的炉膛选型、燃烧器布置、吹灰器布置及受热面布置等措施,有效的缓解了锅炉炉内的结渣、沾污问题。锅炉在满负荷运行工况下,准东煤掺烧比例达到95%以上,为国内燃用准东煤同类型锅炉掺烧比例的最大值。     

准东煤混烧过程中结渣沾污特性研究

针对准东煤在实际电厂燃烧过程中的强结渣、强沾污问题,选取了典型的高Ca、高Na南矿煤为研究对象。在0.4 MW燃烧试验台上进行了准东煤结渣特性试验研究,并通过添加不同比例的将军庙煤来研究混烧对煤灰结渣、沾污特性的影响。研究结果表明:纯烧南矿煤时结渣较为严重,灰渣呈现灰褐色,且质地较为疏松,其不同区域的灰渣主要以Ca的低温化合物为主;沾污样呈现亮白色,主要以硫酸钠为主。添加将军庙煤后,煤灰中的Al、Si与Ca、Na发生强烈的交互反应,生成高熔点的硅铝酸盐类物质,结渣和沾污倾向大为减缓。最终结果表明:实际电厂再燃用南矿煤时,可部分掺烧(10%～20%)将军庙煤,能够明显减缓煤灰的结渣沾污强度。     

660 MW超临界直流锅炉大比例燃用准东煤燃烧调整试验分析

准东煤因其灰分低、易着火、燃尽性好等优点通常被作为优良的动力用煤,但因其煤灰中碱金属含量较高,容易出现受热面沾污、腐蚀、结渣等危害锅炉运行安全的问题.在大比例燃用准东煤的过程中,为了增大锅炉热效率、减小热偏差、降低污染物排放量、防止受热面结渣和提高锅炉燃烧经济性,首先通过摸底试验测定了某660 MW锅炉目前的运行情况及...     

五彩湾煤燃烧特性的试验研究

对五彩湾煤与乌东煤2种煤种及3种不同掺烧比例的混煤分别进行了物理化学特性分析、煤粉气流着火温度测试、一维火焰炉中燃烧与结渣试验以及200kW沾污试验台的沾污性能试验,并对各种混煤的着火、燃尽和结渣性能进行了评定.利用专家系统对试验煤样的主要特性进行了最终评价,并结合2种沾污性能判别指标对煤灰的沾污性能进行了验证,给出推荐的设计煤种和校核煤种.结果表明:混煤具有严重结渣倾向;五彩湾煤具有严重的沾污倾向,而乌东煤为低沾污倾向煤种,通过掺烧乌东煤可以减轻五彩湾煤的沾污;推荐选用五彩湾煤与乌东煤的掺烧比例为7∶3和5∶5的混煤1和混煤3分别作为设计煤种和校核煤种.     

添加剂对准东煤结渣和沾污特性影响的研究

在0.4 MW准东煤燃烧与沾污试验台上进行了3种不同添加剂对某准东煤燃烧时结渣、沾污特性影响的研究。结果表明:炉膛内和蛇形管前屏只存在结渣现象,结渣物是以Fe、Ca为主形成的低熔点复合盐类,而Na对结渣贡献并不占主要地位;各工况的准东煤真实灰熔点在1 100℃左右;烟温在800℃左右时受热面以沾污为主,Na_2SO_4和CaSO_4的冷凝沉积占主导;准东煤自身燃烧产生的底渣作为添加剂时缓解结渣、沾污效果不明显;添加高岭土时结渣物虽较厚但较为疏松,易于清除,说明其具有明显的减弱结渣强度的作用;以将军庙煤为添加剂时能明显减弱沾污强度。     

高岭土对新疆高碱煤沾污结渣特性的影响研究

为深入研究高岭土对减缓新疆准东高碱煤沾污结渣特性的影响规律与作用机制,利用3 MW_(th)多功能煤燃烧中试平台模拟实际电站锅炉四角切圆燃烧环境下研究高岭土对新疆准东高碱煤燃烧过程中灰的生成及沾污结渣特性的影响。试验结果表明:高岭土成分以SiO_2为主,虽然SiO_2单质熔点高达到1 730℃,但煤灰中SiO_2主要以非晶体状态存在,有时可提高熔融温度,有时则起到助熔作用;添加10%高岭土后,其炉膛结焦比纯烧准东高碱煤要好一些,虽然仍有流渣,但其渣的致密程度要比纯烧准东高碱煤要低;在炉膛燃烧区域准东高碱煤的碱酸比(B/A值)高于添加高岭土对应灰样的碱酸比值,而在高温对流受热面烟温区域(末级过热器、末级再热器区域),添加高岭土后其灰样的碱酸比值比燃准东高碱煤工况下灰样的碱酸比要低,添加高岭土后,与纯烧准东高碱煤相比,高碱酸比分布温度区间沿烟气流向方向向后推移,即易发生严重沾污的烟温区间向低温区域偏移。因此,相同条件下其在对流受热面上的沾污烧结程度要低,添加高岭土对降低锅炉对流受热面发生大面积沾污具有一定的效果。     

Investigation on ash deposition characteristics during Zhundong coal combustion

The reserves of Zhundong (ZD) coal in China are huge. However, the high content of Na and Ca induces serious slagging and fouling problems. In this study, the ZD coal was burned in a DTF (drop tube furnace), and the ashes collected at different gas temperature with non-cooling probe were analyzed to obtain the ash particle properties and their combination mode. The results showed that Na, Ca and Fe are the main elements leading to slagging when the gas temperature is about 1000 °C during ZD coal combustion, but their mechanisms are quite different. Some sodium silicates and aluminosilicates and calcium sulfate keep molten state in the ashes collected at 1000 °C. These molten ash particles may impact and adhere on the bare tube surface, and then solidified quickly. With the growth of slag thickness, the depositing surface temperature is increased. The molten ash particles might form a layer of molten film, which could capture the other high fusion temperature particles. The Fe₂O₃ sphere were captured by the formed molten slag and then they blended together to form a new molten slag with lower melting temperature.     

Combustion performance and slagging characteristics during co-combustion of Zhundong coal and sludge

Zhundong coal (ZDc) with a very large reserve is faced with severe problems of slagging and fouling during combustion in boilers because of the high-Na content. Sludge, the by-product of urban sewage treatment, is also faced with the problem in utilization. In this study, the co-combustion of ZDc and sludge was investigated in a laboratory-scale experimental apparatus before further studies in larger-scale setups. The experimental results confirm an interaction between ZDc and sludge during co-combustion, which was mainly caused by the Na catalytic action and improved the combustion performance of the co-fuels. The catalytic effect was particularly significant at low sludge mixing ratios. The reactions between Na-based compounds in ZDc and Si/Al/P-rich minerals in sludge, forming high-melting-point phosphates and aluminosilicates, not only increased Na retention in residual ash reducing the risk of fouling on tail-heating surfaces in boilers, but also raised the ash fusibility of the co-fuels avoiding low-temperature sintering. Even so, to prevent slagging, the high combustion temperature above 900 °C should be avoided during co-combustion because of the high Na retention in residual ash. Moreover, the high heavy metal retention in residual ash decreased the pollution caused by heavy metal volatilization during sludge combustion.     

燃煤电站锅炉受热面灰污监测研究

锅炉受热面积灰和结渣会导致锅炉运行的安全性和经济性下降。定义了新的受热面清洁因子,考虑了锅炉各受热面清洁时与灰污平衡时工质进出口焓升的变化,该清洁因子能够更显著地反映出受热面的灰污程度。应用BP神经网络预测不同工况下锅炉各受热面的工质焓升极大值与极小值,实时计算出锅炉各受热面的灰污状况,可指导和优化锅炉吹灰操作,并以屏式过热器为例进行了验证。     

燃高灰分劣质无烟煤角管式链条炉排锅炉技术改造

从工程实践的角度出发,针对高灰分劣质无烟煤的特点,对一台角管式链条炉排锅炉在燃用非设计煤种时,所产生的锅炉出力降低、受热面积灰严重的状况进行了研究和分析.通过对锅炉炉拱和炉内烟气流道的改造,以及二次风的运用,提高锅炉在燃用高灰分劣质无烟煤时的出力和运行效率,改善了炉内的严重积灰现象.改造突出了锅炉前、后拱在链条炉燃烧组织中极其重要的作用,可为其它在燃用非设计煤种时出力降低的锅炉技术改造提供借鉴.     

NOx and H2S formation in the reductive zone of air-staged combustion of pulverized blended coals

Low NO_x combustion of blended coals is widely used in coal-fired boilers in China to control NO_x emission; thus, it is necessary to understand the formation mechanism of NO_x and H₂S during the combustion of blended coals. This paper focused on the investigation of reductive gases in the formation of NO_x and H₂S in the reductive zone of blended coals during combustion. Experiments with Zhundong (ZD) and Commercial (GE) coal and their blends with different mixing ratios were conducted in a drop tube furnace at 1200°C–1400°C with an excessive air ratio of 0.6–1.2. The coal conversion and formation characteristics of CO, H₂S, and NO_x in the fuel-rich zone were carefully studied under different experimental conditions for different blend ratios. Blending ZD into GE was found to increase not only the coal conversion but also the concentrations of CO and H₂S as NO reduction accelerated. Both the CO and H₂S concentrations inblended coal combustion increase with an increase in the combustion temperature and a decrease in the excessive air ratio. Based on accumulated experimental data, one interesting finding was that NO and H₂S from blended coal combustion were almost directly dependent on the CO concentration, and the CO concentration of the blended coal combustion depended on the single char gasification conversion.Thus, CO, NO_x, and H₂S formation characteristics from blended coal combustion can be well predicted by single char gasification kinetics.     

Development and application of anti-fouling ceramic coating for high-sodium coal-fired boilers

To address the fouling problem in boilers fired with high-sodium coal (HSC), a composite ceramic coating was developed using the slurry method and applied on 15CrMo steel. After sintering, the composite ceramic coating had a dense structure and was well bonded to the substrate forming a metallurgical damascene structure. The fouling and thermal shock resistance of the ceramic coating to sodium sulfate was found be excellent. After five fouling cycles, the uncoated steel had a surface fouling rate of 21.9%, compared to 0% for the coated steel. The composite ceramic coating also demonstrated an appreciable fouling resistance to sodium sulfate. Similar to the flaky oxide film formed on the uncoated steel surface, only a few fine sodium sulfate particles penetrated the microcracks generated during the sintering of the ceramic coating. However, remarkable anti-fouling results were achieved when the composite ceramic coating was applied in an industrial boiler fired with a Zhundong HSC blend.     

超超临界燃准东煤机组吹灰系统优化研究

吹灰是清除受热面积灰结渣的一种有效手段。目前电厂吹灰的频率和时机通常是依靠经验判断,效率低且经济成本高。为改善吹灰方式,以新疆准东地区某台660 MW超超临界燃煤电站锅炉为研究对象,基于电厂分布式控制系统(DCS)中的运行数据、受热面管束排布方式及入炉煤的煤质特性,运用热平衡法求出受热面上的灰污系数,并构建在线监测模型,利用该模型优化原有的吹灰系统。结果表明：优化后1天内吹灰频率减少4次,可为电厂节省约76.26 t煤,说明此优化模型经济效益十分明显。