【作者】 兰泽全；

【导师】 曹欣玉； 岑可法； 周俊虎；

【作者基本信息】 浙江大学 ， 工程热物理， 2004， 博士

【摘要】 长期以来，受热面沾污结渣一直是困扰燃煤锅炉而未能得到妥善解决的国际性难题之一，极大地威胁着锅炉的安全、经济运行及设备的可靠性。矿物质是引起灰沉积的根本原因，本文主要通过对矿物元素在炉内的迁移和沉积行为的研究，来揭示沾污结渣机理。Na、Fe、Ca是导致灰沉积的重要矿物元素，因此，在燃料的选择上充分考虑了代表性，以含Na很高的新汶黑液水煤浆等五种在煤质组成和熔融温度方面都极具代表性的煤和煤浆为研究对象，因而本文的研究具有一定的普遍意义。 本文研究的重点之一是黑液水煤浆的燃烧特性和沾污结渣特性，目的是考察其工业应用的可行性及潜在问题。热天平机理实验、试验炉中试试验及工业炉应用试验结果都表明，黑液浆粘度低，具有良好的流动、雾化性能，加上含有大量的木质素和Na基化合物等有机成分，因而容易着火，燃烧稳定、良好，烟气中NOx、SO₂含量及烟尘浓度都远低于常规浆和制浆原煤，因此，黑液水煤浆具有显著的经济效益和环保效益，应用前景广阔。 然而，黑液浆中的Na易带来受热面的沾污结渣。烧结试验结果表明，黑液浆具有很强的烧结特性，初始烧结温度很低，仅700℃左右。在沾污结渣机理方面，通过灰污热流探针、炉内颗粒取样及电子探针等多种创新性手段和方法，对煤和黑液水煤浆的灰沉积机理及动态过程进行了深入的研究。如采用带有能谱仪的扫描电镜，分析比较了炉内空间中心颗粒、近壁颗粒、炉壁渣中颗粒及尾部烟道飞灰颗粒的形貌和元素含量，研究了灰粒中矿物质的迁徙和沉积特性。结果表明，沾污结渣与燃料自身特性有直接关系，Na是造成黑液水煤浆积灰结渣严重的根本原因，Na无论是在初始层还是整个灰渣中的含量都很高，从而引起灰渣层中Si和Al具有几乎完全相同的分布规律，绝大部分Si、Al与Na结合在一起生成了低熔点的霞石等铝硅酸钠盐，黑液浆初始层中Fe的富集不明显。Si、Al、Fe、Ca是造成煤灰结渣的主要矿物元素，在灰沉积物中Fe的富集明显，Fe、Ca对结渣可能起着协同机理作用。研究结果还表明，积灰和结渣在机理上存在很大的不同，积灰沉积物中基本上没有出现Fe的富集，其含量远低于结渣沉积物，而Na、Ca含量则比结渣沉积物中高，表明高温环境有利于Fe的沉积，而较低的受热面温度则对烟气中挥发性碱金属和碱土金属蒸气的凝结有利。 最后，对现有的结渣评判模型进行了改进，提出了将综合指数R纳入评判因素集以此来预测和判别燃煤结渣倾向的五因素模型，以及适用于切圆燃烧锅炉结渣特性评判的七因素模型。通过可靠性校验，表明此新模型具有更高的准确性，并在VB环境下开发了程序化实现沾污结渣评判的用户界面。更多还原

【Abstract】 For a long time, fouling and slagging is one of the international problems which puzzles boiler whereas not found adequate solution. It endangers boiler’s security, economical operation and equipment reliability. Mineral substance in coal is the primary cause giving rise to ash deposition. In order to reveal mechanism of fouling and slagging, mineral elements’ migration and deposition behaviour at furnace are investigated in this paper. Sodium, ferrumiron, calcium are the important mineral elements causing ash deposition, accordingly, deliberate consideration is made in selecting trial fuels, Xinwen black liquor coal water slurry which contains plenty of sodium and other four fuels are chosen investigation objects. These fuels have good representativeness both in coal quality composition and ash fusing temperature. Consequently, the investigation in this paper is possessed of some general sense.One of the investigation emphases is black liquor coal water slurry’ s combustion characteristics and fouling/slagging performance, aim at surveying its industrial application feasibility and potential problems. The results of thermobalance mechanism experiment, trial furnace pilot plant and industrial furnace application test show, black liquor slurry’s viscosity is low, with favorable performance of flow and sprayability. It contains some organic constituents such as lignin, sodium-group compound. As a result, black liquor slurry is easy to fire. It have good quality of flameholding, but also its nitrogen oxide, sulfur dioxide, and flue dust contents are far lower than the coal- water slurry and raw coal. Accordingly, black liquor coal water slurry is possessed of notable economic benefits, environmental benefits and amplitude potential application.Yet, the sodium included in black liquor slurry is amiable to bring about fouling and slagging in heat transfer surface. The sintering test result show black liquor slurry is in possession of very predominant sintering performance, its initial sintering temperature is very low, only about 1073K. In the aspects of foul ing and slagging mechanism, a few innovative instruments and methods are employed to investigate the ash deposition mechanism and dynamic processes in detail, such as heat flux probe, particle sampling along the flue travel and electron probe microanalyzer, et al. For example, scanning electron microscope with energy spectrometer is adopted to analyze and compare the feature and mineral element content of the center grains, near wall grains, grains in wall slags and fly ash grains in chimney. The migration and deposition performance of the mineral substance contained in ash particle are looked into. The results indicate that fouling and slagging have direct relation with fuel self- performance. Sodium is the primary cause of the severefouling and slagging condition in the black I iquor coal water slurry-fired boiler. Its contents both the inial layer and who I ly slags are very high, as a result gave rise to silicium distribution in good agreement with aluminium in ash layer, by reacting with sodium most silicium and aluminium form aluminosiIicate, such as nepheline, whose fusing temperature is very low. The ferr urn iron enrichment is not apparent in the deposit initial layer of black liquor slurry. Silicium, aluminium, ferrumiron, calcium is the essential mineral elements causing coal ash deposition. Ferrumiron enrichment phenomenon is very evident in ash deposits. Ferrumiron and calcium plays synergism roles during the formation of slagging likelihood. The findings also show, the fouling mechanism is much different from slagging. The ferrumiron enrichment doesn’t appear in the fouling deposits, thereof contents far less than in slagging deposits, whereas sodium and calcium contents higher than in slag deposits, which shows high temperature environment is in favor of ferrumiron deposition, however lower heating surface temperature is favorable to the coagulation of volati le alka I i and alka I ine earth metal vapor.In conclusion, the present slagging judgement mod更多还原