共查询到18条相似文献,搜索用时 531 毫秒
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生物质发电是利用生物质所具有的生物质能进行发电,是可再生能源发电的一种,是优化我国能源消费结构的最好途径之一。将农作物秸秆、薪柴、禽畜粪便、工业有机废弃物和城市固体有机垃圾等废弃物作为生物质燃料,充分利用循环流化床锅炉燃烧特性,克服生物质燃料挥发分偏低、热值波动大、水分高的特质。简述了循环流化床锅炉燃烧技术方案在生物质燃料发电项目上的应用,整理对比出优于常规生物质锅炉的技术特点,为同类型生物质发电锅炉选型提供参考。 相似文献
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基于流化床的生物质燃烧技术应用日益广泛.生物质燃料流化床的缺点是容易产生床体结焦.灰的组分和生物质燃料中的硫、氯是影响流化床锅炉烧结倾向、锅炉污染速率、灰沉积过程、结焦和过热器腐蚀的主要因素.以灰成分为基础划分生物质燃料,可分为具有显著的不同燃烧特性的3类.在实践的基础上,阐述了各类生物质燃料及其灰分特性,以及在流化床... 相似文献
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《Progress in Energy and Combustion Science》2005,31(2):171-192
This paper describes the potential applications of renewable energy sources to replace fossil fuel combustion as the prime energy sources in various countries, and discusses problems associated with biomass combustion in boiler power systems. Here, the term biomass includes organic matter produced as a result of photosynthesis as well as municipal, industrial and animal waste material. Brief summaries of the basic concepts involved in the combustion of biomass fuels are presented. Renewable energy sources (RES) supply 14% of the total world energy demand. RES are biomass, hydropower, geothermal, solar, wind and marine energies. The renewables are the primary, domestic and clean or inexhaustible energy resources. The percentage share of biomass was 62.1% of total renewable energy sources in 1995. Experimental results for a large variety of biomass fuels and conditions are presented. Numerical studies are also discussed. Biomass is an attractive renewable fuel in utility boilers. The compositions of biomass among fuel types are variable. Ash composition for the biomass is fundamentally different from ash composition for the coal. Especially inorganic constituents cause to critical problems of toxic emissions, fouling and slagging. Metals in ash, in combination with other fuel elements such as silica and sulfur, and facilitated by the presence of chlorine, are responsible for many undesirable reactions in combustion furnaces and power boilers. Elements including K, Na, S, Cl, P, Ca, Mg, Fe, Si are involved in reactions leading to ash fouling and slagging in biomass combustors. Chlorine in the biomass may affect operation by corrosion. Ash deposits reduce heat transfer and may also result in severe corrosion at high temperatures. Other influences of biomass composition are observed for the rates of combustion and pollutant emissions. Biomass combustion systems are non-polluting and offer significant protection of the environment. The reduction of greenhouse gases pollution is the main advantage of utilizing biomass energy. 相似文献
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Biomass is available from many sources or can be mass-produced. Moreover, biomass has a high energy-generation potential, produces less toxic emissions than some other fuels, is mostly carbon neutrality, and burns easily. Biomass has been widely utilized as a raw material in thermal chemical conversion, replacing coal and oil, including power generation. Biomass firing and co-firing in pulverized coal boilers, fluidized bed boilers, and grate furnaces or stokerfed boilers have been developed around the world because of the worsening environmental problems and developing energy crisis. However, many issues hinder the efficient and clean utilization of biomass in energy applications. They include preparation, firing and co-firing, and ash-related issues during and after combustion. In particular, ash-related issues, including alkali-induced slagging, silicate melt-induced slagging (ash fusion), agglomeration, corrosion, and ash utilization, are among the most challenging problems. The current review provides a summary of knowledge and research developments concerning these ash-related issues. It also gives an in-depth analysis and discussion on the formation mechanisms, urgent requirements, and potential countermeasures including the use of additives, co-firing, leaching, and alloying.Alkali species, particularly alkali chlorides and sulfates, cause alkali-induced slagging during biomass combustion. Thus, the mechanisms of generation, transformation, and sequestration of alkali species and the formation and growth of alkali-induced slagging, formed as an alternating overlapping multi-layered structure, are discussed in detail. For silicate melt-induced slagging (ash fusion), the evolutions of chemical composition of both the elements and minerals in the ash during combustion and existing problems in testing are overviewed. Pseudo-4D phase diagrams of (Ma2O)-MaeO-P2O5-Al2O3 and (Ma2O)-MaeO-SiO2-Al2O3 are proposed as effective tools to predict ash fusion characteristics and the properties of melt-induced slagging. Concerning agglomeration that typically occurs in fluidized bed furnaces, melt-induced and coating-induced agglomeration and coating-forming mechanisms are highlighted. Concerning corrosion, seven corrosion mechanisms associated with Cl2, gaseous, solid/deposited, and molten alkali chlorides, molten alkali sulfates and carbonates, and the sulfation/silication of alkali chlorides are comprehensively reviewed. The effects of alloying, salt state (solid, molten, or gaseous), combustion atmosphere, and temperature are also discussed systematically. For ash utilization, potential approaches to the use of fly ash, bottom ash, and biomass/coal co-fired ash as construction and agricultural materials are explored.Several criteria or evaluation indexes are introduced for alkali-induced slagging and agglomeration, and chemical equilibrium calculation and multicomponent phase diagrams of silicate melt-induced slagging and agglomeration. Meanwhile, remedies, including the use of additives, co-firing, leaching, alloying, and the establishment of regulations, are discussed.It is suggested that considerable attention should be focused on an understanding of the kinetics of alkali chemistry, which is essential for the transformation and sequestration of alkali species. A combination of heterogeneous chemical kinetics and multiphase equilibrium modeling is critical to estimating the speciation, saturation levels, and the presence of melt of the ash-forming matter. Further practical evaluation and improvement of the existing criterion numbers of alkali-induced slagging and agglomeration should be improved. The pseudo-4D phase diagrams of (Ma2O)-MaeO-P2O5-Al2O3 and (Ma2O)-MaeO-SiO2-Al2O3 should be constructed from the data derived from real biomass ashes rather than those of simulated ashes in order to provide the capability to predict the properties of silicate melt-induced slagging. Apart from Cr, research should be conducted to understand the effects of Si, Al, and Co, which exhibit high corrosion resistance, and heavy metals such as Zn and Pb, which may form low-melting chlorides that accelerate corrosion. Regulations, cooperation among biomass-fired power plants and other industries, potential technical research, and logistics should be strengthened to enable the extensive utilization of biomass ash. Finally, alkali-induced slagging, silicate melt-induced slagging, agglomeration, and corrosion occur concurrently, and thus, these issues should be investigated jointly rather than separately. 相似文献
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《能源学会志》2020,93(6):2409-2414
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. 相似文献
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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. 相似文献
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D. Vamvuka M. Pitharoulis G. Alevizos E. Repouskou D. Pentari 《Renewable Energy》2009,34(12):2662-2671
Aiming at investigating the role of minerals in evaluating co-firing applications of low rank coals and biomass materials, agricultural residues characteristic of the Mediterranean countries, one lignite and their blends with biomass proportions up to 20% wt, were burned in a lab-scale fluidized bed facility. Fly ashes and bed material were characterized in terms of mineralogical, chemical and morphological analyses and the slagging/fouling and agglomeration propensities were determined.The results showed that combustion of each fuel alone could provoke medium or high deposition problems. Combustion of raw fuels produced fly ashes rich in Ca, Si and Fe minerals, as well as K and Na minerals in the case of biomass samples. However, blending of the fuels resulted in a reduction of Ca, Fe, K and Na, while an increase of Si and Al elements in the fly ashes as compared to lignite combustion, suggesting lower deposition and corrosion problems in boilers firing these mixtures. The use of bauxite as an additive enriched bottom ash in calcium compounds. Under the conditions of the combustion tests, no signs of ash deposition or bed agglomeration were noticed. 相似文献
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Md Tanvir ALAM Baiqian DAI Xiaojiang WU Andrew HOADLEY Lian ZHANG 《Frontiers in Energy》2021,15(1):46
Gasification or combustion of coal and biomass is the most important form of power generation today. However, the use of coal/biomass at high temperatures has an inherent problem related to the ash generated. The formation of ash leads to a problematic phenomenon called slagging. Slagging is the accumulation of molten ash on the walls of the furnace, gasifier, or boiler and is detrimental as it reduces the heat transfer rate, and the combustion/gasification rate of unburnt carbon, causes mechanical failure, high-temperature corrosion and on occasions, superheater explosions. To improve the gasifier/combustor facility, it is very important to understand the key ash properties, slag characteristics, viscosity and critical viscosity temperature. This paper reviews the content, compositions, and melting characteristics of ashes in differently ranked coal and biomass, and discusses the formation mechanism, characteristics, and structure of slag. In particular, this paper focuses on low-rank coal and biomass that have been receiving increased attention recently. Besides, it reviews the available methodologies and formulae for slag viscosity measurement/prediction and summarizes the current limitations and potential applications. Moreover, it discusses the slagging behavior of different ranks of coal and biomass by examining the applicability of the current viscosity measurement methods to these fuels, and the viscosity prediction models and factors that affect the slag viscosity. This review shows that the existing viscosity models and slagging indices can only satisfactorily predict the viscosity and slagging propensity of high-rank coals but cannot predict the slagging propensity and slag viscosity of low-rank coal, and especially biomass ashes, even if they are limited to a particular composition only. Thus, there is a critical need for the development of an index, or a model or even a measurement method, which can predict/measure the slagging propensity and slag viscosity correctly for all low-rank coal and biomass ashes. 相似文献
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大型电站锅炉采用切向燃烧方式燃用无烟煤的研究 总被引:2,自引:0,他引:2
无烟煤的特点是挥发分低,发热量高,着火温度高。在燃烧过程中存在的主要问题是着火困难、燃烧效率低、炉膛易结渣、NOx排放高。作为我国特定地区的一种动力用煤,燃用无烟煤的电站锅炉在设计时重点考虑着火、稳燃、提高燃烧效率、防止炉膛结渣、降低NOx排放。介绍了无烟煤的主要燃烧方式和大型锅炉采用四角切向燃烧技术燃用无烟煤的设计原则。此外,还介绍了上海锅炉厂有限公司设计的300MW自然循环、切向燃烧无烟煤锅炉的特点和运行结果,并对燃用无烟煤燃烧技术在600MW无烟煤锅炉上的应用前景做了预测。 相似文献
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针对循环流化床锅炉燃用准东煤带来的受热面结渣和沾污问题,从降低入炉煤碱金属着手,采用准东五彩湾煤掺烧不同比例的煤矸石、低钠煤、沙漠黄沙,探究不同掺烧物料及比例对锅炉受热面结渣和沾污的影响。研究结果表明:掺烧25%煤矸石时,炉内受热面沾污、结渣严重,且存在频发的爆管现象;掺烧38%艾维尔沟低钠煤时,各级受热面均比较干净,没有明显的结渣沾污现象,但锅炉运行成本显著增加;掺烧5%古尔班通特沙漠黄沙时,仅在一级蒸发管高温烟区出现了类似于沙子的大焦块,其余受热面均比较光滑、干净,没有结渣和沾污现象。 相似文献