流化床生物质锅炉燃料适应性分析与改进

简要介绍我国各种生物质燃料,并分析生物质燃料水分、灰量、灰分等特性变化对生物质循环流化床锅炉给料、燃烧等流程的影响;同时提出一些针对性的解决措施,以提高流化床生物质锅炉及其系统设备的适应性和可靠性,使生物质直燃技术产生更高的社会和经济效益。     

燃用玉米芯的循环流化床锅炉热风系统研究与设计

介绍了一种循环流化床锅炉热风系统的设计,该系统的热源为一燃用玉米芯的循环流化床热水锅炉,燃料燃烧产生的热首先产生热水,热水在换热器内与空气换热,然后产生43℃热风.这套系统设计关键为锅炉的燃烧温度选择、灰渣质量平衡以及如何保证热风风温稳定等.为进行这套系统的设计,通过试验研究了玉米芯在流化床内的燃烧特性、灰渣结焦特性以及循环床回料器的回料特性.在试验基础上,设计了这套热风系统,这套热风系统由锅炉、换热器、调节系统、除尘器等组成.首台采用该技术的热风系统已在山东登海先锋种业公司投产.这套系统可作为设计燃用稻壳、秸秆等其他生物质燃料锅炉的参考.     

生物质散料直燃技术在循环流化床锅炉中的应用

生物质散料作为一种可再生燃料,易于获得,燃烧后产物内含污染物少,是相对洁净的燃料.循环流化床多回料燃烧技术是一种有自身特点和发展前途的高效、低源头污染排放符合能源政策发展的燃烧技术.针对生物质散料燃烧特性和循环流化床燃烧技术优势互补的特点,通过介绍1台纯燃生物质散料锅炉的开发设计,阐述了利用循环流化床燃烧技术进行纯燃生...     

生物质燃料在燃煤锅炉上直接燃烧的试验研究

在1台燃煤锅炉上进行了生物质燃料燃烧试验和与燃煤的对比试验。结果显示,燃煤锅炉须经改造才能适应生物质燃料。生物质燃料与燃煤比较,不论燃料性质、燃烧现象、结焦特性、对炉膛的要求等方面都不同。生物质燃料燃烧时出现了不低于1 300℃高温区域和较高的NOx排放,与文献报道差别较大。     

循环流化床锅炉在农林生物质发电项目上的应用

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。     

简谈1台燃高水分糠醛渣锅炉的设计

分析了糠醛渣物理特性、燃烧机制,介绍了笔者在锅炉设计中,采用V+4T生物质直燃高低差速床技术,通过合理布置尾部受热面,解决了在燃烧低灰溶点、高水分糠醛渣燃料时的结焦、积灰、磨损与腐蚀等多个技术难题。     

循环流化床生物质直燃锅炉运行问题与设计优化

简述了现阶段我国循环流化床生物质燃料的燃烧特性及技术条件,生物质直燃循环流化床锅炉运行出现的主要问题。针对75 t/h次高温次高压生物质流化床锅炉的关键技术进行优化设计并取得良好效果,为广大技术人员提供有益的参考。     

燃烧方式对生物质理论燃烧温度的影响

采用与生物质燃料特性相近的褐煤为过量空气系数的定性指标,确定了生物质采用固定床、流化床、悬浮燃烧和气化燃烧4种燃烧方式的过量空气系数,依据锅炉机组热力计算标准方法,研究了热值、过量空气系数和燃烧方式对理论燃烧温度的影响。研究结果表明:理论燃烧温度与燃料的低位发热量正相关;理论燃烧温度随过量空气系数的增大而降低;采用流化床、悬浮燃烧和气化燃烧3种燃烧方式,生物质燃料均能够获得较高的理论燃烧温度,其中,采用气化燃烧方式的理论燃烧温度最高。文章的分析结果为生物质燃烧方式的选取及生物质锅炉的设计提供了理论依据。     

浸废渣和褐煤掺烧的循环流化床锅炉设计分析

生物质燃料用于循环流化床锅炉是一项新的技术。本文针对一台燃烧浸废渣－褐煤混合燃料的３５ｔ／ｈ循环流化床锅炉的设计,探讨和分析了生物质循环流化床锅炉设计中所要考虑的一些设计参数和运行参数,为生物质燃料循环流化床锅炉的研发提供了一些依据和建议。     

流化床燃烧煤的成灰磨耗特性

循环流化床燃烧条件下，煤的成灰磨耗特性是影响床的流化特性和锅炉整体性能的重要因素之一。将煤在床内爆裂和燃尽引起的尺寸减损和颗粒的磨耗视为相互独立的两个过程，利用静态燃烧然后冷态流化的方法，得到成灰与磨耗参数，提出煤种的本征成灰数据概念，认为煤种的本征成灰数据应视为只与煤种本身特性有关的燃料特性参数，建议将其作为设计循环流化床锅炉的燃料数据。     

生物质内循环流化床气化炉结焦特性

分析了近年来生物质流化床气化炉的结焦研究的状况,总结了影响生物质流化床气化过程中结焦的因素和确定结焦时最小流化速度的几类计算方法。分析了辽宁营口160kW气化装置结焦过程中运行参数的变化情况,给出防止结焦发生的一些措施。     

Model validation of a CFB biomass gasification model

The developed 1-dimensional biomass gasification mathematical model [1] was validated using the experimental results obtained from a circulating fluidized bed biomass gasifier. The reactor was operated on rice husk at various equivalence ratios (ER), fluidization velocities and biomass feed rates. The model gave reasonable predictions of the axial bed temperature profile, syngas composition and lower heating value (LHV), gas production rate, gasification efficiency and overall carbon conversion. The model was also validated by comparing the simulation results with two other different size circulating fluidized beds biomass gasifiers (CFBBGs) using different biomass feedstock, and it was concluded that the developed model can be applied to other CFBBGs using various biomass fuels and having comparable reactor geometries.     

Ash effects during combustion of lignite/biomass blends in fluidized bed

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.     

Case studies––Problem solving in fluidized bed waste fuel incineration

Fluidized bed combustion technology has been widely used as the new, flexible, multi-fuel boiler for waste combustion and energy recovery from low grade fuels. However, problems such as low thermal efficiency, high emissions, bed agglomeration etc. are still encountered in the operation of fluidized beds. Valuable experiences were gained from two case studies recently conducted regarding wastes combustion in industrial scale fluidized beds.In the first case, the performance of a fluidized bed combustor for energy recovery from oil sludge was evaluated during the commissioning trials. Apart from the sludge characterization and bed material analysis, the combustion efficiency, solid flow balance and on stack emission of CO, SO_x and NO_x were investigated, as well as the fluidization quality. Although the system was operated with good combustion efficiency (>99.9%), sulfur dioxide emission (>1000 ppm) was found to be substantially higher than the allowable discharge limit. It was recommended to increase the limestone feed rate in order to meet the SO₂ emission standard, and subsequently, installation of a cyclone is suggested to remove the potentially significant increase in ash and fine particles.The second case study focused on the bed agglomeration observed in a fluidized bed incinerator where a burning blend of three wastes (i.e. carbon soot, biosludge and fuel oil) is involved. To understand the mechanisms and related chemistry, several analytical approaches are employed to identify the bed materials (fresh sand and degrader sand) and the clinkers formed from full scale incinerator tests. The formation of clinker is believed to follow the mechanism of partial melting and/or reactive liquid sintering. The effects of temperature and blending ratio are tested in a muffle furnace. Carbon soot is believed to be more susceptible than the other two fuels. Thermodynamic multi-phase multi-component equilibrium (TPCE) calculations predict that the main low melting point species are predominant under the oxidizing condition, suggesting that reducing conditions might be favorable to restrain bed agglomeration. This study provides valuable information for better understanding of the chemistry related to clinker formation; it also helps in developing methods for control and possible elimination of the bed agglomeration problem for the design fuels.     

生物质成型燃料循环流化床燃烧试验研究

在0.15 MW循环流化床试验台上,进行了玉米秸秆和苹果树枝成型燃料燃烧特性以及排放特性的试验研究.试验结果表明,玉米秸秆成型燃料和苹果树枝成型燃料在循环流化床中能够稳定燃烧,燃烧效率达到96.8%;尾气中HCl的排放质量浓度较高,SO2的排放质量浓度随着生物质的硫含量增大而增大;使用选择性炉渣作为床料同时加入黏土作为添加剂的方法,能够有效抑制玉米秸秆成型燃料和苹果树枝成型燃料燃烧过程中床料的黏结,黏土对循环流化床的物料循环流化起到了稳定作用.     

Bench-scale bubbling fluidized bed systems around the world - Bed agglomeration and collapse: A comprehensive review

Thermochemical conversion by gasification process is one of the most relevant technologies for energy recovery from solid fuel, with an energy conversion efficiency better than other alternatives like combustion and pyrolysis. Nevertheless, the most common technology used in the last decades for thermochemical conversion of solid fuel through gasification process, such as coal, agriculture residues or biomass residues are the fluidized bed or bubbling fluidized bed system. For these gasification technologies, an inert bed material is fed into reactor to improve the homogenization of the particles mixture and increase the heat transfer between solid fuel particles and the bed material. The fluidized bed reactors usually operate at isothermal bed temperatures in the range of 700–1000 °C, providing a suitable contact between solid and gas phases. In this way, chemical reactions with high conversion yield, as well as an intense circulation and mixing of the solid particles are encouraged. Moreover, a high gasification temperature favours carbon conversion efficiency, increasing the syngas production and energy performance of the gasifier. However, the risk of eutectic mixtures formation and its subsequent melting process are increased, and hence the probability of bed agglomeration and the system collapse could be increased, mainly when alkali and alkaline earth metals-rich biomasses are considered. Generally, bed agglomeration occurs when biomass-derived ash reacts with bed material, and the lower melting temperature of ash components promotes the formation of highly viscous layers, which encourages the progressive agglomerates creation, and consequently, the bed collapse and system de-fluidization. Taking into account the relevance of this topic to ensure the normal gasification process operating, this paper provides several aspects about bed agglomeration, mostly for biomass gasification systems. In this way, chemistry and mechanism of bed agglomeration, as well as, some methods for in-situ detection and prediction of the bed agglomeration phenomenon are reviewed and discussed.     

Biomass gasification as the first hot step in clean syngas production process – gas quality optimization and primary tar reduction measures in a 100 kW thermal input steam–oxygen blown CFB gasifier

Syngas production based on biomass gasification is an attractive, feasible alternative to fossil fuel feedstock for the production of transportation fuels. However, the product gas from biomass gasification must be cleaned and tailored to comply with strict syngas quality requirements, as it consists of a wide variety of major and minor components and impurities. The characterization of such species is important to determine downstream gas treatment steps, and to assess the efficiency of the gasification process.This paper gives an overview of the results obtained during experiments on steam–oxygen gasification of biomass using 100 kW maximal thermal input circulating fluidized bed gasifier (CFBG) that have been performed at Delft University of Technology during the CHRISGAS project. The unit is also equipped with a high-temperature ceramic gas filter and downstream reactors for upgrading of the gas.In the experiments biomass types of both woody and agricultural origin have been used. They were represented by clean wood, demolition wood, an energy crop species (miscanthus) and a true residue (Dutch straw), respectively. Moreover, different bed materials have been applied, namely quartz sand, treated and untreated olivine and magnesite. During the experiments extensive measurements of gas composition have been carried out throughout the integrated test rig. The gas characterization included major gas components as well as certain minor species and tar.The results show that with the use of magnesite as bed material, remarkable increases of hydrogen yield were attained, as compared to sand or olivine; up to a volume fraction of almost 40% (dry, nitrogen-free basis). Also the H₂:CO ratio increased from values near or lower than 1 to 2.3–2.6. This is near the values needed, for e.g., Fischer–Tropsch diesel production, indicating a potential for simplification of the gas upgrading. Furthermore, by using magnesite tar content of the raw gas was reduced to values near 2 g m^?3 (STP). Moreover, magnesite complied with the expectation to have a positive impact on agglomeration prevention for the agricultural fuels containing alkali and chlorine in the ash. The kind of olivine applied during the experiments did not yield the expected tar reduction; the measured tar concentration was even higher than when quartz sand was used as bed material. Finally kaolin proved to be an effective additive to counteract the agglomeration when fuels with high alkali content in the ash are gasified using bed material that is rich in silica, as it is the case with quartz sand and olivine.     

燃生物废料流化床锅炉

介绍了国内外生物质开发与利用现状,燃生物废料锅炉炉型的选择以及生物废料在流化床中燃烧存在的烧结问题有解决措施,还介绍哈尔滨工业大学研制的一系列燃生物废料流化床锅炉及其运行结果。     

Hydrogen and syngas production from biomass gasification for fuel cell application

Gasification process is being developed to produce a clean and efficient gas flue from fuels such as coal, biomass, and solid/liquid wastes for power generation. In this work, a biomass gasification kinetic model that can predict reaction temperature, gasification performance, and gas composition has been developed for a circulating fluidized bed (CFB). Experimental data from a CFB power plant have been used to validate the model. It is confirmed that the addition of steam is important for increasing the hydrogen concentration and syngas caloric value. Based on the predicted results, an optimal condition is suggested for air and steam gasification in the CFB gasifier.     

高水分燃料的沸腾层烟气热平衡方程

以树皮、褐煤、I类烟煤为例,分析了沸腾层内未燃烧燃料中的水分蒸发吸热对埋管吸热份额和沸腾层温度的影响得到了高水分燃料的沸腾层烟气热平衡方程。计算和分析表明,对高水分燃料,沸腾层内未燃烧燃料中的水分蒸发吸热所需热量较大,在沸腾层烟气热平衡方程中应予考虑。