Generation and reduction of nitrogen oxides in firing different kinds of fuel in a circulating fluidized bed

The processes through which nitrogen oxides are generated and reduced in the course of firing different kinds of fuel in a circulating fluidized bed are addressed. All experimental studies were carried by the authors on their own laboratory installations. To construct a model simulating the generation of nitrogen oxides, the fuel combustion process in a fluidized bed was subdivided into two stages: combustion of volatiles and combustion of coke residue. The processes through which nitrogen oxides are generated and reduced under the conditions of firing fuel with shortage of oxygen (which is one of efficient methods for reducing nitrogen oxide emissions in firing fuel in a fluidized bed) are considered.     

流化床常压空气部分气化和半焦燃烧的试验研究

为进行煤的多联产方案研究,在1 MW循环流化床热电气多联产试验装置上,选取兖州煤、大同煤为试验煤种进行了部分空气气化和半焦燃烧试验。试验结果表明,空气部分气化方案得到的煤气热值较低,为3~5 MJ/m3,在气化炉中的碳转化率为40%~70%,剩余半焦被送入循环流化床反应器中燃烧,该系统的总体转化效率为90%左右。气化炉床层温度对气化炉碳转化率影响较大,随着温度升高其碳转化率明显提高,而燃烧炉燃烧效率呈下降趋势。石灰石的加入除了对焦油的裂解有一定的促进作用外,还具有脱除硫化氢作用,当[Ca]/[S]为3时,脱硫效率为90%。气化炉的给煤量、燃烧炉运行温度随气化炉鼓风温度提高而增加。     

Three-zonal engineering method of heat calculation for fluidized bed furnaces based on data on commercial investigations of heat generation distribution during biomass combustion

A three-zonal method of heat calculation of furnaces for combustion of biomass and low-caloric fuel in the fluidized bed is described. The method is based on equations of thermal and material balances that account for heat generation by fuel in the zone, heat-and-mass transfer heat exchange between the furnace media and surfaces that bound the zone, and heat-and-mass transfer between furnace zones. The calculation procedure for heat generation by fuel in the fluidized bed (FB) using the heat generation portion by the fuel is proposed. Based on commercial investigations, the main factors that affect the average temperature in the FB and the portion of fuel heat that is released in the FB are determined. Results of commercial investigations showed that the airflow coefficient in the FB should be recognized as the main operation parameter that affects the average temperature in the FB and, consequently, heat generation in the FB. The gas flow rate in the FB can be marked out as the second factor that affects the consumption degree of oxidizer supplied in the FB. Commercial investigations revealed that mixing is affected by the gas flow rate in the FB and the bed material particle size, which may be changed during the boiler operation because of the agglomeration of particles of sand and ash. The calculation processing of commercial investigations on a KM-75-40M boiler of a CHP-3 of an Arkhangelsk Pulp and Paper Mill (APPM), which was carried out using the inverse problem procedure by means of a developed computer program, determined the range of the fuel heat release share in the FB, which was 0.26–0.45 at an excess air factor of 0.59–0.93 in the bed, and the heat release share in the maximum temperature zone in the total heat release in the superbed space. The heat release share in the bed is determined as an approximating function of the excess air factor in the bed and the fluidization number. The research results can be used during designing boilers with the fluidized bed on biomass.     

Combustion of black coal in the form of coal-water slurry in low-capacity boilers

The present paper describes the examples of experimental and industrial implementation of technologies of flame-droplet combustion of the coal-water mixture in furnaces above a bed consisting of burning coal and in a swirling-type furnace chamber. For preparing coal-water fuel (CWF), Kuznetsk coals of G and D ranks, as well as tailings of coking coals, were used. The future prospect of both technologies of coal combustion has been shown from both economic and environmental standpoints.     

Air-based coal gasification in a two-chamber gas reactor with circulating fluidized bed

During the bed gasification of solid fuels, the process temperature in the reaction zone is not high enough for reaching the maximum rate of the chemical efficiency factor of the gasification process. In order to increase the chemical efficiency factor, it is necessary to supply extra heat to the reaction zone to increase the reaction temperature. In this article, coal gasification in a chamber with forced fluidized bed is considered and it is proposed to supply extra heat with a circulating flow of an inert particulate heat transfer agent. Circulating inert particulate material is successively heated by coal combustion in a cone chamber with bubbling fluidized bed and in a combustion chamber with a spherical nozzle that inhibits the forced fluidized bed. After that, the heat transfer agent heated to 930–950°C enters first in a gasification chamber with bubbling bed and then in a chamber with forced fluidized bed, where it transfers the physical heat to the air fuel mixture. The experiments conducted with crushed Borodinsky coal and inert particulate heat transfer agent (electrocorundum) showed the temperature rise in a gasification chamber with from 760 to 870°C and the increase in the combustible component (CO) concentration in the gasification products by 5.5%. Based on the kinetic equations of the fuel combustion reactions and the CO₂ reduction to CO and on the thermal balance equations of combustion and gasification chambers, the simulation model for the gas composition and the temperature rate calculated by the height of reaction chambers was developed. The experimental temperature rates and product gas compositions are in good agreement with the simulation results based on the proposed kinetic gasification model.     

新建75 t/h高温高压水煤浆锅炉的设计与调试

吉林石化公司有机合成厂新建 75 t/h 高温高压水煤浆锅炉属国内首创产品。燃烧调整试验证明锅炉燃料适应性能好,烧油、烧气和烧浆均能满足设计要求,浆气混烧和全烧浆时燃烧效率均在 99%以上。     

水分对垃圾焚烧影响的实验研究

以层燃-流化复合垃圾焚烧为研究背景,利用实验方法,从垃圾干燥、层燃、流化燃烧3个方面研究了水分对垃圾焚烧过程的影响。垃圾中的过多水分导致垃圾的干燥过程延长,阻碍了垃圾的起燃,吸水性强的垃圾携带较多水分比吸水性弱的垃圾更能阻碍燃烧。在低温层燃状态下,因水煤气反应等作用,CO生成量随着含水率的增加而增加,高温下由于H2O能促进CO的氧化反应,CO随着含水率的增加而降低。高挥发分PVC、PS、木屑等燃料在层燃状态下可产生较高的CO。随着H2O的增加,N向NO、H向CH4的转化率多呈增加的趋势。而在流化燃烧状态下,随着水分的增加,CO降低,NO降低,表明H2O分子在流化床内对燃烧在机理上有强化作用。     

循环流化床锅炉结焦原因分析及预防措施

分析了循环流化床锅炉结焦的原因,认为其主要因床料局部或整体温度超过灰熔点或烧结温度,以及炉内流化工况不良等所致。对此,提出了改变燃煤焦结特性,严格控制运行参数,尽量缩短压火时间等措施,以避免循环流化床锅炉结焦。     

大型循环流化床锅炉启动调试试验及研究

介绍了循环流化床(CFB)锅炉本体及系统设计的主要特点,重点分析了大型循环流化床锅炉启动调试中的重要内容及所存在的问题,针对燃烧阳泉无烟煤的HG480/13.7L.MG21型CFB锅炉的调试实践,提出了风量标定、高温烘炉、蒸汽吹洗、炉膛受热面保护、返料器投入时间和方式、主燃料投入、给煤控制和床下点火燃烧器等调试优化方案。     

A thermodynamic analysis of operating conditions under which coal-water fuel is gasified in flow

A thermodynamic analysis of processes through which coal-water fuel is gasified in a flow is carried out. The influence of temperature, pressure, relative quantity of air, and fraction of moisture in coal-water fuel on the gasification efficiency, content, and yield of synthesis gas is studied.     

高温煤基燃料的燃烧特性及NOx排放试验研究

为了探索控制煤粉燃烧时NOx的生成，参考高温空气燃烧的概念，提出了将煤粉预热到800 ℃的高温后再进一步燃烧的新工艺，方法是借助循环流化床在低过剩空气系数下燃烧的技术预热煤粉，由于煤粉在预热过程中发生了部分气化的反应，将生成物称为高温煤基燃料。在小型热态试验台上完成了第一阶段的概念性验证试验。热态试验台由提供高温煤基燃料的循环流化床和用于高温煤基燃料燃烧的下行燃烧室组成，下行燃烧室的直径为220 mm、高度为3000 mm。试验以大同烟煤为燃料。试验结果表明：下行燃烧室内轴向温度分布比较均匀，最大温差为176 ℃；NOx排放值为399 mg/m3 (@ 6% O2)，低于GB13223 —2003规定的450 mg/m3，高温煤基燃料中的燃料N向NOx的转化率为26.9%；燃烧效率达到99%。     

油页岩和半焦着火特性实验研究

在热重分析仪、固定床和流化床实验台上对油页岩和半焦的着火特性进行了实验研究。在固定床和流化床实验中,根据排放气体(CO,CO2)和床温的变化曲线判断着火温度,结果表明：随着粒径的增大,油页岩和半焦的热重着火温度和流化床一次投料着火温度逐渐增大;固定床实验测得的着火温度比其他技术低,对于流化床一次投料实验,半焦的着火温度在很大程度上取决于投料温度,不同的实验技术对着火机理有很大影响,油页岩固定床实验和流化床间断给料实验为均相着火,流化床一次给料实验油页岩着火机理逐渐向非均相着火过渡;利用热爆炸理论对不同实验条件导致的着火温度不同进行了理论分析,当无量纲换热系数y从0.4167变化到2.0时,无量纲着火温度qg从0.059 9变化到0.067 32。     

循环流化床锅炉二次风射流特性的冷模实验研究

循环流化床二次风的主要作用是为燃料补充燃烧所需的氧气和加强燃料在炉内的扰动,对锅炉燃烧效率有重要的影响。在一个可视化的循环流化床实验装置上进行了炉内物料浓度、二次风喷口直径和风速对二次风射程与扩散影响的冷模实验。采用向炉内送入高温二次风,然后通过布置在二次风平面的热电偶来测量炉内温度变化的方法,间接反映二次风的射程和扩散情况。结果表明,在固体颗粒浓度一定时,最大射流深度、扩散程度与二次风动量成正比;二次风动量一定时,最大射流深度、扩散程度与固体颗粒浓度成反比。     

Organic coal-water fuel: Problems and advances (Review)

The study results of ignition of organic coal-water fuel (OCWF) compositions were considered. The main problems associated with investigation of these processes were identified. Historical perspectives of the development of coal-water composite fuel technologies in Russia and worldwide are presented. The advantages of the OCWF use as a power-plant fuel in comparison with the common coal-water fuels (CWF) were emphasized. The factors (component ratio, grinding degree of solid (coal) component, limiting temperature of oxidizer, properties of liquid and solid components, procedure and time of suspension preparation, etc.) affecting inertia and stability of the ignition processes of suspensions based on the products of coaland oil processing (coals of various types and metamorphism degree, filter cakes, waste motor, transformer, and turbine oils, water-oil emulsions, fuel-oil, etc.) were analyzed. The promising directions for the development of modern notions on the OCWF ignition processes were determined. The main reasons limiting active application of the OCWF in power generation were identified. Characteristics of ignition and combustion of coal-water and organic coal-water slurry fuels were compared. The effect of water in the composite coal fuels on the energy characteristics of their ignition and combustion, as well as ecological features of these processes, were elucidated. The current problems associated with pulverization of composite coal fuels in power plants, as well as the effect of characteristics of the pulverization process on the combustion parameters of fuel, were considered. The problems hindering the development of models of ignition and combustion of OCWF were analyzed. It was established that the main one was the lack of reliable experimental data on the processes of heating, evaporation, ignition, and combustion of OCWF droplets. It was concluded that the use of high-speed video recording systems and low-inertia sensors of temperature and gas concentration could help in providing the lacking experimental information.     

450t/h循环流化床锅炉床温运行特性分析

针对目前循环流化床锅炉床温控制水平较低．难以投入自动控制的问题，基于某电厂450t/h循环流化床锅炉的运行数据和运行实例，较全面地分析了给煤、一次风、氧量、床层高度、负荷等主要因素对床温的影响。分析发现：给煤调节床温具有滞后性，煤质和煤粒径对床温也有一定影响；不同运行工况下一次风对床温可能有不同影响；氧气浓度变化可反映炉内的燃烧工况；密相区料层厚度变化会带来床温变化；床温只是影响负荷的主要因素之一，所得结论可对循环流化床锅炉运行、床温控制系统的设计和了解床温调节规律提供参考。     

循环流化床锅炉与增压流化床锅炉公用煤处理系统合理性分析

通过对循环流化床(CFB)和增压流化床(PFBC)对燃料的粒径要求的分析和技术经济比较,说明贾汪电厂CFB锅炉与PFBC锅炉公用煤处理系统在技术上是可行的,经济上是合理的。     

Mathematical simulation of working processes in the furnace of a circulating fluidized bed boiler

A software system developed for simulating and calculating boiler furnaces with circulating fluidized beds is described. The main principles on which the system is constructed are outlined, and the physical and mathematical models of processes in circulating fluidized bed furnaces are described together with the calculation algorithm. Results from a study of analyzing the effect the grinding fineness of initial fuel particles has on the processes in a circulating fluidized bed furnace are presented.     

75t/h循环流化床锅炉回料阀结焦堵塞的原因分析及处理

对XG-75／3．82-M20型循环流化床锅炉回料阀结焦堵塞原因进行了分析,认为锅炉本体结构和运行因素是造成回料阀堵塞的主要影响因素。通过采取控制床内温度、燃料粒度分布、调整回料阀结构和安装尺寸等措施,可以有效解决循环流化床锅炉回料阀堵塞问题。     

木屑和聚乙烯流化床共气化实验研究

为揭示城市生活垃圾中典型组分在气化过程中的相互作用，该文以木屑和聚乙烯为研究对象，在流化床中进行了单组分和双组分共气化实验研究。结果显示，通过控制燃料量和反应温度，可以避免流化恶化现象发生。木屑与聚乙烯共气化时，CH4的浓度分布与单组分聚乙烯气化CH4趋势一致；共气化时，产品气中CO浓度随着温度升高而降低，近似于单组分木屑和聚乙烯气化时CO浓度的线性组合；共气化时C2Hm生成量减少。静止床高增加时，有利于CO、H2、CH4以及低碳氢化合物的生成。     

200 t/d循环流化床焚烧炉垃圾及纸渣混烧运行实践

介绍了 200 t/d 垃圾、纸渣混烧流化床焚烧炉的设计及运行概况;根据运行及监测结果说明流化床焚烧炉处理生活垃圾及纸渣有燃烧效率高、负荷调节能力强、燃料适应性强、污染物排放低等方面的优势;并在实际运行过程中摸索出了一些可进一步改善和保证流化床焚烧炉稳定运行的经验。