循环流化床煤着火特性的试验研究

对不同煤种在循环流化床（CFB）条件下的着火温度进行了试验研究，分析了流化床条件下煤着火燃烧的特点，并对流化床煤的着火温度进行了公式拟合，提出了简单的计算方法。对燃烧无烟煤的CFB锅炉，建议采用启动煤点火。     

富氧气氛煤粉气流着火特性的实验研究

在沉降炉上,研究了神木煤和褐煤在不同煤粉浓度和不同氧气浓度下着火特性的变化.存在一个使着火温度最低的煤粉浓度.煤粉气流的着火温度随着氧气浓度的升高而降低.神木煤当煤粉浓度在氧气浓度为40%、煤粉浓度为0.57 kg/kg时,着火温度为428℃,神木煤在此时足以替代油作为电站锅炉点火启动和低负荷稳燃的燃料.着火前期物CH4、CO随着氧气浓度的升高,峰值上移,也就意味着着火点向上移动,当氧气浓度大于60%时,煤粉表面有烧结现象使着火点下移.富氧条件下煤粉燃烧时易烧结.     

煤颗粒在流化床中着火和燃烬特征研究

根据煤的经典着火理论，从建立煤在流化床中燃烧的热平衡方式入手，建立煤颗粒在流化床中着火和燃烬的热力模型，并用褐煤在小型电加热流化床上进行了试验研究。研究表明对宽筛分煤和窄筛分煤，着火温度既是煤颗粒自身性质的函数也是运行条件的函数。当其他条件确定以后，着火时间和燃烬时间随流化床温度的变化而平滑变化。随着燃烧进行，灰层阻力的作用越来越显著。对流化床锅炉而言，当煤颗粒含碳量降到一定程度后，即认为燃烧结束是可以接受的。     

宽筛分煤粒在循环流化床内应用的特性

目前我国的循环流化床锅炉大多采用8mm以下宽呼分的煤位，这不同于国外循环流化床锅炉使用的窄筛分物料，这种宽筛分煤位中的细粉部分和大领位部分在流化床内的运动特性和着火燃饶有不同的表现。本文从空气动力特性和燃烧特性两方面进行了初步的理论探讨，并由此对循环流化床的设计和运行提出了建议．     

燃用稻壳流化床锅炉的试验研究及35t／h锅炉的设计

介绍了在小型试验台上燃用稻壳流化床锅炉的关键技术，诸如稻壳，稻壳与砂，稻壳与砂及煤等多组份物料的流化特性与混合特性，并介绍了稻壳在流化床中的着火特性和燃烧特性，得到了一系列有指导意义的结论。在此基础上，完成了３５ｔ／ｈ稻壳流化床锅炉的设计，为稻壳流化床燃烧锅炉设计和运行提供了理论依据和实际经验。     

福建无烟煤富氧燃烧的应用性研究

针对燃用福建无烟煤的循环流化床(CFB)锅炉在运行中存在的问题和矛盾,提出了采用富氧燃烧技术改善福建无烟煤的着火和燃烧特性.通过热重分析法研究了龙岩煤在不同氧浓度(20%、30%、40%、60%、100%)的燃烧行为.实验结果表明,随着氧浓度的增大,煤样的着火温度及燃尽温度均呈下降趋势,燃烧强度增强,着火提前且燃烧时间缩短.对富氧燃烧技术应用于CFB锅炉燃烧福建无烟煤存在的若干问题进行了较深入的探讨,并提出相关建议.     

KZL4-13锅炉节能消烟改造

1 前言 我厂 ＫＺＬ４— １３ＡⅢ型锅炉,自 １９８７年投入运行,燃用的是优质烟煤,燃烧状况不错,现改为燃用地方小窑煤种,因为煤种多变,出现着火不利,炉膛温度偏低,炉渣含碳量高,严重制约了锅炉出力,而且烟尘排放不达标,严重污染环境,针对这些问题,我厂对锅炉进行了改造．２锅炉存在的问题及原因分析 这台ＫＺＬ４—１３锅炉在燃用地方小窑煤后,运行中表现为：炉内前部火焰充满度差,着火点靠后,距煤闸板３００mｍ,并参差不齐．煤质变差时,时常出现断火、跑火等现象,造成炉膛温度低,炉渣含碳量高达３５％,出力严重不足…     

生物质与煤掺烧燃烧特性的实验研究

利用热重分析仪,在不同条件下,对单一生物质、煤及其混合物的燃烧特性进行分析,研究了木屑、稻壳、稻草及耒阳白沙煤的着火温度、燃烧最大速率温度和燃烬温度等燃烧特性参数。实验结果表明,生物质的着火温度比白沙煤低,生物质在燃烧过程中有两个明显的失重阶段,而煤只有一个明显的失重阶段。通过掺烧可以使生物质与煤的混合物着火温度降低,着火时间缩短,延长了整个燃烧的温度区间,使煤能更好地燃尽,使燃料的燃烧特性得到了优化。随着生物质掺混比例的提高,掺混样品着火点温度降低得更加明显;且生物质颗粒尺寸由R90变为R200时,同样的掺混比例下,尺寸R200的掺混样品着火温度更低。     

浅析465t/h循环流化床锅炉爆燃原因及应对措施

通过对465 t/h循环流化床(CFB)锅炉在试运中锅炉的爆燃和原因分析,从增加启动床料、控制投煤温度及方式等方面,提出了预防和控制爆燃的措施,取得了较好的效果。因此,对同类循环流化床锅炉运行具有一定的参考价值。     

循环流化床锅炉的设计理论与设计参数的确定

提出了循环流化床锅炉的流态性质、定态设计、物料平衡的设计理论。介绍了清华大学提出的循环流化床锅炉的标准实验方法，包括煤成灰磨耗实验方法、石灰石爆裂磨耗及反应活性实验方法、点火温度测量方法及给煤输送特性测量方法。这些实验结果是锅炉设计运行的基础数据。     

增压流化床锅炉床下点火启动过程的研究与应用

分别在实验室规模常压模拟增压流化床燃烧室和１５ＭＷｅ ＰＦＢＣ－ＣＣ联合循环中试电站６０ｔ／ｈ蒸 发量的ＰＦＢＣ锅炉上进行了增压流化床锅炉床下点火启动特性的试验研究和应用实践．试验了热烟气点 燃流化床的煤种适应性;研究了加煤床温、埋管受热面、热烟气温度和流化风量等参数对床层冷启动和热 启动过程的影响规律．验证了为增压流化床锅炉设计的启动系统中带有气封结构风室的可靠性和烟气分 布的均匀性。考察了增压流化床在深床运行中实施压火后,能再次热启动的条件及所需的燃油量和煤量 的变化。将热烟气床下点火技术和热烟气与主燃风的同风室结构应用于中国第一座ＰＦＢＣ－ＣＣ中试电站, 取得了点火过程稳定可靠和安全的效果．     

Experimental study on coal multi-generation in dual fluidized beds

An atmospheric test system of dual fluidized beds for coal multi-generation was built.One bubbling fluidized bedis for gasification and a circulating fluidized bed for combustion.The two beds are combined with two valves:one valve to send high temperature ash from combustion bed to the gasification bed and another valve to sendchar and ash from gasification bed to combustion bed.Experiments on Shenhua coal multi-generation were madeat temperatures from 1112 K to 1191 K in the dual fluidized beds.The temperatures of the combustor are stableand the char combustion efficiency is about 98%.Increasing air/coal ratio to the fluidized bed leads to theincrease of temperature and gasification efficiency.The maximum gasification efficiency is 36.7% and thecalorific value of fuel gas is 10.7 MJ/Nm3.The tar yield in this work is 1.5%,much lower than that of pyrolysis.Carbon conversion efficiency to fuel gas and flue gas is about 90%.     

Combustion of single coal particles in a jet

Fluidized bed combustion has attracted much interest in recent years, but there is very little data on the behavior of coal particles at these new conditions. Coal of much larger diameter (1–10 mm), much lower furnace temperatures (~850 °C), and different fluid mechanical conditions exist compared to pulverized coal furnaces. This paper presents experimental data on the behavior and combustion rates of individual coal particles aerodynamically suspended in a heated jet, to stimulate flow conditions in a fluidized bed.Tests of bituminous, sub-bituminous and lignite coals from 2 to 12 mm at jet temperatures of 705 and 816 °C in air and air diluted with equal parts of nitrogen were conducted. The ignition delay time varied from 2 to 44 sec. The devolatilization time extended up to 80 sec and was dependent mainly on particle size. The total burn time was independent of coal type and temperature, and varied as the square of the size and inversally with the oxygen concentration. The total turn time varied from 25 to 740 sec independently of coal type. The square law for the char burning rate was investigated.     

Experimental research of radiative heat transfer in fluidized beds

A new method to measure the radiative heat transfer in fluidized beds was presented. Experiments were carried out on a 0.8 th⁻¹ fluidized bed combustion boiler. The residual slag of fired coal was operated in a fluidized bed at room temperature. As the radiative heat transfer at room temperature is insignificant, its contribution at high temperatures might be obtained by the comparison of experimental results at high and low temperatures. On experimental study, a radiative contribution was given as a function of bed temperature and particle size. The results were compared with those in other references.     

75t／h洗煤泥流化床锅炉设计与点火运行

介绍采用浙江大学开发的异比重流化床技术燃用洗煤泥的75t/h流化床锅炉设计的设计技术特点,点火过程及运行情况。运行表明,该锅炉为我国矿区洗煤泥资料化利用提供了先进的技术手段。     

Experimental Study on Oxy-Fuel Combustion and NO Emission in a Spouted-Fluidized Bed with under Bed Feeding

The spouted-fluidized bed is modified from the classical fluidized bed device, which combines the features of spouted and fluidized beds. In the present work, the performance of oxy-fuel spouted-fluidized bed combustion with under bed feeding and its effect on NO emission were systematically investigated. The results revealed that it was feasible to use a spouted-fluidized bed combustor for oxy-fuel combustion with real flue gas recycling. The transition from air combustion to oxy-fuel combustion was smooth and the concentration of CO_2 in the flue gas could be as high as 90% steadily(dry base). Increasing the reaction temperature exhibited a negative effect on NO emission. Compared with that under the shallow bed, the concentration of NO in the flue gas was lower under the deep bed condition. Besides, the utilization of crush particles was favorable for suppressing NO emission because of the promoted mixing between coal particles and solid bed materials. Furthermore, the addition of limestone was proven to undesirably increase the NO emission during oxy-fuel spouted-fluidized bed combustion.     

基于灰颗粒的物理特性为分类原则的试验研究

循环流化床(CFB)锅炉炉内的燃烧及传热与炉内床料的状态密切相关,而炉内床料主要是由燃煤含有的矿物组分经过燃烧、爆裂和磨耗过程形成的。文中对6种煤样在固定床燃烧后,使用可视化显微仪,获取了灰颗粒的微观形貌特征,根据灰颗粒的机械强度和耐磨性能的不同,将灰颗粒定义为3类不同性质的灰。以此为基点,采用固定床燃烧后冷态振动筛分和流化床实验台热态流化后筛分的方法,研究了不同燃烧温度下升温速率对灰颗粒粒径变化的影响,以及不同燃烧温度下燃烧时间对灰颗粒粒径变化的影响,推演了不同煤样在燃烧过程中的演化特征。结果表明:3类灰颗粒在不同的燃烧温度和时间的演化过程存在明显的不同,从而为预测循环流化床中的床料粒径分布提供了理论依据。     

Combustion of isolated bubbles in an elevated-temperature fluidized bed

Combustion of isolated bubbles was investigated with a laboratory-scale fluidized-bed reactor. Two different combinations of oxygen and argon were employed as the fluidizing gas. Single bubbles of methane were injected into an incipiently fluidized bed maintained at elevated temperatures. Gas composition inside the bubbles was measured using a suction probe connected to an on-line mass spectrometer, and the temperature of the bubbles was monitored using a fast-response thermocouple. The effects of bed particle type, particle size, bubble size, bed temperature, and oxygen concentration in the emulsion phase were examined for bed temperatures between 923 and 1203 K. A theoretical model of homogeneous combustion within the bubble phase was developed for comparison to the experimental results. The model accounted for the heat and mass transfer between bubble and emulsion phases, but only considered combustion within the bubble. The results indicated that small bubble size and high oxygen concentrations in the emulsion phase enhanced bubble-phase combustion. The bed temperature also proved to be an important parameter, with higher temperatures promoting bubble combustion, but unlike some other investigations, no critical ignition temperatures were observed in either experiments or model results. The fluidized bed's particle size and particle composition influence the heat and mass-transfer coefficients, and therefore the bubble-phase combustion, but these have a smaller influence than bed temperature and bubble size. Model results for bubble-phase gas composition and temperature compared favorably with the experimental measurements.     

Modeling of single coal particle combustion in O2/N2 and O2/CO2 atmospheres under fluidized bed condition

A one-dimensional transient single coal particle combustion model was proposed to investigate the characteristics of single coal particle combustion in both O₂/N₂ and O₂/CO₂ atmospheres under the fluidized bed combustion condition. The model accounted for the fuel devolatilization, moisture evaporation, heterogeneous reaction as well as homogeneous reactions integrated with the heat and mass transfer from the fluidized bed environment to the coal particle. This model was validated by comparing the model prediction with the experimental results in the literature, and a satisfactory agreement between modeling and experiments proved the reliability of the model. The modeling results demonstrated that the carbon conversion rate of a single coal particle (diameter 6 to 8 mm) under fluidized bed conditions (bed temperature 1088 K) in an O₂/CO₂ (30:70) atmosphere was promoted by the gasification reaction, which was considerably greater than that in the O₂/N₂ (30:70) atmosphere. In addition, the surface and center temperatures of the particle evolved similarly, no matter it is under the O₂/N₂ condition or the O₂/CO₂ condition. A further analysis indicated that similar trends of the temperature evolution under different atmospheres were caused by the fact that the strong heat transfer under the fluidized bed condition overwhelmingly dominated the temperature evolution rather than the heat release of the chemical reaction.