循环流化床锅炉对环保的价值及其立管内物料结渣问题的研究

循环流化床锅炉是减少燃煤锅炉烟气的污染的一个良好选择,这表明了其在环保上的价值,对其立管内物料燃烧结渣影响问题,给出了燃烧过程的特征及各因素的影响作用,并提出了防止结渣的原则。     

锅炉结渣的原因分析及调整

本文介绍中间储仓式锅炉炉膛的结构,结合锅炉制粉系统的结构和炉膛燃烧特性,找出锅炉燃烧时引起结渣的因素,以及对这些结渣因素进行深入分析。提出解决锅炉燃烧结渣的对策。     

电站锅炉结渣与安全问题研究

电站锅炉结渣对锅炉的安全经济运行造成很大危害，影响受热面传热，严重时因通风不良可使燃烧恶化，有可能造成炉膛灭火、爆管、爆炸等。电站锅炉炉膛结渣与煤灰性质、锅炉设计及锅炉运行状况等因素有关。避免锅炉结渣应从燃料的灰熔点、烟温等方面控制。分析了锅炉结渣的原因及引起的安全问题，提出了结渣的控制措施和清渣安全措施。     

循环流化床锅炉结渣特性研究

循环流化床燃烧技术是近年来在国际上发展起来的新一代高效、低污染清洁燃烧技术,生物质燃料是具有广阔发展前景的新型燃料。本文通过循环流化床锅炉中混燃时的结渣问题进行了分析研究,并对解决发电厂锅炉结渣问题给出了相应的技术措施。     

生物质锅炉中碱金属氯化物迁移规律及对炉内结焦的影响

生物质能是一种分布广、资源丰富的可再生能源。然而,这些生物质中碱金属元素含量普遍较高,在燃烧利用过程中碱金属容易与其它成灰元素(如氯、硅)发生化学反应,生成低熔点的物质而造成锅炉受热面结渣,影响锅炉运行的安全性和经济性。本文选用稻草秸秆作为研究对象,利用化学平衡软件Fact Sage中平衡模块EQUILIB对稻草秸秆燃烧过程进行热力学模拟。计算过程考虑了燃烧温度、炉内压力、过量空气系数、燃料中硫元素的含量和氯元素含量五个因素对碱金属氯化物迁移及锅炉结渣的影响,为工程应用中解决生物质锅炉结焦问题提供了参考。     

突变级数法在电站燃煤锅炉结渣预测中的应用

提出了一种基于突变级数理论的电站燃煤锅炉结渣特性的预测方法。首先介绍了突变级数法的基本思想和分析步骤,在找出影响电站燃煤锅炉结渣分级的主要因素之后,对各因素进行排序,并确定各因素指标体系,最后,求出各样本的突变级数,对电站燃煤锅炉结渣等级进行划分。通过工程实例可见,该方法对电站燃煤锅炉结渣分级的预测有效性较高,并且更体现出客观性较强、定量化程度较高,计算简单等优势。     

生物质热转化过程中积灰沾污结渣特性及趋势预测研究进展

为阐明生物质灰的沾污结渣特性及其趋势预测研究现状,使生物质能热转化利用过程更加安全,在综合分析生物质灰沾污结渣的危害及机制的基础上,从沾污结渣特性与沾污结渣预测两方面归纳国内外研究进展,梳理出影响结渣的主要因素——灰分组成、反应温度、气氛和添加剂等;并对沾污结渣趋势的预测方法和研究趋势进行分析。针对实际工程中锅炉受热面结渣和腐蚀问题,可以采用混烧、混入添加剂、水洗、酸洗、改变受热面材料、优化锅炉和烟道结构设计、优化反应条件等措施解决。在生物质灰沾污结渣趋势预测方面,目前并没有完整的统一标准,简单沿用煤灰的结渣指标存在严重的不适应性,且现有的预测方法通常只考虑固态或熔融成分对结渣的影响,而忽略了碱金属、氯、硫等元素挥发与温度变化的关系。因此,以热转化过程中碱金属的气-固分配趋势为基础,结合不同温度下生物质灰的特点及成灰特性,建立适用于不同温度下生物质灰的沾污结渣预测模型,是下一步研究应重点关注的问题。     

碱金属迁移转化对生物质灰沾污结渣的影响研究进展

生物质热化学转化利用过程会产生大量的生物质灰,其钾、钠等碱金属元素的含量高,导致其熔融温度低,在高温下极易熔融或挥发,进而对锅炉、管道或设备受热面造成沾污结渣、腐蚀等危害。为系统了解碱金属迁移转化对生物质灰沾污结渣影响的研究并预测其发展趋势,首先,归纳生物质热化学转化过程中由碱金属迁移转化引发的安全问题及危害;其次,回顾和总结近年来国内外生物质灰沾污结渣机理方面的研究进展,主要包括不同热化学转化来源生物质灰沾污结渣演变规律和碱金属迁移转化特性研究等;最后,预测生物质灰沾污结渣防治研究的发展趋势。研究结果显示：生物质热化学转化过程中碱金属的赋存形式和演化特征是影响灰熔融和沾污结渣特性的重要因素,不同热化学转化来源生物质灰的熔融和烧结规律是灰沾污结渣防治研究的关键。以往针对碱金属迁移转化特性的研究,大多只考虑生物质自身的燃料性质、矿物组成等,对不同热化学转化过程中碱金属迁移转化对生物质灰沾污结渣和熔融烧结的影响以及不同形式碱金属成分的影响研究仍不够深入和系统,尚未形成完善的理论体系,这将成为以后的重点研究方向。     

锅炉受热面结焦事故分析

在锅炉运行中,锅炉受热面结焦(或称结渣)是比较普遍的现象,它与燃料中灰分的熔融特性、燃烧室及燃烧设备的结构特性、安装检修质量和运行调整等因素有关。尤其是烧劣质煤,更容易结焦,且往往导致停炉。由于除渣劳动条件恶劣,还容易发生事故。一、事故树分析1.事故树锅炉受热面结焦事故树见附图。     

锅炉结渣的生成机理及计算分析

综合概述燃煤锅炉结渣的生成机理及内外因素。并计算分析各项判别指标，提出了结渣的控制措施。     

An experimental study on the burning rate of a continuously released n-heptane spill fire on an open water surface

Spill fires are common during oil product storage and transportation after a loss of containment. Since the burning fuel is moving and the fuel depth is quite shallow, the burning rate in a spill fire is different from that of a pool fire with a static burning zone. Unlike pool fires, which have been studied for decades and have well-established correlations for burning rate, research on spill fires is inadequate. In this paper, continuously released n-heptane spill fire experiments were conducted on open water surfaces with varying fuel discharge rates. The pool diameters were measured, and the spill fire burning rates were estimated based on a dynamic balance between fuel supply and combustion. The burning rates in n-heptane pool fires from the literature were reviewed and compared with the estimated burning rates in spill fires of the same dimension. The spill fire burning rate was found to be close to that in a pool fire during the initial burning phase but lower than that in a bulk burning pool fire and that in a “fuel-level-controlled” pool fire. The distinction between the burning rates of spill fires and pool fires is explained by the heat balance analysis of the fuel layer. A model for the spill fire burning rate was proposed accordingly. The results calculated with the presented model are closer to the measured data than those calculated with pool fire models.     

航空煤油薄油层燃烧特性实验研究

为研究薄油层燃烧特性，开展航空煤油薄层油池火实验，分析油品燃烧的整个过程、燃烧速率、火焰高度和辐射反馈等参数随时间的变化规律。结果表明:整个薄层燃烧过程除发展、稳定和熄灭阶段外，还存在薄层燃烧衰减阶段。稳定阶段的燃烧速率与初始油层厚度相关，但随着厚度的增加其逐渐趋于稳定；薄层燃烧衰减阶段，燃烧速率会随着实时油层厚度的下降逐渐降低。对比火焰高度的实测值和模型预测值发现，Heskestad模型的预测更接近实际结果；燃烧发展阶段后，火焰辐射反馈基本维持稳定，受初始厚度的影响较小，但辐射透射强度会随着油层厚度的降低而增加，且增速逐渐加快，表明辐射透射在薄层燃烧衰退阶段中起到关键作用。结合辐射透射的变化规律，将辐射反馈分为可吸收和不可吸收2部分，并提出用于预测辐射透射大小的经验模型。     

庚烷池火多火源燃烧特性的实验研究

多火源燃烧是森林火灾和城市群发性火灾中重要而又特殊的火灾现象,相关研究很少。通过恒定控制液面高度的实验系统,对直径0.1m、0.2m和0.4m的庚烷池火在单个火源、两火源燃烧和三火源线性排列时的火焰高度、火焰体积和燃烧速率等特性进行了实验研究。研究发现,三火源燃烧时中间火源的火焰高度、火焰体积和燃烧速率明显高于两火源燃烧和单火源燃烧,三火源燃烧时边上火源与两火源的燃烧状况难以区分。这些燃烧特性随着火源间距的减小,呈现增大趋势。热量反馈增强和空气卷吸受限这两种火源相互作用机制相互耦合,且随着火源间距的减小而增强,在S/D（S为火源间距,D为油池直径）为2～4时,两种机制强烈竞争,在其他参数范围内热量反馈增强效应占主导作用。研究还发现火焰体积与热释放速率有较好的线性相关关系,单位火焰体积的热释放速率约为1614kW/m3。     

An experimental and modeling study of continuous liquid fuel spill fires on water

The spread of burning fuel spilled from oil product containers during offshore storage and transportation may cause large damage and trigger further accidents. Some analytical models already exist to predict the spread and burning behavior of liquid fuel spill fires, however, few experimental studies have been conducted to verify the model results. In this paper, continuous n-heptane spill fire experiments were conducted in a rectangular trench covered with water. The burning area, fuel spread rate, and thermal flux with different discharge flow rates and ignition delay times were investigated by both experimental and modeling means. The spill fire burning area, with 5 typical phases during burning, has a quasi-steady value which is directly proportional to the discharge rate but irrelevant to the ignition delay times. The steady burning rate, as the ratio of discharge rate over burning area, was estimated. A spread model was modified to simulate the spread of continuous liquid fuel spill fires in a one-dimensional channel, based on the balance between gravity and viscous forces. A cuboid solid flame model was used to compute the thermal flux from spill fires. The burning fuel spread and the heat flux calculated by the models agree with the experimental results.     

基于GSI原理瓦斯抽采钻孔收缩比评估方法及其应用

瓦斯抽采钻孔收缩是致使排渣阻力增大、钻孔发生堵塞的主要因素。基于地质强度指标(GSI)法,分析了评估煤体力学参数的方法,探讨了Mohr-Coulomb与Hoek-Brown准则内在关系,从而能够应用较为广泛的方法验证和求解不同煤层条件下钻孔的变形量;提出了钻孔收缩比概念和计算方法,应用GSI原理对不同强度煤的钻孔收缩比进行定性分析。分析结果表明,钻孔收缩比受煤体强度变化的影响非常敏感,对于强度较低的煤体,钻孔变形量大,钻孔收缩严重,其结果缩小了钻孔的排渣空间,间接增大了钻屑运移、钻杆旋转及退钻阻力,使钻孔施工更加困难。结合工程案例,根据施工地点地质条件,科学评估钻孔收缩比并提出钻孔施工改进方案,通过工业性试验,钻进深度提高40%,钻进效率提高97.5%。     

计划烧除的应用与研究

火作为一个重要的生态因子影响着生态系统的平衡。林火生态是计划烧除的理论基础,讨论作广科学家应用于营林,生态系统的保护和野动物的保护等方面。文中还对林地计划火烧的间隔期和计划划烧除的效果与评价作了阐述,并讨论了计划烧除在应用在存在的问题。     

突然进风对室内火灾影响的实验研究

以工业酒精为燃料，在一房间与走廊相联的模型中，研究了封闭燃烧一定时间后，突然进风对室内火灾的影响。分别在走廊进风。起火室进风等情况下，观察了燃烧状况的变化，测量了典型截面的温度分布，并对一些现象出现的原因作了分析。指出这种突然进风，可在短时间、一定范围内降低温度，但主要效果是促进燃烧。当室内有明火源时还会引发烟气回燃，致使其中的温度急剧升高。     

多因素下小尺度油罐火燃烧速率的研究

以正庚烷为研究对象,开展了不同因素耦合作用下小尺度油罐火燃烧特性的实验研究。结果表明:在不改变其他工况条件下,开口因子直接影响燃料燃烧速率,发现不同开口因子下燃烧速率与全开口下燃烧速率之比始终正比于对应的开口面积之比,且之间存在着相应的关系式。在实验所测两种液位6cm和8cm下,其燃烧速率变化不大,由此可发现,在该实验液位下油罐火液位高度不是影响燃烧速率的主要因素。在不同的风速下,随着风速的增加燃烧速率逐渐增加并趋于一定值,且不同开口因子下风速对燃烧速率的影响程度不同。风速对开口因子大的油罐燃烧速率的影响小于开口因子较小的油罐。     

On the determination of the laminar burning velocity from closed vessel gas explosions

A methodology to determine the laminar burning velocity from closed vessel gas explosions is explored. Unlike other methods which have been used to measure burning velocities from closed vessel explosions, this approach belongs to the category which does not involve observation of a rapidly moving flame front. Only the pressure–time curve is required as experimental input. To verify the methodology, initially quiescent methane–air mixtures were ignited in a 20-l explosion sphere and the equivalence ratio was varied from 0.67 to 1.36. The behavior of the pressure in the vessel was measured as a function of time and two integral balance models, namely, the thin-flame and the three-zone model, were fitted to determine the laminar burning velocity. Data on the laminar burning velocity as a function of equivalence ratio, pressure and temperature, measured by a variety of other methods have been collected from the literature to enable a comparison. Empirical correlations for the effect of pressure and temperature on the laminar burning velocity have been reviewed and two were selected to be used in conjunction with the thin-flame model. For the three-zone model, a set of coupled correlations has been derived to describe the effect of pressure and temperature on the laminar burning velocity and the laminar flame thickness. Our laminar burning velocities are seen to fall within the band of data from the period 1953–2003. A comparison with recent data from the period 1994–2003 shows that our results are 5–10% higher than the laminar burning velocities which are currently believed to be the correct ones for methane–air mixtures. Based on this observation it is concluded that the methodology described in this work should only be used under circumstances where more accurate methods can not be applied.