【作者】 昝军；

【导师】 赵云胜；

【作者基本信息】 中国地质大学 ， 安全技术及工程， 2010， 博士

【摘要】 近年来,我国水泥行业发展迅速,是我国国民经济发展的重要组成部分。2008年,全国共有水泥企业4350家,水泥产能18.7亿吨,分布在31个省区市。河北、山东、湖北等省我国水泥生产大省,仅湖北省一年的水泥生产产量比美国一个国家的水泥产量都高。其中新型干法水泥生产线1018条,产能约11亿吨,落后水泥产能约5亿吨,其余为水泥粉磨站和其它类型回转窑。新型干法水泥生产线水泥回转窑的窑头、窑尾是水泥厂最大的粉尘污染源,窑头、窑尾废气总量约占全厂废气总量的60%左右。其中水泥熟料生产中粉尘,粉碎、研磨、过筛、配料出窑、包装等工序都有大量粉尘产生。通常,熟料中游离二氧化硅含量约1.7-9.0%,成品水泥含1.2-2.6%。人体长期吸入烧成后的熟料或水泥粉尘可引起水泥尘肺。水泥遇水或汗液,能生成氢氧化钙等碱性物质,刺激皮肤引起皮炎,进入眼内引起结膜炎、角膜炎。而回转窑窑头等作业地带,更有高温、热辐射等危害。湖北省华新水泥厂具有新型干法水泥生产线21条,生产工艺和技术在国内具有领先水平,笔者对湖北省两大水泥生产企业华新水泥厂和葛洲坝水泥厂进行了现场调研,在调研中发现,熟料生产线的窑头烟尘污染以及窑尾的大烟囱废气排放是水泥厂目前生产中主要职业危害和环境问题。窑头烟尘污染主要来至于固定窑头与旋转窑筒体之间的窑头,因此论文以新型干法水泥窑窑头烟尘控制技术研究为选题,以华新水泥厂4.75米窑为实例研究对象,在窑头烟尘动力特性分析、水泥窑窑头控尘重力沉降室导流板、窑头烟尘控制通风系统等方面进行了研究。研究的主要内容如下：第一章绪论。介绍了水泥窑的发展阶段及新型干法水泥旋窑的生产工艺,结合对华新水泥厂和葛洲坝水泥厂的现场调研,论述了我国目前干法水泥窑头职业卫生现状和国内外关于水泥生产的环保的要求,提出了课题研究的重要意义。综述了国内外关于干法水泥旋窑窑头密封技术的研究现状,提出了当前我国窑头密封存在的主要问题,并以华新4.75米窑窑头为研究实例,以葛洲坝3.5窑窑头密封为类比研究对象,研究其烟尘控制技术的理论和方法,力求更完善的解决长期以来困扰窑头密封处烟尘泄漏扩散这一关键技术问题,有效改善窑头的职业卫生现状。最后,介绍了论文的主要研究内容、创新点、研究方法和技术路线。第二章水泥窑窑头烟尘动力特性分析研究。对粉尘除尘机理和除尘设施设备进行了概述。讨论了烟尘粒径的定义、烟尘粒径分布即分散度的概念及罗率-拉姆勒粒径分布函数。对窑头烟尘颗粒的受力状况进行了分析,建立了环形通道沉降室沉降模型,该模型将沉降室分为4个区域,考虑了布朗扩散作用、湍流扩散作用、重力沉降重力和湍流泳力四种作用形式。通过量纲分析,得到了不同直径大小的颗粒在环形通道中的壁以及底处的沉降规律,并进一步得到了顶面沉降速度与壁面、地面沉降速度的关系。得到以下结论：颗粒在壁面上的的量纲-沉降速度随粒径的增大先减小后增大最后趋于一个定值,并且随着通风流量的增大而增大,在底面的量纲-沉降速度随粒径的增大先减小后增大,并且通风流量对其影响较小；顶面的沉降速度公式：(?)第三章水泥窑窑头控尘重力沉降室导流板研究。首先对重力沉降室导流板进行了初步设计,包括沉降室尺寸与结构。讨论了导流板的计算模型包括计算区域、边界条件、控制方程、数学模型以及其传热规律。以华新4.75米窑为实例,以圆形导流板作为典型算例进行研究,在抽风压力-70kPa条件下,通过数值分析可知,抽风压力没有对窑体内压力场产生影响,没有影响窑内正常通风状况,密封罩内气流稳定,不会在系统内产生“漩涡”,不易造成粒子在“漩涡”内发生粉尘堆积；小于50um的颗粒被直接抽走。通过对3.5米窑的对比分析可知,风压压力梯度变化不大,但由于沉降距离变小,在沉降长度不变的情况下,抽风口颗粒直径大,说明沉降效果不理想,且易于在抽风口形成“漩涡”,不易将颗粒带走,说明小直径窑可不设置导流板来增加沉降效果。通过数值分析,得到如下结论：1、沉降室在采用圆形导流板时,随着抽风压力的提高,小颗粒被抽走,大颗粒在沉降室沉降比例得到提高,但抽风压力过大,电耗增加,抽风压力可在-70kPa-50kPa之间。2、研究了三种导流板结构形式,即椭圆(a)导流板、椭圆(b)和圆形导流板三种形式的导流板的沉降效果。通过抽风口出颗粒直径分布及溜灰口处颗粒直径分布可知,沉降室沉降室能力为椭圆(a)导流板<圆形导流板<椭圆(b)导流板。3、研究了三种导流板纵截面结构即直筒型(Ⅰ)、扩张型(Ⅱ)、收缩型(Ⅲ)的沉降效果,通过比较其内部静压分布、气体密度分布、气体x方向速度分布、z方向速度分布、抽风口出颗粒直径分布等,可知：纵截面导流板沉降能力排力规律为：收缩型(Ⅲ)>扩张型(Ⅱ)>直筒型(1)。第四章窑头烟尘控制通风系统研究。论文通过窑头烟尘的沉降规律以及重力沉降室导流板研究,可以将烟尘中的大颗粒实现一次降尘。但对于50um以下的颗粒必须通过二次收尘来解决。根据密封式控尘装置的特点,可以考虑采用空气幕隔尘或单向气流抽风除尘两种方案。由于高温差环境的影响,空气幕隔尘所需动力远远大于目前窑头的吹吸式降温除尘,同时也大于在后面讨论的抽吸式除尘动力。因此以抽吸式控尘进行了详尽系统的研究。针对抽吸式控尘,首先探讨了控尘方案和原理,系统研究了其数值计算,主要包括模型的建立及简化、网格生成与优化、紊流模型的选择、边界条件与初始条件的选择、控制方程的选用。对不同抽风口个数(1、2、4、6、8)和压力分布进行了数值分析和对比研究,以6个抽风口进行了通风系统的完整设计,并充分考虑了抽吸效果、水泥积灰和流场压力与速度分布。1、从流场速度分布上：1)、当有两个抽风口时,即使在压力达到1000Pa时,仍然有很大一部分圆弧环面向外漏风。2)、当有四个抽风口,每个抽风口负压均为800Pa或900Pa时,基本达到控尘效果。3)、当有六个抽风口,每个抽风口负压力为400Pa时,最小进风速度为2.8m/s,速度分布均匀,因此抽风口负压力为400Pa,可以作为一个转折点,即若选择六个出风口,就能达到控尘要求。4)、当有八个抽风口,每个抽风口负压力为300Pa时,最小进风速度为2m/s,速度分布均匀,速度分布从2.0m/s至4.6m/s,这就是当有八个抽风口时,开始满足要求的转折点。即只要抽风口负压力值大于等于300Pa,就一定能控尘。2、从抽风口总的质量流量上：六个风口的风口负压为350Pa,速度分布范围是1.8m/s到5m/s。八个风口的风口负压为300Pa时,速度分布范围是2.0m/s到4.6m/s,即六个风口的风口负压为350Pa时,与八个风口的风口负压为300Pa时,抽风效果相当,都保证小缝隙环面处有2m/s的进风速度。但是采用六个风口时的风口出流质量为3.87kg/s,采用八个风口时的风口出流质量为4.74kg/s，几乎少了1 kg/s,所以,建议采用六个风口的方案。3、六个抽风口通风系统的设计从负压室三维流场的角度确定了使用六个抽风口时风机最佳位置、各抽风口的分布、管径、角度和连接方式。更多还原

【Abstract】 In recent years, cement industry has been developed quickly in our country as an important part of national economy. In 2008, there are totally 4350 cement enterprises distributed in 31 provinces/districts/cities with the cement capacity of 18.7 hundreds million tons. Hebei, Shandong and Hubei have the most cement capacity and Hubei province’annual output of cement is larger than that of the whole America. There are 1018 production lines of new type of new dry cement with the cement capacity of 11 hundreds million tons and the lagging cement capacity of 5 hundreds million tons. Others are cement grinding stations and other types of rotary kilns. The kiln head and kiln rear on the new dry cement product lines are the biggest dust pollution source, which can produce 60% of exhaust gas of the total amount. In the process of cement clinker, a lot of dust is produced in the workstage of cmminution, grinding,subsize,burdening,out kiln and pack. Usually, the free silica content is about 1.7-9.0% in clinker, and 1.2-2.6% in finished cement. Long-time inhalation of clinker or cement dust for human body can cause cement pneumonoconiosis. Meeting with water or sweat,cement can generate alkalinity matter such as calcium hydroxide etc., which can irritate skin, causing dermatitis and conjunctivitis and keratitis after entering into eye. In the work area of rotary kiln head,there are hazards such as high temperature and thermal radiation. Hubei Huaxin Cement factory has 21 new type of dry cement produce lines, whose industrial art and technique is in the lead in our country. The writer conducted site survey in Hubei Huaxin Cement factory and Gezhouba Cement factory, finding out that the smoke and dust pollution at clinker kiln head and waste gas emission from the smokestack in kiln end are the main occupational hazard and environment problem. The smoke and dust pollution at clinker kiln head mainly comes from the kiln mouth between the fixed kiln head and rotary cylindrical shell. Therefore, this paper chose smoke and dust control technique for new type of dry-process rotary kilns as a subject, the 4.75 m kiln of Huaxin Cement factory as case study, doing the research in aspects of kiln mouth smoke dynamic characteristics analysis, kiln mouth dust control gravity settling room guidevane, smoke and dust control ventilation system etc.. The main components are followed:Chapter One Introduction. The cement kiln develop stage and new dry cement rotary kiln industrial art were introduced. Combination with the site survey result in Huaxin Cement factory and Gezhouba Cement factory, the current occupational health status in dry cement kiln head of our country and environment protection requests about cement product at home and abroad were discussed, putting forward the essential meaning of this subject. The research status of dry cement rotary kiln mouth seal technique was reviewed, raising the main existed problems of kiln mouth seal. This paper studied on the smoke and dust control theory and measure taking Huaxing 4.74m kiln mouth as a research example and Gezhouba 3.5m kiln mouth as an analogy example, so as to resolve the key technical problem of smoke and dust drain diffusion from kiln mouth seal, to improve occupational health status effectively. At last, the main study content, innovation, research method and technical route.Chapter Two cement kiln mouth smoke and dust dynamic characteristics analysis research. Dust removal mechanism and dust collection device were summarized and Grain diameter definition, particle size distribution(that is degreeofdispersion) concept and Rosin-Rammler particle size distribution foundation were discussed. Kiln mouth smoke granule stress condition was analyzed. The sedimentation model of ringlike passage settle room was established, which divided the settling room into 4 parts, considering the effect of Brown diffusion,turbulence diffusion, gravity settling gravity and turbulent flow throwing power. Based on dimensional analysis, the settling discipline was obtained that showed how different diameter granule settled on the circle passage wall and at the bottom, and further more, the relationship between the top surface settling speed and wall, ground settling speed. The conclusion is that the along with the increase of grain diameter, the granule dimension-settling speed on the wall will decrease and then increase towards to a definite value, and it will increase with the ventilation flow rate increment; at the bottom, along with the increase of grain diameter, the granule dimension-settling speed on the wall will increase and then decrease with less effect of flow rate; the top surface settling speed formula is: (?)Chapter Three cement kiln mouth dust control gravity settling room deflector study. First, gravity settling room deflector was designed initially, including selling room size and structure. The calculation model of deflector was discussed containing calculation area, boundary condition, control formula, mathematical model and its heat transfer rule. Taking Huaxin 4.75m kiln as an example and circle air deflector as a typical numerical example, thorough numeric calculation, it showed that in the condition of air extracting pressure-70kPa, the air extracting pressure doesn’t have effect on the inner kiln pressure space, neither on the normal ventilation, the air flow in the seal cover is stable and it will not cause vortex, neither cause dust accumulation in the vortex. The granule with diameter less than 50um will be drawn out. Contrasted with 3.5m kiln, it can be known that wind pressure gradient changes rarely, but because the settling distance minifies, under the condition of settling length unchangeable, the grain diameter is great, which shows that the settling effect is unsatisfactory, and vortex can be formed easily at the air extracting tuyere, thus it can’t take grains away, stating that small diameter kiln without air deflector has good settling effect. Though numerical analysis, the following conclusions can be achieved.1.when using circle air deflector in settling room, with the increase of air draft pressure, small granules are taken out, the big granules settling rate increases. However, when the draw pressure is too high, the current drain will raise. So the pressure should be between-70kPa to 50kPa.2.Studied on three types of air deflector settling effect, that is ellipse(a)deflector, ellipse(b)deflector and round deflector. Through the grain diameter distribution at air draft and dust down spouting, it can be known that the settling ability is ellipse(a)deflector<round deflector <ellipse(b)deflector.3.Researched on three types of deflector longitudinal section structure settling effect, that is straight trunk type (Ⅰ) expanding type (Ⅱ) and shrinkage type (Ⅲ).Though comparing its inner static pressure distribution, gas density distribution, gas x direction speed distribution, z direction speed distribution and grain diameter distribution at air draft exit, it shows that the rule of deflector longitudinal section settling ability is shrinkage type (Ⅲ)> expanding type (Ⅱ) straight trunk type (Ⅰ)Chapter Four studied on the ventilation system of dust control. Through the research on the dust settling rules and gravity settling room deflector, big granules can be settled at a time,but the grains with diameter 50um must be collected twice. According to the features of sealed dust control device, it can use curtain to separate dust or unidirectional air flow to draw dust. Considering the effect of high temperature difference, using air curtain needs much more power than using kiln mouth push-pull type to remove dust at current and drawing-in type which would be mentioned later. So this chapter researched on the drawing-in type in detail, including the dust control program and principle, it numeric calculation, which contained the model building and simplify, grids form and optimization, turbulent flow model choosing, boundary condition and initial condition choice and control formula selecting. Then,this chapter studied on the numerical analysis and contrast of different air draft opening number (1、2、4、6、8) and pressure distribution. The whole ventilation system with 6 air draft opening was designed, based on sufficient considering of drawing-in effect, cement dust stratification, flow filed pressure and speed distribution.1.Flow filed speed distribution1)When there are two drawing openings, air till leak from most part of circular arc side even the pressure reaches 1000Pa.2) When there are four drawing openings, the dust control effect can be guaranteed when every drawing opening negative pressure is 800Pa 900Pa.3)When there are six drawing openings, every drawing opening negative pressure is 400Pa, the minimum intake air speed is 2.8m/s,and the speed distribution is balance. So the drawing opening negative pressure 400Pa can be a turning point, that is there are six drawing openings, the dust control requirement can be achieved.4)When there are eight drawing openings, every drawing opening negative pressure is 300Pa, the minimum intake air speed is 2m/s, and the speed distribution is balance which is from 2.0m/s to 4.6m/s. This is a turning point to reach the requirement. As long as the drawing opening negative pressure is not less than 300Pa, dust can be controlled.2.Drawing opening total quality of flowThe opening negative pressure is 350Pa when there are six drawing openings and the speed is from 1.8m/s to 5m/s. The opening negative pressure is 300Pa when there are eight drawing openings and the speed is from 2.8m/s to 4.6m/s. That is to say, the drawing effect is the same when using six drawing openings with the pressure of 350Pa and when using eight drawing openings with the pressure of 300Pa and can assure 2m/s intake air speed at the gap. While the quality of flow is 3.87kg/s when using six drawing openings and 4.74kg/s when using eight, less almost 1kg/s. So using six air openings is suggested.3.Ventilation system design using six drawing openings Based on three-dimensional flow field of negative pressure room, fan’s best site, air openings distribution, pipe diameter, angle and connection type are determined when using six drawing openings.更多还原