【作者】 赵鹏；

【导师】 卢啸风；

【作者基本信息】 重庆大学 ， 动力工程及工程热物理， 2011， 硕士

【摘要】 鉴于我国目前仍是以煤炭为主的能源结构,以及煤质逐渐变差的新形势,上世纪80年代初兴起的循环流化床锅炉(简称CFB)燃烧技术在国内得到了迅速的发展。我国已是CFB装机数量和装机总容量最大的国家,目前已投运的300MWCFB机组近30台,首台世界上最大的600MW超临界CFB电厂目前也在紧张施工中。在煤质逐渐变差的大背景下,尤其是随着CFB的大型化,底渣的有效冷却和底渣中细颗粒的回炉就显得特别重要。担当这一重任的传统冷渣器在业界的表现不能令人满意,可以说,几乎所的CFB都或多或少地存在冷渣器运行不良的现象。在吸收各种传统冷渣器优点的基础上,笔者所在研究室研制了一种新型的混流式流化床冷渣器,并获得了国家发明专利。该专利产品已在150MW和300MWCFB机组上投运,总体上运行效果良好,但仍有必要对颗粒分选和回灰进行深入研究,笔者在一半工业可视化试验台上对该冷渣器的气固流动特性进行了系统的试验。试验床料采用四川白马300MWCFB示范电厂锅炉滚筒冷渣器排出的底渣。首先对两个仓室的空板阻力进行了验证;其次,通过流化特性曲线确定了临界流化风速,对分选仓在不同风速和不同隔墙高度下的分选和返料特性、鼓泡仓在不同风速、不同静止床高和不同时间段的返料特性、两仓同时运行时的返料特性进行了试验研究;接着,对返料回灰对炉内床料粒径分布的影响进行了计算和分析;最后又对该冷渣器的工业应用情况进行了简要的分析。试验及分析结果如下:①经验证,试验台设计合理,能够达到试验要求;②分选仓的分选效率和分级分选效率均随流化风速的增加而增大,随隔墙的增高而减小。700mm隔墙、分选风速为5m/s时的分选效率最佳——可达50%(理想值为70%),1mm以下颗粒的分级分选效率均大于60%;③分选仓的分选速率随分选风速增大而增大,且分选风速大于4m/s时,分选速率随隔墙增高而减小。700mm隔墙、分选风速5m/s时的分选速率最佳——达4.5t/h,分选至鼓泡仓的颗粒90%以上为小于4mm的细颗粒,有利于鼓泡仓的微鼓泡运行;④分选仓的返料量(返料速率)和鼓泡仓的返料量均流化风速的增大而增大;分选仓的返料量随隔墙增高而降低;鼓泡仓返料量随静止床高的增高而增大,在4min～12min间随试验时间的延长而明显增大;两仓单独运行时,分选仓的返料速率更大;⑤分选仓和鼓泡仓的返料粒径绝大部分都在循环流化床锅炉外循环灰的粒径范围内(0～0.38mm),而且分选仓的返料相对而言更细一些,90%以上在0.15mm以下;也正因为此,两仓同时运行时的返料粒径分布更倾向于分选仓的;⑥采用混流式流化床冷渣器,返料能够在短时间能扭转细颗粒逐渐减少的趋势,对炉膛内细颗粒份额有显著的改善作用;⑦混流式流化床冷渣器的工业应用表明:该冷渣器分选效果良好,并能够有效地避免冷渣过程中引起的堵塞、结焦问题,对底渣粒径的适应性比传统流化床冷渣器更强。更多还原

【Abstract】 In consideration of the coal account for the majority of energy structure in our country at present, and new state of coal quality becoming worse and worse, the circulating fluidization bed boiler (short title CFB) combustion technology which derived from the 80s last century have had a rapid expansion in China. Our country is the maximum state for CFB install and total capacity, with about 30 CFB units for 300MW put into operation, the first maximum supercritical 600MWCFB in process of constructing Baima model plant in Sichuan province. Under the background of coal quality getting worse and worse, especially, along with large-scale CFB, effective boiler bottom ash cooling and fine ash recovery become very important. Traditional ash cooler can do the things, but they can’t be satisfactory frequently, so to speak, almost all the CFB have undesirable operating conditions more or less. On the base of absorbing multitudinous merit of traditional fluidized bed ash cooler, Clean Coal Combustion Technology Laboratory develops a kind of mixed-fluid fluidized bed ash cooler, and has obtained state inventive patent. This product has been put into operation on 150CFB and 300MWCFB units, and the effect was very well as a whole. However, it’s necessary to do some research about particle separation and fine ash recovery. The author did series test on a semi-industrial visual test-bed.The author adopted as test materials boiler bottom ash out of rotary ash cooler running in Baima 300MW plant. Primarily, test and verify bare board resistance of two cabins; then, confirm the critical fluidized air velocity, get through fluidization characteristics curve, do plentiful test study, such as, separation and returning materials character in different air velocity and different partition height of sorted cabin, returning materials character in different air velocity, different static state bed height and different test time of bubble cabin, and returning materials character when two cabins are running at the same time; besides, counter returning materials react on the particle size distribution of furnace, apply mathematical model to make some calculation and analysis; at last, make brief analysis for mixed-flow fluidized bed bottom ash industrial application. The test results and analysis are as follows:①Through checking, the test-bed design was reasonable, and could reach all the test demands;②Both efficiency of separation and scale efficiency of separation of sorting cabin increased with air velocity, but decreased with partition height rise. At 700mm partition and 5m/s air velocity, efficiency of separation is the best and reached to 50%(ideal value is 70%), and scale efficiency of separation of particle under 1mm more than 60%;③Sorting rate of sorting cabin magnified with air velocity improvement, and when air velocity exceeded to 4m/s, it decreased with partition height rise. Similarly, at 700mm partition and 5m/s air velocity, Sorting rate is the best and reached to 4.5t/h; in sorting cabin, more than 90% particle were less than 4mm, which was good for micro-bubbling;④The returning material quantity of two cabins increased with air velocity increase; the returning material quantity of sorting cabin decreased with partition height rise; the returning material quantity of bubbling cabin increased with static bed-height rise, and sharply increased within 4th minutes to 12th minutes; when the two cabins were running simultaneously, the returning material rate of sorting cabin became greater;⑤Two cabins’returning material size distribution were in the range of circulating ash of boiler(0～0.38mm). What’s more, the returning material of sorting cabin was more fine relatively speaking, more than 90% under 0.15mm; for this, two cabins running simultaneously, the returning material size distribution was close to sorting cabin;⑥Adopting mixed-fluid fluidized bed ash cooler, returning material could reverse fine particle decreasing tendency in furnace in short time, which had an prominent improvement on the fine particle in furnace;⑦Industrial application of mixed-flow fluidized bed ash cooler indicated that: the ash cooler sorted effect is favorable ,could effectively avoid ash cooler cooking, blocking and other common troubles, it has much stronger adaptability to big bottom ash compared with traditional fluidized bed ash cooler.更多还原