论文总字数：27665字

摘 要

随着中国乃至世界能源局势的紧张化，褐煤的价值以及其运用和加工逐渐得到重视，已经成为我国主要使用的煤种。作为循环流化床锅炉的常用煤种之一，研究褐煤的成灰特性对循环流化床锅炉的设计和运行具有重要意义。

通过查阅大量的相关文献，本文对煤成灰特性的试验研究方法进行了归纳总结。现今研究，主要采用静态燃烧与冷态振筛磨耗结合或者静态燃烧与冷态流化床磨耗结合的方法来研究煤的成灰特性。其中，静态燃烧与冷态振筛磨耗结合的方法因其操作简单，数据可靠等优点成为试验研究煤成灰特性的较佳选择。

本文以云南褐煤作为试验煤样，通过工业分析，热重实验和成灰特性试验对云南褐煤的成灰特性进行了分析。同时，由于国际上对煤成灰特性并没有明确的标准，本文创新性地引入流化床常用淮北烟煤的成灰特性进行数据对比。

试验结果表明,云南褐煤的挥发份含量高，灰分含量低，其水分含量较高，但是低位发热量也较高；其着火温度比淮北烟煤低，燃尽时间比淮北烟煤短，在燃烧过程中更容易着火和燃尽。

不同粒径范围的云南褐煤煤样在静态燃烧试验和冷态振筛磨耗试验后产生的煤灰颗粒偏细，细颗粒（≤100μm）质量分数占30%以上，甚至在细粒径原煤成灰试验中，细灰颗粒的质量分数在60%以上，大幅度高于淮北烟煤。这说明云南褐煤在循环流化床锅炉的运行条件下，较淮北烟煤更容易发生破碎和磨耗，形成粒径更小的灰颗粒。

云南褐煤原煤粒径较细煤样的成灰特性与原煤粒径较粗煤样的成灰特性相似，而淮北烟煤原煤粒径较细煤样的成灰特性与原煤粒径较粗煤样的成灰特性有明显差别，这可能是由于云南褐煤中矸石含量少，而淮北烟煤中所含矸石含量较多，成灰粒径大小与原煤所含矸石粒径大小有关。

各档云南褐煤成灰的等比表面积平均当量直径均小于100μm，其中最小粒径原煤的成灰等比表面积平均当量直径为45.6μm，最大粒径原煤成灰等比表面积平均当量直径为82.1μm。而各档淮北烟煤灰的等比表面积平均当量直径均大于100μm。

云南褐煤发热量高，燃烧磨耗后产生的煤灰质量少、粒径小，会降低旋风分离器的分离效率，进而降低物料的循环倍率，最终可能导致锅炉密相区超温和出力不足等现象，可从提高旋风分离效率，添加辅助床料和采用飞灰回燃技术等方面进行改进。

关键词： 褐煤；淮北烟煤；循环流化床；成灰特性；燃烧特性

Abstract

Because of the shortage of energy in China and all over the world, more and more people pay attention to the value, application and processing of lignite, and the lignite has becomes the main type of coal used in china. As one of the common types of fuel used in CFB boilers, it is important to study the ash formation characters of lignite, which makes great sense in the designing and operation of CFB.

By the investigation of a large number of relevant literatures, the experimental methods of studying the ash formation characters of coal are summarized as follows. There are two main methods, one is coal static combustion combined with ash cold sieving method and another is coal static combustion combined with ash cold fluidizing method. Coal static combustion combined with ash cold sieving is the better one as it is easy and reliable.

Taking Yunnan lignite as an experimental sample, the paper used the proximate analysis, thermogravimetric analysis and coal static combustion combined with ash cold sieving method to find out the combustion and ash formation characters of Yunnan Lignite. At the same time, as there is no clear international standard of ash formation characters of coal, the paper also creatively use the data of ash formation characters of widely used Huaibei bitumite to be a contrast.

The result shows that Yunnan lignite has high volatile matter, low ash content, high water content and high lower heating value. The ignition temperature of Yunnan lignite is lower than Huaibei bitumite and the burnout-time of Yunnan lignite is shorter than Yunnan lignite. It shows that Yunnan lignite is easier to catch fire and burn out.

After coal static combustion combined with ash cold sieving, the ash of different size of Yunnan lignite is fine. The mass fraction of fine ash (100μm or less) is over 30%.In the experiment of fine raw lignite, the mass fraction of fine ash is even over 60%, which is drastically higher than Huaibei bitumite. Compared with Huaibei bitumite, Yunnan lignite is easier to be broken and form finer ash under the condition of CFB.

The ash formation characters of fine samples of Yunnan lignite are similar to the ash formation characters of coarse samples of Yunnan lignite，while there are different of Huaibei bitumite. The reason may be that the gangue content of Yunnan lignite is less than that of Huaibei bitumite. The particle size of ash is relevant to the size of the gangue in raw coal.

The equivalent specific surface diameter of all Yunnan lignite ash samples is less than 100μm. The minimum one is 45.6μm and the maximal one is 82.1μm. On the contrary, equivalent specific surface diameter of all Huaibei bitumite ash samples is more than 100μm.

Yunnan lignite has high lower heating value, low ash content and the size of ash is fine，which may reduce the efficiency of cyclone separator and then reduce the circulation factor of bed materiel. Finally it may cause the overheating of dense phase and decrease the output of boilers. To solve the problem, the efficiency of cyclone separator could be improved, assisted bed material could be added and the method of fly ash recirculation could be used.

KEY WORDS: Lignite; Huaibei bitumite; CFB; Characters of ash formation; Characters of combustion.

目 录

第一章 绪 论 1

1.1 引言 1

1.2 煤的成灰特性试验研究现状 3

1.3 研究煤成灰特性的常用方法 4

1.4 本文的研究目的和主要研究内容 5

第二章 试验设备与方法 7

2.1 试验煤种 7

2.2 热重试验 7

2.3 成灰特性试验 7

第三章 热重试验 9

3.1 热重试验装置 9

3.2 燃烧特性分析 9

第四章 成灰特性试验 12

4.1 成灰特性试验流程 12

4.2 静态燃烧试验结果分析 12

4.3 冷态振筛试验结果分析 14

4.4 分析与小结 27

第五章 总 结 28

致 谢 30

参考文献(References) 31

第一章 绪 论

1.1 引言

循环流化床锅炉最主要的特征是有一定量的床料在物料循环系统中进行循环，它们既是循环介质，也是气-固反应的参与者。因此，床料的品质对于循环流化床锅炉的流化特性和锅炉整体性能有十分重要的影响。其中，物料循环倍率和床内颗粒的粒径分布等参数对于流化床的运行尤为重要，因为其对燃烧效率和脱硫效率都会产生影响。对于给定任意床存量（主要指炉膛内的总压降），床内颗粒的粒径分布将影响到锅炉的分离器分离效率、循环倍率、炉膛传热特性和热负荷分布等。

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