褐煤高温烟气顺流床干燥过程研究

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摘要

随着经济的高速发展，石油、天然气及煤炭等传统能源日益枯竭，能源价格

居高不下，低品质能源褐煤的综合利用与开发势在必行。我国褐煤资源丰富，但

由于我国褐煤“三高两低”（高水分、高灰分、高含氧、低热值、低灰熔点）的

特点，限制了褐煤的综合利用。因此，有必要对褐煤进行脱水提质处理，扩大褐

煤的综合利用途径，提高褐煤的市场竞争力。

本文首先介绍了我国褐煤的资源概况、特点及其利用情况，并充分阐述了国

内外褐煤脱水提质技术的应用现状及其发展趋势。初步分析了振动床顺流高温热

气流干燥技术的可行性。本论文并结合干燥实验和数学模拟研究了高温烟气下褐

煤干燥过程。

利用自制褐煤脱水提质实验台开展实验研究，重点考察干燥介质（氮气）初

始温度、褐煤颗粒粒径大小以及停留时间三要素对干燥效果的影响。同时开展正

交试验，采用多指标综合平衡法对实验结果加以分析，实验结果表明：停留时间、

初始烟温及粒径大小对干燥效果都有较大影响，其中停留时间和干燥介质初始温

度对水分脱除以及挥发分残留的影响较大，在实际应用中应着重考虑。

本文基于 McIntosh 提出的干壳/收缩的湿芯模型，建立了一维球坐标系下的干/

湿蒸发界面数学模型，采用了有限体积法和 Crank-Nicolson 六点差分格式对模型方

程进行离散化处理，同时结合 Matlab 语言对模型方程进行编程求解，模拟得到不

同工况下，单颗粒褐煤含湿量及其内部温度分布的动态变化。模型计算结果与实

验结果对比表明，两者吻合程度较好，模型结果基本上反映了褐煤干燥过程中温

度以及含湿量的变化趋势，说明本文建立的干燥模型可以较好地反映褐煤干燥的

实际过程。

本文利用所建模型对实验中难以测得的颗粒含湿量随时间的变化情况进行定

量分析，从而进一步考察各因素对褐煤脱水提质过程的影响，结果表明：

1不同介质初始温度下，褐煤脱水量和颗粒温度随时间的变化有所不同，介

质初始温度越高，褐煤颗粒升温及脱水速度越快；

2随着褐煤粒径及其初始含湿量的增加，褐煤颗粒升温速率以及水分脱除速

率均有所降低；

3研究发现：20mm 的褐煤颗粒在初始温度为 600℃的热气流下仅需停留 156s，

颗粒含水量即可降到 12% 以下，同时热值可提升 3767.4kJ/kg ，达到

20.51MJ/kg。

关键词：褐煤脱水提质传热传质干燥过程数学模型

ABSTRACT

With the rapid economical development, the traditional energy resources, such as

oil, natural gas, and coal, are being exhausted. Because of the ever-rising cost of

energy, people began to pay more attention to low-quality lignite resources. There is

lots of lignite in China. However, Chinese lignite is characteristic of high moisture

content, highash yield, highoxygen content, low heating value and low ash-melting

point. So the lignite utilization is restricted. Therefore, lignite dewatering is very

necessary to expand its application field and impove its market competitiveness.

The properties and the utilizations of Chinese lignite are firstly introduced in this

thesis. Then, the dewatering/upgrading technologies for lignite were introduced in

detail and the prospects and development trends of lignite upgrading were also

discussed. The feasibility of the technology of the downstream vibrated bed dryer for

lignite dewatering with hot temperature flue gas is preliminarily analyzed. The lignite

drying process was investigated in the thesis using experimental research and

numerical simulation.

A self-designed experimental appatus for lignite dewatering with high

temperature drying medium (nitrogen) was used to the effects of the original gas

temperature, lignite particle size and residence time on the lignite drying process.

Orthogonal experiment was designed and carried out to accomplish the experimental

purpose. The results shows that thelignite particle drying is influenced greatly by

combined factors of initial gas temperature, particle size and resident time. Residence

time and initial gas temperature exert a larger effect on the residual moisture and

residual volatile yield.

Based on the wet core model of dry shell/shrinking developed by McIntosh, a

model of moisture evaporation interface between dry/wet regions moving in a single

spherical lignite particle during the drying process was established using finite volume

method. The equation was solved using Crank-Nicolson scheme and Matlab program.

Thus, the distribution of moisture content and temperature in a single lignite particle

under different conditions can be obtained by the numerical simulation.Some

predictions were carried out using the model and the predictions agreed well with the

experimental results. This verifies at the model can be used to simulate the drying

process of a single spherical lignite particle.

The quantitative analyses of some parameters, which was hard to be measured

using experimental method in the research were carried out using the model. Thus, the

effects of these parameters were further discussed. The results show that the variations

of the water loss and lignite particle temperature with residence time are different under

different original gas temperature. With the increasing temperature, the dewatering rate

and the particle temperature rising rate increase. With the increase of the lignite particle

size and the initial moisture content, the dewatering rate and the temperature rising rate

are decreased to some extent. It is found that the moisture content of a lignite particl of

20 mm decreases from 25.3% in the raw lignite to 12 % in the product within the

residence time of 156s and the heat value of the coal increase to 20.51MJ/kg by

3767.4kJ/kg.

Key words：lignite, dewatering/upgrading, heat and mass transfer, drying process,

mathematical model

中文摘要

ABSTRACT

第一章绪论 ......................................................... 1

§1.1 我国褐煤资源概况 ............................................. 1

§1.2 褐煤的结构与特性 ............................................. 3

§1.3 褐煤干燥技术分析 ............................................. 4

§1.3.1 机械热压成型提质技术 ..................................... 4

§1.3.2 非蒸发脱水提质技术 ....................................... 5

§1.3.3 物理蒸发干燥技术 ......................................... 7

§1.4 褐煤蒸发干燥过程分析 ........................................ 12

§1.4.1 蒸发干燥过程 ............................................ 12

§1.4.2 干燥过程中的热质传递机理 ................................ 13

§1.5 本论文的主要内容 ............................................ 16

第二章实验方案及设备介绍 ........................................... 17

§2.1 实验样品 .................................................... 17

§2.1.1 煤质分析 ................................................ 17

§2.1.2 物性参数 ................................................ 17

§2.2 实验装置 .................................................... 18

§2.2.1 脱水提质实验装置 ........................................ 18

§2.2.2 热天平实验装置 .......................................... 19

§2.2.3 辅助设备说明 ............................................ 20

§2.3 实验步骤 .................................................... 21

§2.3.1 实验步骤 ................................................ 21

§2.3.2 注意事项 ................................................ 22

§2.4 试验设计与数据处理方法 ...................................... 22

§2.4.1 预备性实验 .............................................. 23

§2.4.2 正交实验 ................................................ 23

§2.5 主要参数的测量 .............................................. 24

§2.5.1 水分、挥发分含量 ........................................ 24

§2.5.2 发热量计算 .............................................. 24

第三章干燥条件对褐煤脱水提质的影响 ................................. 26

§3.1 褐煤脱水提质效果的主要影响因素 .............................. 26

§3.1.1 热流温度 ................................................ 26

§3.1.2 粒径大小 ................................................ 26

§3.1.3 停留时间 ................................................ 26

§3.2 实验结果与讨论 .............................................. 26

§3.2.1 实验结果 ................................................ 26

§3.2.2 工况条件对褐煤干燥的影响 ................................ 28

§3.2.3 正交实验分析 ............................................ 30

§3.3 本章小结 .................................................... 32

第四章单颗粒褐煤高温热气流干燥模型 ................................. 33

§4.1 干燥过程分析 ................................................ 33

§4.2 模型假设 .................................................... 34

§4.3 控制方程 .................................................... 34

§4.3.1 守恒方程 ................................................ 34

§4.3.2 干区传热、传质方程 ...................................... 35

§4.3.3 湿区传热方程 ............................................ 35

§4.3.4 初始条件 ................................................ 36

§4.3.5 边界条件 ................................................ 36

§4.4 算法 ........................................................ 36

§4.5 离散化 ...................................................... 36

§4.6 本章小结 .................................................... 41

第五章模型计算结果与分析 ........................................... 42

§5.1 求解方法 .................................................... 42

§5.2 物性方程 .................................................... 44

§5.2.1 物性参数 ................................................ 44

§5.2.2 对流传热、传质系数 ...................................... 45

§5.3 热气流温度的模拟结果与实验结果对比 .......................... 46

§5.4 单颗粒褐煤高温热气流干燥性能的模型预测 ...................... 47

§5.4.1 热气流温度对脱水提质的影响 .............................. 48

§5.4.2 停留时间对脱水提质的影响 ................................ 48

§5.4.3 颗粒粒径对脱水提质的影响 ................................ 49

§5.5 本章小结 .................................................... 50

第六章总结与展望 ................................................... 51

§6.1 总结 ........................................................ 51

§6.2 展望 ........................................................ 52

主要符号表 .......................................................... 53

参考文献 ............................................................ 55

在读期间公开发表的论文和承担科研项目及取得成果 ...................... 61

致谢 ............................................................... 62

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摘要：

摘要随着经济的高速发展，石油、天然气及煤炭等传统能源日益枯竭，能源价格居高不下，低品质能源褐煤的综合利用与开发势在必行。我国褐煤资源丰富，但由于我国褐煤“三高两低”（高水分、高灰分、高含氧、低热值、低灰熔点）的特点，限制了褐煤的综合利用。因此，有必要对褐煤进行脱水提质处理，扩大褐煤的综合利用途径，提高褐煤的市场竞争力。本文首先介绍了我国褐煤的资源概况、特点及其利用情况，并充分阐述了国内外褐煤脱水提质技术的应用现状及其发展趋势。初步分析了振动床顺流高温热气流干燥技术的可行性。本论文并结合干燥实验和数学模拟研究了高温烟气下褐煤干燥过程。利用自制褐煤脱水提质实验台开展实验研究，重点考察干燥介质（氮气...

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