煤粉催化燃烧技术的基础研究
文献类型：学位论文
| 作者 | 公旭中 |
| 学位类别 | 博士 |
| 答辩日期 | 2010-01-15 |
| 授予单位 | 中国科学院过程工程研究所 |
| 授予地点 | 过程工程研究所 |
| 导师 | 郭占成 |
| 关键词 | 煤粉 催化燃烧 反应性 燃烧效率 催化热解 |
| 其他题名 | Fundamental Research on Catalytic Combustion Technology of Pulverized Coal |
| 学位专业 | 化学工艺 |
| 中文摘要 | 煤炭占我国一次能源的70%左右，因此我国的发展对煤炭的依赖尤为突出。燃烧是煤炭利用的主要方式，我国每年煤炭消费量的80%以上用于直接燃烧，导致了我国的环境污染是以煤烟型的大气污染为主。由于生产技术水平的落后，导致了我国煤炭燃烧过程中利用率较低，因此在煤炭燃烧过程中实现节能减排具有重要意义。煤粉催化燃烧是一种高效的燃烧技术。本文就此在以下几个方面对煤粉催化燃烧技术进行了应用基础研究，并取得了一些创新性研究结果。 (1) 利用热重、差热、固定床、流化床等反应器研究了催化剂、煤质、燃烧工艺等应用条件对煤催化燃烧效果的影响。结果表明，无烟煤中分别加入Ca-Fe-Ce工业复合催化剂、以及Fe2O3、CeO2、CaCO3等单组份催化剂均可以提高无烟煤在上述反应器内的燃烧反应性，由于复合催化剂组分间的协同作用导致了相同条件下，其催化效果由于单组份催化剂。相同方法制备的催化剂可以通过降低催化剂的粒径，燃点降低和燃速增加幅度更大。化学组分相同，而制备方法不同时，提高催化剂表面上具有催化活性的晶面的比例，则可以提高燃点降低幅度。变质程度越高的煤种，燃点降低幅度更大。当CeO2作为催化剂时，煤中矿物质和CeO2具有一定的协同作用，随着煤中矿物质的增加，协同作用逐渐消失。在相同的燃烧条件下，系统中氧气的浓度越大，升温速率越高，燃点降低和燃速增加幅度更大。 (2) 提出了研究煤粉催化燃烧特性的RDTA法。即将常规DTA实验中的参比物替换为没有加入催化剂的煤粉，而样品坩埚中加入负载有催化剂的煤粉，这样获得的DTA曲线，称为RDTA曲线。RDTA法能够更加直观地反映出催化燃烧时，煤粉燃点和燃烧效率的变化。 (3) 将煤粉燃烧反应模拟成多个连续的等温相变过程。利用常规DTA和RDTA数据，结合相变焓计算方程。将方程中的系数(KC)由特定温度下的常数，转变为一个温度的函数。利用这一温度函数替代相变焓计算方程中的特定温度下的系数，计算了煤粉在DTA反应器中，单位质量煤粉催化燃烧时的放热量。结果表明催化燃烧可以提高单位质量煤粉燃烧时的放热量。 (4) 基于不同反应器内催化燃烧过程中CO2的释放规律，研究了催化燃烧对反应器的选择性。在热重和固定床内催化剂可以提高煤粉燃烧反应性和燃烧效率，在流化床中催化剂只能提高煤粉的燃烧反应性，而不能提高燃烧效率。当采用Fe2O3为催化剂时，在微型流化床、固定床、热重三种反应器内煤粉燃烧反应性指数(CO2释放指数)分别为82.8%、16.7%、11.1%。其燃烧效率的指数分别为0%、6%、3.4%。 (5) 基于催化热解的研究，本文详细地分析了无烟煤催化燃烧时燃点降低的原因。研究表明催化剂促进了无烟煤的热解是其燃点降低主要原因。无烟煤的点燃过程属于异相燃烧过程，半焦周围有效的氧气浓度。①在较低的温度下，催化燃烧为点燃前提供了比非催化燃烧多的热解气，增加了均相燃烧提供的热量。②催化燃烧点燃前催化热解使得半焦的结构更具活性：活性位增加，含氧量增加。导致了半焦吸附氧的速率增加，吸附氧气量减少，使得半焦周围很快达到了点燃所需的氧气量，开始在较低的温度燃烧。 (6) 采用燃烧失重率、DTA曲线面积、CO2的释放量等变化量，利用阿雷尼乌斯方程，用EXCEL程序拟合并优化了常见气固反应模型，并利用优化后模型计算了煤粉催化燃烧和热解动力学。结果表明三种变化量所计算的无烟煤催化燃烧的表观活化能均低于非催化燃烧的表观活化能。 |
| 英文摘要 | In China, coal occupies about 70% in primary energy. Combustion is one of the most important ways of coal utilization, and 80% of consumed coal amount were combusted directly every year, bringing about many contaminations for atmosphere. Due to lagging technology, coal combustion efficiency was very low in many industrial boilers. Consequently, it was very significant to achieve energy-saving and emission-reduction for coal combustion process. Catalytic combustion of pulverized coal is the high effective approach. In this paper, several works were carried out to understand catalytic combustion of coal and some innovative as follows: (1) Effects of applied conditions, including catalysts, coal properties and combustion technologies, on catalytic combustion reactivity of pulverized coal were investigated using TGA, DTA, fixed bed and fluidized bed. The results indicated that catalytic activity of Ca-Fe-Ce was higher than that of Fe2O3, CeO2, and CaCO3 for combustion reactivity of anthracite. For catalyst from the same preparation, the smaller the particle size, the better the catalytic activity. For catalyst from the different preparation, it was very important to increase the proportion of exposed crystalplane with catalytic activity. The catalytic effects increased with increasing coal rank, whereas the catalytic activity decreased with increasing coal ash content. There were sme positive interactions between coal ash composition and CeO2, resulting in better catalytic effects. In addition, the higher the heating rate and oxygen concentration is, the higher the catalytic combustion reactivity is. (2) To directly study catalytic combustion characteristics of pulverized coal, RDTA (referenced differential thermal analysis) was proposed for the first time. With it, the raw anthracite was used as reference, and anthracite with catalysts was used as sample in the RDTA experiment. RDTA curve could directly reveal the variation of ignition temperature and combustion effiency during catalytic combusiotn process of coal. (3) Coal combustion reaction was simulated into a seriate phase transition process. The effects of catalysts on combustion efficiency of anthracite were inversigated using DTA and RDTA. Based on the equation for calculation enthalpy of phase change, the constant KC was modified into a function of temperature to calculate heat release from coal combustion for the first time. The results indicated that catalytic combustion increased efficiency of coal combustion. (4) Based on CO2 emission of catalytic combustion of pulverized coal in the different reactors, selectivity of catalytic combustion for combustion reactor was investiged. In TG, fixed bed and fluized bed, combustion reactivity of anthracite was improved by catalysts. Meanwhile, catalytic combustion can increase combustion efficiency in TG and fixed bed, however, it can not imprve combuston efficiency in the fluized bed. When Fe2O3 was used as catalyst for coal combustion, combustion reactivity index of micro-fluidized bed, fixed bed and TG was 2.8%, 16.7% and 11.1%, respectively. And their combustion efficiency index was 0%, 6.0% and 3.4%, respectively. (5) Mechanism of lowered ignition temperature was proposed based on pyroysis stage of catalytic combustion process in detail. The results showed that catalytic pyrolysis was main reason lowered ignition temperature of anthracite. There are two reasons for lowered ignition temperature and increasing combustion rate during catalytic combustion process of anthracite. On the hand, catalytic combustion provided more pyroysis gas than that of non-catalytic combustion at lower temperature, advancing heat from homogeneous combustion before coal ignition. On the other hand, reactivity of char from catalytic pyrolysis was higher than that of non-catalytic pyrolysis. Catalytic pyrolysis resulted in higher combustion activity of char with lowered ordering degree, more active sites and increasing oxygen content. (6) Kinetics parameters of pyrolysis and combustion were calucalated using Arrhenius equation combined with the data from TG, DTA, CO2 emssion and gas-solid models. The results from kinetics parameters showed that activation energy of catalytic combustion of anthracite was lower than that of non-catalytic combustion. |
| 语种 | 中文 |
| 公开日期 | 2013-09-13 |
| 页码 | 153 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1264]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 公旭中. 煤粉催化燃烧技术的基础研究[D]. 过程工程研究所. 中国科学院过程工程研究所. 2010. |
入库方式： OAI收割
来源：过程工程研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。