煤炭拔头－气化工艺集成的基础研究
文献类型：学位论文
| 作者 | 朱文魁 |
| 学位类别 | 博士 |
| 答辩日期 | 2008-12-08 |
| 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 | 林伟刚 |
| 关键词 | 煤拔头 半焦 气化 集成工艺 |
| 其他题名 | Fundamental Research on the Integrated Process of Coal Topping and Gasification |
| 学位专业 | 化学工程 |
| 中文摘要 | 在我国的煤炭资源中，挥发分较高的年轻煤所占比例较大，Vad在28％以上的低阶煤约占全国煤炭储量的75％左右。以煤炭分级转化技术为基础的煤拔头工艺采用低阶煤为原料，通过温和的转化方式从年轻煤中获取轻质燃料油和高值化学品，为年轻煤种高效洁净利用提供了新的途径。 煤炭分级转化技术，依据煤结构组成的非均一性和不同组分的转化特性的差异，将热解、气化、燃烧等多种煤炭转化技术有机集成在一起，对煤炭实施分级转化，有利于提高煤炭综合利用和整体转化效应。基于此，针对低阶煤，本文提出了煤拔头－气化分级转化工艺，即将煤拔头产生的半焦气化以制备合成气或燃气，可将年轻煤完全转化为液体和气体燃料，有利于实现煤炭更为高效和洁净的转化，同时也扩展了煤拔头工艺的应用领域，如合成气工业及燃气发电技术等领域。 对煤炭实施拔头－气化分级转化，并非将煤拔头与气化工艺简单叠加，而是以系统整体的煤炭利用价值和利用效率的最大化为目标，依据煤拔头工艺及产物半焦的特点，并根据燃料在不同工艺过程中的转化规律，对煤拔头与气化工艺进行优化集成。为此，在煤拔头工艺研究的基础上，本文系统的研究了煤拔头半焦的特性、拔头工艺条件对半焦反应性影响、半焦气化转化规律及反应动力学，在此基础上提出并分析了可能实施的集成工艺方案，为煤炭拔头－气化分级转化工艺的优化集成，提供了试验及理论依据。 本研究在喷动－载流床中制备了不同条件下的煤拔头半焦，考察了其组成与结构特性。在热天平中考察了不同热解条件制备的半焦的气化反应性，研究了拔头工艺条件对半焦反应性的影响。研究结果表明，热解温度是影响煤拔头半焦产率及组成与结构的主要热解工艺条件，挥发分的析出程度及其二次反应是影响热解半焦产率的主要因素。随热解温度升高，煤拔头半焦中含氧结构脱除程度增加、芳香结构缩聚程度增大、H/C降低，但半焦的碳结构尚无明显的石墨化现象。 研究了煤拔头工艺条件对半焦反应性影响及作用机理，结果表明：煤拔头热解过程中，挥发分的二次反应，即二次热解焦的生成，是影响半焦气化反应性的主要因素。热解温度的增加及停留时间的延长，加剧了挥发分的二次反应程度，降低了半焦的气化反应性。随原料粒级的增加，其中的矿物质含量降低。不同粒径原料中这种矿物质的偏析以及颗粒内挥发分的二次反应，是导致半焦的反应性随原煤粒径增加而显著降低的主要原因。 在固定床反应装置中，研究了煤拔头半焦气化特性，并制备了部分气化焦，考察了部分气化焦的结构变化。研究表明，变质程度较高的煤，其半焦存在更为显著的阶段气化反应特性，即随气化程度的加深，其半焦的气化反应速度降低的程度更大；同一煤种，反应温度愈低，半焦气化反应速率降低程度也越大。与热解焦相比，部分气化焦中有序碳浓度增大，其碳结构的有序程度增加；矿物质对煤焦碳结构的石墨化程度亦有影响，脱除矿物质使煤焦中碳结构的有序程度增大。 气化动力学研究表明，所采用的三种动力学模型均可用于模拟煤拔头半焦的气化过程，但提出的修正后的半经验模型可以很好的反映出气化温度及不同煤种对半焦的阶段气化反应特性的影响，并具有相对较好的模拟精度。 对煤拔头和气化工艺集成的分析表明，CFB技术可以成为煤拔头工艺和半焦气化集成的平台；优化煤拔头热解条件以降低热解过程中挥发分二次反应程度，有利于同时提高热解焦油产率和半焦气化转化效率；半焦的气化过程为集成工艺的控速步骤，应充分考虑不同煤焦气化过程中转化特性的差异，以提高系统整体的煤炭转化效率。基于以上分析，针对不同半焦的转化特性，提出了两种可能的技术方案。基于Aspen plus平台建立了气化模型，对半焦气化过程和系统热量平衡进行了分析。 此外，本文探索了以富含碱金属的生物质作为廉价的催化剂来源以催化煤焦气化反应这一思路，研究了煤/生物质共热解焦的气化反应特性。研究结果表明，麦秸中的碱金属的催化作用使共热解焦的反应性显著高于煤焦；通过煤/生物质拔头－气化的共处理工艺，生物质中的碱金属可有效用于催化煤焦的气化反应，因此，富含碱金属的生物质有望成为煤焦气化反应的廉价的催化剂来源。 |
| 英文摘要 | In China, the resources of low rank coal (bituminous coal and lignite) account for 75% of the coal reserves. The coal-topping process，which extracts light fuel oil and valuable chemicals from coal before combustion by flash pyrolysis at mild conditions, provides a way for efficient and clean utilization of low rank coal. According to the heterogeneity of coal and the difference in reactivity of different components in coal, the staged conversion process of coal integrates different coal conversion technologies and carries out the gradient utilization of coal, which is favorable for improving the overall efficiency and benefit of coal conversion. When coal-topping process is integrated with char gasification, low rank coal could be converted entirely into liquid and gas fuels. This staged conversion process of coal would realize more efficient and clean utilization of coal. By this integrated process, the coal-topping technology can be widely used in the field of syngas industry and gas-fired power generation. The coal topping-gasification process is not a simple combination of coal topping and gasification technologies, but an optimized process which aims at the maximum of efficiency and value of coal utilization according to the characteristics of coal-topping technology and char as well as the conversion behavior of fuel in different process. Accordingly, on the basis of previous research work on coal topping, the characteristics of char form coal topping, effect of pyrolysis conditions on char reactivity and gasification behavior and reaction kinetics of char are systematic discussed in the paper. Based on the above work, the possible schemes of coal topping-gasification process are proposed and analyzed. The chars are prepared in a spout-entrained bed. Char characteristics are investigated and the char reactivity is analyzed in a TGA. The effect of coal topping conditions on char gasification reactivity was studied. The results show that pyrolysis temperature is the main factor effecting yield and composition and strucrure of chars. With the increasing of pyrolysis temperature, the condensation of aromatic structure increases and the oxygen-containing groups as well as the H/C ratio decreases, while no obvious graphitizing phenomenon was observed in char structure. The effect of pyrolysis conditions on char reactivity was investigated. The results indicated that the secondary reactions of volatiles accounts for the influence of pyrolysis temperature and residence time on char reactivity, and the decrease of secondary reactions is beneficial to improve char reactivity. The effect of coal particle size on char reactivity is associated with the mineral segregation between different size fractions of coal and the secondary reactions of volatiles. The reactivity of chars from coal topping is similar with coal, while obviously higher than chars prepared by slow-pyrolysis method. In a fixed bed system, gasification behavior of chars and their structure was investigated. The results show that gasification rate of char decreases with the increasing of gasification conversion ratio, and the decrease of gasification rate for Datong coal with higher rank is more obvious; for the same coal, the decrease of gasification rate is also more evident at lower gasification temperature. Compared with pyrolysis char, ordered carbon in part-gasification chars increases and graphitization degree of char enhances; mineral also effects the graphitizing of char structure, and the removal of mineral improves the graphitization degree of char. The study on the reaction kinetics of chars show that three kinetics models, including pseudo homogeneous model, shrinking core model and revised simi-empirical model, all can be used to simulate the gasification process of char from coal topping, but the revised simi-empirical model can reflect the effect of temperature and coal type on the gasification behavior of char well and has a relatively higher simulation precision. According to the analysis of coal topping-gasification process, the Circulating Fluidized Bed (CFB) can become the platform of integrated process; optimizing the pyrolysis conditions of coal topping to decrease the secondary reactions of volatiles is beneficial for the increase of both tar yield and gasification rate of char; the gasification of char is the rate determining step of integrated process, so the difference of char gasification behavior for different coal should be sufficiently considered when the processes are integrated in order to improve the overall efficiency of coal conversion. Bases on the above, two possible schemes of coal topping-gasification process are proposed. A gasification model was established by Aspen plus and gasification process of char as well as heat balance of integrated process was analyzed. In addition, as an exploratory research work based on the idea that use the biomass with high content of AAEM as a cheap catalysis to catalyze the gasification of coal/char, gasification characteristics of co-pyrolysis char from coal/biomass were investigated. The results show that reactivity of co-pyrolysis char is advanced by catalysis of AAEM from biomass, and by coal/biomass topping-gasification process, AAEM in biomass can be used to catalyze the gasification of coal/char, which means biomass with high content of AAEM can become a cheap source of gasification catalysis. |
| 语种 | 中文 |
| 公开日期 | 2013-09-13 |
| 页码 | 160 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1191]  |
| 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 | 朱文魁. 煤炭拔头－气化工艺集成的基础研究[D]. 过程工程研究所. 中国科学院过程工程研究所. 2008. |
入库方式： OAI收割
来源：过程工程研究所
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