Knowledge Management System Of Institute of process engineering,CAS
煤的催化热解是从低阶煤炭资源中提取液体燃料和高价值化学品的主要技术之一，钢铁工业是国民经济的重要基础产业。针对目前煤催化热解提质存在的催化剂成本高昂、难分离回收等关键问题，并结合我国铁矿石品质日趋降低的现实问题，课题提出开展煤热解与铁矿石还原耦合过程基础研究，采用低品质铁矿石催化煤热解，实现焦油轻质化同时获得高品位还原铁矿石。本文将从基础和工艺两个层面出发，对铁矿石催化反应机理与煤催化热解产物形成规律、铁矿石还原反应机制以及煤热解与铁矿石还原耦合工艺等方面进行系统的研究。主要研究内容及结果如下：1. 采用Py-GC/MS快速裂解仪研究了不同铁矿石的催化裂解作用及其对煤热解产物分布影响规律，结果表明所考察四种铁矿石中，褐铁矿催化裂解作用最为显著，促进了煤热解产物中轻质芳烃的生成；铁矿石物化性质表征结果表明铁矿石比表面积与轻质芳烃产率存在正相关性；以正十九烷和甲酚为模型化合物，结合气体中含氧气体产率与轻质芳烃产率变化关系发现，含氧化合物的脱氧转化可能是褐铁矿催化裂解焦油生成轻质芳烃的主要途径；褐铁矿催化多煤种热解反应结果显示，煤中含氧量越高，褐铁矿的催化效果越显著，间接验证了褐铁矿对焦油中含氧化合物脱氧转化的催化作用。2. 进一步利用Py-GC/MS开展了操作条件对铁矿石催化煤热解产物裂解的影响规律研究。结果表明提高反应温度、H2气氛下增加反应压力（0.1-0.9 MPa）均有利于轻质芳烃的形成，但加压与H2气氛对褐铁矿催化裂解性能并未表现出明显促进作用；同时热解产物分析结果表明，铁矿石催化作用主要体现在促进酚类及其他含氧化合物的脱氧分解以及芳烃化合物的形成；褐铁矿多循环及再生实验证明催化反应过程褐铁矿还原为低价态铁而提高催化活性，多次循环及再生后褐铁矿保持较高活性。3. 利用固定床装置，研究了热解气氛下铁氧化物的还原特性，以模拟热解气和焦油模型化合物为原料，分别考察了还原温度、时间以及焦油含量对三氧化二铁还原程度的影响。研究结果表明提高还原温度和反应时间，均有利于促进Fe2O3的还原，但单纯热解气对铁氧化物还原能力较低，而焦油的加入能够推进Fe2O3向高品质Fe3C的还原进程；提高热解气相产物中焦油蒸汽分压，将有利于促进铁矿石的还原，获得高品质的深度还原铁产物。初步验证了铁矿石催化煤热解反应过程能够获得高品质还原铁的可行性。4. 基于Py-GC/MS快速裂解仪和固定床装置上的实验结果，设计并搭建了一套煤热解耦合铁矿石还原的连续反应装置，并通过煤热解、铁矿石催化裂解反应参数优化实验，考察了不同温度和空速条件下褐铁矿催化煤热解产物分布的影响，并获取优化工艺参数：热解温度550oC，固相停留时间15 min，催化裂解温度700oC，空速7651 h-1，此时焦油中轻质焦油产率为3.78 wt%，含量达到85.12 wt%，较热裂解条件分别提高6.70%和29.42%。褐铁矿催化煤连续热解反应产物分析结果表明焦油轻质化主要来自重质焦油的裂解以及含氧化合物的转化，并进一步对煤催化热解反应过程含氧化合物的转化路径作出阐释。5. 通过对煤连续热解耦合铁矿石还原反应获得褐铁矿进行了孔隙结构、物相组成、积碳量、微观形貌、还原度等物化性质的表征分析，对铁矿石还原反应基本过程进行了阐述，铁矿石经预热脱水处理形成具有较高比表面积的多孔结构，促进褐铁矿向还原态铁FexOy (y/x<1.5)转化；反应条件对铁矿石还原影响结果显示空速对铁矿石还原影响高于反应温度，优化工况下（700oC，3825 h-1）获得铁矿石以Fe3O4和FeO形式存在，还原度可达24%。结合热重分析结果发现耦合过程获得的含碳铁矿石具有较高的还原活性，能够作为炼铁的优质原料。6. 建立了煤热解与铁矿石还原耦合工艺的?分析体系，采用?分析法对比研究了独立的煤热解+铁矿石预热工艺和煤热解与铁矿石还原耦合工艺的?损失；?分析结果表明高温裂解气物理?的回收能够有效地减少煤热解与铁矿石还原全过程的?损失，与煤热解、铁矿石预热独立工艺相比，耦合工艺?损失降低了10.4%；耦合反应获得的含碳铁矿石可作为优质的球团烧结原料，当原料中含积碳铁矿石的掺混比例超过50%时，即可实现烧结系统的热量自给，不产生外配焦粉成本。;Catalytic pyrolysis is one of the major technologies producing liquid fuels and valuable chemicals from low-rank coal resources. The iron and steel industry is an important basic industry of the national economy. Various catalysts examined so far for coal catalytic pyrolysis still has lots of problems such as: high cost, difficult separation and recovery, etc. To solve catalyst problems and make up the shortage of high-grade iron ores, an integrated process combined coal pyrolysis with iron ore reduction was put forward. The process adopts low-grade iron ores to catalyze coal pyrolysis vapor to obtain light tar, while iron ore is reduced by the pyrolytic vapor at the same time. The distribution and formation of coal pyrolytic products catalyzed by iron ores, the mechanism of iron ore catalytic reaction, the mechanism of iron ore reduction, the technology of integration process of coal pyrolysis combined with iron ore reduction in both the fundamental and technological aspects have been investigated in this thesis. The major findings are listed as following: 1. The impact on coal pyrolysis products by different iron ores were studied by Py-GC/MS. Results showed that limonite was the most effective one for promoting the formation of light aromatic hydrocarbons among four iron ores. The microstructure and physicochemical properties of iron ore showed positive correlation between the specific surface area of iron ore and the yield of light aromatic hydrocarbon. Using C19 alkanes and phenol as model compounds, it is found that deoxygenation is dominant in the pathways of formation of light aromatics considering the relation between oxygen-containing gas yield and yield of light aromatics. Results of coal effect exhibited that high oxygen content of coal has a relatively high percentage increase of light aromatics. It was indirectly validated that the catalytic effect of limonite on deoxygenation and transformation of oxygen-containing compounds in coal tar.2. The effect of operating conditions on coal pyrolysis products over iron ore catalyst was further studied by Py-GC/MS. The results showed that high temperature, high pressure in hydrogen atmosphere were beneficial to the formation of light aromatics. However, high pressure (0.1-0.9 MPa) and hydrogen atmosphere suggested no significant promotion on the limonite’s catalytic cracking. Limonite promoted the decomposition of phenols and oxygenates and formation of light aromatics. The experiments of multicycle and regeneration of limonite showed that the reduction of limonite to low valence iron increased the catalytic activity, and the limonite remained high activity after many cycles and regeneration.3. The reduction characteristics of iron oxides in pyrolytic vapor were studied on a fixed bed reactor. The effects of reduction temperature, reduction time and tar concentration on the reduction degree of ferric oxide were investigated using simulated pyrolysis gas and tar model compound as raw materials. The results showed that the reduction degree of iron oxide increases with the increase of reduction temperature and time. Pyrolysis gas only had a weaker reduction ability and addition of tar would promote the reduction of ferric oxide to cementite. Increasing the tar concentration in the pyrolytic vapor could promote the reduction process to obtain high quality iron products. The feasibility of high quality iron products attained from integration of coal pyrolysis with iron ore reduction was proved. 4. Based on the results of experiments operated on Py-GC/MS and fixed bed reactor, a continuous apparatus of integration coal pyrolysis with iron ore reduction was designed and set up. The reaction conditions of coal pyrolysis were optimized. Under the optimized condition the catalytic cracking temperature and space velocity were examined. The highest light tar yield achieved was 3.78 wt%, and the content of the light tar is 85.12 wt% at pyrolysis temperature of 550oC, solid retention time of 15 min, the catalytic cracking temperature of 700 oC and space velocity of 7651 h-1. The light tar yield and content has increased by 6.70% and 29.42%, respectively, comparing with the thermal cracking under same condition. The products catalyzed by limonite showed that light tar mainly came from the cracking of heavy tar and the conversion of oxygen-containing compounds in tar. Oxygen-containing compounds during the catalytic process were analyzed to give further explanation.5. The physicochemical properties of limonite obtained from the integration of coal pyrolysis with iron ore reduction process, such as pore structure, phase composition, carbon deposition, microscopic morphology and reduction degree, were characterized. The basic reduction process was describe based on the results. Porous iron ore formed after the dehydration process was easily reduced to FexOy (y/x<1.5). Results has shown that space velocity is more significant than catalytic cracking temperature on reduction process. The reduction degree could be 24% under the optimal condition (700oC, 3825 h-1), while iron ore products was composed of Fe3O4 and FeO. Thermogravimetric analysis illustrated that carbonized ore had higher reactivity, which could be used as high quality raw materials for ironmaking.6. The exergy analysis diagram of integration of coal pyrolysis with iron ore reduction was established. Compared with the conventional process (separated coal pyrolysis and iron ore preheating process), the integrated process reduced the exergy loss by 10.4%. The reduced exergy loss could owe to the recovery of the physical exergy of high temperature cracking gas. Moreover, the carbonized iron ore could be applied in sinter plant. When the ratio of carbonized iron ore exceeds 50%, the heat produced from carbonized ore could be sufficient without additional coke breeze cost.
|贺璐. 煤热解与铁矿石还原耦合工艺的基础研究[D]. 中国科学院研究生院,2018.|
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