【作者】 关珺；

【导师】 张秋民；

【作者基本信息】 大连理工大学 ， 化学工艺， 2013， 博士

【摘要】 褐煤提质是提高褐煤利用效率和减少污染排放的有效手段。本文围绕着褐煤低温热改质过程,研究了褐煤表面含氧官能团随温度的变化规律；重点研究了低温热改质温度对热改质冷凝水水质和冷凝水中有机物的组成与含量影响的规律；考察了改质后提质煤的成型性能。论文的研究内容和取得的研究结果包括：1、以霍林河褐煤和小龙潭褐煤为原料,在间壁式热改质装置上进行了褐煤低温热改质实验。实验结果表明：褐煤在100℃改质时,煤中水的脱除率不足50%：热改质温度高于150℃后,煤中的水分基本可以全部脱除。提质煤的挥发分随热改质温度的升高而减低,热改质温度升高至400℃,霍林河和小龙潭煤提质煤的挥发分分别下降了10.69%和15.60%。由平均芳环数可知,霍林河和小龙潭褐煤分别在400℃和350℃煤大分子碳骨架开始发生明显改变。2、对原煤和提质煤的表面官能团进行了红外和化学分析。研究发现,小龙潭原煤存在着类似泥炭的多聚羟基为主的网状体系(Coal—OH—O—Coal),在热改质温度超过250℃后这种结构被破坏。随热改质温度的增加,褐煤表面含氧官能团的脱除率显著增加,400℃时羧基的脱除率为90%以上,而酚羟基的脱除率与氧元素的脱除率相当,不足50%。在改质温度超过400℃后对小龙潭和霍林河原煤中烷烃支链、醚氧基结构和CH2桥键结构有明显影响。3、对褐煤低温热改质冷凝水水质进行了研究。实验结果表明：热改质温度在200℃前收集的冷凝水无色透明;200℃热改质冷凝水氨氮指标略高,可通过简单生化处理达标。250℃时冷凝水开始略带褐色,在350℃后开始出现分层现象,水质劣化明显。4、使用GC-MS分析了热改质冷凝水中的有机物。结果揭示了冷凝水中有机物含量随热改质温度变化的规律。实验结果表明：冷凝水中有机物组成十分复杂,包含了脂肪烃、芳香烃、含氧化合物和杂环类等化合物。含氧化合物含量最高,包括酚类、醇类、醛类、酮类、酸类和酯类等。其中,酚类物质是冷凝水中有机物含量最高的一类,其含量随处理温度的升高而增加。低级酚在冷凝水中酚类物质占比例很高,含量超过总酚的80%。与甲酚的脱烷基反应活性顺序不一致,三种甲酚的含量顺序是间甲酚>邻甲酚>对甲酚；苯酚的产率随热改质温度的增加而增加,但总酚中苯酚的比例并未呈现出类似煤热解焦油中一直上升的规律,可能是由于生成的酚类化合物经历酚分解过程或裂解和脱烷基反应不充分造成的。5、使用Aspen Plus软件NRTL活度系数法建立冷凝水脱酚过程模型,并根据相平衡实验数据对NRTL模型参数进行矫正。并对萃取塔中相比、温度、塔板数和塔板效率进行了灵敏度分析。结果表明,采用三级逆流萃取,以醋酸丁酯为萃取剂苯酚及甲酚在萃取温度20℃、水油相比3：1、理论塔板数3的条件下,可使冷凝水中的苯酚和甲酚含量降至满足生化处理要求。6、研究了褐煤和提质煤无粘结剂成型。结果表明,褐煤成型压制曲线总体变化大致可以分为褐煤粉末的致密化、部分褐煤颗粒开始发生形变、稳定阶段和褐煤颗粒发生明显形变四个阶段。褐煤颗粒群特性可以使用RRB方程进行描述。颗粒群特性、成型压力、水分含量和提质煤混合比例是影响型煤强度的主要因素。热改质温度为400℃的提质煤单独成型困难,配入一定量原煤后可顺利成型。更多还原

【Abstract】 Thermal upgrading process is the most effective technology that removes moisture and certain pollutants from lower-rank coals such as sub-bituminous and lignite (brown) coals and in order to raise their calorific values. The goals of lignite upgrading technologies are to increase efficiency and reduce emissions before coal utilization. Therefore, in this thesis, the changes of oxygen-containing functional group contents with thermal upgrading of lignite were studied in detail, the influence of upgrading temperature on the water quality including composition and distribution of organic matter in lignite-derived water was investigated and the effects of upgrading process on coal briquette were also studied.The main works and results of this research are as follows:1) Two Chinese coals, Huolinhe(HLH) lignite and Xiaolongtan(XLT) lignite, were used to investigate the lignite upgrading reaction within the ranges of100℃-400℃℃. The results showed that the reduction of its water proportion of upgraded coal was no more than50%when the temperature was100℃,and down to below5%when the temperature exceeded150℃. The volatile matter in the upgraded coals was decrease with an increase of upgrading temperature. The volatile matter in the upgraded HLH and XLT lignites was reduced by10.69% and15.60%respectively compared with the raw lignites. By calculating the average number of aromatic rings, we know that large aromatic molecules of lignites were changed considerably when upgrading temperature exceeded400℃for HLH lignites and350℃for XLT lignites.2) FI-IR and chemical analysis were used to investigate the changes of oxygen-containing groups with different upgrading temperatures. The results indicated that network systems like Coal-OH-O-Coal were found in raw XLT lignite which are analogous to peat. The Coal-OH-O-Coal network systems were destroyed easily while upgrading temperature went over250℃. Besides, the oxygen-functional groups contents of both upgraded HLH and XLT lignites decreased obviously, especially carboxyl groups, at400℃, the removal rate of carboxyl groups had reached90%. The removal rate of phenolic hydroxyl groups was commensurate with that of oxygen element. In addition, when the upgrading temperature was more than400℃,it had obvious effects on alkane chain, ether oxygen bond and CH2bridged bond.3) Lignite-derived water from lignite upgrading reaction was analyzed with COD, NH3-N, phenols etc. The experimental results showed that the water was colorless and transparent when the upgrading temperature was not more than200℃. 4) In order to better understand the composition and distribution of organic matter in lignite-derived water, GC-MS was used to analyze the organic matter in water. The results showed that the proportion of organic matter in water went up with the increase of the upgrading temperature. Furthermore the composition of organic matter was very complex, including aliphatic hydrocarbon, aromatic hydrocarbon, oxygen containing compounds and heterocyclic compounds. And phenols, alcohols, aldehydes, ketones, acids, esters and other complex compounds in oxygen containing compounds were detected as well. Phenols were found as the highest amount of organic matter. Phenols content in water was increased as the upgrading temperature increased, and noticeably increased after300℃. The content of simple phenols accounts for approximately80%of total phenols. The content of o-cresol, m-cresol, p-cresol was m-cresol>o-cresol>p-cresol, out of accord with cresol dealkylation activity. The yield of phenol in water went up with the increase of upgrading temperature, however, the content of phenol in phenols did not show the same tendency. By analyzing the phenols composition and distribution in lignite-derived water, it was concluded that it was due to inadequte dealkylation of cresol and decomposition of reactive intermediate.5) Aspen Plus software was applied in this study, NRTL equation taken as property, and extraction model established, in order to absorb phenol capability in extraction process. Model parameter of NRTL was corrected by detailed data from phase balance experiment to improve the accuracy of simulation. The sensitivity was analyzed in terms of phase ratio, temperature, number of plates and plate efficiency. The results indicated that at the temperature of20℃, with the phase ratio of3:1and number of plates of3, phenol concentration of final water dropped enough to meet the requirement of biochemical treatment.6) Lignite briquetting experiment was conducted in a hydraulic press. Compaction curves of the lignites show that the whole compaction process can be divided into stages of densification, the particle re-arrangement stage, the plastic deformation stage and the whole deformation stage. Rosin-Rammler-Bennet equation (RRB) was used to describe particle size distribution. Uniformity index n and characteristic feature size De were also calculated. In addition, characterization of particle group, briquetting pressure, water content and upgraded coal content were the major factors that affect briquette strength.更多还原