【作者】 吴波；

【导师】 胡浩权；

【作者基本信息】 大连理工大学 ， 化学工艺， 2009， 博士

【摘要】 本文以研究西部弱还原性煤一神东煤的热解特性为目的,分别采用热重（TG）和热重-质谱（TG-MS）、固定床热解装置和半连续式亚临界和超临界萃取装置等实验设备进行研究,考察其在不同装置上的产物分布规律以及实验条件对产物分布规律的影响,并对亚临界和超临界萃取所得残渣的性质进行分析;以还原性的平朔煤作为参比对象,比较性地探讨了具有不同还原性的两种煤的热解特性。论文的主要研究内容和结果如下:在热重分析装置上,研究两种煤的非等温热解规律,考察了升温速率对热解过程的影响,并进行了热解动力学分析。研究结果表明:神东煤的主要热解温度区间为365-650℃,最大失重速率峰出现在450℃左右;与平朔煤相比,神东煤具有较大的总失重量、较小的最大失重速率以及较低的最大失重速率所对应的温度,最大不同在于神东煤在600-700℃有一明显失重峰;升温速率提高,最大失重速率所对应的温度向高温区移动;动力学分析表明,神东煤热解活化能（118-265kJ/mol）明显低于平朔煤热解活化能（196-280kJ/mol）。在热重-质谱联用装置上,考察了两种煤热解逸出物的逸出规律。研究结果表明:在600-700℃之间,神东煤的H₂和CO₂的逸出强度均要高于平朔煤,说明神东煤在600-700℃的失重峰是神东煤的二次热解和其矿物质组分中碳酸盐部分的热分解共同造成的。由低分子碳氢化合物的逸出规律可知,与平朔煤相比,神东煤在主要分解温度段的热解强度要弱些。平朔煤热解气体中的H₂S主要是由煤大分子结构中的含硫键断裂形成的,平朔煤热解气体中的SO₂是由有机硫的逸出和硫铁矿的分解共同造成的:神东煤的热解气体中的H₂S和SO₂主要是由煤中铁铁矿的分解生成的,少部分的SO₂是由有机硫的逸出生成的。在固定床热解装置上,考察了两种煤热解和加氢热解过程中温度对产物分布规律的影响,并对所得半焦的性质进行了分析。结果表明:神东煤氮气气氛下焦油产率呈现随温度提高先增加后减小的趋势,在650℃时达到最大值10.5%:在加氢热解条件下,则呈缓慢近线性增大的趋势,在700℃时达到最大值12.1%;无论氮气还是氢气气氛,平朔煤热解的焦油产率均呈现先增加后减小的趋势,均在650℃附近达最大值,分别17.1%和19.8%,均高于神东煤;两种煤热解和加氢热解所得气体的逸出规律相近,但神东煤的气体生成总量稍高于平朔煤;两种煤的半焦产率都随着温度升高而降低,相同终温下,神东煤的半焦产率大于平朔煤的半焦产率。在半连续式亚临界和超临界萃取装置上,考察了两种煤在不同溶剂和不同压力下的产物分布规律。研究结果表明:以水为溶剂时,随着压力的升高,液体产率增加,30MPa时,平朔煤和神东煤的液体产率分别为21.3%和16.3%;两种煤液体产物中主要组分均为沥青烯,但神东煤液体产物具有相对较高的油组分,随着温度的增加,液体产物生成速率先增大,在400℃左右出现峰值后再降低;随着压力的增加,液体产物最大生成速率所对应的温度向高温区移动,与平朔煤相比,神东煤具有较低的液体最大生成速率和与之相对应的温度;两种煤气体产率也随着压力的增加而稍有增大,神东煤比平朔煤有更高的气体产率,平均高3%左右,气体组成中H₂、CH₄和CO₂是主要成分;残渣产率为65%-75%,并随着压力的增加而减小,神东煤具有比平朔煤低的残渣产率。以甲苯为溶剂时,液体和气体产物随温度和压力的变化所呈现的规律与以水为溶剂时大体相似,不同的是在变化幅度和具体组成上。30MPa时,平朔煤和神东煤液体产率分别为35.3%和33.8%,液体产物的主要成分为油组分,与以水为溶剂时的结果相比,液体产物在相对较宽的温度范围生成,但最大生成速率变小,最大生成速率对应的温度提高;神东煤的气体产率高于平朔煤,主要气体成分为H₂和CH₄;残渣产率为70%-80%,神东煤比平朔煤具有较高的残渣产率。当以甲苯和四氢萘（9:1,V/V）的混合物为溶剂时,液体产率仍随着反应压力的增加而增大,30MPa下,平朔煤和神东煤的液体产率分别为68.2%和64.0%,油是液体产物的主要成分,其中很大部分液体产物来自于溶剂的反应;液体产物生成速率在低压时随温度的变化规律与以水和甲苯为溶剂时相似,高压时则随着温度的升高而不断增大。在气体产率和组成上,与以甲苯为溶剂时相似,但H₂含量有所增加。残渣产率为65%-75%,神东煤比平朔煤具有较低的残渣产率。对两种煤在不同溶剂下亚临界和超临界萃取所得的残渣进行了煤质分析、红外光谱分析和燃烧反应实验。结果表明:以水为溶剂所得残渣与原煤相比,几乎不含水分,具有较高的灰分、较低的挥发份;C元素含量增加,H、O元素含量降低,具有较高的发热量;与平朔煤残渣相比,神东煤残渣有较高的C、N含量,具有略低的挥发份和较低的灰分。通过对原煤与萃取残渣的红外光谱的对比分析发现:大部分的矿物质并未参与到萃取过程中。以水为溶剂得到的神东煤残渣的发热量高于平朔煤残渣,且更容易反应和燃烧,燃烧反应符合一级反应;甲苯为溶剂和采用混合溶剂时所得残渣表现出与以水为溶剂时相似的规律,只是在幅度和具体数值上有所差别。对以水为溶剂所得残渣进行了氮吸附和XPS分析,考察亚临界和超临界萃取对煤结构和表面元素赋存状态的影响。研究结果显示:残渣的平均孔径与原煤相比减小,比表面积有较大增加,且随着反应压力的增加而增大,说明亚临界和超临界水萃取对于煤具有一定的活化作用。神东煤残渣具有较大的比表面积和较小平均孔径,具有一定的中孔材料特征。原煤与残渣的表面C的主要赋存状态为C-C,神东煤相对于平朔煤具有较高的C-C和较低的C-H赋存比例;原煤与残渣的表面O的主要赋存状态为C-O;吡啶型氮（N-6）和吡咯型氮（N-5）是原煤表面N的主要赋存形式,吡啶型氮（N-6）是残渣表面N的主要赋存形式。更多还原

【Abstract】 In this paper, pyrolysis performance of a weakly reductive Shendong （SD） coal was investigated by using thermogravimetric analyzer （TG）, thermogravimetric analyzer - mass spectrometer （TG-MS）, a fixed bed reactor and a semi-continuous apparatus with sub- and supercritical solvent. The characteristic of residues from coal extraction with sub- and supercritical solvent was also characterized by different methods. Pingshuo （PS） coal, a reductive coal was used as reference coal in comparison with SD coal. Main research works and results are as follows:Kinetic characteristics of two coals during pyrolysis were investigated by TG. The results showed that the pyrolysis of SD coal mainly takes place in the temperature range between 365 and 650℃. The temperature corresponding to the maximum weight loss rate appears at about 450℃. In comparison with PS coal, SD coal has a high weight loss and low temperature corresponding to the maximum weight loss rate and another peak of weight loss rate appears at the temperature between 600 and 700℃. with the increase of heating rate, the temperature corresponding to the maximum weight loss rate shifts to high temperature. Activation energy of SD coal and PS coal during pyrolysis at the temperature of 300-650℃are 118-265kJ·mol^-1 and 196-280kJ·mol^-1, respectively.TG-MS was used to investigate the pyrolysis behaviours of two coals. The results showed that The evolution intensity of H₂ and CO₂ from SD coal is higher than that from PS coal between 600 and 700℃.It means that weight loss peak of SD coal between 600-700℃is attributed to the second reaction of the pyrolysis product and the mineral matter decomposition. The H₂S evolution of PS coal mainly comes from the rupture of sulfur containing bond in coal macromolecule. The SO₂ evolution of PS coal attributed to decomposition of pyrite and the evolution of organic sulfur. The H₂S and SO₂ evolution of SD coal mainly attributed to decomposition of pyrite, and partly come from the evolution of organic sulfur.The effect of end temperature on product distribution of two coals was investigated in a fixed bed reactor under N₂ and H₂ atmosphere. With the increase of the temperature, the tar yield of SD coal increases, gets a maximum and then decreases with further increase of the temperature under N₂ atmosphere. The maximum, 10.5%, appears at about 650_. Under H₂ atmosphere, the tar yield of SD coal increases with a increasing of the temperature. The maximum, 12.1%, appears at about 700℃. The tar yield of PS coal has a similar trend as that of SD coal pyrolysis under both N₂ and H₂ atmosphere. The maximum, 17.1 % and 19.8%, respectively, appears at about 650℃, higher than that of SD coal. The gas evolution rule of two coals during pyrolysis and hydropyrolysis shows a similar trend. The total gas volume of SD coal is higher than that of PS coal. The char yield of two coals decreases with an increase of the temperature. At the same final temperature, the char yield of SD coal is higher than that of PS coal.On a semi-continuous apparatus, SD coal and PS coal were non-isothermally extracted with sub- and supercritical solvent to explore the differences between the two coals. The effect of temperature on extract formation rate, conversion and product composition under different pressures was investigated. Water, toluene, and toluene-tetralin （9:1, V/V） were used as solvent. When the solvent is water, the results indicate that the liquid formation rate of two coal samples increases to a maximum at temperature about 400℃and then decreases with further increase of the temperature. With increasing pressure, the liquid yield increase. At a pressure of 30MPa, the liquid yield of SD coal and PS coal is 16.3% daf, 21.3% daf respectively. The conversion and the liquid formation rate also increases and the temperature corresponding to maximum of liquid formation rate moves to higher temperature. In comparison with PS coal, SD coal has high conversion, low liquid yield and low temperature corresponding to the maximum formation rate: The main fraction in liquid product from PS coal is asphaltene, while that from SD coal has relatively higher content of oil fraction. The yield of gas formed during coal extraction increases with the increase of the pressure and the main gas components are CO₂, CH₄ and H₂. In comparison with PS coal, SD coal has a high gas yield. The main product in coal extraction is extraction residue, about 65-75% of coal. SD coal has lower residue yield than PS coal.When the toluene is solvent, the results indicate that the rule of the liquid and gas product with the change of the temperature and pressure is similar with that using water as solvent. The difference is the change intensity and composition. For example, the liquid yield of PS coal is 35.3% daf and that of SD coal is 33.8% daf at the pressure of 30MPa. The main fraction in liquid product from two coals is oil. The liquid formation rate and the maximum liquid formation rate are smaller than that using water as solvent, while the temperature corresponding to the maximum liquid formation rate is higher than that using water as solvent. SD coal has higher gas yield than PS coal, although the main gas components change to CH4 and H₂. About 70-80% of coal became the extraction residue. SD coal has higher residue yield than PS coal. When the toluene-tetralin （9:1, V/V） is used as solvent, the results indicate that with increasing pressure, the liquid yield increase. At a pressure of 30MPa, the liquid yield of SD coal and PS coal is 64.0% daf, 68.2% daf respectively. The main fraction in liquid product from two coals is also oil. The liquid formation rate under the low pressure has the similar as that using water and toluene as solvent, while that under the high pressure increases with an increase of the temperature. The main gas components are CH₄ and H₂, although the content of H₂ has a small increment. About 65-75% of coal became the extraction residue. SD coal has lower residue yield than PS coal.The residues, obtained from extraction of SD coal and PS coal with sub- and supercritical solvent were characterized by proximate analysis, ultimate analysis, calorific value analysis, FTIR analysis and combustion experiment. The results indicate that the residues from the extraction of two coals with sub- and supercritical water have higher carbon content, lower hydrogen, oxygen content and higher calorific value than coal samples. In compared with the extraction residues of PS coal （PSER）, the extraction residues of SD coal （SDER） has a high calorific value and carbon, hydrogen content and a low volatile matter and ash yield. The results of the FT-IR comparison between raw coal and the extraction residues indicate that the main part of mineral matter is not involved in extraction. The results of combustion indicate that the extraction residues of SD coal are more reactive and can be more easily burned than that from PS coal. The characteristics of the residues using the toluene and toluene-tetralin （9:1, V/V） as solvent have the similar trend, the difference is the change intensity and the actual value.The residues from extraction of two coals with sub- and supercritical water were characterized by XPS analysis and N₂ adsorption. The results indicate that the average pore diameter has a decrease after extraction, and the surface area of residue becomes larger with the increase of pressure. The sub- and supercritical water extraction has an activation effect to the samples, although this effect is limited. In compared with PSER, SDER have high surface area and small average pore diameter, which shows the character of mesopore materials. C-C and C-0 are the main form of carbon, oxygen element on the surface of coal samples and extraction residues. Pyridinic nitrogen （N-6） and pyrrolic nitrogen （N-5） are the main form of nitrogen element on the surface of coal samples. Pyridinic nitrogen （N-6） is the main form of nitrogen element on the surface of extraction residues. In comparison with PS coal, SD coal has a high C-C content and a low C-H content.更多还原