【作者】 万永周；

【导师】 刘炯天； 陶秀祥；

【作者基本信息】 中国矿业大学 ， 化学工艺， 2012， 博士

【摘要】 褐煤是煤化程度最低的煤种之一，具有高水分、低热值的特点。随着世界范围内能源资源需求的增加，以及石油、优质煤资源等能源资源的逐渐匮乏，储量丰富的褐煤资源已引起人们的关注。褐煤热压脱水工艺，水分以液态形式脱水，产品能级密度得以明显提高，且具有不易吸潮、自燃，煤质性能明显改善等优点。本文以云南小龙潭等高水、低热值褐煤为主要研究对象，对褐煤热压脱水过程机理、褐煤热压型煤稳定机制及热压脱水工艺过程等进行了研究。本论文主要包括以下内容及结果：褐煤原煤煤质分析结果表明，原料褐煤孔隙结构发达，氧含量较高，具有大量的含氧官能团结构，易吸湿返潮、自燃，其挥发分初析温度在222℃左右。褐煤热压脱水机理研究结果表明，热压过程中煤水分离的基本过程为温度引起的热力效应脱水、机械压力产生的压实固结脱水和闪蒸脱水三方面；其机制是褐煤在热力作用下其有机含氧官能团和有机结构发生分解等引起褐煤物理结构和化学结构及组成的改变，煤水体系作用力减弱，借助于褐煤本身体积收缩、释放气体的排水作用及压力的压密固结作用等实现煤水体系的彻底分离。结合热压脱水过程基本特点，根据已有固结理论对热压过程进行了模型推导，建立了包含热压压力、温度和煤质特性因素的模型方程，模型方程进一步揭示并反映了热压过程热态固结脱水的特点。对小龙潭褐煤无粘结热压型煤稳定机制进行了研究，在分析热压型煤稳定性的同时，从褐煤样品表观形态、总孔容与稳定性关系及物理化学性能变化角度对热压型煤的稳定性机制进行了分析。热压过程中褐煤内部及表面含氧亲水基团的减少、疏水性增强，及孔隙、总孔容的大幅降低，内部结构的规整和热压作用引起的型煤表面的炭化作用是热压型煤稳定的基本原因。实验条件下，经干燥褐煤吸水率达9%以上，而型煤产品吸水率在4%左右，二者相差达5个百分点；褐煤经热压成型后，其自燃倾向性降低，自燃倾向性等级从Ⅰ级容易自燃变为Ⅱ级自燃倾向性等级。论文对100kg/d规模褐煤热压脱水工艺过程进行了研究。结果表明，温度、压力和保压时间是褐煤水分含量的显著性影响因素，其中温度和压力是褐煤热压脱水过程中关键因素，二者间交互作用对褐煤水分含量影响显著；热压过程适宜的工艺参数应根据对褐煤产品水分含量的要求确定，适宜的温度压力范围分别为150-200℃和5-10MPa，保压时间1-5min；上述极值条件下，褐煤水分含量可分别降至24.8%和8.78%。对热压产品煤质分析结果表明，脱水后褐煤能级密度得到大幅提升，小龙潭褐煤干基发热量增幅最大可达37%以上；同时，元素组成中碳含量可提升9%，而氧和硫元素含量明显降低；热压过程对褐煤具有一定的“洗涤”作用，其Na、Mg、Ca等金属元素含量较原煤有明显降低；Cl、Ni、As等元素含量也有所降低；热压处理后煤样挥发分、最高内在水分的大幅降低及固定碳含量的升高，反映热压过程对褐煤煤化程度具有一定的提升作用。对热压产品的热重实验结果表明，相较原煤，煤样挥发分初析温度、着火温度及最大失重速率温度均有明显提高，而燃尽温度变化不大，说明褐煤经热压后热稳定性的提高及燃烧性能的改善。基于获得200℃、10MPa条件下褐煤产品的热压脱水过程，对所需基本理论能耗进行了分析计算，结果表明其理论能耗大约为1195.7kJ/kg，按褐煤原煤热值及价格折合为17.52元/t。即热压脱水过程能耗成本为17.52元/t。该论文有图75幅，表31个，参考文献165篇。更多还原

【Abstract】 Lignite is one kind of low rank coal, and has the characteristics of high innerwater and low heat value. With the worldwide increase in demand for energyresources, and gradual lack of oil, high rank coal, the abundant lignite resources haveattracted ever-increasing attentions. The Hot-pressing Dehydration (HPD) technologyhas the advantages that the water in lignite can be removed in liquid form, and theproduct from HPD has higher heat value, and an improved performance for utilizationwith the stability of not easily reabsorb moisture and spontaneous combustion. XiaoLongtan lignite (XLT) Adopted as raw material, the mechanism of dewatering of HPD,and the process parameters and the mechanism of the stability of briquette from HPDwere studied. The paper includes the followings:Some properties of raw lignite were analyzed. The results show that XLT ligniteis rich in pore structure and oxygen-containing functional group structure, and hashigher oxygen element content, and is easy to reabsorb moisture and prone tospontaneous combustion, and the volatile initial escaping temperature is about220℃.The mechanisms of dewatering of lignite by HPD were explored. The basicprinciple of water removal in PHD is thermal effect, compacting consolidation, andflash evaporation. The underlying dewatering mechanism is that the changes inphysical＆chemical properties owing to the organic groups decomposition caused bythermal effect, which weakening the force between coal and water system, creatingthe conditions for the separation of water from lignite; then, the moisture is removedcompletely from coal by the volume contraction of lignite and the drainage effect ofgas from organic decomposition and the effect of compacting consolidation caused bymechanical press. On the basis of the HPD process feature, the model of HPD processwas created on the theory of consolidation, in which the factors of temperature,pressure and coal property are included.The mechanisms of the stability of lignite briquette from HPD were studied. Thestability of lignite briquettes were analyzed, and the mechanisms of the stability wasrevealed through the studies on the apparent morphological, and the relations betweentotal pore volume and stability, and the changes in physical＆chemical properties.Which the significant decreases of oxygen content and the increase of hydrophobicityof lignite, and the significant reduction of porosity and total pore volume, and thesome degree carbonizing of briquette surface are the underlying reasons. At the conditions of test, the reabsorbed moisture difference between dried lignite from dryerand dewatered lignite from HPD is5percent, respectively are9percent and4percent.The grade of spontaneous combustion of the coal briquetted changes from Ⅰgrade toⅡgrade.Dewatering of lignite by HPD technology in a100kg/h scale was studied. Itshows that the significant factors effecting on dewatering of lignite are temperature,pressure and pressing time, and the factors of temperature and pressure and theirinteraction are the key to the water removal; suitable conditions parameters aredepended on the demand for the water content in lignite, and can be in the ranges oftemperature150-200℃, pressure5-10MPa and pressing time1-5min. The productsproperties were analyzed, and it shows that the heat density can be significantlyincreased by above37percent; and the carbon element content has been increased by9percent, and oxygen and sulfur elements content decreased significantly in theprocess; the process has some purification on some soluble metal ions with the ion Na,Mg, Ca content significantly reduction and Cl, Ni, As some degree reduction; the coalrank can be upgrade by HPD reflecting in the notable reduction of MHC and volatilecontent, and the fixed carbon content increased significantly; and the volatile initialescaping temperature, burning temperature and the fastest burning temperature can beraised, while burning out temperature changes little, which illustrates the rise ofstability and the improvement of burning performance.Based on obtained product from the HPD process conditions of temperature200℃, pressure10MPa, the theory energy consumption were calculated and discussed,and it gives the1195.7kJ theory energy consumption per kilogram product, and itequals to17.52Yuan per ton(base on the price of raw lignite price). That the cost ofenergy to process1ton raw lignite is17.52Yuan.75figs.,31tabs.,165refs.更多还原