ABSTRACT

The low-grade lignite reserve is large and it is an important basic material for coal gasification and liquefaction. However, it has high moisture content, high ash content, and low calorific value, and its use value is low without upgrading. The calorific value of lignite can be effectively improved by drying and dehydration. Meanwhile, due to the fine particle size of lignite powder, it is not convenient for storage and transportation, but it has certain utilization value. The efficient recovery and rational utilization of this part of the pulverized coal resources through coal powder briquetting increases its utilization value. In this paper, a study on the high-efficiency upgrading of low-grade lignite was carried out by using the combined process of multi-layer cross-flow drying and binderless pulverized coal briquetting. The migration and distribution law of lignite moisture in each drying bed was emphatically analyzed, and the influence of drying temperature and hot flue gas flow rate on drying effect under different treatment capacity was systematically studied. At the same time, the influence of coal powder with different particle size fraction on the briquetting load during the briquetting process and the influence of the −0.125 mm coal powder content on the quality of the briquetting product were analyzed. The drying and coal powder binderless briquetting test were carried out under the optimal parameters. The results show that the material moisture content decreases gradually from top to bottom along the bed height direction, and decreases gradually from the feed end to the discharge end for every layer. The dehydration rate is directly related to the feeding quantity. For the same drying temperature, the less the feeding quantity is, the lower critical point the optimal drying temperature reaches. During the binderless pulverized coal briquetting, as the briquetting load increases, the compressive strength of briquette products for different particle size fraction showed an increasing trend, while the falling strength increase firstly and then decreases. As the −0.125 mm fine coal content increases, the compressive strength increases, while the falling strength increases firstly and then decreases. The average drying temperature of hot flue gas is 200°C; the flow quantity of hot flue gas is 445–455 m³/h; the drying time is 12 minutes; the briquetting load is 120KN; the moisture content added is 12%. Under condition mentioned above, the moisture content of the dry lignite product is 9.75%; the ash content is 26.12%, and the calorific value is 23.47 KJ/g. For the briquetted lump coal, the total moisture content is 10.16%; the ash content is 25.78%; the calorific value is 23.21 KJ/g; the compressive strength is 2.56MPa and the falling strength is 93%.

摘要

低品位褐煤储量大，是煤气化、液化的重要基础原料。但其水分高、灰分高、热值低，不升级利用价值低。褐煤通过干燥脱水可有效提高热值。同时，由于褐煤粉粒度较细，不便于贮存和运输，但具有一定的利用价值。通过煤粉压块对这部分煤粉资源进行高效回收和合理利用，提高了其利用价值。【摘要】：采用多层错流干燥与无粘结剂煤粉压块联合工艺对低品位褐煤进行高效提质研究。着重分析了褐煤水分在各干燥床层中的运移分布规律，系统研究了不同处理量下干燥温度和热烟气流量对干燥效果的影响。同时分析了不同粒度级数的煤粉在压球过程中对压球负荷的影响以及-0.125 mm煤粉含量对压球产品质量的影响。在优化参数下进行了干燥和煤粉无粘结剂压块试验。结果表明，物料含水率沿床高方向自上而下逐渐降低，每层从进料端到出料端逐渐降低。脱水率与进料量直接相关。对于相同的干燥温度，进料量越少，最佳干燥温度达到的临界点越低。在无粘结剂煤粉压球过程中，随着压球负荷的增加，不同粒度级压球产品的抗压强度均呈上升趋势，而抗压强度则先上升后下降。随着-0.125 mm粉煤含量的增加，抗压强度增加，而抗落强度先增加后降低。热烟气平均干燥温度为200℃；热烟气流量445～455 m 在无粘结剂煤粉压球过程中，随着压球负荷的增加，不同粒度级压球产品的抗压强度均呈上升趋势，而抗压强度则先上升后下降。随着-0.125 mm粉煤含量的增加，抗压强度增加，而抗落强度先增加后降低。热烟气平均干燥温度为200℃；热烟气流量445～455 m 在无粘结剂煤粉压球过程中，随着压球负荷的增加，不同粒度级压球产品的抗压强度均呈上升趋势，而抗压强度则先上升后下降。随着-0.125 mm粉煤含量的增加，抗压强度增加，而抗落强度先增加后降低。热烟气平均干燥温度为200℃；热烟气流量445～455 m 而落下强度先增大后减小。热烟气平均干燥温度为200℃；热烟气流量445～455 m 而落下强度先增大后减小。热烟气平均干燥温度为200℃；热烟气流量445～455 m^3个/小时；干燥时间为12分钟；压块载荷为120KN；添加的水分含量为12%。在上述条件下，褐煤干品含水率为9.75%；灰分26.12%，热值23.47KJ/g。压块块煤总水分为10.16%；灰分25.78%；热值为23.21KJ/g；抗压强度2.56MPa，跌落强度93%。