洁净煤技术

2019, (04) 94-99

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环境湿度对煤粉吸水特性的影响
Effect of environmental humidity on the water absorption characteristics of pulverized coal

周沛然;
ZHOU Peiran

摘要(Abstract):

煤粉广泛应用于锅炉燃烧中,含水率过高会影响煤粉存储和锅炉生产安全。煤会吸附环境中的水分,为了研究环境湿度对煤粉吸水率的影响,选用3类不同变质程度的原煤制成煤粉,收到基煤粉为Ⅰ组,烘干外水后煤粉为Ⅱ组,共6个样品,在45%和70%两种环境湿度条件下研究了煤粉的吸水特性。45%和70%湿度时,Ⅰ组含水率曲线均为持续增加后出现下降拐点,再小幅上升直至基本稳定。Ⅱ组含水率曲线变化趋势则不同,45%湿度时,含水率一直上升直至稳定。70%湿度时,变化趋势为先增加而后出现下降拐点,再上升直至基本稳定。45%湿度时,3种煤粉出现拐点时含水率相比70%湿度时低4%~5%,主要是由于拐点产生的原因不同,45%环境湿度下出现的第一类拐点是由于氢键断裂导致煤粉对水产生解吸影响。70%环境湿度下出现的第二类拐点是因为煤粉吸附水后煤氧复合作用产生润湿热,样品自身水分蒸发的逸出量超过吸附量后产生的。2种湿度条件下,在吸附达到饱和后,Ⅱ组煤粉含水率均低于Ⅰ组煤粉,是由于干燥煤样时,发生了一定程度的提质改性,同时孔隙结构会有少量坍塌破坏,煤的疏水性增加,导致干燥基吸附平衡时含水率低于收到基。Ⅱ组的绝对吸水量和吸水速率均高于Ⅰ组,是由于环境水蒸气与烘干煤自身毛细管压差大于Ⅰ组造成的。70%湿度时的吸附水量和吸附速率均高于45%湿度时,其余试验条件均基本相同,是因为湿度大时水蒸气分压力大,水蒸气更易被煤粉吸附,更易主动进入煤粉内部结构中,说明环境湿度是影响煤粉吸附水量和速度的一个重要因素。最后还比较了不同变质程度煤粉对水的吸附情况,由于低阶煤表面静电势和活性官能团多于高阶煤,故而吸水性能强于高阶煤,在45%环境湿度时,环境蒸气压与3种煤粉毛细管压力相差不大,故而吸附量较小且相差不大;在70%环境湿度时,该规律表现较为明显。
Pulverized coal is widely used in boiler combustion.The high moisture content will affect the safety of pulverized storage coal and boiler production.Coal adsorbs the moisture in the environment.In order to study the influence of environmental humidity on water absorption of pulverized coal,the three kinds of raw coal with different metamorphic degree were selected to prepare pulverized coal.The samples were divided into two groups,the group I was the basic pulverized coal,and the group II was dry coal,and a total of six samples were collected.The water absorption characteristics of pulverized coal were studied under the conditions of 45% and 70% ambient humidity.At 45% and 70% ambient humidity,the water content curve of group I shows a downward inflection point after continuous increase,then rises slightly until it is basically stable.The trend of water content curve in group II is different under two humidity.At 45% ambient humidity,the moisture content of pulverized coal in group II rises until it is stable.At 70% ambient humidity,the trend of change is to first increase,then declines inflection point,and then rises until it is basically stable.At 45% ambient humidity,the water content of three kinds of pulverized coal at inflection point is 4%-5% lower than that at 70% ambient humidity,mainly due to the different reasons of inflection point.The first inflection point at 45% ambient humidity is the desorption effect of pulverized coal on water due to hydrogen bond breakage.The second inflection point at 70% ambient humidity is due to the wetting heat generated by the combined action of coal and oxygen after coal powder adsorbing water.The amount of evaporation from the sample itself exceeds the amount of adsorption.Under two humidity conditions,the moisture content of pulverized coal in group II is lower than that of pulverized coal in group I after the adsorption reaches saturation.The reason is that when the dry coal sample is dried,a certain degree of upgrading and modification has taken place.At the same time,the pore structure will collapse a little,and the hydrophobicity of the coal will increase,resulting in that the moisture content of the dry base is lower than that of the received base when the adsorption equilibrium is reached.The absolute water absorption and water absorption rate of group II are higher than those of group I,because the difference of capillary pressure between ambient water vapor and drying coal is greater than that of group I.When the amount of water adsorbed and the rate of adsorption at 70% humidity are higher than those at 45% humidity,the other experimental conditions are basically the same,because when the humidity is high,the partial pressure of water vapor is high,the water vapor is more easily absorbed by pulverized coal,and it is easier to actively enter the internal structure of pulverized coal,indicating that environmental humidity is an important factor affecting the amount and speed of water adsorbed by pulverized coal.At last,the water adsorption of pulverized coal with different metamorphic degree is compared.Because the surface electrostatic potential and active functional groups of low rank coal are more than those of high rank coal,the water absorption performance of low rank coal is stronger than that of high rank coal.When the ambient humidity is 45%,the ambient vapor pressure is not different from the capillary pressure of three kinds of pulverized coal,so the adsorption capacity is small and there is little difference At 70% environmental humidity,the law is more obvious.

关键词(KeyWords): 煤粉;吸水;氢键;环境湿度
pulverized coal;water absorption;hydrogen bond;environmental humidity

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作者(Author): 周沛然;
ZHOU Peiran

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