Pore structure characteristics are significant factor in the evaluation of the physical characteristics of low-rank coal. In this study, three low-rank coal samples were collected from the Xishanyao Formation, Santanghu Basin, and low-temperature liquid-nitrogen adsorption (LP-N₂A) measurements were taken under various pretreatment temperatures. Owing to the continuous loss of water and volatile matter in low-rank coal, the total pore volume assumes a three-step profile with knee temperatures of 150 °C and 240 °C. However, the ash in the coal can protect the coal skeleton. Pore collapse mainly occurs for mesopores with aperture smaller than 20 nm. Mesopores with apertures smaller than 5 nm exhibit a continuous decrease in pore volume, whereas the pore volume of mesopores with apertures ranging from 5 to 10 nm increases at lower pretreatment temperatures (<150 °C) followed by a faint decrease. As for mesopores with apertures larger than 10 nm, the pore volume increases significantly when the pretreatment temperature reaches 300 °C. The pore structure of low-rank coal features a significant heating effect, the pretreatment temperature should not exceed 150 °C when the LP-N₂A is used to evaluate the pore structure of low-rank coal to effectively evaluate the reservoir characteristics of low-rank coal.

孔隙结构特征是评估低阶煤物理特征的重要因素。在这项研究中，从三塘湖盆地西山窑组收集了三个低品位煤样品，并进行了低温液氮吸附（LP-N ₂A）在各种预处理温度下进行测量。由于低阶煤中水和挥发物的不断损失，总孔隙体积呈三个步骤，拐点温度分别为150°C和240°C。但是，煤中的灰分可以保护煤骨架。孔径崩溃主要发生在孔径小于20 nm的中孔中。孔径小于5 nm的中孔表现出孔体积的连续减小，而孔径在5到10 nm范围内的中孔的孔体积在较低的预处理温度（<150°C）下增加，随后逐渐减少。对于孔径大于10 nm的中孔，当预处理温度达到300°C时，孔体积会显着增加。低阶煤的孔隙结构具有明显的加热作用，₂ A用于评价低品位煤的孔隙结构，有效评价低品位煤的储层特征。