阻化剂防灭火技术在我国煤矿中应用广泛，但常见的矿用阻化剂存在作用手段单一、易失效、阻化效果弱的缺点。本文制备了以羟乙基纤维素(HEC)、甲基纤维素(MC)和纳米二氧化硅(CSPs)为原料的纳米复合水凝胶(NCH)，作为复合阻化剂的物理阻化部分；优选出抗氧化剂(AO)白皮杉醇作为化学阻化部分，复配了不同比例的复合阻化剂(AO-NCH)。采用理论分析、实验测试和数学计算的方法研究AO-NCH的防灭火特性、优选AO-NCH的配比、掌握AO-NCH对煤自燃过程中活性官能团变化的影响规律、揭示AO-NCH阻化煤自燃的作用机理。

采用溶液共混法制备了非共价相互作用驱动的NCH，以成胶时间和状态为依据初步筛选出适合防灭火的凝胶配比，通过热稳定性、渗透性及封堵性测试进一步确定各配比凝胶的基础性能，最终选择成胶时间为12 min的凝胶作为阻化凝胶(HEC:MC:CSPs=0.75wt%:0.25wt%:5wt%)，成胶时间为2.5 min的凝胶作为灭火凝胶(HEC:MC:CSPs=1.25wt%:1.25wt%:5wt%)，与白皮杉醇复配形成AO-NCH开展防灭火特性研究。

通过同步热分析实验和程序升温实验得到了AO、NCH及不同配比的AO-NCH对煤自燃过程热特性及煤低温氧化特性的影响。与原煤相比，阻化煤的特征温度明显增大，其中NCH和AO对失水结束温度T₁与质量峰值温度T₂具有较为明显的提高作用，AO-NCH(40%:60%)表现出了优于单一阻化剂的阻化效果；阻化煤的最大质量损失率、平均质量损失率、可燃性指数及综合燃烧特性指数均低于原煤，其中AO-NCH(40%:60%)对煤自燃的前期反应能力抑制效果最佳，AO-NCH(50%:50%)对整体氧化燃烧性能具有最明显的抑制效果；阻化剂增大了原煤热平衡温度与最大放热功率温度，增加了煤自燃过程中的吸热量并减少了放热量；阻化煤样在氧化升温过程中具有比原煤更低的CO生成浓度、C₂H₄生成浓度、耗氧速率以及更高的表观活化能，但过高的AO含量或NCH含量均会导致阻化率及表观活化能的降低。其中AO-NCH(40%:60%)对原煤低温氧化过程的抑制效果最为明显，AO-NCH(40%:60%)阻化煤的表观活化能和平均阻化率最大。因此选用AO:NCH=40%:60%作为阻化煤自燃的最佳复配比例。

利用小型灭火试验台测试了AO-NCH的灭火性能，AO-NCH成胶前具有的流动性能保证了其在破碎煤体间的扩散，与高温火源接触后产生的水蒸气相对量小、安全性好；扩散过程中交联程度的加深使其能够有效粘附于煤体，覆盖煤体表面、封堵漏风通道，材料流失量少；优异的性能使煤温从783℃降低至50℃左右且未发生复燃。

利用原位漫反射红外光谱实验研究了原煤及AO-NCH(40%:60%)阻化煤氧化过程中的活性官能团变化规律，结果表明AO-NCH(40%:60%)可以有效减缓羟基的消耗趋势，抑制羟基、羧基、羰基及脂肪烃官能团的增长趋势，增加稳定醚键的生成速率。这意味着AO-NCH可以通过惰化活性中心、隔氧吸热的方式抑制煤氧反应，实现协同阻化煤自燃。

The fire retardant prevention technology is widely used in China's coal mines, but the common mining retardants have the disadvantages of single means of action, easy failure and weak retarding effect. In this paper, a nano-composite hydrogel (NCH) with hydroxyethyl cellulose (HEC), methyl cellulose (MC) and nano-silica (CSPs) was prepared as the physical inhibiting part of the composite retardant; the antioxidant (AO) piceatannol was preferably selected as the chemical inhibiting part, and different ratios of the composite retardant (AO-NCH) were compounded. Theoretical analysis, experimental tests and mathematical calculations were used to study the fire-fighting properties of AO-NCH, to optimize the proportion of AO-NCH, to grasp the influence law of AO-NCH on the change of active functional groups during coal spontaneous combustion, and to reveal the mechanism of the effect of AO-NCH in inhibiting coal spontaneous combustion.

Non-covalent interaction-driven NCH was prepared by solution blending method, and suitable gel ratios were initially screened on the basis of gel formation time and state, and the basic properties of each ratio were further determined by thermal stability, permeability and blockability tests. The gel with a gel formation time of 12 min was finally selected as the inhibiting gel(HEC:MC:CSPs=0.75wt%:0.25wt%:5wt%), and the gel with a gel formation time of 2.5 min was selected as the fire suppression gel(HEC:MC:CSPs=1.25wt%:1.25wt%:5wt%). AO-NCH was formed by compounding NCH and piceatannol and the study of fire-fighting properties was carried out.

The effects of AO, NCH and AO-NCH on the thermal characteristics of coal spontaneous combustion process and the low temperature oxidation characteristics of coal were obtained by simultaneous thermal analysis experiments and temperature-programmed experiments. The retardant effectively increased the characteristic temperature of the raw coal, among which NCH and AO had more obvious effects on the water loss end temperature T₁ and mass peak temperature T₂, respectively. Furthermore, AO-NCH (40%:60%) showed better inhibiting effects than single retardant. The maximum mass loss rate, average mass loss rate, combustion characteristics index of the inhibited coal were lower than those of the raw coal, among which AO-NCH (40%:60%) and AO-NCH (50%:50%) had the most obvious inhibition effects on the pre-combustion reactivity and the overall oxidative combustion performance of the coal, respectively.The retardant increased the thermal equilibrium temperature and the maximum exothermic power temperature of the raw coal, increased the heat absorption and reduced the exothermic heat in the process of spontaneous combustion. The inhibited coal has lower CO generation concentration, C₂H₄ generation concentration, oxygen consumption rate and higher apparent activation energy than the raw coal, but too high AO or NCH content will lead to the decrease of inhibiting rate and apparent activation energy. Among them, AO-NCH (40%:60%) has the most obvious inhibiting effect on the low-temperature oxidation of raw coal, and has the highest apparent activation energy and inhibiting rate. Therefore, AO:NCH=40%:60% was selected as the best compounding ratio for inhibiting coal spontaneous combustion.

The fire extinguishing performance of AO-NCH was tested by a small fire extinguishing test bench. The fluidity of AO-NCH before gel formation ensures its diffusion among broken coal bodies, and the relative amount of water vapor generated after contacting with high temperature fire sources is small and safe. The deepening of cross-linking in the diffusion process enables it to adhere to the coal body effectively, covering the surface of the coal body and sealing the air leakage channels with less material loss. The excellent performance reduces the coal temperature from 783℃ to about 50℃ without re-ignition.

The changes of active functional groups during the oxidation of raw coal and AO-NCH (40%:60%) inhibited coal were investigated by in situ diffuse reflectance infrared spectroscopy experiments, and the results showed that AO-NCH (40%:60%) could effectively slow down the consumption trend of hydroxyl groups, inhibit the growth trend of hydroxyl, carboxyl, carbonyl and aliphatic hydrocarbon functional groups, and increase the generation rate of stable ether bonds. This implies that AO-NCH can inhibit the coal oxygen reaction by inerting the active center and isolating oxygen and absorbing heat to achieve synergistic deterrence of coal spontaneous combustion.

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