现有的煤自燃反应模式中,煤直接氧化和煤氧吸附分解两个序列已得到证实,但其能否全面反映煤自燃过程仍存在质疑。基于这一现状,对煤中活性基团的氧化与自反应过程进行了研究。采用傅里叶变换红外光谱技术分析了不同变质程度原始煤样中基团的基本情况,从含氧基团、烷基侧链、含硫基团等类别分别对煤中原生和次生活性基团进行了分析,明确了煤中基团的分布情况。系统测试了活性基团在不同条件下的实时变化情况,从微观上论证了活性基团的自反应。采用红外光谱原位测试技术,以内置反应池为煤样载体,通过外置供气系统和控温装置模拟不同的反应条件,实时测试了供氧、无氧和无氧反应后供氧等条件下煤反应升温过程30～220℃范围内的红外光谱。研究表明：供氧反应过程中,低阶煤中活性基团在初始阶段存在先减后增现象,不同基团的拐点温度差别较大,其中,较低者40～50℃,较高者130～140℃;无氧反应过程的变化趋势与供氧反应类似,但基团数量减小25%～80%,拐点温度约降低10℃;无氧反应后煤样的供氧反应过程中,活性基团的初期减小现象基本消失。上述变化规律表明部分活性基团可在无氧条件下自发反应。供氧和无氧反应过程初期,煤中原生活性基团因反应被消耗,而次生活性基团的生成又存在滞后性,导致活性基团总量的暂时性减小;而在无氧反应后的供氧反应过程中,大部分原生活性基团已在无氧反应中被消耗,后续供氧反应过程的原生活性基团自反应较弱,基团总量随次生基团产生而逐渐增多,初期减小现象消失。为了进一步证实煤中活性基团的自反应,采用色谱分析技术对供氧、无氧、无氧反应后供氧等3种条件下活性基团反应过程的产物进行了研究。结果表明：3种条件下煤中活性基团的反应过程均能产生不同种类的产物;供氧条件下的产量和增速最大,无氧条件下的产量和增速最小,无氧反应后供氧条件下的产量和增速与直接供氧相比均有不同程度的减小;煤中活性基团的自反应能够生成各类产物,但其反应强度明显小于供氧反应。在证实煤中活性基团自反应的基础上,提出了煤自燃过程的三序列反应模型,认为除已被验证的煤直接氧化和煤氧复合分解反应外,煤自燃过程还存在活性基团的自反应,并推导出了CO、CO2、H2O等主要产物的形成过程,指出煤中原生和次生的羰基、羧基和羟基分别是其形成的主要物质基础,阐明了煤自燃过程的反应模式。煤自燃实质上是活性基团氧化反应与自反应共同作用的结果,两者之间共生互存、相互促进;但活性基团的自反应无法孤立存在,它需要氧化反应放出的热量作为原始促动力。采用活性基团的氧化与自反应理论阐释了煤自燃过程的部分宏观特性。由于煤自热初期只有原生活性基团和少量次生活性基团参与反应,反应强度小,而后期大量次生活性基团生成并迅速发生链式反应,反应强度迅速增加,导致煤自热过程的分段性;高阶煤中原生活性基团较少,且次生活性基团较难生成,低温反应初期（30～50℃）的基团总量呈减小趋势,导致高阶煤在该阶段的耗氧速率相应减小;水分抑制了活性基团的运移和热量传递,降低了活性基团接触反应的几率,导致高水分煤的反应升温过程存在延滞效应;低温干燥条件下,难反应的含硫结构覆盖在煤粒表面,阻碍了活性基团的接触反应和热量传递,一定程度上抑制了活性基团反应。%The direct burn-off of coal and sorption reaction sequences between coal and oxygen had been confirmed to occur in this phenomenon.However,whether the two squences can comprehensively reflect spontaneous combustion of coal is still being suspected.The dissertation focused on the oxidation and self-reaction of active groups in coal.Firstly,the active groups in coal were analyzed.According to the formed time,the active groups in coal were separated to initial ones and secondary ones.The groups in initial coal samples were tested by FTIR.The real-time changes of active groups were obtained using an in-situ FTIR.An in-situ testing system of infared spectrogram was designed based on traditional FTIR.In the in-situ testing system,a chamber was used to load coal sample;a gas providing system and an electronical heater was used to simulate different conditions.Using the in-situ testing system,the real-time changes of active groups under different conditions were tested.Under oxygen atmosphere,some active groups decreases at initial stage and then increases with the rise of temperature later.The break points of different active groups are also different.Under oxygen-free atmosphere,the change trends of active groups are similar to oxygen atmosphere.In contrast with oxygen atmosphere,the quantity of active groups under oxygen-free atmosphere is smaller and the temperatures at break points are lower.Under oxygen atmosphere after oxygen-free atmosphere,the decrease at initial stage almost disappears.The analysis on real-time change of active groups indicates some types of active groups can react at low temperatures under oxygen-free atmoshphere.At the initial stage of coal reactions under oxygen and oxygen-free atmospheres,initial active groups in coal are consumed but the same types of secondary active groups cannot form very much until a high enough temperature.So the quantity of active groups decreases at the initial stage.During the reaction under oxygen atmosphere of coal samples which had reacted under oxygen-free atmosphere,most of the initial active groups had been consumed during the previous reaction under oxygen-free atmosphere.So the self-reaction of active groups is weak.Consequently,the quantity of active groups would increase with the production of secondary active groups.The decrease phenomenon at the initial stage of coal reaction disappears.In order to further approve the self-reaction of active groups,the products were tested by a gas chromatography.Gaseous production of coal reaction under different conditions of oxygen atmosphere,oxygen-free atmosphere and oxygen atmosphere after oxygen-free atmosphere were tested.The reactions under the three different conditons can produce different types of gaseous products.It indicates self-reaction of active groups exists and can produce products.Based on comprehensive analysis,a reaction model including three reaction sequences was proposed for spontaneous combustion of coal.The model suggests the self-reaction of active groups exists in spontaneous combustion of coal besides direct burn-off and sorption sequences between coal and oxygen.And the chemical reactions which generate CO,CO2 and H2O were proposed.Spontaneous combustion of coal is the result of oxidation and self-reaction of active groups.However,self-reaction of active groups in coal can not exist individually.The heat released from oxidation of active groups provides initial enery for the self-reaction of active groups.Based on the theory of oxidation and self-reaction of active groups,some macroscopic characteristics were analyzed.At early stage of coal self-heating,only initial active groups and few secondary active groups take part in reaction.In contrast,plenty of secondary active groups take part in chain reactions at later stage.Consequently,self-heating of coal is a nolinear process.For high ranks of coal,initial active groups are few and secondary active groups are difficult to form.It results in the decrease of the quantity of active groups.As a result,their oxygen consumption rate decreases during 30~50 ℃.Moisture inhibits the transfer of active groups,which decreases the probability of active groups to contact and react.Consequently,the coals with high moisture content present a delay phenomenon in temperature rise.The unreacted sulphur components form a film that covers the coal surface and would slightly inhibit the reaction between active groups.The theory of oxidation and self-reaction of active groups can explain the macroscopic characteristics very well.
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