煤炭地下气化过程产气特征数值模拟研究

Numerical simulation on gas production characteristics during underground coal gasification

为了提高煤炭地下气化产气效率,采用数值模拟方法,建立了煤炭地下气化通道数值模型,研究了气化通道内产气组分的时空分布和可燃气体的热值特征。结果表明:气化产气过程可分为初始产气、中期产气和稳定产气三阶段,CO_(2)浓度在气化初期快速达到峰值,CO和H_(2)浓度则在气化中期快速增加,气化20d后通道内气体组分浓度分布和热值均趋于稳定;气化剂中氧含量对通道内CO_(2)和CO的浓度分布影响明显,对H_(2)影响相对较小;C的氧化反应、CO_(2)和水蒸气的还原反应同时存在于氧化区和还原区,随着气化剂中氧含量的提高,还原区范围逐渐扩大,CO和H_(2)的浓度逐渐升高;氧含量每增加20%,通道出口可燃气体热值增加约10%。模拟结果与工业性试验结果具有较好的一致性。

To improve the gas production efficiency of underground coal gasification(UCG),a numerical channel-type UCG model was established to study the spatial distribution of gas components and calorific value characteristics of combustible gas in the UCG channel. Results have shown that the gas production process can be divided into three stages,initial stage,middle stage and stable gas production stage. The CO_(2)concentration reached the peak rapidly in the early period of gasification,while the CO and H_(2) concentration increased sharply in the middle stage. After 20d of gasification,the gas concentration distribution and calorific value in the channel became stable. The oxygen content in gasification agent had an obvious influence on the concentration of CO_(2)and CO in UCG channel,but had little impact on that of H_(2). The oxidation reaction of C and the reduction reaction of CO_(2)and water vapor simultaneously existed in the oxidation reaction zone and reduction reaction zone. As the oxygen concentration rose,the reduction area in gasification channel expanded,and the concentration of CO and H_(2) increased gradually at the same time. The calorific value of combustible gases at the outlet of gasification channel increased by 10% with the rise of oxygen content by 20%. The numerical simulation results were in good consistency with the industrial test results.