煤炭地下气化注气方式与能量回收效率

Gas injection methods and energy recovery efficiency in underground coal gasification

研究不同注气方式煤炭地下气化(UCG)能量回收情况,有利于发展更高效的UCG工艺。设计并实施了固定和移动注气点UCG模型实验,基于化学计量学和碳平衡法计算了气化煤耗总量及速率,对比分析了2种注气工艺对煤气组成和热值的影响。在此基础上,分析了不同注气方式下煤气产量和有效气体组成的变化,评价了2种注气工艺实验的能量回收效率。结果表明,固定注气点实验中提高O_(2)净注入流量可改善煤气热值衰减的现象,但随着气化空腔的扩大,提高O_(2)净注入流量对气化反应的促进作用逐渐降低;分3次提高O_(2)净注入流量,煤气热值分别提高2.01、1.27和1.10 MJ/Nm^(3),气化效率(煤气的热值与碳的燃烧热之比)分别提高14.64%、9.45%和7.73%。移动注气点位置,可实现煤气热值和气化效率的短时间快速回升,分4次移动注气点位置,每次移动距离为300 mm,煤气热值分别提高2.95、3.32、3.37和2.54 MJ/Nm^(3),气化效率分别提高17.99%、21.04%、27.88%和13.92%。2种注气工艺实验分别气化了72.49 kg和91.47kg的煤,平均煤耗速率分别为0.97和1.27 kg/h,气化效率和煤耗速率呈同步突变,这一现象在改变气化剂注入条件和移动注气点位置后更为明显,表明气化效率与煤耗速率具有一定关系。相比固定注气点实验,移动注气点位置可有效改善气化效果,相同的气化剂注入条件下,有效气体组分和气化效率分别提高12.5%和23.23%。

The study of energy recovery from underground coal gasification(UCG)with different gas injection methods is conducive to the development of a more efficient UCG process.Various UCG modeling experiments were designed and implemented for fixed and mobile gas injection points,the total gasification coal consumption and rate were calculated based on stoichiometry and carbon balance method,and the effects of the two gas injection processes on the composition and calorific value of the gas were compared and analyzed.On this basis,the changes in gas production per unit of coal and effective gas composition under different gas injection methods were analyzed,and the energy recovery rates of the two gas injection process experiments were evaluated.The results show that increasing the net O_(2) injection flow rate can improve the gas calorific value decay in the fixed injection point experiment,but the promotion effect of increasing the net O_(2) injection flow rate on the gasification reaction decreased with the expansion of the gasification cavity.By increasing the net O_(2) injection flow rate three times,the calorific value of gas was increased by 2.01,1.27 and 1.10 MJ/m^(3),respectively,and the gasification efficiency(the ratio of the calorific value of the gas to the heat of combustion of carbon)was increased by 14.64%,9.45%and 7.73%,respectively.Moving the position of the gas injection point can achieve a short-time rapid recovery of the calorific value of the gas and the gasification efficiency.Moving the position of the gas injection point four times,each time the moving distance was 300 mm,the calorific value of the gas was increased by 2.95,3.32,3.37 and 2.54 MJ/m^(3),respectively,and the gasification efficiency was increased by 17.99%,21.04%,27.88%,and 13.92%.The two gas injection process experiments respectively gasified 72.49 kg and 91.47 kg of coal,and the average coal consumption rate was 0.97 and 1.27 kg/h.The gasification efficiency and coal consumption rate showed a synchronous mutation,and this phenomenon was more obvious after changing the injection conditions of the gasifier and moving the position of the gas injection point,which indicated that there was a certain relationship between the gasification efficiency and the coal consumption rate.Compared with the fixed gas injection point experiment,moving the location of the gas injection point can effectively improve the gasification effect,and the effective gas composition and gasification efficiency was increased by 12.5%and 23.23%,respectively,under the same gasifier injection conditions.