铁粉辅助微波热激联合降压分解甲烷水合物试验

Experiment on methane hydrate decomposition with iron powder assisted microwave stimulation combined with depressurization

为了提高甲烷水合物的分解率及能量利用率,提出采用铁粉辅助微波热激联合降压分解甲烷水合物的方法。设置了4个实验组(微波热激实验组1、铁粉辅助微波热激实验组2、微波热激联合降压实验组3以及铁粉辅助微波热激联合降压实验组4),对预先在石英砂中合成的甲烷水合物开展了分解试验,研究了不同试验条件下甲烷水合物的分解特性。研究结果表明:在微波热激作用下,甲烷水合物快速吸收微波能量而迅速分解,前期水合物由微波穿透体积加热的方式分解,中后期由于宏观热传导而分解,且分解前期的平均产气速率和能量效率比均远比分解中期和后期的高,微波的直接体积加热效果比传统加热方法的加热效果好;在微波加热功率相同的条件下,实验组2、实验组3、实验组4都能进一步促进甲烷水合物的分解,且实验组2的分解效果更高,为本研究的最优的分解条件;降压组分解前期的平均产气速率和能量效率比都高于非降压组,中后期的平均产气速率和能量效率均比非降压组的低。在实际应用时,可在水合物分解后期关闭微波,避免过多微波能量的浪费,进一步提高能量效率比。

Iron powder assisted microwave stimulation combined with depressurization method was proposed to improve the decomposition rate and energy utilization rate of methane hydrate. Four experimental cases(microwave stimulation Case 1, iron powder assisted microwave stimulation Case 2, microwave stimulation combined with depressurization Case 3 and iron powder assisted microwave stimulation combined with depressurization Case 4) were set up to decompose pre-synthesized methane hydrate in quartz sand. The methane hydrate decomposition characteristics under different experimental conditions were studied. The results show that methane hydrate decomposes rapidly during microwave stimulation. The hydrate decomposes because of microwave penetrating volume heating in the initial stage and it decomposes because of heat conduction in the middle and last stage. The average gas production rate and the energy efficiency ratio of the initial stage are both higher than those of middle and last stage, which indicates that direct volume of microwave stimulation is better than traditional heating method for hydrate decomposition. All of Case 2, Case 3 and Case 4 can promote decomposition rate further with the same microwave power, and Case 2 has more significant promotion effect,which is the optimal decomposition condition in this study. The average gas production rate and energy efficiency ratio of the depressurization case are higher than those of the non-depressurized case in the early stage, and lower than those of the non-depressurized case in the middle and late stage. Microwave stimulation in the initial stage of depressurization will be more helpful for decomposing and producing gas. In turn, the microwave can be turned off at the later decomposition stage to avoid excessive waste of microwave energy in practical application.