Laboratory measurements of methane desorption behavior on coal under different modes of real-time microwave loading

Abstract

This paper presents a technique for accelerating coalbed methane (CBM) desorption to increase extraction efficiency using microwaves. Methane desorption experiments with and without real-time microwave loading (ML) were carried out in the laboratory. To avoid high temperatures in the samples, ML was employed via two modes; continuous ML (CML) with low power and discontinuous ML (DML) with high power. The results show that total desorption volumes were increased from 1.87 to 3.26 times under CML and from 1.91 to 4.13 times under DML. The desorption rate using CML decreased smoothly like the rate without ML but the desorption rate was higher. The DML caused the desorption rate to increase rapidly and sharp peaks were evident on its desorption rate graph. For DML, the maximum desorption rate increased by a factor of 10.8. Kinetic analysis indicated that both CML and DML increased the diffusion coefficient and reduced diffusion attenuation. For the same microwave output energy, DML with short-term microwave bursts with high power has a better stimulating effect on methane desorption than CML. That ML significantly enhances methane desorption indicates that ML can greatly improve CBM productivity, and thus it has the potential to become a new CBM stimulation technology.