Experimental study of advantages of coalbed gas bioengineering

Abstract

Coalbed gas bioengineering (CGB) is a special fermentation engineering that converts some organic components of coal to methane, which enhances coalbed gas production. To verify the feasibility and superiority of CGB, three different rank coals were used to simulate the anaerobic fermentation for biomethane production in laboratory. The SEM, XPS, MIP and Isothermal adsorption experiments were used to characterize coal surface modification and pore structure changes of coal before and after bioconversion. Firstly, the different rank coals have potential for biomethane production, and the biomethane production of HN coal as low rank coal is 1.43 times and 2.45 times higher than that of HB and ZG coals. The injection of CO2 in the later stage of HN anaerobic fermentation can realize the CO2 biomethanation with a methane yield of 1.85 mL/g. Secondly, the decrescent of Langmuir volume of residual coal after bioconversion determine the enhancement of coal seam desorption capacity for methane. Thirdly, the increase rate in the proportion of macropores in HN, HB, and ZG coals is 5.86%, 4.23%, and 11.76%, the increase in coal permeability is consistent with the increase in the distribution ratio of macropores in the coal, as well as the increase in total pore volume. The multiple advantages of “four enhancements and one reduction” (production enhancement, liquids enhancement, desorption enhancement, permeability enhancement, and emission reduction) are summarized. A framework system of CGB covering three phases is briefly described: acquisition of efficient microorganisms, laboratory simulations and field tests. CBGB is expected to positively impact the stagnant commercial development of coalbed methane.