关键词: 煤层气, 微波注热, 热量迁移, 热经济性, 数值模拟

Abstract: Microwave heating for coalbed methane(CBM)production features fast heat injection and high thermal efficiency;however,energy dissipation and loss are inevitable in field operations.To further improve energy-utilization efficiency in microwave-heating production,a systematic study was conducted on energy-transfer laws and thermo-economic performance during the production process.Based on triaxial adsorption-desorption experiments for CBM under microwave heating,the dynamic relationship between temperature and desorbed gas volume with heating time was obtained,and a mathematical model of energy transfer was established.Numerical simulation was used to reveal heat-transfer laws during microwave-heating production,and a thermo-economic evaluation model was constructed with thermal efficiency and energy extraction efficiency as the core indices;the impacts of different microwave power levels and port layouts on thermo-economic performance were analyzed.Results show that under different microwave power levels,the coal seam accounts for the largest proportion of absorbed heat,whereas the adsorbed gas accounts for the smallest proportion.The heat absorbed by water changes relatively steadily;the heat absorbed by desorbed gas increases with time;and boundary dissipated heat increases significantly under high microwave power.With two microwave ports and 500 d of heating,thermal efficiency reaches a peak of 14.7% at 1 330 W;energy extraction efficiency can reach 660% at 1 330 W.Under constant power,the use of a four-port layout increases thermal efficiency by 2.51 percentage points and increases energy extraction efficiency by 71.00 percentage points.This study provides a theoretical basis for accelerating commercialization of CBM production and for optimizing construction schemes and process parameters for microwave-heating production.