Book Description

The Laramie Energy Research Center (LERC) conducted an underground coal gasification experiment in a 9-m thick subbituminous coal seam near Hanna, Wyoming. Sandia Laboratories designed and fielded an extensive instrumentation array which included approximately eight thermocouples within the seam in each of 15 diagnostic wells. The instrumentation provided thermal data related to the process during both reverse combustion linkage and forward gasification. Portions of these data suitable for analysis by inverse heat conduction techniques included (1) the responses from the approximately cylindrical reverse combustion linkage path and (2) the responses at thermocouples outside the gasified zone due to conduction from the final boundary. Because of the effects of property variations and water vaporization on the conduction response, an exact analytical solution could not be used. Instead, the approach was to adjust parameters of the constant property analytical solutions to fit numerical calculations that included property variations and water vaporization. Sensitivity studies performed to estimate the accuracy of solutions obtained indicated that parameters relating to size and distance should be identifiable within +- 0.25 m; however, accurate estimates of temperature could not be obtained. Results allowed the position of the reverse combustion linkage path to be mapped, and estimates of its size (approximately 1 m in diameter) and average temperature (750 K--1000 K) to be obtained. With respect to forward gasification, the analysis yielded estimates of the final boundaries established by the burn and characterizations of how the front approached its final position.