Further development of an axisymmetric global UCG (underground coal gasification) cavity growth simulator
Development has continued on the global underground coal gasification (UCG) cavity simulation model CAVSMII, first described at the 12th UCG symposium, with the result that it now treats essentially all major processes that occur during a UCG operation. To a large extent these modifications were motivated by insight into UCG cavity growth gained from observation of the excavated Partial Seam CRIP (PSC) UCG site. A submodel for water influx has been formulated and added, based on gravity drainage and water reflux, including compressibility effects of the medium. A submodel empirically describing the growth of an outflow channel from a horizontal uncased production borehole in the coal seam has been developed as well. The settling of solids in the rubble pile caused by removal of carbon from spalled char has been reformulated more realistically. Another major modeling reformulation is the addition of a resistance to gas flow through the overburden rubble, which was previously assumed negligible in comparison to the ash pile flow resistance. Also, the submodel describing dynamics of the reaction zone between the ash rubble and the competent coal wall, which previously consisted of an empirical two-parameter model, is now fully integrated into the global cavity evolution model and solved for each time step. At the same time, more efficient algorithms for computing flow of injection gas through the rubble pile have reduced both total CPU time and code memory requirements by more than a factor of two. The present state of the simulator is presented and the effect of some key physical and process parameters is explored. Finally, results are presented for the simulation of UCG cavity growth for the PSC test, the upcoming Rocky Mountain I test and a test of a high-ash, relatively thin seam coal proposed for Brazil. 13 refs.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6141524
- Report Number(s):
- UCRL-96461; CONF-8708106-2; ON: DE87013115
- Country of Publication:
- United States
- Language:
- English
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