№83-4

Justification of goaf parameters in an underground gasifier

P. Saik¹ https://orcid.org/0000-0001-7758-1083

¹Dnipro University of Technology, Dnipro, Ukraine

Coll.res.pap.nat.min.univ. 2025, 83:45–54

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ABSTRACT

Purpose. To establish relationships governing the formation and spatio-temporal evolution of the gasification goaf area in an underground gasifier as a function of gasification duration and coal seam thickness.

The research methodology was based on laboratory-scale physical modeling of underground coal gasification, reproducing the advance of the combustion face and the deformation behavior of the gasifier roof strata. During the experiments, the propagation rate of the combustion face, roof subsidence parameters measured using reference sensors, and the composition and concentration of producer gas were determined. The geometric parameters of the gasified cavity were obtained by visualizing cavity outlines at different time instants and calculating areas using the trapezoidal rule.

Findings. Time-dependent relationships for the gasified cavity area were established as a function of gasification duration and coal seam thickness. A procedure for calculating the gasified cavity area of an underground gasifier is proposed. It is shown that the cavity growth dynamics are nonlinear and predominantly exponential, governed by the rate of advance of the combustion face across the chemical reaction zones. A relationship was identified between cavity expansion and the injection pressure of the blast mixture with respect to the stability of the gasification process.

Results. Time-dependent relationships for the gasified cavity area were established as a function of gasification duration and coal seam thickness. A procedure for calculating the gasified cavity area of an underground gasifier is proposed. It is shown that the cavity growth dynamics are nonlinear and predominantly exponential, governed by the rate of advance of the combustion face across the chemical reaction zones. A relationship was identified between cavity expansion and the injection pressure of the blast mixture with respect to the stability of the gasification process.

Scientific novelty lies in establishing the dependencies of changes in the gasified cavity area of an underground gasifier on gasification duration and coal seam thickness, while accounting for the spatial distribution of chemical reaction zones that evolve along the reaction channel.

Practical significance lies in the applicability of the obtained relationships for predicting gasified cavity parameters and controlling the underground coal gasification process. The established dependencies can be used to justify blast-mixture injection regimes, improve the operational stability of the underground gasifier, and reduce the risk of uncontrolled roof collapse. The results are recommended for use in developing process flow schemes and mathematical models of underground coal gasification under real mining and geological conditions.

Keywords: underground coal gasification, underground gasifier, gasification goaf, coal seam.

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date of first submission of the article to the publication – 10/01/2025
date of acceptance of the article for publication after review – 11/03/2025
date of publication – 12/29/2025