Synthesis Gas Composition Prediction for Underground Coal Gasification Using a Thermochemical Equilibrium Modeling Approach

Abstract

Underground coal gasification (UCG) is an in situ conversion technique that enables the production of high-calorific synthesis gas from resources that are economically not minable by conventional methods. A broad range of end-use options is available for the synthesis gas, including fuels and chemical feedstock production. Furthermore, UCG also offers a high potential for integration with Carbon Capture and Storage (CCS) to mitigate greenhouse gas emissions. In the present study, a stoichiometric equilibrium model, based on minimization of the Gibbs function has been used to estimate the equilibrium composition of the synthesis gas. Thereto, we further developed and applied a proven thermodynamic equilibrium model to simulate the relevant thermochemical coal conversion processes (pyrolysis and gasification). Our modeling approach has been validated against thermodynamic models, laboratory gasification experiments and UCG field trial data reported in the literature. The synthesis gas compositions have been found to be in good agreement under a wide range of different operating conditions. Consequently, the presented modeling approach enables an efficient quantification of synthesis gas quality resulting from UCG, considering varying coal and oxidizer compositions at deposit-specific pressures and temperatures.

Establishment and application of a two‐stage reaction equilibrium model for underground coal gasification

“…The kinetic modeling results of Perkins and Sahajwalla showed good results (relative inaccuracy range: the main gas component was 0.00% to 19.19%; LCV was 6.52%) in comparison with the Centralia LBK-1 field test data. 35 The thermodynamic UCG model of Klebingat et al showed that the relative inaccuracy range for the main gas single compounds ranged between 4.32% and 9.95%; the relative inaccuracy for the synthesis gas LCV was found to be relatively low (6.60%) in comparison with the Hanna I field trial study. But the relative inaccuracy range for the main gas single compounds was between 5.88% and 18.6% and the relative inaccuracy for the synthesis gas LCV was 21.7% compared to the Centralia PSC field trial study.…”

“…The results of the main gas components and LCVs were consistent with the measured data, and the maximum deviation was less than 10% (relative inaccuracy: the main compound was 0.2% to 9.4%; LCV was 0.4% to 2.2%). The kinetic modeling results of Perkins and Sahajwalla showed good results (relative inaccuracy range: the main gas component was 0.00% to 19.19%; LCV was 6.52%) in comparison with the Centralia LBK‐1 field test data 35 . The thermodynamic UCG model of Klebingat et al showed that the relative inaccuracy range for the main gas single compounds ranged between 4.32% and 9.95%; the relative inaccuracy for the synthesis gas LCV was found to be relatively low (6.60%) in comparison with the Hanna I field trial study.…”

Large-Scale Experimental Simulations of In Situ Coal Gasification in Terms of Process Efficiency and Physicochemical Properties of Process By-Products

“…The unique research results are invaluable for modeling various aspects of the UCG process and designing the process in real conditions. A number of examples of the application of the results of experimental research for the implementation of model works, including designing automated control systems, are described in the literature [44][45][46].…”

Regression Models Utilization to the Underground Temperature Determination at Coal Energy Conversion

“…The results showed the positive impact of the steam addition into the gasification agent to increase the hydrogen and carbon monoxide content in syngas and increase the calorific value. A stoichiometric equilibrium model has been used to estimate the equilibrium composition of the produced gas [6]. This model is based on the Gibbs function's minimization and was used to simulate the relevant thermochemical coal conversion processes.…”