THERMODYNAMIC ANALYSIS OF ENERGY OPTIMUM FORMATION IN COAL GASIFICATION
DOI:
https://doi.org/10.34185/1991-7848.2026.01.20Keywords:
gasification, coal, thermodynamic analysis, oxidizer consumption coefficient, producer gas, energy optimum, integral energy indicatorAbstract
Equilibrium thermodynamic modeling was applied to analyze the energy efficiency of coal gasification as a function of the oxidizer consumption coefficient. The oxidizer consumption coefficient is considered as a continuous control parameter that determines the balance between reduction and oxidation processes, and the analysis is based on the coordinated evaluation of equilibrium temperature, producer gas composition, its heating value, and specific gas yield. It is shown that variation of the oxidizer consumption coefficient leads not to isolated changes of individual parameters, but to their interrelated transformation with a clearly pronounced structural character. It is established that within the studied range, a three-stage structure of the process is formed, including a region of incomplete conversion with the presence of unreacted carbon, a region of rational operating conditions, and a region of excessive oxidation accompanied by a decrease in the content of combustible gas components. It is shown that transitions between these regions are characterized by changes in the behavior of the main parameter dependencies, reflecting a shift in the balance between dominant thermochemical processes.
It is established that within the region of rational operating conditions, an energy-optimal gasification regime is formed, corresponding to the maximum of the total combustible fraction of the producer gas and the minimum of oxidation products. It is shown that this regime is realized at an oxidizer consumption coefficient of approximately 0.3 and corresponds to the region of minimal oxidation losses. The introduction of the logarithmic indicator lg((CO+H₂)/CO₂) made it possible to obtain a stable criterion for evaluating the gasification regime, ensuring unambiguous identification of the optimum region. It is shown that the maximum of this indicator coincides with the maximum of the total combustible fraction and the minimum of oxidation products, confirming the realization of an optimal reduction–oxidation balance.
It is established that the gasification temperature increases monotonically with increasing oxidizer consumption coefficient and does not determine the position of the energy optimum. It is shown that beyond a certain value of the oxidizer consumption coefficient, further increases in temperature and gas yield no longer compensate for the decrease in gas heating value, resulting in reduced energy efficiency. To generalize the obtained results, an integral energy indicator was proposed, which simultaneously accounts for the producer gas yield and its heating value. It is established that this indicator exhibits a well-defined maximum at an oxidizer consumption coefficient of approximately 0.3 for all investigated conditions, despite the opposite trends of its components.
The obtained results show that the energy optimum of the gasification process is formed as a result of coordinated variation of process parameters and is determined by its internal thermodynamic structure. This makes it possible to move from the analysis of individual characteristics to a system-based identification of the rational gasification regime corresponding to minimal oxidation losses and maximum total energy output of the producer gas.
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