Regression Orthogonal Analysis of Underground Coal Gasification Products

Abstract Underground coal gasification is the process of converting coal deep buried underground into a combustible gas in situ through appropriate chemical reactions and extracting it to the ground for use. Since the chemical reactions take place underground, controls and measurements are extremely difficult. In addition, it is very expensive to conduct underground coal gasification tests directly in underground coal seams, and field tests cannot accomplish the same conditions as underground. To establish the relationship between injection parameters and gasification products in underground coal gasification, the process simulation software, Aspen Plus, was used to simulate the underground coal gasification process. The state parameters of processing units and nodes under each injection parameter, as well as the state parameters and mole content of the gasification products were obtained through calculating the mass balance and energy balance by using thermodynamic equations, unit operation equations, and mathematical equations. The orthogonal experimental method was adopted to analyze the significant influence of gasification agent injecting parameters on products. It is expressed from the result that the oxygen flow rate has a significant impact on the gasification products, followed by the water flow rate, and the influence of temperature and pressure of the gasification agents, i.e. oxygen and water, on the products are minor. Finally, the quantitative relationship between the gasification products and the injection parameters of each agent was established through regression orthogonal method, and the regression equation was confirmed by the inverse calculation and correlation coefficient test. The research results can provide reference for the technique formulating and parameters controlling of underground coal gasification.