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

Abstract

This paper presents a series of surface experiments simulating underground coal gasification (UCG). The main goal of the experiments was to investigate the influence of the gasification medium and the coal rank on the gasification process. Four multi-day trials were carried out using a laboratory gasification facility designed for the large-scale experimental simulations of UCG and located in the Experimental Mine “Barbara”, located at Mikołów, Poland. Two Polish bituminous coals were investigated: coal sourced from “Piast-Ziemowit” mine and coal sourced from “Wesoła” mine. Each of the two coals was gasified in two separate experiments using oxygen-enriched air (OEA) and pure oxygen as the respective gasifying agents. Gasification with oxygen resulted in significantly higher gas quality and higher process efficiency than gasification with OEA. Higher concentrations of hydrogen (23.2% and 25.5%) and carbon monoxide (31.8% and 33.4%) were obtained when oxygen was used as a gasifying reagent, while lower concentrations were obtained in the case of gasification with OEA (7.1% and 9.5% of hydrogen; 6.4% and 19.7% of carbon monoxide). Average gas calorific values were 7.96 MJ/Nm3 and 9.14 MJ/Nm3 for the oxygen experiments, compared to 2.25 MJ/Nm3 and 3.44 MJ/Nm3 for the OEA experiments (“Piast-Ziemowit” coal and “Wesoła” coal, respectively). The higher coalification degree of “Wesoła” coal (82.01% of carbon) compared to the “Piast-Ziemowit” coal (68.62% of carbon) definitely improves the gas quality and energy efficiency of the process. The rate of water condensate production was higher for the oxygen gasification process (5.01 kg/h and 3.63 kg/h) compared to the OEA gasification process (4.18 kg/h and 2.63 kg/h, respectively), regardless of the type of gasified coal. Additionally, the textural characteristics (porosity development) of the chars remaining after coal gasification experiments were analyzed. A noticeable development of pores larger than 0.7 nm was only observed for the less coalified “Piast-Ziemowit” coal when analyzed under the more reactive atmosphere of oxygen.

Constructed wetland as a green remediation technology for the treatment of wastewater from underground coal gasification process

“…Coal from the "Wesoła" mine contains about two times less moisture and a lower content of ash, is more coalified and has a greater calorific value. Due to their properties, both coals can be classified as medium-rank bituminous coals [ 21 , 22 ]. The raw coals were subjected to gasification using oxygen-enriched air (OEA) as a gasifying agent (Experiment 1 and Experiment 3).…”

“…Characteristics of the UCG experiments are presented in Table 2 . Detailed information on the UCG simulations was described by Wiatowski et al [ 21 ].…”

Simulation of Underground Coal-Gasification Process Using Aspen Plus

“…Due to its underground nature, it is challenging to measure and control these processes. Consequently, there are limited research findings in this area; in particular, there is a lack of mature models to describe gasification reactions [7,8].…”

“…Chen et al [9] conducted an oxygen-enriched carbon dioxide gasification experiment, and the results of the study concluded that an increase in the oxygen content led to an increase in both gas products and calorific value and that the best gas production was achieved when the oxygen concentration was 50-60%. Wiatowski et al [7] investigated the effect of oxygen content on the gasification process and showed that higher gas quality and process efficiency can be obtained, and the calorific value of the resulting gas is higher when oxygen-enriched air is used as a gasifier compared to pure oxygen. Zong et al [10] used Aspen Plus to establish a kinetic simulation model for the underground gasification process of coal and investigated the effects of oxygen/coal mass ratio and steam/coal mass ratio on the gas components, and the results concluded that: with the increase in the oxygen/coal mass ratio, the carbon conversion rate gradually rises, and the content of CO and H 2 increases; however, with the increase in the steam/coal mass ratio, the carbon conversion rate gradually decreases, and the content of CO and H 2 gradually decreases.…”