Abstract
Underground coal gasification (UCG) is an industrial process that converts coal into product gas (syngas). This technology makes it possible to obtain energy without mining coal and post-processing. The UCG process is considered a safe technology with various advantages over conventional mining techniques. However, a small amount of potentially dangerous syngas may escape from the UCG cavity, and it is necessary to pay attention to the safety of the process in this respect. This article analyses the impact of a syngas leak from UCG on a possible CO poisoning and explosion hazard in the vulnerable zones. Measured data from experiments and proposed mathematical models were used for the analysis of the UCG process and simulation studies. It is mainly a mathematical model mixing of gases, which evaluated the danger of explosion and CO poisoning in sensitive zones. This model predicts the composition of the syngas mixture with air because this mixture can be dangerous at a certain concentration. Simulation studies focused mainly on CO poisoning in vulnerable areas based on the measured data from laboratory experiments. Simulation studies have shown that the critical value of CO poisoning can achieve with a certain composition of syngas and its escape into vulnerable areas. The results of the studies here indicate a possible hazard. However, by monitoring and control of UCG process, this risk can be minimized. Based on the obtained results, the control of the supply of fresh air to the endangered area during the monitoring of the syngas composition was proposed to prevent the occurrence of possible poisoning.
Highlights
Coal is converted into syngas during the underground coal gasification process in the coal seam
We focused on predicting undesirable effects of the Underground coal gasification (UCG) process, such as explosion and carbon monoxide (CO) poisoning in areas with possible access to syngas leaking from this process
Simulation studies for an explosion and CO poisoning were investigated for vulnerability areas, i.e., mining shafts or populated areas near the UCG process
Summary
Coal is converted into syngas during the underground coal gasification process in the coal seam (i.e., in situ). The gas is produced and extracted by a well drilled into the gasified coal seam. Production wells are used to transport the product gas to the earth’s surface (see recovered gases in Figure 1) [1,2]. High-pressure gasification is carried out at a temperature of 700–900 ◦ C, but under certain conditions, a temperature of up to 1500 ◦ C can be achieved [2,3]. Coal is decomposed and mainly produces carbon dioxide (CO2 ), hydrogen (H2 ), carbon monoxide (CO), small amounts of methane (CH4 ), and hydrogen sulfide (H2 S) in the UCG process [3,4]. The UCG technology is not new; its history dates back more than 100 years, demonstrated in publications [5,6,7]
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