Removing CO₂ and H₂S from the Gas Produced during Underground Coal Gasification (UCG)

Abstract

The new method of simultaneous disposal of CO₂ and H₂S in coal gas generated during underground coal gasification (UCG) using industrial waste alkali liquor is put forward and studied for the first time. The rationale of absorption of CO₂ and H₂S by the alkali liquor is analyzed, and the mass transfer model for the above process is established. The impact of the existence of H₂S on absorbing CO₂ by the alkali liquor is studied on the basis of the model experiment. Research shows that as the velocity of coal gas increases, the selection coefficient of H₂S improves, the temperature rises, the selection coefficient of H₂S deceases, but the removal rate of CO₂ increases. By means of study, it can be found that the removal rate of CO₂ can reach more than 60% under the conditions of the suitable concentration of the alkali liquor and the ratio of liquid to gas, the heat value of underground coal gas can heighten by 12.3%, 17.7%, and over 20%, respectively, when the removal rate of CO₂ is 58%, 80%, and greater than 90%.

Keywords:

• absorption
• CO₂
• H₂S
• mass transfer model
• UCG
• waste alkali liquor

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Ratification No.: 59906014, 50276066, 20207014, 50674084). The technical contributions of Professor Wang Jialian and Doctor Liang Jie are gratefully acknowledged by the authors.