This study presents an innovative dual CO2 sequestration (DCS) method by integrating gaseous storage in mined-out areas with mineralized storage in backfill materials. The objects are to maximize the CO2 storage and FA disposal capacity in the premise of ensuring caprock stability and ecological water table preservation during on-site industrial practice. The indoor experiments were employed to analyze the workability of CO2 mineralized filling materials (CMFM) containing 50–90% fly ash (FA). The results demonstrate that: (1) As FA proportion rises, the CO2 uptake rate decreases from 1.49 to 1.21 mg-CO2/g-CMFM; the unconfined compressive strength (UCS) grows first and then decreases, peaking at FA80. (2) FA70 (70% FA content) exhibits optimal performance with yield stress of 16.76 Pa (< 200 Pa), mini-slump of 290 mm (> 71 mm), initial setting time of 146 min, CO2 uptake of 1.25 mg-CO2/g-CMFM, and peak UCS of 5.2 MPa. Additionally, with full consideration of the strain-softening of CMFM, strain-hardening of caved gangue, the criteria for roof caving and gangue-roof contacting, FLAC3D secondary development was employed to illustrate the influence of the width of CO2 gas storage block (CGSB) and CO2 mineralized storage block (CMSB) on the total mass of wastes disposal, caprock deformation, and water table lowering. The findings illustrate that a 40–20 m configuration achieves maximum FA utilization (e.g., 33.76 × 103 t for FA70) while maintaining critical environmental thresholds: horizontal deformation of caprock of 0.124 mm/m (< 0.15 mm/m) and water table lowering of 0.61 m (< 1.2 m). These findings establish an engineering paradigm that simultaneously addresses CO2 sequestration, industrial waste recycling, and ecological water table preservation. Article Highlights.<UnorderedList Mark="Bullet"> <ItemContent> The novel dual CO2 storage by integrating CO2 storage in goaf areas with carbonation backfill was proposed. </ItemContent> <ItemContent> The workability of the CMFM were analyzed. </ItemContent> <ItemContent> The influence of width of gas and solid block (WGSB) on caprock deformation, CO2 storage and FA disposal capacity, and water table lowering were illustrated based on FLAC3D secondary development. </ItemContent> </UnorderedList>

Continuous extraction and continuous backfill for gaseous and mineralized dual CO₂ sequestration and water-preserving coal mining

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2025年4月10日

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Yujun Xu,
Liqiang Ma,
Lei Wang,
Ichhuy Ngo,
Yangyang Wang

摘要

This study presents an innovative dual CO₂ sequestration (DCS) method by integrating gaseous storage in mined-out areas with mineralized storage in backfill materials. The objects are to maximize the CO₂ storage and FA disposal capacity in the premise of ensuring caprock stability and ecological water table preservation during on-site industrial practice. The indoor experiments were employed to analyze the workability of CO₂ mineralized filling materials (CMFM) containing 50–90% fly ash (FA). The results demonstrate that: (1) As FA proportion rises, the CO₂ uptake rate decreases from 1.49 to 1.21 mg-CO₂/g-CMFM; the unconfined compressive strength (UCS) grows first and then decreases, peaking at FA80. (2) FA70 (70% FA content) exhibits optimal performance with yield stress of 16.76 Pa (< 200 Pa), mini-slump of 290 mm (> 71 mm), initial setting time of 146 min, CO₂ uptake of 1.25 mg-CO₂/g-CMFM, and peak UCS of 5.2 MPa. Additionally, with full consideration of the strain-softening of CMFM, strain-hardening of caved gangue, the criteria for roof caving and gangue-roof contacting, FLAC^3D secondary development was employed to illustrate the influence of the width of CO₂ gas storage block (CGSB) and CO₂ mineralized storage block (CMSB) on the total mass of wastes disposal, caprock deformation, and water table lowering. The findings illustrate that a 40–20 m configuration achieves maximum FA utilization (e.g., 33.76 × 10³ t for FA70) while maintaining critical environmental thresholds: horizontal deformation of caprock of 0.124 mm/m (< 0.15 mm/m) and water table lowering of 0.61 m (< 1.2 m). These findings establish an engineering paradigm that simultaneously addresses CO₂ sequestration, industrial waste recycling, and ecological water table preservation. Article Highlights.

The novel dual CO₂ storage by integrating CO₂ storage in goaf areas with carbonation backfill was proposed.

The workability of the CMFM were analyzed.

The influence of width of gas and solid block (WGSB) on caprock deformation, CO₂ storage and FA disposal capacity, and water table lowering were illustrated based on FLAC^3D secondary development.

Continuous extraction and continuous backfill for gaseous and mineralized dual CO2 sequestration and water-preserving coal mining

摘要

Continuous extraction and continuous backfill for gaseous and mineralized dual CO₂ sequestration and water-preserving coal mining