Goaf Backfilling With Supercritical CO2 for Roof Support and Storage
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Solution Overview
Problem
Existing carbon storage methods in abandoned mines fail to address gas leakage from overburden cracks and do not synchronize backfilling reinforcement with carbon dioxide storage, which is crucial for green mining and carbon neutrality.
Innovation Solution
A combined process integrating stopping-backfilling and carbon storage, where supercritical carbon dioxide is injected into backfilling slurry to solidify it, providing early support and achieving synchronization with backfilling reinforcement, using a backfilling slurry composed of water, cement, caustic sludge, sand, and an activator, with a cyclic process to enhance strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carbon dioxide is stored in the goaf after stopping, then the abandoned space is utilized for carbon storage, but the goaf cannot provide sufficient support for the roof strata
Solution Approach 1:
The patent combines carbon dioxide storage with backfilling support into a single integrated process. The goaf is simultaneously used as both a storage space for carbon dioxide and a support structure for the roof strata, eliminating the need to choose between these two functions. This is achieved by injecting backfilling slurry containing carbon dioxide into the goaf, where the slurry provides mechanical support while storing carbon.
Solution Approach 2:
The goaf is given multiple functions: it serves as a carbon storage reservoir, a support structure for the roof, and a disposal space for mining waste. The backfilling material performs dual functions of providing structural support and storing carbon dioxide, maximizing the utility of the abandoned mining space.
2Strength
If backfilling is performed to support the goaf, then the roof strata are stabilized, but the carbon storage capacity is reduced due to space occupation
Solution Approach 1:
The patent changes the physical and chemical parameters of the backfilling material by incorporating carbon dioxide into the slurry. This transforms the backfilling material from a simple structural support medium to a dual-function material that provides both mechanical support and carbon storage. The carbon dioxide is injected into the slurry in supercritical or gaseous state and becomes trapped within the solidifying matrix.
Solution Approach 2:
The backfilling slurry is formulated as a composite material containing cement, water, and injected carbon dioxide. This composite structure allows the material to simultaneously provide structural integrity through cement hydration and store carbon dioxide within its matrix, achieving both support and storage functions in a single material system.
3Strength
If early support strength is required for the backfilling body, then the stopping process must wait for full strength development, but this reduces mining productivity
Solution Approach 1:
The patent applies preliminary action by injecting carbon dioxide into the backfilling slurry before the slurry fully solidifies. The injected carbon dioxide accelerates the strength development of the backfilling body, providing early support strength that allows the mining operation to continue without waiting for complete curing of the backfill material.
Solution Approach 2:
The patent utilizes phase transitions of carbon dioxide (injected in supercritical or gaseous state) to accelerate the hardening process of the backfilling slurry. The phase change of carbon dioxide during injection and subsequent trapping within the slurry matrix promotes faster strength development, enabling early support and continuous mining operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method maximizes the use of abandoned space for carbon dioxide storage while effectively supporting the roof strata, ensuring the stability of the mining area and achieving carbon neutrality.
Implementation Method 1
injecting supercritical carbon dioxide into the backfilling slurry
Implementation Method 2
the state of the carbon dioxide is converted into a solid or liquid state
Data Source
AI summary
Disclosed is a combined process of integrating stopping-backfilling and carbon storage. The combined process includes the following steps of: determining a cyclic interval of a working face through measured data of a mine pressure of a fully-mechanized coal winning working face; when the stopping distance of the fully-mechanized coal winning working face reaches a backfilling isolation interval, providing a backfilling tarpaulin behind a hydraulic support, and pumping, through a backfilling pipeline, backfilling slurry to a backfilling area along a support beam; when the area is backfilled with the backfilling slurry, injecting supercritical carbon dioxide into the backfilling slurry; and allowing the supercritical carbon dioxide to fully react with the backfilling slurry to solidify the backfilling slurry.