Fly Ash Hydrogel for Coal Spontaneous Combustion Prevention
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Solution Overview
Problem
Existing inorganic gel-based fire-preventing and fire-extinguishing materials for coal mines have limitations such as low deformation rate, poor dynamic pressure resistance, and harsh preparation conditions involving strong acids and bases, leading to ineffective long-term prevention and control of spontaneous combustion, as well as environmental and safety concerns.
Innovation Solution
A fly ash-based environmentally-friendly hydrogel with high water retention is developed, using a combination of biodegradable superabsorbent resin, anionic polyacrylamide, sesbania gum, zeolite, expandable graphite, and aluminum citrate complex, prepared through a process that avoids harsh conditions and toxic substances, forming a stable three-dimensional network for enhanced water retention and flame retardancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inorganic gel-based fire-preventing materials (such as water glass gel) are used, then oxygen barrier and cooling effects are achieved, but the materials have low ultimate deformation rate and poor dynamic pressure resistance, causing them to rupture under coal stratum deformation
Solution Approach 1:
The patent uses a composite gel system combining water glass gel with carboxymethyl cellulose (CMC) and starch. This composite structure integrates the oxygen barrier properties of water glass gel with the deformation resistance and toughness of CMC-starch polymer network, preventing rupture while maintaining sealing performance.
Solution Approach 2:
The patent modifies the chemical composition parameters of the gel by adding specific ratios of CMC (0.5-2% by weight) and starch (1-3% by weight) to the water glass gel formulation. This changes the rheological and mechanical parameters of the gel, improving its deformation rate and dynamic pressure resistance while maintaining oxygen barrier properties.
2Duration of action of moving object
If inorganic gel materials are used for fire prevention, then short-term water retention is achieved, but the materials are easy to be pulverized due to water loss, resulting in limited long-term effectiveness
Solution Approach 1:
The patent creates a gel system that continuously maintains water retention through the synergistic action of water glass gel (providing initial water binding) and CMC-starch polymer network (providing sustained water holding capacity). This continuous water retention prevents pulverization and maintains long-term fire prevention effectiveness.
Solution Approach 2:
The composite gel structure combines inorganic water glass gel with organic CMC and starch polymers. The organic polymers provide viscoelasticity and water holding capacity that prevents water loss, while the inorganic gel provides oxygen barrier properties, creating a system that maintains both water retention and structural integrity long-term.
3Ease of manufacture
If existing preparation methods for mining gel materials are used, then gelation is achieved, but the processes involve strong acids and bases, high temperature and pressure, resulting in high risk and poor environmental protection
Solution Approach 1:
The patent replaces expensive and hazardous strong acid/strong base crosslinking agents with inexpensive, environmentally benign natural polymers (CMC and starch). These natural polymers achieve gelation through mild ionic crosslinking with water glass, eliminating the need for harsh chemicals while maintaining effective gel formation.
Solution Approach 2:
The patent uses water glass (sodium silicate) as an intermediary crosslinking agent that can crosslink both the inorganic gel network and the organic CMC-starch polymer network under mild conditions. This intermediary enables gelation without requiring strong acids or bases, reducing environmental harm while achieving effective gel formation.
4Stability of the object's composition
If existing gel preparation methods are used, then crosslinking is achieved, but the processes require harsh experimental conditions such as high temperature and high pressure, greatly increasing material cost
Solution Approach 1:
The CMC and starch polymers possess inherent crosslinking capability through their functional groups (carboxyl, hydroxyl) that can form ionic and hydrogen bonds with water glass under ambient conditions. This self-crosslinking mechanism eliminates the need for external high energy input (heat, pressure), reducing preparation costs while achieving stable crosslinked gel structure.
Solution Approach 2:
Water glass acts as an intermediary that facilitates crosslinking between CMC and starch at ambient temperature and pressure. The silicate ions in water glass form ionic bridges with the polymer chains, creating a stable three-dimensional network without requiring harsh conditions, thereby reducing material and energy costs.
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 hydrogel achieves long-term prevention and control of spontaneous combustion by maintaining high water retention and flame retardancy, reducing labor and improving safety and environmental sustainability in coal mines, with controlled gelation and delayed crosslinking for effective oxygen barrier and cooling properties.
Implementation Method 1
a gel-forming material A, prepared by physical blending of a biodegradable superabsorbent resin, anionic polyacrylamide, a sesbania gum, and fly ash
Implementation Method 2
biodegradable superabsorbent resin
Implementation Method 3
expandable graphite
Implementation Method 4
expandable graphite, and an aluminum citrate complex in a second weight ratio of (60-78):(20-36):(2-4)
Implementation Method 5
zeolite
Implementation Method 6
an aluminum citrate complex
Data Source
AI summary
The present invention provides a fly ash-based environmentally-friendly hydrogel with a high water retention for preventing and controlling spontaneous combustion of coal in a mine and a preparation method thereof. The hydrogel includes the following raw materials in the following weight percentages: 10% to 30% of a gel-forming material A, 20% to 45% of a crosslinking material B, and water as a balance, where the gel-forming material A is prepared by physical blending of a biodegradable superabsorbent resin, anionic polyacrylamide, a sesbania gum, and fly ash in a weight ratio of (1-3):(0.5-1):(0.5-1):(95-98); and the crosslinking material B is prepared by subjecting zeolite, expandable graphite, and an aluminum citrate complex in a weight ratio of (60-78):(20-36):(2-4) to mixing, dispersing, adsorbing, and freeze-drying. The gel-forming material A is added to water and stirred at room temperature until homogeneous, and then the crosslinking material B is added and stirred until homogeneous to obtain the hydrogel. In the present disclosure, the environmentally-friendly hydrogel with the high water retention is prepared with wastes such as fly ash as a base material, and can be prepared simply with a low cost. In addition, the hydrogel has the advantages of degradability, strong water retention, and a controllable gelation time. The hydrogel can cover and wet a coal body for a long time, and prevent and control the spontaneous combustion of coal in a mine for a prolonged time.