Physical-Chemical Composite Inhibitor for Low-Rank Coal Spontaneous Combustion
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Solution Overview
Problem
Low-rank coal in coal mines is prone to spontaneous combustion due to its active functional groups, leading to fires and environmental hazards, with existing inhibitors either lacking long-term effectiveness or posing safety risks and being costly.
Innovation Solution
A physical-chemical composite inhibitor composed of a chelate generated by proanthocyanidin and calcium chloride combined with attapulgite, which is sprayed onto coal regions to inhibit oxidation by forming stable structures that block oxygen contact and capture free radicals, providing both moisture retention and long-term inhibition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If physical inhibitors (foams, gels, water absorbent salts) are used to control spontaneous combustion, then moisture retaining and temperature lowing effects are achieved, but the inhibition effect disappears when moisture retaining properties are exhausted and the risk of spontaneous combustion is not essentially reduced
Solution Approach 1:
The patent combines physical inhibitor (attapulgite) and chemical inhibitor (chelate of proanthocyanidin and calcium chloride) into a composite inhibitor system. The attapulgite provides moisture retaining and temperature lowing effects, while the chelate chemically reacts with active functional groups in coal to form stable structures, achieving both immediate temperature control and long-term inhibition of oxidation reactions.
2Reliability
If chemical inhibitors (oxidants such as perchlorates, permanganates, peroxides) are used to control spontaneous combustion, then active functional groups are reduced and free radical chain-cycle reaction is interrupted, but heat is released during reaction resulting in increase in temperature of coal bodies and oxidants themselves have a large risk of fires
Solution Approach 1:
The patent uses proanthocyanidin, a naturally occurring compound with short-lived, controlled reactivity, that reacts with active functional groups in coal to form stable chelate structures with calcium chloride. This approach provides reliable inhibition of spontaneous combustion without the persistent fire hazards and excessive heat release associated with traditional oxidant-based chemical inhibitors.
3Reliability
If chemical inhibitors (anti-aging agents, catechins) are used to control spontaneous combustion, then spontaneous combustion is inhibited, but they are costly resulting in difficulty in actual field use
Solution Approach 1:
The patent employs proanthocyanidin, a cost-effective naturally occurring compound, combined with calcium chloride to form a stable chelate. This combination provides effective inhibition of spontaneous combustion at a fraction of the cost of traditional chemical inhibitors like anti-aging agents and catechins, making it economically viable for actual field use in coal mines.
4Quantity of substance
If low-rank coal with active functional groups is left untreated, then coal resources are available for use, but oxidation spontaneous combustion easily occurs leading to fires and release of toxic gases
Solution Approach 1:
The patent applies a composite inhibitor containing chelate and attapulgite to coal bodies before oxidation spontaneous combustion can occur. The chelate chemically reacts with active functional groups to form stable structures, while attapulgite provides moisture retaining and physical barrier effects, preventing oxidation reactions and toxic gas release while allowing the coal resources to remain available for safe utilization.
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 composite inhibitor effectively reduces the oxidation activity of low-rank coal, achieving up to 86% inhibition rate by stabilizing active functional groups and forming insulating layers, while being environmentally friendly and economically viable.
Implementation Method 1
The chelate is generated by chelation of proanthocyanidin with calcium chloride
Implementation Method 2
Low-temperature oxidation of coal is a complicated process of free radical chain-cycle reaction of a coal-oxygen complex
Implementation Method 3
The physical inhibitors mainly are foams, gels, and water absorbent salts (such as NaCl, MgCl2 and CaCl2). These physical inhibitors can change physical conditions around the coal body and inhibit spontaneous combustion of coal mainly by moisture retaining, heat absorption and temperature lowing
Implementation Method 4
A stable oxide insulating layer such as MgO and Al2O3 insulating layer will be formed, which can block a coal body from contacting with oxygen
Implementation Method 5
These physical inhibitors can change physical conditions around the coal body and inhibit spontaneous combustion of coal mainly by moisture retaining, heat absorption and temperature lowing
Data Source
AI summary
Disclosed is a physical-chemical composite inhibitor for controlling spontaneous combustion of low-rank coal, and methods of preparing and using the same. The composite inhibitor consists of a chelate and attapulgite, the chelate is generated by chelation of proanthocyanidin with calcium chloride. The composite inhibitor has moisture-absorbing and moisture-retaining effect, and can reduce water dissipation at low temperature. A stable oxide insulating layer such as MgO and Al2O3 insulating layer can be formed at high temperature, which can block a coal body from contacting with oxygen. In addition, the composite inhibitor can capture hydroxyl free radicals generated during the chain-cycle reaction and destroy peroxide free radicals, and can also interact with an active moiety in coal to form a stable structure such as ether linkage and hydrogen bonding, thereby achieving permanent inhibition of low-rank coal.