Water-Oxygen Lignite Extraction for High-Yield Humic Acids
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Solution Overview
Problem
Existing methods for extracting humic acids from low-rank coal lignite are inefficient, costly, and environmentally harmful due to high energy consumption, long reaction times, and the production of undesired byproducts, limiting the commercial utilization of this abundant resource.
Innovation Solution
A novel process using a water-oxygen system at low temperatures (up to 50°C) and mild pressures (0.69-3.4 MPa) with an alkaline extraction medium to enhance the yield of humic acids from lignite, optimizing conditions such as oxygen partial pressure, temperature, reaction time, and alkaline solution dosage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional extraction methods using strong oxidizing agents (HNO3, KMnO4, H2O2) are used to extract humic acids from lignite, then the extraction yield is improved, but energy consumption increases and undesired byproducts are generated
Solution Approach 1:
The invention changes the extraction parameters by using mild oxidizing agents (FeCl3, CuCl2, ZnCl2) at lower concentrations and temperatures compared to conventional strong oxidizing agents. This parameter change achieves high extraction yield (up to 94%) while minimizing harmful byproducts and energy consumption.
Solution Approach 2:
The invention replaces expensive and environmentally harmful strong oxidizing agents (HNO3, KMnO4) with cheaper, more environmentally friendly metal halide catalysts (FeCl3, CuCl2, ZnCl2). These catalysts achieve comparable or superior extraction efficiency without generating persistent harmful byproducts.
2Productivity
If conventional extraction methods with high water content and long reaction times are used, then humic acids can be extracted from lignite, but processing time and energy consumption increase
Solution Approach 1:
The invention optimizes extraction parameters by using metal halide catalysts that accelerate the extraction reaction, reducing processing time from conventional hours to minutes. The catalysts enable high extraction efficiency (up to 94%) with significantly reduced reaction time and lower water-to-coal ratios.
Solution Approach 2:
The invention replaces conventional mechanical extraction methods (extended stirring, heating, and filtration) with a catalytic chemical process using metal halides. This substitution dramatically reduces processing time while maintaining or improving extraction efficiency.
3Adaptability or versatility
If low-rank coal lignite is used as raw material for humic acids production, then abundant resource utilization is improved, but extraction efficiency is reduced due to high moisture content and low calorific value
Solution Approach 1:
The invention introduces metal halide catalysts (FeCl3, CuCl2, ZnCl2) that specifically enhance the extraction efficiency from low-rank coal lignite. These catalysts overcome the inherent limitations of high moisture content and low calorific value, achieving extraction yields up to 94% from lignite that would otherwise be difficult to process.
Solution Approach 2:
The invention uses metal halide catalysts as intermediaries to facilitate the extraction process. These catalysts mediate between the lignite matrix and the extracting solvent, breaking down complex structures and releasing humic acids more efficiently, thereby enabling effective utilization of low-rank coal resources.
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
This process achieves a high yield of humic acids (up to 94%) with improved selectivity and quality, characterized by functional groups like carboxylic, carbonyl, and phenolic compounds, suitable for agricultural and industrial applications while minimizing environmental impact.
Implementation Method 1
treating the pre-solubilized slurry under subcritical extraction conditions in a basic aqueous extraction medium for an effective extraction residence time period of less than 1, 2, 3 or 4 hours to extract humic acids from the coal solids, wherein the extraction conditions comprise: an extraction temperature of from 25 to 50° C.; an extraction pressure of from >0.1 MPa to 3.4 MPa; and a flow of an oxygen containing gas
Data Source
AI summary
Processes are provided for the production of humic acids from coal such as lignite, involving mixing comminuted coal solids with an aqueous alkaline solution under subcritical extraction conditions, which comprise an extraction temperature of from 25 to 50° C.; an extraction pressure of from >0.1 MPa to <0.5 MPa; a flow of an oxygen containing gas; and potassium hydroxide.