Fine Coal Dewatering via Hydrophobic Liquid Agglomeration
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Solution Overview
Problem
Fine coal cleaning processes, such as froth flotation and selective agglomeration, face challenges in efficiently removing mineral matter and achieving low moisture content, leading to high costs and environmental concerns due to the discarding of ultrafine particles, and existing methods like thermal drying are energy-intensive and costly.
Innovation Solution
A method involving the use of a hydrophobic liquid to displace water from fine coal particles during high-shear agitation, allowing for the separation of coal from mineral matter and water, with the hydrophobic liquid being recycled and the process achieving moisture levels comparable to thermal drying without excessive heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If froth flotation is used to clean fine coal, then mineral matter is removed, but the clean coal product contains large amounts of water making it difficult to handle
Solution Approach 1:
The patent changes the physical-chemical parameters of the cleaning process by using oil agglomeration instead of water-based flotation. Oil is added to the coal slurry and agglomerates with coal particles, changing the separation mechanism from hydrophobic-hydrophilic interaction to oil-coal agglomeration. This parameter change allows for effective cleaning while producing a product with lower moisture content that is easier to handle.
Solution Approach 2:
The patent introduces oil as an intermediary substance that mediates between the coal particles and water. The oil forms agglomerates with coal particles, acting as a bridge that allows separation from mineral matter while simultaneously reducing the water content in the final product. This intermediary approach resolves the contradiction by providing a different separation mechanism that doesn't leave excess water on the coal surface.
2Quantity of substance
If selective agglomeration with oil is used to clean fine coal, then lower moisture products are achieved, but high dosages of oil are required
Solution Approach 1:
The patent optimizes the oil dosage parameter by conducting systematic experiments to determine the minimum effective concentration. By changing the oil dosage from high levels (5-30% by weight) to optimized lower levels, the patent achieves effective cleaning and dewatering while minimizing oil consumption and cost.
Solution Approach 2:
The patent applies partial action by using just enough oil to achieve the desired cleaning and dewatering效果, rather than excessive oil dosage. The optimized oil concentration is sufficient to form stable agglomerates and displace water from coal particles, but not in excess amounts that would increase costs and require more complex recovery systems.
3Quantity of substance
If thermal drying is used to reduce moisture content, then low moisture levels are achieved, but energy consumption becomes excessive
Solution Approach 1:
The patent replaces the thermal drying system with a mechanical-chemical dewatering system based on oil agglomeration. Instead of using heat energy to evaporate water, the process uses oil-coal agglomeration and mechanical separation to physically remove water from the coal particles. This substitution of thermal energy with mechanical-chemical processes dramatically reduces energy consumption while achieving comparable moisture reduction.
Solution Approach 2:
The patent changes the dewatering mechanism from thermal evaporation to oil-based agglomeration and physical separation. By changing the fundamental parameter of how water is removed (from heat-driven evaporation to chemistry-driven agglomeration followed by mechanical separation), the process achieves low moisture content without the excessive energy consumption of thermal drying.
4Manufacturing precision
If ultrafine particles are processed through conventional cleaning methods, then cleaning is achieved, but dewatering costs become prohibitive
Solution Approach 1:
The patent applies a universal oil agglomeration process that effectively handles ultrafine particles across different size ranges. The same oil-based mechanism that works for coarser particles also effectively treats ultrafine particles, providing a multi-functional solution that eliminates the need for specialized expensive dewatering equipment for different particle sizes. This universal approach makes ultrafine particle processing economically viable.
Solution Approach 2:
The patent replaces complex mechanical dewatering systems (centrifuges, filters, presses) with a simpler oil agglomeration and phase separation system. For ultrafine particles, this substitution is particularly valuable as it avoids the need for expensive specialized equipment while achieving effective dewatering at much lower cost.
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 effectively reduces moisture content in fine coal to less than 8% by weight, comparable to thermal drying, while minimizing the use of hydrophobic liquids and enabling the recycling of the spent liquid, thus reducing costs and environmental impact.
Implementation Method 1
Higher-rank coal particles are usually hydrophobic and, therefore, can be attracted to air bubbles that are also hydrophobic via a mechanism known as hydrophobic interaction
Implementation Method 2
fine coal (approximately 0.15 mm and smaller) is cleaned by froth flotation
Implementation Method 3
removing the process water from both the clean coal and refuse products to the levels that can usually be achieved by thermal drying
Data Source
AI summary
Fine coal is cleaned of its mineral matter impurities and dewatered by mixing the aqueous slurry containing both with a hydrophobic liquid, subjecting the mixture to a phase separation. The resulting hydrophobic liquid phase contains coal particles free of surface moisture and droplets of water stabilized by coal particles, while the aqueous phase contains the mineral matter. By separating the entrained water droplets from the coal particles mechanically, a clean coal product of substantially reduced mineral matter and moisture contents is obtained. The spent hydrophobic liquid is separated from the clean coal product and recycled. The process can also be used to separate one type of hydrophilic particles from another by selectively hydrophobizing one.