Eutectic Freeze Crystallization for Leachate Purification
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Solution Overview
Problem
Current methods for purifying landfill leachate, such as reverse osmosis and evaporation, face challenges like scaling, high energy consumption, and the need for large land areas, and do not allow for efficient removal and isolation of salts.
Innovation Solution
The method employs eutectic freeze crystallization (EFC) to purify landfill leachate by reducing the temperature to a eutectic point, resulting in the formation of ice and crystalline salts, which are then separated and recovered, allowing for sequential separation of salts and reducing the leachate volume significantly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If reverse osmosis is used to concentrate leachate, then water is removed and leachate concentration increases, but scaling occurs and further concentration becomes impossible
Solution Approach 1:
The patent applies phase transition by freezing leachate to separate water as ice from dissolved salts. The freezing process causes water to transition from liquid to solid phase, leaving concentrated brine and enabling further concentration beyond reverse osmosis limits without scaling issues.
Solution Approach 2:
The patent replaces the mechanical pressure-driven reverse osmosis system with a thermal freezing system. Instead of using high pressure to force water through membranes (which causes scaling), the system uses controlled freezing to achieve separation and concentration.
2Quantity of substance
If evaporation is used to remove water from leachate, then water is removed and leachate volume decreases, but energy consumption increases
Solution Approach 1:
The patent uses freezing (liquid to solid phase transition) instead of evaporation (liquid to gas phase transition). Freezing requires significantly less energy than evaporation because it only needs to remove latent heat of fusion rather than latent heat of vaporization, thereby reducing energy consumption while achieving the same volume reduction.
3Loss of substance
If evaporation is used to solidify salts from leachate, then salts are recovered, but the process requires large land areas and is sensitive to corrosion and scaling
Solution Approach 1:
The patent uses freezing to directly solidify water as ice, leaving salts in concentrated brine form that can be handled in compact equipment. This eliminates the need for large evaporation ponds while reducing corrosion and scaling issues associated with high-temperature evaporation processes.
4Quantity of substance
If recirculation is used to concentrate leachate by absorbing additional contaminants, then concentration increases, but this is now prohibited in several countries
Solution Approach 1:
The patent extracts water from leachate through freezing, separating it from dissolved contaminants. This direct extraction method achieves concentration without requiring recirculation back to the landfill, thereby complying with regulatory prohibitions while still achieving the desired concentration effect.
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
EFC significantly reduces energy consumption compared to evaporation, minimizes scaling issues, and allows for the recovery of pure crystalline salts with commercial value, achieving a volume reduction of over 98% of the leachate.
Implementation Method 1
carrying out eutectic freeze crystallization by reducing the temperature of the leachate to a first eutectic point to obtain a first mixture comprising ice and a first crystalline salt
Implementation Method 2
carrying out eutectic freeze crystallization by reducing the temperature of the leachate to a first eutectic point to obtain a first mixture comprising ice and a first crystalline salt
Data Source
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AI summary
The invention is in the field of landfill leachate, in particular the invention is directed to a method for purifying landfill leachate comprising water, dissociated ions and organic compounds, wherein the method comprises providing the leachate in a eutectic freeze crystallization (EFC) crystallizer and carrying out eutectic freeze crystallization by reducing the temperature of the leachate to a first eutectic point to obtain a first mixture comprising ice and a first crystalline salt. Further the ice and the first crystalline salt are separated into an ice stream and a crystalline salt stream.