Wash Column Operating Window Expansion via Freezing Point Depression
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Solution Overview
Problem
The operating window of forced transport wash columns is limited, restricting their production capacity and purification efficiency due to maximum temperature differences across the wash front, which leads to recrystallization of wash liquid and loss of pore volume, making it difficult to maintain counter-current washing processes economically and technically.
Innovation Solution
Introducing a compound or composition between the wash front and the product outlet, or in the melting circuit that is miscible with the product suspension, reducing the equilibrium temperature and extending the operating window without adversely affecting product quality, thereby increasing production capacity and purification efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a forced transport wash column operates with a large temperature difference across the wash front to increase production capacity, then more crystals can be processed, but the wash liquid recrystallizes and loses pore volume, disrupting the counter-current washing process
Solution Approach 1:
The invention introduces a compound or composition that modifies the temperature parameters of the system. By adding a substance that lowers the equilibrium temperature or alters the thermal properties of the wash liquid, the temperature difference across the wash front can be increased without causing unwanted recrystallization. This parameter change allows the system to operate at higher productivity while maintaining the necessary temperature gradient for effective counter-current washing.
Solution Approach 2:
The introduced compound or composition acts as an intermediary substance that mediates between the temperature difference requirement and the recrystallization prevention need. This intermediary modifies the thermal behavior of the wash liquid or the crystal bed, allowing heat transfer without triggering phase changes that would disrupt the washing process. The intermediary enables the system to tolerate larger temperature differences while maintaining operational reliability.
2Productivity
If the temperature difference across the wash front is increased to enhance production capacity, then more material can be separated, but the operating window is exceeded and recrystallization occurs
Solution Approach 1:
By introducing a compound or composition that alters the thermal parameters of the system, the invention effectively expands the operating window. The added substance changes the temperature-at which equilibrium occurs or modifies the heat capacity and thermal conductivity of the medium, allowing the system to operate at higher temperature differences without exceeding the original stability limits. This parameter modification enables broader operational flexibility and higher production capacity.
Solution Approach 2:
The invention introduces dynamic adaptability to the system by adding a compound that can adjust the thermal behavior in response to operating conditions. This allows the system to dynamically accommodate larger temperature differences without losing stability, effectively making the operating window more flexible and adaptable to high-productivity requirements.
3Productivity
If the wash column operates at high production capacity with large temperature differences, then output increases, but maintaining counter-current washing becomes economically and technically difficult
Solution Approach 1:
The introduced compound or composition simplifies the thermal management at high production capacities by fundamentally changing the temperature parameters of the system. Instead of requiring complex control mechanisms to manage heat transfer and prevent recrystallization, the additive inherently stabilizes the thermal behavior, allowing high-capacity operation with simpler process control and reduced operational complexity.
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 approach significantly expands the operating window of wash columns, enhancing production capacity and maintaining high purification efficiency by reducing temperature differences and preventing recrystallization of wash liquid, while ensuring the product quality remains unaffected.
Implementation Method 1
The freezing point depression of the mixture to be crystallized increases with increasing impurity concentration.
Implementation Method 2
At the feed side of the wash column a porous bed of crystals is formed by removing mother liquor through one or more filters.
Implementation Method 3
In the thus-formed bed the relatively pure crystals are still in contact with the portion of impure mother liquor that could not be removed by the filtration. After forming the bed, the forced transport of the bed to the product side of the wash column
Implementation Method 4
At the product side of the wash column the porous crystal bed is disintegrated by means of a mechanical device like a rotating scraper knife or by means of the impulse of a circulating liquid stream.
Data Source
AI summary
The invention is directed to an improvement in operation of wash columns, and more in particular to an apparatus for separating solid particles from a slurry and to a process for separating solid particles from a mother liquor slurry. The apparatus of the invention comprises a wash column (1), which comprises a melting circuit (8,10,11,21), wherein means (22,23) are present to introduce a compound or composition to said wash column between a wash front (6b) formed in said wash column in operation and a product outlet and/or in the melting circuit. The process of the invention comprises separating the liquid from the solid particles by filtration with the aid of at least one filtering element (4), while a packed bed of solid particles coming from the mother liquid slurry forms near said filtering element (4), and wherein a wash front (6b) forms which is obtained by bringing a washing liquid in counter current to the solid particles in the bed, the bed being subjected to a movement in the direction of said wash front (6b), while a product stream comprising the material of said solid particles is obtained by continuously discharging a portion of said washing liquid, wherein a portion of said bed is continuously disintegrated, characterized in that a compound or composition is introduced into said wash column (1) between the wash front (6b) and a product outlet and/or in a melting circuit (8,10,11,21), and wherein the introduction of the said compound or composition decreases the equilibrium temperature of the contents of the melting circuit (8,10,11,21), further characterized by the feature that the introduced compound or composition is completely miscible with the product suspension and/or molten product being present in the said melting circuit (8,10,11,21).