Crystallization Degree Control in Indirect Heat Exchangers
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Solution Overview
Problem
Existing closed-loop control structures for crystallizative removal of target products in heat exchangers are inadequate in maintaining a stable degree of crystallization, especially when market demand fluctuates, leading to inefficiencies and potential apparatus damage due to unstable pressure and permeability issues.
Innovation Solution
A process that uses a heat exchanger with a secondary and primary chamber, where the desired degree of crystallization is maintained by balancing the heat flow of crystallization in the secondary chamber with the overall heat flow in and out, employing a process computer to adjust the fluid cooling medium temperature and flow, ensuring the target product content in the liquid residual phase is ≥70% by weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the degree of crystallization is increased to improve separation efficiency, then the separating action is improved, but the pressure and permeability become unstable leading to apparatus damage
Solution Approach 1:
The patent implements a closed-loop control system that continuously monitors the degree of crystallization and adjusts operating parameters (temperature, residence time) to maintain stability. This feedback mechanism prevents the pressure and permeability instability that would otherwise occur at high crystallization degrees, allowing the system to operate at optimal separating action without apparatus damage.
Solution Approach 2:
The patent dynamically adjusts process parameters including temperature of the liquid phase, residence time in the heat exchanger, and cooling medium flow rate to maintain the degree of crystallization within a stable range (5-50%). By changing these parameters in response to process conditions, the system achieves high separating action while preventing the harmful effects of excessive crystallization.
2Reliability
If the degree of crystallization is maintained stable to prevent apparatus damage, then the reliability is improved, but the space-time yield may be reduced
Solution Approach 1:
The patent employs dynamic control of the crystallization process, allowing the degree of crystallization to fluctuate within an optimized range (5-50%) rather than maintaining a fixed value. The system continuously adapts operating parameters to maintain stability while maximizing productivity, achieving both reliable operation and high space-time yield through responsive parameter adjustment.
Solution Approach 2:
By optimizing and dynamically adjusting key parameters such as temperature, residence time, and cooling rate, the patent achieves the maximum stable degree of crystallization within the 5-50% range. This allows the system to operate at the boundary of stability, maximizing space-time yield while preventing apparatus damage from excessive crystallization.
3Productivity
If the heat flow is increased to accelerate crystallization, then the productivity is improved, but the degree of crystallization becomes unstable
Solution Approach 1:
The closed-loop control system monitors the degree of crystallization in real-time and adjusts the heat flow (cooling rate) to maintain stability. When crystallization accelerates too rapidly, the system reduces heat removal; when it slows down, the system increases cooling. This feedback control enables high productivity through accelerated crystallization while preventing instability in the degree of crystallization.
Solution Approach 2:
The patent employs periodic or pulsed cooling patterns rather than continuous maximum cooling. By applying heat flow in controlled cycles, the system maintains high average crystallization rate while allowing the system to respond to and recover from transient instabilities, thus maintaining overall degree of crystallization stability.
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 stabilizes the degree of crystallization, preventing apparatus damage and maintaining efficient separation by continuously adjusting the crystallization process in response to market demand changes, ensuring high separating action and space-time yield.
Implementation Method 1
By virtue of the transfer of heat from liquid phase P supplied to the secondary chamber through the material dividing wall (the heat transfer area) which divides the secondary chamber and the at least one primary chamber into the coolant flowing in the at least one primary chamber
Implementation Method 2
through the material dividing wall which serves as an area for transferring heat out of the secondary chamber into the at least one primary chamber
Implementation Method 3
the liquid phase P cools until the saturation limit of liquid phase P with target product X is exceeded and oversaturation is counteracted by formation of crystals of the target product X
Implementation Method 4
the liquid phase P cools until the saturation limit of liquid phase P with target product X is exceeded and oversaturation is counteracted by formation of crystals of the target product X
Data Source
AI summary
A process for continuously removing a target product X in the form of fine crystals from a liquid phase P comprising the target product X and constituents other than the target product X by cooling suspension crystallization in the secondary chamber, into which the liquid phase P flows continuously, of an indirect heat exchanger with simultaneous continuous flow of a coolant through the primary chamber of the indirect heat exchanger and continuous withdrawal of a crystal suspension S having a degree of crystallization Y from the secondary chamber, in which the degree of crystallization Y is adjusted on the basis of a heat balance conducted continuously with the aid of a process computer.