Crystallizer Seed Control for Particle Size Distribution
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Solution Overview
Problem
Existing crystallization methods, such as DTB and Oslo crystallizers, face cyclical fluctuations in the average particle size of ammonium sulphate crystallate, leading to alternating phases of coarse and fine particles due to oversaturation and spontaneous seed generation, which affects the consistency of particle size distribution.
Innovation Solution
A method involving continuous internal circulation of an oversaturated solution in a crystallization stage, with controlled seed suspension introduction based on measured particle size distribution, where a partial flow of clarified solution is heated and recycled, and fresh solution is supplied to maintain constant particle size, using a seed generation stage for producing seed crystals through flash crystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If internal circulation is used in DTB crystallizer to produce coarse particles, then particle size increases, but cyclical fluctuations in particle size distribution occur due to spontaneous seed generation
Solution Approach 1:
The patent applies preliminary action by continuously adding pre-formed seed crystals to the crystallization process before spontaneous nucleation can occur. This proactive introduction of seeds controls the crystallization process, ensuring that crystals grow on existing seeds rather than forming new spontaneous nuclei, thereby maintaining consistent particle size distribution and preventing cyclical fluctuations.
Solution Approach 2:
The patent implements feedback control by continuously monitoring particle size distribution and using this information to regulate the addition rate of seed crystals. The measured particle size data feeds back to the control system, which adjusts seed crystal addition to maintain desired particle size consistency, preventing both excessive fine particle formation and oversize crystal growth.
2Manufacturing precision
If external circulation and heating are used to dissolve fine crystals, then fine particle removal improves, but equipment complexity increases
Solution Approach 1:
The patent applies the extraction principle by removing fine crystals from the main crystallization process through external circulation and selective dissolution. The external circulation system extracts fine particles from the crystallizer, dissolves them in a separate heating zone, and returns the clarified solution to the crystallizer, thereby separating the fine particle removal function from the main crystallization process.
Solution Approach 2:
The patent uses an intermediary approach by introducing a separate external circulation loop with dedicated heating and dissolution equipment. This intermediary system handles the delicate task of fine crystal dissolution without directly interfering with the main crystallization process, allowing independent optimization of dissolution conditions while maintaining crystallization stability.
3Manufacturing precision
If seed crystals are continuously added to control particle size, then particle size distribution improves, but production cost increases
Solution Approach 1:
The patent applies discarding and recovering by continuously removing fine crystals through external circulation, dissolving them, and recovering the dissolved substance to be reincorporated into the crystallization process. This recovery loop reduces the need for continuous external seed crystal addition, as the dissolved fine crystals are reused rather than discarded, thereby reducing seed crystal consumption while maintaining particle size control.
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 ensures a consistent medium to coarse particle size distribution with reduced equipment outlay, preventing uncontrolled seed generation and maintaining stable production by continuously monitoring and adjusting seed crystal introduction to match the desired particle size.
Implementation Method 1
The oversaturation of the solution is produced by evaporation of the solvent in the crystallization stage
Implementation Method 2
a clarification region of the crystallization stage, in which in contrast to the base region thereof a clarified solution is present having a solids proportion consisting substantially of seed crystals and fine crystals
Implementation Method 3
a partial flow is drawn off, is heated in an external circuit and, after dissolution of the solids proportion
Implementation Method 4
using a seed generation stage for producing seed crystals through flash crystallization
Data Source
AI summary
The invention proposes a method and a device for continuously producing a crystallite, wherein a metered amount of seed crystals is fed continuously to the internal solution circuit of a crystallizer, in particular a DTB crystallizer, through a crystallization seed line from a seed generator preferably designed as a flash crystallizer. The amount of seed crystals fed is controlled by an electronic control system as a function of a measured value determined by a sensor, said value being representative of the particle size distribution of the crystallites in the solution in the internal circuit in the crystallizer. By way of a line, the seed generator receives a partial stream of the external solution circuit of the crystallizer, said external circuit being routed through a line. Excess fine crystalline suspension can be fed back to the external circuit from the seed generator by way of a return line.