DTB Crystallizer Grain Size Control via Fine Crystal Recirculation
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Solution Overview
Problem
Existing methods for producing coarse-grained ammonium sulphate in draft tube baffled (DTB) crystallizers face periodic fluctuations in grain size due to oversaturation and spontaneous nucleation, leading to alternating phases of fine and coarse grain production, which affects the consistency and yield of the product.
Innovation Solution
A method where a fine crystal suspension is continuously recirculated from the clarifying zone into the internal circuit of the DTB crystallizer without prior dissolution, acting as seeding material for the growth of coarse crystallate, ensuring a constant grain size spectrum and minimizing installation outlay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a DTB crystallizer is used to produce coarse-grained ammonium sulphate, then the product grain size can reach 2-3 mm, but periodic fluctuations occur in grain size with alternating phases of fine and coarse grain production
Solution Approach 1:
The invention applies preliminary action by continuously introducing fine crystal suspension into the crystallizer before spontaneous nucleation can occur. This pre-seeding ensures that crystal growth occurs on existing nuclei rather than allowing uncontrolled spontaneous nucleation, thereby maintaining consistent grain size and preventing periodic fluctuations between fine and coarse grain phases.
Solution Approach 2:
The invention implements feedback by continuously monitoring and adjusting the amount of fine crystal suspension introduced into the crystallizer. This closed-loop control ensures that the seeding rate responds to process conditions, maintaining optimal crystal growth conditions and preventing deviations that would lead to grain size fluctuations.
2Manufacturing precision
If fine crystal suspension is continuously recirculated from the clarifying zone into the internal circuit, then grain size consistency is improved, but additional equipment for suspension production is required
Solution Approach 1:
The invention applies self-service by utilizing the clarifying zone's existing function to produce fine crystal suspension as a byproduct of the normal crystallization process. Instead of requiring separate equipment to generate seeding material, the system repurposes the clarifying zone's output, eliminating the need for additional suspension production equipment while maintaining grain size consistency.
Solution Approach 2:
The invention merges two functions: the clarifying zone simultaneously performs both clarification of the mother liquor and production of fine crystal suspension for seeding. By combining these functions into a single zone, the system eliminates the need for separate seeding equipment and reduces overall installation complexity while maintaining precise grain size control.
3Use of energy by moving object
If fine crystal suspension is recirculated without prior dissolution, then energy consumption is reduced, but the mechanism for maintaining constant grain size spectrum must be optimized
Solution Approach 1:
The invention applies continuity of useful action by maintaining constant recirculation of fine crystal suspension without interruption or dissolution cycles. This continuous seeding action ensures uninterrupted crystal growth on nuclei, maintaining constant grain size spectrum while avoiding the energy consumption associated with periodic dissolution and re-crystallization cycles.
Solution Approach 2:
The invention optimizes parameter changes by adjusting the recirculation rate and concentration of fine crystal suspension to achieve the desired grain size spectrum. By carefully controlling these parameters, the system maintains precise grain size control while operating in the energy-efficient mode of direct recirculation without dissolution.
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 production of coarse-grained ammonium sulphate with a consistent grain size of 2.0-3.0 mm, maintaining high yield and reducing cyclical fluctuations, while eliminating the need for additional equipment or energy for seeding material production.
Implementation Method 1
crystallization of an ammonium sulphate solution in a crystallization stage
Implementation Method 2
spontaneous nucleation occurs suddenly with a myriad of very fine crystals
Implementation Method 3
During the course of the operating period, the size of the formed crystals initially increases constantly
Implementation Method 4
a heat exchanger is connected into the external circuit and elevates the temperature of the clarified solution and thus the power of the solvent to dissolve ammonium sulphate
Data Source
AI summary
Method for the production of a coarse-grained ammonium sulphate product by crystallization and installation for carrying out the method from an ammonium sulphate solution in a DTB type crystallizer having an internal suspension circuit and a clarifying zone, from which a clarified partial flow of solution is constantly drawn off into an external circuit, is heated in a heat exchanger to dissolve the solids contained therein and is guided back as a clear solution into the lower region of the crystallizer. A fine crystal suspension flow is drawn off from the clarifying zone as a further partial flow and guided back into the internal circuit of the crystallization stage without any previous dissolution of the solid proportion contained therein.