Spray-Drying Chelating Agents with Particle Recycling
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Solution Overview
Problem
Existing processes for producing chelating agents in solid form face challenges such as high hygroscopicity and yellowing when contacted with percarbonate, and inefficiencies in gas inlet temperature and particle size management, leading to suboptimal product quality and capacity in spray drying and granulation.
Innovation Solution
A process involving spray-drying or spray-granulation of aqueous solutions of alkali metal salts of methyl glycine diacetic acid, glutamic acid diacetate, and iminodisuccinic acid, followed by separation and milling of fines and lumps, with recycling of these particles to optimize particle size distribution and reduce hygroscopicity, while maintaining low residual moisture content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spray-drying or spray-granulation is used to produce solid chelating agents, then productivity is improved, but the product exhibits high hygroscopicity and yellowing when contacted with percarbonate
Solution Approach 1:
The patent applies parameter changes by optimizing the gas inlet temperature (125-250°C) and controlling the particle size distribution through selective separation and recycling. These parameter adjustments resolve the contradiction by achieving both high productivity through spray-drying and improved product stability with reduced hygroscopicity and peroxide compatibility
Solution Approach 2:
The patent implements discarding and recovering by separating fines (particles <30 μm for powders, <350 μm for granules) and lumps (particles >250 μm for powders, >1,500 μm for granules) from the spray-dried product, then recycling these separated fractions back into the spray-dryer or spray-granulator. This process resolves the contradiction by allowing continuous high-productivity operation while the recycling loop produces a final product with optimized particle size distribution and improved stability characteristics
2Productivity
If gas inlet temperature is increased to improve drying efficiency, then productivity is improved, but particle size control becomes more difficult leading to increased fines and lumps
Solution Approach 1:
The patent applies feedback by implementing a closed-loop system where fines and lumps are separated from the spray-dried product and recycled back into the spray-dryer or spray-granulator. The recycling amount is controlled at 5-50% by weight of the total chelating agent, providing feedback control that maintains optimal particle size distribution while allowing high drying efficiency through increased gas inlet temperature
Solution Approach 2:
The patent implements dynamics by making the particle size distribution dynamic through continuous separation and recycling. Rather than relying solely on static process parameters, the system dynamically adjusts the particle size profile by removing extremes (fines and lumps) and recycling them, allowing the use of higher gas inlet temperatures for improved productivity without sacrificing particle size control
3Manufacturing precision
If separation and milling of fines and lumps is implemented to improve particle size distribution, then manufacturing precision is improved, but device complexity and processing time increase
Solution Approach 1:
The patent applies discarding and recovering by separating fines and lumps from the spray-dried product and recycling them back into the process. This approach achieves improved particle size distribution (manufacturing precision) while avoiding the need for complex downstream milling equipment, as the recycling process itself acts as a size distribution optimization mechanism
Solution Approach 2:
The patent implements merging by combining the separation and particle size optimization functions into the existing spray-drying or spray-granulation process through recycling. Rather than adding separate milling and classification equipment, the system merges these functions into the thermal processing step, reducing overall device complexity while maintaining manufacturing precision
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
The process results in chelating agents with improved hygroscopicity and peroxide stability, achieving a broad or narrow particle diameter distribution and low residual moisture, enhancing product quality and manufacturing efficiency.
Implementation Method 1
introducing an aqueous solution or aqueous slurry of the respective chelating agent (A) into a spray-dryer or spray-granulator, and removing most of said water by spray-drying or spray granulation using a gas with an inlet temperature of 125 to 250° C.
Data Source
AI summary
Process for making a powder or granule containing at least one chelating agent selected from alkali metal salts of methyl glycine diacetic acid (MGDA) and glutamic acid diacetate (GLDA) and iminodisuccinic acid (IDS), said process comprising the steps of (a) introducing an aqueous solution or aqueous slurry of the respective chelating agent (A) into a spray-dryer or spray-granulator, and removing most of said water by spray-drying or spray granulation using a gas with an inlet temperature of 125 to 250° C., (b) withdrawingpowder or granules, respectively, from the spray-dryer or spray-granulator, respectively, (c) separating off fines from said powder or granules, wherein said fines have a maximum particle diameter of 350 μm, (d) separating off lumps from said powder or granules, wherein said lumps have a particle diameter of 1,500 μm or more, (e) milling said lumps to a maximum particle diameter of 500 μm, (f) re-introducing said fines from step (c) and milled lumps from step (e) into the spray-dryer or spray-granulator, wherein the share of fines is in the range of from 0.5 to 20% by weight of the total chelating agent (A) withdrawn in step (b) and the share of milled lumps is in the range of from 5 to 60% by weight of the total chelating agent (A) withdrawn in step (b).