Soluble Potassium Sulfate Recrystallization
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Solution Overview
Problem
Existing methods for producing potassium sulfate often result in a product with poor dissolution properties, making it unsuitable for use in spray equipment and liquid fertilizer systems, which requires high-quality, swiftly dissolving potassium sulfate to prevent clogging and ensure efficient application.
Innovation Solution
A method involving the recrystallization of crude potassium sulfate with a potassium content of 15 wt% or higher, incorporating a solid material removal step, acid addition before or during crystallization, and controlled particle size to achieve a product with less than 0.05 wt% insoluble material, pH below 6, and specific particle size distribution, ensuring high solubility and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional production methods (Mannheim process, double salt decomposition) are used to produce potassium sulfate, then production volume and cost are adequate, but the product has poor dissolution properties and high insoluble content making it unsuitable for fertigation and foliar sprays
Solution Approach 1:
The patent applies parameter changes by adjusting pH (adding acid to reach pH 4-6), temperature (heating to 50-95°C during dissolution, then cooling for crystallization), and particle size control (sieving to achieve d90 ≤ 0.6mm). These parameter modifications transform crude potassium sulfate with poor dissolution properties into a product suitable for fertigation and foliar sprays, resolving the contradiction between maintaining production simplicity and improving dissolution reliability.
Solution Approach 2:
The patent utilizes phase transitions through dissolution (solid to liquid) followed by crystallization (liquid to solid). The crude potassium sulfate is dissolved in water at elevated temperature, then the solution is cooled to crystallize purified potassium sulfate with controlled particle size. This phase transition process effectively removes insoluble impurities while producing high-quality product, resolving the contradiction without requiring complex production methods.
2Manufacturing precision
If recrystallization process is applied to improve dissolution properties, then solubility and particle size control are improved, but additional process steps and equipment are required
Solution Approach 1:
The patent segments the purification process into distinct operational steps: dissolution, filtration to remove insoluble material, acid addition for pH control, cooling, and sieving for particle size separation. The sieving step specifically segments particles by size (d90 ≤ 0.6mm, d10 ≥ 0.02mm) to ensure optimal dissolution properties while maintaining a relatively simple overall process flow suitable for industrial implementation.
3Speed
If acid is added during crystallization to control pH below 6, then dissolution speed is improved, but additional chemical handling and safety requirements are introduced
Solution Approach 1:
The patent converts the potentially harmful effect of acid (corrosivity) into a beneficial effect by carefully controlling pH to the 4-6 range. This pH optimization accelerates dissolution speed (achieving ≥90% dissolution in 3 minutes) while minimizing corrosion risks to spray equipment and handling safety issues. The acid addition is precisely controlled to achieve the optimal pH window that balances dissolution performance with safety.
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 method produces potassium sulfate with improved solubility characteristics, achieving at least 90% dissolution in 3 minutes, reduced insoluble content, and optimal pH, enhancing its usability in foliar sprays and fertigation systems while minimizing equipment clogging and improving application efficiency.
Implementation Method 1
the crude potassium sulfate is dissolved
Implementation Method 2
potassium sulfate is crystallized
Implementation Method 3
wherein the particle size of the crystalline material is controlled to be within the ranges provided, optionally with sieving and/or grinding, preferably by sieving such that the resulting potassium sulfate crystalline material conforms with the following parameters: the amount of insoluble material is less than 0.05 wt%, a 1% solution of the potassium sulfate has a pH below 6
Data Source
AI summary
The invention relates to a method for producing for producing soluble potassium sulfate by recrystallization of crude potassium sulfate wherein the crude potassium sulfate contains an amount of potassium, calculated as K2O of about 15 wt% or higher, preferably about 40 wt% or higher and has either more than about 0.07 wt% insoluble material, and/or a dissolution speed wherein at 3 min dissolution of 100 gram product in 1 L cold water (20 °C), without stirring the amount of dissolved potassium sulfate of less than about 90% and/or a pH of about 6 or higher as a 1 % dissolved crude potassium sulfate, wherein the method comprises the following steps: crude potassium sulfate is dissolved, the dissolved potassium sulfate is subjected to a solid material removal step, potassium sulfate is crystallized, while optionally an acid is provided before, during or after the crystallization step of the potassium sulfate and whereafter the obtained potassium sulfate is separated and dried, wherein the particle size of the crystalline material is controlled to be within the ranges provided, optionally with sieving and/or grinding, preferably by sieving, such that the resulting potassium sulfate crystalline material conforms with the following characteristics: the amount of insoluble material is less than about 0.05 wt%, a 1 wt% solution of the potassium sulfate has a pH below about 6, and/or 1 pH unit lower than the pH of the crude potassium sulfate, the fraction obtained after crystallization has an average particle size within the following parameters: (i) d90 < about 0.6 mm, (ii) d10 > about 0.02 mm, and (iii) dust amounts to about 0.4 wt% or less, whereby the potassium sulfate contains more than 51 % potassium, calculated as K2O.