Potassium Nitrate Purification via Stepwise Cooling
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Solution Overview
Problem
The chemical glass-strengthening process generates solid waste containing potassium nitrate and sodium nitrate, where the ion exchange reaction leads to increased sodium nitrate concentration, rendering the molten potassium nitrate unusable, resulting in waste and increased manufacturing costs.
Innovation Solution
A purification method involving heating the solid waste to a melting temperature, cooling it at specific rates to crystallize potassium nitrate, and collecting it, with optional additional steps to further purify the crystals, utilizing a series of tanks and temperature control systems to recover and recycle potassium nitrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ion exchange reaction is conducted repeatedly using the same molten potassium nitrate, then the sodium nitrate concentration increases, but the reaction cannot be continuously conducted and glass surface strength improvement is limited
Solution Approach 1:
The patent applies parameter changes by controlling the cooling rate to separate potassium nitrate from sodium nitrate based on their different solubility characteristics at different temperatures. By changing the cooling rate parameter, the system achieves continuous purification and reuse of potassium nitrate, resolving the contradiction between continuous operation capability and potassium nitrate usability.
Solution Approach 2:
The patent utilizes phase transitions by cooling the molten salt mixture to crystallize potassium nitrate while keeping sodium nitrate in solution. This phase transition allows for the separation and recovery of potassium nitrate, enabling continuous operation without accumulating sodium nitrate contamination.
2Loss of substance
If the reacted molten salt is diluted with pure molten potassium nitrate, then the concentration of sodium nitrate is reduced, but the manufacturing cost increases due to large amounts of pure potassium nitrate required
Solution Approach 1:
The patent uses phase transitions through controlled cooling to crystallize and recover potassium nitrate from the reacted molten salt. This eliminates the need for dilution with pure potassium nitrate, reducing manufacturing costs while achieving high recovery rates.
Solution Approach 2:
By changing the temperature parameter through controlled cooling rates, the patent achieves efficient separation and recovery of potassium nitrate, making the process economically viable without requiring additional pure potassium nitrate input.
3Ease of manufacture
If the reacted molten salt is discarded after ion exchange reaction, then the process is simple, but waste is generated and environmentally unfriendly
Solution Approach 1:
The patent employs phase transitions by cooling the reacted molten salt to crystallize potassium nitrate, which is then filtered and reused. This simple yet effective method prevents waste generation and environmental pollution while maintaining process simplicity.
Solution Approach 2:
Instead of discarding the reacted molten salt, the patent recovers potassium nitrate through controlled cooling and crystallization. This recovery process eliminates environmental pollution while keeping the manufacturing process simple and efficient.
4Productivity
If fast cooling is applied to crystallize potassium nitrate, then the crystallization rate is high, but the purity of potassium nitrate crystals may be reduced
Solution Approach 1:
The patent applies periodic action by using a two-stage cooling process: first rapid cooling to achieve high crystallization rate, then slow cooling to purify the crystals. This periodic variation in cooling rate simultaneously achieves high productivity and high crystal purity.
Solution Approach 2:
The patent changes the cooling rate parameter in two stages: initial fast cooling for high crystallization rate, followed by slow cooling for crystal purification. This dynamic parameter adjustment resolves the contradiction between productivity and 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
Effectively separates and recycles potassium nitrate from the solid waste, reducing waste and manufacturing costs, while allowing for the production of potassium nitrate of various purity grades.
Implementation Method 1
heating the solid waste to a melting temperature to melt the solid waste into a liquid waste
Implementation Method 2
cooling the liquid waste from the melting temperature to a first temperature for facilitating the potassium nitrate contained in the liquid waste to be crystallized as potassium nitrate crystal attached to a sidewall of the first purifying tank
Data Source
AI summary
Provided is a method and an apparatus for purifying potassium nitrate from the solid waste produced by a chemical glass-strengthening process. In the method, the solid waste is melted into a liquid waste at first. Potassium nitrate of various purity grades can be obtained by batch processing the liquid waste through stepwise cooling processes of cooling the liquid waste to a first temperature facilitating the potassium nitrate contained in the liquid waste to be crystallized at a first rate and then cooling the liquid waste to a second temperature close to the freezing point of the potassium nitrate at a second rate that is slower than the first rate. The recovered potassium nitrate from the solid waste can be recycled and reused.