Cyanide Crystallization Process With Controlled Hydroxide Addition
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Solution Overview
Problem
Existing methods for producing alkali metal cyanide solid products face challenges in achieving a stable product with a high alkali metal hydroxide content while minimizing the risk of hydrogen cyanide release and avoiding issues like clumping, energy-intensive drying, and equipment blockages.
Innovation Solution
A system is designed with an alkali mixing device downstream of the crystallization vessel and a solid-liquid separation device, allowing controlled addition of aqueous alkali metal hydroxide to the suspension, which is then processed through a reaction loop and crystallization vessel to achieve a higher alkali metal hydroxide fraction in the final product, while maintaining process stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alkali metal hydroxide is added to prevent hydrogen cyanide release, then safety is improved, but the product tends to clump together due to moisture absorption
Solution Approach 1:
The patent optimizes the alkali metal hydroxide content parameter to a specific range (0.5-3% by weight) that balances safety requirements with product stability. This parameter optimization prevents both insufficient safety protection and excessive moisture absorption that causes clumping.
2Reliability
If alkali metal hydroxide concentration in mother liquor is increased to ensure safety, then hydrogen cyanide release is prevented, but serious rumbling and knocking occurs in the system
Solution Approach 1:
The patent establishes an optimal concentration range for alkali metal hydroxide in the mother liquor (0.5-3% by weight) that prevents hydrogen cyanide release while avoiding the rumbling and knocking phenomena that occur at higher concentrations. This parameter control resolves the contradiction between safety and system stability.
3Reliability
If alkali metal hydroxide is added to neutralize acids, then decomposition of alkali metal cyanide is prevented, but energy consumption increases due to drying requirements
Solution Approach 1:
The patent optimizes the alkali metal hydroxide content to a minimal effective range (0.5-3% by weight) that provides sufficient acid neutralization capacity to prevent cyanide decomposition while minimizing the energy required for subsequent drying operations. This avoids excessive energy consumption associated with higher hydroxide concentrations.
4Reliability
If alkali metal hydroxide content is increased to ensure safety, then acid neutralization capacity is improved, but the product becomes excessively hygroscopic
Solution Approach 1:
The patent determines an optimal alkali metal hydroxide content range (0.5-3% by weight) that provides adequate acid neutralization capacity for safety while limiting hygroscopic properties to prevent excessive moisture absorption. This parameter optimization resolves the contradiction between safety functionality and reduced hygroscopicity.
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 system produces a stable alkali metal cyanide solid product with a higher alkali metal hydroxide content, reducing the risk of hydrogen cyanide release and minimizing energy consumption and equipment issues, thereby enhancing safety and efficiency.
Implementation Method 1
water from the liquid phase of the first suspension can be evaporated in the crystallization vessel. This promotes the formation and growth of alkali metal cyanide crystals.
Implementation Method 2
If the vapors contain hydrogen cyanide, further aqueous sodium cyanide is formed upon contact with the sodium hydroxide solution.
Implementation Method 3
a reactant gas, essentially pure gaseous hydrogen cyanide, is added to the first suspension. This creates a reaction mixture with a third suspension, which, compared to the first suspension, contains a higher proportion of aqueous sodium cyanide and a lower proportion of aqueous sodium hydroxide.
Data Source
Figure 1
AI summary
The present invention relates to a plant and to a process for producing a solid-state alkali metal cyanide product. In order to obtain a solid-state alkali metal cyanide product that has a good proportion by weight of alkali metal hydroxide, and in order to ensure that it remains as calm as possible in the plant during operation, it is proposed that the proportion by weight of alkali metal hydroxide in a suspension withdrawn from the crystallization vessel and sent to a solid-liquid separation device be increased before it enters the solid-liquid separation device.