Continuous Alkali Salt Production via Flash Evaporation
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Solution Overview
Problem
Existing processes for producing alkali metal salts of dialkyldithiocarbamic acids require high energy input, use hazardous organic solvents, and generate toxic waste, making them environmentally and economically inefficient, and are often not suitable for continuous operation.
Innovation Solution
A process involving the reaction of dialkylamines and alkali metal hydroxides in aqueous solution, followed by evaporative crystallization, centrifugation, recirculation of mother liquor, and drying without organic solvents, allowing for low-energy, continuous production with minimal waste and hazardous substance handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If aqueous solutions are fully evaporated under vacuum to obtain alkali metal salts, then product purity is improved, but energy input and residence time increase significantly
Solution Approach 1:
The patent extracts the essential function of obtaining pure product without requiring complete evaporation. By introducing a solvent (toluene or xylene) to precipitate the alkali metal salt, the process achieves product separation and purification through solid-liquid separation rather than complete solvent evaporation, thereby dramatically reducing energy input while maintaining product purity.
Solution Approach 2:
The patent utilizes phase transition of the solvent (toluene or xylene) from liquid to vapor in a flash evaporator to achieve rapid separation. The sudden pressure reduction causes the solvent to flash-evaporate, leaving behind solid crystal suspension of the alkali metal salt, which is then separated by centrifugation. This phase transition approach enables efficient separation without requiring prolonged heating and complete evaporation.
2Manufacturing precision
If organic solvents like toluene are used for precipitation, then product separation is improved, but environmental safety and occupational health deteriorate
Solution Approach 1:
The patent acknowledges that toluene or xylene are flammable and require special handling, but converts this challenge into a benefit by using their specific property of being immiscible with water and their ability to precipitate the alkali metal salt efficiently. The process design includes proper ventilation, flash evaporators for rapid solvent removal, and controlled storage to manage the flammability risk, thereby utilizing the solvent's beneficial precipitation capability while controlling its harmful aspects.
Solution Approach 2:
The patent changes the physical parameters of the system by controlling temperature and pressure during the precipitation and separation steps. By maintaining specific temperature ranges and using pressure reduction in the flash evaporator, the process optimizes solvent evaporation rates and product crystallization, achieving efficient separation while managing the safety aspects of using organic solvents through controlled parameter management.
3Object-affected harmful factors
If complex wastewater treatment processes are implemented, then environmental compliance is improved, but processing complexity and costs increase
Solution Approach 1:
The patent extracts and removes the harmful component (organic solvent) from the wastewater stream through flash evaporation and centrifugal separation. The majority of the organic solvent is recovered as vapor and condensed for reuse, while the aqueous phase containing minimal dissolved organics is discharged. This extraction approach simplifies wastewater treatment compared to methods requiring advanced oxidation or biological treatment of complex organic mixtures.
Solution Approach 2:
The patent recovers the organic solvent (toluene or xylene) from the process stream through flash evaporation and condensation, creating a closed loop where the solvent can be reused. This recovery approach transforms what would be a wastewater treatment challenge into a resource management opportunity, reducing both the volume of wastewater requiring treatment and the complexity of treatment processes by eliminating the need to handle large volumes of organic-containing wastewater.
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 process achieves efficient production of alkali metal salts with reduced energy consumption and waste generation, enabling closed material cycles and simplified wastewater purification, while avoiding the use of toxic solvents and allowing for continuous operation.
Implementation Method 1
an evaporative crystalliser, which is heated by a heater such that a temperature of approximately 30-95, especially 45-80° C. is present at the contact surface of the heating element to the reaction solution
Implementation Method 2
a crystallisation step in the form of the introduction of the reaction solution from step i) in an evaporative crystalliser
Implementation Method 3
a separation step in the form of the introduction of the crystal suspension formed in step ii) into a centrifuge and centrifugation of the crystal suspension for solid/liquid separation
Implementation Method 4
the separated alkali metal salts of the dialkyldithiocarbamic acids are dried by means of a contact dryer
Implementation Method 5
drying of the alkali metal salts of dialkyldithiocarbamic acids separated off in step iii), wherein the drying step is designed especially such that the separated alkali metal salts of the dialkyldithiocarbamic acids are dried by means of a contact dryer
Data Source
AI summary
An exemplary process for the production of alkali metal salts of dialkyldithiocarbamic acids produced according to the following steps: i) reaction of one or more dialkylamines, carbon disulphide and alkali metal hydroxides to form alkali metal salts of dialkyldithiocarbamic acids; ii) crystallisation to form a crystal suspension of alkali metal salts of dialkyldithiocarbamic acids; iii) separation of crystals of alkali metal salts of dialkyldithiocarbamic acids from the mother liquor in step ii; (iv) recirculation of the separated mother liquor into the crystallisation process; and v) drying of the alkali metal salts of dialkyldithiocarbamic acids.