Two-Pressure Distillation of Aqueous Amine Solutions
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Solution Overview
Problem
Current processes for distillative working-up of aqueous amine solutions from catalytic hydrogenation of nitroaromatic compounds are energy-intensive, with high energy consumption and contamination of distilled water with steam-volatile organic byproducts.
Innovation Solution
The process involves using at least two distillation columns operated at different pressures, where vapors from the higher-pressure column are condensed and used to heat the lower-pressure column, and steam-volatile byproducts are separated and recycled, significantly reducing energy consumption and achieving purified water and amine separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single distillation column is used to separate aqueous amine solutions, then the separation process is simple, but high energy consumption occurs (1.2 to 2 kg of heating steam per kg of water separated)
Solution Approach 1:
The single distillation column is divided into two distillation columns operating at different pressures. The first column operates at lower pressure (0.1-10 bar) and the second at higher pressure (2-20 bar), allowing energy optimization through pressure differential while maintaining separation effectiveness
Solution Approach 2:
Vapors from the higher-pressure column are condensed and the condensation heat is utilized to heat the lower-pressure column. This heat integration reduces external energy input by recovering and reusing thermal energy within the system
2Quantity of substance
If conventional distillation is used to separate water from amine solutions, then water is obtained, but the distilled water is highly contaminated with steam-volatile organic byproducts
Solution Approach 1:
The system uses different operating pressures in the two distillation columns to selectively separate components. The lower-pressure column preferentially removes steam-volatile organic byproducts, while the higher-pressure column produces high-purity water, achieving both quantity and quality requirements
Solution Approach 2:
The separation process adds a pressure dimension by operating two columns at different pressures. This creates additional separation capability where the lower-pressure column handles volatile organics and the higher-pressure column handles water purification, achieving comprehensive separation that a single column cannot accomplish
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 approach reduces energy consumption by 30 to 50% compared to one-stage evaporation plants, effectively separating amine solutions into amine, byproducts, and pure water with minimal energy expenditure.
Implementation Method 1
the vapors leaving the distillation column operating at higher pressures are at least partially condensed and the heat that is thereby released is used to heat the bottom of the distillation column operating at the lower pressures
Implementation Method 2
the heat that is thereby released is used to heat the bottom of the distillation column operating at the lower pressures
Implementation Method 3
the distillation is carried out in at least two distillation columns connected in series and operated at different pressures
Data Source
AI summary
The invention relates to an energy efficient process for the distillative working-up of aqueous amine solutions that occur in the catalytic hydrogenation of nitroaromatic compounds. In this process, the amine is freed from water and also the water is obtained free from amine and low-boiling compounds and the concentrated low-boiling compounds are obtained.