Adiabatic Mixed-Acid Workup With Sulfuric Acid Reconcentration
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Solution Overview
Problem
Existing processes for processing nitric acid-containing waste streams from aromatic nitration are inefficient, requiring additional energy for nitric acid reconcentration and separate treatment of different waste streams, and face challenges with incomplete conversion due to substoichiometric aromatic compound addition.
Innovation Solution
A device and process that combines all waste streams with reconcentrated sulfuric acid and adds an aromatic compound in stoichiometric excess under adiabatic conditions, allowing complete nitric acid conversion without additional energy input, using a modular tubular reactor and separator to separate organic and sulfuric acid phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If substoichiometric amount of aromatic compound is added to convert nitric acid, then nitric acid conversion is incomplete, but adding stoichiometric excess of aromatic compound requires additional energy for reconcentration of sulfuric acid
Solution Approach 1:
The patent combines multiple waste streams (nitration waste acid, acidic wash water, and dilute nitric acid from exhaust gas treatment) into a single processing system. By merging these streams and adding aromatic compound in stoichiometric excess, the system achieves complete nitric acid conversion while the reaction heat from adiabatic conditions provides the energy for sulfuric acid reconcentration, eliminating the need for external energy input.
Solution Approach 2:
The patent converts the exothermic nitration reaction heat, which would otherwise be waste energy requiring cooling, into a useful resource for driving the sulfuric acid reconcentration process. The adiabatic operation allows the reaction heat to increase the temperature of the sulfuric acid phase, providing the thermal energy needed for reconcentration without additional energy input.
2Manufacturing precision
If separate treatment of different waste streams is performed, then treatment completeness is improved, but device complexity and investment costs increase
Solution Approach 1:
The patent integrates three separate waste streams (nitration waste acid, acidic wash water, and dilute nitric acid) into a single processing system. All streams are combined in a mixing unit and treated together in one adiabatic reactor, eliminating the need for separate treatment trains and reducing overall system complexity while maintaining treatment effectiveness.
Solution Approach 2:
The adiabatic reactor serves multiple functions simultaneously: it converts nitric acid to nitroaromatic compounds, heats the sulfuric acid phase for reconcentration, and processes all combined waste streams. This multi-functionality reduces the number of dedicated units needed for each function, simplifying the overall device configuration.
3Use of energy by moving object
If adiabatic operation is used to reduce energy input, then energy consumption is reduced, but temperature control becomes more difficult
Solution Approach 1:
The system uses its own reaction heat to drive the sulfuric acid reconcentration process. The exothermic nitration reaction automatically provides the thermal energy needed for heating and reconcentrating the sulfuric acid phase, making the system self-sufficient and eliminating the need for external energy input or complex temperature control systems.
Solution Approach 2:
The reactor is designed with static mixers that segment the liquid phases and improve mixing efficiency. This segmentation ensures uniform distribution of reactants and heat, facilitating better temperature control and preventing hot spots despite the adiabatic operation.
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
Achieves complete nitric acid conversion with reduced energy consumption and lower investment costs by integrating all waste streams and utilizing reaction energy for sulfuric acid reconcentration, eliminating the need for separate treatment and additional energy input.
Implementation Method 1
nitric acid contained therein is converted by reaction with an aromatic under adiabatic conditions
Implementation Method 2
a separator, in which the mixture emerging from the tubular reactor is separated into an organic phase and an acid phase
Implementation Method 3
a flash evaporator, in which the acid phase is fed and water is removed
Implementation Method 4
a concentration unit with an indirectly heated heat exchanger and an associated evaporator with associated vapor condensation
Data Source
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Figure 2
AI summary
In a process for the work-up of mixed acid and wastewater from the nitration of aromatics, in which the nitric acid contained is reacted with an aromatic under adiabatic conditions, a. at least one waste stream component is selected from waste acid (mixed acid) obtained during nitration, acidic wash water from the work-up of crude nitroaromatics, and dilute nitric acid obtained during exhaust gas treatment in the course of nitration; b. the at least one waste stream component is mixed with reconcentrated sulfuric acid; c. an aromatic is added to the mixture in a stoichiometric excess relative to the nitric acid; d. the resulting reaction mixture is reacted in an adiabatic reactor; e. the resulting organic phase is separated from the sulfuric acid phase in a separator; f. the sulfuric acid phase is concentrated under vacuum; and g.at least a partial stream of the reconcentrated sulfuric acid from step g) is used in step b).