Sulfuric Acid Recirculation Loop for 98% Concentration
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Solution Overview
Problem
Existing sulfuric acid concentration technologies, such as the Integrated Sulfuric Acid Concentrator (ISAC) and direct fired units, struggle to achieve the desired concentration of 98 wt % sulfuric acid due to limitations in the flow of hot dried air and the presence of azeotropes, leading to suboptimal product concentration and increased energy consumption.
Innovation Solution
The implementation of a sulfuric acid recirculation loop utilizing an air lift pump, which recirculates concentrated sulfuric acid through a concentrator column with a carrier fluid, allowing for increased concentration by stripping water from the acid, and includes features like a sulfuric acid heater and parallel air lift pumps to enhance efficiency and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ISAC or direct fired concentration units are used, then sulfuric acid concentration can be increased, but the maximum achievable concentration is limited to around 96.3 wt % due to azeotrope formation and limited hot dried air flow
Solution Approach 1:
The concentration process is divided into multiple sequential stages: initial concentration in ISAC to ~96.3 wt %, followed by further concentration in a second concentrator column to achieve 98.0 wt %. This segmentation allows each stage to operate within its optimal range and overcome the azeotrope limitation of the first stage.
Solution Approach 2:
Hot dried air serves as an intermediary medium that transfers thermal energy and mass transfer capacity between the sulfuric acid streams. The recirculated hot dried air from the second concentrator column acts as a mediator to enable further concentration beyond the azeotrope point without requiring additional external heating.
2Manufacturing precision
If multiple distillation steps are used to achieve >98.0 wt % sulfuric acid, then concentration can be increased, but energy consumption increases and at least the last step requires vacuum operation
Solution Approach 1:
The system maintains continuous circulation of hot dried air and sulfuric acid through the concentrator columns, eliminating the need for intermittent vacuum operations. The recirculation loop ensures continuous heat and mass transfer, achieving sustained concentration at atmospheric pressure with lower energy input.
Solution Approach 2:
The process changes the operating parameters by using recirculated hot dried air at controlled temperatures and flow rates to shift the equilibrium conditions, enabling concentration beyond the traditional azeotrope point without requiring vacuum conditions or excessive energy input.
3Manufacturing precision
If ISAC is used to concentrate sulfuric acid, then concentration can be increased, but the allowable flow of hot dried air is limited by the wetting requirement, restricting further concentration
Solution Approach 1:
The concentration capacity is segmented across two concentrator columns operating in series. The first column (ISAC) handles the initial concentration up to ~96.3 wt %, while the second column handles the final concentration to 98.0 wt %. This segmentation allows each column to operate at optimal air flow rates without exceeding wetting limits.
Solution Approach 2:
The system adds a temporal dimension through recirculation, where hot dried air and sulfuric acid are circulated multiple times through the concentrator columns. This allows progressive concentration over multiple passes, effectively increasing the overall concentration capacity without requiring higher instantaneous air flow rates that would exceed wetting limits.
4Ease of operation
If centrifugal pumps are used in the recirculation loop, then sulfuric acid can be recirculated, but equipment wear and maintenance needs increase
Solution Approach 1:
The mechanical centrifugal pump is replaced with a gas lift recirculation system that uses recirculated hot dried air to provide the lifting force. This substitution eliminates mechanical contact between the pump and corrosive sulfuric acid, dramatically reducing equipment wear and maintenance requirements while maintaining recirculation capability.
Solution Approach 2:
Hot dried air serves as an intermediary medium that provides the recirculation force without direct mechanical contact with sulfuric acid. The gas lift system uses the density difference between the hot dried air and sulfuric acid to create circulation, eliminating the need for mechanical pumps that would require frequent maintenance in the corrosive environment.
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 enables the production of 98.0 wt % sulfuric acid independently of the initial concentration from the sulfuric acid condenser, improving operational flexibility and reducing energy costs while minimizing equipment wear and maintenance needs.
Implementation Method 1
an air lift pump having a liquid inlet fed with hot concentrated sulfuric acid from the outlet of a sulfuric acid reservoir downstream the concentrator column, a gas inlet fed with a carrier fluid having a lower density than the hot concentrated sulfuric acid
Implementation Method 2
The sulfuric acid is optionally heated during its passage through the sulfuric acid recirculation loop
Implementation Method 3
the hot already concentrated sulfuric acid from the sulfuric acid condenser is contacted with hot dried air in a concentrator column, flowing in counter-current to the sulfuric acid, thereby forcing water and a little sulfuric acid to evaporate from the sulfuric acid
Implementation Method 4
contacted with hot dried air in a concentrator column, flowing in counter-current to the sulfuric acid
Implementation Method 5
sulfuric acid condenses from the gas phase by direct or indirect cooling of the process gas containing sulfuric acid and water vapor
Data Source
AI summary
A sulfuric acid recirculation loop and a standalone sulfuric acid concentrator including: a concentrator column, an air lift pump having a liquid inlet fed with concentrated sulfuric acid from the outlet of a sulfuric acid reservoir downstream the concentrator column, a gas inlet fed with a carrier fluid having a lower density than the concentrated sulfuric acid, and an outlet, wherein the sulfuric acid reservoir is located below the concentrator column and above the carrier fluid inlet of the air lift pump, a downcomer pipe leading down from the sulfuric acid reservoir to the liquid inlet of the air lift pump, and a riser pipe leading up from the carrier fluid inlet on the air lift pump to an inlet pipe for the concentrator column, the inlet pipe being configured for allowing a liquid flow from the inlet to the outlet.