Nitric Acid Absorption Tower Riser Oxygen Injection
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Solution Overview
Problem
Current nitric acid production processes, such as the Ostwald process, face inefficiencies due to high nitrous gas content in exhaust gases, particularly at low oxygen partial pressures, leading to suboptimal capacity and increased costs for high-pressure system design and operation.
Innovation Solution
Introducing oxygen at a higher pressure into the upper region of the absorption tower, where the nitric acid solution is compressed, allowing nitrogen oxides to react with oxygen and water to form additional nitric acid, thereby increasing production efficiency and reducing waste gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If additional oxygen is introduced into the absorption tower to increase oxygen partial pressure, then nitric acid production efficiency is improved, but device complexity and operational costs increase
Solution Approach 1:
The invention introduces oxygen into the riser line before the nitric acid solution enters the absorption tower, allowing oxidation reactions to begin in advance. This preliminary oxygen introduction ensures that when the solution reaches the absorption tower, the oxidation of nitrogen oxides is already underway, improving overall process efficiency without requiring complex oxygen injection systems within the tower itself.
Solution Approach 2:
The riser line itself serves dual purposes: as a transport conduit for the nitric acid solution and as a reaction zone where oxygen introduction initiates oxidation. This eliminates the need for separate reaction chambers or complex internal tower modifications, allowing the existing infrastructure to serve multiple functions and reducing overall system complexity.
2Productivity
If the absorption tower operates at higher pressure to reduce nitrous gas content, then nitric acid production is improved, but compression costs and system design costs increase significantly
Solution Approach 1:
The invention changes the oxidation conditions by introducing oxygen at controlled pressures in the riser line, allowing efficient nitric acid production at lower operating pressures. By optimizing the oxygen partial pressure and introduction timing, the system achieves high conversion efficiency without requiring the high compression pressures that would otherwise be needed, thereby reducing energy consumption and compression costs.
3Ease of manufacture
If oxygen is introduced at lower pressure, then system design and operation are simpler, but nitric acid production efficiency decreases due to low oxygen partial pressure
Solution Approach 1:
By introducing oxygen preliminarily in the riser line before the solution enters the absorption tower, the system achieves efficient oxidation at lower pressures. This preliminary oxygen introduction ensures that oxidation reactions begin under favorable conditions, maintaining high productivity while allowing the absorption tower to operate at simpler, lower pressures.
Solution Approach 2:
The invention optimizes the oxygen introduction parameters in the riser line, controlling pressure and flow rate to achieve maximum oxidation efficiency at low operating pressures. This parameter optimization allows the system to maintain high nitric acid production efficiency while operating under simpler pressure conditions, reducing the need for complex high-pressure equipment.
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 method enhances nitric acid production by increasing the oxygen partial pressure, reducing nitrous gas emissions, and lowering operational costs through improved reaction kinetics and reduced need for additional oxygen, particularly beneficial for low- and medium-pressure systems.
Implementation Method 1
allowing nitrogen oxides to react with oxygen and water to form additional nitric acid
Implementation Method 2
nitrogen oxides to react with oxygen and water to form additional nitric acid
Implementation Method 3
where the nitric acid solution is compressed, allowing nitrogen oxides to react with oxygen
Implementation Method 4
Introducing oxygen at a higher pressure into the upper region of the absorption tower
Data Source
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AI summary
In a process for preparing nitric acid, nitrogen oxides are first generated in an ammonia combustion plant (2), and these are then supplied to at least one absorption tower (4, 5). In the absorption tower (4, 5), the nitrogen oxides are contacted in the water and oxygen, with at least partial reaction of the nitrogen-containing gas mixture with the water and the oxygen to form an aqueous nitric acid-containing solution which collects at the base of the absorption tower (4, 5) and is subsequently compressed and introduced via a riser line (12, 14, 21) back into the absorption tower (4, 5). In order to minimize the concentration of nitrogen oxides in the offgas from such a plant, it is proposed in accordance with the invention that oxygen be introduced in liquid form or gaseous form into a region of the riser line (12, 14, 21) that is lower in a geodetic sense. This promotes the dissolution of the oxygen and the reaction of the oxygen with likewise dissolved nitrogen oxides to give nitric acid.