Nitric Acid Plant Air Compression Layout for Capacity Bottlenecks
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Solution Overview
Problem
Conventional dual-pressure nitric acid production processes face limitations in capacity due to bottlenecks in the compressor system, leading to high costs and risks in revamps, and single-pressure processes result in the production of dilute nitric acid.
Innovation Solution
A dual-pressure process where secondary air for bleaching is provided by a separate compressor independent of the primary air compressor, allowing bleaching to occur at a lower pressure, with the laden bleach air being compressed to a higher pressure by a further compressor, thus avoiding stress on the NOx compressor and enabling full capacity utilization of the primary air compressor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single air compressor is used for both primary air and secondary air supply in conventional dual-pressure plants, then the compressor assembly is simplified, but the capacity of the plant is limited due to bottleneck at the compressor output
Solution Approach 1:
The patent divides the air compression function into separate compressors: a first air compressor for primary air supply to the oxidation reactor, and a second air compressor for secondary air supply to the absorption tower. This segmentation removes the bottleneck at the single compressor output and enables independent optimization of each air stream, thereby increasing overall plant capacity without requiring complex modifications to an integrated compressor assembly.
2Productivity
If an additional secondary air compressor is added to increase plant capacity, then the capacity limitation is overcome, but the costs and complexity of the compressor assembly increase significantly
Solution Approach 1:
Instead of adding complexity to a single integrated compressor assembly, the patent segments the air supply system into separate compressors for primary and secondary air. This allows capacity expansion through the addition of a second compressor rather than upgrading a complex multi-functional assembly, reducing both capital costs and operational complexity.
Solution Approach 2:
The second air compressor serves multiple functions: it supplies secondary air to the absorption tower and also provides bleed air for the bleaching tower. This multi-functionality maximizes the utility of the additional compressor while minimizing overall system complexity and cost.
3Ease of operation
If the air stream is divided downstream of the air compressor in conventional plants, then the primary air and secondary air are supplied, but the output of the compressor becomes a bottleneck that limits plant capacity
Solution Approach 1:
The patent applies segmentation by providing separate air compressors for primary and secondary air streams rather than dividing a single compressed air stream. This eliminates the bottleneck at the compressor output while maintaining ease of operation, as each compressor can be independently controlled and optimized for its specific function.
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 allows for increased plant capacity without significant capital costs or alterations to the main machine, maintaining existing secondary air systems and avoiding stress on the NOx compressor, while achieving effective nitric acid production.
Implementation Method 1
the oxidation of ammonia to nitrogen oxides (NOx) is carried out in a reactor at a first pressure
Implementation Method 2
the oxidation of ammonia to nitrogen oxides (NOx) is carried out in a reactor at a first pressure
Implementation Method 3
said oxides subsequently being reacted with water to afford crude nitric acid in an absorption tower
Implementation Method 4
the secondary air is brought to the operating pressure of the bleaching operation via at least one separate compressor independent of the compressor which brings the primary air to the first pressure
Implementation Method 5
the laden bleach air being compressed to a higher pressure by a further compressor, thus avoiding stress on the NOx compressor
Data Source
AI summary
A process for producing nitric acid by the Ostwald process involves reacting ammonia with atmospheric oxygen as primary air to afford a NOx-containing gas stream in an ammonia oxidation reactor at a first pressure and absorbing the NOx-containing gas stream in water in an absorption apparatus at a higher, second pressure. Nitric acid is bleached with bleach air as secondary air at approximately the first pressure. The secondary air is brought to an operating pressure of the bleaching operation via a separate secondary air compressor or compressor stage. The separate secondary air compressor is independent of the compressor that brings the primary air to the first pressure. Compression to the second higher pressure at which the absorption of the NOx gases is performed in the absorption apparatus is provided only downstream of the bleaching operation.