Dual-Pressure Nitric Acid Plant Revamping via Segmented Bleaching
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Solution Overview
Problem
The existing dual-pressure nitric acid production processes require costly and technically demanding revamping to increase primary air, leading to elevated costs and long plant downtime due to the need for new or modified compressors and turbines, with the nitrous gas compressor often becoming a bottleneck.
Innovation Solution
A dual-pressure plant with a two-stage bleaching process, where a high-pressure bleacher strips nitric acid and recycles the nitrogen oxides-loaded air directly to the compressor discharge, allowing for increased capacity without modifying the compressor train, and utilizing a second compressor to provide enriched air at suitable pressures for both bleachers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the amount of primary air to the reactor is increased to increase nitric acid production, then productivity increases, but device complexity and cost increase due to requiring new or modified compressors and turbines
Solution Approach 1:
The bleaching process is divided into two separate stages: a first bleacher operating at absorption pressure and a second bleacher operating at reaction pressure. This segmentation allows each bleacher to be optimized for its specific pressure condition, enabling increased primary air flow without requiring modifications to the compressor train, as the nitrogen oxides-loaded air from the first bleacher is recycled to the compressor discharge rather than requiring increased compressor capacity
2Productivity
If the amount of primary air to the reactor is increased to increase nitric acid production, then productivity increases, but loss of time increases due to long plant downtime required for revamping
Solution Approach 1:
By dividing the bleaching process into two pressure stages and recycling nitrogen oxides-loaded air from the first bleacher to the compressor discharge, the system enables capacity increase without physical modifications to the compressor train or turbines, thereby eliminating the need for plant shutdown and extensive revamping work that would cause time loss
3Productivity
If the amount of primary air to the reactor is increased to increase nitric acid production, then productivity increases, but cost increases due to elevated costs for modification or replacement of existing machines
Solution Approach 1:
The two-stage bleaching process with pressure-based separation and nitrogen oxides recycling creates a configuration where increased primary air flow can be accommodated without capital-intensive modifications to the compressor train or turbines, thereby avoiding the elevated revamping costs associated with replacing or modifying existing machinery
Solution Approach 2:
The system uses the nitrogen oxides-loaded air from the first bleacher as a resource that is recycled back to the compressor discharge, creating a self-sustaining loop that eliminates the need for additional compressor capacity or turbine modifications to handle increased production demands
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 enhances nitric acid purity and production capacity without altering the compressor train, reducing costs and downtime by recycling nitrogen oxides-loaded air at the absorption tower pressure, thus optimizing plant performance.
Implementation Method 1
a first bleacher stripping nitrogen oxides away from the output stream of the absorption tower with a first stripping medium
Implementation Method 2
said second bleacher stripping nitrogen oxides away from said partially stripped nitric acid stream with a second stripping medium
Implementation Method 3
a compressor, which elevates the pressure of the gaseous effluent of the reactor from the reaction pressure to the absorption pressure
Implementation Method 4
a reactor, wherein a stream of ammonia is oxidized to provide a gaseous effluent containing nitrogen oxides
Implementation Method 5
an absorption tower, wherein nitrogen oxides contained in said gaseous effluent react with water to provide an output product stream containing nitric acid
Data Source
AI summary
A dual-pressure plant for the synthesis of nitric acid comprising: a reactor (4) providing a gaseous effluent (15) containing nitrogen oxides; an absorption tower (6) nitrogen oxides react with water providing raw nitric acid and, said absorption tower operating at a pressure greater than the pressure of the reactor; a compressor (5) elevating the pressure of the reactor effluent (15) to the absorption pressure; said plant also comprising a first bleacher (37) and a second bleacher (7), said first bleacher (37) stripping with air (39) nitrogen oxides from the output stream (27) of the absorption tower (6) providing a partially stripped nitric acid stream (40) and a nitrogen oxides-loaded air stream (41), the former being fed to the second bleacher (7) and the latter being recycled to the delivery-side of said compressor (5).