Two-Stage Cooling Device for Nitric Acid Condensation
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Solution Overview
Problem
The existing methods for producing nitric acid through the oxidation of ammonia face challenges in controlling the condensation of hot acidic gas mixtures, leading to corrosive effects on stainless steel materials due to the heating of nitric acid condensate, which can cause corrosion and is costly to mitigate with resistant materials like zirconium.
Innovation Solution
A method involving a two-stage cooling process using a tube bundle heat exchanger with vertically arranged tubes in the first cooling device and a cylindrical second cooling device with a transverse axis, where the hot gas mixture is cooled to below its dew point in the first stage, preventing significant condensate heating and allowing unhindered flow, and further cooled in the second stage to prevent corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional cooling devices are used to cool hot acidic gas mixtures, then cooling and condensation occur, but the nitric acid condensate heats up to highly corrosive temperatures causing severe corrosion on stainless steel materials
Solution Approach 1:
The cooling process is divided into two separate cooling devices: a first cooling device that cools the gas mixture to below the dew point, and a second cooling device that further cools the partially condensed mixture. This segmentation prevents the condensate from being heated to highly corrosive temperatures by ensuring it condenses in a controlled manner without subsequent heating exposure.
Solution Approach 2:
The first cooling device performs preliminary cooling of the hot gas mixture to below its dew point before the condensate can be heated to corrosive temperatures. This preliminary action of cooling and condensing the acid mist in a controlled first stage prevents the harmful heating effect that would otherwise occur in conventional single-stage cooling systems.
2Object-affected harmful factors
If resistant materials like zirconium are used to prevent corrosion, then corrosion resistance is improved, but material costs increase significantly
Solution Approach 1:
The patent employs conventional stainless steel materials (a cheaper alternative to zirconium) in the cooling devices by controlling the cooling process to prevent corrosive heating. The first cooling device uses stainless steel construction with controlled cooling to below dew point, avoiding the need for expensive corrosion-resistant alloys like zirconium while maintaining adequate material life through process control.
3Productivity
If the gas mixture is cooled rapidly to condense acid, then condensation efficiency is improved, but the condensate may collect on horizontal surfaces and be heated to corrosive temperatures
Solution Approach 1:
The second cooling device is oriented with its axis extending transversely to the first cooling device, creating a different spatial dimension for the cooling process. This transverse arrangement allows the partially condensed mixture to be further cooled in a different orientation, preventing condensate collection on horizontal surfaces and eliminating the heating effect that would occur in conventional horizontal cooling arrangements.
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 effectively prevents corrosion by ensuring the nitric acid condensate does not heat up significantly, reducing the risk of corrosive attacks on equipment and allowing for efficient condensation of the gas mixture into aqueous solutions, thereby minimizing material degradation and operational costs.
Implementation Method 1
the hot gas mixture is cooled and condensed by means of a coolant
Implementation Method 2
the hot gas mixture is cooled and condensed by means of a coolant
Implementation Method 3
the hot gas mixture is cooled and condensed by means of a coolant
Data Source
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AI summary
The present invention relates to an arrangement for the controlled condensation of a hot acidic gas mixture, in particular gases containing nitrogen oxides, during the production of nitric acid from ammonia by oxidation with air or an oxidizing gas, comprising at least one cooling device in which the hot gas mixture is cooled and condensed by means of a coolant, wherein the at least one cooling device (10) is designed as a shell-and-tube heat exchanger with a plurality of tubes (8) arranged substantially parallel to one another. Preferably, this cooling device (10) is a first cooling device, and a second cooling device is provided downstream of the first cooling device in the direction of flow with respect to the hot gas mixture, and which is fluidically connected to the first cooling device (10).An important advantage arises from the fact that two cooling devices can be used and the energy transfer between the pipes (8), through which the hot gas mixture flows, and the cooling medium can be adjusted so that the dew point of the hot gas mixture is safely crossed in the first cooling device (10), i.e., in the first heat exchanger. This prevents excessive heating by the hot gas mixture at points in the arrangement where condensate can collect, thus preventing corrosion.