Boiler Segmentation for SO2 Oxidation Thermal Management
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Solution Overview
Problem
The thermal management of sulfuric acid production plants is inefficient due to limited flexibility and high costs, particularly when SO2 concentrations are low, requiring additional fuel for heating and posing challenges in maintaining temperatures above 370-400°C for oxidation reactions while avoiding corrosive sulfuric acid condensation.
Innovation Solution
Implementing a process that uses combined heat exchange, including a boiler producing steam, to ensure the cooled oxidized process gas remains non-condensing, allowing for increased temperature approaches in heat exchangers, reducing the heat exchange area and material corrosion concerns, and enabling auto-thermal operation with lower SO2 concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the feed gas is heated to 400°C using reaction heat from the SO2 converter, then the oxidation reaction can proceed at a reasonable rate, but the thermal management flexibility is limited and additional fuel is required when SO2 concentration is low
Solution Approach 1:
The thermal management system is segmented into multiple independent heating zones: a first heating zone using a boiler before the converter, and a second heating zone using reaction heat from the converter itself. This segmentation allows each zone to operate independently, enabling flexible thermal management when SO2 concentration varies, while ensuring the oxidation reaction can always proceed at the required temperature
Solution Approach 2:
The boiler serving as the first heating zone is designed to provide heating functionality that complements the converter's reaction heat. This multi-functional thermal management system can handle both high and low SO2 concentration scenarios, making the overall system adaptable to varying feed gas compositions while maintaining productive oxidation rates
2Productivity
If the oxidized process gas is cooled to shift product equilibrium towards SO3, then the conversion efficiency improves, but sulfuric acid condensation occurs causing corrosion
Solution Approach 1:
Different sections of the cooling system are designed with different material qualities: the first cooling zone (where temperature is still high) uses materials resistant to hot sulfuric acid, while the second cooling zone (where temperature is lower) uses materials resistant to condensed sulfuric acid. This local differentiation of material quality allows efficient cooling to shift equilibrium while managing corrosion risks in each specific zone
Solution Approach 2:
The cooling process is divided into two stages with different temperature parameters: first cooling from reaction temperature to an intermediate temperature, then second cooling to near ambient temperature. By changing the temperature parameter in stages and using appropriate materials for each stage, the system achieves high conversion efficiency while preventing corrosive condensation through proper material selection in each temperature zone
3Productivity
If support-firing is used to heat the feed gas when SO2 concentration is low, then the oxidation reaction can proceed, but the energy cost increases
Solution Approach 1:
A boiler is installed as a first heating zone that pre-heats the feed gas before it enters the converter. This preliminary heating action reduces the temperature gap that needs to be bridged by reaction heat or support-firing, thereby reducing the amount of additional fuel needed when SO2 concentration is low while maintaining productive oxidation rates
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 significantly reduces heat exchange area and costs, stabilizes the temperature at the sulfuric acid condenser inlet, and allows for efficient thermal management with non-corrosive conditions, enabling more optimal oxidation reactions and sulfuric acid production.
Implementation Method 1
heating water in a boiler to a temperature corresponding to a pressure of the steam to be produced in the boiler, thereby producing the steam
Implementation Method 2
heat exchange with the oxidized process gas or a further oxidized process gas
Implementation Method 3
contacting the heated process gas with a first zone of material catalytically active in oxidation of SO2 to SO3
Implementation Method 4
material catalytically active in oxidation of SO2 to SO3
Implementation Method 5
the hydration reaction for SO3 is exothermal
Data Source
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AI summary
The present invention relates to a process plant for the oxidation of SO2 to SO3 in a process gas, said process plant comprising a heat exchanger configured for heating the process gas by heat exchange with an oxidized process gas and/or a further oxidized process gas by providing thermal contact between said process gas and said oxidized process gas and/or said further oxidized process gas, a first zone of material catalytically active in oxidation of SO2 to SO3, and a boiler configured for containing steam being heated by the oxidized process gas and/or the further oxidized process after said oxidized process gas has been cooled in the heat exchanger characterized in the cooled oxidized process gas in the boiler being non-condensing with the benefit of providing the possibility for a smaller heat exchanger which may be made with only moderate corrosion resistant materials, compared to a process plant according to the prior art, as well as a related process.