Ammonia Synthesis Loop Modernization via Isothermal Converter
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Solution Overview
Problem
The existing ammonia plant synthesis loop design with two converters in series faces a risk of failure due to severe stress on the second converter's pressure vessel from high temperature and corrosive conditions, leading to potential corrosion and brittleness, especially in the absence of effective shell cooling.
Innovation Solution
The method involves replacing the cartridge of the first converter with a new one containing an isothermal catalyst bed and increasing the purge rate of inert gases, allowing the first converter to maintain conversion rates similar to the original two-reactor system while bypassing or removing the second converter to alleviate stress on the pressure vessel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the second converter is used to boost capacity and decrease energy consumption, then productivity is improved, but the pressure vessel is exposed to severe corrosion and stress due to high temperature and corrosive environment
Solution Approach 1:
The harmful second converter is extracted and removed from the synthesis loop, eliminating the source of high-temperature corrosion and stress on pressure vessels while maintaining acceptable ammonia production capacity through optimization of the first converter and increased purge rate
Solution Approach 2:
The purge rate is increased to remove more inerts from the loop, which changes the composition and flow parameters to compensate for the removal of the second converter, maintaining conversion rates while reducing the need for high-temperature operation
2Productivity
If the second converter operates at high temperature to maintain conversion rates, then productivity is improved, but hydrogen and ammonia corrosion causes brittleness of the steel vessel
Solution Approach 1:
The increased purge rate, which removes inerts that would otherwise accumulate and hinder conversion, is used as a compensatory mechanism to maintain productivity without requiring the harmful high-temperature operation of the second converter, thus protecting vessel strength
3Ease of manufacture
If the simple design of the second converter is used to reduce cost, then ease of manufacture is improved, but the shell cannot be effectively cooled leading to constant high temperature operation
Solution Approach 1:
The problematic second converter with its inadequate cooling design is extracted from the system, eliminating the temperature control issue while the first converter's shell cooling system continues to effectively cool the pressure vessel
4Reliability
If the first converter is revamped with an isothermal catalyst bed and increased purge rate, then reliability is improved by eliminating the second converter, but device complexity increases
Solution Approach 1:
The functions previously distributed across two converters are merged into a single revamped first converter with an isothermal catalyst bed and optimized purge system, reducing the number of components while concentrating the necessary functionality in one unit
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 the reliability of the ammonia synthesis loop by eliminating the risk of second reactor failure without affecting ammonia concentration or requiring modifications to other loop components, while potentially recovering more hydrogen and reducing energy consumption.
Implementation Method 1
replacing said cartridge with a new cartridge comprising an isothermal catalyst bed
Implementation Method 2
A purge stream is taken from the synthesis loop in order to remove inerts from the loop
Data Source
Figure 1
AI summary
A method for modernizing an ammonia synthesis loop (1) with a first converter (10) and a second converter (11) in series, the first converter (10) comprises a cartridge with one or more catalyst beds, the second converter (11) comprises a catalyst bed in direct contact with said vessel, the method comprising the steps of removing the second converter, boosting the first converter by replacing the cartridge with a new cartridge comprising an isothermal catalyst bed, and reducing the concentration of inerts in said first converter.