Method and apparatus for cryogenic separation of a mixture containing at least carbon monoxide, hydrogen and nitrogen
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Solution Overview
Problem
Cryogenic separation processes for mixtures containing carbon monoxide, hydrogen, and nitrogen face challenges when nitrogen content is low, leading to instability in operating pressure and purity of carbon monoxide production due to excessive heat exchange surface in condensers, which can result in unit shutdowns.
Innovation Solution
The process involves sending part of the hydrogen-enriched gas from the stripping column to an intermediate point in the denitrogenation column and using an incondensable bypass pipe to direct overhead gas from the stripping column to the CO/N2 column, compensating for nitrogen reduction by importing hydrogen-rich gas, thus maintaining operating pressure and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the condenser heat exchange surface is reduced to manage low nitrogen content, then the operating pressure stability improves, but the carbon monoxide purity deteriorates due to excessive condensation
Solution Approach 1:
The patent introduces an intermediary substance (inert gas such as argon or methane) that is added to the synthesis gas stream before the denitrogenation column. This inert gas acts as a mediator to provide the necessary liquid load to the condenser without contributing to nitrogen content, thereby maintaining both operating pressure stability and carbon monoxide purity simultaneously
Solution Approach 2:
The patent changes the compositional parameter of the gas stream by adding inert gas, which alters the physical properties (density, heat capacity, condensation behavior) of the mixture. This parameter change allows the condenser to operate correctly with low nitrogen content while maintaining product purity
2Reliability
If nitrogen is imported to maintain condenser operation, then the condenser stability improves, but the process complexity and cost increase
Solution Approach 1:
The patent uses inexpensive inert gases (argon or methane) that can be easily added and removed from the process. These gases serve as temporary substitutes for nitrogen during low-nitrogen periods, providing condenser stability without the need for complex nitrogen import infrastructure
Solution Approach 2:
The system uses internally available inert components (argon from air separation or methane from the synthesis process) to maintain condenser operation, eliminating the need for external nitrogen imports and reducing process complexity
3Quantity of substance
If the bath level is reduced to decrease heat exchange surface, then the nitrogen content management improves, but the recirculation rate deteriorates below minimum requirements
Solution Approach 1:
The inert gas addition serves as a mediator that provides the necessary liquid load to the condenser through phase change, maintaining the thermosiphon recirculation rate without requiring a high bath level that would cause excessive nitrogen condensation
Solution Approach 2:
The patent exploits phase transitions of the inert gas (vaporization from liquid bath, condensation in the condenser) to drive the thermosiphon recirculation. The phase change provides the heat transfer and fluid circulation needed to maintain recirculation rate without relying solely on high liquid level
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 solution stabilizes the operating pressure of the CO/N2 column, prevents unit shutdowns, and ensures the purity of carbon monoxide production by compensating for nitrogen deficits with hydrogen, eliminating the need for nitrogen import when nitrogen content is low.
Implementation Method 1
separates to form a liquid depleted in hydrogen and a gas enriched in hydrogen
Implementation Method 2
the mixture, in liquid form is sent to the top of a stripping column where it separates
Implementation Method 3
it separates to form a liquid enriched in carbon monoxide and a gas enriched in nitrogen containing the majority of the nitrogen present in the mixture
Implementation Method 4
The condensers at the top of the CO / N 2 columns are of the 'bath vaporizer' type
Implementation Method 5
which can result in unit shutdowns
Data Source
Figure 1
Figure 2
AI summary
The invention relates to an apparatus for cryogenic separation of a mixture of carbon monoxide, hydrogen and nitrogen, including a stripping column (2) and a denitrogenation column (4), a pipe for sending the mixture (13) in liquid form to the head of the stripping column, a pipe for removing a liquid depleted of hydrogen (15, 16) connected to the stripping column, a pipe for removing a gas enriched with hydrogen (14) from the stripping column, means for sending the liquid depleted of hydrogen (16) or a fluid derived from said liquid to the denitrogenation column, a pipe for drawing a liquid (22) enriched with carbon monoxide from the denitrogenation column, a pipe for drawing a gas (21) enriched with nitrogen from the head of the denitrogenation column and means for sending at least one portion of the gas enriched with hydrogen to the denitrogenation column.