Cryogenic CO/N2 Column Pressure Control Using Hydrogen-Rich Recycle
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cryogenic separation processes for mixtures containing carbon monoxide, hydrogen, and nitrogen face challenges when nitrogen content is low, leading to operational instability and pressure issues in CO/N2 columns, as existing methods require a minimum nitrogen level to maintain column pressure and purity.
Innovation Solution
The method involves sending part of the hydrogen-enriched gas from the stripping column to an intermediate point in the nitrogen-removal column or using a detector to regulate the flow rate of hydrogen-enriched gas, allowing for nitrogen compensation by importing hydrogen-rich head gas from the stripping column upstream, thereby maintaining column pressure and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nitrogen content in the mixture is far lower than the design basis, then the condenser has excess heat-exchange surface area leading to complete condensation, but the column operating pressure can no longer be maintained and CO purity is compromised
Solution Approach 1:
The patent introduces an intermediary control mechanism (flow control valve 12) that regulates the recirculation of uncondensed gas from the condenser back to the column inlet. This intermediary control allows the system to maintain stable operating pressure and proper vapor-liquid equilibrium even when nitrogen content varies significantly from design conditions, preventing complete condensation and pressure instability
2Quantity of substance
If the nitrogen content drops below threshold, then the condenser cannot maintain proper recirculation rate, but lowering the bath level is limited by the thermosiphon design requirements
Solution Approach 1:
The patent implements a self-regulating mechanism where the flow control valve 12 automatically adjusts the recirculation flow based on the actual nitrogen content in the mixture. The system monitors nitrogen content and self-adjusts the recirculation rate to maintain proper thermosiphon operation, eliminating the need for manual intervention or complex external control systems while ensuring the condenser operates within its design parameters
3Reliability
If gaseous nitrogen is imported and injected into the impure-CO line to compensate for low nitrogen content, then operational stability is maintained, but additional equipment and complexity are required
Solution Approach 1:
The patent converts the harmful effect of low nitrogen content (which causes condensation and pressure instability) into a beneficial control opportunity. By using the existing uncondensed gas recirculation loop and adding a flow control valve, the system turns a potential failure mode into a self-regulating feature that maintains stability without requiring external nitrogen injection or additional complex equipment
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 decouples the operating pressure of the CO/N2 column from nitrogen content, preventing shutdowns and ensuring stable operation by compensating for nitrogen deficits with hydrogen, eliminating the need for additional nitrogen injection.
Implementation Method 1
the mixture, in liquid form, is sent to the top of a stripping column where it separates to form a hydrogen-lean liquid and a hydrogen-enriched gas
Implementation Method 2
the hydrogen-lean liquid or a fluid derived from this liquid is sent to a nitrogen-removal column where it separates to form a carbon monoxide-enriched liquid and a nitrogen-enriched gas
Implementation Method 3
an uncondensed gas from a head condenser at the top of the separation column
Data Source
AI summary
The invention relates to an apparatus for cryogenic separation of a mixture of carbon monoxide, hydrogen and nitrogen, including a stripping column and a denitrogenation column, a pipe for sending the mixture in liquid form to the head of the stripping column, a pipe for removing a liquid depleted of hydrogen connected to the stripping column, a pipe for removing a gas enriched with hydrogen from the stripping column, means for sending the liquid depleted of hydrogen or a fluid derived from said liquid to the denitrogenation column, a pipe for drawing a liquid enriched with carbon monoxide from the denitrogenation column, a pipe for drawing a gas 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.