Cryogenic Distillation Tower CO2 Separation During Start-Up
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Solution Overview
Problem
During abnormal operations, such as start-up, cryogenic distillation towers face challenges in maintaining steady-state conditions necessary for effective separation of carbon dioxide from methane, leading to higher CO2 concentrations and potential solidification outside the controlled freeze zone, which complicates the separation process.
Innovation Solution
The system includes a rectifier section and a controlled freeze zone in the distillation tower, where a carbon dioxide-free cryogenic fluid is fed to reduce CO2 concentration by spraying it into the controlled freeze zone, and accumulating the stream in a holding vessel or sump to stabilize the process, ensuring the CO2 concentration is within acceptable limits before allowing it to proceed to the upper section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional distillation is used to separate CO2 from methane, then the separation process can operate under normal steady-state conditions, but during abnormal operations (such as start-up), the CO2 concentration increases and solidification occurs outside the controlled freeze zone, complicating the separation process
Solution Approach 1:
The patent applies preliminary action by introducing a carbon dioxide-free cryogenic fluid into the controlled freeze zone section before the abnormal operation (start-up) is complete. This preemptive measure lowers the temperature and establishes the proper conditions for CO2 solidification within the controlled zone, preventing solidification outside the zone and enabling a smooth transition to normal operating conditions.
2Manufacturing precision
If cryogenic distillation is used to achieve pipeline quality hydrocarbon product, then CO2 can be separated effectively, but CO2 solidifies outside the controlled freeze zone during abnormal operations, creating operational complications
Solution Approach 1:
The patent applies parameter changes by modifying the temperature parameter in the controlled freeze zone section through the introduction of carbon dioxide-free cryogenic fluid. This temperature adjustment ensures that CO2 solidifies only within the controlled freeze zone at the appropriate location, maintaining product quality while simplifying process control during the transition from abnormal to normal operations.
3Ease of operation
If the distillation tower operates at warmer temperatures during abnormal operations, then the operation is easier to maintain, but CO2 concentration increases and prevents sufficient CO2 knock-out
Solution Approach 1:
The patent applies local quality by creating a localized cold zone within the controlled freeze zone section through the introduction of carbon dioxide-free cryogenic fluid. This localized temperature reduction ensures that CO2 solidifies in the correct location while the rest of the tower can operate at relatively warmer temperatures, maintaining ease of operation while effectively reducing CO2 concentration in the product stream.
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 method effectively reduces CO2 concentration in the stream, preventing solidification and facilitating the transition from abnormal to normal operating conditions, thereby improving the separation efficiency of carbon dioxide from methane during start-up and normal operations.
Implementation Method 1
reducing a carbon dioxide concentration of the stream received by the rectifier section by: feeding a first cryogenic fluid to the controlled freeze zone section
Implementation Method 2
maintaining a controlled freeze zone section in the distillation tower that forms solids from carbon dioxide within the distillation tower
Implementation Method 3
accumulating rectifier section stream in at least one of a holding vessel and a sump of the rectifier section
Data Source
AI summary
A method and system for separating fluids in a distillation tower. The method may include feeding a stream to the distillation tower, wherein the stream includes carbon dioxide, reducing a carbon dioxide concentration of the stream received by the rectifier section by feeding a first cryogenic fluid to the controlled freeze zone section and accumulating rectifier section stream in at least one of a holding vessel and a sump of the rectifier section, and terminating reducing the carbon dioxide concentration when the carbon dioxide concentration of the stream travelling from the controlled freeze zone section to the rectifier section is less than or equal to a maximum carbon dioxide concentration. The first cryogenic fluid may comprise a substantially carbon-dioxide-free fluid.