Intermediate Pressure Kettle Column for Air Separation Reflux
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Solution Overview
Problem
Conventional three-column air separation units face challenges in producing normal purity oxygen and argon with high efficiency, characterized by high power consumption and limited nitrogen and argon recovery due to a tight pinch in the lower pressure column and limited nitrogen reflux production.
Innovation Solution
A four-column arrangement comprising a higher pressure column, a lower pressure column, an intermediate pressure kettle column, and an argon column, where the intermediate pressure kettle column generates additional nitrogen reflux and an argon product stream, and the argon column condenser is integrated within the lower pressure column to enhance mass transfer driving forces and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional three-column arrangement is used for normal purity oxygen and argon production, then the separation can be achieved, but the power consumption is high and the mass transfer driving forces are insufficient
Solution Approach 1:
The patent divides the distillation system into four separate columns operating at different pressure levels (high pressure, intermediate pressure, low pressure, and argon column). This segmentation allows each column to operate optimally within its pressure range, creating sufficient mass transfer driving forces while improving overall energy efficiency compared to a conventional three-column arrangement.
Solution Approach 2:
The patent introduces an intermediate pressure dimension between the conventional high and low pressure columns. This additional pressure level creates a gradient that enhances mass transfer driving forces across all columns while reducing the energy penalty associated with large pressure differentials, thereby resolving the contradiction between power consumption and separation efficiency.
2Manufacturing precision
If the lower pressure column operates with tight approach between equilibrium line and operating line, then oxygen and argon separation is achieved, but the nitrogen reflux production is limited
Solution Approach 1:
The patent separates the nitrogen reflux generation function into a dedicated high pressure column and an intermediate pressure column. The high pressure column generates nitrogen-rich vapor that is condensed to provide reflux for the low pressure column, while the intermediate pressure column handles the oxygen-argon separation. This functional segmentation allows sufficient nitrogen reflux production without compromising the tight separation required for oxygen and argon purity.
Solution Approach 2:
The intermediate pressure column acts as an intermediary between the high pressure nitrogen generation column and the low pressure oxygen-argon separation column. It receives kettle liquid from the high pressure column, performs preliminary separation, and provides both nitrogen reflux (after condensation) and feed to the low pressure column, thereby resolving the conflict between nitrogen reflux quantity and separation precision.
3Productivity
If an intermediate pressure kettle column is added to generate additional nitrogen reflux, then the oxygen and argon recovery increases, but the device complexity increases
Solution Approach 1:
The intermediate pressure kettle column serves multiple functions: it generates nitrogen-rich vapor for reflux, performs preliminary oxygen-argon separation, and provides feed to both the high pressure and low pressure columns. By making this column multi-functional, the patent achieves improved oxygen and argon recovery without requiring additional columns for each function, thereby limiting the increase in device complexity.
Solution Approach 2:
The intermediate pressure kettle column uses its own internal vapor-liquid equilibrium to generate the nitrogen reflux needed by the low pressure column, rather than requiring external compression or additional processing equipment. The column self-regulates the reflux composition and quantity through its pressure-level operation, reducing the need for complex external control systems and improving productivity with moderate complexity increase.
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 configuration increases oxygen and argon recovery, reduces power consumption, and provides additional product flexibility by generating supplemental nitrogen and argon products, improving efficiency over conventional three-column and some intermediate column arrangements.
Implementation Method 1
a main condenser-reboiler disposed in the lower pressure column and configured for thermally coupling the higher pressure column and the lower pressure column by liquefying at least a portion of the nitrogen-rich overhead from the higher pressure column against the oxygen liquid at the bottom of the lower pressure column
Implementation Method 2
an argon column arrangement with an argon condenser disposed within the lower pressure column configured to condense an argon-rich overhead against a portion of the descending liquid in the lower pressure column to produce a crude argon stream
Implementation Method 3
separating air by cryogenic distillation using a distillation column system that includes an intermediate pressure kettle column
Implementation Method 4
The present system and method relates to separating air by cryogenic distillation
Data Source
AI summary
An air separation unit and associated method for separating air by cryogenic distillation using a distillation column system including a higher pressure column, a lower pressure column, an intermediate pressure kettle column, and an argon column arrangement is provided. The disclosed air separation unit and method is particularly suited for production of an oxygen product as well as several nitrogen products wherein a portion of the nitrogen overhead intermediate pressure kettle column is taken as an intermediate pressure nitrogen product. The present air separation unit and associated method employs a once-through kettle column reboiler, a once-through kettle column condenser, and a once-through argon condenser. The once through argon condenser is disposed within the lower pressure column where an argon-rich vapor stream is condensed against the descending liquid in the lower pressure column.