Three-Column Cryogenic Air Separation for Flexible Nitrogen Production
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Solution Overview
Problem
Air separation plants with an additional high-pressure column lack flexible operation capabilities, particularly in managing nitrogen production quantities, as they do not have a controllable compressor for compressed nitrogen, leading to inefficiencies in energy consumption and product scaling.
Innovation Solution
The implementation of a three-column air separation system where the first and second columns operate at higher and conventional pressure ranges respectively, with the third column receiving bottom liquids from both, allowing for dynamic sharing of top gas condensates to adjust nitrogen production based on demand, and utilizing a combination compressor for efficient oxygen production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an additional high-pressure column is added to increase nitrogen production capacity, then nitrogen production quantity is improved, but device complexity increases and flexible operation capability deteriorates due to lack of compressor control
Solution Approach 1:
The patent implements dynamic operation modes that allow the air separation plant to switch between different production configurations. The control system dynamically adjusts which columns are active and how they are configured based on real-time demand, enabling flexible nitrogen production without requiring a compressor for the additional high-pressure column.
Solution Approach 2:
The additional high-pressure column is designed to serve multiple functions: it can operate as a nitrogen production column when nitrogen demand is high, or be repurposed to support oxygen production when oxygen demand increases. This multi-functionality allows the plant to maintain flexibility without adding dedicated compression equipment for each product.
2Device complexity
If an additional high-pressure column is added to provide compressed nitrogen without a compressor, then device complexity is reduced by eliminating the compressor, but flexible operation capability deteriorates as control options are lost
Solution Approach 1:
The patent implements dynamic operation modes that allow the air separation plant to switch between different production configurations. The control system dynamically adjusts which columns are active and how they are configured based on real-time demand, enabling flexible nitrogen production without requiring a compressor for the additional high-pressure column.
Solution Approach 2:
The patent utilizes parameter changes in pressure and flow distribution to achieve flexible operation. By adjusting operating parameters such as feed air distribution, reflux ratios, and product withdrawal rates across the multiple columns, the plant can adapt to different production requirements without mechanical compression control.
3Adaptability or versatility
If product quantities are scaled to match demand in a multi-column system, then adaptability is improved, but energy consumption increases due to inefficient column operation
Solution Approach 1:
The patent implements a control system that continuously monitors product demand and adjusts column operation parameters in real-time. This feedback mechanism ensures that columns operate at optimal efficiency points by adjusting feed rates, reflux ratios, and product withdrawal rates to match actual demand, preventing energy waste from operating columns at suboptimal conditions.
Solution Approach 2:
The patent implements dynamic operation modes that allow the air separation plant to switch between different production configurations. The control system dynamically adjusts which columns are active and how they are configured based on real-time demand, optimizing energy utilization while meeting varying product requirements.
4Adaptability or versatility
If compressed nitrogen is produced using further compression in a double-column system, then operation flexibility is improved by enabling compressor turndown or shutdown, but device complexity increases by adding a compressor
Solution Approach 1:
The patent implements dynamic operation modes that allow the air separation plant to switch between different production configurations. The control system dynamically adjusts which columns are active and how they are configured based on real-time demand, providing compressor-like control flexibility through column operation adjustments without adding physical compression 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 configuration enables flexible operation by optimizing nitrogen production, reducing energy consumption, and enhancing oxygen yield without the need for additional compressors or liquid transfer pumps, allowing for efficient scaling of product ratios.
Implementation Method 1
The production of air products in a liquid or gaseous state by low-temperature separation of air in air separation plants is known and is described, for example, by H.-W. Häring (ed.), Industrial Gases Processing, Wiley-VCH, 2006, in particular Section 2.2.5, 'Cryogenic Rectification'.
Implementation Method 2
The additional column is operated with a condenser evaporator which condenses overhead gas from the additional column so that reflux to the additional column can be provided.
Implementation Method 3
a third column (11) in particular structurally separately from the second column (12) and the third column (13), with the second column (12) and the third column (13) being part of a double column in particular and using a corresponding main condenser, can be in heat-exchanging connection with each other.
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a process for the low-temperature separation of air, in which an air separation plant (100, 200) is used, comprising a first column (11), a second column (12), and a third column (13), wherein the first column (11) is operated in a first pressure range, the second column (12) in a second pressure range below the first pressure range, and the third column (13) in a third pressure range below both the first and second pressure ranges, wherein the third column (13) is fed with bottom liquid from the first column (11) and bottom liquid from the second column (12), wherein a first top gas condensate is formed from the overhead gas of the first column (11) and a second top gas condensate is formed from the overhead gas of the second column (12), and wherein further overhead gas from the first column (11) is extracted gaseous from the air separation plant (100, 200). is expelled.It is provided that the further overhead gas of the first column (11), which is discharged in gaseous form from the air separation unit (100, 200), is discharged from the air separation unit (100, 200) in a first operating mode in a first quantity per unit of time and in a second operating mode in a second quantity per unit of time, which is lower than the first quantity per unit of time. In the first operating mode, a portion of the second overhead gas condensate is transferred to the first column (11), and in the second operating mode, a portion of the first overhead gas condensate is transferred to the first column (11). An air separation unit (100, 200) is also part of the present invention.