External Gas Adsorber Repressurization for Cryogenic Air Separation
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Solution Overview
Problem
Current air separation processes face challenges in maintaining constant air flow and compressor capacity during repressurization, leading to process upsets and increased capital expenditures due to varying air flow rates and composition changes.
Innovation Solution
The method involves using an external dry gas, such as nitrogen or purified air, to repressurize the adsorber without diverting purified air from the online adsorber or changing the main air compressor flow rate, ensuring a constant air flow to the cold box and minimizing capital expenditures by maintaining consistent process conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If purified air is diverted to repressurize the adsorber during regeneration, then the adsorber can be repressurized, but the air flow to the cold box varies and process upsets occur
Solution Approach 1:
The invention extracts the repressurization function from the purified air stream by introducing an external inert gas source. This separates the repressurization operation from the main air flow path, allowing the adsorber to be repressurized without diverting purified air from the online adsorber or changing the main air compressor flow rate.
Solution Approach 2:
An external inert gas (nitrogen or purified air from independent source) serves as an intermediary substance to perform the repressurization function. This mediator allows the adsorber to be repressurized during regeneration without affecting the main air flow to the cold box, as the inert gas does not interfere with the cryogenic separation process.
2Ease of operation
If the main air compressor flow rate is changed during repressurization, then the adsorber can be repressurized, but capital expenditures increase due to varying air flow rates
Solution Approach 1:
The invention extracts the repressurization function from the main air compressor by using an external gas source. This allows the compressor to maintain constant flow rate and capacity, eliminating the need for oversized equipment that would be required to handle flow rate variations during repressurization cycles.
Solution Approach 2:
The external inert gas is prepared and made available before the repressurization step is needed. This preliminary preparation allows immediate repressurization without requiring the main air compressor to change its operating parameters, thus avoiding the need for increased compressor capacity and associated capital expenditures.
3Ease of operation
If purified air composition changes during repressurization, then the adsorber can be repressurized, but process conditions become unstable
Solution Approach 1:
The invention uses an external inert gas (nitrogen or purified air from independent source) to create an inert repressurization environment. This inert atmosphere does not interfere with the cryogenic separation process or alter the composition of the air stream going to the cold box, maintaining stable process conditions throughout the repressurization operation.
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 allows the main air compressor to operate at a constant capacity and maintain a stable air flow to the cold box, reducing process upsets and capital expenditures related to warm-end equipment, while maintaining consistent process conditions throughout the air separation unit.
Implementation Method 1
purification of the air by adsorption of the impurities at superatmospheric pressure
Implementation Method 2
compressing atmospheric air to a pressure suitable for the cryogenic rectification of air
Implementation Method 3
cooling the purified air in a heat exchanger by indirect heat exchange against process streams from the cryogenic distillation column
Implementation Method 4
introducing the cold air into the distillation column for rectification therein; collecting nitrogen from the top of the column (typically as a gas) and collecting oxygen from the bottom of the column as a liquid
Data Source
AI summary
A method and apparatus for the production of air gases by the cryogenic separation of air with front end purification and air compression can include using an available compressed dry gas such as nitrogen, oxygen, stored purified air, or synthetic air to repressurize the adsorber without diverting any of the purified air just exiting the currently on-line adsorber or changing the flow rate of the main air compressor or air sent to the cold box. This enables the main air compressor (MAC) to operate at a relatively constant flow rate while also sending a relatively constant air flow to the cold box during this repressurization step, thereby reducing the risks of process upsets and minimizing capital expenditures related to the MAC and other warm-end equipments.