Method and apparatus for eliminating heat bumps following regeneration of adsorbers in an air separation unit
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Solution Overview
Problem
Existing air separation unit processes experience temperature excursions and inefficiencies due to inadequate cooling of adsorbers during the regeneration cycle, leading to process upsets and increased heat duty in the heating step.
Innovation Solution
Cooling the waste nitrogen gas using chilled water in a regeneration cooler to match the adsorber temperature to that of the normal adsorption cycle, thereby maintaining constant dry air temperature post-switchover, and utilizing a regeneration gas cooler in parallel with the regeneration gas heater to manage heat exchange efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the waste nitrogen stream is removed from the main heat exchanger at a colder temperature, then the adsorber cooling effect is improved, but the heat exchange efficiency deteriorates and heat duty increases
Solution Approach 1:
The cooling process is divided into two separate stages: first, the waste nitrogen stream is cooled in the main heat exchanger to a moderate temperature; second, a dedicated regeneration cooler further cools the stream to the required low temperature for adsorber regeneration. This segmentation allows each cooler to operate optimally without compromising overall heat exchange efficiency.
Solution Approach 2:
The regeneration cooler acts as an intermediary device between the main heat exchanger and the adsorber. It receives the pre-cooled waste nitrogen stream, performs additional cooling, and delivers the stream at the appropriate temperature to the adsorber, thereby resolving the conflict between cooling effectiveness and heat exchange efficiency.
2Stability of the object's composition
If the BAC is oversized to accommodate temperature increase, then the temperature disturbance is minimized, but the device complexity and cost increase
Solution Approach 1:
The waste nitrogen stream is pre-cooled in the regeneration cooler before being introduced to the adsorber. This preliminary cooling action ensures that the temperature of the stream entering the adsorber is already optimized, eliminating the need for the BAC to be oversized as a compensatory measure for temperature instability.
3Device complexity
If the regeneration gas is not sufficiently cooled, then the process is simpler, but heat bumps occur causing process upsets
Solution Approach 1:
The waste nitrogen stream, which would otherwise be a waste product, is converted into a beneficial cooling medium for the adsorber regeneration process. By cooling this stream in the regeneration cooler, the harmful heat bump effect is eliminated while simultaneously utilizing the waste stream for useful cooling purposes.
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 reduces heat bumps and operational disturbances, allowing for a more efficient and stable air separation process with reduced heat duty and equipment oversizing, enhancing overall process efficiency.
Implementation Method 1
Cooling the waste nitrogen gas using chilled water in a regeneration cooler
Implementation Method 2
compressed wet air from a main air compressor is cooled to approximately 53° F. by chilled water in a direct contact tower
Implementation Method 3
introducing the cooled air stream in the distillation column system under conditions effective for rectification of air into nitrogen and oxygen
Implementation Method 4
FEP adsorbers are operated alternatively between adsorption A and regeneration R cycle
Data Source
AI summary
A method for reducing heat bumps following regeneration of adsorbers in an air separation unit is provided. The air separation unit can include a front end purification unit, a main air compressor, a main heat exchanger, a distillation column system, a regeneration gas heater, and a regeneration gas cooler, wherein the front end purification unit comprises a first adsorber and a second adsorber. The method can include the steps of: regenerating the first adsorber while the second adsorber operates in an adsorption cycle, wherein the step of regenerating the first adsorber further includes the steps of heating the first adsorber and then cooling the first adsorber, wherein during the step of cooling the first adsorber, a regeneration gas sourced from the distillation column system and cooled in the main heat exchanger is further cooled in a regeneration gas cooler prior to being used to cool the first adsorber.