Variable-Speed Air Compression for Cryogenic Plant Turndown
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Solution Overview
Problem
Cryogenic air separation plants face high energy costs due to inefficient compression processes, with conventional systems requiring significant power for compression and limited turndown capabilities, leading to reduced efficiency and increased operational costs.
Innovation Solution
Implementing a method using direct drive compression assemblies with variable speed drives to control the compression of incoming feed air streams, allowing for adjustable discharge pressures and flow rates, and incorporating a split functional air compression train to optimize compression stages and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional multi-stage MAC compression arrangements are used to achieve desired discharge pressure and flow, then compression capability is improved, but energy consumption increases significantly
Solution Approach 1:
The patent applies variable speed drives to the compressor stages, allowing dynamic adjustment of rotational speeds to match actual process demands. This enables the compression system to operate at optimal efficiency points across varying load conditions rather than running at fixed high speeds, thereby reducing energy consumption while maintaining compression capability.
Solution Approach 2:
The invention changes operational parameters by implementing variable speed control across multiple compressor stages, adjusting flow rates and discharge pressures dynamically. This allows the system to adapt compression intensity to actual needs, avoiding unnecessary energy expenditure while maintaining required compression performance.
2Stability of the object's composition
If conventional compression systems operate at fixed speeds to maintain stable discharge pressure, then operational stability is improved, but turndown capability deteriorates
Solution Approach 1:
The patent implements variable speed drives on compressor stages that can dynamically adjust rotational speeds to maintain stable discharge pressures across varying flow conditions. This dynamic control enables the system to adapt to different turndown requirements while preserving operational stability through active pressure regulation.
Solution Approach 2:
The invention incorporates control systems that monitor discharge pressure and flow conditions, providing feedback to adjust compressor speeds accordingly. This feedback mechanism ensures operational stability is maintained even as the system adapts to varying turndown requirements through real-time parameter adjustments.
3Use of energy by moving object
If multiple compression stages are used to achieve high discharge pressure, then compression efficiency is improved, but device complexity increases
Solution Approach 1:
The patent divides the compression process into multiple independent stages, each equipped with its own variable speed drive. This segmentation allows each stage to be optimized and controlled independently, improving overall compression efficiency through staged pressure increases while managing complexity through modular design and control.
Solution Approach 2:
The invention applies universal variable speed drive technology across multiple compressor stages, allowing the same control mechanism to be used throughout the compression train. This multi-functionality approach improves compression efficiency through coordinated stage operation while reducing complexity by using standardized components and control strategies across all stages.
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 energy consumption by optimizing compression efficiency, enabling greater turndown capabilities and maintaining high plant efficiency across varying operating conditions, thereby lowering operational costs.
Implementation Method 1
at least one compression stage in the lower pressure single stage or multi-stage compressor driven directly by a first variable speed drive assembly
Implementation Method 2
compressing at least a portion of the incoming feed air stream in a lower pressure single stage or multi-stage compressor
Implementation Method 3
The compressed, incoming feed air stream is then purified in a pre-purification unit to remove high boiling contaminants from the incoming feed air stream. Such a pre-purification unit typically has beds of adsorbents to adsorb such contaminants as water vapor, carbon dioxide, and hydrocarbons.
Implementation Method 4
The plurality of cooled, compressed air streams are then directed to two-column or three column cryogenic air distillation column system which includes a higher pressure column thermally linked or coupled to a lower pressure column
Implementation Method 5
The plurality of cooled, compressed air streams are then directed to two-column or three column cryogenic air distillation column system
Implementation Method 6
Prior to entering the higher pressure column and lower pressure columns, any liquid air streams may be expanded in a Joule-Thompson valve to produce still further refrigeration required for producing the cryogenic products
Data Source
AI summary
A method for compression of an incoming feed air stream using at least two variable speed compressor drive assemblies controlled in tandem is provided. The first variable speed drive assembly drives at least one compression stage in the lower pressure compressor unit driven while the second variable speed drive assembly drives higher pressure compression stage disposed either in the common air compression train or the split functional compression train of the air separation plant. The first and second variable speed drive assemblies are preferably high speed, variable speed electric motor assemblies each having a motor body, a motor housing, and a motor shaft with one or more impellers directly and rigidly coupled to the motor shaft via a sacrificial rigid shaft coupling.