VPSA Centrifugal Compressor Anti-Surge Control
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Solution Overview
Problem
Centrifugal compressors in vacuum pressure swing adsorption processes often encounter surge conditions due to lag in control systems, transitional steps, and changes in ambient conditions, leading to unstable operation and potential damage, especially during high-speed operations in evacuation and purge steps.
Innovation Solution
A method and control system that dynamically adjusts the speed of a centrifugal compressor driven by an electric motor using a variable frequency drive, measuring flow rates and pressure ratios to determine optimal speeds and apply feedback and feedforward multipliers to prevent surge conditions, particularly during evacuation and purge steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the compressor speed is increased to match the varying pressure ratio requirements during different process steps, then the compressor can operate near peak efficiency, but the compressor may enter surge conditions during evacuation and purge steps
Solution Approach 1:
The patent implements dynamic speed adjustment by continuously varying the compressor speed to match the varying pressure ratio requirements during different VPSA process steps. The controller receives pressure ratio signals and adjusts motor speed accordingly, allowing the compressor to operate near peak efficiency during pressurization while preventing surge during evacuation and purge steps through real-time speed modulation.
Solution Approach 2:
The patent employs feedback control by continuously monitoring the pressure ratio across the compressor and using this information to adjust the motor speed. The controller receives pressure signals from transducers, calculates the pressure ratio, and adjusts the compressor speed to maintain optimal operation while avoiding surge conditions, creating a closed-loop control system.
2Productivity
If the compressor operates at high speed during evacuation and purge steps, then the productivity of the VPSA process is improved, but the compressor encounters surge conditions causing unstable operation
Solution Approach 1:
The patent applies preliminary action by anticipating surge-prone conditions during evacuation and purge steps and adjusting the compressor speed in advance to prevent surge. The controller is programmed to recognize these process steps and modulate speed proactively, preventing the harmful surge condition before it occurs rather than reacting after surge begins.
3Device complexity
If a conventional induction motor/gearbox system is used to drive the centrifugal compressor, then the system structure is simpler, but the compressor cannot accelerate and decelerate quickly due to high inertia
Solution Approach 1:
The patent replaces the conventional mechanical induction motor/gearbox drive system with a direct-drive high-speed permanent magnet motor. This substitution eliminates the gearbox and reduces rotational inertia, enabling rapid acceleration and deceleration of the centrifugal compressor to match the dynamic requirements of the VPSA process while maintaining a relatively simple overall system structure.
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
The system effectively prevents surge conditions by adjusting compressor speeds, ensuring stable operation and extending the lifespan of compressor components by maintaining the compressor on its peak efficiency operating line, even during critical high-speed phases.
Implementation Method 1
a centrifugal compressor operating within a vacuum pressure swing adsorption apparatus and directly driven by an electric motor controlled by a variable frequency drive
Implementation Method 2
the pressure ratio of outlet to inlet pressure of the compressor
Data Source
AI summary
The present invention relates to a method and control system to control the speed of a centrifugal compressor operating within a vacuum pressure swing adsorption process to avoid an operation at which surge can occur and directly driven by an electric motor that is in turn controlled by a variable frequency drive. In accordance with present invention an optimal speed for operation of the compressor is determined at which the compressor will operate along a peak efficiency operating line of a compressor map thereof. This speed is adjusted by a feed back speed multiplier when the flow or other parameter referable to flow through the compressor is below a minimum and a feed forward multiplier during evacuation and evacuation with purge steps that multiplies the feed back multiplier to increase speed of the compressor and thereby avoid surge.