Cryogenic Compressor Inlet Control to Prevent Overspeed Trips
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Solution Overview
Problem
Cryogenic cooling systems face challenges in maintaining stable operation during start-up and cool-down phases, particularly in avoiding overspeeds and temperature fluctuations that lead to compressor trip and inefficient pump-down processes.
Innovation Solution
A method involving real-time monitoring and control of compressor speeds and pressures, using detected actual and desired values to adjust inlet temperatures and speeds, ensuring uninterrupted pump-down and cool-down processes by prioritizing pressure and temperature control based on proportional and priority values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the compressors are started at the same time as the system during cool-down, then the pump-down process can begin immediately, but the compressors reach maximum speeds quickly due to high gas temperature and low density, causing overspeeds and requiring repeated interruptions
Solution Approach 1:
The system performs preliminary cooling of the fluid before starting the compression process. During the cool-down phase, the fluid is cooled to a lower temperature (increasing its density) before the compressors begin operation, which allows the compressors to operate at controlled speeds from the start without reaching maximum speeds quickly
Solution Approach 2:
The control system continuously monitors the actual temperature and pressure at the inlet of the first compressor, along with the actual speeds of all compressors. Based on this feedback, the system dynamically adjusts the desired inlet temperature and desired speeds to maintain optimal operating conditions and prevent overspeeds
2Productivity
If the compressors operate without temperature control during cool-down, then the compression process can proceed continuously, but the temperature increase during compression causes the outlet temperature to reach problematic levels (4K-23K)
Solution Approach 1:
The system pre-cools the fluid to a lower temperature before compression begins. This preliminary cooling action ensures that even after the temperature increase during compression (4K-23K rise), the outlet temperature remains at acceptable levels for downstream components
Solution Approach 2:
The control system dynamically adjusts the inlet temperature parameter during operation. By controlling the desired inlet temperature based on actual measurements and priority values, the system maintains the outlet temperature within acceptable ranges while allowing continuous compression operation
3Use of energy by moving object
If the inlet pressure is controlled to achieve desired saturation temperature, then the compression efficiency is improved, but the entry conditions of downstream compressors are affected by speed changes of upstream compressors
Solution Approach 1:
The control system monitors the actual pressure and temperature at the inlet of the first compressor and the actual speeds of all compressors. Based on this feedback, it dynamically adjusts the desired inlet temperature and desired speeds to maintain both compression efficiency and stable entry conditions for all compressors in the series
Solution Approach 2:
The system uses dynamic control where the desired inlet temperature and desired speeds are continuously adjusted based on actual measurements. This dynamic adaptation allows the system to maintain optimal compression efficiency while compensating for the interdependent effects of speed changes on downstream compressor entry conditions
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 method allows for continuous pump-down and cool-down operations, preventing overspeeds and maintaining suitable temperatures for downstream components, ensuring efficient and uninterrupted operation of cryogenic compressor systems.
Implementation Method 1
the pressure at the output of the series as well as the temperature of the fluid flowing through the compressor is increased (polytropic compression process)
Implementation Method 2
A cooling reservoir (5) upstream of the inlet of the first compressor (V1) is provided, in particular for cooling the fluid to be compressed
Data Source
AI summary
A method for pressure and temperature control of fluid in a series of cryogenic compressors. An actual speed for each compressor and an actual inlet pressure and actual inlet temperature at entry are determined. The maximum speed for each compressor and a desired inlet pressure for the first compressor is provided. A speed index for each compressor is determined from the maximum speed and actual speed of each compressor. A proportional value is determined from the deviation of the actual and desired inlet pressure. A priority value is determined from the smaller of the proportional value and the smallest speed index. A desired inlet temperature for the first compressor and a desired speed for each compressor are determined from the priority value. The actual inlet temperature is adjusted to the determined desired inlet temperature and the actual speed for each compressor is adjusted to the determined desired speed.