Compressor Control Using Real-Time Gas Liquid Flow Measurement
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Solution Overview
Problem
Conventional gas compressor control systems are inaccurate and unreliable when dealing with changing gas compositions or the presence of liquids, leading to potential surge conditions and inefficient operation, as they fail to accurately measure total volumetric flow rates and fluid properties.
Innovation Solution
A method and apparatus that integrate real-time measurement of gas and liquid flow rates, fluid composition, and properties to accurately determine the compressor's operation point, using a flow metering device that measures individual fractions of gas, water, and non-aqueous liquids, and calculates polytropic head and efficiency, enabling precise control of anti-surge valves and hot gas bypass valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional control systems use standard flow measurement methods, then the system is simple to operate, but the measurement precision deteriorates when gas composition changes or liquids are present
Solution Approach 1:
The flow measurement system is segmented into multiple independent measurement components: a first flow measurement device for measuring total flow rate, a second flow measurement device for measuring gas flow rate specifically, and a composition measurement device for measuring gas composition. This segmentation allows each device to be optimized for its specific measurement task, maintaining high precision even when gas composition changes or liquids are present.
Solution Approach 2:
The invention introduces an intermediary calculation process that uses measurements from multiple devices (total flow rate, gas flow rate, composition) to derive the liquid flow rate and corrected volumetric flow rate. This intermediary approach allows the system to compensate for measurement errors caused by changing gas composition or liquid presence, maintaining high measurement precision without requiring a single complex measurement device.
2Productivity
If the compressor operates close to the surge limit to increase productivity, then the productivity increases, but the reliability deteriorates due to potential surge conditions
Solution Approach 1:
The control system continuously monitors the actual volumetric flow rate, gas composition, and compressor operating parameters, and uses this feedback to dynamically adjust the compressor operation. The system calculates the actual surge limit based on real-time composition measurements and adjusts the operating point accordingly, allowing the compressor to operate close to the surge limit safely and maintain high productivity without compromising reliability.
Solution Approach 2:
The invention implements dynamic surge limit calculation that adapts to changing gas composition and operating conditions. Instead of using a fixed surge limit, the system continuously updates the surge limit based on real-time measurements of gas composition, temperature, and pressure, allowing the compressor to dynamically operate at the maximum safe capacity and maintain high productivity while preventing surge conditions.
3Measurement precision
If real-time composition measurement is implemented to improve control accuracy, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The composition measurement device is designed to measure multiple parameters simultaneously (gas composition, temperature, pressure) and provide data for multiple purposes: calculating liquid flow rate, determining actual volumetric flow rate, and establishing the surge limit. This multi-functionality reduces the need for separate measurement devices and maintains high measurement precision while limiting the increase in device complexity.
Data Source
AI summary
A method and apparatus controls a compressor, where the compressor inlet gas may contain water and/or non-aqueous liquid. The method includes the steps of measuring temperature at the compressor inlet and/or outlet side, measuring pressure at the compressor inlet and outlet side in order to determine a compressor pressure ratio, measuring fluid mixture density at the compressor inlet and/or outlet side, measuring individual volume fractions of gas, water and non-aqueous liquid at the compressor inlet and/or outlet side, measuring fluid velocity at the compressor inlet and/or outlet side, and determining individual flow rates of gas, water and non-aqueous liquid on the basis of the measured individual volume fractions of gas, water and non aqueous liquid and the fluid velocity at the compressor inlet and/or outlet side.