Compressor Control System for Ammonia Synthesis Plants
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Solution Overview
Problem
Existing control systems for rotary compressors driven by rotary engines in synthesis plants, such as those used in ammonia production, face instability due to variations in gas mixture composition, requiring manual intervention to avoid amplifying disturbances and reaching unstable conditions.
Innovation Solution
A fully-automatic control system comprising two control subsystems and a selector, which adjusts the compressor's rotational speed based on performance and rotation speed signals, allowing for seamless operation even with varying gas mixture compositions without human intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a typical control system determines load demand based on suction pressure and adjusts engine speed accordingly, then the control system works well when gas mixture composition is constant, but the control system becomes unstable and requires manual intervention when gas mixture composition varies
Solution Approach 1:
The control system is divided into two separate control subsystems: a first control subsystem that determines load demand based on suction pressure and rotation speed, and a second control subsystem that determines load demand based solely on suction pressure. A selector then chooses between the two subsystems based on operating conditions, allowing the system to adapt to gas composition variations without manual intervention
Solution Approach 2:
The control system dynamically switches between two different control strategies based on operating conditions. The selector monitors the operating state and automatically transitions between the first control subsystem (for stable composition conditions) and the second control subsystem (for varying composition conditions), enabling full automatic adaptation to changing gas mixture compositions
2Ease of operation
If the control system operates in automatic mode with single-subsystem control, then the operation is simplified, but the system reaches unstable conditions and requires switching to manual mode when disturbances occur
Solution Approach 1:
The selector acts as an intermediary between the two control subsystems and the engine control. It automatically monitors operating conditions and selects the appropriate control subsystem output, eliminating the need for manual mode switching while maintaining system stability under various disturbance conditions
3Device complexity
If the control system uses a single control subsystem, then the device complexity is reduced, but the system cannot compensate for variations in gas mixture composition
Solution Approach 1:
The control system achieves multi-functionality by incorporating two control subsystems with different control strategies. The first subsystem handles stable operating conditions while the second subsystem handles varying composition conditions. The selector enables the system to universally adapt to different operating scenarios, compensating for gas mixture composition variations without requiring complex additional hardware
Data Source
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AI summary
The control system 200 is arranged for a rotary compressor driven by a rotary engine, and comprises: a first control subsystem 210, a second control subsystem 220 and a selector 230; the first control subsystem 210 is arranged to provide a first control signal 26 as a function of the performance 21 and the speed 23 of the compressor; the second control subsystem 220 is arranged to provide a second control signal 27 as a function of the performance 22 of the compressor; the selector 230 is arranged to select the first control signal 26 or the second control signal 27 as a third control signal 24 to be provided to a power control input of the engine.