Parallel Compressor Control for Stable Biogas RNG Recovery
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Solution Overview
Problem
Conventional RNG facilities face limitations in operability and reliability due to fluctuations in biogas composition and contaminant levels, which affect the integrity of pipeline systems and human/environmental health, necessitating advanced processing facilities that can handle a wide range of inlet gas compositions while meeting strict purity requirements.
Innovation Solution
A system and method for recovering methane from biogas involving compression, chilling, and separation using parallel compressors with common control set points, preferential adsorption, and membrane permeation, along with a computer-based control system for regulating compressor operations to maintain stable discharge pressure and prevent flow disruptions, ensuring efficient methane recovery and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional RNG facilities process biogas with fluctuating composition and contaminant levels, then pipeline quality gas can be produced, but operability and reliability are limited
Solution Approach 1:
The control system dynamically adjusts compressor operations based on real-time biogas composition and flow conditions. The system transitions from static, fixed-operating-point control to dynamic, adaptive control that responds to fluctuating inlet gas characteristics, thereby maintaining reliability while handling variable composition
Solution Approach 2:
The system implements feedback control mechanisms where compressor operations are continuously monitored and adjusted based on discharge pressure, flow rate, and biogas composition measurements. This closed-loop control enables the system to adapt to changing conditions while maintaining stable operation and meeting pipeline quality requirements
2Stability of the object's composition
If parallel compressors are used with common control set points, then stable discharge pressure is maintained, but control system complexity increases
Solution Approach 1:
The patent merges the control functions of multiple parallel compressors into a single unified control system with common set points. Instead of independently controlling each compressor, the system combines their operations under one control architecture, simplifying the control structure while maintaining discharge pressure stability through coordinated operation
Solution Approach 2:
The control system is designed to universally manage multiple compressors simultaneously, allowing a single control mechanism to regulate the combined output of several compressors. This multi-functional approach enables the system to maintain stable discharge pressure while avoiding the complexity of individual compressor control systems
3Stability of the object's composition
If compressor slide valves are frequently adjusted to maintain pressure, then discharge pressure remains stable, but valve sticking and flow disruptions occur
Solution Approach 1:
The system employs dynamic pressure control with deadband hysteresis, where slide valves are adjusted only when pressure deviates beyond predetermined thresholds. This dynamic approach prevents excessive valve actuation while maintaining adequate pressure stability, reducing the frequency of adjustments that cause valve sticking and flow disruptions
Solution Approach 2:
The control system uses feedback mechanisms with deadband parameters that prevent unnecessary valve adjustments. By implementing hysteresis control, the system maintains discharge pressure within acceptable ranges without requiring continuous valve movement, thereby preventing valve sticking and ensuring flow continuity
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 solution enhances methane recovery efficiency, maintains stable gas flow and pressure, reduces methane losses, and improves operational reliability and efficiency by handling varying biogas compositions effectively, meeting strict pipeline quality standards.
Implementation Method 1
the gas stream can be compressed to a pressure of at least 50 psig
Implementation Method 2
The gas stream can be chilled to less than 60 deg F
Implementation Method 3
A majority of trace contaminants can be separated from the gas stream through preferential adsorption of the trace contaminants
Implementation Method 4
A majority of the carbon dioxide can be separated from the gas stream through preferential permeation of carbon dioxide through membranes
Data Source
AI summary
A system and method for recovering high-quality biomethane (RNG) from biogas sources is provided. The gas stream is compressed and liquids are separated from the gas stream at elevated pressure and reduced temperature. The compressing is performed using a plurality of compressors operating in parallel with common control set points. The system and method improve upon conventional practices and yield a biomethane product which meets strict gas pipeline quality specifications. Additionally, the system and method are an improvement to the overall methane recovery efficiency for biogas processing facilities.