Gas Mixture Quality Monitoring via Throttled Dew Point Measurement
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Solution Overview
Problem
Current methods for monitoring gas mixture quality in the dense-phase region face challenges such as expensive and non-linear NIR methods, elaborate condensate collection setups, and inaccuracies in gas chromatograph-based systems, particularly in distinguishing C6+ fractions and determining cricondentherm accurately.
Innovation Solution
A method and system that throttles a gas sample to a representative pressure, measuring the hydrocarbon dew point, which is indicative of the cricondentherm, using a statistical method to select the pressure based on temperature-pressure relationships to achieve a pre-selected margin of error, allowing for reliable and inexpensive on-line monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If NIR spectroscopy is used for gas quality monitoring, then measurement speed is improved, but measurement precision deteriorates because it cannot distinguish between C3-C5 components and determine nitrogen concentration
Solution Approach 1:
The patent combines multiple measurement techniques (NIR spectroscopy, GC analysis, and condensate collection) into a hybrid system that leverages the speed of NIR for initial screening and the precision of GC/GC-MS for accurate component identification and quantification, particularly for C3-C5 fractions and nitrogen concentration
2Measurement precision
If condensate collection method is used, then measurement precision is improved, but device complexity increases due to elaborate setup and careful weighing requirements
Solution Approach 1:
The patent extracts only the essential measurement function from the complex condensate collection system by using pre-selected pressure and temperature conditions that naturally condense heavier components, eliminating the need for elaborate weighing setups while maintaining measurement precision through simplified condensate collection and volume measurement
3Measurement precision
If GC-based analysis is used, then measurement precision is improved, but loss of substance occurs due to NGL dropout in the sample stream
Solution Approach 1:
The patent performs preliminary heating of the gas sample before it enters the GC analyzer to prevent NGL dropout during sampling and analysis. By maintaining the sample above its dew point temperature throughout the sampling process, heavier components remain in the gas phase and are properly delivered to the GC for accurate analysis
4Adaptability or versatility
If GC-EOS method is used to determine cricondentherm, then adaptability is improved, but measurement precision deteriorates due to inherent uncertainties in equations of state
Solution Approach 1:
The patent uses measured compositional data from GC/GC-MS analysis as feedback to refine and validate the equation of state calculations for cricondentherm determination. The actual measured composition information is fed back into the EOS model to improve the accuracy of phase behavior predictions and cricondentherm calculations for specific gas mixtures
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 approach provides accurate and cost-effective monitoring of gas mixtures, ensuring reliable operation by estimating cricondentherm with a pre-selected margin of error, reducing liquid dropout and operational issues in pipelines.
Implementation Method 1
throttling a sample of the gas mixture to a representative pressure
Implementation Method 2
measuring the hydrocarbon dew point of the sample at the representative pressure, the measured hydrocarbon dew point being indicative of the cricondentherm
Data Source
AI summary
A method and system for monitoring the quality of a given gas mixture being transmitted under pressure by throttling a sample of the gas mixture to a representative pressure and measuring the hydrocarbon dew point of the sample at the representative pressure. The measured hydrocarbon dew point is indicative of the cricondentherm of the gas mixture. The representative pressure is pre-selected to provide a pre-selected margin of error between measured hydrocarbon dew points of a set of representative gas mixtures at the representative pressure and respective cricondentherms of the set of representative gas mixtures.