Trace Gas Analysis via GC-Tunable Diode Laser Spectrometry
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Solution Overview
Problem
Conventional absorption spectroscopy is ineffective for measuring trace components in complex gas mixtures due to overlapping absorption features from multiple compounds, which is common in petrochemical plant vent gases.
Innovation Solution
The method involves using gas chromatography to separate and concentrate components of a gas mixture, followed by absorption spectroscopy with a tunable diode laser to accurately measure trace gas concentrations by isolating the absorption spectrum of the target component from overlapping spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If absorption spectroscopy is used to measure trace components in complex gas mixtures, then measurement capability is provided, but measurement precision deteriorates due to overlapping absorption features from multiple compounds
Solution Approach 1:
The patent segments the complex gas mixture into individual components using gas chromatography separation before absorption spectroscopy measurement. The chromatography column physically separates different gas components based on their retention times, so that only the target component is measured at a specific time point, eliminating overlapping absorption features from other components.
Solution Approach 2:
The patent performs preliminary separation of the gas mixture using gas chromatography before the actual absorption spectroscopy measurement. The system pre-concentrates and isolates the target component in the sample cell prior to measurement, ensuring that the absorption spectrum measured belongs to a single component rather than a mixture of multiple components.
2Measurement precision
If gas chromatography is used to separate and concentrate components, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent merges the gas chromatography separation system with the absorption spectroscopy measurement system into a single integrated instrument. The chromatography column, sample cell, and spectrometer are combined in one device, allowing the benefits of both separation and spectroscopy without requiring two separate instruments, thus reducing overall system complexity.
Solution Approach 2:
The patent creates a multi-functional device that performs both gas separation (chromatography) and optical measurement (absorption spectroscopy) within a single instrument. The same device can analyze multiple gas components by changing the target component being measured, providing universal capability for trace gas analysis in complex 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 allows for precise measurement of trace components in complex gas mixtures by separating and concentrating components using gas chromatography and employing a tunable diode laser absorption spectrometer to isolate and quantify the target component's absorption spectrum, overcoming the limitations of overlapping spectral features.
Implementation Method 1
A first sample of a gas mixture containing a component is injected into a first gas chromatography column through which a carrier gas flows. The component is transported by the carrier gas through the first gas chromatography column and elutes from the first gas chromatography column at a known elution time.
Implementation Method 2
The carrier gas and the component eluting from the first gas chromatography column are supplied into a sample cell of an absorption spectrometer at the elution time. A light beam is passed through the sample cell, and an absorption of the light beam in the sample cell is measured.
Implementation Method 3
absorption spectroscopy with a tunable diode laser to accurately measure trace gas concentrations by isolating the absorption spectrum of the target component from overlapping spectra
Data Source
AI summary
Low concentrations of complex gas mixture components may be detected and quantified using a gas-chromatograph to separate a gas mixture prior to analysis of one or more eluting components using an absorption spectrometer. Substantial reductions in analytical system complexity and improvements in reliability are achieved compared with other commonly used methods for analyzing such complex mixtures.