Portable Optical Spectroscopy Device for Methane Leak Detection
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Solution Overview
Problem
Current gas leak detectors are not responsive enough to detect low methane concentrations, are not selective to methane, pose explosion hazards, and require multiple devices for measurement across different concentration ranges, making them unsuitable for efficient natural gas leak surveys.
Innovation Solution
A portable optical spectroscopy device using multiple spectroscopic methods and a microcontroller to select the appropriate method for measuring methane concentrations from ambient to pure gas levels, with a low-power semiconductor laser diode and intrinsic safety features to prevent explosions, allowing for continuous and selective measurement of methane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If flame ionization detectors are used to detect gas leaks, then sensitivity to low methane concentrations is improved, but intrinsic safety deteriorates due to internal flame and explosion hazard
Solution Approach 1:
The patent replaces the mechanical/chemical combustion-based flame ionization detection system with an optical spectroscopy system using laser diodes and photodetectors. This substitution eliminates the internal flame and explosion hazard while maintaining high sensitivity to methane concentrations through optical absorption measurements at specific wavelengths.
2Measurement precision
If multiple different instruments are used to measure different concentration ranges, then measurement precision across full dynamic range is improved, but device complexity increases
Solution Approach 1:
The patent designs a universal optical spectroscopy device that can measure methane concentrations across the entire dynamic range from 1.7 ppm to 100% using a single instrument. The system employs multiple laser diodes operating at different wavelengths and multiple photodetectors configured to handle different absorption regimes, allowing one device to replace multiple specialized instruments.
Solution Approach 2:
The patent segments the measurement function across multiple optical channels within a single device. Different laser diodes target specific absorption lines of methane, and multiple photodetectors measure transmitted light at different wavelengths or positions. This segmentation allows the single device to accurately measure across the full concentration range by selecting appropriate channels based on the expected concentration level.
3Ease of operation
If conventional gas leak detectors are used, then ease of operation is maintained, but selectivity to methane deteriorates as they respond to any hydrocarbon
Solution Approach 1:
The patent applies local quality by targeting specific localized absorption features of methane molecules at precise wavelengths. The laser diodes are tuned to excite specific rotational-vibrational transitions of methane, and the photodetectors measure absorption at these localized spectral regions. This wavelength-specific measurement provides high selectivity to methane while maintaining ease of operation, as the device automatically distinguishes methane from other hydrocarbons based on their unique spectral fingerprints.
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 device provides rapid, continuous, and selective measurement of methane concentrations from 1.7 ppm to 100% with intrinsic safety, replacing multiple instruments and preventing false alarms, suitable for rapid walking area surveys and ATEX compliance.
Implementation Method 1
A portable optical spectroscopy device uses two or more spectroscopic methods to cover the full measurement dynamic range from ambient methane levels (approximately 1.7 ppm) to pure gas
Implementation Method 2
The optical absorption is preferably at a wavelength corresponding to a methane absorption line between 1,630 and 1,700 nm
Data Source
AI summary
A portable optical spectroscopy device is disclosed for analyzing gas samples and/or for measurement of species concentration, number density, or column density. The device includes a measuring chamber with the gas sample to be analyzed, a light source with at least one laser diode for emitting a laser beam along a light path running through the measuring chamber at least in certain regions, means for modulating the wavelength of the light beam emitted by the light source, and an optical detector device having a first optical detector and at least one second optical detector. At least a part of the light emitted by the laser diode is detected after the light has passed through the measuring chamber m-times, and at least a part of the light emitted by the laser diode is detected with the at least one second optical detector after the light has passed through the measuring chamber n-times, where n>m applies.