Mid-IR Hydrocarbon Measurement for Overlapping Absorption Spectra
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Solution Overview
Problem
Existing methods struggle to accurately measure concentrations of low molecular weight hydrocarbons (C1 to C4 alkanes) in gas mixtures due to overlapping absorption spectra, making it difficult to distinguish between different hydrocarbons using mid-infrared radiation.
Innovation Solution
A method involving the use of infrared radiation at specific wavelengths where each hydrocarbon has a unique absorption coefficient at least 5 times greater than others, combined with a computer processor to calculate concentrations by subtracting predicted absorbances, and an apparatus with a gas-permeable membrane for immersion in liquids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If measurements are made at a large number of wavelengths with an infrared spectrometer, then the ability to distinguish between different hydrocarbons improves, but the device complexity and measurement time increase significantly
Solution Approach 1:
The patent divides the infrared spectrum into multiple discrete wavelength bands, with each band targeted by a separate detector. This segmentation allows the system to focus on specific absorption regions for different hydrocarbons (C1-C4) without requiring a full spectrometer, thereby reducing device complexity while maintaining the ability to distinguish between hydrocarbon types through multi-band absorption measurement
Solution Approach 2:
The patent transitions from a single-wavelength measurement approach to a multi-wavelength approach by adding spectral dimensionality. Instead of measuring at one wavelength, the system measures absorbance across multiple discrete wavelength bands simultaneously, creating a spectral fingerprint that enables hydrocarbon differentiation without the complexity of full spectral analysis
2Measurement precision
If a gas chromatograph is used to separate and analyze hydrocarbon gases, then the measurement precision improves, but the device complexity and analysis time increase
Solution Approach 1:
The patent replaces the mechanical separation system of a gas chromatograph with an optical detection system. Instead of physically separating hydrocarbons through chromatographic columns and moving parts, the system uses infrared absorption spectroscopy at multiple wavelength bands to directly identify and quantify different hydrocarbons based on their unique absorption spectra, eliminating the need for complex mechanical separation apparatus
Solution Approach 2:
The patent introduces an intermediary computational layer that processes multi-band absorbance measurements to derive hydrocarbon concentrations. Rather than relying on physical separation, the system uses mathematical algorithms to deconvolve the overlapping absorption spectra of different hydrocarbons, acting as a computational intermediary that translates optical measurements into concentration data
3Ease of operation
If measurements are made at wavelengths where hydrocarbons have similar absorption coefficients, then the ease of operation improves, but the measurement precision deteriorates due to inability to distinguish between hydrocarbons
Solution Approach 1:
The patent changes the measurement parameters by selecting specific wavelength bands where different hydrocarbons exhibit distinct absorption characteristics. Instead of using a single wavelength or broad spectrum, the system carefully chooses multiple discrete wavelength bands that maximize the spectral differences between C1-C4 hydrocarbons, thereby improving distinguishability while maintaining operational simplicity through fixed-band measurement
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
Enables precise measurement of individual hydrocarbon concentrations in gas and liquid samples by distinguishing between overlapping spectra, facilitating applications in mud logging, pipeline leakage detection, and other environmental gas monitoring.
Implementation Method 1
an internal space enclosed within the apparatus is separated from liquid outside the apparatus by a gas-permeable membrane. Such a membrane allows gas to enter a chamber within the apparatus
Implementation Method 2
Measurement of absorbance of mid-infrared (typically 2μm to 20μm wavelength) radiation is a known method for measuring gases
Implementation Method 3
Measurement of the concentration of an individual gas in a gas mixture can be made by measurement of the absorption of infrared radiation at a wavelength at which there is absorption by the gas of interest
Data Source
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AI summary
Concentrations of individual hydrocarbons in a gas mixture are determined by measuring absorbance of mid-infrared radiation at specific wavelengths. Computation enables determination of concentrations of individual hydrocarbons despite overlaps of absorption bands.