Multiple contaminants natural gas analyser
Inventors
HAYDT, David D. • Frish, Michael B. • Chen, Shin-Juh • AUBUT, Nicholas F.
Assignees
Galvanic Applied Sciences Inc • Physical Sciences Inc
Publication Number
US-11293862-B2
Publication Date
2022-04-05
Expiration Date
2041-03-10
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Abstract
Systems and method for analysing contaminants of a gas sample of natural gas are provided. An interrogation light beam propagates into a chamber of a multipass gas cell receiving the gas sample. The interrogation light beam has a wavelength controlled to alternately correspond to an absorption wavelength of H2S and an absorption wavelength of an additional gas contaminant. The additional gas contaminant may for example be CO2 or H2O. In some implementation, a single laser emitter may be used to generate the interrogation light beam at the H2S and CO2 wavelengths. In some implementations, two different laser emitters may be used to generate the interrogation light beam at the H2S and H2O wavelengths. A WMS detection scheme may be used.
Core Innovation
The invention provides systems and methods for analysing multiple contaminants in a natural gas sample using absorption spectroscopy in a single device. Specifically, it enables detection and measurement of different gas species, such as hydrogen sulfide (H2S), carbon dioxide (CO2), and water vapor (H2O), by alternately tuning an interrogation light beam to their respective absorption wavelengths. This approach leverages a multipass gas cell and photodetector configuration, where the sample is probed with laser light at selected wavelengths and the absorption is measured to deduce the concentration of each contaminant.
Conventionally, measurement of different natural gas contaminants is performed using separate analysers employing distinct techniques, limiting efficiency and integration. The described system addresses this by using either a single spectrally tunable laser emitter or multiple laser emitters, and an optical, multipass cell through which the gas is passed. By coordinating the emitted light wavelength with absorption features of each target contaminant and detecting changes in light intensity, the system sequentially determines concentrations of different analytes within the same apparatus and sample.
The system further utilizes control signals to modulate the laser(s) for wavelength and intensity, optionally employing wavelength modulation spectroscopy (WMS) for enhanced sensitivity. Absorption lines, such as 1574.55 nm for H2S, 1574.40 nm for CO2, and 1486.71 nm for H2O, are specifically highlighted as effective operational points, with the device optimized to maximize detection sensitivity for H2S and accommodating CO2 and H2O accordingly through selection of appropriate absorption features.
Claims Coverage
The patent claims cover four main inventive features that collectively define the invention’s scope for analysing multiple contaminants in natural gas.
Laser module with multiple emitters and output optical coupler
A laser module comprising: - A first laser emitter operable within a spectral range encompassing both a selected H2S absorption wavelength and a selected CO2 absorption wavelength. - A second laser emitter operable within a spectral range encompassing a selected H2O absorption wavelength. - An output optical coupler optically coupled to both emitters and configured to output an interrogation light beam. The system allows alternate emission of light at the respective absorption wavelengths for the detection of H2S, CO2, and H2O.
Controller-driven sequential output of interrogation wavelengths
A controller configured to send control signals to the laser module, operating the emitters such that the interrogation light beam alternately corresponds to: - The H2S absorption wavelength from the first emitter - The CO2 absorption wavelength from the first emitter - The H2O absorption wavelength from the second emitter This enables automatic sequential measurement of different gas contaminants using the same gas sample and cell.
Multipass gas cell and photodetector configuration
A multipass gas cell defining a chamber that receives the gas sample, with optical input for the interrogation light beam and optical output for the beam after multiple across-chamber passes. A photodetector operatively connected to the gas cell output to receive the beam after absorption events. This increases pathlength for improved sensitivity and enables detection based on intensity reductions at selected wavelengths.
Spectrally tunable or dual-laser gas analyser for multiple contaminants
Alternative claims cover a system with either: - A single spectrally tunable laser emitter, operable to emit at both a selected H2S absorption wavelength and an additional contaminant (e.g., CO2), adjusted via controller signals for alternating measurements. - Or two laser emitters, each set to a fixed or optimally tunable absorption line for H2S and another contaminant (e.g., H2O), with controller-driven alternate operation. Both configurations are paired with a multipass cell and photodetector.
Collectively, these features provide a unified analyser device and method for sequential or alternating measurement of multiple contaminants (H2S, CO2, H2O) in natural gas using absorption spectroscopy, with either a spectrally tunable laser or multiple emitters, and incorporating a multipass gas cell for enhanced sensitivity.
Stated Advantages
Enables measurement of multiple natural gas contaminants using a single analyser and gas cell.
Allows sequential and alternating detection of different gas species (H2S, CO2, H2O) in the same sample.
Provides increased sensitivity for detection of low concentration analytes using multipass absorption spectroscopy and wavelength selection.
Documented Applications
Analysis of contaminants in natural gas, specifically monitoring H2S, CO2, and H2O concentrations.
Measurement of contaminant concentrations at custody transfer points or at various points in the natural gas value chain.
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