High pressure flow cell for spectral analyses and spectral range conversion
Inventors
Assignees
University of Alaska Fairbanks
Publication Number
US-11635368-B2
Publication Date
2023-04-25
Expiration Date
2040-02-25
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Abstract
A flow cell can comprise a high-pressure, fluidic, flow-through housing that encloses and auto-aligns a heavy-walled, internally reflective low-cost glass capillary for concentrating and amplifying laser-excited spectra. The containment housing that encloses the capillaries can optionally sustain operational pressures of at least 10,000 psi. The pressure housing can be fitted with transparent optical windows that can accommodate laser-safe injection and spectra collection. The flow-cell design can adaptably accommodate different optical sampling configurations such as transmissive (forward scattering), reflective (backward scattering), or multipass, combined scattering. The flow cell size is scalable (lengthwise) to accommodate different applications or installations such as benchtop (lab), permanent (industrial), and portable (field). With new, miniaturized spectrometers, the flow cell can optionally be configured for transport as a real-time, high-sensitivity gas-analysis sensor aboard compact aerial or otherwise mobile systems (e.g., drones) for remote or hazardous applications.
Core Innovation
The invention describes a flow cell for spectral analysis that includes a high-pressure, fluidic, flow-through housing enclosing a heavy-walled, internally reflective glass capillary waveguide. The flow cell auto-aligns the capillary and employs transparent optical windows at each end to allow laser-safe injection and spectra collection. The capillary waveguide is designed to remain optically straight when supported only by vertical forces at its ends and may be coated internally with reflective materials such as silver, gold, aluminum, or dielectric layers to enhance light interaction.
This flow cell overcomes problems of conventional designs, which typically use thin-walled, flexible glass capillaries that require complex support systems, specialized engineering, proprietary parts, and are often fragile, costly, and difficult to scale or maintain. Unlike these conventional systems, the disclosed invention uses a rigid, heavy-walled capillary that does not require tensioning for alignment, improves robustness, supports high pressure (at least 10,000 psi), and is compatible with modular fittings for easy assembly and maintenance.
The invention also enables multiple optical sampling configurations—including transmissive (forward scattering), reflective (backward scattering), and multipass combined scattering—for spectroscopic applications such as Raman and absorption spectroscopy. Its scalable design accommodates various installations, from benchtop laboratory setups to portable field or mobile units, and the flow cell functions as a turn-key, bolt-on solution for spectroscopic systems, offering flexibility and improved sensitivity for real-time gas and liquid analysis.
Claims Coverage
The patent contains three independent claims, each capturing distinct inventive features related to a high-pressure spectral analysis flow cell, a spectroscopy system, and a spectroscopic analysis method.
High-pressure flow cell with heavy-walled, auto-aligned capillary waveguide
The flow cell includes: - An enclosure tube with opposed ends. - A capillary waveguide extending longitudinally through the enclosure, with an outer surface, inner bore, opposing ends, and an inlet and outlet, wherein the capillary is rigid enough to remain optically straight when only vertically supported at its ends. - First and second compression fitting assemblies at each end of the enclosure tube, each with: - An alignment fitting with a tapered interior bore to receive an O-ring seal, coupled by a compression seal. - A compression fitting joined to the alignment fitting by another compression seal, receiving a respective window. - A nut threadedly engaged to provide biasing force against the window. - A first O-ring compressed between the fitting and window. - A compression sleeve within the alignment fitting, providing window biasing. - A second O-ring between the compression sleeve and alignment fitting.
Spectroscopy system comprising the flow cell, laser, and spectrometer
The system consists of: - The flow cell as detailed above, with its capillary waveguide, compression fitting assemblies, and windows. - A laser configured to provide a beam into one end of the capillary waveguide. - A spectrometer configured to receive a portion of the beam from the second end of the capillary waveguide. - Each compression fitting assembly includes the alignment fitting (with tapered bore and compression seals), compression fitting, threaded nut for biasing the window, O-rings, and compression sleeve, as previously described.
Method for spectroscopic analysis of flowing gases using the flow cell system
The method includes the steps of: 1. Providing a flow of gas through a spectroscopy system that includes the described flow cell with its specific features and the spectroscopic components (laser and spectrometer). 2. Passing the laser beam through the inner bore of the capillary waveguide. 3. Receiving at least a portion of the beam at the spectrometer for analysis. - Each compression fitting assembly operates as detailed above, providing alignment, sealing, and window placement via the described components.
The inventive features encompass a robust flow cell design with auto-aligned, heavy-walled capillary waveguide, specialized high-pressure compression assemblies, and the integration of such flow cells into complete spectroscopy systems and methods.
Stated Advantages
The flow cell provides simple yet precise assembly, significantly reducing production, maintenance, and repair time compared to specially fabricated alternatives, resulting in considerable economic savings.
The design lowers costs and offers modular construction with off-the-shelf components, enabling cost-effective manufacturing and maintenance.
Heavy-walled capillary waveguides are rigid, durable, optically straight, and reliable, eliminating the need for specialized supports or tensioning.
The auto-alignment and sealing mechanisms simplify integration and ensure reliable, leak-free performance under high pressure.
Internally reflective coatings enhance laser-fluid interaction, improving sensitivity and spectroscopic signal collection, especially for weak gas-phase Raman signals.
The flow cell accommodates various optical measurement configurations, increasing flexibility for spectral analysis.
Capillaries can be easily removed and replaced for cleaning, maintenance, or refurbishment, providing robust operational convenience.
The flow cell enables fast fluid analyses with high temporal resolution, facilitating near real-time measurement of compositional changes.
Direct integration compatibility with a wide range of optics systems and adaptability to several applications (benchtop, industrial, portable, mobile).
Single crystal sapphire windows enhance durability, pressure resistance, laser-safety, and provide distinct spectra with minimal overlap with target gases.
Documented Applications
Spectral analysis of flowing gases or liquids during experimental or operational conditions in laboratory, industrial, portable, and field installations.
Real-time, high-sensitivity gas-analysis sensors, including portable, hand-held instruments or integration aboard mobile systems such as drones for remote or hazardous environments.
Turn-key, bolt-on spectroscopic detection and quantification of short-lived or episodic gas concentrations in processes such as coal gasification, fuel-cell operations, steam-turbine gas bearings, and nuclear power plants.
Continuous, near real-time, multi-component gas-stream analysis for mixtures of gases (e.g., H2, CH4, CO, CO2, N2, O2, and others) without offline sample preparation.
Functioning as a spectral-conversion device to induce predictable spectral shifts (e.g., via Raman effect) by filling the flow cell with a selected fluid and transmitting laser light.
Spectroscopic liquid analysis as a long-path flow cell, with or without the capillary waveguide core.
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