The Natural Gas (NG) sector is looking at the Hydrogen-enriched Natural Gas mixtures (H-NG) with growing interest. Hydrogen injections in the NG networks are expected to increase in the next years. Simultaneously, there is the requirement to constantly sample the composition and the thermodynamics properties of combustible blends. Raman spectroscopy is an intrinsic non-invasive approach for gas analysis. In addition, this technique is able to provide multiple-species analysis in a simultaneous way. An industrial-grade instrument, designed to operate directly on-site, has been developed. Its aim is to determine the NG and H-NG blends composition in an accurate and repeatable way, by referring to the OIML R 140 standard. The system is going forward in its industrialization by applying all the engineering steps useful to make it robust and easily replicable. The system laser source is a broadband multi-mode diode centered at 447nm with an optical power of 2W. The scattered radiation is collected by an appositely designed diffraction grating spectrometer and acquired by a 2D uncooled camera. The spectrometer guarantees Raman Stokes acquisition of the entire spectral region of interest without any mechanical movement. Three typical NG and one H-NG certified mixtures has been measured by placing the system in a climatic chamber. The results obtained during this validation show a high accuracy and repeatability in the overall temperature range by requiring only one calibration set carried out at room temperature. The calorific value, calculated by the measured gas mixture concentration, results within ±0.5% error in the full temperature range.
This paper introduces a novel laser-based system designed for real-time Raman spectroscopy applied to in-line combustion diagnostics. While Raman spectroscopy is a well-established technique for solid and liquid analysis, its application to gas samples is challenging due to their low density, which limits the intensity of Raman scattering. To address this issue, our system utilizes a multipass cell, strategically designed to enhance signal generation and its collection. The instrument performs calibrated analysis, providing qualitative and quantitative information about gas composition. Depending by the application, the system can work with spectra integration time ranging from 0.15 s up to 10 s. This study has demonstrated that Raman spectroscopy can be a useful tool for combustion diagnostics, as it can operate fast enough to follow the time scale of combustion phenomena.
Nowadays the Clostridium detection in milk for the dairy industry still is a challenging problem since traditional methods are time-consuming and lack specificity towards these bacteria. The use of microbiological techniques is possible but is expensive in terms of response time and requires qualified personnel. Pasteurization is ineffective against Clostridium spores which can survive the process and later revert to their vegetative form during cheese aging. The Clostridium metabolism is characterized by the production of carbon dioxide and hydrogen, which can lead to the formation of cracks and slits in the cheese altering its taste and structure. The analysis of gas production is indicative of the presence of Clostridia; therefore, it can be exploited to detect their presence. This study presents a Raman spectroscopy-based instrument for a rapid and cost-effective identification of Clostridium in milk. The methodology relies on the widely adopted Most Probable Number (MPN) method, as established by Brändle et al. (2016). However, our innovation lies in adoption of a Raman-based instrument to speed up the vial positivity detection. The instrument also enables the discrimination Clostridia infection from non-hydrogen-producing bacteria.
The detection of Clostridium in milk poses a significant challenge for the dairy industry since traditional methods are time-consuming and lack specificity towards these bacteria. Conversely, microbiological techniques are costly and demand skilled personnel. Clostridium in the form of spores can survive pasteurization and revert to their vegetative form during cheese aging. The gas-producing metabolism of Clostridium, characterized by the production of carbon dioxide and hydrogen, leads to the formation of cracks in the cheese and off-flavors. However, the analysis of gases produced in the headspace can be exploited to determine the presence of Clostridium in milk. This study aims present a Raman spectroscopy-based instrument that enables rapid and cost-effective identification of Clostridium in milk. The methodology aligns with the widely adopted most probable number (MPN) method, as established by Brändle et al. (2016), where vials are considered positive for growth after incubation. However, our innovation lies in the integration of an actual multigas sensing instrument to determine vial positivity, thereby enhancing accuracy. Notably, we emphasize the meticulous selection of vials and the optimization of headspace volume, crucial factors contributing to the heightened performance of the proposed instrument.
The combustible gas sector requires for instrumentation capable to determine the composition and the quality of the gas mixtures present in the transport and distribution networks. The gas parameters need to be monitored in a wide interval, since mixtures are found within an extremely variable range. A compact, fast and highly sensitive instrument based on Raman spectroscopy has been developed with the specific aim to operate directly on-line. This approach is intrinsically non-invasive, since it needs a laser beam passing through the gas, and multi-species sensitive, since the different components of the gas mixture are simultaneously detected. The Raman scattering is stimulated by a laser diode centered at 455 nm with multi-mode emission and 1.5 W optical power. The laser is focused on a gas cell through a window, the Raman emission is collected by a grating spectrometer and finally acquired by a 2D camera. The measured spectra are fitted with the calibration dataset acquired at room temperature to achieve the mixture composition. The system is able to determine the main components of the natural gas: methane, heavier hydrocarbons, nitrogen, carbon dioxide and hydrogen. The Heating Value (HV) is finally calculated using the ISO6976:2016 standard. Several certified gas mixtures have been tested with the instrument operated at different temperatures in the range from -20°C to 50°C, to prove the capability to operate in a wide industrial temperature range. Each measure requires less than 25 seconds, with a sample pressure of 6 bars. The calculated HV value lies in the ±0.5% error range.
Despite developments in the dairy industry, blowing defects in cheese due to Clostridium contamination continues to be a problem. Traditional microbiological detection methods used in dairy industries to detect spores are time consuming and limited in efficiency and sensitivity. Many alternative approaches of detecting butyric acid clostridia in milk still pose a major challenge for microbiologists. According to the fermentative butyric acid production, carbon dioxide and hydrogen are also produced as byproducts during fermentation. As a consequence, during the incubation of contaminated milk in a sealed container (such as a cuvette), the measurement of CO2 and H2 in the headspace can be a promising possibility for early-stage detection of the spores. A multi-gas sensor based on Raman spectroscopy was used for the measurement of CO2 and H2 concentration. The aim of this paper is to demonstrate the applicability of Raman gas analysis to the detection of multiple gas species in sealed, transparent samples for early detection of spore contamination in milk. Two different contaminant spores were used: Clostridium tyrobutyricum and Bacillus. The first one showed an increase of CO2 and H2 content within 16h of incubation. The second one showed an increase of CO2 content within 48 h of incubation. For the first time, Raman gas spectroscopy has been applied for contactless measurement of the time resolved evolution of multiple gaseous species in milk samples for spore analysis.
Soil is a precious, essentially non-renewable, resource presently endangered by human activities. The road to protection goes through knowledge: there is the need to raise the global understanding of the importance of soil. Therefore, diffuse measurement of soil properties is central to soil conservation and management. We present a device tailored to monitor the soil quality by adopting a low-cost open-source multi-sensor approach. The device measures in the field soil temperature, moisture, density and pH. Furthermore, the device has a penetrometer to obtain a depth-resolved soil hardness characterization down to 60cm from the surface. The device is controlled via Bluetooth by a custom-built Android App. The application georeferences each data and uploads the generated _les to a server for data elaboration aimed to build and populate a map with all the collected soil quality measurements. The device is equipped with a temperature/moisture sensor, a 0-5kg load cell used as weight scale for density measurements, a reflectance spectra sensor for automatic reading pH test strips and, on the bottom side, a penetrometric tip mounted on a 100kg load cell coupled with an optical time-of-flight sensor for depth-referenced penetrometer measurements. Preliminary test evidenced good correlation between in-the-field observations and traditional laboratory tests. The device is easily also by unexperienced users, allowing for applications both in agronomic and in environmental fields, ranging from educational purposes and ICT learning of soil sciences to scientific projects related to soil monitoring and awareness raising Citizen Science initiatives.
A multi gas analyzer for in line composition evaluation has been developed and optimized for the detection of fuel gas main components. The system has been designed for unmanned and remote operation on natural gas pipelines and biogas production plants as a low cost and low maintenance alternative to current industry standard gas chromatographic methods which are used to evaluate the mixture heating value as well as to detect undesired contaminants. The system does not require any consumable supply and could also be considered as a competitor of most available non-analytical techniques for the determination of heating value, which in our case can be obtained from actual gas composition through application of the relevant calculation as described by ISO 6976 norm.
A high-power, lighting grade multimode laser diode pump has been used to reduce both manufacturing and operation costs as well as power supply requirements. Sample gas is flowing in a cell rated for high pressure operation and the spectral analysis is performed by a custom design, high throughput lens based spectrometer developed for this application featuring an industrial CMOS camera as a low cost, high sensitivity and low noise focal plane array.
The use of a multimode pump operating over a wide temperature range and a non-cooled detector array are the source of several issues in the recorded spectra which have been addressed with the developement of custom image processing and fitting software routines to cope with broadened, drifting Raman spectra. This approach has been lab calibrated against the single components (such as methane, ethane, propane, n-butane, iso-butane, nitrogen, oxygen, water vapour, carbon dioxide, carbon monoxide, hydrogen) and tested with certified gas mixtures made to simulate the concentration levels commonly found during field operation at total absolute pressures ranging from 1 to 6 bar.
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