Étude du traitement des siloxanes par adsorption sur matériaux poreux (application au traitement des biogaz)

Les biogaz sont des mélanges à forte teneur en méthane utilisés dans la production de chaleur ou d électricité. Ils contiennent des quantités plus ou moins importantes des siloxanes qui sont interdits pour de nombreuses utilisations du biogaz. La possibilité d élimination des siloxanes par adsorption est étudiée. Une étude en réacteurs statiques permet d évaluer les capacités d adsorption des charbons actifs, de zéolithes et du gel de silice. L influence sur les capacités de traitement des siloxanes, de la présence de CH4, de CO2, de l humidité, et d autres composés organiques volatils dans la matrice gazeuse, est étudiée. Des bonnes capacités d adsorption de certains adsorbants sont retrouvées. Dans les conditions d adsorption les plus défavorables on obtient une diminution de 20 % sur les capacités d adsorption. Les capacités de traitement restent modestes. L influence des conditions opératoires du procédé est étudiée dans le but d augmenter les capacités de traitement et réduire la quantité d adsorbant. Les résultats, nous ont permis de définir, valider et dimensionner un système de traitement à échelle réduite. Le procédé envisagé consiste en une adsorption sur tissu de carbone activé, alternant avec des phases de régénération thermique. Une unité pilote a permis de réaliser et d évaluer le vieillissement du procédé. L ensemble de ce travaille laisse entrevoir des possibilités d applications industrielles du procédé, même si une phase d essai sur site en conditions réelle est encore nécessaireBiogases have strong content of methane used in the production of heat or electricity. They contain more or less important quantities of siloxanes, which are forbidden for numerous uses of biogases. The possibility of siloxanes elimination by adsorption process is studied. The study in batch reactors allows us to evaluate the adsorption capacities of different materials as activated carbons cloths and grains, zeolites and silica gel. The influence on the treatment capacities of siloxanes under the presence of CH4, CO2, humidity, and other volatile organic compounds is studied. Good adsorption capacities for some adsorbents were found. For the most disadvantageous conditions of adsorption, a reduction of 20 % on the adsorption capacities has been found. The adsorption capacity remains modest. The influence of the operational conditions of the process is studied in order to improve the treatment capacities and to reduce the quantity of the adsorbent used. The results allowed us to define, validate and design a reduced scale system in the treatment of siloxanes. The process consists of an adsorption into activated carbon cloth, alternating with thermal regeneration by Joule effect. A pilo t plant allowed us to accomplish and evaluate the aging of the process. All this work allows us to see the possibilities of industrial applications of the process, even if a trial stage on site in real conditions is still necessaryNANTES-BU Sciences (441092104) / SudocSudocFranceF

Understanding the influence of media geometry on the degradation of acrylonitrile: Experimental and CFD analysis

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Influence of operating parameters on the single-pass photocatalytic removal efficiency of acrylonitrile

International audiencePhotocatalytic oxidation (PCO) is an advanced air cleaning technology that is used as a means to improve air quality in indoor environments and could also potentially be used in hospital operating rooms (ORs). However, when it comes to the feasibility of using PCO to remove VOCs, most studies have been on those that are commonly found in indoor environments like homes and schools. There are little or no studies on other indoor environments like hospitals. Therefore in this work, acrylonitrile, one of the hazardous compounds found in surgical smoke (a source of pollution in the OR) was chosen as a representative compound to evaluate the performance of a photocatalytic system in an OR. The experiments were performed in a 420-L multi-pass laboratory reactor. The performance of the system was based on the influence that three operating parameters (air velocity, light intensity and initial concentration) would have on the single-pass removal efficiency (SPRE). A mathematical model was used to enable the calculation of the SPRE from the experimental degradation profile. The influence of the operating parameters on the degradation of acrylonitrile as well as the possible inter-mediates formed and mineralization rates are discussed

Influence of operating parameters on the single-pass photocatalytic removal efficiency of acrylonitrile

International audiencePhotocatalytic oxidation (PCO) is an advanced air cleaning technology that is used as a means to improve air quality in indoor environments and could also potentially be used in hospital operating rooms (ORs). However, when it comes to the feasibility of using PCO to remove VOCs, most studies have been on those that are commonly found in indoor environments like homes and schools. There are little or no studies on other indoor environments like hospitals. Therefore in this work, acrylonitrile, one of the hazardous compounds found in surgical smoke (a source of pollution in the OR) was chosen as a representative compound to evaluate the performance of a photocatalytic system in an OR. The experiments were performed in a 420-L multi-pass laboratory reactor. The performance of the system was based on the influence that three operating parameters (air velocity, light intensity and initial concentration) would have on the single-pass removal efficiency (SPRE). A mathematical model was used to enable the calculation of the SPRE from the experimental degradation profile. The influence of the operating parameters on the degradation of acrylonitrile as well as the possible inter-mediates formed and mineralization rates are discussed

Influence des paramètres opératoires sur la dégradation photocatalytique d'un gaz anesthésiant : l'isoflurane

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Influence of environmental parameters on the photocatalytic oxidation efficiency of acrylonitrile and isoflurane; two operating room pollutants

International audienceIn hospitals, operating rooms (ORs) are very demanding in terms of the indoor air quality (IAQ) and require systems that minimize the concentrations of pollutants (microorganisms, chemical and particulate matter). Air treatment devices that use photocatalytic oxidation (PCO) could potentially be used in the OR to improve IAQ. In this work, the fate of two OR pollutants acrylonitrile (chemical found in surgical smoke) and isoflurane (an-esthetic gas) when they go through a PCO device was investigated. The experiments were conducted in a laboratory closed loop multi-pass reactor. A mathematical model was utilized to enable the calculation of one indicator (single-pass removal efficiency) for acrylonitrile and two indicators (induction period and single-pass removal efficiency) for isoflurane. The degradation efficiency was then accessed by studying the influence of environmental parameters on these indicators. The parameters that were studied are the relative humidity, presence of co-pollutants and presence of particles. The parameters were observed to have similar effects on the degradation of both compounds. Increasing relative humidity inhibited the degradation probably due to competitive adsorption. The presence of co-pollutants like nitrous oxide and acetic acid caused a possible competition for adsorption unto active sites thus decreased the degradation efficiency of acrylonitrile and isoflurane. The increase in the concentration of the co-pollutants enhances the competitive effect and further decreases the degradation efficiency of the target pollutants. Finally the presence of particles on the photocatalytic media could block active sites thereby inhibiting the degradation of acrylonitrile and isoflurane

INFLUENCE OF ENVIRONMENTAL PARAMETERS ON PCO REMOVAL EFFICIENCY OF TWO OPERATING ROOM POLLUANTS

International audienceThe hospital environment is a complex one compared to others like residential and commercial buildings. The complexity lies in the fact that there are several zones where specific activities are performed and consequently, occupants (hospitals workers, patients, etc) are exposed to a wide variety of chemical pollutants (Leung and Chan, 2006) (Gangneux et al, 2017). Additionally, these different zones have different indoor air quality (IAQ) requirements. Operating rooms (ORs) are one of the most demanding zones in terms of IAQ and thus require systems that minimize the concentrations of pollutants (bioaerosols, chemical pollutants and particulate matter). Air treatment devices that use photocatalytic oxidation (PCO) could potentially be used in the OR to improve IAQ. In this work, the fate of two OR pollutants acrylonitrile (chemical found in surgical smoke) and isoflurane (anesthetic gas) was investigated. For the first time, experiments were conducted in a laboratory closed loop multi-pass reactor to investigate the effect of environmental parameters on the PCO removal efficiency of isoflurane and acrylonitrile. The study looks at the influence of three environmental parameters; relative humidity, presence of co-pollutants and presence of particles on their degradation under relevant conditions to actual applications. The closed loop reactor used in this work allows the study of air pollutants at low concentrations and has also been recently modeled (Dumont and Héquet, 2017) (Héquet et al, 2017). This reactor permits a better representation of PCO systems functioning in dynamic mode and is realistic regarding air treatment systems working as standalone devices or implanted in HVAC systems. A mathematical model was utilized to enable the calculation of one indicator (single-pass removal efficiency) for acrylonitrile and two indicators (induction period and single-pass removal efficiency) for isoflurane. The degradation efficiency was then accessed by studying the influence of environmental parameters on these indicators. Figure 1 presents an example of the degradation profile of acrylonitrile and the determination of the single pass removal efficiency (α) whilst Figure 2 shows an example of the degradation profile of isoflurane and the determination of the single pass removal efficiency (α) and the induction period ( i)

Acrylonitrile photocatalytic degradation : an experimental and CFD study to understand the influence of media geometry on the process efficiency

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Photocatalytic oxidation of isoflurane, an anesthetic gas: The influence of operating parameters

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