Accumulators for the Capture of Heavy Metals in Thermal Conversion Systems

International audienceA clay ceramic with organic additives (biomass and biochar) was investigated for the development of highly porous accumulators to capture heavy metals in thermal conversion systems. The structure was characterized using X-ray pair distribution function analysis, differential scanning calorimetry, and scanning electron microscopy. It was found that the organic additives transformed into porosity during firing. The morphology of the pores also corresponded to the morphology of the organic additives. Hence, the clay ceramic with a 15-wt% addition of biochar had a porosity of 46 vol% with 20-μm interconnected pores after firing. The resulting accumulator was found to capture cadmium (a model for heavy metals with high volatility) via condensation of the cadmium vapor as 2-μm beads in the pores. The cadmium capture efficiency reached up to 57% using a 15-wt% addition of biochar. Furthermore, cadmium was captured at higher temperatures than the condensation temperature in the atmosphere. This means that heavy metals may be captured before they condense in fly ash to promote the recycling of this material

Ceramic Water Filters for the Removal of Bacterial, Chemical, and Viral Contaminants

International audienceIn this study, the combination of capture mechanisms in ceramic water filters (doped with hydroxyapatite and alumina) was considered for the removal of contaminants from drinking water. It was found that hydroxyapatite and alumina were conserved during the firing process of the ceramic water filters up to 950°C. The nanopores resulting from the conservation of the additives increased the specific surface area of the ceramic water filters from 3.7 to 21.0m2·g−1. On the other hand, the microscopic pores associated with the processing of the ceramic water filters (i.e., pressing and drying) and the combustion of the sawdust reduced the filtration time from 24 to 4 h. The efficiency of the resulting filters in removing bacterial, chemical, and viral contaminants from water was investigated using E. coli, fluoride, and MS2 as model contaminants. The contaminants were found to be captured from water by trapping in the pores, substitution in the hydroxyapatite, and adsorption on the surface of alumina. Hence, the ceramic water filters incorporating hydroxyapatite and alumina combined the different capture mechanisms. They had an efficiency of 99.998%, 99.970%, and 99.450% in the removal of bacterial, chemical, and viral contaminants, corresponding to log reduction values (LRVs) of 4.69, 3.47, and 2.26, respectively

Study of microstructural transformations of clay/biomass mixtures on the firing and relations with the mechanical and thermal properties

La valorisation de résidus agricoles, industriels ou urbains se révèle, à mesure des recherches et des avancées, un recours pertinent aux défis s’imposant à l’industrie de la terre cuite et au domaine de l’habitat. L’incorporation de résidus agricoles à travers des produits conventionnels a permis au long de cette étude une économie de ressource argileuse et d’énergie, tout en améliorant les performances mécaniques et thermiques à la base des matériaux de construction. Des matières végétales ajoutées au mélange argileux de fabrication entrainent une formation de porosité, durant la cuisson des produits, selon la libération d’espaces occupés par les particules, à des températures allant de 200 à 400°C. Les pores en formation adoptent alors les formes et les tailles de particules constitutives, en procurant une maitrise de la microstructure et des propriétés usuelles de la terre cuite. Les résidus agricoles à fines particules se décomposent au sein de la matrice argileuse et procurent, en réduisant la taille moyenne des pores, une amélioration des performances mécaniques de près de 40%. Les matières végétales à particules fibreuses suscitent en revanche une augmentation de l’anisotropie originelle de la microstructure et une amélioration notable de 40% des performances thermiques. La combustion de la matière organique assure, en prime, un apport énergétique au procédé de cuisson s’élevant à 35% des besoins en combustible et compensant un coût d’achat éventuel. L’incorporation de matières végétales au sein des produits de terre cuite apparait comme un succès sur le plan économique, environnemental et technique en raison d’une valorisation matière, entrainant une amélioration des performances usuelles, et d’une valorisation énergétique, accordant une réduction des consommations en gaz et des émissions en dioxyde de carbone.Waste and biomass valorization appears, on a way of research and advances, as a relevant answer in the challenge offered to the clay bricks industry and housing field. Incorporations of agricultural wastes into clayey ceramic bodies accorded, along those investigations, raw material and energy savings, since improving the mechanical and thermal properties on the basis of every building material. Biomass incorporations amongst argillaceous mixtures induce a porosity formation through the firing process under a release, on a range of temperatures going from 200 to 400°C, of the material spaces previously filled by the organic particles. The porous cavities assume the sizes as well as shapes of the biomass particles and provide a microstructure control affording a functional properties command. The agricultural wastes including thin particles fade out into the clayey bodies and provide, through a median pore size reduction, an improvement of the mechanical strength up to 40%. Crops residues showing fibrous particles induce on the other hand an increase of microstructure and porous network anisotropy, leading to a tremendous improvement of nearly 40% in the insulation behavior. The biomass combustion provides a calorific contribution as well, to the industrial process of firing, surrounding 35% of the usual fuel requirements and supplies an eventual cost of agricultural wastes. Biomass incorporation into clayey ceramic appears as a success on economical, environmental and technical terms, according to the material purpose offering an improvement of the functional performances, and energy purpose assuming a diminution of gas consumptions or a reduction of carbon dioxide release

Etude des transformations microstructurales de mélanges argile/biomasse lors de la cuisson et relations avec les propriétés mécaniques et thermiques

Waste and biomass valorization appears, on a way of research and advances, as a relevant answer in the challenge offered to the clay bricks industry and housing field. Incorporations of agricultural wastes into clayey ceramic bodies accorded, along those investigations, raw material and energy savings, since improving the mechanical and thermal properties on the basis of every building material. Biomass incorporations amongst argillaceous mixtures induce a porosity formation through the firing process under a release, on a range of temperatures going from 200 to 400°C, of the material spaces previously filled by the organic particles. The porous cavities assume the sizes as well as shapes of the biomass particles and provide a microstructure control affording a functional properties command. The agricultural wastes including thin particles fade out into the clayey bodies and provide, through a median pore size reduction, an improvement of the mechanical strength up to 40%. Crops residues showing fibrous particles induce on the other hand an increase of microstructure and porous network anisotropy, leading to a tremendous improvement of nearly 40% in the insulation behavior. The biomass combustion provides a calorific contribution as well, to the industrial process of firing, surrounding 35% of the usual fuel requirements and supplies an eventual cost of agricultural wastes. Biomass incorporation into clayey ceramic appears as a success on economical, environmental and technical terms, according to the material purpose offering an improvement of the functional performances, and energy purpose assuming a diminution of gas consumptions or a reduction of carbon dioxide release.La valorisation de résidus agricoles, industriels ou urbains se révèle, à mesure des recherches et des avancées, un recours pertinent aux défis s’imposant à l’industrie de la terre cuite et au domaine de l’habitat. L’incorporation de résidus agricoles à travers des produits conventionnels a permis au long de cette étude une économie de ressource argileuse et d’énergie, tout en améliorant les performances mécaniques et thermiques à la base des matériaux de construction. Des matières végétales ajoutées au mélange argileux de fabrication entrainent une formation de porosité, durant la cuisson des produits, selon la libération d’espaces occupés par les particules, à des températures allant de 200 à 400°C. Les pores en formation adoptent alors les formes et les tailles de particules constitutives, en procurant une maitrise de la microstructure et des propriétés usuelles de la terre cuite. Les résidus agricoles à fines particules se décomposent au sein de la matrice argileuse et procurent, en réduisant la taille moyenne des pores, une amélioration des performances mécaniques de près de 40%. Les matières végétales à particules fibreuses suscitent en revanche une augmentation de l’anisotropie originelle de la microstructure et une amélioration notable de 40% des performances thermiques. La combustion de la matière organique assure, en prime, un apport énergétique au procédé de cuisson s’élevant à 35% des besoins en combustible et compensant un coût d’achat éventuel. L’incorporation de matières végétales au sein des produits de terre cuite apparait comme un succès sur le plan économique, environnemental et technique en raison d’une valorisation matière, entrainant une amélioration des performances usuelles, et d’une valorisation énergétique, accordant une réduction des consommations en gaz et des émissions en dioxyde de carbone

The impact of the particle size distribution of organic additives on the microstructure of a clay ceramic and its thermal and mechanical properties

International audienceIn this study, the structure-property relationships of a clay ceramic with calibrated particles (10 or 50μm) of polymethyl methacrylate (PMMA) were investigated to improve both the thermal and mechanical properties of fired clay bricks incorporating organic wastes. The structure was characterized using differential thermal, thermomechanical, and computed tomography analysis. It was found that the addition of 10- or 50–μm particles of PMMA resulted in a same 11% decrease of the thermal conductivity during the extrusion process. The Young’s modulus also increased by 23% during the extrusion process with the addition of 50–μm particles. However, the addition of 10–μm particles resulted in a greater increase of the Young’s modulus by 34%. The calibrated particles of PMMA were then found to transform into porosity during firing of the clay ceramic. Typically, the pore size of the clay ceramic corresponded to the particle size of the calibrated particles of PMMA. The improvement of the thermal and mechanical properties that was obtained during the extrusion process was conserved in the form of porosity with a reduction of the median pore size after the firing process. Hence, the current results indicate that the thermal and mechanical properties of fired clay bricks can be improved at the same time using a wide range of organic wastes if the organic wastes are subjected to grinding prior to incorporation in the mixture. They also suggest that organic wastes can reduce the environmental impact of fired clay bricks with an energetic contribution of 73.8%

The impact of the particle size distribution of organic additives on the microstructure of a clay ceramic and its thermal and mechanical properties

International audienceIn this study, the structure-property relationships of a clay ceramic with calibrated particles (10 or 50μm) of polymethyl methacrylate (PMMA) were investigated to improve both the thermal and mechanical properties of fired clay bricks incorporating organic wastes. The structure was characterized using differential thermal, thermomechanical, and computed tomography analysis. It was found that the addition of 10- or 50–μm particles of PMMA resulted in a same 11% decrease of the thermal conductivity during the extrusion process. The Young’s modulus also increased by 23% during the extrusion process with the addition of 50–μm particles. However, the addition of 10–μm particles resulted in a greater increase of the Young’s modulus by 34%. The calibrated particles of PMMA were then found to transform into porosity during firing of the clay ceramic. Typically, the pore size of the clay ceramic corresponded to the particle size of the calibrated particles of PMMA. The improvement of the thermal and mechanical properties that was obtained during the extrusion process was conserved in the form of porosity with a reduction of the median pore size after the firing process. Hence, the current results indicate that the thermal and mechanical properties of fired clay bricks can be improved at the same time using a wide range of organic wastes if the organic wastes are subjected to grinding prior to incorporation in the mixture. They also suggest that organic wastes can reduce the environmental impact of fired clay bricks with an energetic contribution of 73.8%

Improvement of fired clay bricks properties through biomass incorporation

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The impact of heat treatment on the microstructure of a clay ceramic and its thermal and mechanical properties

International audienceThis paper presents the results of an experimental study on the microstructure, the thermal and the mechanical properties of a clay-based ceramic used in building applications. The X-ray tomography analysis showed a layered microstructure of clay with 200 mu m sheets of porosity after the extrusion process. The gas release from the dehydration, dehydroxylation and decarbonation induced a 7 vol% formation of porosity during the heat treatment of the clay-based ceramic up to 850 degrees C. The porosity increase and the development of metakaolin led to a 38% decrease in the thermal conductivity. On the other hand, the Young's modulus of the clay-based ceramic was conserved due to the formation of smaller pores than the 200 mu m sheets of porosity. The densification and the crystallization of amorphous phases also led to a 110% increase of the Young's modulus from 850 degrees C to 1050 degrees C. The Young's modulus of the clay-based ceramic was only decreased by the 13 Kt quartz inversion of the cooling due to sand addition. Hence, this study provided a useful insight into how the microstructure of fired clay bricks can be specifically transformed by the porosity during the heat treatment to control the thermal and mechanical properties

The impact of the particle size distribution of organic additives on the microstructure of a clay ceramic and its thermal and mechanical properties

International audienceIn this study, the structure-property relationships of a clay ceramic with calibrated particles (10 or 50μm) of polymethyl methacrylate (PMMA) were investigated to improve both the thermal and mechanical properties of fired clay bricks incorporating organic wastes. The structure was characterized using differential thermal, thermomechanical, and computed tomography analysis. It was found that the addition of 10- or 50–μm particles of PMMA resulted in a same 11% decrease of the thermal conductivity during the extrusion process. The Young’s modulus also increased by 23% during the extrusion process with the addition of 50–μm particles. However, the addition of 10–μm particles resulted in a greater increase of the Young’s modulus by 34%. The calibrated particles of PMMA were then found to transform into porosity during firing of the clay ceramic. Typically, the pore size of the clay ceramic corresponded to the particle size of the calibrated particles of PMMA. The improvement of the thermal and mechanical properties that was obtained during the extrusion process was conserved in the form of porosity with a reduction of the median pore size after the firing process. Hence, the current results indicate that the thermal and mechanical properties of fired clay bricks can be improved at the same time using a wide range of organic wastes if the organic wastes are subjected to grinding prior to incorporation in the mixture. They also suggest that organic wastes can reduce the environmental impact of fired clay bricks with an energetic contribution of 73.8%

Modeling of the thermal and mechanical properties of clay ceramics incorporating organic additives

International audienceThis paper presents the results of a combined experimental and theoretical study on a clay ceramic used for building applications. The thermal and mechanical properties of the clay ceramic were improved by addition of organic additives. The organic additives consisted of Olive Stone Flour (OSF), with round-shape particles of 55 µm, and Wheat Straw (WS), with 877 µm particles in the form of fibers. It was found that the combustion of OSF and WS resulted in a porosity formation during the firing process. The morphology of these pores corresponded to that of the organic additives. Therefore, the addition of small OSF particles decreased the median pore size of the clay ceramic. It improved the mechanical strength of the clay ceramic by 12% for an 8 wt% addition of OSF. On the other hand, the WS fibers increased the clay ceramic anisotropy. This resulted in a 41% improvement of the thermal conductivity using an 8 wt% addition of WS. Finally, a model was developed from these experimental results to predict the thermal conductivity and the mechanical strength of the clay ceramic with other organic additives. They were predicted from the parameters of the organic additives (i.e., true density, swelling degree, particle size distribution, particle shape factor). The predictions indicated that the thermal conductivity is improved by 50% with a 25% improvement of the mechanical strength using small organic fibers, which is a step forward in the development of fired clay bricks that can be used for both insulation and structure purposes in building applications