For a Soderberg Technology, paste production process consists of four basic steps: raw material handling; dry aggregate preparation; mixing; and briquettes loading at electrolytic cells for aluminum production. Dry aggregate is prepared from calcined petroleum coke, where the grains are crushed and separated between 3 different fractions of pre-determined sizing and a dust component. Petroleum pitch blended with the finest particles from dry aggregate forms the binder used for wetting, lubricating and filling open pores of larger coke grains, resulting into a higher anode paste quality with adequate mechanical properties, higher density, oxidation resistance and lower electrical resistivity. Raw materials recent trends showed significant quality degradation and cost raise, pushing up industry to look forward for untraditional suppliers, in addition to process optimization. This paper describes enablers chosen to improve paste properties, through dry aggregate particle size distribution using two of the most traditional particle packing models: Andreasen and Alfred. The formulations developed in this work were compared to the formulation originally used by an industry through measures flowability and apparent baked density. The results have shown that both the equations of Alfred and Andreasen, for distribution coefficient 0.30 and 0.52 respectively, can be applied to the Aluminum Industry, resulting into products significantly different from the point of view of quality.
On the ceramic tile production there are plenty of different possible origins inside the process that can lead to hue variation. Many tile producers use to increase the speed of production and the machinery industry follow this tendency to please their costumers; and so this scenario creates a need of a study on the influence of the speed production on hue variation. In this work this influence was verified using the silicon laser engraving method, one of the most methods worldwide used.
Concrete mixing technology has spread with the development of water-reducing additives, enabling production of high quality products. Despite the discoveries and important technological advances, occurrences concerning the incompatibility between sealers and additives have been reported. The main incompatibilities occur between additive and cement of different brands, or different batches. This study investigated the influence of a superplasticizer on the properties of two cements of the same class (type CP II E 32), but different manufacturers. Two cements (without the presence of the additive) were characterized by physical, chemical and mechanical tests. The setting times for pastes made from cement, water and superplasticizer mixtures were determined. The results showed a significant difference in physical, chemical and mechanical properties of cements, as well as those related to the hydration process thereof.
In the process of ceramic tiles production, the hue variation is one of the oldest and common problems whose appearance persists within the production and between two different productions of the same product; therefore it’s a problem to be solved still. Identify the origin the hue variation and minimize its occurrence it’s a constant challenge in the ceramic tile production, and the target is always to increase the quality end decrease the batches with different tones. Although the hue variation can have it’s origin within which one of the whole steps of the process, this work is focused on the decoration process using one of the most widespread technics of such step, the laser engraving silicon cylinders. This work accosts the influence of the speed of the ceramic line production and its effects on the hue variation. The studied characteristics were the shape and volume of the ink dot transferred by the cylinder to the tile surface, measured by optical microscopy and the result tone of the decoration, measured by spectrophotometry.
Several factors can influence the hue variation of tiles through contact elements; the pressure on the surface to be decorated is an important feature. This paper studied this variable applied to decoration by silicone cylinders. A variation of height was made between the cylinder and the tile. The influence of the feature is linked to cylinder wear and distance decrease. The reflectance, as well as the shape and filling of the decorated dots of gray scale values (5, 25 and 85%) were analyzed; the heights studied were 0.8; 1.0; 1.3 and 1.5mm. A similar behavior was observed in the engraving studied; in low shades of gray the reflectance decreases with increasing pressure and then becomes directly proportional; in the middle and high tones range the general trend was an increase in reflectance with increasing pressure on the ceramic tile.
In the ceramic tile decoration process, the set of variables that can cause hue variation is quite wide and independent of the methodology used in the production. The understanding of the effects of these variables over the final expected result is of great importance to the producers, especially if it could be done before the ceramic tile's sintering stage. The quality of the decoration is linked to the deposited dot shape and its filling with ink. It is proposed in this paper the determination of a 'quality index', comparing the theoretical deposition pattern and a real deposition obtained with samples. Measuring the values of the areas with and without ink, using the statistical tool of the ROC curve, it was obtained the values for sensibility=0.791, specificity=0.830, precision=0.802 and quality index=0.768. The method is intended to be used prior to the sintering step for hue variation control.
The increasing demand for tiles to be used in civil construction has resulted in the development of industrial ceramic production in Brazil. However, a bigger production of tile means an increase in raw material consumption, which could increase the amount of industrial waste materials. One of the guidelines within the Brazilian law for solid waste materials (“Política Nacional dos Resíduos Sólidos”) is “Integrated Management”. The objective of this subcategory is to insure that research and application are being done in a way that will offer a solution and a use for the solid waste materials. Through laboratorial experiments regarding the ceramic microstructure, the properties of the ceramic waste materials were determined. These materials show great properties such as high mechanical resistance. New formulas were made that include the addition of waste materials and it was concluded that the maximum quantity of waste materials that can be added to the pre-existing formula is 4%, which will save around R$ 11,833.90 per month for the Porto Ferreira Ceramic Industry. In addition to helping the company financially, this change in the formula will also decrease the number of broken tiles and decrease the environmental damage.
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