Papers by Author: João Jorge Ribeiro Damasceno

Abstract: The filtration operation is one of the most widely used procedures in gas-solid separation due to its high removal efficiency, low cost and low sensitivity to variations in operating conditions. Therefore, the objective of this work is to study the effects of operating variables (pressure drop, filtration velocities and cleaning velocity) on the formation of filter cakes using gas-solid polypropylene filter media and particulate matter as for instance phosphate rock. The filtration velocities evaluated were 5, 7.5 and 10 cm/s with maximum pressure drops of 100, 200, 300 and 400mm H₂O and filter cleaning velocities of 15 cm/s by the reverse air flow method. The cake filtration porosity was estimated using the classical Ergun equation (1952) in the literature. The results led to important correlations for the use of fibrous filters in the removal of particles suspended in in micrometer aerosols.

Abstract: Orifice Meters are mechanical devices used to measure gases and liquids flows. Due to manufacturing, installation and operation simplicity, the orifice meters are widely used in the industrial processes in which there is flow of gases or liquids. Moreover, their acquisition and operation costs are smaller than the ones verified for other flow meters (Venturi, flowmeter). However, before the utilization of any calibration orifice meters, they demand an experimental calibration procedure. Thus, in order to suppress this laborious experimental procedure, this work objectified to apply computational fluid dynamics techniques (CFD) to numerically predict the Calibration Coefficient of the orifice meter. The adopted numerical methodology was able to satisfactorily predict the discharge coefficients, presenting an economic alternative when compared to traditional experimental approaches.

Abstract: Hydrocyclones are centrifugal devices widely used in chemical industries and they are used to the solid or liquid particles separation of a fluid according to the density and size distribution of the dispersed phase. In order to maximize the separation in these devices, this work had as objective to study the influence of the filtration during the process of separation in hydrocyclones. Thus, experimental data were used to predict the behavior of a hydrocyclone having a porous cylinder in the same operating conditions of a conventional hydrocyclone (impermeable cylinder). The experimental studies showed that the filtration interferes directly in the performance of the separator, so the filtering hydrocyclone required a higher pumping power. Moreover, the experimental data also indicated that the presence of the porous cylinder in the hydrocyclone was able to increase the number of dragged particles in the underflow, increasing therefore the efficiency of separation.

Abstract: The new environmental laws, as well as the search for technologies of accuracy production, have leaded companies to search for more and more efficient equipment. Regarding the emission of particulate material, the fabric filter is the most used equipment in the industry, for presenting a high efficiency and low operational costs, essential in any project of this type. In the search for a more efficient and economic filtering operation, this work studied, by techniques of CFD, the modification of the traditional way of feeding a filtering box (usually accomplished by the side of the system) by another in which the feeding was accomplished through the bottom of the equipment, in order to review the distribution of volumetric outflows in the bags and pressure drop. The fluid dynamic simulations had shown that the feeding fluid - through the bottom of the filtering box - provides an inferior operational pressure drop and a better distribution of fluids between the bags.

Abstract: The effective filtration area determined in a design of fabric filter depends on the filtration velocity, also known as air-to-cloth ratio that will be used. Low filtration velocities may demand big effective filtration areas. But then high filtration velocities may wear the filters out early. By searching for more efficient and economic equipments, this paper investigated the influence of the filtration velocity by formatting and removing the dust cake. Concluding that filtering at higher velocities a higher penetration of particles in the filter media occurs. Decreasing the filtration time and increasing the number which regenerates the cloth, consequently decreasing the life cycle of the filters.

Abstract: Slaked lime is a suspension of hydrated lime in water that can contain up to 40% of solids in suspension. The quality of the suspensions of slaked lime depends on the quality of lime used and on a careful choice of the conditions during the hydration process. A high quality slaked lime is a product with a small quantity of insoluble residues, high specific surface area, high alkaline content and small particle size. Therefore, the objective of this work was to study the best conditions of temperature and concentration to produce a superior slaked lime. A statistic analysis was performed using the experimental results in order to optimize the operational conditions of the hydration process. The use of hydration water around 74 °C, of small particles of CaO (0.144 mm) and of a CaO/H2O ratio around 220 g/L contributed to the production a slaked lime suspension of fine quality.

Abstract: Calcium carbonate (CaCO3) is a natural occurring mineral or it can be produced by chemical means. This last product is often referred to as Precipitated Calcium Carbonate (PCC). PCC has various advantanges since it exhibits higher brightness and opacity. There can be considerable variation in the properties of the PCC depending upon the process conditions used to prepare it. In this work, the effect of different factors on the particle size of PCC has been investigated. The experiments were performed by bubbling CO2 in slaked lime suspensions. The pH of the lime slurry was 12 or higher at the beginning, but it decreased, down to an equilibrium pH of 8± 1, when the reaction was considered complete.

Abstract: The settling vessels are equipment destined to solid-liquid separation; usually have continuous operation, with a circular section, presenting one conic and one cylindrical part. They are very used in chemical industries: wastewater treatment, minerals industries; to concentrate or to remove the solids. The solid particle splitting with small granular becomes difficult through the operation of conventional sedimentation. An expedient very used in the industry is the flocculant substance addition, whose objective is to promote the precipitation of particles, with decantation speed is upper than the single one. The present work aim the study of the burst operational conditions that influence the formation and the stability of these aggregates, the flake, the effect of pH and the concentration of flocculant using kaolin suspension and genfloc, that contains aluminum sulfate, as a flocculant; and the capacity of conventional settling vessel, which area of the transversal remains constant, considering this operational conditions.

Abstract: The filtering hydrocyclone is a solid-liquid separation device patented by the Chemical Engineering School of the Federal University of Uberlândia, which consists of a hydrocyclone whose conical section was replaced by a conical filtering wall. During the operation of these separators, besides underflow and overflow streams, the existence of a filtrate stream generated by the filtering process is found in the permeable conical region of the hydrocyclones. Vieira et al. (2006) got a filtering hydrocyclone that simultaneously presented low Euler Number and cut size diameter because its geometric relationships has been optimized. The objective of this work was to analyze the behavior of this optimized filtering hydrocyclone through computational fluid dynamics and experimental studies. In the same operational conditions of the conventional hydrocyclone, the performance of this optimized filtering hydrocyclone was significantly influenced by the filtration. The filtration caused decreases in the Euler number and increment in the total efficiency.

Abstract: The suspended particles in the air are a factor that causes chronic illnesses to the respiratory system, which go from allergy to severe pulmonary damage. Particulary, breathable particles (from 0,5 μm to 5,0 μm sizes) cause damages to the respiratory system. The penetration and the deposition are the reason for the damages to the pulmonary alveolus. The industrial activity is the main responsible for the most part of the breathable particles emission. Because of that, Venturi scrubbers have been incorporated to the industrial process due to their high efficiency for particle collection. Venturi scrubbers are gas-atomizing devices. They are mechanical devices which rely on shearing and impaction forces to break water into fine droplets. Those droplets in contact with the particles, will collected them. This work consists of a Venturi scrubber of circular section operating horizontally, with liquid injection through a single orifice located in the scrubber throat. The experiments will analyse the influence of the length throat, gas velocity, liquid flow and particles sizes on the Venturi´s collection efficiency.