Performance of a Venturi scrubber in the removal of fine powder from a confined gas stream

Experimental results on the performance of a laboratory scale rectangular Venturi scrubber in the removal of fine mineral particles from a confined air stream are presented, and a new correlation is proposed and evaluated. The scrubber was operated with air velocities in the throat varying from 58 m/s to 75 m/s and liquid flow rates varying from 280 ml/min to 900 ml/min. Liquid was injected as a jet emerging from a 1.0 mm orifice at the throat. Results for dust collection grade efficiency varied from 87% to 98% for particles from 0.1 µm to 2.0 µm

A combined CFD modeling with population balance equation to predict pressure drop in venturi scrubbers

A venturi scrubber is one of the most important devices for air pollution control. Although there are different models for predicting the pressure drop in venturi scrubbers, most of them have some defects and cannot predict the pressure drop correctly. In this study, for the first time, an Eulerian–Eulerian computational fluid dynamics (CFD) model is combined with a population balance equation to predict the pressure drop in venturi scrubbers. This simulation takes into account a multiple size group model for droplet dispersion and droplet size distribution, which is based on a population balance equation. Flow field has been calculated by solving the time averaged continuity and Navier–Stokes equations along with the standard k–ε turbulence model. The equations included drag, turbulent dispersion, and buoyancy forces. The calculated pressure drop with and without considering the population balance equation was compared with the experimental data to evaluate the accuracy of the CFD modeling. The size distribution of droplets in the venturi scrubber was studied at different points for different liquid to gas ratios and throat gas velocities. The results show that the maximum break-up of droplets happens at the liquid injection point. Finally, the effects of nozzle diameter and nozzle arrangement on pressure drop in venturi scrubbers were investigated.Azam Sharifi, Ali Mohebb

Alimentação, estado nutricional e condição bucal da criança Food, nutritional status and oral condition of the child

A relação entre alimentação, estado nutricional e a condição bucal ainda não está bem esclarecida, apresentando, muitas vezes, versões controversas e conhecimento limitado. Existe certa concordância de que a alimentação e, conseqüentemente, o estado nutricional, possam exercer certa influência sobre a condição bucal imediata e futura da criança. O objetivo desta comunicação é apresentar possíveis relações entre alimentação, estado nutricional e a condição bucal da criança. O estado nutricional pode afetar os dentes durante o seu período de formação e após a erupção na cavidade bucal. Os efeitos sistêmicos provenientes da nutrição podem alterar o desenvolvimento dos dentes, a quantidade e a qualidade da saliva, assim como os efeitos externos também podem determinar uma maior prevalência de cárie dentária, uma vez que tanto a quantidade de sacarose ingerida, quanto a freqüência de ingestão são importantes fatores envolvidos em sua etiologia. As reflexões deste trabalho sugerem a necessidade de ações interdisciplinares para obtenção de resultados na prevenção e no tratamento das doenças bucais.<br>The relationship among food, nutritional status and oral condition is not yet well established, many times presenting controversial versions and limited knowledge. There seems to be an agreement that eating, and consequently, the nutritional status, may have a certain amount of influence over present and future oral conditions of the child. The objective of this communication is to discuss possible relations among food, nutritional status and oral condition in the child. Nutritional status may affect the teeth during their formation period and after eruption in the oral cavity. Systemic effects of nutrition may alter the development of teeth, quantity and quality of saliva, and the external effect may also determine a bigger prevalence of dental cavities, since both the quantity and the frequency of saccharose ingestion are important factors involved in their etiology. The reflections contained in this paper suggest that interdisciplinary actions are necessary in order to obtain results in the prevention and treatment of oral diseases