Hydrodynamic evaluation of a mechanical flocculation pilot unit

This work focused on the hydrodynamic research aiming at the short-circuiting evaluation for five different outlet configurations through the compartments of a vertical paddle flocculation pilot unit. The tests were carried out with variable and constant velocity gradients, including alternative rotation direction of the paddles. The research pointed out that the relevance of outlet configuration increases with the reduction of the number of compartments. In opposite, the velocity gradient and the rotation direction of paddles seem less significant features. These results open the perspective of viable increasing of performance, with low financial investments, mainly for flocculation units with three or two compartments installed in overloaded water treatment plants

Transferência de oxigênio em reatores de leito fluidizado com circulação em tubos concêntricos em meios bifásico e trifásico com variação da relação entre diâmetros

A eficiência do reator de leito fluidizado com circulação em tubos concêntricos depende das condições hidrodinâmicas que influem na transferência de oxigênio ao biofilme. Este trabalho investigou a influência da relação entre diâmetros dos tubos e da concentração de meio suporte (areia), sobre o coeficiente global de transferência de oxigênio (K La). Os ensaios - em reatores de 2,6 m de altura, com diâmetro externo de 250 mm e internos de 100, 125, 150 e 200 mm - empregaram vazões de ar até 2.500 L.h-1 e concentrações de até 150 g.L-1 de areia. O K La aumentou ligeiramente com 30 g.L-1 e diminuiu para concentrações maiores, confirmando relatos da literatura em condições semelhantes. Um modelo para K La em meio bifásico foi ajustado para as diversas relações ensaiadas entre a área externa e a interna, postulando-se uma redução na razão entre a transferência na fase líquida e o diâmetro da bolha com o aumento da vazão de ar.The efficiency of the concentric tubes internal-loop airlift reactor depends on the hydrodynamic conditions that affect oxygen transfer to the biofilm. This work studied the effects of the relation between diameters of the tubes and of the carrier (sand) concentration on the global oxygen transfer coefficient (K La). The tests - in 2,6 m high reactors with 250 mm external diameter and 100, 125, 150 and 200 mm internal diameters - were performed with air flow taxes up to 2,500 L.h-1 and sand concentrations up to 150 g.L-1. The K La increased slightly for 30 g.L-1 and decreased for higher concentrations, in accordance with related data for similar conditions. A model for K La in biphasic medium was fitted embracing all the external/internal area relationships tested, based on the reduction of the liquid phase transfer coefficient and the bubble diameter ratio with increasing air flow rates

Estimativa das máximas pistas de vento no reservatório da barragem de Ilha Solteira, Estado de São Paulo

Most methods employed to estimate the height of waves generated by the wind require the surface length over which the wind blows. The choice of method depends on the nature of the water body, being applicable to ocean areas or interior water bodies, such as bays, lakes and reservoirs. One of the usual solutions has been the direct usage of the method validated in ocean waters for interior waters, therefore, not taking into consideration the effect of the restriction imposed by the shores. Nevertheless, the excessive quantity of operations of the method applied to interior water bodies (where the shore is a restraint condition) may not assure a satisfactory precision degree, unless an accurate enough graphic base of the shore with the addition of the operator's subjectivity is used. Thus, this scientific community brings this discussion to light, proposing a classic solution based on the application of the adequate method to interior waters (Saville et al., 1954) via automatized processing. Therefore, a program in AutoLISP, a computational language, has been developed. The application of the program has determined the maximum wind fetches in Ilha Solteira, state of São Paulo, reservoir as being between 9.5 and 12.5 km, in contrast with a previous study which has predicted far longer fetches (factor of three)

Reactores aeróbios de lecho fluidizado trifásico con circulación interna: Caracterización hidrodinámica y del soporte

Aerobic internal-loop reactors use active biomass attached in a supporting media (biofilm) with the advantage of retaining a big biomass concentration in a small physical space, removing carbonaceous matter and nitrogen in only one reactor. Liquid circulation occurs due to hydrostatic pressure difference produced by air injection in the riser. In biphasic conditions liquid circulation velocities, gas holdup and oxygen transfer coefficient in four different reactor configurations were studied. For the three-phase conditions, the same parameters in just one of those configurations were evaluated. Also, there were three granular supporting media characterized. On the other hand, the relationship between internal and external tube areas and supporting media concentrations influence the liquid velocity, gas holdup and oxygen mass transfer values and some important supporting media characteristics were observed and compared