Effect Of Immobilized Cells In Calcium Alginate Beads In Alcoholic Fermentation.

Saccharomyces cerevisiae cells were immobilized in calcium alginate and chitosan-covered calcium alginate beads and studied in the fermentation of glucose and sucrose for ethanol production. The batch fermentations were carried out in an orbital shaker and assessed by monitoring the concentration of substrate and product with HPLC. Cell immobilization in calcium alginate beads and chitosan-covered calcium alginate beads allowed reuse of the beads in eight sequential fermentation cycles of 10 h each. The final concentration of ethanol using free cells was 40 g L-1 and the yields using glucose and sucrose as carbon sources were 78% and 74.3%, respectively. For immobilized cells in calcium alginate beads, the final ethanol concentration from glucose was 32.9 ± 1.7 g L-1 with a 64.5 ± 3.4% yield, while the final ethanol concentration from sucrose was 33.5 ± 4.6 g L-1 with a 64.5 ± 8.6% yield. For immobilized cells in chitosan-covered calcium alginate beads, the ethanol concentration from glucose was 30.7 ± 1.4 g L-1 with a 61.1 ± 2.8% yield, while the final ethanol concentration from sucrose was 31.8 ± 6.9 g L-1 with a 62.1 ± 12.8% yield. The immobilized cells allowed eight 10 h sequential reuse cycles to be carried out with stable final ethanol concentrations. In addition, there was no need to use antibiotics and no contamination was observed. After the eighth cycle, there was a significant rupture of the beads making them inappropriate for reuse.33

Nusselt number correlation for a jacketed stirred tank using computational fluid dynamics

The heat exchange in stirred tanks occurs mainly due to the impeller rotation and overall circulation of the fluid that promotes a more effective heat transfer between fluid and heat transfer surfaces. The type of impeller used and the size of the vessel (that affects the relation heat transfer area and volume of the vessel) have significant effects on the heat transfer. The heat transfer coefficient is very much dependent on the impeller and the speed of rotation. Empirical correlations are usually used to estimate the process side heat transfer coefficient. However, its dependence on the geometrical parameters restricts the use of those correlations to specific tank configurations. In this respect, the use of computational fluid dynamics (CFD) has recently emerged as an alternative to experimental studies. The procedure proved to be faster and lower cost, and the results proved to be accurate. In this study, CFD was applied to obtain a Nusselt number correlation for a jacketed stirred tank equipped with a six-blade Rushton turbine impeller. The Nusselt number correlation obtained from the simulated model agrees with experimental data providing a reliable representation of the heat transfer in the tank972586593CNPQ - Conselho Nacional de Desenvolvimento Científico e Tecnológicosem informaçã

Development of static mixers for miscible fluids in laminar flow with the use of computational fluid dynamics (CFD)

Static mixers with improved performance were developed from CFD simulations in a stepwise approach. The relevant geometric features of simple mixer designs and the corresponding mixing mechanisms—laminar shear, elongational flow, and distributive mixing—were identified first. This information was used to formulate guidelines for the development of new geometries. The solid elements of the static mixer should: (a) provide restrictions to the flow; (b) deflect the flow; (c) be sequentially rotated around the flow direction to provide symmetry; (d) extend from the center of the pipe to the vicinity of the walls to avoid short‐circuiting; and (e) distribute and remix the flow. Based on these guidelines, two improved mixer designs were developed: the DS A–I mixer has a good mixing efficiency and an acceptable pressure drop; the Fins 35° mixer is more efficient and compact, but requires a larger pressure drop. Their performance indicates that their use is possible on industrial applications894734744sem informaçãosem informaçã

DEVELOPMENT OF STATIC MIXERS FOR MISCIBLE FLUIDS IN LAMINAR FLOW WITH THE USE OF COMPUTATIONAL FLUID DYNAMICS (CFD)

Static mixers with improved performance were developed from CFD simulations in a stepwise approach. The relevant geometric features of simple mixer designs and the corresponding mixing mechanisms-laminar shear, elongational flow, and distributive mixing-were identified first. This information was used to formulate guidelines for the development of new geometries. The solid elements of the static mixer should: (a) provide restrictions to the flow; (b) deflect the flow; (c) be sequentially rotated around the flow direction to provide symmetry; (d) extend from the center of the pipe to the vicinity of the walls to avoid short-circuiting; and (e) distribute and remix the flow. Based on these guidelines, two improved mixer designs were developed: the DS A-I mixer has a good mixing efficiency and an acceptable pressure drop; the Fins 35 degrees mixer is more efficient and compact, but requires a larger pressure drop. Their performance indicates that their use is possible on industrial applications