The role of water on the equilibrium of esterification by immobilized lipase packed-bed column reactor
SummaryThe role of water on the continous synthesis of geranyl esters by immobilized lipase fromHumicola lanuginosa No. 3 was studied in a packed-bed column reactor (PBR) installed with a molecular sieve column for water extraction. The conversion degress by PBR were highly influenced by the water concentration throughout the reaction which acted as a determinant on the reaction equilibrium. Almost 100% conversion of geranyl laurate could be achieved under the optimum water-controlled conditions. The stability of the PBR system was for 35 days with the half-life of 38 days.
Synthèse d'esters de l'acide benzoïque par catalyse enzymatique en milieu hétérogène microaqueux
La synthese d'esters de l'acide benzoique par voie enzymatique en milieu heterogene microaqueux est envisagee. Cette esterification est possible et est catalysee par la lipase de Candida rugosa en suspension dans un melange hexane/toluene. Le toluene permet la solubilisation de l'acide benzoique. De nombreux parametres influencent la synthese des benzoates de methyle et de butyle. La teneur en eau initiale agit uniquement sur la cinetique de reaction sans modifier de maniere notable la position de l'equilibre de reaction. Il est preferable, dans la mesure du possible, de travailler a une activite en eau fixee au depart pour s'affranchir d'artefacts lies a la desorption de la pellicule aqueuse entourant les grains d'enzyme. Une approche par les plans d'experiences montre l'influence de plusieurs parametres et de certaines interactions entre facteurs sur la cinetique et sur l'evolution de la reaction. La vitesse initiale specifique decroit lineairement avec la fraction de toluene dans des milieux organiques contenant plus de 40% de toluene. Par contre, la variation de la Vi(sp) avec la teneur en enzyme est dependante de la nature de l'alcool et de sa concentration. les effets de la proportion de toluene dans le melange et de la teneur en enzyme sont expliques par la variation de la concentration en substrats dans la pellicule aqueuse entourant l'enzyme. La vitesse initiale de production du benzoate de 1-butyle est modelisee et realisee dans un melange equivolumique hexane/toluene a une activite en eau initiale de 0,65. La cinetique suit un schema reactionnel de type bi bi ping-pong avec inhibition par l'alcool si les concentrations en substrats dans la pellicule aqueuse sont prises en compte. En particulier, la concentration en acide benzoique dans cette phase est dependante de la concentration en 1-butanol. Ce travail demontre que la technique d'ajout d'eau dans le systeme, la variation des coefficients de partage des substrats entre milieu organique et pellicule aqueuse, la nature de l'alcool et les phenomenes d'inhibition par les alcools permettent d'expliquer les variations de vitesses initiales specifiques. Enfin, ce systeme catalytique permet d'obtenir ces benzoates avec des taux de conversion superieurs a 95% et peut- etre employe a la synthese d'autres benzoates.
Quantitative and qualitative relationship between swirl burner operatingconditions and pulverized coal flame length
Abstract Currently, there are used in power plants two types of burners to combustion the pulverized coal: jet burners and swirl burners. Most of the published works in the field of analysis of burners operating conditions are related to jet burners and are limited to initial region of the flame at the outlet of the burner. For jet burners an offset between the burner outlet and the flame beginning point could be analyzed. In the case of swirl burners with the pre-mixing diffuser chamber an offset between flame ignition point and burner outlet is usually not visible. Because already in the pre-mixing diffuser chamber of swirl burner occurs the ignition of coal-dust together with oxidant-gas cloud and thereby the formation of the flame. Therefore, the analysis of operating conditions for this types of burners requires a different approach. There is a lack of researches, in which will be analyzed changes of the flame length, that are caused by changes of design and operating parameters of swirl burner with the pre-mixing diffuser chamber. Therefore the aim of this study was to implement and verify the methodology for estimating the flame length, which will allow monitoring changes of operating conditions, that are caused by changes of design and operating parameters of swirl burner with the pre-mixing diffuser chamber. To carry out the analysis of the image of the coal flame, the two algorithms have been presented. This two algorithms, being based on the video images of the coal flame allows to specify and detect the end point of the flame and on that basis the length of the flame, as well as the fluctuation changes of flame length can be later determined. Both, the change thermal loads of coal burner, streams of secondary air, as well as the constructional change of the angle of swirler assemblies, resulted in distinct changes in the length of the pulverized coal flame.