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Contribuição ao estudo de controle plantwinde: controle indireto e coordenação de controladores descentralizados
(Universidade Federal de São Carlos, 2005-03-28) Hori, Eduardo Shigueo; Kwong, Wu Hong
The design of plantwide control systems has received increasing attention in the last years. The modern chemical plants usually consist of hundreds of interconnected elementary processes and unit operations (large scale complex systems). These plants are usually characterized and dominated by large and highly integrated and automatized installations, with several recycle streams, more heat integration and fewer inventories. All these factors lead to high interactions among the subunits caused by material and energy recycle and, consequently to the need for a perspective beyond individual units. The plantwide system control design procedure is not clear and the literature is scarce about this issue, comparatively with simple unit design. In this way, a large challenge for the Chemical Engineer in the last decades has been designing control systems that operate with safety and bring the performance objectives needed to control these complex plants. The main objective of this project is to study the plantwide control problem aiming, particularly, the choice of controlled variables and the coordination of several decentralized controllers to avoid conflicting control actions. The results presented in this thesis show that the work objective was reached successfully, due to a significant contribution to plantwide control study.
Avaliação de transferência de calor e massa em biorreator Airlift de bancada para a produção de ácido clavulânico
(Universidade Federal de São Carlos, 2005-03-28) Cerri, Marcel Otávio; Badino Júnior, Alberto Colli; https://lattes.cnpq.br/7999741482353508
The importance of the airlift bioreactor has grown in the biotechnology field by aspects as high oxygen transfer, with power input low. In this work were study the conditions heat and mass transfer, as well as the condenser efficiency in the water retention, of an airlift bench bioreactor of internal circulation of useful capacity 6 L. Such bioreactor is endowed with hollow draft tube working as a heat charger for temperature control and of aspersor type crosspiece for aspersion of air. Values of the heat transfer global coefficient (U) were certain in different operation conditions starting from applied energy balance in the system after the same to reach the steady state. Values of U varied in the range from 300 to 700 W.m-2.°C-1, showing that the device of thermal change proposed was efficient to heat removal. The results were correlated with the water flow inside the draft tube and with the feeding air flow in the bioreactor. After this stage, it was evaluated water drags of the bioreactor system plus condenser in different conditions of air flow and temperatures in the bioreactor and in the condenser. The condenser was shown efficient in the water retention, obtaining efficiency superior values to 80%, but it didn't solve the problem of water loss by water drag for the high air flows in that the airlift bioreactor is operated. The variable air flow was the variable that influenced more significantly water drags. The transfer oxygen was evaluated through the oxygen transfer volumetric coefficient (kLa). For comparison, kLa values were obtained in the airlift bioreactor operated in a range of specific feeding air flow from 1 to 5 vvm and in conventional bioreactor of 4 L, in different agitation conditions (600, 800 and 1000 rpm) and aeration (0,5 and 1,0 vvm). Two methods for kLa determination were employees, the sulfite method and the dynamic method considering the delay of the electrode answer. This last one that generated results between 2 and 6 times inferior, depending of bioreactor type, because it evaluates the kLa in coalescent media, similar to most of the media fermentation. Finally, to validate the use of the system as bioreactor, cultivations with Streptomyces clavuligerus seeking to the production of clavulanic acid, a potent inhibitor of β-lactamase, enzyme producted by patogenics microorganism that broke β-lactamic rings of antibiotics. Four cultivations were accomplished, two in airlift bioreactor and two in bioreactor conventional (Bioflo III) in two different conditions of oxygen transfer (kLa) and the results were compared in terms of clavulanic acid production. The maximum clavulanic acid concentrations obtained in the cultivations in airlift bioreactor were superior those obtained in conventional bioreactor, with minors consistence index (K), showing larger shear rate in the airlift bioreactors in the same conditions of transfer oxygen. In global terms, the obtained results suggest that bioreactor as the most appropriate for this cultivation type, justified for the appropriate heat and mass transfers formed an alliance with the smallest energy consumption.
Avaliação experimental do fenômeno de retração em alvenaria de blocos de concreto
(Universidade Federal de São Carlos, 2005-03-28) Barbosa, Kleilson Carmo; Parsekian, Guilherme Aris; https://lattes.cnpq.br/7798651726059215
The shrinkage phenomenon is the cause of many verified pathological manifestations in buildings, especially in those with masonry produced with concrete blocks. The present work has as goal experimentally to evaluate the effect of shrinkage in masonry of concrete blocks. Studies had been carried through of shrinkage tests with blocks of different strength and processes of cure and also monitoring deformations of small walls constructed with each type of block. The walls had its deformations monitored for a period of one year, having been that the analyses had been formed taking in account the three first months of age. With the shrinkage tests are expected to get coefficients that allow the forecast of this effect in walls. From the necessary knowledge of the shrinkage of the wall it is possible to foresee the possibility of the appearance of cracks and to determine the necessity of the creation of control joints to prevent pathology and also to foresee losses of protension in prestressed masonry. As result of the work was possible to improve the procedure of test of shrinkage of concrete blocks according to Brazilian normalization. From the tests of walls it can be suggested values of shrinkage coefficient to be considered in project. Also it was possible to quantify some relative characteristics to the phenomenon, as the highest shrinkage observed in blocks produced with low quality control and in walls executed in recent ages, the impediment of shrinkage in the first row due to restriction of the support slab, the same order of magnitude for vertical and horizontal unrestricted shrinkage, among others.