Artigos
URI permanente para esta coleçãohttps://repositorio.fei.edu.br/handle/FEI/800
Navegar
8 resultados
Resultados da Pesquisa
- Safety Related Development of a PEM Fuel Cell Supply and Control System(2023-02-05) BRUNO, B. F.; IBUSUKI, U.; URIEL, G. J.; Gerhard Ett (ETT, G.)© 2021 SAE International.Although the proton exchange membrane fuel cell (PEMFC) is still attracting enormous R&D interest because of its high energy density, its commercialization is hampered by many challenges including cutting cost, improving performance and increasing durability. While they could be solved by material selection, the durability of PEMFC is also affected by voltage reversals and fuel starvation. [1] Despite the problems related to the construction of the fuel cell, there are also problems in terms of safety. In the development chain of a technology, it is essential to take into account the origin of the materials used for their maintenance / after-sales. Knowing that hydrogen is a gas that has several peculiarities and among them the high combustion power, great attention is needed when handling it and therefore there is a sequence of good practices and standards to be respected from which will be discussed in this article.
- Risk analysis and environmental impact analysis in a chemical processing facility(2009-01-05) Maristhela Passoni de Araújo Marin; TAMBOURGI, E. B.The present work provides a method of risk analysis in chemical processing facilities, which consists primarily of the following steps: description and study of the system, hazard analysis and identification, identification of the accidental scenarios, calculation of the consequences of the scenarios and risk characterization. To illustrate the application of the method, an uranium hexafluoride production facility was selected. The main hazards identified were: fire, explosion, spill of toxic chemical substances and ground contamination due to problems in the waterproof blanket of the waste contention bund. Some cases of environmental impact due to uranium hexafluoride (UF6) release were quantitatively analyzed for different scenarios, considering two categories of atmospheric stability: Pasquill D and Pasquill F. It was found that the impact which reached a great external area around the plant corresponded to the condition of atmospheric stability F. © 2009 Elsevier B.V. All rights reserved.
- Optimal control of heat exchanger networks(2009-01-05) Luis Novazzi; ZEMP, R. J.Energy integration among chemical process streams can lead to quite complex heat exchanger networks (HEN) with difficulties in terms of control. In the HEN, the control system primary objective is to keep outlet stream temperatures in a specified range. This objective can be achieved by manipulating bypasses in the exchangers or heat loads in coolers or heaters, which results in a positive degree of freedom, since the number of possible manipulated variables is greater than the number of controlled variables. Thus, a secondary control objective can be set: minimization of utility consumption. In this work HEN dynamics and steady state aspects were addressed with the aim of proposing a control strategy that minimizes utility consumption and satisfies imposed restrictions. With the tools developed in this work it was proposed a feedforward optimal control strategy, which consisted in the minimization of a steady state objective function, connected to utility consumption and subjected to constraints in outlet stream temperatures. The suggested approach is an interesting one since rigid or flexible control objectives can be set. The solution of the minimization problem resulted in optimal bypasses positions in the HEN, which were dynamically implemented using a ramp function and a step function. It was verified that ramp implementation was better, with tolerable dynamic violations. © 2009 Elsevier B.V. All rights reserved.
- Bioreactor temperature control using a generic fuzzy feedforward controlsystem(2016-08-05) FONSECA, R. R.; Ivan Carlos Franco; SILVA, F. V.Fermentation process is widely used in industries to produce biofuels, beverages, foods and medicines. As example, ethanol is obtained via corn syrup fermentation by Saccharomyces cerevisae, a bioprocess that is thermal sensitive and requires temperature control to maintain microorganism metabolic rate. In a CSTR, the feed stream temperature is normally a load source, affecting process variable control that makes a feedforward control system highly recommended to this case. However, bioprocesses are intrinsically nonlinear processes, becoming very difficult to obtain satisfactory control performance using classic feedforward control. Nevertheless, Fuzzy logic control is indicated to this type of process because results in nonlinear control law. For this reason, this work presents a generic Fuzzy feedforward control strategy developed to be used with a feedback control system in nonlinear processes, aiming load rejection improvement. The results shown that the Fuzzy feedforward feedback control system (4FB) was better than only feedback control to reject feed stream temperature loads in Saccharomyces cerevisae fermentation in a CSTR, being an interesting control strategy for load rejection in nonlinear processes.
- Orthogonal least square based non-linear system identification of a refrigeration system(2016-08-05) DANTA, T. S. S.; Ivan Carlos Franco; SILVA, F. V.Chillers are important part of several processes in the Chemical, Petro-Chemical, Pharmaceutical, Beverage and Food industries. Controlling these processes at an advantageous operating point is essential to achieve high productivity and profitability. Ultimately control system design and controller tuning depend on accurate process knowledge in the form of dynamic mathematical models. But attempts to develop analytical models often stumble upon problems such as unknown physical parameters. In this work, system identification, an established modeling technique, is used to build a non-linear dynamic model of a chiller from raw Input-Output data. Two dynamic nonlinear stochastic models where obtained, one more compact and the other with more terms but more precise, showing good simulation results and average prediction errors between 3.65%-5.23%.
- Coupling of Fischer-Tropsch synthesis and MCH dehydrogenation in a multifunctional reactor(2016) Luis Novazzi; SANTOS, R. S.Multifunctional reactors are used in chemical process industries and promote thermal coupling between an exothermic and an endothermic reaction. The former supplies energy to the latter so they can be carried out simultaneously. Fischer-Tropsch (FT) synthesis coupled with methyl cyclohexane (MCH) dehydration in a multifunctional reactor was studied in this work, aiming the production of gasoline and hydrogen. The reactor was modelled by using material and energy balances for the reactional system, in a pseudo homogeneous, one dimensional and steady state model. Reaction kinetics were taken from the literature and the system of ordinary differential equations was solved in Matlab, in parallel flow. In addition to technical aspects, a preliminary economic evaluation was developed. Gasoline production was optimized and in the best operational conditions its yield was equal to 10.2 g / 100 g.
- Automation and Control of a Dissolved Air Flotation Pilot Plant(2017) Fonseca R.R.; Thompson J.P.; Franco I.C.; da Silva F.V.© 2017Turbidity is an important process variable on water treatment processes for safeguard health requirements, and dissolved air flotation (DAF) is a physical treatment that allows water turbidity reduction by floating particles dispersed on water. Hence, a DAF pilot plant was assembled and automated using supervisory control and data acquisition (SCADA), open platform of communication protocol (OPC), signal filters and Ethernet to test two possible strategies for water turbidity control. The results indicated that manipulating recycle ratio by needle valve opening has advantages on DAF control.
- Study of acetylsalicylic acid adsorption using molecular sieves(2015) Assumpcao G.; Poco J.; Fernandez-Felisbino R.; Cardoso D.; Gomes E.Molecular sieves can be used as a host matrix to encapsulate several drugs. Here, we studied the adsorption of acetylsalicylic acid (ASA) in HUS-Y, HZSM-5 and silicalite-1 zeolites, as well as in the mesoporous sieve Si-MCM-41, and compared their adsorption capacities. The materials used generally presented good performance for ASA adsorption. Among the zeolites studied, HZSM-5 adsorbed large amounts of drug than the others. The Si-MCM-41 samples synthesized with fumed silica presented better adsorption performance than those synthesized with tetraethyl orthosilicate. The best mesoporous sample for adsorption synthesized with fumed silica was chosen for the kinetic assay. The adsorption kinetics of ASA for this sample fitted well to a second-order model. The initial loading rate and diffusion coefficient for the ASA-mesoporous sieve system were 0.153% (mg ASA)/(mg solid/minute) and 5.02 × 10-17 m2/s, respectively. The materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen physisorption.