Production planning using time windows for short-term multipurpose batch plants scheduling problems

This paper deals with short-time planning and scheduling in multipurpose plants subject to a variable demand profile. In this case, production delays are often due to equipment overload, and this paper addresses a two-level approach that is intended to help managers engineer a scheduling solution that fulfills a compromise between products' demands and plant loading. At the first level, once a product's demand and raw-material delivery plan are defined, backward and forward explosion procedures are developed in such a way that time windows, defined by the earliest starting time and latest finishing time for each batch, are generated. Those time windows are submitted to an extended capacity analysis, based on constraint-propagation mechanisms, which is intended to reduce the time windows. If, after the capacity analysis, the problem is still feasible and the plant loading is accepted, then a scheduling procedure is launched. The scheduling approach is based on a uniform discrete time representation that is intended to explore plant features, such as, zero-wait policies, limited storage; and/or low equipment demand. The mixed integer linear problem (MILP) approach, combined with the time-window shortening procedure at the planning level, leads to smaller MILP problems, thereby reducing the solution time.39103823383

Short-term planning and scheduling in multipurpose batch chemical plants: a multi-level approach

This paper deals with short-term planning/scheduling problems when the product demands are driven by customer orders. This type of problem is, in general difficult to be solved, once the orders are subject to changes in short periods. In this paper is proposed a multi-level decomposition procedure, containing at least two levels. At the planning level, demands are adjusted, a raw material delivery plan is defined and a capacity analysis is performed. Therefore, time windows for each operation are defined. At the scheduling level, an MILP model is developed. In order to reduce scheduling problem dimension, it is performed an analysis of equipment contention profile, enabling to model only situations where a decision variable is requested. (C) 2000 Elsevier Science Ltd. All rights reserved.24419212247225

Optimization of Chitosanase Production by Trichoderma koningii sp Under Solid-State Fermentation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)This study aimed at the optimization of the production of chitosanase in solid culture. Trichoderma koningii sp., an entomopathogenic fungus, was used to produce chitosanase under solid-state fermentation using a mixture of wheat bran and chitosan. The incubation period; addition of moistening water and culture medium composition were optimized. The protocol to extract the enzyme was also optimized. The optimal conditions for chitosanase production by T. koningii were obtained using a mixture of 3.0 g of wheat bran and 1.5 g of chitosan, with the addition of 2.5 mL of moistening water (pH 5.5) and of 2.5 mL of saline solution (pH 5.5) containing NaNO3 (1.0 g/L), (NH4)(2)HPO4 (1.0 g/L), MgSO4.7H(2)O (1.0 g/L), and NaCl (1.0 g/L). Optimal enzyme extraction was carried out adding 20 mL of sodium acetate buffer (200 mM, pH 5.5) at 30 A degrees C under orbital agitation at 150 rpm for 6 min. The optimized production yielded 4.84 IU/gds.5515641572Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Effect of pH and Temperature on Enzyme Activity of Chitosanase Produced Under Solid Stated Fermentation by Trichoderma spp.

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Trichoderma strains were extensively studied as biocontrol agents due to their ability of producing hydrolytic enzymes, which are considered key enzymes because they attack the insect exoskeleton allowing the fungi infection. The present work aimed to evaluate the ability of chitosanase production by four Trichoderma strains (T. harzianum, T. koningii, T. viride and T. polysporum) under solid stated fermentation and to evaluate the effect of pH and temperature on enzyme activity. pH strongly affected the enzyme activity from all tested strains. Chitosanase from T. harzianum and T. viride presented optimum activity at pH 5.0 and chitosanase from T. koningii and T. polysporum presented optimum activity at pH 5.5. Temperature in the range of 40-50 degrees C did not affect enzyme activity. T. polysporum was found as the most promising strain to produce chitosanase with maximal enzyme activity of about 1.4 IU/gds, followed by T. viride (similar to 1.2 IU/gds) and T. harzianum (1.06 IU/gds).5216065Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Contamination from an affluent of Furnas reservoir by trace metals

This study aims to determine concentrations and characterize trace metals distribution in an affluent of Furnas reservoir, Alfenas-MG. Water and sediment samples were taken monthly, 2010/10-2011/07 in five sites of Córrego do Pântano for subsequent determination of Pb, Cd and Zn levels by chemical analysis. The stream studied is in disagreement with Brazilian legislation for Class II water bodies (CONAMA 357). The highlights are the unsuitable concentrations of Pb for human consumption, according to Ministry of Health 2914 decree, providing risk for population

Contamination from an affluent of Furnas reservoir by trace metals

This study aims to determine concentrations and characterize trace metals distribution in an affluent of Furnas reservoir, Alfenas-MG. Water and sediment samples were taken monthly, 2010/10-2011/07 in five sites of Córrego do Pântano for subsequent determination of Pb, Cd and Zn levels by chemical analysis. The stream studied is in disagreement with Brazilian legislation for Class II water bodies (CONAMA 357). The highlights are the unsuitable concentrations of Pb for human consumption, according to Ministry of Health 2914 decree, providing risk for population