Risk-based decision making method for maintenance policy selection of thermal power plant equipment

This study presents a decision-making method for maintenance policy selection of power plants equipment. The method is based on risk analysis concepts. The method first step consists in identifying critical equipment both for power plant operational performance and availability based on risk concepts. The second step involves the proposal of a potential maintenance policy that could be applied to critical equipment in order to increase its availability. The costs associated with each potential maintenance policy must be estimated, including the maintenance costs and the cost of failure that measures the critical equipment failure consequences for the power plant operation. Once the failure probabilities and the costs of failures are estimated, a decision-making procedure is applied to select the best maintenance policy. The decision criterion is to minimize the equipment cost of failure, considering the costs and likelihood of occurrence of failure scenarios. The method is applied to the analysis of a lubrication oil system used in gas turbines journal bearings. The turbine has more than 150 MW nominal output, installed in an open cycle thermoelectric power plant. A design modification with the installation of a redundant oil pump is proposed for lubricating oil system availability improvement. (C) 2009 Elsevier Ltd. All rights reserved.

Modeling extended Petri nets compatible with GHENeSys IEC61131 for industrial automation

Petri net (PN) modeling is one of the most used formal methods in the automation applications field, together with programmable logic controllers (PLCs). Therefore, the creation of a modeling methodology for PNs compatible with the IEC61131 standard is a necessity of automation specialists. Different works dealing with this subject have been carried out; they are presented in the first part of this paper [Frey (2000a, 2000b); Peng and Zhou (IEEE Trans Syst Man Cybern, Part C Appl Rev 34(4):523-531, 2004); Uzam and Jones (Int J Adv Manuf Technol 14(10):716-728, 1998)], but they do not present a completely compatible methodology with this standard. At the same time, they do not maintain the simplicity required for such applications, nor the use of all-graphical and all-mathematical ordinary Petri net (OPN) tools to facilitate model verification and validation. The proposal presented here completes these requirements. Educational applications at the USP and UEA (Brazil) and the UO (Cuba), as well as industrial applications in Brazil and Cuba, have already been carried out with good results.

Kinetics and Modeling of Fatty Alcohol Ethoxylation in an Industrial Spray Loop Reactor

The kinetics of the ethoxylation of fatty alcohols catalyzed by potassium hydroxide was studied to obtain the rate constants for modeling of the industrial process. Experimental data obtained in a lab-scale semibatch autoclave reactor were used to evaluate kinetic and equilibrium parameters. The kinetic model was employed to model the performance of an industrial-scale spray tower reactor for fatty alcohol ethoxylation. The reactor model considers that mass transfer and reaction occur independently in two distinct zones of the reactor. Good agreement between the model predictions and real data was found. These findings confirm the reliability of the kinetic and reactor model for simulating fatty alcohol ethoxylation processes under industrial conditions.

Optimizing model predictive control of an industrial distillation column

The main scope of this work is the implementation of an MPC that integrates the control and the economic optimization of the system. The two problems are solved simultaneously through the modification of the control cost function that includes an additional term related to the economic objective. The optimizing MPC is based on a quadratic program (QP) as the conventional MPC and can be solved with the available QP solvers. The method was implemented in an industrial distillation system, and the results show that the approach is efficient and can be used, in several practical cases. (C) 2011 Elsevier Ltd. All rights reserved.

The Policy Iteration Algorithm for Average Continuous Control of Piecewise Deterministic Markov Processes

The main goal of this paper is to apply the so-called policy iteration algorithm (PIA) for the long run average continuous control problem of piecewise deterministic Markov processes (PDMP`s) taking values in a general Borel space and with compact action space depending on the state variable. In order to do that we first derive some important properties for a pseudo-Poisson equation associated to the problem. In the sequence it is shown that the convergence of the PIA to a solution satisfying the optimality equation holds under some classical hypotheses and that this optimal solution yields to an optimal control strategy for the average control problem for the continuous-time PDMP in a feedback form.

Carbide lime and industrial hydrated lime characterization

This paper focuses on the characterization of carbide lime (CL) - a by-product of acetylene production, composed mainly of calcium hydroxide with minor parts of carbonate - and compares its features to those of ""dry"" hydrated lime (HL) commonly used as a building material. Chemical, thermogravimetric and X-ray diffraction analyses indicated that the limes are similar in chemical and mineralogical compositions. except for the presence of carbon in the waste. Morphological and elemental chemical analyses by SEM and EDS revealed that CL particles differ from HL ones in their morphology and by the presence of carbon formations, Physical characterization included density and BET surface area of the materials. as well as, their particle size distributions in deionized water at diverse time periods. CL underwent agglomeration after approximately 60 min in water, whereas HL progressively became finer with time as determined by laser diffraction. In addition, water retention and squeeze flow tests were used to assess the pastes` fresh properties. (c) 2009 Elsevier B.V. All rights reserved.

Forest Policy Reform in Brazil

Rapid deforestation in the Brazilian Amazon, caused by economic, social, and policy factors, has focused global and national attention on protecting this valuable forest resource. In response, Brazil reformed its federal forest laws in 2006, creating new regulatory, development, and incentive policy instruments and institutions. Federal forestry responsibilities are maintained within the ministry of the environment; its regulatory agency responsibilities are divided among three different branches of the agency; many powers are delegated to states and municipalities; and a new private concession system is being developed. These reforms offer promise to improve forest protection and management in Brazil but must overcome significant institutional and social resistance for success.

EFFECT OF CHEMICAL INTERESTERIFICATION ON PHYSICOCHEMICAL PROPERTIES AND INDUSTRIAL APPLICATIONS OF CANOLA OIL AND FULLY HYDROGENATED COTTONSEED OIL BLENDS

Blends of canola oil (CO) and fully hydrogenated cottonseed oil (FHCSO), with 20, 25, 30, 35 and 40% FHCSO (w/w) were interesterified under the following conditions: 0.4% sodium methoxide, 500 rpm stirring, 100C, 20 min. The original and interesterified blends were examined for triacylglycerol composition, melting point, solid fat content (SFC) and consistency. Interesterification caused considerable rearrangement of triacylglycerol species, reduction of trisaturated triacylglycerol content and increase in disaturated-monounsaturated and monosaturated-diunsaturated triacylglycerols in all blends, resulting in lowering of respective melting points. The interesterified blends showed reduced SFC at all temperatures and more linear melting profiles if compared with the original blends. Consistency, expressed as yield value, significantly decreased after the reaction. Iso-solid curves indicated eutectic interactions for the original blends, which were eliminated after randomization. The 80:20, 75:25, 70:30 and 65:35 (w/w) CO: FHCSO interesterified blends showed characteristics which are appropriate for their application as soft margarines, spreads, fat for bakery/all-purpose shortenings, and icing shortenings, respectively. PRACTICAL APPLICATIONS Recently, a number of studies have suggested a direct relationship between trans isomers and increased risk of vascular disease. In response, many health organizations have recommended reducing consumption of foods containing trans fatty acids. In this connection, chemical interesterification has proven the main alternative for obtaining plastic fats that have low trans isomer content or are even trans isomer free. This work proposes to evaluate the chemical interesterification of binary blends of canola oil and fully hydrogenated cottonseed oil and the specific potential application of these interesterified blends in food products.

Incorporating demand-side aspects into regional policy: variations in the importance of private investment decision factors across regions

Most regional programs focus on the supply side of regions, emphasizing the attraction conditions offered, such as infrastructure, labor skills, tax incentives, etc. This study analyzes one aspect of the demand side, that is, how investment decisions of private firms are made by asking the question: ""Do corporations decide the same way on investments in different parts of the territory?"" The paper analyzes the investments of 373 large Brazilian firms during 1996-2004. Based on the investment decisions of these firms, the role of sales, cash-flow, external financing, and working capital is investigated through regression analysis. The regional influence is captured by explanatory variables representing regional and firm characteristics, and by interaction dummies between the region and the main investment determinants. The results indicate significant differences across regions in the importance of investment determinants. This information is important for regional development policy, because different mechanisms should be used in different regions to foster private investments.

Fiscal policy and reelection in Brazilian municipalities

This paper uses a new panel of more than 2,000 Brazilian municipalities over 13 years to analyze the influence of public expenditures on the probability of mayors` reelection. We examine Brazilian municipal elections from 1988 to 2000 using a logit fixed-effects model. The results suggest that mayors who spend more during their terms of office increase the probability of their own reelection or of a successor of the same political party. In particular, higher capital spending over the years preceding elections and current expenditures in election years are beneficial to Brazilian incumbent mayors.

A costs structure analysis of the Brazilian sugar and ethanol companies

The Brazil consolidated itself as the largest world producer of sugarcane, sugar and ethanol. The creation of the Programa Nacional do Alcool - PROALCOOL and the growing use of cars with flexible motors were some of the factors that helped to motivate still more the production. Evolutions in the agricultural and industrial research did the Brazilian competitiveness in sugar and ethanol globally elevated, what is evidenced when comparing the amount produced at the country and the production costs, which turned a big one differential. Therefore, the administration of costs is of great relevance to the sugar and ethanol companies, for representing a significant rationalization in the production processes, with economy of resources and the reach of better earnings, besides reducing the operational risk pertinent at the fixed costs of production. Thus, the present work has for objective to analyze the costs structure of sugar and ethanol companies of the Center-south area of the country through an empiric-analytical study based in methodologies and concepts extracted of the costs accounting. It is verified that great part of the costs and operational expenses have variable behavior, a positive factor for the sector reducing the operational risk of the activity. The main restraint of this study is the sample of five years and 10% of the number of plants in Brazil that although they represent 30% of the national production, don`t allow the generalization of the model.

FOOD, FUEL, FORESTS, AND THE PRICING OF ECOSYSTEM SERVICES

U.S. Department of Energy (DOE), Office of Science[DE-FG02-94ER61937]

Forward-looking versus recursive-dynamic modeling in climate policy analysis: A comparison

This paper develops a multi-regional general equilibrium model for climate policy analysis based on the latest version of the MIT Emissions Prediction and Policy Analysis (EPPA) model. We develop two versions so that we can solve the model either as a fully inter-temporal optimization problem (forward-looking, perfect foresight) or recursively. The standard EPPA model on which these models are based is solved recursively, and it is necessary to simplify some aspects of it to make inter-temporal solution possible. The forward-looking capability allows one to better address economic and policy issues such as borrowing and banking of GHG allowances, efficiency implications of environmental tax recycling, endogenous depletion of fossil resources, international capital flows, and optimal emissions abatement paths among others. To evaluate the solution approaches, we benchmark each version to the same macroeconomic path, and then compare the behavior of the two versions under a climate policy that restricts greenhouse gas emissions. We find that the energy sector and CO(2) price behavior are similar in both versions (in the recursive version of the model we force the inter-temporal theoretical efficiency result that abatement through time should be allocated such that the CO(2) price rises at the interest rate.) The main difference that arises is that the macroeconomic costs are substantially lower in the forward-looking version of the model, since it allows consumption shifting as an additional avenue of adjustment to the policy. On the other hand, the simplifications required for solving the model as an optimization problem, such as dropping the full vintaging of the capital stock and fewer explicit technological options, likely have effects on the results. Moreover, inter-temporal optimization with perfect foresight poorly represents the real economy where agents face high levels of uncertainty that likely lead to higher costs than if they knew the future with certainty. We conclude that while the forward-looking model has value for some problems, the recursive model produces similar behavior in the energy sector and provides greater flexibility in the details of the system that can be represented. (C) 2009 Elsevier B.V. All rights reserved.

Production of fibrolytic enzymes by Aspergillus japonicus C03 using agro-industrial residues with potential application as additives in animal feed

Solid-state fermentation obtained from different and low-cost carbon sources was evaluated to endocellulases and endoxylanases production by Aspergillus japonicus C03. Regarding the enzymatic production the highest levels were observed at 30 degrees C, using soy bran added to crushed corncob or wheat bran added to sugarcane bagasse, humidified with salt solutions, and incubated for 3 days (xylanase) or 6 days (cellulase) with 70% relative humidity. Peptone improved the xylanase and cellulase activities in 12 and 29%, respectively. The optimum temperature corresponded to 60 degrees C and 50-55 degrees C for xylanase and cellulase, respectively, both having 4.0 as optimum pH. Xylanase was fully stable up to 40 degrees C, which is close to the rumen temperature. The enzymes were stable in pH 4.0-7.0. Cu(++) and Mn(++) increased xylanase and cellulase activities by 10 and 64%, respectively. A. japonicus C03 xylanase was greatly stable in goat rumen fluid for 4 h during in vivo and in vitro experiments.

Brazil The Swinging Pendulum Between Labor Sociology and Labor Movement

In this article, the authors analyze the relationship between labor sociology and trade unionism in Brazil by focusing on its three key phases. Against the backdrop of successive political and economical scenarios, the authors go from the first generation of labor sociologists to the most recent period, trying to identify the transition points in this trajectory. This study develops the hypothesis that labor sociology in Brazil was first characterized by a search for affirmation and professionalization (1950-1960). Later, it developed a strong political-social engagement, and assumed a public character, by claiming particular social identities (1970-1980). Finally, it flowed toward policy sociology (1990-2000).