Brazilian Power Plant Research Articles

Economic and CO2 avoided emissions analysis of WWTP biogas recovery and its use in a small power plant in Brazil

An anaerobic wastewater treatment generates at the end of its process an anaerobic biomass, also known as anaerobic sludge, and a major sub product, the biogas, composed mainly by methane (CH4) and carbonic gas (CO2). The biogas needs to be collected in order to be flared or used in another process, especially because it cannot be released directly into the atmosphere due to methane gas and its high global warming potential. Nevertheless, when this gas is burnt, an energy vector for micro generation is discarded. In the present work was designed a thermal power plant using the biogas produced in an anaerobic wastewater treatment plant (WWTP) through an implementation methodology that considers the population growth according to a southeast ordinary Brazilian city. The energy production potential, avoided CO2 emissions due to the biogas burnt and the possibility of using this energy to supply the WWTP’s internal demand consumption were analyzed, as well as the project’s economic viability and the arising benefits from carbon credits, calculated in three scenarios. The data of calculus were based on the Brazilian sales tariffs obtained from Brazilian National Electric Energy Agency – ANEEL, where: i) T1=64.9[US$/MWh] (average tariff on Brazilian energy auction A-5); ii) T2=86.47[US$/MWh] (average tariff for thermal power plants in the same auction), and iii) the third scenario, in which the energy produced would be consumed by the WWTP’s internal demand. The economic viability was only achieved in second and third scenarios, being intensified in the scenario that WWTP’s internal demand is supplied using the energy generated in the biogas plant.

Agricultural and agro-industrial residues-to-energy: Techno-economic and environmental assessment in Brazil

This study aims to quantify the environmentally sustainable and economically feasible potentials of agricultural and agro-industrial residues to generate electricity via direct combustion in centralised power plants in Brazil. Further, the energy savings and greenhouse gas (GHG) reduction potential of replacing natural gas-based electricity by bioenergy have been assessed. To this end, a methodology has been developed based on an integrated evaluation, incorporating statistical and geographical information system (GIS)-based analysis, and a life-cycle-assessment approach. Results reveal that the environmentally sustainable generation potential is nearly 141 TWh/year, mainly concentrated in the South, Southeast, and Midwest regions of the country. Sugarcane, soybean and maize crop residues are the major feedstocks for available bioenergy. On the other hand, the economic potential is far lower, accounting to 39 TWh/year. The total GHG mitigation is nearly 18 million tonne CO2e and could reach 64 million tonne CO2e yearly, if the technical potential is considered. The gap between technical and economic potentials implies that constraints to bioenergy are not related to a lack of resources, but rather associated to economic, logistical, regulatory and political barriers.

Analysing a power transformer’s internal response to system transients using a hybrid modelling methodology

Abstract This article presents a novel approach to analysing a power transformer’s internal response to system transients. In this approach a hybrid modelling methodology is adopted which leverages the distinct advantages offered by both Black and Grey Box modelling techniques. The Black Box model of the transformer is used within the EMTP system study environment in order to take advantage of its mathematical flexibility and modelling accuracy. Transients derived from network switching operations within the study can then be used for injection tests within the Grey Box modelling environment. The Grey Box model, which is based upon the physical structure of the transformer, will facilitate analysis of the transformer’s internal voltage response to the external stimulus. A fundamental difference between the approach described in this paper and more traditional approaches is that it does not require prior knowledge of the internal geometry of the transformer. All of the modelling parameters are derived from external tests, nameplate details and an intrinsic understanding of common transformer design principles. This can be a distinct advantage since in most cases a transformer’s design specifications are not readily available outside of the laboratory due to the manufacturer’s intellectual property restrictions. A study of a gas insulated substation within a hydroelectric power plant in Brazil is used to demonstrate the proposed technique.

Estimates and Spatial Distribution of Emissions from Sugar Cane Bagasse Fired Thermal Power Plants in Brazil

Sugar cane bagasse is one of the largest fuels used for electricity generation in Brazil and its usage has continuously increased to supply the energy demand. This paper presents emission inventory based on power plants burning sugar cane bagasse. The inventory involves the spatial distribution and the estimated flows for the following major pollutants: nitrogen oxides (NOx), particulate material (PM), carbon dioxide (CO2) and total organic carbon (TOC). A total of 384 power plants were inventoried, representing a generated power of 9.9 GW, about 26% of the energy produced by thermal power plants sector. The plants are concentrated in two main poles: one of them in S?o Paulo State and nearby areas and the other one in coast of Brazilian Northeast. The limits proposed by the AP-42 Regulations of the US Environmental Protection Agency (USEPA) for the emission factors were applied. Additional emission factors identified in the scientific literature were also included in the analysis in order to assess the uncertainties associated to the estimative. The estimated emissions showed values in the range 16.0 - 20.5 Gg?year?1 for NOx, 18.0 - 267.0 Gg?year?1 for MP and 20.5 - 26.7 Tg?year?1 for CO2. The contribution of TOC showed a minor contribution around 10 - 20 Mg?year?1. PM showed to be the most representative pollutant emitted by the thermal plants burning sugar cane bagasse, but with a large range of uncertainty. There is a high level of uncertainty associated to the preparation of cane as well as the use of collectors to control particulate emissions. The adequate control over all stages could reduce the bagasse ash content in 90% or more.

Techniques of the Optimization Based in Artificial Intelligence Applied to Hydrothermal Power Systems Operation Planning

The Hydrothermal Power Systems Operation Planning (HPSOP) aims to determine a strategy for each generation plant at each time interval in order to minimize the expected value of operating costs in the planning horizon. This is a challenge for managers of the Energy Sector, because of the stochastic nature of the problem which is coupled in time (dynamic) and in space (interconnected), large, not separable, non-convex and the target function is non-linear. Therefore, the application of classical techniques presents several limitations. In order to overcome those limitations, improvement of traditional methods, or the development of alternative heuristics is a vital step in the operation of HPSOP. This paper presents an application of two of this new heuristics of Artificial Intelligence: Genetic Algorithms and Ant Colony Optimization. Those techniques were applied to a test system with data from Brazilian power plants. The results showed a good performance when compared with traditional optimization techniques already used in HPSOP. It is noteworthy that in the current study, the applications of traditional optimization techniques and Artificial Intelligence have made use of real characteristics of plant operation without the need to simplify the original formulation.

EPSIM - A Social-Environmental Regional Sequential Interindustry Economic Model for Energy Planning: Evaluating the Impacts of New Power Plants in Brazil

This study proposes a social-environmental economic model, based on Regional Sequential Interindustry Model (SIM) integrated with geoprocessing data, in order to identify economic, pollution and public health impacts in state and municipality levels for energy planning analysis. Integrating I-O framework with electrical and dispersion models, dose-response functions and GIS data, this model aims to expand policy makers’ scope of analysis and provide an auxiliary tool to assess energy planning scenarios in Brazil both dynamically and spatially. Moreover, a case study for wind power plants in Brazil is performed to illustrate its usage.

On-line cleaning technique for mitigation of biofouling in heat exchangers: A case study of a hydroelectric power plant in Brazil

An experimental methodology was developed to assess an on-line cleaning technique to mitigate biofouling in plate heat exchangers. The exchangers are used in the cooling system of the journal bearings of hydro-generators of a power plant. The cleaning technology tested consisted of a non-intrusive electronic device wrapped around the water cooling piping that generated an electric field to inhibit the growth of micro-organisms on the heat transfer surfaces. Limnology studies explained the phenomenon of biofouling formation caused by limnophilous microorganisms present in the deepest parts of the reservoir manage to survive in hostile environments under anoxic conditions. Two criteria were adopted to assess the performance of the antifouling technology: a hydrodynamic criterion based on Kakaç’s pressure drop equation for plate heat exchangers and a thermal criterion (index of fouling) that takes into account the heat transfer effectiveness under the clean and fouled conditions of operation. The position of the antifouling device produced better results when installed in the primary cooling circuit. For the conditions studied, the cleaning technique mitigated biofouling but did not eliminate it completely. Excitation of the flow by an electric field diminishes the pressure drop and the index of fouling when compared to the unexcited flow condition. Control and reduction of the fouling thermal resistance is highly desired as it drastically lessens mechanical pumping costs and increases heat transfer performance.

How the choice of multi-gas equivalency metrics affects mitigation options: The case of CO2 capture in a Brazilian coal-fired power plant

Abstract This study shows how the assessment of emissions reductions from CO 2 capture is critically dependent on the choice of multi-gas equivalency metric and climate impact time horizon. This has implications for time-sensitive mitigation policies, in particular when considering relative impact of short-lifetime gases. CO 2 , CH 4 and N 2 O emissions from a coal-fired power plant in Brazil are used to estimate and compare the CO 2 -equivalent emissions based on standard practice global warming potentials GWP-100 with the less common GWP-50 and variable GWP for impact target years 2050 and 2100. Emission reductions appear lower for the variable metric, when the choice of target year is critical: 73% in 2100 and 60% in 2050. Reductions appear more favorable using a metric with a fixed time horizon, where the choice of time horizon is important: 77% for GWP-100 and 71% for GWP-50. Since CH 4 emissions from mining have a larger contribution in the total emission of a plant with capture compared to one without, different perspectives on the impact of CH 4 are analyzed. Use of variable GWP implies that CH 4 emissions appear 39% greater in 2100 than with use of fixed GWP and 91% greater in 2050.

Public-Private Partnership Model for Developing Sustainable Hydroelectric Power Plants in Brazil

In this article, the Brazilian Model for Public-Private Partnership (PPP) is described. It was conceived envisaging investments for the completion of new electric sustainable power plants. The objective is to present the main drivers in Brazilian regulatory system for private investors in what relates to risks configuration and investment decision-making, either Brazilian or foreign ones. We analyzed the investment in 5 Brazilian power plants that altogether constitute an electric power-generating complex in Juruena River, in the state of Mato Grosso, in Brazil. According to the results, we can conclude that the present legal framework is able to support investment in small hydroelectric and sustainable power plants, considering the existence of Engineering Procurement Contracts (EPC) for the completion phase and of Power Purchase Agreements (PPA) for the operational phase as well. Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved.

Analysis of the qualified life extension of nuclear safety systems through modulated Poisson point processes

The Modulated Power Law Process (MPLP) is a three-parameter stochastic point process that can be used to describe the failure times of repairable systems. While the Non-Homogeneous Poisson Process (NHPP) or the Renewal Process (RP) implies that a system is exactly on the same condition just after a repair as just before a failure, the MPLP allows for the system to be affected both by failure and repair. For this reason this model is adequate for evaluating the recurrent events that incorporate both time trends and effects of past events such as the renewal type behavior. The purpose of this paper is to evaluate the MPLP as a model for the rate of occurrence of failures (ROCOF) of repairable systems to decide for an extension of qualified life in the context of a license renewal of a nuclear power plant. The analysis was carried out considering some field data spanning a 2300 calendar day period, which is approximately equivalent to four burn-up cycles and refueling periods. The reliability is estimated, and maintenance strategies are discussed, concerning the results of the case study presented. As a conclusion, the MPLP is adequate for modeling the rate of occurrence of failures that are time dependent, and can be used where aging mechanisms are present in the operation of repairable systems. This means that equipment characteristics that are important may be inserted into the model and the results can help make decisions in the context of maintenance programs, as is the case with the maintenance rule concept that has been proposed by the U.S. Nuclear Regulatory Commission and has just been implemented in nuclear power plants in Brazil, for instance. The difficulty with data acquisition for applying point processes is discussed throughout.

EPSIM - An Integrated Sequential Interindustry Model for Energy Planning: Evaluating Economic, Electrical, Environmental and Health Dimensions of New Power Plants

Energy is the input in which modern society depends the most for life standard maintenance besides economic and social activities, however, it is also one of the major sources of greenhouse gases (GHG) emissions, especially the electric sector, due to a world energy matrix concentrated on oil and coal resources. Hereby, impact analysis is essential for policy making focused on sustainable energy systems, once it provides ex ante evaluations for the diverse effects of new projects, being especially important in relation to large infra-structure investments as power plants. In the Brazilian case, although the current electrical matrix is primarily renewable and has low GHG intensity, the required expansion of generation capacity leads to rediscuss power plants’ alternatives and their externalities. Due to the transient and heterogeneous demand of these projects, economic, environmental, energy and social impacts must be assessed dynamically and spatially. This study proposes a social-environmental economic model, based on Regional Sequential Interindustry Model (SIM) integrated with geoprocessing data, in order to identify economic, pollution and public health impacts in state and county levels for energy planning analysis. Integrating I-O framework with electrical and dispersion models, dose-response functions and GIS data, this model aims to expand policy makers’ scope of analysis and provide an auxiliary tool to assess energy planning scenarios in Brazil. Moreover, a case study for wind power plants in Brazil is performed to illustrate its usage.

A Multi-analytical Approach to Understand the chemistry of Fe-minerals in Feed Coals and Ashes

Seven feed coals used in the Brazilian power generation industry were obtained and subsequently analysed together with fly ash and bottom ash from a major Brazilian power plant. The samples were investigated by means of room temperature Fe-Mossbauer analyses, X-ray diffraction, Raman spectroscopy, scanning electron microscope and petrographic analysis. In addition, nanometer-sized crystalline phases in coals and ashes were characterised using an energy-dispersive X-ray spectrometer and a high-resolution transmission electron microscope. The major identified Fe-bearing minerals in the coals were found to be actinolite, ankerite, chalcopyrite, chlorite, goethite, illite, ilmenite, magnesioferrite, natrojarosite, pyrite, pyrrhotite, and siderite; whilst in the fly ash and bottom ash, ankerite, chlorite, chromite, goethite, hematite, hercynite, jarosite, maghemite, magnesioferrite, and magnetite were identified. Most of the Fe in the ash samples was present as Fe^3+^ resulting from the melting of Fe and silicates during combustion. The fraction of glassy Fe in those particles is high because of the high contact probability between Fe melt and silicates. The combination of the various methods offers a powerful analytical technique in the study of coal and coal ashes. This investigation can be regarded as an introductory and prospective study prior to further quantification.

Mineralogy and Leaching Characteristics of Coal Ash from a Major Brazilian Power Plant

The feed coals, fly ashes and bottom ashes collected from seven different units in a major Brazilian PF power plant have been subjected to comprehensive mineralogical, geochemical, and petrographic studies, to investigate the links between feed coal and ash characteristics. Ashes from two of the units were collected while the coal was being co-fired with oil as part of the boiler start-up procedure, allowing the impact of oil co-firing on ash characteristics also to be evaluated. High proportions of unburnt carbon and high proportions of retained sulphur were found in the fly ashes produced during oil co-firing, probably reflecting less efficient combustion and associated lower combustion temperatures. Higher concentrations of a number of relatively volatile trace elements were also noted in these fly ashes, compared to the fly ashes collected from units under normal operating conditions. The fly ashes produced during oil co-firing gave rise to acid pH conditions in water-based leaching tests, in contrast to the alkaline pH associated with fly ashes produced during normal operations. This probably reflects higher SO~3~ contents relative to total CaO + MgO for the co-fired ash samples. Many trace elements that are typically mobilised as cations were also more abundant in leachates from the co-fired fly ashes. This is due, most likely, to the more acid pH conditions involved. Despite similar or even higher total concentrations, however, elements that are typically released from coal ash as oxy-anions were less mobile from the co-fired fly ashes than from the normally-fired fly ash materials.

14CO 2 dispersion around two PWR nuclear power plants in Brazil

Atmospheric air samples were taken within 3 km from power plants encompassing five different distances and wind directions. Samples were taken between 2002 and 2005 aiming to evaluate the environmental 14C enrichment due to the operation of Brazilian nuclear power plants. The sampling system consisted of a pump connected to a trapping column filled with a 3 M NaOH solution. The trapped CO 2 was analyzed for 14C by using a single stage accelerator mass spectrometry (SSAMS). All sampling sites revealed measurable 14C excess values. The maximum excesses were of 15 and 14 mBq/m 3 for sampling sites placed at NE of the power plants, which is the main wind direction in the area. The mean excesses values were 12 mBq/m 3 to the NE direction, 8 mBq/m 3 to the E, 10 mBq/m 3 to the N, 8 mBq/m 3 to the WNW and 7 mBq/m 3 to the W direction (increasing distances from NE to W). Compared to other Light Water Reactors (LWR) data, these means' values are significantly higher than the average worldwide reported value of 3 mBq/m 3. Available data indicate that the observed values are not related to 14C emission by the power plants vent stack. Other factors, such as topography, seem to have an important role because it affects wind dispersion thus favoring 14C accumulation in the sampled area. Moreover, the high elevations around the power plants enhance the chances to measure high values of 14C since the plume can be intercepted before it is drawn to the ground. Modeling of the plume has shown that its dispersion does not follow a Gaussian model and that agreement between atmospheric CO 2 and vegetation 14C activities occurs only for sampling sites placed at NE of the power plants.

Biofouling e biodeterioração química de argamassa de cimento portland em reservatório de usina hidroelétrica

Last decade Brazilian rivers experimented progressive biofouling of Limnoperna fortunei communities and Cordylophora caspia hydroids. The microhabitat is so favorable that in around 1.5 years L. fortunei increased from 0.39 to nearby 149,000 units/m2. Ten Portland cement mortar samples were produced with 1: 3.5: 0.4 dosages and installed for 1 year at Salto Caxias Brazilian Power Plant reservoir in 0.5 m and 1.0 m deep to investigate the biofouling influence on hydraulic civil structures. SEM, EDS, visual investigation and XRF results indicate none direct chemical interrelationships between L. fortunei and the mortar samples. However C. caspia diminished the mortar surface resistance and caused cement paste leaching.

Excelência no gerenciamento de construção de hidrelétrica de grande porte

Este trabalho verifica a aplicação das práticas gerenciais descritas no PMBOK, na gestão da construção de duas hidrelétricas de grande porte no Brasil. Utilizando o método do estudo de caso, esta pesquisa permitiu a obtenção dos dados práticos referentes a 23 proposições selecionadas do PMBOK. O levantamento de campo, realizado em 2005, ocorreu por observação direta, coleta de documentos, entrevistas estruturadas e abertas. Visando à obtenção de dados sob perspectivas diferentes, foram selecionados para entrevista não só os gestores atuantes nos canteiros de obras dos dois projetos, mas também os executivos da matriz e um consultor. Os resultados atestam que as práticas de gerenciamento adotadas pelos gestores dos dois projetos, caso objeto deste estudo, são aderentes às proposições do PMBOK. Obteve-se também a descrição das práticas de gerenciamento de tempo, custo, comunicação e outras práticas relevantes não contempladas pelo modelo PMBOK. O trabalho permite recomendar que os referenciais relativos a caminho crítico, orçamento e flexibilização das proposições do PMBOK estão entre os aspectos prioritários a serem investigados em futuras pesquisas sobre gerenciamento de projetos.

Chemical characterization of feed coals and combustion-by-products from Brazilian power plants

In this work, coal, bottom ash, and fly ash from coal-fired power plants located in the South of Brazil (Figueira/PR, Capivari de Baixo/SC, Candiota/RS, São Jerônimo/RS, and Charqueadas/RS) were evaluated and compared, mainly with respect to chemical composition. Major elements (Si, Al, Fe, P, Ca, Mg, Ti, Na, and K) concentrations were determined by X-ray fluorescence spectrometry (XRF), whereas the concentrations of minor and trace elements (Ag, As, Au, B, Ba, Be, Cd, Ce, Co, Cr, Cu, Ga, Ge, Li, Mn, Mo, Nb, Ni, Pb, Pt, Rb, Sb, Se, Sr, Ti, U, V,Y, Zn, and Zr) were determined by inductively coupled plasma mass spectrometry (ICP-MS) and/or inductively coupled plasma atomic emission spectrometry (ICP-OES). Mercury was determined by cold vapour atomic absorption spectrometry (CV-AAS). It was observed that the concentrations of minor and trace elements (mainly As, Cd, Mo, Pb, TI, U, Zn, and Hg) are, in general, highest in the coal and combustion-by-products from Figueira/PR, with statistical analysis showing that the coal and fly ash from Figueira/PR are significantly different from the other areas. Leaching tests using water and mechanical agitation demonstrated that the yield of minor and trace elements extraction from fly ash was higher than in bottom ash. The extraction of As, B, Ge, Li, Mo, Se, and Sr by water was typically in the range of 5 to 50%, whereas the other elements showed lower leaching. The pH of the leachates of both fly and bottom ashes is alkaline (average pH ranging from 8.04 to 10.0), with the exception of the bottom ash from Candiota (the average pH is 5.34).

Maximizing wear resistance of balls for grinding of coal

A Brazilian power plant consumes mineral coal with high ash contents to feed four turbines to generate 450 MW. Four ball mills, 4.2 m in diameter, are fed with crushed coal to deliver the material ground to sizes less than 0.075 μm. High wear rates were observed when using forged high-carbon steel balls. A pilot-plant ball mill, with a 0.01 m 3 chamber, was used to perform wear tests, comparing the original ball material and seven grades of high chromium cast irons, grinding the same coal as used in the industrial plant. Test pieces were 60-mm balls with different chemical compositions and heat treatments. Balls were weighed after 10-h grinding periods, for up to 7 periods. The mass losses were converted to equivalent diameter losses and regression straight lines were obtained, showing the wear rates of the materials. The wear rates of the cast irons with 25–30% Cr were only 10–20% of the wear rate of the forged steel. Cast irons with 15–18% Cr wore at around 50% of the rate of the steel. Analyses of the coal ashes showed around 40% of quartz as 10–20 μm particles. Examination of the surface of worn balls showed that these particles caused the wear.

Radioactivity of coal and ashes from Figueira coal power plant in Brazil

The Figueira coal-fired power plant (CFPP) is among the Brazilian CFPP which presents higher uranium concentration. Gamma-ray spectrometry was used to determine 238U, 226Ra, 210Pb, 232 Th and 40K contents in pulverized coal, furnace bottom ash and fly ash samples. The natural radionuclide concentrations in pulverized coal ranged from 813 to 2609 Bq . kg-1 for U series and from 22 to 40 Bq . kg-1 for 232 Th. The fly ash fraction gave concentrations ranging from 1442 to 14641 Bq . kg-1, for uranium series. The same enrichment factor was observed for 238U, 226Ra and 232 Th. Only 210Pb and stable Pb presented a high enrichment factor for the last stage filter fly ash. The concentration of the uranium series found in the ashes is close to the limit adopted by the Brazilian guideline (CNEN-NN-4.01).22 Therefore, it is advisable to evaluate the environmental impact of the installation.

Evaluation of radionuclides concentration in Brazilian coals

Raw material samples of coal used by the main power plants in Brazil (RS; SC; PR) were evaluated. Radiological relevant radionuclides of the natural series, such as 238U, 228Ra, 226Ra, 210Pb and 40K were analyzed by direct gamma spectrometry. The results showed that the uranium concentration in coal from (PR) was at least three times higher than concentration found in other coal samples in Brazil (RS and SC). In spite of the high uranium concentration in the PR coal, the small (10 MW e) local power plant currently operating in (PR) produced low amount of ashes, however more detailed studies should be done for the new power plant (140 MW e) in project.