bluuebunny/crossref_metadata_2025 huggingface dataset:
Capture of SO2 by limestone in a 71 MWe pressurized fluidized bed boiler
Authors: Shimizu Tadaaki , Peglow Mirko , Yamagiwa Kazuaki , Tanaka Masato , Sakuno Shinichi , Misawa Nobuhiro , Suzuki Nobuyuki , Veda Hachiro , Sasatsv Hiroshi , Gotou Hideki
Published: July 2007

A 71 MWe pressurized fluidized bed coal combustor was operated. A wide variety of coals were burnt under fly ash recycle conditions. Limestone was fed to the combustor as bed material as well as sorbent. The emission of SO^ and limestone attrition rate were measured. A simple mathematical model of SO? capture by limestone with intermittent solid attrition was applied to the analysis of the present experimental results. Except for high sulfur fuel, the results of the present model agreed with the experimental results.
Experimental studies and economic considerations on a thermosolar pilot system destined for house temperature maintenance
Authors: Luminosu Ioan
Published: July 2007

The "Politehnica" University of Timisoara has built a thermo solar system implemented on the ground floor and first floor of a building. The system is made up of solar water collectors, an air-water heat exchanger, a bedrock heat accumulator and a minimal thermal loss enclosure. The statistical processing of the measurements performed during spring and autumn 2000 resulted in determining the average features of the system and in the evaluation of its efficiency in maintaining the enclosure's temperature, enclosure assimilated to a living space. The efficiency of the system is 30%. During spring and autumn, the enclosure's temperature is maintained at a level of 20 ?C by solar and electrical gain, with a 60% solar energy ratio. With the help of the state in promoting solar energy, the investment's writing-off period would be 18.5years, and the user's benefit, B = 21176.
Numerical modeling of disperse material evaporation in axisymmetric thermal plasma reactor
Authors: Stefanovic Predrag , Cvetinovic Dejan , Zivkovic Goran , Oka Simeon , Pavlovic Pavle
Published: July 2007

A numerical 3D Euler-Lagrangian stochastic-deterministic (LSD) model of two-phase flow laden with solid particles was developed. The model includes the relevant physical effects, namely phase interaction, panicle dispersion by turbulence, lift forces, particle-particle collisions, particle-wall collisions, heat and mass transfer between phases, melting and evaporation of particles, vapour diffusion in the gas flow. It was applied to simulate the processes in thermal plasma reactors, designed for the production of the ceramic powders. Paper presents results of extensive numerical simulation provided (a) to determine critical mechanism of interphase heat and mass transfer in plasma flows, (b) to show relative influence of some plasma reactor parameters on solid precursor evaporation efficiency: 1 - inlet plasma temperature, 2 - inlet plasma velocity, 3 - particle initial diameter, 4 - particle injection angle a, and 5 - reactor wall temperature, (c) to analyze the possibilities for high evaporation efficiency of different starting solid precursors (Si, Al, Ti, and B2O3 powder), and (d) to compare different plasma reactor configurations in conjunction with disperse material evaporation efficiency.
Fluidized bed combustion research and development in Sweden: A historical survey
Authors: Leckner Bo.
Published: July 2007

A survey is made on research and development related to fluidized bed boilers in Sweden during the past two decades, where several Swedish enterprises took part: Generator, G?taverken, Stal Laval (ABB Carbon) and Studsvik. Chalmers University of Technology contributed in the field of research related to emissions, heat transfer and fluid dynamics, and some results from this activity are briefly summarized.
Experimental studies and economic considerations on a living space heated through passive solar gain and through electric power
Authors: Luminosu Iona
Published: July 2007

The Trombe wall, of an area AT = 8.8 m, built on the southern facade of a room, heats the accommodation during the transition months, complementary to electric power. The statistical processing of the experimental data led to a global quantitative image of the wall?s behavior during the average day of the months March, April, September, and October 1999. The inner climate parameters are: tint = = 21 ?C, trad = 17.9 ?C, troom= 19.5 ?C, j= 35-70%, E ?80 + 120 lx. The thermal comfort factor is B = -0.325. These values insure a room?s comfort close to the optimal one prescribed by the hygienists. The heliothermal conversion?s efficiency is hT = 10.4%. The proportion of heat supplied by the wall in the entire energy required by the room is hheat = 45.8%. The wall?s specific cost is Pu = 24.9 ? /m. The write-off period of the initial investment is n = 53 years. The development of passive solar architecture in the Euro-region Danube-Cris-Mures-Tisa which includes the town of Timisoara (45? north, 22? east), was proven feasible by the experiments from both the energy and the economical point of view.
Experimental investigation of a flow around a sphere
Authors: Bakic Vukman
Published: July 2007

This paper presents the experimental results for the flow around a sphere: a smooth sphere in flow with low inlet turbulence, a sphere with trip wire and a sphere in flow with high free stream turbulence, at sub critical Reynolds number. The mean velocity field and the turbulence quantities are obtained using laser-Doppler anemometry. Comparison of velocity field and turbulence character is tics for different flow configuration are given.
A method for stability analysis of the non-linear heat and mass transfer processes
Authors: Boyadjiev Christo , Doichinova Maria
Published: July 2007

Many systems with non-linear heat and mass transfer processes might be unstable at certain conditions. Small disturbances might bring out them of their equilibrium state, after which they achieve itself to a new stable state. The method developed here concerns a non-linear analysis of hydrodynamic stability of the systems with intensive heat and mass transfer. It al lows the determination of the kinetic energy distribution between the main flow and the disturbance, when the equilibrium value of the disturbance amplitude is determined.
Biomass fast pyrolysis
Authors: Bridgewater Anthony
Published: July 2007

Bioenergy is now accepted as having the potential to provide the major part of the projected renewable energy provisions of the future. Fast pyrolysis is one of the three main thermal routes, with gasification and combustion, to providing a useful and valuable biofuel. It is one of the most recent renewable energy processes to have been introduced and offers the advantages of a liquid product bio-oil that can be readily stored and trans ported, and used as a fuel, an energy carrier and a source of chemicals. Fast pyrolysis has now achieved commercial success for production of some chemicals, liquid fuel and electricity. Bio-oils have been success fully tested in engines turbines and boilers, and have been upgraded to high quality hydrocarbon fuels although at a presently unacceptable energetic and financial cost. This review concentrates on the technology of pyrolysis and applications for the liquid product. The basic pyrolysis process and the characteristics of the main liquid product bio-oil are first summarized followed by a review of applications for bio-oil. The main technical and non-technical barriers to implementation are identified.
Parallel and series-reaction mechanisms of wood and char combustion
Authors: Branca Carmen , di Blasi
Published: July 2007

Thermo gravimetric curves in air of beech wood and char, obtained from conventional pyrolysis of beech wood at a laboratory scale, have been re-examined using different kinetic models. Multi-step reaction mechanisms consisting of either four (wood) or two (char) reactions are needed for accurate predictions of weight loss curves. In the case of wood, three reactions are linear in the reactant mass fraction whereas the fourth step presents a power-law dependence. A linear reaction for devolatilization and a non-linear reaction for combustion are used for the weight loss curves of char. It has been found that activation energies and pre-exponential factors are in variant with series or parallel reactions, providing changes in the stoichiometric coefficients. Further more, the activation energies of the two reactions occurring at higher temperatures in the four-step mechanism (wood) and those of the two-step mechanism (char) are the same. Thus pre-exponential factors and reaction order take into account variations in the char reactivity derived from different pyrolysis conditions.
Experimental study of co-pyrolysis of polyethylene/sawdust mixtures
Authors: Berrueco Cesar , Ceamanos Jesús , Esperanza Ernesto , Mastral Francisco
Published: July 2007

A study of the behavior of the thermal decomposition of mixtures of biomass and thermoplastics, such as polyethylene, is of interest for processes for the thermal recovery of industrial and urban wastes such as pyrolysis or gasification. No solid residue is formed during the thermal degradation of pure polyethylene. However, the addition of biomass, which generates char can vary the product distribution and increase the heating value of the gas obtained. A study of the thermal degradation of pine sawdust, polyethylene and mixtures of polyethylene and pine sawdust has been carried out in a fluidized bed reactor. Experiments were carried out at five different temperatures: 640, 685, 730, 780, and 850 ?C. The yields and composition of the derived oil, wax, and gas were determined. The addition of polyethylene increases the gas production and decreases the production of waxes and liquids for the different temperatures tested. The main gases produced from the co-pyrolysis process were, at low temperatures, carbon monoxide ethylene, carbon dioxide, propylene, butadiene, methane and pentadiene while at high temperatures the gas composition changed drastically, the main components being carbon monoxide (more than 33 wt.%), ethylene, methane benzene and hydrogen. The analysis of the liquid fraction shows a decrease of the concentration of oxygenated and aliphatic compounds.
Effects of biomass on dynamics of combustion in circulating fluidized beds
Authors: Tourunen Antti , Häsä Heidi , Pitsinki Juha , Jegoroff Mikko , Saastamoinen Jaakko , Hämäläinen Jouni
Published: July 2007

Fluidized bed technology is very suitable for the combustion of biomass Nevertheless substitution of coal with biomass affects boiler operation and especially dynamics and controllability. Non-homogeneity of biomass and fuel feeding disturbances cause process instability, such as variations in temperatures and pressures, which reduce lifetime of equipment and structures. Because of process instability higher air coefficient must be used in order to avoid CO emissions, which is not economical. Combustion profiles for coal, wood and peat, measured at the VTT Processes Pilot circulating fluidized bed reactor, have been compared. Process stability and char inventories have been studied by the measurements and the model. Biofuel are usually very reactive and their combustion profiles are quite different compared to coals. Because of high reactivity and low char content combustion process with biofuel is very sensitive for fuel feeding. Also low char inventory effect on load changes combined with combustion profile that differs from coals. Because of different combustion profile heat transfer can be a limiting factor in load changes despite the high reactivity and fast oxygen response.
Utilization of gases from biomass gasification in a reforming reactor coupled to an integrated planar solid oxide fuel cell: Simulation analysis
Authors: Costamagna Paola , Cerutti Fabio , di Felice , Collins Robert
Published: July 2007

One of the high-efficiency options currently under study for a rational employment of hydrogen are fuel cells. In this scenario, the integrated planar solid oxide fuel cell is a new concept recently proposed by Rolls-Royce. The basic unit of a modular plant is the so called "strip", containing an electro-chemical reactor formed by a number of IP-SOFC modules, and a reforming reactor. For a better under standing of the behavior of a system of this kind, a simulation model has been set up for both the electrochemical reactor and the reformer; both models follow the approach typically employed in the simulation of chemical reactors, based on the solution of mass and energy balances. In the case of the IP-SOFC electro chemical reactor, the model includes the calculation of the electrical resistance of the stack (that is essentially due to ohmic losses, activation polar is action and mass transport limitations), the mass balances of the gaseous flows, the energy balances of gaseous flows (anodic and cathodic) and of the solid. The strip is designed in such a way that the reaction in the reforming reactor is thermally sustained by the sensible heat of the hot air exiting the electrochemical section; this heat exchange is taken into account in the model of the reformer, which includes the energy balance of gaseous flows and of the solid structure. Simulation results are reported and discussed for both the electrochemical reactor in stand-alone configuration (including comparison to experimental data in a narrow range of operating conditions) and for the complete strip.
Production of dry wood chips in connection with a district heating plant
Authors: Yrjölä Jukka
Published: July 2007

Moisture and its variation in wood chips make the control of burning in small scale heating appliances difficult resulting in emissions and loss of efficiency. If the quality of wood chips would be better, i. e. dried and sieved fuel with more uniform size distribution would be avail able, the burning could be much cleaner and efficiency higher. In addition higher power out put could be obtained and the investment costs of the burning appliances would be lower. The production of sieved and dried wood chip with good quality could be accomplished in connection with a district heating plant. Then the plant would make profit, in addition to the district heat, from the dried wood chips sold to the neighboring buildings and enterprises sep a rated from the district heating net using wood chips in energy production. The peak power of a district heating plant is required only a short time during the coldest days of the winter. Then the excess capacity during the milder days can be used as heat source for drying of wood chips to be marketed. Then wood chips are sieved and the fuel with best quality is sold and the reject is used as fuel in the plant it self. In a larger district heating plant, quality of the fuel does not need to be so high In this paper the effect of moisture on the fuel chain and on the boiler is discussed. Energy and mass balance calculations as a tool of system design is described and the characteristics of proposed dry chips production method is discussed.
On peculiar property of the velocity fluctuations in wall-bounded flows
Authors: Jovanovic Jovan , Hillerbrand Rafaela
Published: July 2007

Statistical analysis of the velocity fluctuations is performed for the near-wall region of wall-bounded flows. By demanding that the small-scale part of the fluctuations satisfies constraints imposed by local ax symmetry it was found that the small scales must be entirely suppressed in the near-wall region. This major conclusion is well supported by all available data from direct numerical simulations.
The effect of polymers on the dynamics of turbulence in a drag reduced flow
Authors: Jovanovic Jovan , Frohnapfel Bettina , Pashtrapanska Mira , Durst Franz
Published: July 2007

An experimental investigation of a polymer drag reduced flow using state-of-the-art laser-Doppler anemometry in a refractive index-matched pipe flow facility is reported. The measured turbulent stresses deep in the viscous sublayer are analyzed using the tools of invariant theory. It is shown that with higher polymer concentration the anisotropy of the Reynolds stresses increases. This trend is consistent with the trends extracted from DNS data of non-Newtonian fluids yielding different amounts of drag reduction. The interaction between polymer and turbulence is studied by considering local stretching of the molecular structure of a polymer by small-scale turbulent motions in the region very close to the wall. The stretching process is assumed to re-structure turbulence at small scales by forcing these to satisfy local axisymmetry with invariance under rotation about the axis aligned with the main flow. It is shown analytically that kinematic constraints imposed by local axisymmetry farce turbulence near the wall to tend towards the one-component state and when turbulence reaches this limiting state it must be entirely suppressed across the viscous sublayer. Based on this consideration it is suggested that turbulent drag reduction by high polymers resembles the reverse transition process from turbulent to laminar. Theoretical considerations based on the elastic behavior of a polymer and spatial intermittency of turbulence at small scales enabled quantitative estimates to be made for the relaxation time of a polymer and its concentration that ensure maximum drag reduction in turbulent pipe flows, and it is shown that predictions based on these are in very good agreement with available experimental data.
Friction factors and internal flow length scales of gas-solid magnetically stabilized beds in axial fields: Scaling and applications to bed-to-surface heat transfer
Authors: Hristov Jordan
Published: July 2007

Friction factors and internal flow length scales of gas-solid magnetically stabilized beds are discussed. Pressure drop and expansion data of beds stabilized by axial magnetic fields are used. The concept of a variable friction factor of fluid-driven deformable packed bed is discussed. Scaling relationships of the internal flow length scale and the bed overall porosity are developed through three approaches: (1) fluidization approach concerning a length scale proportional to the particle size, (2) packed bed approach based on a hydraulic diameters as a length scale, and (3) porous media approach based on the Forchheimer equation. The main result is that the bed length scale ~e", irrespective of the model used, where n is the exponent of the Richardson-Zaki scaling law. These scaling estimates are used to explain the magnetic field effects on bed-to-surface heat transfer coefficients.
A new multifield finite element method in steady state heat analysis
Authors: Mijuca Dubravka , Ziberna Ana , Medjo Bojan
Published: July 2007

A new original primal-mixed finite element approach and related hexahedral finite element HC:T/q for the analysis of behavior of solid bodies under thermal loading is presented. The essential contributions of the present approach is the treatment of temperature and heat flux as fundamental variables that are simultaneously calculated, as well as capability to introduce initial and prescribed temperature and heal flux. In order to minimize accuracy error and enable introductions afflux constraints, the tensorial character of the present finite element equations is fully respected. The proposed finite element is subjected to some standard benchmark tests in order to test convergence of the results, which enlighten the effectiveness and reliability of the approach proposed.
Solid recovered fuel as coal substitute in the electricity generation sector
Authors: Kakaras Emmanuel , Grammeus Panagiotis , Agraniotis Michails , Derichs Willy , Schiffer Hans-Peter , Maier Jörg , Hilber Thomas , Glorius Thomas , Becker Uwe
Published: July 2007

According to the 1999/31 EC Directive, municipal solid waste should not be disposed for landfill from 2005. In this way, more environmental friendly waste management options are promoted towards the volume reduction and limitation of negative consequences. In this context, attention is focused on the utilization of solid recovered fuels derived from the waste treatment as coal substitute in large-scale power plants. Such activities are realized within an EU-funded project RECOFUEL, in which the solid recovered fuels co-combustion with brown coal is demonstrated in two commercial-scale PF-boilers at R WE Power's power plant site in Weisweiler, Germany. During testing the thermal share of solid recovered fuels in the overall thermal input was adjusted to some 2%, resulting into a feeding rate of about 2 x 12.5 tons per hour. NTUA-LSB in cooperation with IVD-University of Stuttgart, Germany, is responsible for the boiler measurements and the characterization of boilers operational behavior. Among the main activities are the technology transfer of co-combustion practice in the Balkan countries and the perspectives of its future application in the Greek region, with respect to the special characteristics of the Greek brown coal and municipal solid waste. Co-combustion tests of brown coal and solid recovered fuels, that have been taken place up to now, have been successfully performed and the strict European emission limits are kept. The waste quantities in Greece that can be utilized are estimated in 200,000 Mg/year while their utilization in existing thermal plants is expected to bring savings of 3% lignite use and avoidance of up to 200,000 Mg CO2 per year.
Application of inverse concepts to drying
Authors: Kanevce Ljubica , Kanevce Gligor , Dulikravich George
Published: July 2007

This paper deals with the application of inverse approaches to estimation of drying body parameters. Simultaneous estimation of the thermo physical properties of a drying body as well as the heat and mass transfer coefficients, by using only temperature measurements, is analyzed. A mathematical model of the drying process has been developed, where the moisture content and temperature fields in the drying body are expressed by a system of two coupled partial differential equations. For the estimation of the unknown parameters, the transient readings of a single temperature sensor located in an infinite flat plate, exposed to convective drying, have been used. The Levenberg-Marquardt method and a hybrid optimization method of minimization of the least-squares norm are used to solve the present parameter estimation problem. An analysis of the influence of the drying air velocity, drying air temperature, drying body dimension, and drying time on the thermophysical properties estimation, that enables the design of the proper experiments by using the so-called D-optimum criterion was conducted. In order to perform this analysis, the sensitivity coefficients and the sensitivity matrix determinant were calculated for the characteristic drying regimes and the drying body dimensions.
Identification of heat and mass transfer processes in bread during baking
Authors: Zheleva Ivanka , Kambourova Vesselka
Published: July 2007

A mathematical model representing temperature and moisture content in bread during baking is developed. The model employs the coupled partial differential equations proposed by Luikov. Dependences of mass and thermal properties of dough on temperature and moisture content are included in the model. Resulting system of non-linear partial differential equations in time and one space dimension is reduced to algebraic system by applying a finite difference numerical method. A numerical solution of the model equations is obtained and simultaneous heat and moisture transfer in dough during baking is predicted. The changes of temperature and moisture content during the time of the process are graphically presented and commented.
Stability of two superposed viscous-viscoelastic fluids
Authors: Kumar Pardeep , Lal Roshan
Published: July 2007

The Rayleigh-Taylor instability of a Newtonian viscous fluid overlying a Rivlin-Ericksen viscoelastic fluid is considered. Upon application of normal mode technique, the dispersion relation is obtained. As in both Newtonian viscous-viscous fluids the system is stable in the potentially stable case and unstable in the potentially unstable case, this holds for the present problem also. The behavior of growth rates with respect to kinematic viscosity and kinematic viscoelasticity parameters are examined numerically and it is found that both kinematic viscosity and kinematic viscoelasticity have stabilizing effect.
Sustainable energy path
Authors: Yamamoto Hiromi , Yamaji Kenji
Published: July 2007

The uses of fossil fuels cause not only the resources exhaustion but also the environmental problems such as global warming. The purposes of this study are to evaluate paths to ward sustainable energy systems and roles of each renewable. In order to realize the purposes, the authors developed the global land use and energy model that figured the global energy supply systems in the future considering the cost minimization. Using the model the authors conducted a simulation in C30R scenario, which is a kind of strict CO2 emission limit scenarios and reduced CO2 emissions by 30% compared with Kyoto protocol forever scenario, and obtained the following results. In C30R scenario bio energy will supply 33% of all the primary energy consumption. How ever, wind and photo voltaic will supply 1.8% and 1.4% of all the primary energy consumption, respectively, because of the limits of power grid stability. The results imply that the strict limits of CO2 emissions are not sufficient to achieve the complete renewable energy systems. In order to use wind and photo voltaic as major energy resources we need not only to reduce the plant costs but also to develop unconventional renewable technologies. .
Constructal theory of design in engineering and nature
Authors: Bejan Adrian
Published: July 2007

This is a brief introduction to an engineering theory on the origin and generation of geometric form in all flow systems: the animate, the in animate and the engineered. The theory is named constructal, and is based on the thought that it is natural for cur rents to construct for them selves in time paths of greater flow access. It is shown that this process of flow path optimization can be reasoned on the basis of principle: the maximization of global performance subject to finite-size constraints. One example is the generation of tree-shaped flow pat terns, as paths of least resistance between one point (source, sink) and an infinity of points (area, volume), as in the circulatory, respiratory and nervous systems. Another is the generation of regular spacing's in heat generating volumes, such as swarms of honey - bees. The optimized tree-flow geometries ac count for allometric laws, e. g., the relation ship between the total tube contact area and the body size, the proportionality between metabolic rate and body size raised to the power 3/4, the proportionality between breathing and heart beating times and body size raised to the power 1/4, and the proportionality between the cruising speed of flying bodies (in sects, birds, air planes) and body mass raised to the power 1/6. The optimized flow structures constitute robust designs, and robustness improves as the complexity of the system increases. Flow architectures that are more efficient look more natural.
Performance evaluation of tube-in-tube heat exchangers with heat transfer enhancement in the annulus
Authors: Zimparov Ventsislav , Penchev Plamen , Meyer Joshua
Published: July 2007

Different techniques as angled spiraling tape inserts, a round tube in side a twisted square tube and spiraled tube in side the annulus have been used to enhance heat transfer in the annulus of tube-in-tube heat exchangers. The heat transfer enhancement in the shell can be supplemented by heat transfer augmentation in tubes using twisted tape inserts or micro-finned tubes. The effect of the thermal resistance of the condensing refrigerant could also be taken into consideration. To assess the benefit of using these techniques extended performance evaluation criteria have been implemented at different constraints. The decrease of the entropy generation can be combined with the relative in crease of the heat transfer rate or the relative reduction of the heat transfer area to find out the geometrical parameters of the tubes for optimal thermodynamics performance. The results show that in most of the cases considered, the angled spiraling tube insert technique is the most efficient.
Constructal theory and flow architectures in living systems
Authors: Reis Antonio , Miguel Ferreira
Published: July 2007

We apply Constructal theory to the study of the flow structure of the human respiratory tree. We show that the flow architecture that would per form oxygenation of the blood and removal of carbon dioxide best, i. e. with lowest resistance, would be composed of a channel system with 23 bifurcation with a diffusive zone (alveolus) at the end. As this tree matches the human respiratory tree we conclude that nature has optimized it in time. Two constructal relation ships also emerge: (1) the length l, de fined by the ratio of the square of the airway diameter to its length, is constant for all individuals of the same species, and (2) the length ? is related to the volume of the space al located to the respiratory process, to the length of the respiratory tree and to the area of the alveoli, and determines univocally the branching level of the respiratory tree.
Entropy-cycle method for analysis of refrigeration machine and heat pump cycles
Authors: Morosuk Tatiana , Nikulshin Ruslan , Morosuk Larisa
Published: July 2007

Real and ideal cycles of any complexity can be compared through the definition of the irreversibility's and ways of their minimization in the thermodynamic analysis. The paper considers the use of entropy-cycle method for thermodynamic analysis of refrigerating machines and heat pumps. Using this method preconditions of practical use for analysis, synthesis, and optimization have been created. The methodology of the entropy-cycle method can be use in many areas of the scientific work and educational process.
The energy policy of Greece
Authors: Kalampalikas Nikos , Pilavachi Petros
Published: July 2007

This paper presents the energy policy of Greece and deals with four energy sectors i. e. petroleum, natural gas, electricity/lignite, and renewable energy sources. Each of these sectors is described and its present state is presented. The Greek national strategy in each energy sector is examined while its international policy is discussed. The objectives of the new energy strategy that Greece is about to introduce are also presented. .
Release of arsenic during the carbonisation of CCA-treated wood on a laboratory and pilot scale
Authors: Zandersons Janis , Zhurinsh Aivars , Dobele Galina , Spince Baiba , Tardenaka Ausma , Rizhikovs Janis
Published: July 2007

The release of arsenic during pyrolysis of CCA(chromated copper arsenate)-treated wood starts at a temperature below 327 ?C, but up to 600 ?C only 30-40% of the arsenic initially present in the wood is volatilised. The changes of heating rate, wood moisture, degree of the comminution and methods of pyrolysis (fixed bed or mechanically pushed and loosened bulk of chips) do not substantially change the situation. The release of arsenic can be eliminated or strongly reduced by use of carbonisation catalysts. The ways and means of metals regeneration or practical use of this contaminated charcoal are still to be elucidated. A substantial decrease of the As, Cr, and Cu content in charcoal from 2800-5550 ppm, 3700-14300 ppm, and 3500-8800 ppm, to 61 ppm, 1014 ppm, and 282 ppm, respectively, was achieved by carbonisation of the previously leached wood specimens. The leachability of CCA-salts from the wood treated with diluted sulphuric acid is good, and the amount of the leached-out metals exceeds 90-95%. Ultrasound treatment improves the leachability, although the effect is not high enough to achieve the full elimination of metals, especially chromium, to meet the concentration levels in charcoal set by legislation.
Novel concepts for near-zero emissions IGCC power plants
Authors: Kakaras Emmanouil , Doukelis Aggelos , Giannakopoulos Dionysios , Koumanakos Antonios
Published: July 2007

The paper aims in examining and evaluating the state-of-the-art in technological concepts towards zero-emission coal-fired power plants. The discussion is based on the evaluation of a novel concept dealing with the carbonation-calcination process of lime for CO2 capture from coal-fired power plants, compared to the integration of CO2 capture in an Integrated Gasification Combined Cycle power plant. Results from thermodynamic simulations dealing with the most important features for CO2 reduction are presented. Preliminary economic considerations are made, taking into account investment and operating costs, in order to assess the electricity cost related to the two different technological approaches. The cycle calculations were performed with the thermodynamic cycle calculation software ENBIPRO (ENergie-BIllanz-PROgram), a powerful tool for heat and mass balance solving of complex thermodynamic circuits, calculation of efficiency, exergetic and exergoeconomic analysis of power plants. The software code models all pieces of equipment that usually appear in power plant installations and can accurately calculate all thermodynamic properties at each node of the thermodynamic circuit, power consumption of each component, flue gas composition etc. [1]. The code has proven its validity by accurately simulating a large number of power plants and through comparison of the results with other commercial software. .
Comparison of oxygen carriers for chemical-looping combustion
Authors: Johansson Marcus , Mattisson Tobias , Lyngfelt Anders
Published: July 2007

Chemical-looping combustion is a combustion technology with inherent separation of the greenhouse gas CO2. This technique involves combustion of fossil fuels by means of an oxygen carrier which transfers oxygen from the air to the fuel. In this manner a decrease in efficiency is avoided for the energy demanding separation of CO2 from the rest of the flue gases. Results from fifty oxygen carriers based on iron-, manganese- and nickel oxides on different inert materials are compared. The particles were prepared using freeze granulation, sintered at different temperatures and sieved to a size 125-180 mm. To simulate the environment the particles would be exposed to in a chemical-looping combustor, reactivity tests under alternating oxidizing and reducing conditions were performed in a laboratory fluidized bed-reactor of quartz. Reduction was performed in 50% CH4/50% H2O while the oxidation was carried out in 5% O2 in nitrogen. In general nickel particles are the most reactive, followed by manganese. Iron particles are harder but have a lower reactivity. An increase in sintering temperatures normally leads to an increase in strength and decrease in reactivity. Several particles investigated display a combination of high reactivity and strength as well as good fluidization behavior, and are feasible for use as oxygen carriers in chemical-looping combustion.
Applications of oxygen for NOx control and CO2 capture in coal-fired power plants
Authors: Châtel-Pélage Fabienne , Varagani Rajani , Pranda Pavol , Perrin Nicolas , Farzan Hamid , Vecci Stanley , Yongqi LU. , Chen Scott , Rostam-Abadi Massoud , Bose Arun
Published: July 2007

Two promising combustion modification approaches applicable to pulverized coal fired boilers are presented: "Oxygen-Enriched Combustion" (OEC) for NOx control and "Oxy-Combustion" (PC-OC) for CO2 capture. Oxygen-enriched air rather than air is used as an oxidizer in the OEC technology. Unlike flue gas treatment technologies, OEC directly impacts the NOx formation process by significantly reducing the conversion of coal bound nitrogen to NOx. Pilot-scale and full-scale tests have shown 20 to 30% NOx reduction from an optimized staged-air baseline. In addition to the overall cost competitiveness and the reduced capital requirements, other significant advantages of the O2-enriched technology vs. existing low NOx technologies are presented. The PC-OC technology is shown as a cost-effective technology for CO2 capture from existing or new coal-fired power plants. Pure oxygen diluted in recycled flue gases is used as an oxidizer. The process has been successfully demonstrated and extensively characterized at pilot-scale level (1.5 MWt). The tests have shown substantial benefits of the PC-OC technology, in terms of NOx reduction (60-70% from air-baseline), overall plant efficiency, etc. The cost effectiveness of this capture technology compared to competitive amine scrubbing technology was investigated. The cost of CO2 avoided was around $36/ton for the new PC-OC cases, about $48/ton on a retrofit PC-OC case, which is about 25 to 40% cheaper than the amine scrubbing system. Those numbers were calculated for sub-critical units and include the cost of CO2 compression up to 80 bar. .
An increase of hydro-aggregate's installed power and efficiency factor before the revitalization phase
Authors: Petrovic Dragan , Vidakovic Veljko , Ciric Zoran , Stojkovic Sinisa , Benisek Miroslav , Bozic Ivan , Dragic Milorad , Zeljic Milorad
Published: July 2007

The revitalization of hydro-aggregates should be performed before the life-time expiry of most their parts. But, as in our practice aggregates have been under exploitation much longer then theoretical life-time advices (40, even 50 years), there is a need to estimate the equipment's condition through more sophisticated monitoring, providing the maximum level of safety and availability with minimum investment expenses, before the revitalization finally takes place. That estimation is based on appropriating calculations and measurements needed to take the competent decision. Results of that analysis can be also useful for estimation of the aggregate's power and parameters after the revitalization. In this paper the results of appropriate calculations and measurements for the Hydropower station HE Zvornik are given. .
Adaptive computer supported surveillance-management model of dewatering system at coal open pit mine
Authors: Vujic Slobodan
Published: July 2007

The lignite open pit mine of "Drmno", Mining Basin Kostolac, deals within the framework of the Electric Power Industry of Serbia. The imperative condition for coal exploitation in this deposit is closely connected to the protection of open pit mine against ground waters which is based on the complex, spatial and timely non-stationary system of about 200 drainage wells, having the total installed power of pumps of approximately 2 MW. This system pumps out approximately 15.000,000 m3 water annually. The already existing manner of monitoring and management of the work of wells neither supports in real time the guiding of the process of dewatering according to the optimum regime and enables precise monitoring of electric power consumption nor monitoring the capacity and time efficiency of the system and does not register and does not diagnosis stoppages. The system also fails to enable prognosis and preventive undertaking the corrective measures, monitoring the reliability work of system components, precise monitoring of operation costs, control of costs covering building and exploitation of the system, storage of experience, efficient end effective support to the decision-making process. Both these recognitions and the fact that each ton of the excavated coal is burdened by the costs of removal around 2.5 m3 water from the working environment, influenced the initiating the idea on introducing computer-supported monitoring-management system of a complex for dewatering of the "Drmno" open pit mine. .
Monitoring and diagnostics of power transformer insulation
Authors: Kovacevic Dragan , Skundric Slobodan , Lukic Jelena
Published: July 2007

Liberalization of the energy market drives utilities to a more cost-effective power system. Power transformers are the most complex, important, and critical components of the transition and distribution power systems. Insulation system is the key component of life extension, better availability and higher reliability of a transformer. In order to achieve both decreasing operational cost and reliable service condition-based maintenance is needed. Monitoring and diagnostics methods and techniques, for insulation condition assessment of power transformers, are described. Date base and knowledge rules diagnostics management system, in internet oriented environment, is outlined. .
Energy savings for residential heating in two pairs of buildings achieved by implementation of actually consumed energy measuring
Authors: Zivkovic Branislav , Todorovic Maja , Vasiljevic Petar
Published: July 2007

The paper presents results of heating energy consumption measurements in two pairs of buildings in community New Belgrade for two heating seasons. Influence of these measurements on energy savings is also presented. The measurements were carried out during heating seasons 2002/03 and 2003/04 in buildings in Block 34 and 63, connected to the district heating system "Beogradske elektrane". The buildings in each pair have similar architectural and thermal characteristics. One of the buildings in a pair was "test" building and the other "control" one. In the "test" building the energy consumption for heating of each apartment was measured, as well as total energy consumption for the whole building in the substation. Occupants were able to regulate the heating system. In the "control" building the energy consumption was measured only for the whole building, and occupants had almost no impact on heating energy consumption. The comparison of energy consumption for heating in the "test" and "control" buildings is given in the paper, as well as analysis of the influence of energy consumption measurements on the achieved energy savings. .
Reduction of carbon monoxide emission from a solid-fuel thermo-accumulation furnace
Authors: Dakic Dragoljub , Belosevic Srdjan , Mladenovic Rastko , Paprika Milijana , Djurovic Dejan , Eric Aleksandar , Komatina Mirko , Grbic Bosko , Radic Nenad
Published: July 2007

Many households in Serbia, using electric thermo-accumulation furnaces for heating, have been forced to find an alternative solution, due to a significant increase in electricity prices during the last decade. A possible solution is replacing electric heating appliances with the solid fuel-fired ones. A prototype of a new concept of thermo-accumulation solid fuel-fired furnace has been developed to meet these growing needs, providing electricity saving together with considerable environmental benefits. Two strategies for reduction of carbon monoxide emission are examined in the paper: application of Pt/Al2O3 catalyst, in the form of 3 ? 0.3 mm spheres, providing further combustion of flue gases within the furnace, as well as an additional emission reduction by means of the air excess control. Experimental investigations of the catalyst influence on the conversion of carbon monoxide have been done for different operation regimes and positions of the catalyst. The paper presents selected results regarding carbon monoxide emission during wood and coal combustion. Investigations suggest a considerable effect of the catalyst and a strong influence of the catalyst position within the furnace to carbon monoxide emission reduction. In addition, experimental tests have been conducted to asses the effect of the air excess control in the furnace on carbon monoxide emission. The amount of combustion air, the flue gas flow rate, and the fuel feeding regime have been adjusted in order to keep the flue gas oxygen content in a relatively narrow range, thus obtaining controlled combustion conditions and lower carbon monoxide emission. In this way, the furnace has been made able to respond to the changes in heating needs, fuel quality and other parameters, which is advantageous in comparison with similar solid-fuel fired furnaces. .
Investigations of combustion process in combined cooker-boiler fired on solid fuels
Authors: Stojiljkovic Dragoslava , Jovanovic Vladimir , Radovanovic Milan , Manic Nebojsa , Radulovic Ivo
Published: July 2007

The aim of the investigation was to make some reconstructions on the existing stove used for cooking and baking and to obtain the combined cooker-boiler which will fulfill the demands of European standard EN 12815. Implementation of modern scientific achievements in the field of combustion on stoves and furnaces fired on solid fuels was used. During the investigations four various constructions were made with different fresh air inlet and secondary air supply with the intention to obtain more complete combustion with increased efficiency and reduced CO emission. Three different fuels were used: firewood, coal, and wood briquette. A numerous parameters were measured: fuel weight changes during the combustion process, temperature of inlet and outlet water, flue gas composition (O2, CO, SO2, CO2, NOx), flue gas temperature, ash quantity etc. The result of the investigations is the stove with the efficiency of more than 75% - boiler Class 1 (according EN 12815) and CO emission of about 1% v/v. The results obtained during the measurements were used as parameters for modeling of combustion process. .
Fluid boundaries shaping using the method of kinetic balance
Authors: Benisek Miroslav , Cantrak Svetislav , Nedeljkovic Milos , Cantrak Djordje , Ilic Dejan , Bozic Ivan
Published: July 2007

Fluid flow in curved channels with various cross-sections, as a common problem in theoretical and applied fluid mechanics, is a very complex and quite undiscovered phenomenon. Defining the optimum shape of the fluid flow boundaries, which would ensure minimum undesirable phenomena, like "dead water" zones, unsteady fluid flow, etc., is one of the crucial hydraulic engineering?s task. Method of kinetic balance is described and used for this purpose, what is illustrated with few examples. .
Pilot plant for exploitation of geothermal waters
Authors: Stojiljkovic Dragan , Stojiljkovic Stanisa , Mitic Nebojsa , Pejic Dragan , Djurovic-Petrovic Maja
Published: July 2007

In Sijarinska spa, there are some 15 mineral and thermomineral springs, that are already being used for therapeutic purposes. For the exploitation of heat energy boring B-4 is very interesting. It is a boring of a closed type, with the water temperature of about 78?C and a flow rate of about 33 l/s. Waters with the flow rate of about 6 l/s are currently used for heating of the Gejzer hotel, and waters of the flow rate of about 0,121 l/s for the pilot drying plant. The paper presents this pilot plant. .
Development of the heating system using geothermal energy
Authors: Milanovic Predrag , Tomic Vojislav , Jacimovic Branislav , Genic Srbislav , Djurovic-Petrovic Maja
Published: July 2007

The paper presents the results achieved by the project financed by Ministry of Science and Environmental Protection of Serbia during the period 2003-2005. The purpose of the project was determination methodology for designing heating system using geothermal water. Achieved results were implemented in the demonstration installment in factory "Palanacki kiseljak" in Smederevska Palanka, Serbia, using geothermal water from the well near by factory. .