Showing papers in "Thermal Science in 2006"

Comparison of Oxygen Carriers for Chemical-Looping Combustion

Abstract: 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.

Performance characteristics of the solar parabolic trough collector with hot water generation system

Abstract: The performance of a new parabolic trough collector hot water generation system with a well mixed hot water storage tank is investigated in the present work. The storage tank water temperature is increased from 35 °C at 9.30 h to 73.84 °C at 16.00 h when no energy is withdrawn from the storage tank. The average beam radiation during the collection period is 699 W/m2. The useful heat gain, the collector instantaneous efficiency, the energy gained by the storage tank water and the efficiency of the system as a whole are found to follow the variation of incident beam radiation as these parameters are strongly influenced by the incident beam radiation. The value of each of those parameters is observed to be maximum around noon, when the incident beam radiation is maximum.

Applications of oxygen for NOx control and CO2 capture in coal-fired power plants

Abstract: 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. .

Thermodynamic analysis of air refrigerator on exergy graph

Abstract: Improving mechanical system efficiency is the goal of many engineers and scientists. Commonly, the solutions to these types of problems are uncovered using thermodynamic analysis and optimization. An innovative method for the thermodynamic analysis of a complex energy-intensive system with an arbitrary structure is described in this paper. The method is based on a novel general equation to calculate the total system exergy efficiency using an exergy flow graph proposed by the authors. Discuss in this paper exergy efficiency and exergy loss models as well this approach allows a user to obtain not only the exergy losses and efficiency of the total system, but also to show the relationship between the exergy efficiency of an individual element and that of the entire system. An example is provided that employs this method to the thermodynamic analysis of an air refrigerator.

Optimization of pulverised coal combustion by means of CFD/CTA modeling

Abstract: The objective of the work presented in this paper was to apply a method for handling two-phase reacting flow for prediction of pulverized coal combustion in large-scale boiler furnace and to assess the ability of the model to predict existing power plant data. The paper presents the principal steps and results of the numerical modeling of power boiler furnace with tangential disposition of the burners. The computational fluid dynamics/computational thermal analysis (CFD/CTA) approach is utilized for creation of a three-dimensional model of the boiler furnace, including the platen superheater in the upper part of the furnace. Standard k-e model is employed for description of the turbulent flow. Coal combustion is modeled by the mixture fraction/probability density function approach for the reaction chemistry, with equilibrium assumption applied for description of the system chemistry. Radiation heat transfer is computed by means of the simplified P-N model, based on the expansion of the radiation intensity into an orthogonal series of spherical harmonics. Some distinctive results regarding the examined boiler performance in capacity range between 65 and 95% are presented graphically. Comparing the simulation predictions and available site measurements concerning temperature, heat flux and combustion efficiency, a conclusion can be drawn that the model produces realistic insight into the furnace processes. Qualitative agreement indicates reasonability of the calculations and validates the employed sub-models. After the validation and verification of the model it was used to check the combustion efficiency as a function of coal dust sieve characteristics, as well as the impact of burners modification with introduction of over fire air ports to the appearance of incomplete combustion, including CO concentration, as well as to the NOx concentration. The described case and other experiences with CFD/CTA stress the advantages of numerical modeling and simulation over a purely field data study, such as the ability to quickly analyze a variety of design options without modifying the object and the availability of significantly more data to interpret the results. .

Experimental investigation of turbulent structures of flow around a sphere

Abstract: This paper presents the experimental investigation of turbulent structures of flow around a sphere. The mean velocity field and the turbulence quantities are obtained in a small low speed wind tunnel using, laser-Doppler anemometry, for the flow around a sphere at subcritical Reynolds number of 50,000. The results of laser-Doppler measurements are compared with results obtained by large eddy simulation. In this paper also flow visualization around sphere in the bigger wind tunnel and water channel for Reynolds numbers between 22,000 and 400,000 have been done.

Entropy-cycle method for analysis of refrigeration machine and heat pump cycles

Abstract: 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.

Energy Efficiency in Serbia: Research and Development Activities

Abstract: Energy system in Serbia, from exploitation of primary energy sources transformations in electric power plants and district heating plants, energy (electric and heat) transmission and distribution to final users, is faced with a number of irrational and in efficient behaviors and processes. Those are consequences of the old technologies in use, old equipment at the end of their life time, bad exploitation of the equipment in use, wrong energy strategy in the past, un suitable energy price policy, as well as delayed refurbishment of the equipment and delayed implementation of the modern technologies. Structure of the industry, developed after the World War II also contributed to a high specific use of energy per unit of production. Paper gives a short review of the present status of energy system in Serbia with special emphasis on the energy efficiency, renewable energy sources use and import energy dependence. Main part of the paper is devoted to the activity of the National Energy Efficiency Program (NEEP), founded by Ministry of Science and Environmental Protection. A program started in 2002 and in the period up to 2005, 140 RD energy and fuel prices do not stimulate rational and efficient use of energy; favor able environment for rational and efficient behavior of the people and companies was not created by governmental policy.

Advanced thermodynamics metrics for sustainability assessments of open engineering systems

Abstract: This paper offers a verification of the following hypotheses. Advanced thermodynamics metrics based on entropy generation assessments indicate the level of sustainability of transient open systems, such as in manufacturing or process industries. The indicator of sustainability may be related to particular property uniformity during materials processing. In such a case the property uniformity would indicate systems’ distance from equilibrium i.e., from the sustainable energy utilization level. This idea is applied to a selected state-of-the-art manufacturing process. The system under consideration involves thermal processing of complex aluminum structures during controlled atmosphere brazing for a near-net-shape mass production of compact heat exchangers.

Energy efficiency in Serbia national energy efficiency program: Strategy and priorities for the future

Abstract: Energy system in Serbia, in the whole energy chain, from exploitation of primary energy sources, transformations in electric power plants and district heating plants, energy (electric and heat) transmission and distribution to final users, and up to final energy consumption, is faced with a number of irrational and inefficient behavior and processes. In order to fight with such situation National Energy Efficiency Program, financed by the Ministry of Science and Environmental Protection has been founded in 2001. Basic facts about status of energy sector in Serbia, with special emphasis on the energy efficiency and use of renewable energy sources have been given in the review paper published in the issue No. 2, 2006 of this journal. In present paper new strategy and priorities of the National Energy Efficiency Program for the future period from 2006 to 2008, and beyond, is presented. This strategy and priorities are mainly based on the same concept and principles as previous, but new reality and new and more simulative economic and financial environment in energy sector made by the Energy low (accepted by Parliament in 2004) and Strategy of Development of Energy Sector in Republic Serbia up to 2015 (accepted by the Parliament in May 2005), have been taken into account. Also, responsibilities that are formulated in the Energy Community Treaty signed by the South-East European countries, and also coming from documents and directives of the European Community and Kyoto Protocol are included in new strategy. Once again necessity of legislative framework and influence of regulations and standards, as well as of the governmental support, has been pointed out if increased energy efficiency and increased use of renewable energy sources are expected. .

Numerical experiments on wall turbulence at low Reynolds number

Abstract: A direct numerical simulation of a turbulent channel flow, with regularly spaced two-dimensional roughness elements mounted at the wall and perpendicular to the flow direction, was performed at a very low Reynolds number of Re
940 based on the centerline velocity and the full channel height. Using the lattice Boltzmann numerical algorithm, all essential scales were resolved with about 19·106 grid points (1155 x 129 x 128 in the x1, x2 and x3 directions). The computed results confirm the existence of turbulence at such a low Reynolds number. Turbulence persisted over the entire computation time, which was sufficiently long to prove its self-maintenance. By examination of statistical features of the flow across the anisotropy-in variant map, it was found that these coincide with conclusions emerging from the analysis of transition and breakdown to turbulence in a laminar boundary layer exposed to small, statistically stationary, neutrally stable axisymmetric disturbances with the stream wise intensity component ( u'1) lower than the intensities in the normal ( u'1) and span wise directions u'1< u'2 = u'3. To further support the concept and the results of
theoretical considerations of the laminar to turbulent transition process in wall-bounded flows using statistical techniques and to demonstrate its great potential for engineering, an additional simulation was performed of a plane channel flow with regularly spaced riblet elements mounted at the wall and aligned parallel with the flow direction. The supplementary simulation was done at a Reynolds number of Re = 6584 using about 250·106 grid points (4096 x 257 x 240). Analysis of the simulation results carried out across the flow region located in the mid plane between the riblet elements confirms the central result which lies in the root of the statistical dynamics of the velocity fluctuations in wall-bounded flows: when the velocity fluctuations close to the wall tend towards the one-component state, so that the stream wise intensity component is much larger than the intensities in the normal and span wise directions, u'1< u'2 = u'3, the turbulent dissipation rate vanishes at the wall, leading to a significant reduction of the wall shear stress. For the simulated flow case the local value of wall shear stress reduction was found to exceed the wall shear stress reduction SR
92% which corresponds to a fully developed laminar channel flow with smooth walls at the same Reynolds number.

Production and characterization of bio-oil from catalytic biomass pyrolysis

Abstract: Biomass flash pyrolysis is a very promising thermochemical process for the production of bio-fuels and/or chemicals. However, large-scale applications are still under careful consideration, because of the high bio-liquid upgrading cost. In this paper the production of bio-liquids from biomass flash pyrolysis in a single stage catalytic process is being investigated using a novel once through fluid bed reactor. This biomass pyrolysis unit was constructed in Chemical Process Engineering Research Institute and comprises of a catalyst regenerator, a biomass-vibrating hopper, a fluidization reactor (that consists of an injector and a riser reactor), a product stripper along with a hot cyclone and a filter housing and finally a product condensation/recovery section. The unit can process up to 20 g/min. of biomass (50-800 mm) and can circulate up to 300 g/min. of catalyst or inert material. The experiments performed in the pilot plant showed that the unit operates without problems and with satisfactory mass balances in a wide range of experimental conditions both in the absence and presence of catalyst. With the incorporation of an FCC catalyst in the pyrolysis, the physical properties of the bio-oil produced changed, while more stable bio-oil was produced. .

Scaling of permeabilities and friction factors of homogeneously expanding gas-solids fluidized beds: Geldart’s A powders and magnetically stabilized beds

Abstract: The concept of a variable friction factor of fluid-driven de form able powder beds undergoing fluidization is discussed. The special problem discussed addresses the friction factor and bed permeability relationships of Geldart’s A powders and magnetically stabilized beds in axial fields. Governing equations and scaling relation ships are developed through three approaches (1) Minimization of the pressure drop with respect to the fluid velocity employing the Darcy-Forchheimer equation together with the Richardson-Zaki scaling law, (2) Minimization of the pres sure drop across an equivalent-channel replacing the actual packed beds by a straight pipe with bed-equivalent obstacle of a simple geometry, and (3) Entropy minimization method applied in cases of the Darcy-Forchheimer equation and the equivalent-channel model. Bed-to-surface heat transfer coefficients are commented in the context of the porosity/length scale relationships developed. Both the pressure drop curves developments and phase diagram de signs are illustrated by applications of the intersection of asymptotes technique to beds exhibiting certain degree of cohesion.

Performance evaluation of tube-in-tube heat exchangers with heat transfer enhancement in the annulus

Abstract: 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.

Persistence of the laminar regime in a flat plate boundary layer at very high Reynolds number

Abstract: Starting from the Navier-Stokes and the continuity equations of a viscous incompressible fluid, a statistical theory is developed for the prediction of transition and breakdown to turbulence in a laminar boundary layer exposed to small, statistically stationary axisymmetric disturbances. The transport equations for the statistical properties of the disturbances are closed using the two-point correlation technique and invariant theory. By considering the local equilibrium to exist between production and viscous dissipation, which forces the energy of the disturbances in the boundary layer to be lower than that of the free stream, the transition criterion is formulated in terms of the anisotropy of the disturbances and a Reynolds number based on the intensity and the length scale of the disturbances. The transition criterion determines conditions that guarantee maintenance of the laminar flow regime in a flat plate boundary layer. It is shown that predictions of the transition onset deduced from the transition criterion yield the critical Reynolds number, which is in good agreement with the experimental data obtained under well-controlled laboratory conditions reported in the literature. For the preferred mode of the axisymmetric disturbances, for which the intensity of the disturbances in the stream wise direction is larger than in the other two directions, the analysis shows that the anisotropy increases the critical Reynolds number. Theoretical considerations yield the quantitative estimate for the minimum level of the anisotropy of the free stream required to prevent transition and breakdown to turbulence. The numerical databases for fully developed turbulent wall-bounded flows at low and moderate Reynolds numbers were utilized to demonstrate the stabilizing and destabilizing role of the anisotropy in the disturbances on the development of the transition process in wall-bounded flows. The stabilizing role of increased anisotropy in a free stream on the boundary layer development was successfully tested experimentally in a large wind tunnel by maintaining the stable laminar regime in a flat plate boundary layer up to (Rex)T

4·106.

Constructal theory and flow architectures in living systems

Abstract: 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 γ 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.

Monitoring and diagnostics of power transformer insulation

Abstract: 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. .

Lignite chemical conversion in an indirect heat rotary kiln gasifier

Abstract: The results on the gasification of Greek lignite using two indirect heat (allothermal) pilot rotary kiln gasifiers are reported in the present work. The development of this new reactor-gasifier concept intended for solid fuels chemical conversion exploits data and experience gained from the following two pilot plants. The first unit A (about 100 kg/h raw lignite) demonstrated the production of a medium heating value gas (12-13 MJ/Nm3) with quite high DAF (dry ash free) coal conversions, in an indirect heat rotary gasifier under mild temperature and pressure conditions. The second unit B is a small pilot size unit (about 10 kg/h raw lignite) comprises an electrically heated rotary kiln, is an operation flexible and exhibits effective phase mixing and enhanced heat transfer characteristics. Greek lignite pyrolysis and gasification data were produced from experiments performed with pilot plant B and the results are compared with those of a theoretical model. The model assumes a scheme of three consecutive-partly parallel processes (i. e. drying, pyrolysis, and gasification) and predicts DAF lignite conversion and gas composition in relatively good agreement with the pertinent experimental data typical of the rotary kiln gasifier performance. Pilot plant B is currently being employed in lime-enhanced gasification studies aiming at the production of hydrogen enriched synthesis gas. Presented herein are two typical gas compositions obtain from lignite gasification runs in the presence or not of lime. .

Development and investigation of solar collectors for conversion of solar radiation into heat and/or electricity

Abstract: This article describes work on two projects of the National Energy Efficiency Program NEEP 709300036 and NPEE 271003 titled "The model of solar collector for middle temperature conversion of solar radiation in heat" and "Development and investigation on hybrid solar collector for heat and electricity generation", respectively. This first project deals with solar collector that transfers solar radiation in heat in area of middle temperature conversion (at temperatures above 100 oC). During entire year it can realize significant saving of electric energy used for preparation of warm water and in central and district heating. During work on the second project, two hybrid solar collectors, their installation, mathematical model, software, and experimental set-up were designed and realized. The first collector had the photovoltaic panel located above the absorber and the second collector had the panel located on the absorber. For both collectors, the results show that efficiency of fossil fuel replacement is 85%. .

Efficiency and emission of crop residues combustion facilities in Serbia: Status and needed measures for improvement

Abstract: Use of crop residues as fuel has a long tradition in rural areas of Serbia. Numerous biomass-fueled facilities were built during the 80s. Among those were small facilities for household heating, with thermal power from 5 to 50 kW, medium-size facilities for farm and greenhouses, with thermal power 50 to 1000 kW, and large facilities for processing of agricultural products, with thermal powers higher than 1000 kW. The results showed that the level of biomass combustion facilities is in general very low. This is especially the case for heating facilities used for house-hold heating. The measures for improvement were proposed. .

Development of the heating system using geothermal energy

Abstract: 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. .

Pilot plant for exploitation of geothermal waters

Abstract: 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. .

Constructal theory of design in engineering and nature

Abstract: 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.

Novel concepts for near-zero emissions IGCC power plants

Abstract: 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. .

The energy policy of Greece

Abstract: 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. .

Dispersion modeling for regulatory applications

Abstract: Air quality simulation models are extensively used in assessing the impacts of combustion plants. A wide variety of models are available. In order to recommend the most appropriate air quality modeling technique that should be incorporated into a standard regulatory framework in the Republic of Macedonia the performances of three Gaussian-plume atmospheric dispersion models, ADMS 3, OML, and ISCST3 have been analyzed. The models have been tested against the ground level measurements of the daily mean SO2 concentrations obtained at the four locations around the Thermal Power Plant of Bitola. Two experimental campaigns have been performed. The three model results and the measurements at the presented locations for 365 days in the year are compared. An analysis of the obtained results is presented in the paper as well. The meteorological preprocessor MADAM_MP has been used to provide the required boundary layer parameters for estimation of the transport and diffusion of pollutants released from the stacks. Using the MADAM_MP a year of hourly values for the mixing height, Monin-Obukhov length surface friction velocity, sensible heat flux, and Pasquill's stability class, have been calculated from the available meteorological data set. The approach and the main equations for the boundary layer parameters estimation are presented in this paper.

Energy savings for residential heating in two pairs of buildings achieved by implementation of actually consumed energy measuring

Abstract: 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. .

Prospects for co-firing of clean coal and creosote-treated waste wood at small-scale power stations

Abstract: If a small-scale clean coal fueled power plant is co-fueled with 5% of creosote-treated used-up sleeper wood, the decontamination by carbonisation at 500 °C in an indirectly heated rotary kiln with the diameter 1.7 m and effective length 10 m can be realized. It should be included in the "3R Clean Coal Carbonisation Plant" system, which processes coal. It will improve the heat balance of the system, since the carbonisation of wood will deliver a lot of high caloricity pyroligneous vapour to the joint furnace of the "3R Clean Coal Carbonisation Plant". Pine wood sleeper sapwood contains 0.25% of sulphur, but the average pine sleeper wood (sapwood and heartwood) 0.05% of sulphur. Most of the sulphur is lost with the pyroligneous vapour and burned in the furnace. Since the "3R Clean Coal Carbonisation Plant" is equipped with a flue gases cleaning system, the SO2 emission level will not exceed 5 mg/m3. The charcoal of the sapwood portion of sleepers and that of the average sleeper wood will contain 0.22% and 0.035% of sulphur, respectively. The increase of the carbonisation temperature does not substantially decrease the sulphur content in charcoal, although it is sufficiently low, and the charcoal can be co-fired with clean coal. The considered process is suitable for small power plants, if the biomass input in the common energy balance is 5 to 10%. If the mean distance of sleepers transportation for Central and Eastern Europe is estimated not to exceed 200 km, the co-combustion of clean coal and carbonized sleepers would be an acceptable option from the environmental and economic points of view.

CO2 capture and storage in Greece: A case study from komotini ngcc power plant

Abstract: The aim of this paper is to examine the possibilities for the abatement of CO2 emissions in the Greek fossil fuel power generation sector. An overview of CO2 capture, transportation, and storage concepts, on which the R&D community is focused, is presented. The implementation of post-combustion CO2 capture options in an existing fossil fuel power plant is then examined and the consequences on the overall plant performance are determined. Finally, the possibilities of transportation and then underground storage of the pure CO2 stream are analyzed taking into account both technical and economical factors. The results of this analysis show that CO2 sequestration is technically feasible for existing fossil fuel fired power plants in Greece. However, substantial reduction in plant efficiency is observed due to increased energy demand of the technologies used as well as in electricity production cost due to capital and operation costs of capture, transport, and storage of CO2. .