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Selected AbstractsEnergy, exergy and exergoeconomic analysis of a steam power plant: A case studyINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2009Mohammad Ameri Abstract The objective of this paper is to perform the energy, exergy and exergoeconomic analysis for the Hamedan steam power plant. In the first part of the paper, the exergy destruction and exergy loss of each component of this power plant is estimated. Moreover, the effects of the load variations and ambient temperature are calculated in order to obtain a good insight into this analysis. The exergy efficiencies of the boiler, turbine, pump, heaters and the condenser are estimated at different ambient temperatures. The results show that energy losses have mainly occurred in the condenser where 306.9,MW is lost to the environment while only 67.63,MW has been lost from the boiler. Nevertheless, the irreversibility rate of the boiler is higher than the irreversibility rates of the other components. It is due to the fact that the combustion reaction and its high temperature are the most significant sources of exergy destruction in the boiler system, which can be reduced by preheating the combustion air and reducing the air,fuel ratio. When the ambient temperature is increased from 5 to 24°C, the irreversibility rate of the boiler, turbine, feed water heaters, pumps and the total irreversibility rate of the plant are increased. In addition, as the load varies from 125 to 250,MW (i.e. full load) the exergy efficiency of the boiler and turbine, condenser and heaters are increased due to the fact that the power plant is designed for the full load. In the second part of the paper, the exergoeconomic analysis is done for each component of the power plant in order to calculate the cost of exergy destruction. The results show that the boiler has the highest cost of exergy destruction. In addition, an optimization procedure is developed for that power plant. The results show that by considering the decision variables, the cost of exergy destruction and purchase can be decreased by almost 17.11%. Copyright © 2008 John Wiley & Sons, Ltd. [source] Performance and emission characteristics of turpentine,diesel dual fuel engine and knock suppression using water diluentsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2007R. Karthikeyan Abstract In the present work, a normal diesel engine was modified to work in a dual fuel (DF) mode with turpentine and diesel as primary and pilot fuels, respectively. The resulting homogeneous mixture was compressed to a temperature below the self-ignition point. The pilot fuel was injected through the standard injection system and initiated the combustion in the primary-fuel air mixture. The primary fuel (turpentine) has supplied most of the heat energy. Usually, in all DF engines, low-cetane fuels are preferred as a primary fuel. Therefore, at higher loads these fuels start knocking and deteriorating in performances. Usually, DF operators suppress the knock by adding more pilot-fuel quantity. But in the present work, a minimum pilot-fuel quantity was maintained constant throughout the test and a required quantity of diluent (water) was added into the combustion at the time of knocking. The advantages of this method of knock suppression are restoration of performance at full load, maintenance of the same pilot quantity through the load range and reduction in the fuel consumption at full load. From the results, it was found that all performance and emission parameters of turpentine, except volumetric efficiency, are better than those of diesel fuel. The emissions like CO, UBHC are higher than those of the diesel baseline (DBL) and around 40,45% reduction of smoke was observed at 100% of full load. The major pollutant of diesel engine, NOx, was found to be equal to that of DBL. From the above experiment, it was proved that approximately 80% replacement of diesel with turpentine is quite possible. Copyright © 2006 John Wiley & Sons, Ltd. [source] Exergy analysis of a coal-based 210 MW thermal power plantINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2007S. Sengupta Abstract In the present work, exergy analysis of a coal-based thermal power plant is done using the design data from a 210 MW thermal power plant under operation in India. The entire plant cycle is split up into three zones for the analysis: (1) only the turbo-generator with its inlets and outlets, (2) turbo-generator, condenser, feed pumps and the regenerative heaters, (3) the entire cycle with boiler, turbo-generator, condenser, feed pumps, regenerative heaters and the plant auxiliaries. It helps to find out the contributions of different parts of the plant towards exergy destruction. The exergy efficiency is calculated using the operating data from the plant at different conditions, viz. at different loads, different condenser pressures, with and without regenerative heaters and with different settings of the turbine governing. The load variation is studied with the data at 100, 75, 60 and 40% of full load. Effects of two different condenser pressures, i.e. 76 and 89 mmHg (abs.), are studied. Effect of regeneration on exergy efficiency is studied by successively removing the high pressure regenerative heaters out of operation. The turbine governing system has been kept at constant pressure and sliding pressure modes to study their effects. It is observed that the major source of irreversibility in the power cycle is the boiler, which contributes to an exergy destruction of the order of 60%. Part load operation increases the irreversibilities in the cycle and the effect is more pronounced with the reduction of the load. Increase in the condenser back pressure decreases the exergy efficiency. Successive withdrawal of the high pressure heaters show a gradual increment in the exergy efficiency for the control volume excluding the boiler, while a decrease in exergy efficiency when the whole plant including the boiler is considered. Keeping the main steam pressure before the turbine control valves in sliding mode improves the exergy efficiencies in case of part load operation. Copyright © 2006 John Wiley & Sons, Ltd. [source] Partitioning behavior of mercury during coal combustion: the influence of low-NOx burners and operation load of boilerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009Guang-Qian Luo Abstract Two 200 MW, pulverized bituminous coal-fired electric utility boilers each equipped with a five-field cold-side electrostatic precipitator (ESP) as the only air pollution control device (APCD) were investigated on mercury distribution and speciation under various conditions. With the same fuel consumption, both facilities are the same but with different burners, low-NOx type and conventional type. Sampling points of gaseous mercury and chlorine species were at the inlet and outlet of the ESP. The mercury concentrations in various solids, including parent coal, bottom slag, economizer bottom ash and fly ash in different hoppers of ESP, were sampled and analyzed. The Ontario Hydro Method was employed to detect mercury in flue gas, and HCl and Cl2 were detected by the EPA method 26. A series of tests were conducted on the boiler with low-NOx burners under various loads (70, 85 and 100% of full load) and on the other boiler with conventional burners under full load. Results showed that small amount of mercury remained in the solid combustion products and most of mercury was released into the atmosphere. The majority of the released mercury was in oxidized form. Burner types and load variation had effects on Cl species concentration in flue gas. Furthermore, particle diameter and carbon content and specific surface area of fly ash affected speciation and distribution of mercury and mercury removal efficiency of ESP. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Membrane reformer PEM cogeneration systems for residential applications,Part A: full load and partial load simulationASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009Stefano Campanari Abstract This two-part paper investigates the performances and economic potential benefits of a fuel cell cogeneration system based on a membrane reformer (MREF), using polymer electrolyte membrane (PEM) fuel cells, applied to residential cogeneration. Part A of this work focuses on the thermodynamic analysis and simulation of the system at full and partial load conditions, discussing its performance by means of a sensitivity analysis carried out under different operating conditions. Part B presents the technoeconomic analysis of the proposed system integrated into a real residential application, dealing with the energy savings and the economic balances, and proposes a preliminary design of the cogeneration unit. The system is based upon a PEM fuel cell, integrated with a membrane reformer (MREF) to form a small-scale, highly efficient cogeneration unit, potentially suitable for application to distributed generation in the residential field. The high purity hydrogen fuel required by the PEM fuel cell is produced in the membrane reformer through hydrogen selective membranes based on a Pd-Ag alloy. The analysis is carried out aiming to define the system energy balances in all the conditions occurring under real operation, including the influence of ambient temperature and of the expected fuel cell efficiency decay with time. The discussion reveals the relevant potential advantages of the MREF solution with respect to fuel cell units based on steam reforming (SR) or auto-thermal reforming (ATR): when compared to these solutions, MREF exhibits a 10% points higher electrical efficiency and requires a much simpler plant layout. These results are the basis for the detailed system technoeconomic analysis carried out in Part B of the work. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] A capture-assisted random access scheme for multi-beam LEO satellite packet data networksINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2004George Thomas Abstract A CDMA-based satellite switch is proposed for use in multi-beam satellites carrying random-access packet-switched data. Applications include the emerging new low-earth-orbit (LEO) satellite networks which support global wireless networking. Capture phenomenon is used to advantage in increasing the random access throughput, and the on-board switch is at once simple and specially designed to handle full loads with minimal complexity. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||