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Boiler
Kinds of Boiler Selected AbstractsPilot scale SO2 control by dry sodium bicarbonate injection and an electrostatic precipitatorENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2007Michael J. Pilat Abstract A 500 actual cubic feet gas per minute (acfm) pilot-scale SO2 control study was undertaken to investigate flue gas desulfurization (FGD) by dry sodium sorbents in 400°F (204.5°C) flue gases emitted from a coal fired boiler with flue gas concentrations between 350 and 2500 ppm SO2. Powdered sodium alkaline reagents were injected into the hot flue gas downstream of the air preheater and the spent reagents were collected using an electrostatic precipitator. Three different sorbents were used: processed sodium bicarbonate of two particle sizes; solution mined sodium bicarbonate, and processed sodium sesquicarbonate. SO2 concentrations were measured upstream of the reagent injection, 25-ft (7.62 m) downstream of the injection point, and downstream of the electrostatic precipitator. SO2 collection efficiencies ranged from 40 to 80% using sodium bicarbonate stoichiometric ratios from 0.5 to 3.0. Much of the in-duct SO2 removal occurred during the first second of reagent reaction time, indicating that the sulfur dioxide,sodium reaction rates may be faster than have been measured for fixed bed measurements reported in the literature. © 2007 American Institute of Chemical Engineers Environ Prog, 2007 [source] Eliminating a sulfuric acid mist plume from a wet caustic scrubber on a petroleum coke calcinerENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2001Charles A. Brown Reducing sulfuric acid mist emissions and eliminating the visible plume that remained after steam dissipation were the objectives of a project recently completed for a petroleum coke calciner. The coke calciner produces flue gas containing SO2 that is treated with a wet caustic scrubber. The scrubber is extremely efficient at removing most of the SO2, but some oxidizes to SO3, catalyzed by vanadium in the coke dust that collects in the waste heat boiler. Submicron droplets of H2SO4 form when the flue gas is quenched by the scrubber liquor, and makes its way through the scrubber. This paper describes the installation of, and performance test results for, a wet electrostatic precipitator (WESP), as well as SO2 scrubber modifications that were re q u i red to make room for the WESP. The successful project significantly reduced sulfuric acid mist emissions, eliminating the visible plume while maintaining a very low SO2 outlet concentration, even after removing one of three gas-liquid contactors. [source] Method of calculation of heat transfer coefficient of the heater in a circulating fluidized bed furnaceHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2002J.F. Lu Abstract Knowledge of heat transfer coefficients is important in the design and operation of CFB boilers. It is the key to determining the area and the layout of the heat transfer surfaces in a CFB furnace. Local bulk density has a close relationship to the local heat transfer coefficient. Using a heat flux probe and bulk density sampling probe, the local bed to wall heat transfer coefficient in the furnace of a 75 t/h CFB boiler was measured. According to the experimental results and theoretical analysis of the facts that influence the heat transfer, the heat transfer coefficient calculation method for the CFB furnace was developed. The heat transfer surface configuration, heating condition, and the material density are considered in this method. The calculation method has been used in the design of CFB boilers with a capacity from 130 t/h to 420 t/h. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(7): 540,550, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10056 [source] An experimental study on vapor condensation of wet flue gas in a plastic heat exchangerHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2001L. Jia Abstract An experimental system investigating condensation heat transfer of wet flue gas was set up, and the heat transfer performance of vapor-gas mixture with vapor condensation was discussed. The experimental results of laminar flow in a plastic longitudinal spiral plate heat exchanger were obtained and are in good agreement with the modified classical film model. It is shown that the plastic air preheater can avoid acid corrosion in the low-temperature field for the boiler using fuel containing sulfur and recover latent heat of the water vapor of the wet flue gas. Also some SO2 was scrubbed during the vapor condensing process in the heat exchanger. © 2001 Scripta Technica, Heat Trans Asian Res, 30(7): 571,580, 2001 [source] Energy, 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] Dynamic operation plan of a combined fuel cell cogeneration, solar module, and geo-thermal heat pump system using Genetic AlgorithmINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2007Shin'ya Obara Abstract A chromosome model that simulates the operation patterns of an energy system was introduced into a simple Genetic Algorithm, and a method of dynamic optimization was developed. This paper analyses the operation planning of an energy system that uses in combination a solar power module, proton-exchange membrane fuel cell cogeneration (PEMFC-CGS) with methanol steam reforming, a geo-thermal heat pump, heat storage and battery, commercial power, and a kerosene boiler. The hours of operation of each energy device and the rate of the energy output were calculated by having introduced the analysis program developed by this study. Three objective functions: (a) minimization of operation cost; (b) minimization of the error of demand-and-supply balance; and (c) minimization of the amount of greenhouse gas discharge were given to the optimization analysis of the system. Furthermore, the characteristics of the system operation planning under each objective function are described. Copyright © 2007 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] Long time investigation of the effect of fouling on the super-heaters in a circulating fluidized biomass boilerINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2006Jan Sandberg Abstract The present investigation involves measurements and theories on the mechanisms of the forming of deposit layers on super-heater tubes in a biomass-fired CFD boiler. The deposit layer thickness and the soot-blowing frequency effect on the super-heaters heat transfer are the main subject of the study that has been conducted over a 3-year period. The measurements show a deposit growth rate on the super-heaters of approximately 4 g m,2 h,1. The distribution of the deposit material varies significantly between the windward and the leeward side of the tubes, with the thickest layers on the windward side. Further down stream of the first super-heater, the fouling problem on the super-heater and re-heater tubes are not so severe. A theoretical model shows that a deposit layer of 20 mm will decrease the heat transfer rate of the first super-heater by nearly 40%. The soot-blowing system shows a strong positive effect on the heat transfer rate of the super-heater a few hours after a soot-blowing sequence has been completed. However in the long run, the varied soot-blowing frequency does not have a significant influence on the deposit layer growth rate. Copyright © 2006 John Wiley & Sons, Ltd. [source] Modelling and experimental studies on heat transfer in the convection section of a biomass boilerINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2006Jukka Yrjölä Abstract This paper describes a model of heat transfer for the convection section of a biomass boiler. The predictions obtained with the model are compared to the measurement results from two boilers, a 50 kWth pellet boiler and a 4000 kWth wood chips boiler. An adequate accuracy was achieved on the wood chips boiler. As for the pellet boiler, the calculated and measured heat transfer rates differed more than expected on the basis of the inaccuracies in correlation reported in the literature. The most uncertain aspect of the model was assumed to be the correlation equation of the entrance region. Hence, the model was adjusted to improve the correlation. As a result of this, a high degree of accuracy was also obtained with the pellet boiler. The next step was to analyse the effect of design and the operating parameters on the pellet boiler. Firstly, the portion of radiation was established at 3,13 per cent, and the portion of entrance region at 39,52 per cent of the entire heat transfer rate under typical operating conditions. The effect of natural convection was small. Secondly, the heat transfer rate seemed to increase when dividing the convection section into more passes, even when the heat transfer surface area remained constant. This is because the effect of the entrance region is recurrent. Thirdly, when using smaller tube diameters the heat transfer area is more energy-efficient, even when the bulk velocity of the flow remains constant. Copyright © 2006 John Wiley & Sons, Ltd. [source] Probabilistic aspects in the technical and economic analysis of the industrial waste heat recovery system generating useful heat and refrigerationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2005J. Kozio Abstract The technical and economic analysis of the industrial waste heat recovery system, considering probabilistic distribution of the input data is presented. A prospect and rationality of the application of the waste heat boiler and absorption refrigerator has been examined as an example, in view of covering integrated heat and refrigeration demands. The influence of changing ambient conditions as well as the exhaust gas temperature and its flow rate on the overall system performance has been simulated and assessed. Copyright © 2005 John Wiley & Sons, Ltd. [source] Multi-objective optimization of the coal combustion performance with artificial neural networks and genetic algorithmsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2005Hao Zhou Abstract The present work introduces an approach to predict the nitrogen oxides (NOx) emissions and carbon burnout characteristics of a large capacity pulverized coal-fired boiler with an artificial neural network (ANN). The NOx emissions and carbon burnout characteristics are investigated by parametric field experiments. The effects of over-fire-air (OFA) flow rates, coal properties, boiler load, air distribution scheme and nozzle tilt are studied. An ANN is used to model the NOx emissions characteristics and the carbon burnout characteristics. A genetic algorithm (GA) is employed to perform a multi-objective search to determine the optimum solution of the ANN model, finding the optimal setpoints, which can suggest operators' correct actions to decrease NOx emissions and the carbon content in the flyash simultaneously, namely, get a good boiler combustion performance with high boiler efficiency while keeping the NOx emission concentration meet the requirement. Copyright © 2005 John Wiley & Sons, Ltd. [source] Experimental study of the combustion efficiency and formation of NOx in an industrial pulverized coal combustorINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2004Li ZhengQi Abstract With horizontal bias combustion burners, experiments have been carried out on a 670 t h,1, corner-fired, pulverized-coal fired boiler burning bituminous coal. At 200 MWe load, the furnace excess O2 remains stable. The different horizontal fuel biases are obtained by changing the tilt angle of all the Louvre enrichers' regulating blades. The tilt angles of the blades are 0, 15, 24, 32°; the result is that the enriching ratios of the fuel-rich primary air increase from 2.2 to 2.6 at No. 2 corner, and from 1.2 to 4.2 at No. 3 corner. The gas temperature increases in the burner region. The application of the horizontal bias combustion burners results in a reduction in NOx formation from 545.7 mg Nm,3 (O2=6%) to 287.9 mg Nm,3, and a substantial reduction in carbon in ash content from 5.24 to 2.48%. The boiler operated stably at a load of 80 MWe without auxiliary fuel oil. Copyright © 2004 John Wiley & Sons, Ltd. [source] Measurements and numerical simulations for optimization of the combustion process in a utility boilerINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2004A. Vikhansky Abstract A three-dimensional computational fluid dynamics code was used to analyse the performance of 550MW pulverized coal combustion opposite a wall-fired boiler (of IEC) at different operation modes. The main objective of this study was to prove that connecting plant measurements with three-dimensional furnace modelling is a cost-effective method for design, optimization and problem solving in power plant operation. Heat flux results from calculations were compared with measurements in the boiler and showed good agreement. Consequently, the code was used to study hydrodynamic aspects of air,flue gases mixing in the upper part of the boiler. It was demonstrated that effective mixing between flue gases and overfire air is of essential importance for CO reburning. From our complementary experimental-numerical effort, IEC considers a possibility to improve the boiler performance by replacing the existing OFA nozzles by those with higher penetration depth of the air jets, with the aim to ensure proper mixing to achieve better CO reburning. Copyright © 2004 John Wiley & Sons, Ltd. [source] Fuzzy controlled central heating systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2002Faruk Mendi Abstract In this paper a comparison study was carried out in order to understand how two different systems, classical and fuzzy logic control of central heating affect the economy and comfort of private homes or offices. Also a literature review was done to help decide which one of these systems is more effective. The objective of the fuzzy controller heating system is to estimate the actual heat requirement of the house. It uses a total of five inputs, four of which are derived from energy consumption curve, using conventional digital filtering techniques; the fifth is the average outdoor temperature, whereas, the classical control system burns diesel type fuel in its furnace to heat the water supply (boiler). From the boiler, the hot water is distributed by a pipe system to the individual radiators in the house. Thereby, it is shown that the fuzzy controlled heating system is more effective, also it maximizes the economy and the comfort of the consumer. Copyright © 2002 John Wiley & Sons, Ltd. [source] Sensitivity analysis of investments in the pulp and paper industry On investments in the chemical recovery cycle at a board millINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2002M. Karlsson Abstract In the pulp and paper industry, energy costs represents a relatively large proportion of the value of production. When investing in new equipment, considerations concerning boundary conditions, such as electricity and oil prices, are therefore of great importance. A vital requirement is the identification of other key parameters influencing production costs as well as possible interaction between these parameters. In this paper, a sensitivity analysis is accomplished by using an optimization model that minimizes the system cost combined with a systematic approach involving a statistical method. The paper analyses the possibilities of investing in a new chemical recovery cycle, including a new recovery boiler and evaporation plant, at a Swedish board mill. The study includes a survey of future changes, together with forecasts of boundary conditions, such as changes in the price of electricity and oil. Interactions between different parameters are also examined. Copyright © 2002 John Wiley & Sons, Ltd. [source] The evaluation of small cogeneration for residential heatingINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2002Kris R. Voorspools Abstract The decision whether or not to install small cogeneration for residential purposes mainly depends on individual economic considerations, combined with ecological awareness. Since in most cases, the economic balance is still unfavourable, government grants are considered in order to bridge this economic barrier. It is however still unclear how these grants are best spent to obtain an optimal environmental benefit. In the case of cogeneration, mainly static and simplified methods are used, completely neglecting the dynamic interaction between the cogeneration systems and the central power system and the dynamic response of the cogeneration units themselves. In this paper, these issues are discussed in two parts. The first part clarifies how an actual cogeneration unit, if necessary in combination with a back-up boiler and heat storage, will respond to a certain demand. For this purpose, experiments were performed to establish the transient and stationary behaviour of the system. It is shown that the transient heating of the cogeneration engine is rather slow (e.g. half an hour after cold start, the engine only produced 65% of the heat it would have in stationary regime) where the electric transient behaviour is negligible. In the second part of the paper, dynamic simulations are performed to quantify the impact (primary energy saving and reduction in greenhouse-gas emissions) of the massive installation of cogeneration for residential heating. Two important parameters are isolated. First, the interaction with the expansion of the central power system is very important. If the installation of cogeneration prevents the commissioning of new power plants, the potential energy saving and (especially) emission reduction are reduced. The second parameter is the annual use of the cogeneration units. Here, the potential energy saving and emission reduction increase with increasing annual use. Copyright © 2002 John Wiley & Sons, Ltd. [source] Optimal use of solar collectors for residential buildingsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2001Stig-Inge GustafssonArticle first published online: 5 JUN 200 Abstract Solar radiation is an abundant free resource which may be used in the form of solar heated water. This is achieved in solar collectors which, unfortunately, are expensive devices and, further, the warm water must be stored in accumulators,items which also cost money. This paper shows how we have optimized the situation for a block-of-flats in Sweden. In order to find this point we have used the minimum life-cycle cost (LCC) concept as a criterion. The best solution is therefore found when that cost finds its lowest value. It is also examined under which conditions solar collectors are part of the optimal solution and further it is calculated what happens if this optimal point is abandoned, i.e. how much will the LCC increase if other than optimal solutions are chosen. LCC optimization for multi-family buildings almost always results in a heating system with low operating costs such as district heating or dual-fuel systems where a heat pump takes care of the base load and an oil boiler the peak. The installation cost must, however, be kept to a reasonable level. Expensive solar panel systems are therefore normally avoided if the lowest LCC shall be reached, at least for Swedish conditions. This is so even if the solar system has a very low operating cost. For buildings where the only alternative energy source is electricity, solar collectors seem to be on the rim of profitability, i.e. for an energy price of about 0.6 SEK kWh,1. Copyright © 2001 John Wiley & Sons, Ltd. [source] Comprehensive process design study for layered-NOX -control in a tangentially coal fired boilerAICHE JOURNAL, Issue 3 2010Wei Zhou Abstract As emissions regulations for coal-fired power plants become stricter worldwide, layering combustion modification and post-combustion NOX control technologies can be an attractive option for efficient and cost-effective NOX control in comparison to selective catalytic reduction (SCR) technology. The layered control technology approach designed in this article consists of separate overfire air (SOFA), reburn, and selective noncatalytic reduction (SNCR). The combined system can achieve up to 75% NOX reduction. The work presented in this article successfully applied this technology to NRG Somerset Unit 6, a 120-MW tangential coal-fired utility boiler, to reduce NOX emissions to 0.11 lb/MMBtu (130 mg/Nm3), well under the US EPA SIP Call target of 0.15 lb/MMBtu. The article reviews an integrated design study for the layered system at Somerset and evaluates the performance of different layered-NOX -control scenarios including standalone SNCR (baseline), separated overfire air (SOFA) with SNCR, and gas reburn with SNCR. Isothermal physical flow modeling and computational fluid dynamics simulation (CFD) were applied to understand the boiler flow patterns, the combustible distributions and the impact of combustion modifications on boiler operation and SNCR performance. The modeling results were compared with field data for model validation and verification. The study demonstrates that a comprehensive process design using advanced engineering tools is beneficial to the success of a layered low NOX system. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Potential high temperature corrosion problems due to co-firing of biomass and fossil fuelsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 10 2008M. Montgomery Abstract Over the past few years, considerable high temperature corrosion problems have been encountered when firing biomass in power plants due to the high content of potassium chloride in the deposits. Therefore, to combat chloride corrosion problems co-firing of biomass with a fossil fuel has been undertaken. This results in potassium chloride being converted to potassium sulphate in the combustion chamber and it is sulphate rich deposits that are deposited on the vulnerable metallic surfaces such as high temperature superheaters. Although this removes the problem of chloride corrosion, other corrosion mechanisms appear such as sulphidation and hot corrosion due to sulphate deposits. At Studstrup power plant Unit 4, based on trials with exposure times of 3000 h using 0,20% straw co-firing with coal, the plant now runs with a fuel mix of 10% straw,+,coal. Based on results from a 3 years exposure in this environment, the internal sulphidation is much more significant than that revealed in the demonstration project. Avedøre 2 main boiler is fuelled with wood pellets,+,heavy fuel oil,+,gas. Some reaction products resulting from the presence of vanadium compounds in the heavy oil were detected, i.e. iron vanadates. However, the most significant corrosion attack was sulphidation attack at the grain boundaries of 18-8 steel after 3 years exposure. The corrosion mechanisms and corrosion rates are compared with biomass firing and coal firing. Potential corrosion problems due to co-firing biomass and fossil fuels are discussed. [source] Influence of novel cycle concepts on the high-temperature corrosion of power plantsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 5 2008Bettina BordenetArticle first published online: 29 MAY 200 Abstract The aim to reduce CO2 emissions has triggered the evaluation of new cycle concepts for power plants. CO2 -capture concepts are also evaluated to add on new and existing power plants. For combined cycle power plants (CCPP), different cycles are investigated such as integrated gasification (IGCC) or oxy-fuel firing. Besides the difference in combustion compared to a conventional CCPP, the environmental boundary conditions are changed and will affect the oxidation and corrosion life of the materials in the hot-gas path of the gas turbine and the heat-recovery steam generator. For the circulating fluidised bed power plants, the biomass co-firing and the oxy-fuel firing are also foreseen for CO2 -emission reduction. The fireside corrosion of the water walls will be influenced by these concepts and the changed fuel. The corrosion risk has been evaluated for two new power plant concepts: combined cycle with exhaust gas recirculation and pulverised coal-fired boiler with oxy-fuel firing. Based on this evaluation, the consequences for the testing conditions and the material selection have been discussed in detail. [source] On fusion of PCA and a physical model-based predictive control strategy for efficient load-cycling operation of a thermal power plantOPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 4 2007Girijesh Prasad Abstract Controlling a thermal power plant optimally during load-cycling operation is a very challenging control problem. The control complexity is enhanced further by the possibility of simultaneous occurrence of sensor malfunctions and a plethora of system disturbances. This paper proposes and evaluates the effectiveness of a sensor validation and reconstruction approach using principal component analysis (PCA) in conjunction with a physical plant model. For optimal control under severe operating conditions in the presence of possible sensor malfunctions, a predictive control strategy is devised by appropriate fusion of the PCA-based sensor validation and reconstruction approach and a constrained model predictive control (MPC) technique. As a case study, the control strategy is applied for thermal power plant control in the presence of a single sensor malfunction. In particular, it is applied to investigate the effectiveness and relative advantage of applying rate constraints on main steam temperature and heat-exchanger tube-wall temperature, so that faster load cycling operation is achieved without causing excessive thermal stresses in heat-exchanger tubes. In order to account for unstable and non-minimum phase boiler,turbine dynamics, the MPC technique applied is an infinite horizon non-linear physical model-based state-space MPC strategy, which guarantees asymptotic stability and feasibility in the presence of output and state constraints. Copyright © 2007 John Wiley & Sons, Ltd. [source] Urinary metal and polycyclic aromatic hydrocarbon biomarkers in boilermakers exposed to metal fume and residual oil fly ashAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 6 2005Sutapa Mukherjee MBBS Abstract Background Boilermakers are occupationally exposed to known carcinogens. Methods The association of urinary 1-hydroxy-pyrene (1-OHP), a biomarker of polycyclic aromatic hydrocarbon (PAH) exposure, with biomarkers of metal exposure (vanadium, chromium, manganese, nickel, copper, and lead) in boilermakers exposed to metal fume from welding and dust particulates from residual oil fly ash (ROFA) was examined. A repeated measures cohort study was conducted during the overhaul of an oil-fired boiler. Twice-daily urine samples were obtained for 5 days and analyzed for cotinine, 1-OHP, and metals. Generalized estimating equations (GEE) were used to model the multivariate relationship of 1-OHP to the explanatory variables. Results Metal and 1-OHP levels were determined for 165 urine samples from 20 boilermakers and these levels increased during the workweek. However, the 1-OHP level was not significantly associated with any individual metal level at any time point. Conclusion This suggests that boilermakers were occupationally exposed to PAH and metals, but 1-OHP as a PAH biomarker was unable to serve as a surrogate marker of metal exposure for the metals measured in this study. Am. J. Ind. Med. 47:484,493, 2005. © 2005 Wiley-Liss, Inc. [source] Methods for measuring the concentrations of SO2, and of gaseous reduced sulphur compounds in the combustion chamber of a circulating fluidized bed boilerTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2000Maríaa Joséa Fernández Abstract The present work was aimed at developing and improving methods for measurement of gaseous sulphur compounds in the combustion chamber of a fluidized bed boiler (FBB). The sampling of SO2 was improved by removing NH3 and H2O with a sorbent immediately after the probe. The concentration of reduced sulphur species was determined by means of two conventional SO2 analyzers and an intermediate converter, where the reduced species are oxidized to SO2. Gas phase sulphides were also sampled with a gas quenching probe by means of a basic solution which was subsequently analysed by wet chemistry. The methods were tested during coal combustion in a 12 MW circulating FBB without limestone for two cases of air-staging. Le but de ce travail était de développer et d'améliorer les méthodes de mesure des composés gazeux du soufre dam la chambre de combustion d'une chaudière à lit fluidisé. On a amélioré la prise d'échantillons de SO2 en retirant le NH3 et le H2O avec un sorbant tout de suite après la sonde. La concentration d'espéces réduites de soufre a été déterminée à l'aide de deux analyseurs de SO2 classiques et un convertisseur d'intermédiaires, où les espèces réduites sont oxydées en SO2. Des échantil-Ions de sulfures gazeux ont également été prélevés à l'aide d'une sonde de trempe du gaz en utilisant une solution basique qui a été analysée par la suite en chimie humide. Ces méthodes ont été testées lors de la combustion de charbon dans une chaudière à lit fluidisé circulant de 12 MW sans calcaire pour deux cas d'étagement de l'air. [source] Viscosity models for New Zealand black liquor at low solids concentrationsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010S.B. Alabi Abstract Availability of accurate models for prediction of the viscosity of black liquor (BL) from the chemical pulping of pine will facilitate its online monitoring and control and subsequently the optimisation of combustion in a recovery boiler. New Zealand (NZ) BL viscosity data are limited, and no predictive model is available. The viscosities of the NZ BL samples at solids concentrations (SCs) < 50% were obtained at temperature of 25,85 °C and shear rate up to ,2000 s,1. The samples showed Newtonian behaviour. Existing models from the literature and a binomial model developed in this work were used to fit the viscosity data as a function of SC and temperature. Accuracies of these models were examined for both the log-transformed and the untransformed viscosity data using coefficient of correlation (R) and maximum absolute relative error (MARE) (between the actual and predicted viscosities), respectively, as indices. Although the existing models fit NZ BL viscosity data well when they were log-transformed, they performed poorly when not transformed. Conversely, the new binomial model gave accurate predictions with both the log-transformed and untransformed viscosity data (R = 0.9997; MARE = 5.7%). It is concluded that at low SCs, the viscosity of Newtonian BL can be accurately predicted using the new binomial model. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd. [source] NOx emissions of an opposed wall-fired pulverized coal utility boilerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010Xiaotao Gao Abstract The present paper was addressed to the effects of operational variables and coal properties on NOx emission level of a 600-MW opposed wall-fired pulverized coal utility boiler. The in situ experiments were performed to study the effects of operational variables on boiler performance by changing individual variables while the other variables were held nearly constant on the basis of the nominal load operation. It was found that the oxygen level was a significant parameter to affect the NOx emission. The impacts of coal properties on NOx emission indicated that NOx emission level decreased with the increase of the ratio of the nitrogen content to low heating value because the volatile matter content in coal significantly influenced the in-flame NOx formation. Coal volatile content was the dominant parameter to affect fuel NOx formation through affecting the reducing condition in the inner near-burner zone when the low NOx burners were applied in the boiler. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Influence of oil-atomized air on flow and combustion characteristics in a 300 MWe down-fired boilerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010Zhengqi Li Abstract A method of admitting oil-atomized air into a furnace to adjust coal combustion in a down-fired boiler is described. Experiments with a small-scale furnace simulating a down-fired, pulverized-coal, 300-MWe utility boiler were carried out at a single-phase test facility to investigate the influence of oil-atomized air on the aerodynamic field in the furnace. With the acceleration of oil by secondary air, the primary air/fuel can reach a more distant position with respect to the burner nozzle and the volume of the recirculation zone shrinks. Industrial experiments were also performed in a 300-MWe full-scale boiler. The gas temperature distribution along the primary air/fuel flow in the furnace and the gas components in the near-wall region were measured with the dampers of the oil-atomized air box open and closed. When open, the oil-atomized air does not impede the ignition of the primary air/fuel and can carry the primary air/fuel to a position much deeper in the furnace, resulting in a lowered carbon content in the fly ash. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Mercury and halides emissions from 200 MW pulverized coal combustion boilerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010Hui Wu Abstract Mercury emission from coal-fired power plants is the major industrial source of mercury pollution in China. For a better understanding about the coal combustion Hg emission in China, a field measurement was conducted on a 200 MW pulverized coal fired boiler. Halides being proved to be mercury transformation participators, the U.S. EPA (Environmental Protection Agency) recommended Ontario Hydro method (OHM) and EPA Method 26A were adopted to determine the speciation of Hg and halides in postcombustion flue gases, respectively. Results indicated that, as the flue gas cooling down, the percentage of oxidized mercury in total gas phase mercury (Hg2+(g)/HgT(G)) increased from 41% to about 74% across the electrostatic precipitator (ESP) outlet. Oxidized mercury (Hg2+(g)) was more apt to be absorbed onto the fly ash. The main halides measured in flue gas were HF and HCl, while the concentrations of Cl2 and HBr were extremely low and no Br2 was detected in flue gas. Analysis indicated that acid flue gas components, such as HCl, HF, SO2 and NO, showed a certain extent of promotion on Hg oxidation. The measured mercury emission factor (EMF) in this test was 5.63 g/1012J (13.1 lb/1012Btu). Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] SCT reaction kinetics model and diffusion for p.c. combustion in TGAASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010Pei-Fang Fu Abstract Recently, the process of char burnout is extensively concerned. Global model used widely cannot predict the extent of char burnout at the later burning stage. For the need of predicting the burnout degree in industrial pulverized coal (p.c.) fired furnace by making use of the experimental data from such as thermogravimetry analysis (TGA) and drop tube furnace, based on the simple collision theory (SCT) of chemical reaction kinetics, the SCT model is educed. The p.c. combustion is considered as the results of strike and oxidation of oxygen molecules on the surface of p.c. particles, and the frequency of effective strike was determined by Boltzmann factor. Strike and oxidation occur on the oxygen accessible specific surface area (OASA). Chemical regime controlled is at temperature below 1200 K, and molecules diffusion regime controlled is at the temperature above 1600 K, at which OASA corresponds to the specific surface area with pore diameter more than 38 nm of p.c particles in coal-fired boiler. The OASA of p.c. particles increases with the char burning, for the particles swells, shrinks and cracks. The burning rates calculated based on SCT model have shown good correspondence with experimental data reported. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Response surface modeling and optimization for production of ammonia from urea in a batch reactorASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009J. N. Sahu Abstract Ammonia is applied to removal of NOx contaminates contained in a flue gas stream from energy producing boilers and increase of efficiency of an electrostatic precipitator for removal of fly ash from flue gas stream from a boiler using fossil fuel. In this study, urea hydrolysis for production of ammonia, in different application areas that requires safe use of ammonia, was investigated in a batch reactor. The single and combined effects of operating parameters such as initial feed concentrations, temperature, time and stirring speed on the production of ammonia from urea were analyzed using response surface methodology (RSM). A 24 full factorial central composite experimental design was employed. Analysis of variance (ANOVA) showed a high coefficient of determination value (R2 = 0.976) and satisfactory prediction second-order regression model was derived. The optimum production conditions were determined as temperature, 180 °C; initial feed concentrations, 22.24 wt% of urea; time, 74.9 min and stirring speed, 1150 rpm. At optimum conversion conditions, the conversion of urea for production of ammonia was found to be 75.65%. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Combustion modeling of blended coal in a 300-MW tangentially fired boiler using a two-mixture-fraction modelASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009Qing-Yan Fang Abstract The combustion process in a 300-MW tangentially fired boiler furnace fired with a blended coal has been numerically simulated. The blended coal contains a low-quality bituminous coal and anthracite and it was injected into the furnace from different burner nozzles. In order to better capture the combustion characteristics, a two-mixture-fraction model has been developed to model the combustion process of each individual coal of the blend. The two mixture fractions were used to separately track the combustion processes of the two component coals to reveal the effect of the combustion of the two coals on the chemical reactions in local zones of the furnace. The sum of the two mixture fractions was used to calculate the gas-phase turbulent combustion. Temperature measurements in the furnace were carried out by a flame image processing technique for model validation. Simulation results show that the temperature and oxygen concentration on the horizontal cross-sections close to the primary air burner nozzles in the furnace are nonuniformly, but symmetrically distributed across the four corners. The temperatures predicted by the simulation agree well with those measured by the flame image processing technique with a maximum error of 8.65%. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||||||||