The Experts below are selected from a list of 597 Experts worldwide ranked by ideXlab platform
Dawid Tale - One of the best experts on this subject based on the ideXlab platform.
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numerical model of a steam superheater with a complex shape of the tube cross section using control volume based finite element method
Energy Conversion and Management, 2016Co-Authors: Pawel Madejski, Dawid Tale, Ja TaleAbstract:Abstract In modern utility boilers, characterized by high values of steam pressure and temperature, the individual superheater stages and also the individual passes are made of different low alloy steel grades. The use of tubes having a complex shape of cross section allows the building of the platen with smooth side surfaces, which are arranged in the upper part of the combustion chamber. This avoids the erosion of the superheater tubes and deposition of slag and ash in the spaces between adjacent tubes. The Superheaters of this type are widely used in CFB boilers. To select the appropriate steel for each pass and each stage, the maximum wall temperature of tube need to be determined. Steam and tube wall temperature were computed in the superheater using a method proposed in the paper and compared with the results obtained by CFD simulation using Star-CCM+ software. The method presented in the paper can be easily applied to the modeling of flow and thermal processes in Superheaters with complicated flow arrangements which usually are found in steam boilers. The advantage of the proposed method is a short computing time in comparison with detailed and complex 3D models. Using the methodology developed in the article, time needed to obtain final results at steady-state conditions can be lower even dozen times in comparison to CFD calculations. The proposed calculation method can be used in the design of modern subcritical and supercritical boilers, in which the temperature of the live steam is very high. Very careful and precise calculations of steam and tube walls temperature along the steam flow path will avoid the overheating of the tube material.
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MODELING OF SUPERHEATER OPERATION IN A STEAM BOILER
2015Co-Authors: Marci Troja, Dawid Tale, Pio DzierwaAbstract:A numerical method for modeling actual steam Superheaters is presented. The finite volume method was used to determine flue gas, tube wall and steam temperature. The numerical technique presented in the paper can especially be used for modeling boiler Superheaters with a complex tube arrangement when detail information on the tube wall temperature distribution is needed. The method of modeling the superheater can be used both in the design, performance as well as in upgrading the Superheaters. If the steam temperature at the outlet of the superheater is too low or too high, the designed outlet temperature can be achieved by changing a flow arrangement of the superheater. For example, the impact of the change of the counter to parallel flow or to mixed flow can be easily assessed. The presented method of modeling is a usefu
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thermal simulation of Superheaters taking into account the processes occurring on the side of the steam and flue gas
Fuel, 2015Co-Authors: Marci Troja, Dawid TaleAbstract:Abstract Superheater model was used to analyzing the impact of ash deposits on the outer tube surfaces and scales formed on the inner tube surfaces on the heat flow rate transferred from the flue gas to the steam. The influence of uneven heating of parallel superheater tubes on the flow and temperature maldistribution was also examined. Excessive heating of some tubes reduces the mass flow rate of the steam flowing through these tubes. It may result in overheating of the tube material. Excessive local tube heating by a higher temperature flue gas, in combination with lower steam mass flow rate through each tube, can contribute to the overheating of the tube material. Ash fouling causes a significant decrease in heat flux absorbed by the steam and lowering the temperature of the tube metal. Scale depositions on the inner surface of the tube cause a big increase in wall temperature of superheater tubes despite a decrease in the heat flux transferred from the flue gas to the steam.
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analysis of temperature and stress distribution of superheater tubes after attemperation or sootblower activation
Energy Conversion and Management, 2013Co-Authors: Pawel Madejski, Dawid TaleAbstract:Abstract Superheaters are characterized by high metal temperatures due to higher steam temperature and low heat transfer coefficients on the tube inner surfaces. Superheaters have especially difficult operating conditions, particularly during attemperator and sootblower activations, when temperature and steam flow rate as well as tube wall temperature change with time. A detailed thermo-mechanical analysis of the superheater tubes makes it possible to identify the cause of premature high-temperature failures and aids greatly in the changes in tubing arrangement and improving start-up technology. This paper presents a thermal and strength analysis of a tube “double omega”, used in the steam Superheaters in CFB boilers.
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simplified analysis of radiation heat exchange in boiler Superheaters
Heat Transfer Engineering, 2009Co-Authors: Dawid Tale, Ja TaleAbstract:This article describes the determination of the radiation heat transfer coefficient in radiant platen Superheaters and on convective heating surfaces. A new simple formula for determination of the heat transfer coefficient is derived on the basis of a diffusivity model of radiation heat exchange. The radiation heat transfer coefficients are determined on the tube surface in a convective evaporator, in a second stage convective heat superheater, and in a platen superheater of a pulverized coal-fired boiler. The calculations were carried out applying the method presented in this article, the Central Institute for Boilers and Turbines method, and formulas resulting from the analysis of heat exchange in an enclosure containing a gas of a constant temperature. In order to assess the accuracy of the achieved results, the flow of flue gas and the heat exchange were modeled using a commercial computational fluid dynamics program.
Luis I Diez - One of the best experts on this subject based on the ideXlab platform.
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towards soot blowing optimization in Superheaters
Applied Thermal Engineering, 2013Co-Authors: Enrique Teruel, Luis I DiezAbstract:Abstract This paper seeks the optimization of steam consumptions dedicated to ash removal in large-sized Superheaters operating at coal-fired utility boilers. The methodology consists of the design of a thermal model aiming at the real-time calculation of the fouling rates, the statistical fitting of the computed rates to obtain their time evolution and the assessment of optimized soot-blowing manoeuvres. Fouling rates are estimated by means of global thermal resistances, since local deposition is not feasible from available, standard measurements. The methodology is applied to the upper Superheaters of a selected 350 MWe utility boiler, where significant steam rates are actually consumed. The results from the comparison of the heat transfer gains in this case-study show that energy savings can be attained by adopting new soot-blowing schedules in the plant. The methodology can be easily implemented in other coal-fired utility boilers, without demanding special instrumentation or computation requirements.
Peter Viklund - One of the best experts on this subject based on the ideXlab platform.
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superheater corrosion in biomass and waste fired boilers characterisation causes and prevention of chlorine induced corrosion
2013Co-Authors: Peter ViklundAbstract:Biomass and waste fired boilers suffer severely from corrosion of critical components such as superheater tubes. In this work high temperature corrosion of superheater alloys, and methods to mitiga ...
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corrosion of superheater materials in a waste to energy plant
Fuel Processing Technology, 2013Co-Authors: Peter Viklund, Anders Hjornhede, Pamela Henderso, Annika Stalenheim, Rachel PetterssoAbstract:A major drawback when generating electricity from waste-fired boilers is the rapid corrosion of critical components such as superheater tubes. In this work a number of commonly-used superheater mat ...
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effect of sulphur containing additive on initial corrosion of superheater tubes in waste fired boiler
Corrosion Engineering Science and Technology, 2009Co-Authors: Peter Viklund, Anders Hjornhede, Pamela Henderso, Rachel Pettersso, P SjovallAbstract:The major drawback to generating electricity from waste fired boilers is the rapid corrosion of Superheaters which increases the maintenance costs. Within the last few years, it has been shown that ...
Pawel Madejski - One of the best experts on this subject based on the ideXlab platform.
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numerical model of a steam superheater with a complex shape of the tube cross section using control volume based finite element method
Energy Conversion and Management, 2016Co-Authors: Pawel Madejski, Dawid Tale, Ja TaleAbstract:Abstract In modern utility boilers, characterized by high values of steam pressure and temperature, the individual superheater stages and also the individual passes are made of different low alloy steel grades. The use of tubes having a complex shape of cross section allows the building of the platen with smooth side surfaces, which are arranged in the upper part of the combustion chamber. This avoids the erosion of the superheater tubes and deposition of slag and ash in the spaces between adjacent tubes. The Superheaters of this type are widely used in CFB boilers. To select the appropriate steel for each pass and each stage, the maximum wall temperature of tube need to be determined. Steam and tube wall temperature were computed in the superheater using a method proposed in the paper and compared with the results obtained by CFD simulation using Star-CCM+ software. The method presented in the paper can be easily applied to the modeling of flow and thermal processes in Superheaters with complicated flow arrangements which usually are found in steam boilers. The advantage of the proposed method is a short computing time in comparison with detailed and complex 3D models. Using the methodology developed in the article, time needed to obtain final results at steady-state conditions can be lower even dozen times in comparison to CFD calculations. The proposed calculation method can be used in the design of modern subcritical and supercritical boilers, in which the temperature of the live steam is very high. Very careful and precise calculations of steam and tube walls temperature along the steam flow path will avoid the overheating of the tube material.
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analysis of temperature and stress distribution of superheater tubes after attemperation or sootblower activation
Energy Conversion and Management, 2013Co-Authors: Pawel Madejski, Dawid TaleAbstract:Abstract Superheaters are characterized by high metal temperatures due to higher steam temperature and low heat transfer coefficients on the tube inner surfaces. Superheaters have especially difficult operating conditions, particularly during attemperator and sootblower activations, when temperature and steam flow rate as well as tube wall temperature change with time. A detailed thermo-mechanical analysis of the superheater tubes makes it possible to identify the cause of premature high-temperature failures and aids greatly in the changes in tubing arrangement and improving start-up technology. This paper presents a thermal and strength analysis of a tube “double omega”, used in the steam Superheaters in CFB boilers.
Rachel Pettersso - One of the best experts on this subject based on the ideXlab platform.
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corrosion of superheater materials in a waste to energy plant
Fuel Processing Technology, 2013Co-Authors: Peter Viklund, Anders Hjornhede, Pamela Henderso, Annika Stalenheim, Rachel PetterssoAbstract:A major drawback when generating electricity from waste-fired boilers is the rapid corrosion of critical components such as superheater tubes. In this work a number of commonly-used superheater mat ...
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effect of sulphur containing additive on initial corrosion of superheater tubes in waste fired boiler
Corrosion Engineering Science and Technology, 2009Co-Authors: Peter Viklund, Anders Hjornhede, Pamela Henderso, Rachel Pettersso, P SjovallAbstract:The major drawback to generating electricity from waste fired boilers is the rapid corrosion of Superheaters which increases the maintenance costs. Within the last few years, it has been shown that ...
