Simulation of a coal-fired power plant using mathematical programming algorithms in order to optimize its efficiency

Tzolakis, G.; Papanikolaou, P.; Kolokotronis, Dimitrios; Samaras, Nikolaos; Tourlidakis, A.; Tomboulides, Ananias

doi:10.1016/j.applthermaleng.2012.04.051

Cited by 33 publications

(15 citation statements)

References 11 publications

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“…For this reason, steam superheaters are modeled mathematically or monitored to avoid overheating of tubes. Simulations and optimization results of a 300 MW lignite-fired power boiler are presented by Tzolakis et al [12].…”

Section: Introductionmentioning

confidence: 98%

Effect of scale deposits on the internal surfaces of the tubes on the superheater operation

Trojan¹,

Taler²

2013

Archives of Thermodynamics

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A mathematical model of the steam superheater exchanger with distributed parameters has been developed. Scale deposits were assumed to be present on the internal tube surfaces. It was assumed that the inner tube surfaces are covered by a thin layer of scale deposits. The finite volume method was used to solve partial differential equations describing flue gas, tube wall and steam temperature. The developed modeling technique can especially be used for modeling tube heat exchangers when detail information on the tube wall temperature distribution is needed. The numerical model of the superheater developed in the paper can be used for modeling of the superheaters with complex flow arrangement accounting scales on the internal tube surfaces. Using the model proposed the detailed steam, wall and flue gas temperature distribution over the entire superheater can be determined. The steam pressure distribution along its path flow and the total heat transfer rate can also be obtained. The calculations showed that the presence of scale on the internal surfaces of the tubes cause the steam temperature decrease and the heat flow rate transferred from the flue gas to the steam. Scale deposits on the inner surfaces of the tubes cause the tube wall temperature growth and can lead to premature wear of tubes due to overheating. Nomenclature d h -hydraulic diameter of the superheater tube (for a circular tube, this equals the inner diameter of the tube), m he -equivalent heat transfer coefficient, W/m 2 K hg -heat transfer coefficient on the flue gas side, W/m 2 K hs -heat transfer coefficient at the inner tube surface, W/m 2 K ka -ash deposit thermal conductivity, W/mK ks -iron oxides or scales thermal conductivity, W/mK kw -tube material thermal conductivity, W/mK Lr -tube length, ṁ ms -steam mass flow rate, kg/s N -number of finite volumes on the tube length p -static pressure, Pa r -radius, m ra -outer radius of deposit layer, m rin -inner radius, m ro -outer radius, m s -coordinate along the flow path in direction of flow, m s1 -longitudinal pitch perpendicular to the flue gas flow direction,m s2 -longitudinal pitch parallel to the flu gas flow direction, m Ta -deposit layer temperature o C Tg -flue gas temperature, o C Tg -mean gas temperature over the row thickness, o C Ts -steam temperature, o C Tw -tube wall temperature, o C w -steam velocity, m/s x + -dimensionless coordinate in the steam flow direction y + -dimensionless coordinate in the flue gas flow directionGreek symbols δa -thickness of ash deposits, m δs -thickness of iron oxide or scale deposits, m φ -angle between tube axis and horizontal plane, m ρ -steam density, kg/m 3 ξ -friction factor

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Section: Introductionmentioning

confidence: 98%

Effect of scale deposits on the internal surfaces of the tubes on the superheater operation

Trojan¹,

Taler²

2013

Archives of Thermodynamics

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“…The combustion chamber and the convective section of the boiler can be calculated by combining threedimensional CFD fire side models with one-dimensional tube side model for simulation water, water-steam or steam flow in the tubes. However, the modeling of thermal and hydraulic processes in steam superheaters and economizers on the tube side is very [17]. A heat recovery steam generator (HRSG) was optimized by Behbahani-nia using the genetic algorithm [18].…”

Section: Introductionmentioning

confidence: 99%

“…In the last decade, CFD (Computational Fluid Dynamics) modeling was used to analyze the flow and thermal processes occurring in the combustion chambers and convection passages on the fluegas side of coal-fired boilers [11][12][13][14][15][16][17][18]. Despite the development of computers with high computational power, it is not possible simultaneous CFD simulation of phenomena on the flue gas side and the water-steam side.…”

Section: Introductionmentioning

confidence: 99%

Thermal simulation of superheaters taking into account the processes occurring on the side of the steam and flue gas

Trojan

Taler

2015

Fuel

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“…Because of this, steam superheaters are modeled mathematically or monitored to avoid overheating of tubes. CFD simulations and optimization results of a 300 MW lignite-fired power boiler are presented by Tzolakis et al [42]. A heat recovery steam generator (HRSG) was optimized by Behbahaninia using the genetic algorithm [43].…”

Section: Identification Of Thermal Boundary Conditions In Heat Exchanmentioning

confidence: 99%

Solving Inverse Heat Transfer Problems When Using CFD Modeling

Ludowski¹,

Taler²,

Taler³

2016

Numerical Simulation - From Brain Imaging to Turbulent Flows

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The chapter presents solving steady-state inverse heat transfer problems using Computational Fluid Dynamics (CFD) software. Two examples illustrate the application of the proposed method. As the first inverse problem determining the absorbed heat flux to water walls in furnaces of steam boilers is presented in detail. Three different measurement devices (flux tubes) were designed to identify steady-state boundary conditions in water wall tubes of combustion chambers. The first meter is made of a short eccentric tube in which four thermocouples on the fire side below the inner and outer tube surfaces are installed. The fifth thermocouple is situated at the rear of the tube on the housing side of the water wall tube. The second meter has two longitudinal fins that are welded to the bare eccentric tube. In the third option of the instrument, the fins are attached to the water wall tubes but not to the flux tubes as in the second version of the flux tubes. The first instrument is used to measure the heat flux to water walls made from bare tubes, while another two heat flux tubes are designated for measuring the heat flux to membrane walls. Unlike the existing devices, the flux tube is not attached to neighboring water-wall tubes. The absorbed heat flux on the outer surface and the heat transfer coefficient at the inner surface of the flux tube are determined from temperature measurements at internal points. The thermal conductivity of the flux-tube material is a function of temperature. The nonlinear inverse problem of heat conduction (IHCP) is solved using the least-squares method. Three unknown parameters are determined using the Levenberg-Marquardt method. In each iteration, the temperature distribution in the cross section of the heat flux instrument is determined using the ANSYS/CFX software.Another inverse heat transfer problem will be a CFD simulation carried out for the platen superheater placed in the combustion chamber of the circulating fluidized bed (CFB) boiler. Velocity, pressure, and temperature of the steam, as well as the temperature of the tube wall with the complex cross section, were computed using the ANSYS/ CFX software. The direct and inverse problems were solved. In the first inverse problem, the heat transfer coefficient on the flue-gas side was determined based on the meas- ured steam temperature at the inlet and outlet of the three pass steam superheater. In the second inverse problem, the inlet steam temperature and the heat transfer coefficient on the flue-gas side were estimated using measured steam temperatures at selected locations of the superheater. The Levenberg-Marquardt method was also used to solve the second inverse problem. At every iteration step, a direct conjugate heat transfer problem was solved using the ANSYS/CFX software. The CFX program was called and controlled by an external program written in Python language. The LevenbergMarquardt algorithm was also included in the Python program.

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Simulation of a coal-fired power plant using mathematical programming algorithms in order to optimize its efficiency

Cited by 33 publications

References 11 publications

Effect of scale deposits on the internal surfaces of the tubes on the superheater operation

Effect of scale deposits on the internal surfaces of the tubes on the superheater operation

Thermal simulation of superheaters taking into account the processes occurring on the side of the steam and flue gas

Solving Inverse Heat Transfer Problems When Using CFD Modeling

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