Computer modeling of a convective steam superheater

Open access


Superheater is for generating superheated steam from the saturated steam from the evaporator outlet. In the case of pulverized coal fired boiler, a relatively small amount of ash causes problems with ash fouling on the heating surfaces, including the superheaters. In the convection pass of the boiler, the flue gas temperature is lower and ash deposits can be loose or sintered. Ash fouling not only reduces heat transfer from the flue gas to the steam, but also is the cause of a higher pressure drop on the flue gas flow path. In the case the pressure drop is greater than the power consumed by the fan increases. If the superheater surfaces are covered with ash than the steam temperature at the outlet of the superheater stages falls, and the flow rates of the water injected into attemperator should be reduced. There is also an increase in flue gas temperature after the different stages of the superheater. Consequently, this leads to a reduction in boiler efficiency. The paper presents the results of computational fluid dynamics simulations of the first stage superheater of both the boiler OP-210M using the commercial software. The temperature distributions of the steam and flue gas along the way they flow together with temperature of the tube walls and temperature of the ash deposits will be determined. The calculated steam temperature is compared with measurement results. Knowledge of these temperatures is of great practical importance because it allows to choose the grade of steel for a given superheater stage. Using the developed model of the superheater to determine its degree of ash fouling in the on-line mode one can control the activation frequency of steam sootblowers.

[1] Wessel B., Rüsenberg D., Schlenkert J.U., Thiele I., Karkowski G.: Betriebserfahrungen mit dem Block Niederaußem K. VGB PowerTech 11(2006), 47–51.

[2] Taler J. (Ed.): Thermal and flow processes in large power boilers. Modelling and monitoring. PWN, Warsaw 2010.

[3] Hewitt G.F., Shires G.L., Bott T.R.: Process Heat Transfer. CRC Press – Begell House, Boca Raton 1994.

[4] Shah R.K., Sekulić D.P.: Fundamentals of heat exchanger design. Wiley, Hoboken 2003.

[5] Kakaç S., Liu H.: Heat Exchangers: Selection, Rating, and Thermal Design, 2nd Edn., CRC Press – Taylor & Francis Group: Boca Raton 2002.

[6] Lokshin V.A., Peterson D.F., Schwarz A.L.: Standard Methods of Hydraulic Design for Power Boilers. Hemisphere Publishing, Washington – New York – London 1998.

[7] Kuznetsov N.W., Mitor W.W., Dubovski I.E., Karasina E.S. (Eds.): Thermal Calculations of Steam Boilers (Standard Method), 2nd Edn., Energia, Moscow 1973.

[8] Lin Z.H.: Thermo-Hydraulic Design of Fossil-Fuel-Fired Boiler Components [in:] S. Kakaç (Ed.): Boilers, Evaporators, and Condensers. John Wiley & Sons, Hoboken 1991, 363–469.

[9] Taler J., Trojan M., Taler D.: Monitoring of Ash Fouling and Internal Scale Deposits in Pulverized Coal Fired Boilers. Nova Science Publishers, New York 2011.

[10] French D.N.: Metallurgical failures in fossil fired boilers, 2nd Edn., John Wiley & Sons, New York 1993.

[11] CFX-ANSYS 15 Theory guide. ANSYS, Inc. Canonsburg, USA.

[12] Launder B.E., Spalding D.B.: The numerical computation of turbulent flows. Comput. Method. Appl. M. 3(1974), 2, 269–289.

[13] Versteeg H.K., Malalasekera W.: An Introduction to Computational Fluid Dynamics: The Finite Volume Method. Pearson Education Limited 2007.

[14] Taler D., Trojan M., Taler J.: Mathematical modelling of cross-flow tube heat exchangers with the complex flow arrangement. Heat Transfer Eng. 35(2014), 11-12, 1334-1343.

[15] TableCurve 2d. Systat Software Inc. 2002

[16] HyperMesh 12.0 - Altair HyperWorks 12.0. Altair Engineering Inc. 2013.

Archives of Thermodynamics

The Journal of Committee on Thermodynamics and Combustion of Polish Academy of Sciences

Journal Information

CiteScore 2016: 0.54

SCImago Journal Rank (SJR) 2016: 0.319
Source Normalized Impact per Paper (SNIP) 2016: 0.598


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