Uprating Through Condenser Reconstruction - Balcke-Dürr ...

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coMpReHenSi V e coMpetence in SeRVice anD Heat e XcH anG eRS More than 125 years of product competence, the innovative force of our inter national teams of ex perts as well as constant re search and development are the basis of our global power strategy. Advantages to our customers: Complete solutions and services from one single source – quick, flexible and efficient. Count on us and benefit from our product and service competence. RANGE OF PRODUCTS AND SERVICES Power plant components Development, design, manufacture, erection and commissioning of: • Surface steam condensers • Feedwater heaters • Deaerators/feedwater tanks • Moisture separator reheaters • poWeRSep ® high velocity separators • poWeRVane ® chevron type separators Air and flue gas systems Development, design, manufacture, erection and commissioning of: • Regenerative air and gas heaters of the RotHe MÜHle ® and Ljungström types • Air pollution control equipment RotHeMÜHle ® design • bi-coRona ® electrostatic precipitators • Bag filters • Delta WinG ® static gas mixers for use in DeNOx systems and optimisation of dust collection efficiency in eSps Boiler services and general power plant services • Engineering • Manufacture • Erection • Maintenance and upkeep • Spare parts • Provision and management of overhaul services • Boiler modernisation and modification • Replacement and modernisation of power plant components as well as air and flue gas systems
Uprating Through Condenser Reconstruction Uprating Through Condenser Reconstruction J. Scheurlen, R. Scharf and W. Schulz Abstract Uprating Through Condenser Reconstruction Due to necessary modifications to the feed water chemistry at Stade nuclear power plant, the turbine condensers fitted with brass tubes have been converted to use austenitic cooling water tubes. At the same time, a completely new design of tube bundle and air cooling system has been installed. A significant improvement in heat transfer and considerably more effective air extraction and also increased net output by up to 4 MW have been attained using the new condenser. Kurzfassung Authors Leistungserhöhung durch Kondensatorumbau Durch die notwendige Änderung der Speisewasserchemie im Kernkraftwerk Stade wurden die mit Messingrohren ausgerüsteten Turbinenkondensatoren auf austenitische Kühlwasserrohre umgerüstet. Zugleich wurde eine völlig neue Konstruktion der Rohrbündel und des Luftkühlersystems eingesetzt. Mit dem neuen Kondensator wird eine deutlich bessere Wärmeübertragung und eine erheblich wirkungsvollere Luftabsaugung sowie eine um bis zu 4 MW gesteigerte Nettoleistung erreicht. Dipl.-Ing. J. Scheurlen Dr.-Ing. R. Scharf PreussenElektra AG Hanover/Germany Dipl.-Ing. W. Schulz Balcke-Dürr AG Ratingen/Germany In 1987, the operator of the Stade nuclear power plant (KKS) faced the task of adjusting the feedwater chemistry to higher ammonia (NH3) contents in order to create more favourable conditions for steam generator operation. This adjustment made it necessary to replace all the cupriferous materials in the steam circuit as it is a well-known fact that copper and ammonia are not compatible. The most extensive individual measure in connection with this material change involved the turbine condensers which have a total of 43,000 brass tubes (total length 570 km) and yellow metal tubesheets. Difficulties with ammonia corrosion occurred even with the relatively low NH3 contents of the previous mode of operation and this led to repairs having to be carried out. So-called air pockets, in which the non-condensable gases including an increased concentration of NH3 occurred, formed due to the unfavourable design of the tube fields. Various proposals were investigated as a preliminary step to the required reconstruction measures. The comparison in Ta b l e 1 shows that the concept involving completely prefabricated bundle modules (variant 6) could be implemented within an extremely short period, thus offering decisive cost advantages. The reconstruction times required for all variants involving retubing on the jobsite were considerably longer than the time required for manufacture in the workshop. Moreover, the poorer conductivity of the copper-free tube material would have meant a definite reduction in the turbo generator output if the tube layout remained unchanged. Operating experience with turbo generators which have been reconstructed in this way confirmed this [1]. It is possible to avoid such undesirable loss of output when carrying out the reconstruction on the jobsite using a more up-to-date tube Table 1. Concepts for the reconstruction of the condenser in the KKS. layout, but only at the expense of significantly longer inspection times. The concept involving condensers completely prefabricated in the workshop (variant 5) also proved to be uneconomic. Design The thermodynamic design data were determined after checking how the turbo generator is used: Cooling water inlet temperature 9.8 °C Cooling water mass flow 4 x 7,425 kg/s Heat flow to be discharged 1,214 MW The external dimensions of the bundle modules were to a great extent determined by the existing condenser shell. A height limitation due to the concrete crossbeam of the power house made the situation more difficult. The optimum was found to be a cooling surface area of 37,820 m2 for the entire condenser with a tube outer diameter of 22 mm, a condenser pressure of 34.7 mbar thus being guaranteed. Titanium and stainless steel were considered as tube material. The advantages of titanium are: − somewhat better thermal conductivity − unsusceptibility to standstill corrosion The advantages of stainless steel are: − greater admissible spacing of the supporting walls, − lower price As no corrosion had occurred on the stainless steel tubes (material no 1.4439) used for re- 1 2 3 4 5 6 Measure Retubing and new tubesheets Prefabricated condensers (Condenser modules) Tube layout Unchanged Modernised Manufacture Jobsite Workshop Prefabricated tube internals (Bundle modules) Outages x calendar days 2 x 81 1 x 97 2 x 100 1 x 122 2 x 50 1 x 39 Turboset output Decrease Increase Cost factor 5.4 4.1 7.0 5.1 3.8 1 3
Page 1: Special publication a 98e Uprating
Page 5 and 6: The four bundle modules were constr
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