Abstracts - VGB PowerTech Journal 12/2006

VGB Congress “Power Plants 2006“

The VGB Congress “Power Plants” took place in Dresden, 27th to 29th September 2006 under the auspices of the Federal Minister for Economics and Technology, Michael Glos. The motto of this year’s Congress was “Future becomes Reality – Investments in New Power Plants“. More than 1,200 participants from Germany and abroad attended the plenary and technical lectures on the topics “Market and Competition“ as well as “Technology, Operation and Environment“ for information and discussion. Special papers were dealing with further issues like “Generation Market in Europe”, “Clean Power Technology Platform“, French policy for new power plants as well as potentials and technology of renewables. The Congress was rounded off by a comprehensive side-programme and technical visits.

Reaction Mechanisms of Ferritic Materials During Low-NOx Combustion of Sulphurous Lignite

Thomas Brunne, Hubertus Altmann, Hartmut Schettler, Andreas Knieschke, Peter Seifert, Bernd Meyer

During the analysis of combustion chambers, untypical deposits were detected at the membrane walls. They were the reasons for comprehensive gas analysis measurements at combustion chambers of lignite steam generators to identify development mechanisms of these deposits. Of special interest was the concentration of oxygen, carbon monoxide and hydrosulphide near the ferritic steal. Measures to conserve protective ferrous oxides on the basic material and to reduce the formation of iron sulphides should be integrated into the next revision of the VGB NOx manual. (EN)

New Developments in the Field of Condenser Tubes – Bimetal Tubes, Surface-textured Tubes and Enhanced Copper Alloys

Andreas Gahl

Spiralling raw material prices along with the limited availability of titanium make it necessary to find new alternatives for the manufacture of condenser tubes. Based on initial experience, two quite different approaches seem to be the most promising from an economic and ecological point of view: The recycling of metal from copper alloy condenser tubes and reducing the number of condenser tubes needed by raising heat conduction performance through the use of surface-textured tubes.

Protective Spray Coatings in Fluidised Bed Systems

Rolf Jürgensen, Emmanuil Protogerakis

The continuous fluidisation of solid substances (ash, coal, limestone etc.) in fluidised bed systems results in abrasion, erosion and even corrosion of the individual equipment components. Various protective measures are used, depending on the conditions of usage and geometry of the parts at risk. These include cladding, small metal pins coupled with a ceramic mass, half-pipes and SiC tiles, as well as various forms of coatings, including thermal spray coatings.

Experience in Wearing Protection Measures for Water Walls of CFB Combustion Systems

Bernhard Röper, Fred Kaminski

The water walls of combustion chambers in CFB plants are exposed to strong erosion in the typical problem areas of older plants such as the interface between furnace wall and refractory lining, roof and corners of the combustion chamber and the cyclone inlet area. In the first years of operation, it became evident in RWE Power plants that thermal coatings of the state of the art at that time did not prove their worth on a permanent basis, so that other measures had to be taken to combat erosion. These wearing protection measures are described and evaluated on the basis of long-term wear measurements. If these measures are applied, the combustion chamber's water walls should be able to be maintained over the service life of a plant without an extensive replacement being required. Under the boundary conditions described, thermal coatings will continue to be unnecessary in future. (EN)

The Dry Lignite-fired Power Plant

Frank Schwendig, Hans-Joachim Klutz, Johannes Ewers

From about 2015 on, the dry lignite-fired power plant will be the new standard in the lignite sector. The efficiency of this power plant will be over 10%, relatively, above that of today’s modern lignite-fired power plants. It is based on the WTA technology (fluidised bed drying with internal waste heat utilisation) developed by RWE to pre-dry the lignite and recover the drying energy. In 2008/2009, tests will be performed in the BoA 1 unit at Niederaußem to secure this technology for commercial operation.

Potentials und Operating Experience of the Utilisation of Substitute Fuels at the Jänschwalde Lignite-fired Power Plant Site

Frank Mielke, Hans-Michael Kohde, Reinhard Schneider, Thomas Hörtinger

A reliable operation of the power plant equipment, and in particular the trouble-free operation of the conveying and proportioning plants in the receiving and proportioning facilities for substitute fuels will only be possible if the contractually agreed quality parameters are kept. Within the framework of the producer-related input control, three serious problems occurred, i.e. foreign materials and the required grain sizes, the bulk density and the chlorine content (TS). The paper reports on the mentioned problem areas and presents approaches for their solution.

Synergy Effects of the Co-combustion of Biomass and Sewage Sludge with Coal in the CFB Combustor of Stadtwerke Duisburg AG

Reiner Wischnewski, Joachim Werther, Norbert Heidenhof

In the framework of an EU-funded research project, co-combustion tests of biomass and waste in the coal-fired circulating fluidised bed (CFB) combustor of Stadtwerke Duisburg AG were performed. The aim of the study was to investigate whether positive synergy effects with respect to the overall emissions of the plant and its operating behaviour could be detected. Local measurements of gas and solids concentrations as well as fluid dynamic parameters were performed in the combustion chamber in addition to the measurements with the measurement devices of the plant. (EN)

State-of-the-art Turbine Technology Enabling Extremely High Steam Temperatures in Unit R of the Boxberg Power Plant – Significantly Contributing to a Reduction of CO₂ Emissions

Alexander Tremmel, H. Mandel, U. Klauke, C. Brandt

This paper will describe the steam turbo-generator set designed for the Boxberg Power Plant, Unit R. Consistent measures of improvement have been taken, based on field-proven technology. For instance, the use of state-of-the-art materials, developed by European research groups, allows the plant to be run with extremely high steam parameters. In addition, the flow configuration in the turbine is optimised in all areas. This includes the use of advanced aerodynamic profiles for the blading and an optimised design for the low-pressure last stages, combined with a downstream diffuser.

Operating Experience with Measures for the Improvement of the Cyclone Removal Efficiency

Bernd Krohmer, Bernhard Röper, Joachim Seeber, Georg-N. Stamatelopoulos

As the fuel ash is too fine to serve as bed inventory, quartz sand is added as bed material. For cyclones with non-optimum removal efficiency a loss of bed material particularly occurs at higher boiler loads, which must be compensated by the addition of quartz sand. The addition of quartz sand represents a cost factor and has also a negative effect on the wear of the furnace heating surfaces as well as the ash conveyors. By modifying of the cyclone inlet ducts of the plants Wachtberg K1 and Goldenberg K, which had been previously investigated by means of computer simulation, the consumption of quartz sand could be reduced to about 50 % of the original value. (EN)

Formation and Spreading of Ignitable Hydrogen-air Mixtures due to Postulated Leakage in the Generator Area

Tilman Diesselhorst, Peter Schönfeld, Klaus-Friedrich Freudenstein

The formation of ignitable hydrogen-air mixtures in the turbine building is considered resulting from postulated leakage at the hydrogen system for turbo-generator cooling, in order to specify the safety requirements. Concerning the global accumulation of ignitable mixtures in the turbine building the effect of ventilation is discussed and it is justified why an enrichment and layer formation of hydrogen under roofing structures cannot occur.

IT Reguirements for Integrated Planning and Documentation of Power Station Projects

Marcus Schönwälder

Power station projects typically include the combination of multidisciplinary trades and work packages with differing methodologies for the planning, design and operation phases. These work packages are usually undertaken by several different persons, each with a different methodology, all usually working independently from each other. The alignment of data between the work packages and the integration of results into a master plan is one of the largest challenges facing power plant operators during the project.

Performance Monitoring of Control Loops as Important Contribution Towards Efficiency Increases in Power Plants

Udo Enste

Studies showed that approximately 20% to 30% of all control loops are designed or tuned insufficiently. Here exists a big potential for upgrading the current revenue of power plants. With the help of a controller performance monitoring and loop tuning facilities during the whole life cycle of a power plant, the performance of the controlled loops can be increased up to 30%.