Abstracts - VGB PowerTech Journal 7/2017

Editorial: Flexible coal fired power plants – Experiences from Germany appreciated in China

Dr.-Ing. Claudia Weise

With some 1.4 billion people, China is the most populous country and with a rapidly growing economy China is now also the world’s largest energy consumer and producer. China’s influence on global energy markets is also growing. [more...]

Improving operating behaviour of wind turbine generators via rotor blade condition monitoring

John Reimers and Daniel Brenner

Condition Monitoring has become more and more important to detect damages of wind turbines in their initial states to prevent both damage growth and component failure. Less focus, however, has been spent on the contributions that condition monitoring systems make to the operational behaviour of the turbine, although these contributions increase the energy yield and, at the same time, reduce life-time consumption. Yield increase is especially important to the operator as additional yield directly affects profitability of the project, where higher life-time consumption may be compensated by a full-service contract or the like. This article deals with the contributions of a rotor blade condition monitoring system to both operational behaviour and life-time consumption monitoring. The reason that rotor condition monitoring contributes more to this topic than for example a gearbox monitoring system is that rotor monitoring can detect operational deviations that are not related to the blades, but to the drivetrain and/or the control system.

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Use of VDI 3834-1 & DIN ISO 10816-21 for vibration monitoring of large wind turbine fleets

Thomas Gellermann, Ulrich Oertel and Holger Fritsch

The VDI 3834 standard “Measurement and Evaluation of the Mechanical Vibration of Wind Energy Turbines and Their Components” has been available as a code of practice for the vibration evaluation of wind turbines with gearboxes since 2009. This paper presents the essential content of the code of practice and its aim to standardise vibration measurement and evaluation. It also explains the difference to condition assessment. Based on the extensive pool of data, examples of turbines with abnormal vibration behaviour are presented. Recognisable faults are stated using the vibration characteristics and conversely the limits of detectability are also shown. These require the use of specific analysis methods as provided by condition monitoring systems.

512 MW in 10 minutes – New York City peaking plant solution applicable for Europe

Shawn Picard and Tobias Aschoff

In New York City, fluctuating weather has a high impact on power usage. The daily spread can be as high as 3,500 MW – particularly during the summer months. In fact, a three to four degree change in weather – for example as the result of a rain storm – can cause a significant surge or drop with the changing operation of air conditioning units in private households and office buildings. Peaking generation stations in and around the city that are capable of a quick ramp up or shut down help manage fluctuating power. One of the peaking generation stations is the 512 MW Bayonne Energy Center (BEC), which is powered by eight aero-derivative turbines. A special feature of the configuration is its high cycling capability with high ramp rates from non-spinning reserve and the ability to reach full power from cold start in less than ten minutes. Due to its multiple unit set-up, output can be scaled to the actual demand so that the turbines are operated as close as possible to their more efficient full output. Further advantages of the solution are low maintenance requirements, low emissions, and dual fuel capability.

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Energetically optimisation of the Offenbach waste fired power plant by a dry flue gas cleaning system and a new steam turbine

Günther Weiß, Dimitrios Fotakis, Mario Kuppinger, Tibor Füle, Helmut Peter and Markus Gegner

The Offenbach waste incineration plant increased its output of electricity and district heating about 30% by replacing the wet scrubber in the flue gas cleaning system by a dry sorption, installation of a new steam turbine and improvements of the operation. With a budget of nearly 25 Mio. Euro for the project the electrostatic precipitators were teared down and replaced by fabric type filters with flue gas cleaning by lime milk and natrium hydrogen carbonate. A new bigger steam turbine was installed. The operation of the plant was optimised by a 10 % increase of the maximum steam production, replacing steam for the operation of the feed water pumps by electric power and heat exchangers for heat recovery from the flue gas to the district heating system. It was an economically project by the increased energy output and waste input with an positive ecological effect by further reduction of the emissions.

CFBC nozzle floor: Damage analysis, simulations and maintenance

Joachim Plackmeyer, Adlan Omer and Polat Sentürk

Experiences, problems and solutions are set out in this report regarding the wear of primary air nozzles in circulating fluidised bed combustion. A defective material was identified as a cause for extreme wear and tear that caused great damage after only 1,500 operating hours. Additional causes of extreme above-average erosion are shown. Recommendations for the material selection will follow. Furthermore, a method for the detection of worn or clogged and partially clogged nozzles is presented. This method provides the operator with information on how and when nozzles are to be changed or maintained to ensure a uniform pressure loss at the nozzle bottom. Moreover, the results of a simulation will be presented. The result is that a concrete floor is not absolutely necessary. The erosion at the nozzles just shifts to other parts. Further findings and recommendations for the air nozzles are detailed.

Material location of ammonia in SNCR processes in flue gas and residual material channels at German waste incineration plants

Sabine Weineck, Stefan Vodegel and Torsten Reindorf

The amendments to the 17th Federal Immission Control Regulation (BImSchV) included a reduction of the emission limits for nitrogen oxides and the introduction of a limit for ammonia slip. The regulation poses a particular challenge to plants running SNCR technology. In the research project Material location of ammonia in SNCR processes in flue gas and residual material channels at German waste incineration plants, the VGB Research Foundation (Essen) funded investigations of possible effects of a further reduction of NOx limits. Measurements at six existing waste incineration plants and RDF power plants, with subsequent scientific evaluation of the results, additionally sought to investigate predictions for the possibility of further reductions in limit values. A good data base was established in order to provide answers to future questions relating to reductions in NOx and NH3 limits. Existing knowledge in relation to single plants has been placed on a broader foundation.

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Alkalise with lithium hydroxide – Examples from practice in CCGTs and industrial plants

Christiane Holl and Heiko Woizick

For optimum operation of drum and shell boilers alkaline boiler water conditions are necessary. The choice of solid alkalising agents to control the boiler water corrosion is limited by the design of the boiler and the water substances. As conventional, non-organic conditioning agent sodium hydroxide and trisodium phosphate are mainly used. The use of lithium hydroxide is a little known and unfortunately rarely used alternative. This method has several significant advantages, especially in harmful boiler constructions, for example in boiling surfaces with low tube gradient and / or other plant designs which are difficult to control regarding local flow conditions such as flow accelerated corrosion. CCGT – plants at RheinEnergie as well as some by Hydro – Engineering supported industrial power plants are operated successfully with this alkalising agent partial for many years.

Plasma ignition system for the Zetes power plant in Turkey and its advantages for the changed energy market

Zhang Ke, Liu Lin, Hans-Christian Schröder and Feng Guoqing

After 168 hours of trial operation, the 2 x 600 MW coal-fired units of the Zetes power plant in Turkey were put into commercial operation in 2016. Already during their construction, the units integrated the plasma ignition system, delivered by the China Yantai Longyuan Power Technology Co., Ltd (YTLY). The whole fuel oil system was cancelled, The power plant realised oil-free start-up during boiler commissioning, which helped to save abundant oil, prevent the environmental issues which might have emerged by non-application of ESP while burning oil at the ignition stage, and bring tremendous economic and environmental benefits for the power plant. The plasma ignition system replaces the oil-system in coal-fired power plants for realising oil-free power plant operation, which is regarded as the inevitable direction of coal-fired power industry development.

12,000 hours of operation with oxygen-carriers in industrially relevant scale

Fredrik Lind, Angelica Corcoran, Bengt-Åke Andersson and Henrik Thunman

Oxygen carrier aided combustion (OCAC) is a novel combustion method and a spin-off from chemical-looping combustion (CLC). The core of the technique lies in the utilisation of an oxygen carrier (OC) as bed material, and the purpose to enhance the distribution of oxygen in fluidised bed (FB) boilers. The concept combines the robustness of the well-established technology FB boilers with the novel features of oxygen active properties introduced by the OC. Due to several similarities, the OCAC concept can also contribute with knowledge in a transitional path for the scale-up of other chemical-looping techniques, such as CLC, from lab to industrial scale. First experiences are presented with a 75,000 kWth CFB-boiler which has been operated with ilmenite (FeTiO3) as bed material during 12,000 hours with municipal solid waste as fuel. The investigation shows that ilmenite can replace the commonly used bed material silica-sand without any retrofitting of boiler equipment, and that ilmenite enhances the mass transfer of oxygen inside the furnace.