Abstracts - VGB PowerTech Journal 10/2011

The potential future of high-temperature gas turbines in power plants

Konrad Vogeler

The future role of the high-temperature gas turbine is discussed. Due to environmental and cost pressure, the mix of primary energy sources will be changing. CO2 capture and storage (CCS) will have major impact on technical equipment and operation cost of fossil-fired power plants. If fuel consumption has to be minimised, the efficiency of power plants will be the key to success. The paper discusses the main parameters which influence efficiency and power output for an open and combined cycle gas turbine cycle. State-of-the-art materials and manufacturing methods promise potentials to increase efficiency even further.

Status and significance of national, European and international standards for the gas turbine plant system - GT standardisation quo vadis?

Gerd Weber and Burkhard Josuhn-Kadner

Many different committees are dealing with standardisation in the field of gas turbines. The paper lists these committees and the main work currently pending and outlines the diverse tasks of the standardisation committees to promote participation of operators, customers, authorities and manufacturers. Standardisation has many advantages in terms of cooperation among those involved in the turbine business and can result in considerable reduction of non-value adding work in the business.

The first test results of the new MAN 6 MW gas turbine

Markus Beukenberg, Alexander Wiedermann, Ulrich Orth, Emil Aschenbruck and Frank Reiß

The development of a completely new series of gas turbines requires significant capital, resources and know-how. MAN Diesel & Turbo strategically decided to create a gas turbine in the 6 MW class. The construction of the gas turbine has been on the basis of opportunities in current and future markets and the positioning of competition, this has determined the characteristics and technical parameters which have been optimised in the 6 MW design.

An innovative combustion technology for high-efficiency gas turbines

Sebastian Göke and Christian Oliver Paschereit

A new combustion process is being developed at the Chair of Fluid Dynamics of the Berlin Technical University. The new system is characterised by large amounts of water vapour added to the combustion process. This approach clearly decreases resulting emissions and increases efficiency of the “ultra-wet gas turbine” which is comparable with modern combined cycle power plants. Nearly any gaseous fuel can be combusted by the new process.

Development of reliable thermal barrier coatings for high-loaded turbine and combustor parts

Hans-Peter Bossmann, Gregoire Witz and Robert Baumann

Thermal Barrier Coatings (TBC), mainly consisting of 7 % Yttria stabilised Zirconia (7YSZ), have been used for decades in gas turbines. A variety of MCrAIY have been developed as bondcoat (BC), where M represents Ni, Co or a combination of both. Further elements have been added to improve BC behaviour. For application of BC/TBC, thermal spraying of fine metallic/ceramic powder is state of the art. TBC is applied by atmospheric plasma spraying (APS), BC either by vacuum or low pressure plasma spraying or APS.

Passive acoustic dampers for sound attenuation in modern gas turbine combustors

Sermed Sadig and Michel Houde

The demand on low emission gas turbines is pushing combustion systems more and more to the stability limits. As a result, self-excited combustor oscillations can be often observed in lean premixed combustors. The impact on the operation of the gas turbines is high. Operators need to perform regular inspections of hot component parts. If instabilities have caused a component failure, this component could further damage expensive turbine parts. In addition, engines in certain geographic areas need to be retuned seasonally, due to ambient temperature changes. Passive control features like acoustic dampers can be used to attenuate combustion instabilities and increase operating range and engine performance. This article provides a brief overview on the driving mechanism of instabilities and will describe passive damping technology developed by OEM and implemented in gas turbine combustors to reduce the level of oscillations.

Problems with circulating fluidised bed (CFB) boilers in China and their solution

Leming Cheng, Junchun Zhang, Zhongyang Luo and Kefa Cen

The currently installed capacity of CFB units is nearly 73 million KW, accounting for about 12.1 % of the total thermal power in China. CFB boilers have many advantages but during operation there are still many problems that affect safety and efficiency. The problems experienced with Chinese CFB boilers are summarised and appropriate solutions are discussed.

Experience with availability, maintenance and cost-effectiveness of three coal-fired CFB boilers in a combined heat and power plant after four years of RFD co-combustion

Dirk Roschek and Christoph Ipsen

Since 2006 refuse derived fuels (RDF) have been co-combusted with coal in three circulating fluidised bed (CFB) boilers of the public utility Stadtwerke Flensburg GmbH. The boiler technology has been modified for co-combustion. A compact station, an RDF storage building, three pneumatic conveying lines and an ash hopper with three chambers have been constructed. A report is given on the operating experience, among others related to problems with the new fuel and outages of the fuel feeding system as well as economic marginal conditions.

SRF co-combustion in the Wuppertal-Elberfeld fluidised bed power plant

Uwe Herrmann

Many operators of coal-fired power plants find an opportunity to improve economic conditions by co-combustion of solid recovered fuels (SRF), thereby substituting expensive primary energy sources, as well as improving the CO2 balance in emissions trading. Against this background, WSW Energie & Wasser AG decided in 2009 to combust high-calorific SRF at the Elberfeld CHP plant site, where two coal-fired CFB boilers were retrofitted with a co-combustion facility. First reports are given on the operating experience.

Conditioning monitoring of hot, thick-walled components in boilers with ultra-sound laminography as innovative testing procedure

Klaus Metzger, Falk Müller, Korbinian Puchner and Karl-Heinz Schmitt-Thomas

Within the course of inspection of high-temperature components, the assessment of the microstructure is of significant importance for safety and reliability. For non-destructive investigation, however, only the surface of the components is available. With the UT-laminography it is possible to classify structures on the basis of correlations between ultrasound velocity and microstructural influences especially increasing of inhomogeneity by creep stresses.

Use of synthetic titanium dioxide containing materials to improve the surface properties of furnace and boiler linings against deposits

Peter Kohnen, H.-J. Langhammer and D. Amirzadeh-Asl

Fluidised bed furnaces, that can use a broad fuel band, are susceptible to the formation of mineral deposits such as ash and slag on components, thus reducing the system’s performance and efficiency. These deposits have to be removed at regular intervals which also causes high costs. Refractory materials with additives containing titanium dioxide have been developed in order to eliminate formation of such deposits on the surfaces of refractory boiler linings. Two applications in fluidised bed boiler installations are described, as well as the refractory materials’ properties, along with their development and production process.

Intervex - A new process for desulphurisation of flue gases

Lars Tiberg and Mats Eriksson

A new process for flue gas desulphurisation of flue gases is presented. In a reactor, flue gases pass counter flow through a bed of granular limestone. Water is sprayed over the bed. The limestone is slowly circulated through the bed when the bed material is slowly moving downward in the reactor. Sulphur oxide from the flue gas forms calcium sulphite and sulphate in the spray water flow. A first plant for a 20 MW boiler has been operated during a long development period and now shows interesting properties and results: high degrees of reduction of sulphur, chlorides, fluorides and fly ash, the sorbent is cheap, the pressure drop is low, the yield of the limestone is 75 % and the investment cost is also low.

Measures to observe the current dust emission limit

Michael Evard

The paper describes the operational experience and optimisation approach for a hot electrostatic precipitator (ESP) with a flue gas temperature of approximately 350 °C as part of a circulating fluidised bed (CFB) boiler. It is particularly dealing with fault finding and cleaning after 20 years of operation. From the beginning of January 2011, new laws have come into force regulating dust emission limits. Therefore, it was necessary that existing ESP systems operate optimally. The ESP is a part of a hard coal-fired CFB boiler.