Abstracts - VGB PowerTech Journal 7/2013

Flexibility requirements for fossil-fired power plants to support the growth of the share of renewable energies

Imo Pfaff, Mathias Fruth and Lars Wiese

The planned increase of renewable generation in Germany to more than 100,000 MW of installed capacity within the next decade will result in significant changes to the existing electrical energy system. Fossil-fired power plants will remain inevitable to guarantee supply security. The maximum, securely available power plant capacity probably has to correspond to current level. This power plant park has to meet more stringent requirements in order to support the further extension of renewables-based generation. However, economic incentives, like e.g. necessary reward of flexible operation, are being missing.

Structural health monitoring and lifecycle management for civil engineering constructions in power plants and industrial facilities

Dieter Lehnen, Martin Demmer and Tobias Pfister

In contrast to other fields of engineering, structural health monitoring and lifecycle management for civil engineering constructions in power plants and industrial facilities have to be developed yet. The necessity of this development immediately arises from the building regulations law with its extensive set of regulations as well as from economic constraints. Approaches and methods of structural health monitoring and lifecycle management for civil engineering constructions in power plants and industrial facilities could be improved intensively during recent years. The paper focuses on practical examples that show the necessity of comprehensive and strategic structural health monitoring in conjunction with lifecycle management for civil engineering constructions in power plants and industrial facilities unambiguously und clear.

Efficiency increase and reduction of generation cost at hard-coal fired power plants Post-combustion of combustion residues from co-firing of RDF and biomass during ash removal

Günter Baur and Olaf Spindeldreher

Secondary as well as substitute fuels are being used in hard coal-fired power plants to improve efficiency and to enlarge fuel flexibility. However, grinding and firing systems of the existing coal-fired plants are not designed for those co-fuels. Any deterioration of the combustion performance would reduce the power output and increase ash disposal costs by increased content of combustion residues. The application of air-cooled ash removal, with simultaneous and controlled post-combustion of unburned residues on the conveyor belt, enlarges the furnace and maintains combustion efficiency even with different fuel qualities. Plant efficiency can also be increased through heat recovery.

Successful implementation of ageing management exemplified at the cooling tower of the Emsland nuclear power plant

Alexander Fischer and Carsten Düweling

The paper describes the successful implementation of the restoration of water distribution channels at the cooling tower of the Emsland nuclear power plant under the aspect of ageing management. The main challenge of ageing management is the determination of potential ageing mechanism and to avoid systematically and effectively their damaging influences. In the course of the annual site inspections, abnormalities at the lower side of the water-distribution channels of the cooling tower were detected, analysed, and repaired. The procedures conserve the load bearing reinforcement only for a certain period. Therefore permanent structural monitoring is needed.

9 %-chromium steel P91 and P92 in German power plants - from 1991 to the present day

Mirko Bader, Jörg Rainer Thümer and Klaus Glasenapp

P91 and P92 are the top players in the field of high-pressure piping in modern coal-fired and CCGT power plants. A long-term testing phase and a step-by-step introductory phase since the nineties had preceded current application. For this reason, a review and overview of the first installation in German power plants and the experience acquired from almost 20 years’ operating time of USC boilers in medium-load operation mode will be presented. With a view to the newly built power plants, the focal point changes to P92 for high-temperature pressure tubing. In this context the technical experiences were used in the material qualification process and the design of new component.

Noise emissions of cooling towers

Dirk Hinkelmann

Cooling towers are often large structures with high sound emission. The impact of water drops on the water surface in the collecting basin leads to the generation of middle- and high-frequency noise that is emitted via the air intake opening and the outlet. In forced-draft cooling towers, additional noise is generated by drives and fans. The sound emissions can be predicted by means of empirical calculation models. In this way, noise control measures can be taken into account already at an early phase of planning. Different, proven measures for reduction of sound emissions are taken depending on cooling tower design. Regulations on noise acceptance testing for cooling towers are given in various standards.

A new method to predict and evaluate fuel consumption as function of load and operation mode for the Avedøre 2 plant

Carsten E. Hendriksen, Steffen Hørlyck, Dennis Fisker, Niels Houbak, Søren H. Olsen, Erik Nylén, Rinette Drewsen and Karin Andersson

The multi-fuel CHP plant Avedøre 2 (AVV 2) located south of Copenhagen is the latest and most complex CHP plant in the DONG Energy fleet. The plant delivers close to 600 MW electricity and 600 MJ/s district heating for the Copenhagen district heating system. Fuel consumption can be predicted with a bi-linear approximation within an error of less than 1% over the operating and load range.

Boiler feedwater quality improvement by replacing conventional pre-treatment with advanced membrane systems

Bernhard Doll and Ramraj Venkatadri

Two case studies in different application fields highlight significant economical and operational improvements that were achieved by replacing conventional water treatment technologies by highly-sophisticated membrane systems. The first case study deals with boiler feedwater in a power plant, focusing on the challenges faced as well as the direct and indirect benefits gained by the new system within a utility station. The second case study deals with the conventional water treatment scheme for groundwater from 13 wells at a major oil sands facility. Operational performance as well as the cost improvements gained in both cases will be presented.

Basics of ammonia slip measurement at the flue gas exit of boilers

Sascha Krüger, Jörg Krüger and Friedrich Karau

When using SNCR in WtE-, biomass- and RDF combustion plants, it is not only the reduction rate of nitrogen oxide in the flue gas which is important to control but also the adherence to the limiting values for ammonia slip. Ammonia concentration in the flue gas upstream of stack is of course always in the operators´ focus as limiting values have to be hold. Measuring ammonia in the flue gas downstream of boiler is not trivial due to behaviour of ammonia which occurs in bonded state (compounds) in significant amounts also at flue gas temperatures above 400 °C. Ammonia compounds can occur on one hand as chemical compounds e.g. to chlorine as ammonium chlorine (chemical bonding) and on the other hand they can occur bonded to surfaces (physically adsorbed). Basic additives of the dry and quasi dry flue gas treatment cause the fractional release of bounded ammonia, therefore, after flue gas treatment, the ammonia slip can be partially measured.

Long-term operational experiences in the preparation of river Elbe water to boiler feedwater with membrane processes at AURUBIS AG

Jürgen Müller, Jürgen Batram and Ronny Portner

In Hamburg/Germany, the Aurubis AG (formerly Norddeutsche Affinerie) operates an industrial power plant to generate electricity and steam. For the past ten years, the annual demand of boiler feedwater (350,000 m3) has been obtained with an economical water treatment plant based on membrane processes directly from the river Elbe. The water treatment plant called NAqua built uses roughly pre-filtered river water. The produced water quality corresponds to the requirements of the current VGB-Standard 450 “Feedwater, Boiler Water and Steam Quality for Power Plants/Industrial Plants”. Since August 2002, the water treatment plant has been successfully in operation, and based on the described technique it belongs to the least recently operating plants in Germany.

Simulation and design of multi-stage demineralisation processes by using reverse osmosis and ion exchange

Jens Lipnizki, Björn Dinges and Heinz Schaberger

Simulation and design of both reverse osmosis (RO) and ion exchange (IEX) processes for water demineralisation are supported by the user-friendly, integrated software LewaPlusTM. This new software offers the option to design complex water treatment solutions, and provides the possibility to directly compare the results of RO and IEX calculations. It is possible to calculate with a given water analysis the results of RO treatment, and of subsequent treatment of this water with RO or IEX, respectively. The effect of variables such as temperature, silica, and carbonate concentration in the feed on process design and final water quality can be calculated for a whole system. The paper gives an overview of the capabilities of the software package and presents several application examples.

Influence of chemical composition and physical structure on the radiant emittance characteristics of ash deposits

Fabian Greffrath, Siegmar Wirtz, Viktor Scherer and Markus Neuroth

Ash residues accruing upon the combustion of solid fuels form deposits on heat exchanger surfaces which hinder heat transfer to the working fluid (steam). The thermal conductivity and - especially within the combustion chamber - the optical properties of the deposits determine the transferred amount of heat. In the course of an AiF research project the spectral normal emittances of mineral samples as well as their dependence on both the chemical composition and physical structure were investigated experimentally. Measurements with real coal ashes complete the experimental programme.