Abstracts - VGB PowerTech Journal 3/2014

Enhancing the market flexibility of Rhenish lignite-fired power plants

Armin Eichholz, Christian Fielenbach and Heinz-Gerd Blank

The market for conventional power plants has undergone fundamental changes within a few years: the power plants’ situation is characterised by high price volatility and significantly lower price levels for typical peak- and baseload power exchange products, resulting in a substantially altered load profile. RWE Power, operator of the Rhenish lignite-fired power plants, has adapted to this situation both technically and commercially. Among others a new IT tool known as “Process quality optimisation” has been introduced. This tool is the binding element of the various innovations implemented in the existing power stations. As a result, the flexibility of the existing power stations is almost as high as the flexibility of BoA units.

SGT-750: industrial reliability with aeroderivative performance

Hans Holmstroem

Gas will play an increasingly important role in the power generation mix over the next two decades. Due to their ability to typically reach full load within 10 minutes, many of today’s aeroderivative gas turbines are often used to provide this grid support function. Recognising a gap in its portfolio, Siemens decided to develop a gas turbine that is capable of meeting this need but is also robust enough for use in industry. In addition to having a multi-purpose turbine for the power generation sector, the aim was to design an engine that was also well suited to mechanical drive applications in the oil and gas sector. Known as the SGT-750, the gas turbine has been specifically designed for long operating hours with extended maintenance intervals to reduce downtime. The engine is designed to perform well in hot climates but is also prepared for operation in cold conditions, without the need to change any of the core gas turbine components.

Significant cost savings obtained using advanced membrane systems for cooling tower water treatment and in ZLD plants

Christoph Maurer, Bernhard Doll, Marvin Drake and Ramraj Venkatadri

Driven by the demand for continuous process improvements to increase plant efficiency and lower customer costs, power plants around the world are striving to upgrade conventional water treatment systems. One suitable option is membrane technology such as microfiltration. Case studies highlighting improvements in water quality and improved economics, especially in cooling tower blowdown water treatment and reuse will highlight the latest membrane technologies that can help power plants reduce costs, improve processes, and optimise water footprint.

Preservation of boilers and turbines with the surface-active substance octadecylamine

Ronny Wagner and Erwin Czempik

Based on the feed-in priority of electricity from renewable energy sources, conventional fossil power plants are faced with new challenges. Flexible load requirements associated with frequent shutdowns especially in plants with peak load are the result. For this reason, preservation procedures play an increasingly important role. Because of different methods, the operator has to make a decision to what extent and by which technology the system should be protected during downtime. However, not only costs play a role. The procedure should also provide a good protective effect with the most simple handling and flexible management system. In the paper, the wet chemical procedure of preservations using the surface active-substance octadecylamine (ODA) will be presented. Various techniques of preservation will be explained by practical examples.

SO₃/H₂SO₄ measurement in flue gases – Difficulties and solutions

Christine Koczab and Frans van Dijen

Attention is paid to the measurement of SO₃/H₂SO₄ in flue gases of coal-fired power plants. The quality of the manual methods is not well established yet, and many problems can be encountered. Attention is paid to the importance of measurements, problems, solutions, the state of the art of SO₃/H₂SO₄ measurements, flue gas sampling and the need for working on standards based on the CCM and salt method.

Mass balance of mercury in air pollution control devices while co-firing biomass at a lab-scale firing system

Tobias Schwämmle, Silvio Farr, Barna Heidel and Günter Scheffknecht

One very promising strategy to reduce mercury emissions of coal-fired power plants is the co-benefit approach by oxidation of elemental mercury in high-dust SCR-DENOX catalysts and removal of oxidised mercury in the wet flue gas desulphurisation (FGD). Co-firing of biomass and refuse derived fuels is an attractive nearterm measure for reducing CO₂ emissions forming a new challenge for existing air pollution control devices. The Institute of Combustion and Power Plant Technology of the University of Stuttgart (IFK) operates a lab-scale firing system for the investigation of on-going reactions in the flue gas path. There the influence of biomass co-combustion on CO₂ and Hg removal was determined as well as possible consequences for power plant operation.

Measurement of low mercury concentration in flue gases of combustion plants

Johannes Mayer, Sebastian Hopf, Frans van Dijen and Alessio Baldini

In the context of the implementation or tightening of mercury emission limits on a national (German) and European level the question may be raised how mercury emissions can be measured reliably at very low concentrations. In addition to the determination of the entire mercury content, the oxidation stage of the mercury in the flue gas is of specific importance to achieve further reduction of mercury emissions. Within the scope of a project, which has been funded by VGB, alternative manual and automatic measuring methods following the adsorption principle, as well as alternative continuous measuring methods have been compared with each other and with the standard reference method.

Control of microbiology in cooling water systems by means of ozone – Environmentally-friendly and efficient

Ingo Königs, Florian Axt and Harald Stapel

The control of microbiology is an essential part of the efficient and safe operation of open cooling water systems. One alternative to conventional biocides is ozone. It provides the highest oxidation potential of all biocides and is furthermore environmentally-friendly, as it produces no toxic decomposition products and by-products. Hence it can be applied continuously, which is different to most of the other biocides. The microorganisms have no time and chance to recover which also prevents the generation of biofilms. The article describes the problem of microbiological contamination in open cooling water systems and discusses conventional biocides as well as modern alternatives.

Alternative macro fouling control in power plants

Frank de Vos, Lars Venhuis and Marco Buccolini

Hypochlorite can be used against macro fouling in cooling water systems. However, its application is restricted due to the formation of toxic trihalomethanes (THM), such as chloroform. At a 630 MWe power plant tests have been performed by DNV GL, in consultation with Chimec, using a biocide on the basis of peracetic acid (CH 7562) instead of hypochlorite. On the brackish cooling water of the plant effective mitigation of the mussel Mytilopsis leucophaeata has been shown. The tests results also showed no significant increase in THMs.

Chlorine dioxide utilised as biocide in seawater applications

Matthias Weber, Michael Voges and Spiru Grima

One of the main tasks of a cooling water treatment programme is the avoidance of fouling in the cooling system. When used as a primary biocide, chlorine dioxide has proven to be highly effective against microbiology such as bacteria, algae and fungi, as well as macrobiological contamination in seawater applications. In the application introduced in this paper the common acid-chlorite process to generate chlorine dioxide has been altered by the use of sulphuric acid. The system has been evaluated in order to verify its fitness for similar once-through applications in power plants.

On-line pH measurement in low conductivity samples

David Gray and Kirk Buecher

pH control is essential to minimise corrosion, prevent various kinds of deposits and ensure efficient operation. In power plant applications, the low conductivity of the sample makes pH measurement more difficult than in most other industries and applications. A new probe to be used in power plant applications is being described. The new design includes a built-in measuring circuit, analogue-to-digital signal conversion, calibration memory and operating condition history. This approach is part of an instrument platform design that includes similar intelligent sensors for conductivity, dissolved oxygen and oxidation-reduction potential (ORP) as well as pH.