Abstracts - VGB PowerTech Journal 6/2005

NAPS in Europe – A New Factor in the European Power Market

O. Wilson

National Allocation Plans (NAPs) are the primary mechanism giving effect to the European Union’s “cap and trade” scheme for CO2 emissions established under the emissions trading Directive. These plans effectively set the conditions for the supply and demand for CO2 allowances in the trading period 2005 to 07 and, consequently, the allowance price. Member states need to ensure that national registries are established, accreditation systems are in place for verifiers and the accounting and taxation treatment of allowances are defined. Utilities must put in place emission monitoring and reporting systems, appropriate trading systems and management controls and define their compliance strategy.

How Much CO₂ Can be Stored in Deep Saline Aquifers in Germany?

F. May, Christian Müller and Chr. Bernstone

Saline aquifers are likely to contribute most to the national CO₂ storage potential. Different approaches have been used for capacity estimates at various scales. In order to evaluate the aquifer storage option in relation to national climate protection goals, it is necessary to know the total national storage capacity. Regional studies have covered barely half of the area of sedimentary basins in Germany. Extrapolations of the gross national storage capacity based on different regional studies are within the same order of magnitude (10 to 40 Gt CO₂).

Pressurised Pulverised Coal Combustion: Current Progress of this Coal-based CC-process towards Gas Turbine Needs and State of the Project

M. E. C. Förster, F. Neumann, R. Telöken and D. Pavon

The PPCC technology, a coal-fired combined cycle based on combustion of coal under pressure with a subsequent efficient ash and alkali separating rate over the temperature of GT entrance, can be considered the most suitable and straightforward method to employ hard coal in the combined gas-steam turbine process with an efficiency of approximately 55 %. A test plant with an output of 1 MW (thermal) is being operated within the scope of a research project funded by the Federal Ministry of Economics and Labour (BMWA) and carried out by E.ON Kraftwerke GmbH, Saar Energie AG, and Steag AG. A report is given on the current state of flue gas cleaning, the current quality of the cleaned flue gases and the plans for a 10 MW (thermal) pilot plant to be erected.

Thermodynamical Potential of Alkali Metal- and Heavy Metal Particles in Combined Processes with Pressurised Pulverised Coal Firing

B. Meyer and T. Bause

Coal-based combined gas and steam cycles allow the use of coal for power generation at high efficiency. One of these currently observed options is the combined cycle with pressurised pulverised coal combustion (PPCC). Coal-based combined gas and steam cycles allow the use of coal for power generation at high efficiency. One of these currently observed options is the combined cycle with pressurised pulverised coal combustion (PPCC). Thermo-chemical model calculation were performed that describe the potential of an alkali and heavy metal removal over getter materials and that show the risk of sulphate induced high-temperature corrosion.

High-temperature Corrosion in Biomass-fired Boilers

U. Hohmann and G. Mohr

Recent trends have led to attempts to utilise biogenic wastes for energy purposes on small boiler units. In German installations, it is wood waste of the classes AI to AIV that is mainly combusted. Experience has shown that both superheater and evaporator tubes are subject to severe corrosive attack with these fuels. The investigations carried out show that both chlorine and sulphur participate in the corrosion reactions.

In-situ Fireside Corrosion Testing of Superheater Materials with Coal, Wood and Straw Fuels for Conventional and Advanced Steam Temperatures

Pamela. J. Henderson, C. Davis, M. Montgomery and A. Karlsson

An increase in the steam temperature of a power station increases the electrical efficiency of the turbine. This in turn leads to a reduction in the cost of electricity and in environmental emissions produced per unit of electricity generated. However, higher steam temperatures give rise to more aggressive corrosive environments and the choice of material becomes more important. In addition, the aggressiveness of the fuels also depends on their chemical compositions. As part of a European research programme (COST 522) fireside corrosion tests of superheater and waterwall materials have been performed in-situ in industrial boilers or combustion test facilities, simulating conventional and higher steam temperatures.

Damage, Rehabilitation and Residual Life-Duration of Natural Draft Cooling Towers

R. Harte, W. B. Krätzig, U. Montag and Y. S. Petryna

After more than 30 years of service, many German cooling towers demonstrate severe aging effects. The paper explains and illustrates typical aging processes of towers shells, as there are: Corrosion with losses of concrete on inner shell faces; carbonisation of concrete with reinforcement corrosion, visible mainly on outer faces; damage of concrete due to cleaned flue gas injection; corrosion of resin coatings on inner shell faces; and finally hygro-mechanical swelling at inner surfaces leading to outside cracking. Numerical modelling of such damage phenomena admits computer simulations of tower responses under temperatures and gales, including such deterioration effects.

Environmentally-friendly Process for Reducing Harmful Organisms in Cooling Water

R. Schneider and L. Sprenger

Biological growth in both open and closed cooling circuits leads to corrosion damage, reduced heat transfer and lower efficiency in heat exchangers. Therefore, the tubes have to be cleaned manually at regular intervals. The most important harmful organisms are algae, slime-forming bacteria, and mussels. Degussa has developed a process that prevents these organisms from development. After the cooling water has been successfully treated, it decomposes into water, oxygen, and minor residual contents consisting of organic components, which are easily biologically degradable into CO2.

Planning – Construction – Operation of a Biological Waste Water Treatment for a Desulphurisation Plant

Ulrike Stein and K.-G. Grünewald

An economical and ecological outdated sewage water treatment system for the effluent of a desulphurisation system was disused within 18 months in co-operation with the appropriate authority. Instead a modern biological waste water treatment plant was built and started-up. The considerations and conditions, procedure principle and its realisation are described as well as relevant results and measuring data are represented.

Process Development for Mercury Reduction in FGD Waste Water Sludge before Co-incineration in Power Plants

H.J. Dieckmann and J. Tembrink

The process described aims at the installation of an additional cleaning step in the FGD waste water treatment, which enables the pre-separation of mercury compounds prior to the proper heavy metal precipitation. For this, a precipitant (e.g. Na2S, TMT) is added to the FGD waste water and the emerging particulates are flocculated by an added aid (e.g. Praestol). This procedure provides the plant operator with a significant lowering of waste disposal costs for the FGD sludge and results in an obvious reduction of mercury emissions to the environment

Ageing and Diagnostics of Power Transformers at Service Temperatures - Effect of Oil, Air and Moisture

I. Höhlein and A. J. Kachler

Aging research and diagnostics are essential elements of transformer life management to reduce the total life cycle cost and to enable successful "Condition Assessment".
The here presented results were obtained at 85 °C (within the range of normal service temperatures) and show a pronounced difference in aging performance between "open breather type" and "closed system type" transformers.
The paper discusses the main thermal aging processes:
Pyrolysis (> 150 °C), and Oxidative Hydrolysis (< 150 °C). The most important aging factors and the best ageing analytic diagnostics are presented.

Gas Analytical Transformer Diagnostics - The Way from Laboratory Analysis to On-line Monitoring

E. Bräsel and U. Sasum

The well-accepted laboratory analyses of the gases dissolved in oil have diagnostic limitations, which cannot only be overcome by equipment development to on-line monitoring (real time). Instead, the interrelations of the gas household of oil transformers must be considered for the gas-analytical task. On result is the real-state gas monitoring which describes the original fault gas comprehensively. On this basis it is possible to use the advantages of the interdependencies of electro-technical fault causes to achieve a high degree of diagnostic reliability. The calibratable Transformer Gas Monitor (TGM) allows practical measurements.