Vattenfall

About: Vattenfall is a company organization based out in Stockholm, Sweden. It is known for research contribution in the topics: Wind power & Combustion. The organization has 685 authors who have published 857 publications receiving 18912 citations. The organization is also known as: Vattenfall AB & Kungliga Vattenfallstyrelsen.

Modelling a Lignite Power Plant in Modelica to Evaluate the Effects of Dynamic Operation and Offering Grid Services

Abstract: O ering services to stabilize the electrical grid is nowadays one of the major tasks of fossil power plants and also of signi cant economical relevance. However the e ects on the power plants regarding the additional wear of components is uncertain. Usually the e ects regarding control reserves, especially primary control occur with high frequencies and small amplitudes, which makes investigations based on measurement data impossible since the e ects are masked by the noise of normal operation. In order to investigate this issue, a detailed model of a lignite power plant has been used, which was developed in Modelica for simulating and comparing scenarios with and without o ering primary control reserves. The model comprises the entire water-steam cycle including turbines, preheaters and pumps, as well as a very detailed boiler model including the air supply, coal mills, a combustion chamber, heating surfaces and piping. Furthermore the power plants control system has been implemented in a very precise way. In addition the study involves an investigation on the input signals (grid frequency) and a calculation of lifetime consumption for speci c components to evaluate the e ects.

Deposit chemistry and initial corrosion during biomass combustion – The influence of excess O2 and sulphate injection

Abstract: Corrosion of superheater tubes is a serious problem during combustion of fuels with a high content of chlorine, such as waste and certain biomasses. The alkali chlorides are released to the flue gas and may condense on the heat exchanger tubes forming corrosive, chloride-rich deposits. In this work the effect of ammonium sulphate ((NH4)(2)SO4) injection on gaseous alkali chlorides, deposit chemistry and initial corrosion attack of superheater tubes during biomass combustion have been investigated. The investigation was carried out at three different sulphate injection rates (reference, low and high) and at three air excess ratios (lambda = 1.1, 1.2 and 1.4). Short-term exposures of Sanicro 28 specimens, using temperature controlled probes, were used for deposit collection and to study the initial corrosion attack. The results showed reduced concentrations of potassium chloride in the flue gas when injecting ammonium sulphate and in particular in combination with high air excess ratios. A decrease of chlorine was also observed in the deposit, but the concentrations did not always correlate to the flue gas measurements. In particular, it was evident that a subsequent sulphation occurred on the tube surface at low air excess ratios. Metallography revealed that sulphation reactions on the tube surface, rather than in the flue gas, had a detrimental effect on the initial corrosion attack. As a consequence, the corrosion attack correlated more clearly to the KCl(g) concentration in the flue gas than the chlorine content in the deposit.

17 – The Analysis of Fractures, Stress and Water Flow for Rock Engineering Projects

Abstract: Publisher Summary This chapter presents an analysis of fractures, stress, and water flow for rock-engineering projects. Heavy water inflow to a rock opening is one of the most troublesome problems that can be encountered in a rock engineering project, both from an economic and technical point of view. Depending on the purpose of a rock installation, even minor leakage into an underground cavern or a tunnel can create serious economic and/or environmental disadvantages. In certain cases, predicted values of the hydraulic conductivities of the rock mass can be regarded as too high, and the target area has to be abandoned though other rock mass parameters are predicted as favorable. The degree of reliability of prediction of the hydraulic properties within a target area is, therefore, a key question in all works connected to rock installations. There is a more or less pronounced scale effect present when the hydraulic characteristics of the rock mass are to be estimated or determined. The most common methods used in the preinvestigation stage for a rock installation are naturally small-scale tests. There is a strong relationship between prevailing rock stresses and the hydraulic properties of the rock mass. This situation is specially pronounced in a fractured rock, where there are significant differences in the Young's modulus of the rock matrix and the fractures.

Impacts of acidic gas components on combustion of contaminated biomass fuels

Abstract: The formation of high concentrations of acid gases; in combustion with large variations in fuel qualities, represents a major challenge for energy production from contaminated biomass fuels. This p ...

Long-term hygrothermal performance of nuclear reactor concrete containments – Laboratory evaluations of measurement setup, in situ sampling, and moisture flux calculations

Abstract: A measurement setup for in situ sampling of internal relative humidity and temperature in concrete structures was developed. The setup was used to evaluate the moisture conditions and to determine whether drying of the concrete components within a nuclear reactor containment contributes to the moisture conditions. The measurement setup was tested for accuracy and thereafter installed in Swedish nuclear reactor containments for in situ monitoring. Results from the measurements confirmed that the setup is suitable, especially for long-term measurements at depths of 50 mm or more. Complementary moisture transport calculations showed that the moisture flux from the concrete to the interior of the reactor containment have a noticeable effect on the environmental conditions in the containments. The calculations of the moisture condition in the concrete show that 15–30% of the evaporable water in the concrete has been dried out during the 30 years of operation.