Browsing by Author "de Waal, Henk"

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    Fouling of heat exchanger surfaces by dust particles from flue gases of glass furnaces
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1989) Mutsaers, Peter L. M.; Beerkens, Ruud G. C.; de Waal, Henk
    Fouling by dust particles generally leads to a reduction of the heat transfer and causes corrosion of secondary heat exchangers. A deposition model, including thermodynamic equilibrium calculations, has been derived and applied to describe the deposition (i.e. fouling) process and the nature of the deposition products in a secondary heat exchanger. The deposition model has been verified by means of laboratory experiments, for the case of flue gases from soda-lime glass furnaces. Corrosion of iron-containing metallic materials, caused by the deposition products, has been briefly investigated with the same equipment. There is a close similarity between the experimental results and model calculations. The largest deposition rates from flue gases on cylindrical tubes in cross-flow configuration, are predicted and measured at the upstream stagnation point. The lowest deposition rates are determined at downstream stagnation point locations. At tube surface temperatures of approximately 520 to 550 K, the fouling rate on the tube reaches a maximum. In this temperature region NaHSO4 is the most important deposition product. This component is mainly formed at temperatures from 470 up to 540 K. The compound Na3H(SO4)2 seems to be stable up to 570 K, for even higher temperatures Na2SO4 has been found. These deposition products react with iron, SO3, oxygen and water vapour forming the complex corrosion product Na3Fe(SO4)3. NaHSO4, which is formed at tube surface temperatures below 540 K, causes more severe corrosion of iron-containing materials than Na2SO4. Maintaining temperatures of the heat exchanger surfaces above 550 to 600 Κ reduces the fouling tendency and corrosion in case of flue gases from oil-fired soda-lime glass furnaces.
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    Simulation of the condensation and deposition processes in regenerators of glass furnaces
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1988) Beerkens, Ruud C. G.; de Waal, Henk
    The fouling of regenerators of glass melting furnaces by deposition of flue gas condensates has been studied experimentally with simulated exhaust gases flowing through a cylindrical stack gas tube. The deposition of sodium sulphate and sodium metaborate has been investigated for various furnace conditions. A theoretical model based on thermodynamics and boundary layer transport theories has been developed and applied to determine the nature and deposition rates of the condensates. It has been validated with experiments as well as with practical situations. This model includes the calculation of the composition of the formed dust and of the gaseous phase. The influence of flue gas velocity, temperature distribution and flue gas composition on the fouling of regenerators has been illustrated for soda-lime glass furnaces and sodium borosilicate furnaces. It is shown that sodium sulphate deposition mainly takes place in the sub-top and middle sections of the regenerators. The deposition of sodium sulphate in soda-lime glass furnaces appears to be nearly proportional to the sodium concentration in the flue gas. The chloride and sulphur concentrations influence the deposition behaviour in the sub-top sections, the concentrations of oxygen, water vapor or carbon dioxide hardly influence the fouling in regenerators. In sodium borosilicate furnaces, sodium metaborate and sodium tetraborate formation takes place in the middle sections of the regenerator, sodium sulphate will deposit in the higher sections.