Browsing by Author "Beerkens, Ruud G. C."
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- ItemAmber chromophore formation in sulphur- and iron-containing soda-lime-silica glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2003) Beerkens, Ruud G. C.During cooling of reduced soda-lime-silica glass melts, doped with iron oxides and sulphur species, ferrous iron (Fe2+) reacts with sulphite (SO3 2-), and the Fe3+ (ferric iron) and also the S2- (sulphide) concentration will increase. The sulphite concentration in the amber glass melt after fining is sufficient to produce ferric iron and sulphide, required for amber chromophore formation during the cooling process. The product of the concentrations of Fe3+ and sulphide will strongly increase during coohng below about 1000 K. This mechanism implies that a necessary condition for amber formation is the availability of sufficiently large iron concentrations in the presence of a sufficient sulphite content in the high-temperature glass melt. The formation of a chromophore, based on Fe3+ - S2- - 3O2- - nNa+ complexes in the silicate glass will lead to amber colouring. A strong dependency of the amber intensity of the glass on the maximum temperature of melting, the alkali concentration of the glass, the total iron concentration and on the oxidation-state of the melt has been found experimentally. The charge of the networkmodifying alkali ions stabilizes the ferric iron-sulphide-oxide-alkali chromophores. In strongly reduced melts, hardly any sulphite can be formed and during cooling, the amber chromophore formation is limited. Experiments show a decrease in ferric iron concentrations and in the amber intensity when over-reducing glasses. A decrease in the amber intensity of amber glasses with increasing water content is probably caused by lower sulphite retention after fining of waterrich melts.
- ItemComparative study on energy-saving technologies for glass furnaces(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Beerkens, Ruud G. C.; Muysenberg, Hendrikus P. H.Different new technologies for increasing the energy efficiency of glass furnaces have been compared. The most important technologies are: - batch and cullet preheating, using a fluidized bed for batch preheating and dust filtration; - thermochemical recuperators using a water/methane reformer; - oxygen burners; - advanced air preheat systems like ceramic recuperators; - twin-bed burners; - new combustion technologies. The energy savings of these different measures for an industrial glass furnace have been calculated by using an energy-balance model. A soda-lime glass furnace with a production rate of 250 t glass/d has been chosen as an example for making these comparisons. The economics of all these different technologies have not been compared here. Melting of batches with up to 100 % cullet may have additional advantages for the energy consumption because of the possible lower melting temperatures needed to remelt pure cullet without other raw materials. Batch and cullet preheaters are the most important systems for the near future. Besides the improvement of the energy efficiency, the impact of some of the mentioned energy-saving technologies on the reduction of the emissions of air pollutants like dust, nitrogen oxides, sulfur oxides, chlorides and fluorides seems to be promising.
- ItemFouling 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, HenkFouling 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.
- ItemGlass industry in the Netherlands(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Beerkens, Ruud G. C.; Sturm, Mart[no abstract available]
- ItemImpact of furnace atmosphere and organic contamination of recycled cullet on redox State and fining of glass melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Beerkens, Ruud G. C.; Zaman, Laurens; Laimböck, Paul; Kobayashi, ShoThe onset temperature of fming and the quantity of fming gases is not only determined by the amount of fming agents in sodalime- silica batches, but also by the level of organic contaminants in the cullet or normal batch and the water vapor pressure in the furnace atmosphere. These conditions will also determine the redox State of the glass and residual sulfate or sulfide concentrations in the glass. Organic contaminants will form char during headng of the batch. This char partly reacts with CO₂ Coming from the decomposition of the soda, limestone or dolomite forming carbon monoxide. Stable types of char or cokes or cuUet-rich batches with only small amounts of carbonates will result in some carbon residues after the CO₂ evolution. This carbon partly reduces Sulfates and ferric iron in the fresh melts. This results in sulfide and ferrous iron formation in these glass melts. At increasing temperatures in the melt, the sulfides and Sulfates react together forming sulfur-containing gases between 1000 to 1250°C. The Sulfate retention decreases, finally the glass even may contain sulfur only in the sulfide form under very reduced conditions. In batches without reducing agents, Sulfates in the melt Start to decompose at temperatures exceeding 1400 °C. Small amounts of carbon and water vapor reduce the fining onset temperature. Water vapor from the furnace atmosphere predominantly Infiltrates the batch blanket during melting and foaming. The water will enhance the bubble and seed growth during fining. Water in the melt will influence the redox State of the final glass. Only in batches containing coarse raw materials or cullet, reducing or oxidizing gases from the furnace atmosphere Infiltrate the batch blanket and these gases will respectively reduce and oxidize components like iron oxides, sulfate/sulfide or chromium oxides in the batch blanket interior.
- ItemModeling of the aging of glass furnace regenerators(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Beerkens, Ruud G. C.; Muysenberg, Hendrikus P. H.; Barklage-Hilgefort, HansjürgenA model has been developed to predict the decrease of the thermal performance of glass furnace regenerators due to fouling by flue gas condensates. The model consists of four parts: a) description of the thermal performance (heat transfer) of regenerator checkers; b) description of the heat transfer in the furnace combustion chamber; c) determination of volatilization of sulfur, chloride and sodium components from the melt; d) modeling of chemical reactions in and deposition from flue gases in the regenerator. The aging and the reduction of the thermal efficiency due to fouling has been predicted: - for different checkerwork constructions or refractory types; - as a function of pull rate; - as a function of glass melt temperatures; - as a function of applied cullet fraction. Depending on the different conditions, the predicted increase in energy consumption is about 1 up to more than 3 %/year, mainly due to fouling. Cruciform and chimney block checkers seem to be less sensitive for this fouhng than basketweave packings. As molten glass temperatures increase, dust emissions and fouling rates are going up. According to the model calculations, a higher cullet fraction in the batch will lead to reduced aging rates of the regenerators. The model is in quite good agreement with practical observations in industrial furnaces.
- ItemModelling of sand grain dissolution in industrial glass melting tanks(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Beerkens, Ruud G. C.; Muijsenberg, Hendricus P. H.; van der Heijden, TomA combinadon of two models, deseribing dissoludon of sand grains in bateh blankets or in the molten glass, is presented: a microscale and a macroscale model. The macroscale model is based on a 3-dimensional calculation procedure to determine the temperature distributions and the flows in industrial glass melting tanks. By means of microscale models, using mass transfer relations for diffusional transport, the dissolution rate of single sand grains can be calculated. The dissolution of the sand is determined by following a large number of single grains during their trajectories through the batch blanket and the molten glass in the glass melting tanks. The dissolution rate of a sand grain is calculated for the temperatures and flow conditions i n every volume element in the tank through which the grain proceeds. The dissolution rate in the batch blanket depends strongly on temperature and the stage of the dissolution process. Initially the very fast shrinkage rate of the grains as temperatures exceed 1200°C results within 10 min in the dissolution of more than 50 % of the sand in the blanket. Forced and free convection in the glass melt leads to increases in the dissolution rate, up to a factor 5 compared to motion-free conditions. Forced bubbling for instance results locally in extremely high mass transfer rates and often improves the melting performance of industrial glass furnaces.
- ItemThe role of gases in glass melting processes(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Beerkens, Ruud G. C.The formation of gases and vapors during glass melting and the interaction between furnace atmospheres and industrial glass melts have an important impact on the emissions of glass furnaces, the glass properties and the quality of the glass products. Degassing or fining of glass melts is necessary to obtain a glass without gaseous inclusions. A simulation model has been developed which describes the behavior of gas bubbles in glass melts, depending on the process conditions. This model can be used to optimize the fining process in industrial furnaces. Foam formation on top of glass melts blocks the radiation from the combustion chamber of glass furnaces into the melt. Laboratory tests are used to find practical ways to reduce foaming during melting of sulfate-containing glasses. These tests show the importance of the furnace atmosphere on foam behavior in glass meldng tanks. Volatilization is the major source of particulate emissions in most glass furnaces. Volatilization rates from glass melts can be reduced by lowering the hot-spot temperatures and local gas velocities directly above the melt. One of the most important issues for glass makers today is the NOₓ formation of fossil fuel-fired furnaces. Results from West European glass producers show the possibility to decrease the formation levels of NOₓ by delayed mixing of the fuel and the oxidant and by intelHgent combustion control. Increased levels of water vapor in the glass furnace atmosphere will give higher water concentrations in the glass melt. In water rich glass melts, the sulfate retention will be often much less than in glasses molten in dry atmospheres. The water vapor effects the viscosity, radiative properties and the redox state of the melt. Because of these effects, the color of glasses molten in oxy-fuelfired furnaces, with high water vapor concentrations, may be different from glass molten in air-fired furnaces, using the same batch composition.
- ItemThermal behaviour of glass batch on batch heating(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Faber, Anne J.; Beerkens, Ruud G. C.; Waal, Henk deThe heating process of a barium-strontium glass batch has been studied in a 401 pot furnace, using a multiple thermocouple assembly. The effect of several batch batch parameters on the heating process has been measured, including layer thickness, cullet fraction, water content and pellets. The results have been evaluated using a heat penetration batch model. In the model two heating stages, below and above a certain batch transition temperature ϑs, typically 800 to 900 °C, are distinguished. Values for the temperature-dependent thermal diffusivity of the batch have been derived from experimental temperature distributions in the batch during heating. Below the thermal diffusivity has an almost constant value of 0.4 · 10^-6 m2/s for a standard (powder) batch blanket; for ϑ > ϑs the net thermal diffusivity strongly increases with temperature, due to the formation of primary melt phases. For ϑs < ϑ < 1100 °C the average value is about 1.4 · 10^-6 m2/s. A 100 % cullet layer has a 50 % higher thermal diffusivity for ϑ < ϑs; pelletizing the batch is of little influence on the virtual thermal diffusivity and (extra) wetting has a retarding effect on batch heating due to extra heat absorption. As for the furnace temperatures it appears that increasing the temperature of the glass melt is more effective for improving the batch heating rate than increasing the temperature of the combustion chamber. Practical recommendations are given for batch preparation, charging and heating in industrial glass tanks.
- ItemUpgrading glass melting technology by model-based processing(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Beerkens, Ruud G. C.; Faber, Anne-Jans; Muysenberg, Erik; Simonis, Frank[no abstract available]