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New glass melting concepts

Utilization of melting space

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New relative value – space utilization (u) – was introduced. u = v.τH / V (v - volume flow, τH - geometric residence time, and V - the volume of the reactor), The (u) value quantitatively assesses the main melting processes, i.e. the particle dissolution and the bubble removal in a continuous melting space. The (u) value is obtained by mathematical modeling and incorporates the dead volume (unused for processes) of melting space. The current industrial furnaces have a value of less than 0.1 due to disadvantage type of flow. Modeling of various types of flows in model space shows that the value up to 0.8 can be reached by establishing a certain type spiral flow (proportional to increase performance and reduce heat losses). Favorable modeling results are transmitted to the real melting facilities and also serve on the draft designs of new melting spaces.

Behaviour of bubbles in centrifugal field

 šířka 215px The competition of two phenomena takes place in the centrifugal field: bubble dissolution and centrifugation. Skimming is a faster process on favorable terms. Mathematical and experimental modeling can find optimal process conditions. Optimum conditions can be applied to melt glass or other viscous liquids, provided similar behavior of bubbles. The figure shows the dependence between time of the bubble removal and rotational velocity.

Behaviour of bubbles under reduced pressure

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Experimental modeling in laboratory conditions showed that the reduction of the external pressure in the range of 20 - 40 kPa at temperatures around 1300°C brings roughly the same intensity of the bubble removal process as in conventional melting furnaces working under normal pressure and at maximal temperatures in the melt above 1500°C. Moreover, it is often possible to significantly reduce the concentration of environmentally problematic refining agents. The figure on the left presents the results of a parametric study showing the dependence of the space pull rate on temperature and pressure.

Bubble trajectories in low pressure melting space

 

  Selected papers

  • Jebavá M., Dyrčíková P., Němec L. (2015): Modelling of the controlled melt flow in a glass melting space — Its melting performance and heat losses. Journal of Non-Crystalline Solids 430: 52-63. doi:10.1016/j.jnoncrysol.2015.08.039
  • Hrbek L., Dyrčíková P., Němec L., Jebavá M. (2014). Industrial opportunities of controlled melt flow during glass melting, part 2: Potential applications. Ceramics-Silikáty, 58(3), 202-209. Open Access
  • Dyrčíková P., Hrbek L., Němec L. (2014). Industrial opportunities of controlled melt flow during glass melting, part 1: Melt flow evaluation. Ceramics-Silikáty, 58(2), 111-117.  Open Access
  • Němec L., Jebavá M., Dyrčíková P. (2013). Glass melting phenomena, their ordering, and melting space utilisation. Ceramics-Silikáty, 57(4), 275-284. Open Access
  • Jebavá M., Němec L. (2012). The fining performance under the effect of physico-chemical parameters. Ceramics-Silikáty, 56(3), 286-293. Open Access
  • Němec L., Cincibusová P. (2012). Sand dissolution and bubble removal in a model glass-melting channel with a uniform melt flow. Glass Technol.: Eur. J. Glass Sci. Technol. A, 53(6), 279-286. Ingentaconnect
  • Cincibusová P., Němec L. (2012). Sand dissolution and bubble removal in a model glass-melting channel with a melt circulation. Glass Technol.: Eur. J. Glass Sci. Technol. A, 53(4), 150-157. Ingentaconnect
  • Polák M., Němec L. (2012). Mathematical modelling of sand dissolution in a glass melting channel with controlled glass flow. Journal of Non-Crystalline Solids, 358(9), 1210-1216. doi:10.1016/j.jnoncrysol.2012.02.021
  •  Tonarová V., Němec L., Kloužek J. (2011). The optimal parameters of bubble centrifuging in glass melts. Journal of Non-Crystalline Solids, 357, 3785-3790. doi:10.1016/j.jnoncrysol.2011.07.028

 Patents

  • Polák, M., Němec, L., Cincibusová, P., Jebavá, M., Brada, J., Trochta, M., Kloužek, J. (2015): Method of continuous glass melting under controlled convection of glass melt. Patent No. CZ C 03 B 5/027. UPV
  • Polák, M., Němec, L., Cincibusová, P., Jebavá, M., Brada, J., Trochta, M., Kloužek, J. (2014): Glass melting furnace for continuous glass melting with controlled melt convection. Patent No. CZ 304703. UPV
  • Němec, L., Kloužek, J., Tonarová, V., Jebavá, M. (2014): The device for glass melt fining by centrifuging. Patent No. CZ 304299. UPV
  • Němec, L., Kloužek, J., Tonarová, V., Jebavá, M. (2013): Method of glass fining by centrifuging. Patent No. CZ 304044. UPV

Updated: 15.11.2015 11:43, Author: Jaroslav Kloužek

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