In this blog I present and discuss a tool to calculate metallurgical slag liquid viscosity. This tool has been developed using the Microsoft Silverlight technology, which will also be discussed in a bit more detail than was done in the previous post. The calculations have also been developed as user defined functions compiled into a Microsoft Excel add-in, available on request.
Viscosity calculation
To start off, let’s first consider the viscosity calculation. Slag viscosity is an important process variable in pyrometallurgical processes, with the typical importance of relating the slag composition with the ease with which it could be tapped from the furnace. Any material’s viscosity is determined by its chemical composition and the temperature. In the case of metallurgical slags, a silicate network forms increasing the viscosity. Monoxides have a destructive effect on the silicate bonds, with their presence decreasing the viscosity. These same monoxides however, increase the liquidus temperature, stabilising the formation of solid solution phases which has an increasing effect on effective viscosity.
In practice, the ability to estimate a slag’s viscosity based on its composition and temperature enables better and more consistent decision making when based on researched relationships, rather than rules of thumb. This also makes it possible to evaluate slags outside the normal operating conditions where experience has not yet been gained.
Numerous research results could be found in literature attempting to derive viscosity models for specific slag systems. A general model based on the Urbain formalism is presented in the Slag Atlas, 2nd Edition (1995) by dr. KC Mills, (Ch.9, pp. 349 – 354). This model groups the amounts of input species into glass formers (SiO2, P2O5), modifiers (CaO, MgO, Na2O, K2O, CaF2, FeO, MnO, TiO2, and ZrO2), and amphoterics (Al2O3, Fe2O3, and B2O3). Parameters were derived and tuned for these groups from experimental data to model the viscosity from the mole fraction of each component and the temperature. The software presented here provides a tool to estimate the slag viscosity using this Urbain model as published by dr. KC Mills.
This tool allows for the following two calculations:
- Liquid viscosity: Calculates the liquid viscosity for the input chemical composition (mass %’s) and temperature (°C) using the Urbain model publish by dr. KC Mills in the Slag Atlas, 2nd Ed. It is called the liquid viscosity, based on the assumption that the slag specified is fully liquid at the temperature at which viscosity is calculated (temperature is higher than liquidus).
- Temperature for viscosity: The viscosity model above is used to solve the temperature (°C) at which a slag will have the target viscosity specified. This is useful in operation to calculate the temperature that a slag need to be knowing the typical viscosity value predicted by this specific model for slag classified as easy to tap.
Microsoft Silverlight
The application platform chosen for presenting the calculation tool is Microsoft Silverlight. This is a relatively new technology allowing for rich internet applications, that is available in runtime environment as a plug-in to most browsers. Another useful feature is that the applications do not have to run in the browser alone, but could very easily be installed onto a computer, without directly having to download any software, and available off-line.
The viscosity calculation tool has been embedded as a component at the end of this blog, or can be opened in new window by following this link. This means that if the Silverlight plug-in is installed, you should see the fully functional application. If this is not visible, but an icon requesting you to install Silverlight for your browser, this link should first be followed, and probably you browser restarted, to be able to see and use this application. More information on installing Silverlight can be found here.
Out-of-browser application
As noted earlier, the application could be installed onto your computer without having directly to download any software (other than the Silverlight browser plug-in already installed), or requiring administrator privileges. This can be done by merely right-clicking anywhere on the application component in this blog, selecting “Install algoNess Slag Liquid Viscos… onto this computer…”, and following the requests on the next windows. This is shown below.
The viscosity calculation application will then be installed onto your computer, placing a shortcut on your Desktop and in the Start Menu, if these options were chosen. The application can be started like any other application, clicking on the shortcuts.
To remove the application, one can remove it using “Add or Remove Programs” from the “Control Panel”, or by righ-clicking again on the application, and selecting “Remove this application”. This is shown below.
Slag liquid viscosity calculation tool
In the frame below the fully functional slag liquid viscosity calculation tool is presented. This calculates the slag viscosity, or temperature for viscosity, as described earlier. The composition is specified and then either the temperature of target viscosity, and clicking the appropriate “Calculate” button will initiate the calculations.
