Exercises for Part I: HSC

Transcription

1 Thermodynamic and process modelling in metallurgy and mineral processing S 17 August 2018 Exercises for Part I: HSC This document contains exercises for different modules of the HSC software. It should be noted that these exercises are not taken into account in the grading of the course S Thermodynamic and process modelling in metallurgy and mineral processing. In order to pass the course, it is necessary to make a larger assignment, which is described in more detail in separate document that can be found from the course wwwsite: During the course, there are 12 lectures during which it is possible to practice the use of different modules with these exercises. The larger assignment required to pass the course should also be completed during these lectures. In 2018, the lectures are on Tuedays from 12 to 14 and on Fridays from 10 to 12 on weeks with an exception of weeks 38 and 41 during which there are no lectures. During the lectures it also possible to ask instructions concerning these exercises as well as larger assignment. More detailed information about all the modules of the HSC software is available in the Help (?) module. Exercises for Periodic chart -module Periodic chart (Ele) module contains data about various properties of different elements. Familiarize yourself with this module by checking what kind of information is available for different elements (choose an element by clicking the element of your interest in the periodic chart and the data corresponding this element appears on the right). University of Oulu Oulun yliopisto P.O.Box 8000 FI University of Oulu oulu.fi T fax Additionally, this module can be used to illustrate how different properties of the elements depend on their positions in the periodic table. Choose property of your interest from the menu on the bottom. Show/Hide Legend/Data buttons can be used to show and hide the legend explaining the color codes of the elements in the periodic table and property data on the right, respectively. 1 / 8

2 Exercises for Measure units -module Measure units (Mea) module can be used to convert units. As an exercise, check what units are available for e.g. energy, length, mass and temperature. Make some unit conversions of your own choice just for practice. Note that in addition to making conversions in the Convert sheet you can check the rules of conversion from the Units sheet. Furthermore, some universal constants, grain size tables and data about air and water can be found from the Constants -, Mesh -, Air - and H2O -sheets. Exercises for H,S and Cp database Familiarize yourself with different options to search thermodynamic data from the database (DB): - based on elements, chemical formula or name - use of filters. Familiarize yourself with the denotation used in the HSC software. How different kind of species (gaseous, liquid, solid with different crystal structures, aqueous, ions, etc.) are denoted in the database? Check what kind of thermodynamic data is available for each species and remind yourself how this data is used in equilibrium calculations. Pay special attention on how specific heat capacities are presented in the HSC database. Why specific heat capacities are of special importance in thermodynamic calculations? Finally, check how the references are marked by choosing one species and checking from which source/reference the data for this compound has been taken. After using different modules of the HSC software, try to use Browse and Insert species -options to find certain species (and their thermodynamic data) from the database and then import this data to different modules that are being used. Exercises for H,S,Cp,G diagrams -module With the H, S, Cp and G diagrams (Dia) module it is possible to draw diagrams in which different thermodynamic properties are presented graphically as a function of temperature. Draw a few diagrams for species of your own choice and practice: 2 / 8

3 - how to add species for the diagram (either by writing the chemical formula or by browsing the database), - what kind of properties can be presented (i.e. what kind of diagram types are available), - what is the difference between H, S and G diagrams and deltah, deltas and deltag diagrams, - how the temperature range and units are changed, - how to change the energy units, - how to re-scace the diagram axis - and how to draw diagrams for kg of material instead of mol. When creating so-called Ellingham diagrams, it is necessary to study the Gibbs free energies of formation for certain compounds in a way that all the formation reactions are comparable (e.g. all the oxide formation reactions are written for 1 mol of O 2 ). How can you do this in the H, S, Cp and G diagrams (Dia) module? Check also how the diagrams can be saved (in which formats) and how they can be copied and pasted into other applications such as MS-Word. Exercises for Reaction equations -module The Reaction equations (Rea) module can be used to study individual chemical reactions. Study few reactions of your own choice and practice: - how to define the chemical reaction (either by writing the chemical formula or by browsing the database), - how to balance the stoichiometric coefficients of the reaction, - how to define the temperatures in which reaction is considered, - how to change the units for temperature and energy, - how to draw diagrams in which thermodynamic properties (entalphy, entropy, Gibbs free energy, etc.) for studied reaction can be illustrated as a function of temperature, - how to draw diagrams with several chemical reactions, - how to rescale the diagram axis, - how to save the results (values and figures) 3 / 8

4 - and how to copy and paste data from HSC software to other applications such as MS-Excel and MS-Word. Additionally, remind yourself what does it mean if entalphy of certain chemical reaction at given temperature has either positive or negative values. Furthermore, what can be concluded based on the values of Gibbs free energy at different temperatures? Exercises for Equilibrium compositions -module The Equilibrium compositions (Gem) module can be used to study reaction systems in which several chemical reactions take place. When using the Equilibrium compositions (Gem) module it is essential to know how to define the system for the calculations, because the software does not correct you from making non-realistic or non-relevant assumptions in your system description. For instance, it is important to check that all the relevant phases are defined and the phases include all the necessary species. When defining your system, beware of these typical mistakes made by novice users: - gas components are not defined in the same phase, - some phase and/or species is not defined because its amount in the initial state is zero, and it is hence forgotten in the system definition (NB: Only the phases/species that are defined can exist in the equilibrium state.), - aqueous species are not defined in the same phase and/or water (H2O(l)) is missing, - there is mistake concerning the state of certain species (i.e. H2O for liquid water and solid ice, but H2O(g) for water vapour), - and some species are defined in the same phase even though they are not soluble into each other in reality. In the system definition, the user needs to define (a) the possible phases, (b) the species possibly existing in these phases and (c) the total (initial) composition of the system. This information is entered on the left side of the module window. Additionally, the user needs to define the conditions for which the calculations are made and this information is entered on the right side of the window. It is possible to define the parameters used in the calculations and make the calculations with 0, 1 or 2 independent variables. Minimum and maximum values as well as the amount of steps must be entered for all the used variables. After defining the system, user makes the calculations with the Calculate button after which the figures can be drawn based on the results with the Show Chart button. 4 / 8

5 Practice the use of Equilibrium compositions (Gem) module with following examples: - Study the combustion of methane with varying amounts of oxygen (amounts more, less and equal to stoichiometric amount needed for perfect burning). What is the influence of temperature and pressure on the equilibrium composition of the off-gas? - Study the combustion of methane with varying amounts of air consisting of oxygen and nitrogen? How do the system definition and the results differ from the previous example? - Study the reduction of certain oxide (e.g. CuO, Fe 2 O 3 or MnO) with carbon in different temperatures. Define temperatures in which reduction is possible. Remember to define the possible intermediate products of reduction if they might exist. What is the reaction product of carbon and oxygen? You can also create your own examples of your own interest. Practice also how to save your system definitions and results and how to copy and paste your results to other applications. It should be noted that with an exception of aqueous solutions, only ideal solutions can be considered with the standard version of the Equilibrium compositions (Gem) module. However, it is possible to add models describing the unideality of solutions in the software, but it requires some programming skills and some time and hence not considered within this course. More information is available in the Help module of the HSC software for those interested in this area. Exercises for Heat & material balances -module With Heat & material balances (Bal) module it is possible to estimate the heat balance of chemical systems: i.e. how much extra energy is needed or alternatively, how much energy is released. The user needs to enter all input and output materials as well as their amounts and temperatures into the IN1 and OUT2 sheets and this information must be available from either analyses, other calculations, etc. It is noteworthy, that it is possible to use Excel-type formulas in the IN1 and OUT2 sheets; e.g. to calculate the amount of certain output species based on the amount of certain input species or vice versa. For more complicated systems it is sometimes easier to have additional sheets from which values can be read to the IN1 and OUT2 sheets. The amounts of species can be entered as kmol or kg (for solid and liquid species) and as kmol or kg or Nm 3 (for gaseous species). Be careful when making references so that you refer to correct columns in order to avoid 5 / 8

6 mistakes due to wrong units. Extra heat and/or heat losses can be added to the system as MJ or kwh. After entering all the necessary information user should first check that the material balance is accurate enough. In other words it should be confirmed that the amounts of all the elements in the input streams correspond with the amounts of these elements in the output streams. This element balance is seen at the bottom of the module window and it could be opened in a separate window using Calculate Element Balance option. After fixing the material balance it is possible to estimate the heat balance of the system. Heat balance can be seen on BALANCE sheet and summarized on the bottom left corner of the module window. In addition to this, it is possible to calculate so-called adiabatic temperature which means the temperature for the output species in which the heat balance has a value of zero. This can be done using Calculate Temperature Balance option. Practice the use of Equilibrium compositions (Gem) module with examples of your own choice or by creating a heat balances for the systems you studied with the Equilibrium compositions (Gem) module (i.e. combustion of methane with oxygen or air and reduction of oxides). Exercises for Lpp/Tpp stability diagrams -module Phase stability diagrams (so-called Kellogg diagrams) can be drawn using Stability diagrams (Lpp/Tpp) modules. Although quite similar diagrams may be created with both of these two modules, the calculation routines used in these modules differ from one another. Hence, the information needed for the calculations also depends on which module is being used. In the Stability diagrams (Lpp) module the user selects three elements one of which forms compounds with the other two elements (e.g. iron that forms oxides with oxygen, sulphides with sulphur and sulphates with both of them). After selecting three elements, the module searches the database for the species that can be formed from these elements and creates a list of available species. The user may then choose the species (s)he wants to take into account or just select all the available species to be taken into account in the calculations. After choosing the relevant species the user must define the variables used as x- and y-axes. The axes of the Kellogg diagrams represent partial pressures (or activities) of two species (e.g. partial pressures of oxygen or sulphur dioxide or activity of carbon). Minimun and maximum values for the axes may be entered or Auto scale option may be used. Finally, the user must define the temperature for which the calculations are made and use Draw diagram button to finish the diagram that will be shown on the right side of the module window. The use of Stability diagrams (Tpp) module does not differ very much from the use of Stability diagrams (Lpp) module. Two major differences are as follows: - Auto scale option is not available in Tpp module. 6 / 8

7 - In the Lpp module temperature must be held constant and in order to study the effect of temperature on the phase stabilities it is necessary to create separate diagram for each temperature being considered. In the Tpp module temperature may be used as an variable, which means that only one potential variable (i.e. partial pressure or activity) may be used as a variable, too. If temperature is used as a variable, one partial pressure needs to be held constant in order to fix the degree of freedom to zero. Choose the system (i.e. elements, axis variables and temperature) of your interest and practice the use of these two modules: e.g. how to create a diagram, how to rescale it and how to save/copy/paste it to other applications. Exercises for Eh-pH diagrams -module The Eh-pH diagrams (EpH) module can be used to create so-called Pourbaix diagrams. First, the user chooses one or more elements to be presented in the diagram. Similarly to Lpp and Tpp modules the EpH module also searches the species from the database based on the elements the user has chosen. The user can then select the species taken into account in the calculations or just choose to select all the possible species. Before drawing the diagrams, some additional information about the considered system may be entered. This includes properties of water such as dielectric constant and Gibbs free energy of formation, scaling of the axes, temperature and molalities of considered elements in the electrolytic solution. After fixing all the parameters, Draw button is used to creat the diagram that is drawn on the right side of the module window. The diagram shows the stability regions of different species as a function of ph and (oxidizing) potential, E. Combiner option may be used if phase boundaries representing different values of parameters (such as molalities and temperature) are needed in the same diagram. Choose a system of your own interest and practice the use of this module: e.g. how to change the parameters, how the diagram is changed if the species to be considered are chosen differently, how to use the Combiner option, how to rescale the diagram and how to save/copy/paste the diagram for other applications. Exercises for Species converter -module The Species converter (Con) module can be used to change the components according to which the chemical composition is presented. First, the user enters the chemical composition of the system (s)he is interested in on the left column using the components that are known. At 7 / 8

8 this point it should be verified that the total amount of components equals 100%. After entering the composition using the known components, user must define the components into which (s)he wants to have the composition converted. These new components are entered on the right column. It is important that the new components are chosen in such a way that enables the announcement of original composition with these components. For example, if the original composition is a mixture of metallic iron, chromium and nickel, its composition cannot be announced using CaO, SiO 2 and Al 2 O 3 as new components. After entering both old and new components, Initialize button may be used to calculate the contents of elements based on the original composition. Solve button is then used to report this composition using the new components. If the new components are not chosen properly, the module announces that it is not possible to convert the composition properly. Fix element balance option may be used to try to fix the problem, although one should be careful when using this option since the fixing is purely mathematical and not based on knowledge of the real system. To practice the use of this module, choose a system of your interest and try to convert the components according to which the composition is announced. 8 / 8