Energy Balance Page
On the Energy Balance Page the user sees main and intermediate values and calculation results AlPrg is using
to determine the heat production (see
Haupin Diagrams). This heat must be removed from the electrolytic cell (heat loss) to keep the cell in an
thermal stationary state.
Similar to the other cell voltage pages the user may switch
between reference and actual current intensity values. You select like on the
Cell Voltage Page with the Units Combo Box the units of the Energy Balance
Page (about unit conversion see Table I and II
of the theoretical part).With the +/- button he may show and hide some intermediate values.
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Energy Balance Page. The Energy Balance Page contains main and intermediate values that AlPrg is using to determine the heat loss. Similar to the Cell Voltage Page you select with the Units Combo Box the units of the Energy Balance Page. With the +/- button you show or hide some intermediate values. |
To understand the meaning of the values on the Energy Balance page the next figures shows the energy balance values in voltages (V), specific energies (kWh/kgAl) and power (kW).
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Energy Balance in Different Units. With the Unit Combo Box you select how AlPrg represents the values on the Energy Balance Page: Voltages (V), Specific Energy (kWh/kg) or Power (kW). How to convert the units please see Table I and II of the theoretical part. |
These values add up in the following way: from the total electric power input (Electric Power: 840 kW) the Internal Power part (786 kW) enters into the electrolytic cell (Electric Power minus External Busbars). The Heat Production (or Heat Loss 377 kW) is Internal Power (786 kW) minus Consumption (409 kW). The consumption value (409 kW) is the sum of the power to heat up alumina (36 kW) and the anodes (9 kW) and the power to produce alumina (Reaction: 365 kW). The Reaction value (365 kW) is the amount to decompose alumina into aluminum and oxygen minus the carbon reaction with oxygen to produce carbon dioxide (184 kW) and the reaction of aluminum with carbon dioxide to produce carbon monoxide and alumina (Reoxidation Reaction, 6 kW). The internal busbars contribute with 64 kW to the internal balance. Negative values are power consumptions and positive values correspondingly power productions.
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Summing Up This figure shows how AlPrg adds the starting values and the intermediate results to determine finally the heat loss of the electrolytic cell. |
Inert Anodes
After clicking on the Carbon/Inert Anode Button AlPrg calculates the energy balance for an electrolytic cell that uses inert non consumable anodes. Since the inert anodes stay much longer compared to the carbon anodes in the electrolytic cell the amount to heat the anodes is neglected. Since the anode is non consumable i.e. it produces oxygen there is no contribution of the carbon-oxygen and aluminum-carbon dioxyde reaction. Consequently the heat production is reduced when all the cell voltage is the same. To operate an electrolytic cell with inert anodes and the same heat production compared to a cell with carbon anodes (same thermal insulation) the cell voltage or the current intensity must be adapted.
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Energy Balance Inert Anodes An electrolytic cell using inert non consumable anodes produces aluminum and oxygen. The reaction consumes more energy and consequently the heat production is reduced compared with a cell using carbon anodes. To produce aluminum with the same heat loss the current intensity and/or the cell voltage of the inert anode cell must be adapted. |