Consumptions
On the Consumption Page AlPrg determines the total or the
specific consumptions depending which data are input and which values are
calculated. When you click into an activated input field you change the value
with the keyboard or the mouse wheel and AlPrg calculates the corresponding
output values. When you click into an inactive input field it becomes activated
(a corresponding activated field turns inactivated) and you change the values as
described.
The Consumption Page takes values like the current efficiency and aluminum
production from the Aluminum
Production Page.
Energy Consumptions
If the pot voltage is input AlPrg calculates the specific
electric energy consumption (Espec) according to
Equ. 2
of the Energy Balance
using the values of the Aluminum Production Page
(current efficiency CE = 95 %). The determination of
the consumption of electric energy uses then
Equ. 1b
with 300 pots (npot = 300), the electric current I = 135 kA
and the time period of one year (t = 365×24 = 8760 h) with 1 TWh (tera watt hour) being 1012 Wh.
If you want to change the value of the specific energy consumption (Espec = 1 4.0kWH/kg, for instance)
you click on the input field for the specific electric energy consumption. After you have changed the value,
AlPrg calculates 1.583 TWh for the total electric energy consumption and 4.463 V for the pot voltage.
Input Specific Electric Energy Consumption.
You click into the Specific Electric Energy input field to activate it. You may change now the value with the keyboard or the mouse wheel. AlPrg calculates the corresponding total electric energy consumption and pot voltage and shows the values in the desactivated input fields.
If you want to do the same with the total electric energy you get for E = 17.0 TWh, for instance, a specific electric energy consumption of 15.031 kWh/kg and a pot voltage of 4.792 V.
Input Total Electric Energy Consumption.
In the same way you click into the Total Electric Energy Consumption input field to activate it and to change its value. The output i.e. the result of calculation is the specific electric energy consumption and the pot voltage.
Alumina Consumptions
AlPrg takes the electrolytic specific alumina consumption from Equ.
9c of the Mass
Balance. The total value is calculated with the alumina production (pAl = 113.102×103
t) from the Aluminum
Production Page.
You may enter the specific alumina consumption to calculate the total value or
you enter the total alumina consumption (240'000 t, for instance) and you
receive the specific value (2122.0 g/kg)
Input Total Alumina Consumption.
In a similar way you click into the Total Alumina Consumption input field to activate it and to change its value. Output is the specific alumina consumption.
Anode Consumptions
You find a description of the meaning of the different anode consumption in Mass Balance. On the Consumption Page you select between the input of the gross anode consumption and or butts with the other consumption. The next figure shows the input of gross anode consumption and butts (a), gross anode consumption and net anode consumption (b), gross anode consumption and excess anode consumption (c).
Input Gross Anode Consumption.
If you select the Gross Anode Consumption for input you may select likewise one of the other consumptions: a) butts, b) net or c) excess consumption.
If you click twice on the gross anode consumption input field you want the butts as primary input together with the net anode consumption (d) or you chosse butts with excess anode consumption (e).
Input Anode Butts.
If you select the butts as primary input you may click on net anode consumption(d) or excess anode consumption (e).
Remark:
you may enter the butts by value (70 g/kg on the figure above) or as percent
of the gross anode consumption (13.46 %).
The input procedure described for the specific anode consumptions can be applied
in the same way to the total anode consumptions.
Aluminum Fluoride Consumptions
To keep the aluminum fluoride content of the electrolyte constant an aluminum fluoride feeder adds aluminum fluoride from time to time. This aluminum fluoride consumption is due to several sinks and sources:
 |
Sodium Oxide: aluminum fluoride reacts with the sodium oxide of alumina to form cryolite and aluminum oxide, |
|
Carbon Blocks: the carbon lining of the electrolytic pot absorbs sodium fluoride. These carbon blocks are a source or sink of aluminum fluoride. Absorption of sodium fluoride increases the aluminum fluoride content in the electrolyte. Correspondingly the desorption of sodium fluoride decreases the aluminum fluoride concentrations., |
|
Ledge, Sludge: there are other sources (or sinks) of aluminum fluoride: the composition of solid ledge may be different to the electrolyte similar as the composition of bottom sludge. Melting of ledge or dissolution will change the content of aluminum fluoride in the electrolyte. |
|
Charged Alumina: in the scrubber alumina adsorbs fluoride compounds which will change the electrolyte composition when alumina is dissolved. |
Modern aluminum smelting plants collect and recycle
up to 99 % of the material that was prior lost to the environment. The mean
reason of the aluminum fluoride consumption of the electrolytic pots is the
reaction of aluminum fluoride with the sodium oxide of the alumina (see Equ. 2).
AlPrg takes care of these factors in the following way: you specify the sodium oxide content of
alumina and AlPrg calculates with Equ. 3
the corresponding total and specific alumina fluoride consumption and cryolite
production using the the corresponding alumina consumption.
You may either specify the consumption of the contributors like carbon blocks, ledge, bottom sludge, alumina and
AlPrg calculates the total aluminum fluoride consumption (consumption due to sodium oxide plus other losses).
Aluminum Fluoride Consumption: Input other Losses.
You enter the sodium oxide content and AlPrg calculates the
corresponding aluminum fluoride consumption (total and specific) and the
cryolite production.
This figure shows that the input field of the Other Losses (into the carbon
blocks, ledge or sludge, with the charged alumina) was selected. AlPrg
calculates the total aluminum fluoride consumption.
Or you enter the value of total aluminum fluoride consumption and ElysePrg calculates the consumption value for the other consumers. You make your selection by clicking on that field where you want to make the input.
Aluminum Fluoride Consumption: Input total Loss.
In this figure the input field of the total loss is active. AlPrg calculates now the other losses.