Tungsten is extracted from the mineral scheelite (CaWO4) by roasting it with natrite (Na2CO3) at a temperature of about 700 °C. This converts the CaWO4 to water soluble sodium tungstate (NazWO4). The solid product from the roaster (called "calcine") is transferred to a leacher. In the leacher chilled water is added to dissolve the NazWO4. The chilled water dissolves only the NazWO4 in the solid calcine. The scheelite that enters the roast is mixed with gypsum (CaSO4-2H2O). This stream is 85.2%w CaWO4 and 14.8%w CaSO4-2H2O. (%w means “percent-by-weight.") Four reactions take place during this process. In the roaster: 1: CaWO4 + Na2CO3 - NazWO4 + CaO + CO2 2: CaSO4•2H2O – CaSO4 + 2H2O In the leacher:
Tungsten is extracted from the mineral scheelite (CaWO4) by roasting it with natrite (Na2CO3) at a temperature of about 700 °C. This converts the CaWO4 to water soluble sodium tungstate (NazWO4). The solid product from the roaster (called "calcine") is transferred to a leacher. In the leacher chilled water is added to dissolve the NazWO4. The chilled water dissolves only the NazWO4 in the solid calcine. The scheelite that enters the roast is mixed with gypsum (CaSO4-2H2O). This stream is 85.2%w CaWO4 and 14.8%w CaSO4-2H2O. (%w means “percent-by-weight.") Four reactions take place during this process. In the roaster: 1: CaWO4 + Na2CO3 - NazWO4 + CaO + CO2 2: CaSO4•2H2O – CaSO4 + 2H2O In the leacher:
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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
Transcribed Image Text:Feed 1
Water
4,000 g
3,000 g
85.2%w CaWO4
14.8%w CaSO4-2H2O
Offgas
Leach
solution
- - -
"Calcine"
Roaster
Leacher
~700 C
22.38%w Na2WO4
Feed 2
660 g
Na2ČO3
Insoluble
solids
solid lines: solid-phase streams
dashed line: liquid-phase stream
dotted line: gas-phase stream

Transcribed Image Text:Tungsten is extracted from the mineral scheelite (CaWO4) by roasting it with natrite (Na2CO3) at a
temperature of about 700 °C. This converts the CaWO4 to water soluble sodium tungstate (NazWO4).
The solid product from the roaster (called "calcine") is transferred to a leacher. In the leacher chilled
water is added to dissolve the NazWO4. The chilled water dissolves only the NazWO4 in the solid
calcine. The scheelite that enters the roast is mixed with gypsum (CaSO4-2H2O). This stream is
85.2%w CaWO4 and 14.8%w CaSO4-2H2O. (%w means “percent-by-weight.")
Four reactions take place during this process.
In the roaster:
1: CaWO4 + Na2CO3 - NazWO4 + CaO + CO2
2: CaSO4•2H2O - CaSO4 + 2H2O
In the leacher:
3: СаО + H2О —- Са(ОН)2
4: CaSO4 + 2H2O - CaSO4 2H2O
The first reaction does not go to completion, all the other reactions do go to completion.
For the conditions shown in the process diagram on the next page calculate the conversion of the
CaWO4 in the roaster.
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