Melting

Question 1

Why does the batch pile float on the molten glass? What is the result?

Answer 1

~ the bulk density of the batch is half that of the melt

~ the batch pile insulates the melt underneath from radiation heating

Question 2

When does eutectic liquid form? Between what compounds?

Answer 2

~ sodium disilicate and silica form eutectic at 800C

Question 3

What happens after the melting of soda ash at 850?

Answer 3

~ the reaction SiO2 + Na2CO3 –> Na2O*SiO2 + CO2 occurs violently

Question 4

What is the result of the released CO2 gas?

Answer 4

~ mixing effect, accelerates dissolution of refractory particles

Question 5

What increases the viscosity of the alkali carbonate (soluble in water) liquid?

Answer 5

~ solution of silica and alumina increases viscosity by four orders of magnitude

Question 6

How does limestone decompose in the liquid?

Answer 6

~ it resists wetting by the soda silica liquid

~ decomposition proceeds gradually, done at 1350C

Question 7

What is the result of continuous dissolution of sand?

Answer 7

~ decreases CO2 solubility in liquid, producing bubbles at the liquid-sand interfaces

Question 8

What occurs during the final stages of melting?

Answer 8

~ slow dissolution of the remaining silica particle residue

Question 9

What is the last compund to be soluble in the liquid phase?

Answer 9

~ silica