Variable

Parameter

Low Value

Median Value

High Value

Time (min)

A

0

60

120

Slurry (%)

B

5

10

15

Molar ratio (Na2CO3/Gypsum )

C

0.8

1.4

2

Stirring speed (rpm)

D

100

300

500

Table 3: Levels of factors chosen for the experimental design.