Table 2 Central composite design (CCD) for alkaline treatment (AT) of stillage: values and corresponding levels of factors as well as the basic layout of a three-factor CCD
Factor | Levels | |||||
|---|---|---|---|---|---|---|
− α | − 1 | 0 | + 1 | + α | ||
Reaction time tR (min) | 26 | 40 | 60 | 80 | 94 |
|
Temperature T (°C) | 19 | 60 | 120 | 180 | 221 | |
NaOH concentration c (mol/L) | 0.07 | 0.10 | 0.15 | 0.20 | 0.23 | |
