 |
|
| Table 1: Bleaching chemical pulps over the past 50 years. |
| Year |
1950-1975 |
1975-1990 |
>1990 |
| Stages used |
C |
C |
O |
D |
P |
| in the bleaching |
E |
E |
(EO) |
(DC) |
(PO) |
| sequence |
H |
(DC) |
(EOP) |
C |
Q |
| |
D |
|
(EP) |
O |
Z |
| |
87 |
|
|
(EO) |
PAA |
| |
|
|
|
(EOP) |
Px |
| |
|
|
|
|
X |
| C: chlorine; E: alkaline extraction; H: hypochlorite; D: chlorine dioxide; (DC): a combination of chlorine and chlorine dioxide; O: oxygen; (EO): alkaline extraction under mild oxygen pressure; (EP): alkaline extraction under hydrogen peroxide; (EOP): alkaline extraction under both mild oxygen pressure and hydrogen peroxide; P: peroxide; (PO): hydrogen peroxide under oxygen pressure; Q: chelation; Z: ozone; PAA: peroxyacetic acid; Px: peroxymonosulfuric acid; X: enzymes |
|