Table 2: Analysis of DEopDED Bleaching
|
Hardwood |
||
|
Pulps |
||
|
Conventional Delignification |
Oxygen Delignifications |
|
|
Final Brightness |
89.3 |
90.0 |
|
Number of ECF Bleach Plants |
7 |
4 |
|
Pre-O2 Kappa Number |
16.9 |
|
|
O2 Delignification, % |
32.5 |
|
|
D0 Stage Information |
||
|
Kappa Number to D0 Stage |
14.4 |
10.3 |
|
Plants using Enzyme |
0 |
0 |
|
COD Carryover, kg/ADMt |
11.2 |
5.9 |
|
Na2SO4 Carryover, kg/ADMt |
6.7 |
10.9 |
|
Retention Time, min. |
45 |
39 |
|
Do Stage Temperature, °C |
55 |
60 |
|
End pH |
2.5 |
2.8 |
|
ClO2, kg/ADMt |
12.2 |
12.1 |
|
Kappa Factor |
0.22 |
0.32 |
|
No. |
No. |
|
|
D0 Stage Consistency, Medium |
2 |
2 |
|
D0 Stage Consistency, Low |
5 |
2 |
|
D0 Stage Upflow |
7 |
3 |
|
D0 Stage Upflow/Downflow |
0 |
1 |
|
Acid Added |
6 |
4 |
|
H2SO4 |
6 |
4 |
|
CO2 to brownstock |
1 |
1 |
|
First Stage Control |
No. |
No. |
|
Pre-tower Optical Sensor |
7 |
4 |
|
Pre-tower Residual Sensor |
7 |
4 |
|
Post-tower Optical |
1 |
1 |
|
Post-tower Residual |
0 |
2 |
|
Kappa Analyser |
5 |
3 |
|
Control to D0 Brightness |
3 |
1 |
|
Control to Eo(p) Brightness |
1 |
3 |
|
Control to Eo(p) Kappa Number |
3 |
2 |
|
Hardwood |
||
|
Pulps |
||
|
Conventional Delignification |
Oxygen Delignfication |
|
|
Final Brightness |
89.3 |
90.0 |
|
Number of ECF Bleach Plants |
7 |
4 |
|
Extraction Stage Information |
||
|
Eop Kappa Number |
4.4 |
2.6 |
|
Eop Brightness |
57 |
79 |
|
End pH |
10.9 |
10.7 |
|
NaOH, kg/ADMt |
13.9 |
14.1 |
|
NaOH/Eq. Cl2 with Papricycle |
0.28 |
- |
|
NaOH/Eq. Cl2 without Papricycle |
0.49 |
0.47 |
|
Oxygen Addition*, kg/ADMt |
4.5 |
4.2 |
|
H2O2 Addition*, kg/ADMt |
6.0 |
3.3 |
|
Kappa Factor** after Eo(p) Stage |
0.36 |
0.50 |
|
% Delignification after Eo(p) Stage |
68 |
75 |
|
∆% Eq. Cl2 per ∆ Kappa No.*** |
0.52 |
0.71 |
|
Retention Time @ pressure, min. |
54 |
15 |
|
Temperature, °C |
74 |
72 |
|
No. |
No. |
|
|
Oxygen Added |
5 |
3 |
|
Hydrogen Peroxide Added |
3 |
3 |
|
Papricycle® |
2 |
0 |
|
Extraction Stage Control |
No. |
No. |
|
Kappa Analyser |
3 |
1 |
|
Control to end pH |
6 |
3 |
|
Control to Eo(p) Brightness |
1 |
3 |
|
Control to Eo(p) Kappa Number |
1 |
1 |
* When added.
** Sum of chlorine dioxide in first stage plus oxygen and hydrogen peroxide in extraction - all expressed as % equivalent chlorine on pulp divided by unbleached kappa no.
***All oxidizing chemicals in the D0 and Eo(p) stages as % equivalent chlorine divided by the change in kappa number (i.e., unbleached kappa no. minus the extracted kappa no.)
|
Hardwood |
||
|
Pulps |
||
|
Conventional Delignification |
Oxygen Delignification |
|
|
Final Brightness |
89.3 |
90.0 |
|
Number of ECF Bleach Plants |
7 |
4 |
|
First ClO2 Brightening (D1) Stage Information |
||
|
Retention Time, min. |
124 |
173 |
|
Temperature, °C |
72 |
79 |
|
Upflow pH |
3.9 |
4.3 |
|
End pH |
3.7 |
4.0 |
|
Brightness, % ISO |
85.9 |
87.6 |
|
ClO2, kg/ADMt |
9.0 |
5.5 |
|
ClO2, per Eop kappa, kg/kappa unit |
2.3 |
2.0 |
|
NaOH, kg/ADMt* |
1.4 |
1.0 |
|
H2SO4, kg/ADMt* |
0.0 |
2.6 |
|
DEopD Kappa Factor |
0.52 |
0.61 |
|
First ClO2 Brightening (D1) Control Strategy |
No. |
No. |
|
Pre- ClO2 Mixer Optical Sensor |
0 |
2 |
|
Pre-tower Optical Sensor |
4 |
2 |
|
Pre-tower Residual Sensor |
5 |
4 |
|
Control to End of Stage Residual |
4 |
0 |
|
Control to Compensated Brightness |
2 |
0 |
|
Control to D1 Brightness |
5 |
4 |
|
Control to Upflow pH |
4 |
2 |
|
Add NaOH for pH Control |
2 |
1 |
|
Add H2SO4 for pH Control |
0 |
1 |
|
Control to End pH |
2 |
2 |
|
Antichlor Added |
2 |
0 |
SO2 |
2 |
0 |
NaOH |
0 |
0 |
* When added
|
Hardwood |
||||
|
Pulps |
||||
|
Conventional Delignification |
Oxygen Delignficiation |
|||
|
Final Brightness |
89.3 |
90.0 |
||
|
Number of ECF Bleach Plants |
7 |
4 |
||
|
Second Extraction (E2) Stage Information |
||||
|
NaOH, kg/ADMt (Short Stage)* |
5.9 |
5.7 |
||
|
NaOH, kg/ADMt (Conv. Stage)** |
5.0 |
3.8 |
||
|
H2O2, kg/ADMt, (when used) |
5.0 |
- |
||
|
Brightness, % ISO |
85.9 |
- |
||
|
End pH |
10.2 |
10.4 |
||
|
Retention Time, min. |
50 |
90 |
||
|
Temperature, °C |
76 |
75 |
||
|
No. |
No. |
|||
|
Conventional Stage |
6 |
0 |
||
|
Short Extraction Stage |
0 |
1 |
||
|
Control to End pH |
3 |
2 |
||
|
Stages with H2O2 |
1 |
0 |
||
* (Dn)D
** DED
|
Hardwood |
||
|
Pulps |
||
|
Conventional Delignfication |
Oxygen Delignification |
|
|
Final Brightness |
89.3 |
90.0 |
|
Number of ECF Bleach Plants |
7 |
4 |
|
Second ClO2 Brightening (D2) Stage Information |
||
|
Retention Time, min. |
141 |
190 |
|
Stage Temperature, °C |
77 |
79 |
|
Upflow pH |
4.4 |
4.4 |
|
End pH |
4.1 |
3.8 |
|
Brightness, % ISO |
89.3 |
90.0 |
|
ClO2, kg/ADMt |
3.5 |
2.7 |
|
Second ClO2 Brightening (D2) Control Strategy |
No. |
No. |
|
Pre-ClO2 Mixer Optical Sensor |
0 |
1 |
|
Pre-tower Optical Sensor |
1 |
1 |
|
Pre-tower Residual Sensor |
2 |
1 |
|
Control to End of Stage Residual |
3 |
2 |
|
Control to Compensated Brightness |
0 |
1 |
|
Control to D2 Brightness |
3 |
3 |
|
Control to Upflow pH |
3 |
2 |
|
Add NaOH for pH Control |
3 |
2 |
|
Add H2SO4 for pH Control |
0 |
1 |
|
Control to End pH |
3 |
3 |
|
Antichlor Added |
3 |
3 |
SO2 |
2 |
3 |
NaOH |
0 |
0 |
H2O2 |
1 |
0 |
|
Hardwood |
||
|
Pulps |
||
|
Conventional Delignification |
Oxygen Delignification |
|
|
Final Brightness |
89.3 |
90.0 |
|
Number of ECF Bleach Plants |
7 |
4 |
|
Overall Chemical Consumption |
||
|
ClO2, kg/ADMt |
24.2 |
19.7 |
|
O2, kg/ADMt |
3.2 |
3.1 |
|
H2O2, kg/ADMt |
3.3 |
2.5 |
|
NaOH, kg/ADMt |
17.9 |
16.7 |
|
Sequence Kappa Factor* |
0.59 |
0.68 |
|
Bleaching Cost, Cdn $/ADMt** |
33.35 |
27.71 |
|
Efficiency, Cdn $/Kappa No. |
2.35 |
2.67 |
|
|
||
* Sum of chlorine dioxide in all stages plus oxygen and hydrogen peroxide in extraction stages - all expressed as % equivalent chlorine on pulp divided by unbleached kappa no.
**Cdn $: ClO2 @ $1/kg, H2O2 @ $0.90/kg, NaOH @ $0.34/kg, O2 @ $0.05/kg, cost of enzyme @ $2.00 per ADMt.
Optimization Summary - Conventionally Delignified Hardwood Pulps
|
Category |
Rating (out of 5) |
|
Minimize ClO2 |
4.0 |
|
Minimize Bleaching Cost |
3.96 |
|
Maximize Brightness |
3.7 |
|
Minimize Shives |
3.6 |
|
Compensate for Short Retention |
3.0 |
|
Maximize Pulp Strength |
3.0 |
|
Compensate for Short Sequence |
2.9 |
|
Minimize TOX in Pulp |
2.9 |
|
Minimize AOX |
2.7 |
|
Achieve Low Kappa No. |
2.7 |
Optimization Summary – Oxygen Delignified Hardwood Pulps
|
Category |
Rating (out of 5) |
|
Maximize Brightness |
4.5 |
|
Minimize Bleaching Cost |
4.5 |
|
Minimize ClO2 |
4.0 |
|
Minimize TOX in Pulp |
3.6 |
|
Maximize Pulp Strength |
3.5 |
|
Minimize Shives |
3.5 |
|
Achieve Low Kappa No. |
3.5 |
|
Compensate for Short Sequence |
3.3 |
|
Minimize AOX |
3.0 |
|
Compensate for Short Retention |
3.0 |
Optimization Rating Scheme
1 - Strongly disagree
2 - Disagree
3 - No opinion/not applicable
4 - Agree
5 - Strongly agree