Hannu Hämäläinen R&D Manager, SBU Pulp Chemicals Kemira Pulp&Paper Kemira Oyj FI Vaasa FINLAND

Transcription

1 Hannu Hämäläinen R&D Manager, SBU Pulp Chemicals Kemira Pulp&Paper Kemira Oyj FI Vaasa FINLAND Marco A.B. Azevedo, Jorge L. Colodette, Rubens C. Oliveira & Ann H.Mounteer Federal University of Viçosa Viçosa, MG Brazil 4th International Colloquium on Eucalyptus Pulp, Concepcion, Chile May 4-6, 2009

2 There has been a growing demand for light Elemental Chlorine Free (light-ecf) pulps, particularly in Europe, in order to replace the very expensive Totally Chlorine Free (TCF) ones. Currently attends a small market (niche) Slowly replacing TCF bleaching Pulps that contain less than 20 g Cl - /adt pulp of organically bound chlorine (OX), according to standardized methods (ex: ISO 11480) Light ECF pulps are in the bracket of g Cl - /adt of pulp

3 Many bleaching alternatives have been evaluated to minimize chlorine dioxide use for eucalyptus kraft pulps, one of them being the so-called molybdenum activated hydrogen peroxide stage (PMo). Xylanases Ozone Hot acid stage Peroxyacetic acid Peroxymonosulfuric acid Molybdenum activated acid peroxide (PMo stage) etc.

4 A molybdenum activated acid peroxide treatment Molybdenum may come from various sources (NH 4 ) 6 Mo 7 O 24.4H 2 O Na 2 MoO 4.2H 2 O Silicon molybdate (proprietary), etc. Molybdenum is applied in catalytic doses ( g/adt pulp) Peroxide is applied in large doses (5-10 kg/adt pulp)

5 Mimoun, 1980 Eckert, 1982 Sundman & Dence, 1988 Mounteer & Colodette, 1991 Kubelka, Francis, & Dence, 1992 Hämäläinen et al., 2003 (mill trials) Rabelo & Colodette, 2007

6 A molybdenum diperoxide complex formed according to:

7 The advantages of this stage in relation to other stages run under acidic conditions is the minimum formation of oxalic acid that cause scaling in the bleach plant, and decrease formation of organically bound chlorine However, many questions still remain in regard to PMo stage application for eucalyptus pulps. For example, what types of sequences are more suited for applying such stage?

8 What are the impacts of a PMo stage on overall bleaching effluent quality What are the impacts of a PMo stage on bleached pulp refinability and strength properties?

9 Evaluating P Mo stage in various sequences for bleaching eucalyptus pulp of two different origins (high/low bleachability); Determining the impact of using the PMo stage on bleaching effluent load and treatability and on pulp refinability and physical-mechanical properties.

10 Pulp Characteristic* Difficult-to-Bleach Easy-to-Bleach Kappa No Viscosity, mpa.s Brightness, % ISO HexA, mmol/kg *easy- and difficult-to-bleach pulps were defined on the basis of total active chlorine demand to achieve 90% ISO brightness with the D(EP)DP sequence.

11 (NH 4 ) 6 Mo 7 O 24.4H 2 O Temperature: 85 and 95 C ph : 3.0 and 4.5 Mo: 0.10, 0.15 and 0.25 kg/odt pulp Time: 2 h Reaction consistency: 10% H 2 O 2 : 5 kg/odt pulp

12 Reference: D(EP)DP, D HT (EP)DP and A/D(EP)DP D/Q(PO) Z/EDP Novel Bleaching: P MO (EP)DP; A/P MO (EP)DP; AP MO (EP)DP P MO /Q(PO) P MO Z/ED

13 Pulp refined in PFI mill (0, 1000, 2000 and 3000). Tested for physical-mechanical properties according to Tappi standard procedures. Effluent treatability: Bench Scale Activated Sludge System Parameters quantified - COD - BOD - Color - AOX - Suspended solids - Toxicity

14 Parameter Diff.-to-Bleach Pulp Easy-to-Bleach Pulp Bleaching Stage PMo* A/PMo** PMo* A/PMo** Brightness Kappa Number Viscosity, mpa.s Brightness Gain, % ISO Kappa Drop (Efficiency), % Viscosity Drop, % *PMo fixed conditions: 10% consistency; 120 min.; ph 3.0; 0.15 kg Mo/odt; 5 kg/odt H 2 O 2 ; 85 C. **A/PMo fixed conditions: 11/10% consistency; 110/120 min.; ph 3.0; 0.15 kg Mo/odt; 5 kg/odt H 2 O 2 ; 95/ 85 C.

15 SEQUENCE Bright., % ISO Reversion, % ISO Viscosity, mpa.s Relative Chemical Cost Total Active Chlorine Demand, kg/odt pulp D(EP)DP D HT (EP)DP PMo(EP)DP A/D(EP)DP A/PMo(EP)DP D/Q(PO) PMo/Q(PO) Z/EDP PMo(PO)D

16 SEQUENCE Bright., % ISO Reversion, % ISO Visc. mpa.s Relative Chemical Cost Total Active Chlorine Demand, kg/odt pulp D(EP)DP D HT (EP)DP PMo(EP)DP A/D(EP)DP A/PMo(EP)DP Z/EDP PMoZ/ED

17 SEQUENCE Difficult-to-Bleach Pulp Relative Chemical Cost Total Active Chlorine Demand, kg/odt pulp Easy-to-Bleach Pulp Relative Chemical Cost Total Active Chlorine Demand, kg/odt pulp D(EP)DP D HT (EP)DP A/D(EP)DP Z/EDP PMo(EP)DP A/PMo(EP)DP

18 D HT (EP)DP (reference) PMo(EP)DP A/PMo(EP)DP They were evaluated for: Pulp refinability and physical strength Effluent quality and treatability

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20 SR 60 A/PMo(EP)DP PMo(EP)DP DHT(EP)DP Wh

21 Bleaching Process D HT (EP)DP A/PMo(EP)DP PMo(EP)DP Drainage Degree, ºSR PFI Revolutions Energy consumption, W.h Sheet Density, g/cm Bulk, cm 3 /g T.E.A., J/m Modulus of Elasticity, MN.m/kg Tensile Index, N.m/g Burst index, kpa.m 2 /g Tear Index, mn.m 2 /g Stretch, % Opacity, % Air Resistance, s/100cm

22 Bleaching Process D HT (EP)DP A/PMo(EP)DP PMo(EP)DP Drainage Degree, ºSR PFI Revolutions Energy consumption, W.h Sheet Density, g/cm Bulk, cm 3 /g T.E.A., J/m Modulus of Elasticity, MN.m/kg Tensile Index, N.m/g Burst index, kpa.m 2 /g Tear Index, mn.m 2 /g Stretch, % Opacity, % Air Resistance, s/100cm

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24 Parameter Units Effluent D HT (EP)DP PMo(EP)DP A/PMo(EP)DP COD mg l kg odt BOD mg l kg odt BOD/COD Color mg l kg odt AOX mg l kg odt Acute toxicity % >100 >100 >100

25 COD, mg/l D HT (EP)DP P MopH3 (EP)DP A/P MopH4,5 (EP)DP Day

26 Parameter Units Effluent* D HT (EP)DP PMo(EP)DP A/PMo(EP)DP COD BOD Color AOX mg L a 164 a 178 a kg odt mg L a 112 a 107 a kg odt mg L c 180 b 154 a kg odt mg L b 0.7 a 0.7 a kg odt *Values in each row followed by the same letter are not statistically different, at a 5% level of significance.

27 Parameter Removal efficiency, % D HT (EP)DP PMo(EP)DP A/PMo(EP)DP COD BOD Color AOX

28 Optimum conditions to run the PMo stage include: kg/t Mo, ph 3 and temperature 85-95ºC; The A/P Mo (EP)DP sequence is the most cost-effective among the ones containing a PMo stage; The pulp bleached with the A/P Mo (EP)DP sequence showed poorer refinability and tearing strength than the reference, D HT (EP)DP, while that bleached with the P Mo (EP)DP sequence was similar to the reference;

29 Untreated effluents from the A/P Mo (EP)DP and P Mo (EP)DP sequences presented similar COD, but lower AOX and color than that from the D HT (EP)DP sequence. None of the effluents exhibited acute toxicity; The effluents from A/PMo(EP)DP, PMo(EP)DP and D HT (EP)DP sequences were readily treated in the bench-scale reactors, and achieved COD removal efficiencies of greater than 70%.

30 BLEACHING CONDITIONS BLEACHING STAGE D 0 A/D D HT D HT /Q Z/E (EP) D 1 (PO) P PMo Consistency, % 10 11/ /9 40/ Temp., C 60 95/ /90 50/ ; 95 Time. min / /30 1/ Pressure, kpa Kappa Factor (KF) / / End ph / / / ; 4.5 H 2 O 2, kg/odt Mo, kg/odt ClO 2 as Cl 2, Kg/odt KF KF KF KF O 3, kg/odt / DTPA, kg/odt /