Ozone in sequence and at different places as an interesting bleaching chemical for eucalyptus kraft pulp A. BURNET, B.BROCHIER, M. PETIT-CONIL May 28 th , 2015, Victoria
AGENDA • Motivation • Objective • Results • Influence of ozone during the last bleaching stage • New bleaching sequence • Conclusions
MOTIVATION • During the bleaching of kraft pulp, the last points of brightness are difficult to reach. • Envisaged solutions : To apply O 3 at the final stage: low chemical charge should be applied: the carbohydrates degradation To dissolve O 3 in water: it should facilitate its transfer to the active sites of the pulps at low consistency Easy implementation: no need for more equipment on the bleaching line than for a washing • At the last IPBC (2014), according to D. Lachenal & F.Pouyet, one promising approach was A(ZE)(ZE)(ZE) type of sequence: • At CTP, a ZEZEZE sequence was already tested « InTechFibres ’ property – do not divulgate » - ICEP 2015/ AB / May 28 th , 2015 3
AGENDA • Motivation • Objective • Results • Influence of ozone during the last bleaching stage • New bleaching sequence • Conclusions
OBJECTIVE • Improvement of the final pulp brightness : • Comparison between ozonated water & ozone gas • Substitution of the last P stage by a Z stage • Addition of a supplementary bleaching stage at the end of sequence • New bleaching sequence with successive bleaching stages • Influence of alkaline stage • Influence of ozone charge applied • Influence of pH 5
AGENDA • Motivation • Objective • Results • Influence of ozone during the last bleaching stage • New bleaching sequence • Conclusions
RAW MATERIAL & METHODS • Eucalyptus pulp after OQ(PO)D sequence Ozone effluent • Methods: Ozone absorbed (Dissolved + degraded) • Ozone gas: Reactor equipped with a vertical stirring [O 3 ]=100 mg/l Flow rate: 1l/min Consistency: 3.5% For test at 70°C: pre-heating of pulp Ozone introduced 7
RAW MATERIAL & METHODS • Ozonated water Production of dissolved ozone in the dissolving loop of bleaching pilot plant r 8
RAW MATERIAL & METHODS • Ozonated water Production of dissolved ozone in the dissolving loop of bleaching pilot plant [Dissolved ozone in water]: 80 mg/l Consistency: 3.5% 9
Use of ozone at the last bleaching stage Subtitution of P in (OQ(PO)DP) sequence by a Z stage • Z can substitute P stage: brightness OQ(PO)DP • Better efficiency of the dissolved O 3 / ozone gas • Only 0.05% of O 3 allowed obtaining brightness > 91% ISO • Whatever O 3 application, better results at ambient temperature 10
Use of ozone at the last bleaching stage Subtitution of P in (OQ(PO)DP) sequence by a Z stage • Substitution of P stage by Z stage (0.05%): similar DP • When Z > 0.05% : DP (due to carbonyl group formed during Z stage &/ or the presence of hexA) • Similar evolution of DP after O 3 gas & dissolved O 3 11
Use of ozone at the last bleaching stage Subtitution of P in (OQ(PO)DP) sequence by a Z stage PFI mill refining at ~40°SR 12
Use of ozone at the last bleaching stage Subtitution of P in (OQ(PO)DP) sequence by a Z stage PFI mill refining at ~40°SR • Z stage did not modify mechanical properties obtained after D 13
Use of ozone at the last bleaching stage Subtitution of P in (OQ(PO)DP) sequence by a Z stage PFI mill refining at ~40°SR • Z stage did not modify mechanical properties obtained after D • Dissolved O 3 & O 3 gas at 25°C : Similar mechanical properties 14
Use of ozone at the last bleaching stage Subtitution of P in (OQ(PO)DP) sequence by a Z stage PFI mill refining at ~40°SR • Z stage did not modify mechanical properties obtained after D • Dissolved O 3 & O 3 gas at 25°C : Similar mechanical properties • Substitution of P stage by Z stage: BL, burst & tear index 15
Use of ozone at the last bleaching stage Subtitution of P in (OQ(PO)DP) sequence by a Z stage • Similar COD after O 3 gas & dissolved O 3 at 25°C • Less COD was released after treatment with dissolved O 3 at 70°C lower brightness of pulp : maybe less lignin was released in effluents Degradation of components present in water 16
Use of ozone at the last bleaching stage Addition of a supplementary stage: OQ(PO)DPZ • Addition of a supplementary Z stage: brightness (>91.6% ISO) • O 3 gas was more efficient on the pulp previously bleached with P stage No influence of the temperature treatment with O 3 gas 17
Use of ozone at the last bleaching stage Addition of a supplementary stage: OQ(PO)DPZ • Addition of a supplementary Z stage DP • However, no modification of mechanical properties of the pulp 18
Use of ozone at the last bleaching stage Addition of a supplementary stage: OQ(PO)DPZ Lower COD was released after treatment with dissolved O 3 at 25°C lower brightness of pulp : maybe less lignin was released in effluents Degradation of components present in water with ozone 19
AGENDA • Motivation • Objective • Results • Influence of ozone during the last bleaching stage • New bleaching sequence • Conclusions
MATERIAL & METHODS Eucalyptus pulp Addition of dissolved O 3 in successive very short stages • Preparation of dissolved O 3 in the bleaching pilot • [dissolved O 3 in water]: 80 mg/l • Consistency: 3.5% • Neutral pH No E stage E stage (NaOH: 0.5%, 70°C, 1h) e stage (cold) O3 stage on pulp
New bleaching sequence • O 3 charge kappa number (-10 points) • Similar results whatever the bleaching sequence: Extraction stage (at hot or cold temperature) did not seem necessary 22
New bleaching sequence • Lignin elimination brightness (Correlation) • Similar results whatever the bleaching sequence pulp brightness (+ 20 % ISO) & kappa number (-10 points) 23
New bleaching sequence • kappa number pulp viscosity • E stage at 70°C had more negative impact on DP No necessary to perform Extraction stage 24
New bleaching sequence • After these successive Z stages, pulp brightness was too low for kappa number of 3 Chromophores formation brightness reversion could be occurred if carbonyl group generated during O 3 are not eliminated 25
New bleaching stage Influence of pH • For dissolved O 3 : The addition of acid improved the brightness results • For O 3 gas: pH of pulp did not modify the results 26
New bleaching stage Influence of pH • For dissolved O 3 : better delignification in acid conditions • For O 3 gas: pH of pulp did not have impact on delignification 27
New bleaching stage Influence of pH • More decrease in DP in acid medium: In acid medium, higher radical HO° are formed • In acid conditions, dissolved O 3 & O 3 gas: similar results 28
AGENDA • Motivation • Objective • Results • Influence of ozone during the last bleaching stage • New bleaching sequence • Conclusions
CONCLUSIONS • New bleaching sequence : • New bleaching sequence allowed decreasing the kappa number of pulp (-10 points) Pulp brightness (+20 points) • pH improved the pulp brightness However, these first conditions were not sufficient to obtain a high level of brightness • Optimization of conditions could improve these first results: • Addition of A stage before bleaching sequence It could reduce the cellulose degradation, deposits (calcium oxalate) & chemical consumption • Temperature to 70°C • to perform E stage with higher NaOH charge at 70°C, 1h • Washing after each ZE stages 30
CONCLUSIONS • Increase in final pulp brightness : • Substitution of P stage by a Z stage: • Only 0.05% of O 3 allowed obtaining brightness > 91%ISO • Better results with dissolved O 3 / O 3 gas • DP without consequence on pulp mechanical properties • Addition of a supplementary Z stage at the end of bleaching sequence: • brightness (>91.6% ISO) • O 3 gas was more efficient on the pulp previously bleached with P stage 31
Recommend
More recommend
