Ozone in sequence and at different places as an interesting - - PowerPoint PPT Presentation

Ozone in sequence and at different places as an interesting bleaching chemical for eucalyptus kraft pulp

• A. BURNET, B.BROCHIER, M. PETIT-CONIL

May 28th, 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 O3 at the final stage: low chemical charge should be applied:  the carbohydrates degradation  To dissolve O3 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,
• ne promising approach was A(ZE)(ZE)(ZE) type of sequence:
• At CTP, a ZEZEZE sequence was already tested

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« InTechFibres’ property – do not divulgate » - ICEP 2015/ AB / May 28th, 2015

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

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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
• Methods:
• Ozone gas:

 Reactor equipped with a vertical

stirring

 [O3]=100 mg/l  Flow rate: 1l/min  Consistency: 3.5%  For test at 70°C: pre-heating of pulp

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Ozone introduced Ozone absorbed (Dissolved + degraded) Ozone effluent

RAW MATERIAL & METHODS

• Ozonated water

 Production of dissolved ozone in the dissolving loop of bleaching pilot plant

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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%

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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

• Better efficiency of the dissolved O3/ ozone gas
• Only 0.05% of O3 allowed obtaining brightness > 91% ISO
• Whatever O3 application, better results at ambient temperature

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OQ(PO)DP

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 O3 gas & dissolved O3

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PFI mill refining at ~40°SR

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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

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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 O3 & O3 gas at 25°C : Similar mechanical properties

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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 O3 & O3 gas at 25°C : Similar mechanical properties
• Substitution of P stage by Z stage: BL, burst &  tear index

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Use of ozone at the last bleaching stage

Subtitution of P in (OQ(PO)DP) sequence by a Z stage

• Similar COD after O3 gas & dissolved O3 at 25°C
• Less COD was released after treatment with dissolved O3 at 70°C

lower brightness of pulp : maybe less lignin was released in effluents Degradation of components present in water

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Use of ozone at the last bleaching stage

Subtitution of P in (OQ(PO)DP) sequence by a Z stage

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)
• O3 gas was more efficient on the pulp previously bleached with

P stage

No influence of the temperature treatment with O3 gas

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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

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Use of ozone at the last bleaching stage

Addition of a supplementary stage: OQ(PO)DPZ

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Lower COD was released after treatment with dissolved O3 at 25°C

lower brightness of pulp : maybe less lignin was released in effluents Degradation of components present in water with ozone

AGENDA

• Motivation
• Objective
• Results
• Influence of ozone during the last bleaching stage
• New bleaching sequence
• Conclusions

MATERIAL & METHODS

Eucalyptus pulp Addition of dissolved O3 in successive very short stages

• Preparation of dissolved O3 in the bleaching pilot
• [dissolved O3 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

•  O3 charge kappa number (-10 points)
• Similar results whatever the bleaching sequence:

 Extraction stage (at hot or cold temperature) did not seem necessary

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New bleaching sequence

• Lignin elimination  brightness (Correlation)
• Similar results whatever the bleaching sequence

pulp brightness (+ 20 % ISO) &  kappa number (-10 points)

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New bleaching sequence

•  kappa number   pulp viscosity
• E stage at 70°C had more negative impact on DP

No necessary to perform Extraction stage

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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 O3 are not eliminated

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• For dissolved O3: The addition of acid improved the

brightness results

• For O3 gas: pH of pulp did not modify the results

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New bleaching stage

Influence of pH

• For dissolved O3: better delignification in acid conditions
• For O3 gas: pH of pulp did not have impact on delignification

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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 O3 & O3 gas: similar results

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New bleaching stage

Influence of pH

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

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CONCLUSIONS

• Increase in final pulp brightness :
• Substitution of P stage by a Z stage:
• Only 0.05% of O3 allowed obtaining brightness > 91%ISO
• Better results with dissolved O3 / O3 gas
•  DP without consequence on pulp mechanical properties
• Addition of a supplementary Z stage at the end of bleaching

sequence:

•  brightness (>91.6% ISO)
• O3 gas was more efficient on the pulp previously bleached with

P stage

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