COMPARISON OF DIP BLEACHABILITY BETWEEN TRADITIONAL SOAP AND REDUCED - - PowerPoint PPT Presentation

COMPARISON OF DIP BLEACHABILITY BETWEEN TRADITIONAL SOAP AND REDUCED ALKALINE CHEMISTRIES

Sari Vahlroos, Kemira, Oulu Research Centre, Finland Mika Körkkö, University of Oulu, Finland Scott Rosencrance, Kemira, Marietta, USA Jouko Niinimäki, University of Oulu, Finland

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Introduction

lower total chemical cost improved stickies control ability to remove alkaline sensitive printing inks, like flexo. reduced ink removal efficiency increased ink fragmentation the lack of ink release yield

REDUCED ALKALINE / NEUTRAL DEINKING

Profitability Environmental safety Continuous improvement in quality Debasement of the raw material quality

lower COD release

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Objective of the study

• To evaluate the bleaching

performance for pulps produced via both a reduced alkaline chemistry and a traditional alkaline chemistry.

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Experimental Papers & deinking chemicals

• The furnish composition used in this study consisted of 50% of newspapers

(ONP) and 50% of magazines (OMG). The OMG paper was 50% SC (super calandered) and 50% LWC (light weight coated)

Alkaline soap chemistry Reduced alkaline Lionsurf chemistry Sodium hydroxide 10

• Sodium silicate

10 10 Soap 5

• Hydrogen peroxide

6

• Lionsurf 305
• 0.75

Lionsurf 564

• 0.75

Deinking chemical dosages, kg/t

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Alkaline soap chemistry Reduced alkaline Lionsurf chemistry Hydrogen peroxide 20 20 Sodium hydroxide 3 4 Sodium silicate 10 10 Bleaching chemical dosages, kg/t

Dithionite bleaching: pH 7 Dosage 8 kg/t

• Alkaline or reduced alkaline deinked pulp was bleached with peroxide and

dithionite (P+Y).

Experimental Bleaching chemicals

Peroxide bleaching

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Experimental Deinking; pilot equipment

pulp tank

• np

Pulper Flotation Wire press water tank

Sample point

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Experimental Deinking; pilot equipments

pulp tank Pulper Flotation Wire press water tank

20 minutes 16% consistency batches of 33 kg of o.d. pulp. 45°C temperature

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Experimental Deinking; pilot equipments

pulp tank

• np

Pulper Flotation Wire press water tank

Diluted to 2% consistency with equilibrated process water Pumped through a screen basket with perforation of 1.5 mm. Following screening, the consistency was adjusted to 1% in preparation to feed the flotation stage.

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Experimental Deinking; pilot equipments

pulp tank

• np

Pulper Flotation Wire press water tank

The flotation cell is a model of Metso and consists of four sectors. The air flow to flotation was 80 L/min which resulted in an air/stock ratio of 110%. The reject were pressed and the filtrate was circulated back to process

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Experimental Deinking; pilot equipments

pulp tank

• np

Pulper Flotation Wire press water tank

The accepts of flotation were sent to a wire

• press. After the wire press, the consistency of

the pulp was about 20%. This stock was then utilized for laboratory scale bleaching studies.

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• The carryover of residual peroxide was

prevented by dilution and thickening back to 4% consistency prior to dithionite bleaching

Experimental Lab bleaching

• The peroxide post-bleaching was

performed at 90°C, for 40 min and at 10% consistency.

• The dithionite bleaching was performed at

60°C, for 30 min and at 4% consistency.

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Results Deinking Yield and TOC

• The flotation pH with alkaline and reduced alkaline chemistry was 9.0 and 8.0,

respectively.

Yield over flotation, % Alkaline soap chemistry 82.2 Reduced alkaline Lionsurf chemistry 83.1

100 200 300 400 500 600 TOC, mg/l

Alkaline deinking Reduced alkaline deinking

An equally long trial and the same water consumption gave almost double the Total Organic Carbon (TOC) load for alkaline deinking than reduced alkaline deinking.

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Results Deinking Brightness

45 50 55 60 65 70 Flotation feed Flotation accept Wire press outlet

Brightness, ISO%

Alkaline Reduced alkaline alkaline reduced alkaline 4 ISO%

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Results Deinking Ink removal

200 400 600 800 1000 1200 Flotation feed Flotation accept Wire press outlet

Residual ink, ppm

Alkaline Reduced alkaline alkaline reduced alkaline

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Results Deinking b*-value

1 2 3 4 5 Flotation feed Flotation accept Wire press outlet b* C/2 Alkaline Reduced alkaline

Ink and ash removing ash removing

+ b = yellow

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Results Bleaching Peroxide

0.2 0.4 0.6 0.8 1 1.2 1.4 Alkaline deinking + bleaching Reduced alkaline deinking + bleaching NaOH dosage, %

pulping bleaching bleaching

Intial pH Final pH Residual peroxide

in peroxide bleaching in peroxide bleaching

% of the dosage Alkaline 10 8.9 44 Reduced alkaline 10 7.6 55

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Results Bleaching Brightness

56 58 60 62 64 66 68 70 Wire press outlet peroxide bleached peroxide + dithionite bleached

Brightness, ISO%

Alkaline Reduced alkaline alkaline reduced alkaline

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Conclusions

• Monitoring through the whole process is very important when reduced alkaline

chemistry is compared to the alkaline chemistry: Waters:

• Lower TOC-load

Deinking:

• Equal ink removal

Bleaching: more responsive to the post-bleaching chemicals because peroxide was not used in pulper.

Post-bleaching the pulps, obtained from both a traditional alkaline process and a reduced alkaline process resulted in the same residual ink and brightness values.