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De-inking Overview. What is Deinking? What is Deinking? The removal of ink from a fibre slurry by a combination of Chemical and Mechanical methods De-inking.

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Presentation on theme: "De-inking Overview. What is Deinking? What is Deinking? The removal of ink from a fibre slurry by a combination of Chemical and Mechanical methods De-inking."— Presentation transcript:

1 De-inking Overview

2 What is Deinking? What is Deinking? The removal of ink from a fibre slurry by a combination of Chemical and Mechanical methods De-inking Overview

3 Chemical Methods of Removing Inks Pulping with caustic, silicate, peroxide, fatty acid/soap and or surfactant Wash De-inking with surfactant/dispersant Flotation De-inking with Fatty Acid/Surfactant De-inking Overview

4 Mechanical Methods of Removing Inks Six Methods for removing or changing inks and contaminants WashingFlotationCleanersScreensKneading/DispersionClarification

5 Deinking Overview - Process

6 Pulping - What does it do? Defibering Ink Release Break down of ink particle size De-inking Overview

7 Pulping Chemistry - Basics Caustic: Swells fiber to allow rapid defibering Peroxide: Prevents alkali yellowing of fibers Silicate: Stabilizes peroxide and adds alkalinity DTPA: Chelates metal ions for peroxide efficiency Fatty Acid/Soap: Aids ink detachment and ink agglomeration Surfactant: Aids ink detachment and ink dispersion De-inking Overview

8 PULPER PERFORMANCE - Ink Breakdown # of Particles Particle Size (Microns) De-inking Overview Ideal Size for Flotation Flotation Too large to float Too small to Float

9 Deinking Overview

10 Surfactant Action in Pulping Surfactants in the pulper will increase the ink detachment efficiency. Its high detergency means that it will compensate for some of the caustics mode of action and a decrease in caustic is therefore possible. Any decrease in caustic will be followed by a decrease in peroxide,therefore the overall chemical demand is lower. De-inking Overview

11 Common De-inking chemicals *Sodium Hydroxide *Sodium Silicate *Hydrogen Peroxide *Chelants *Fatty Acids/Soaps *Surfactants De-inking Overview

12 Common De-inking Chemicals Typical Dosages *Sodium Hydroxide - Woodfree - 0.3% - 0.8% on fibre ONP/OMG - 0.2% - 0.5% on fibre ONP/OMG - 0.2% - 0.5% on fibre *Sodium Silicate - 0.8% - 2% on fibre *Hydrogen Peroxide - 0.2% - 0.6% on fibre *Fatty acids - 0.1% - 0.6% on fibre *Surfactants % - 0.1%on fibre De-inking Overview

13 De-inking chemicals Advantages and Disadvantages Chemical AdvantageDisadvantage Sodium hydroxide Wetting, fibre swellingDispersive action, Ink release, neutralisationfiller release, fibre Ink release, neutralisationfiller release, fibre of fatty acid, polymers etcyellowing, saponfication of fatty acid, polymers etcyellowing, saponfication of hot melts etc Sodium Silicate Wetting, buffering, alkalinityDispersive action, colloid peroxide stabilisationstabilisation peroxide stabilisationstabilisation De-inking Overview

14 Chemical AdvantageDisadvantage Fatty Acid Rapid efficient removal ofwater hardness dependent ink, fewer dispersed inkshigh dose rates, low foam ink, fewer dispersed inkshigh dose rates, low foam high brightness, in flotation, make down high brightness, in flotation, make down low cost per kg systems, safety concerns low cost per kg systems, safety concerns Surfactant more efficient ink removalpotential ink carryover, improved washing, lowover dispersion of ink, improved washing, lowover dispersion of ink, dose rates, independent build up in water. dose rates, independent build up in water. of water hardness, of water hardness, high brightness high brightness De-inking Overview

15 Advantages of Using Blended/Combinations of products *Excellent ink removal *Good washing *Less deposition on PM *Lower total chemical demand (e.g.. NaOH, H2O2 etc.) *Low dependence on water hardness *low dosages / cost effective *100% liquid handling if required *On-site optimisation easy De-inking Overview

16 De-inking Product Definitions Surfactant = Surface active Agent Associates with Ink, Dirt and Oil in the pulper. Effectively acts as a cleaning agent to remove Ink from the fibre. Reduces surface tension in stock to give more foam. Can be used to control foam in Flotation De-inking Overview

17 Fatty Acid/Soap= Collector chemical De-inking Product Definitions Liquid Fatty acid is neutralised in the pulper to produce the sodium soap. Converted to Calcium Soap in flotation. (Sometimes supplied as solid sodium soap) Agglomerates ink particles freed in pulping and attaches the ink to the bubbles that are removed in flotation. De-inking Overview

18 Fatty Acid Collector - Mechanism De-inking Overview

19 Fatty Acid Soap - Collector Mechanism NO HYDROPHILIC HEADSCOAGULATED INK AIR BUBBLE + De-inking Overview

20 De-inking Chemicals Selection Parameters The choice of chemicals depends on:- *Type of incoming furnish and process equipment *Types of inks and binders used in these inks *Amount of coatings present *Amount of Calcium available in the water *Operational conditions and final product specifications De-inking Overview

21 Mechanical Methods of Removing Inks Six Methods for removing or changing inks and contaminants WashingFlotationCleanersScreensKneading/DispersionClarification De-inking Overview

22 Washing Most effective on inks microns in size. Washes away fine inks that flotation cannot remove. Any thickening stage (disc filters, drum thickeners etc) will help to wash fine inks out of the system De-inking Overview

23 Flotation Most effective removal at particle sizes microns Air bubbles floated up through the fiber slurry Ink particles attach to the bubbles and are removed Heterogenous bubbles are best for efficient in removal (I.e. larger surface area for ink to attach to) De-inking Overview

24

25 Typical Flotation Performance ONP/OMG Brightness gain points typical Dependent upon:- Retention time OMG level ConsistencyWoodfree/MOW Ink removal 85-95% typical Dependent upon:- FurnishPulping Retention time Consistency Addition point De-inking Overview

26 Kneader/Disperser Reduces particle sizes of inks (Essential for Laser inks) to correct size for flotation Load on kneader determines particle reduction efficiency Temperature is critical to performance De-inking Overview

27 Typical Performance Measurements Image Analysis (Woodfree) - Dirt Count, speck size distribution ERIC (ONP) - Effective Residual Ink Concentration Brightness -UV+, UV- (R457) De-inking Overview

28 IMAGE ANALYSIS Image analysis is used to determine the removal efficiencies of a WF deinking plant. It measures ink specks in the visible range and is an excellent way of determining flotation and kneader/disperser efficiencies. De-inking Overview

29 Commercial Deinking - Historical Developments 1. Fatty AcidTallow based fatty acids have dominated the industry /Soapsfrom the beginning and still maintain a strong position /Soapsfrom the beginning and still maintain a strong position especially in Europe. (Stephensons, FINA, Eka, Nopco) 2. Surfactants:-Surfactant only systems were introduced in These had limited success. Although dominant in Japan it was rejected in Europe and only had limited success in North America. 3. Fatty Acid/Surfactant Blends:- Blend technology was commercialised in Therefore Tallow FA’s were no longer dominant and were replaced by other fatty acid/surfactant combinations in North America. De-inking Overview

30 Troubleshooting - FOAM Factors influencing foam production 1.pH.OH from caustic stabilises foam 2.TemperatureSurfactants are temperature dependent 3.Ash contentThe higher the ash content the higher the foam volume. 4.Furnish typeHigher coating content gives more foam 5.CalciumTypically need > 150ppm to get a good foam if using fatty acid/soap 6.De-inking agents Choice of product will determine foam level De-inking Overview

31 Troubleshooting - Foam 1. Too little foam a) Check pH. Generally if pH is lower than 7.5 there will be little or no foam. An increase in caustic in pulper little or no foam. An increase in caustic in pulper or flotation will help to increase foam. or flotation will help to increase foam. b) Check temp. If the temperature is above the cloud point of the surfactant being used then there will be no foam. surfactant being used then there will be no foam. c) Check dosageA small increase in de-inking chemical dosage will give more foam (economically) d) FurnishLow quantity or poor quality magazine content will reduce foam volume. An increase in the amount of magazine or office waste will increase foam (expensive) De-inking Overview

32 Troubleshooting - Foam 1. Too much foam a) Check pH. A reduction in caustic will help to reduce foam levels. b) Check temp. Increasing the temperature to slightly above the cloud point of the surfactant will help to reduce foam. c) Check dosageA decrease in de-inking chemical dosage will give less foam d) FurnishReduce level of magazine or office waste to reduce foam. e) ChemicallyA small addition of a foam control agent can be used economically to reduce foam. De-inking Overview

33 Troubleshooting - Quality Brightness too lowEither the ink is not being removed in pulping or not being collected in flotation. An increase in the level of surfactant will help to detach more ink from the fibre. However, the foam will need to be controlled. An increase in the fatty acid dosage will help to collect the ink better in flotation. NB.Overdosing surfactant will result in dispersion of the ink into fine particles which will not be removed in flotation and will remain in the water system, causing quality problems (loss of brightness). De-inking Overview

34 Brightness too lowOverdosing caustic will lead to yellowing of the fibre and therefore lower brightness. Underdosing peroxide will lead to low bleaching efficiency (caustic yellowing overrides the bleaching). Therefore lower brightness. Calcium content could be too low, therefore decreasing efficiency of fatty acid collector. Calcium Hydroxide or chloride can be added to raise the level of calcium in system. Increasing the office waste can also increase calcium level. Plus background brightness of furnish will be higher. Troubleshooting - Quality De-inking Overview

35 Brightness too lowNew products are available to increase bleaching efficiency. Generally adjusting the chemicals is more cost effective than increasing the office waste furnish. Troubleshooting - Quality De-inking Overview


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