The AlphaCarb process

Transcription

1 The AlphaCarb process AlphaCarb A process for the reutilization of coating pigments and fillers for paper and cardboard coating technology. This process has been protected worldwide by patent-right claims. Alpha Calcit Füllstoff Gesellschaft mbh & Co. KG D Köln PO-BOX Phone: +49 (0) info@alpha-calcit.de D Köln Otto-Hahn-Str. 9 Fax: +49 (0) Internet AlphaCarb Presentation 9 Version 1.1

2 The AlphaCarb Process A new technology optimising economics and ecology of paper and cardboard coating Introduction: Moving targets as the protection of the environment, the pressure to reduce costs and the continuous improvement of the paper quality indicated the development of a new process becoming part of paper and cardboard coating. Current situation: In the coating plants large amounts of coating colours as well as coating colour components are currently lost during coating colour preparation, at the coaters and during storage due to reasons like changes in paper quality, cleaning operations and standstills. Such losses, named "coating colour rejects", add up to 4 to 11 % of solids, in most cases between 7 and 8 % of solids based on the total tonnage of coating colours produced. In addition, there are further amounts of cleaner rejects. Futural Situation: When using the AlphaCarb technology, such valuable amounts of raw materials have no longer to be dumped and lost, but are re-used by 100 % in paper coating via the AlphaCarb process. How does this new process look alike? In the AlphaCarb process, pigment slurries based on calcium carbonate, talc or china clay will be totally or at least partially self-produced in the coating colour preparation department within the paper plant. The AlphaCarb CRT process as well as the AlphaCarb CCT process are available. CRT stands for Cleaner Reject Technology, CCT stands for Coating Colour Technology. Cleaner rejects are grinded using AlphaCarb CRT technology. To manoeuvre to re-work the total amount of cleaner rejects created at a given plant location, in almost all cases the capacity of just one grinding unit is more than convenient. The so produced fine particle-sized mineral filler is used in the pulp instead of standard filler as purchased. Coating colour containing waters are separately form other waste waters collected and are continuously fed to the AlphaCarb CCT process. Due to the fact that, on the one hand, coating colour containing waters are generated with very high dilution having solids contents of not more than 1 % by weight, but, on the other hand, almost the total solids content of all coating colour containing waste waters shall be recycled in the new process, the coating colour containing waste waters have to be dewatered to a solids content of constantly between 20 and 30 % by weight. To do so, all solids of the coating colour containing waste waters, pigment as well as binder, are quantitatively separated in a first step using cationic flocculation agent CALCIFLOC which has AlphaCarb Process E Page 1 of 13

3 been especially developed for the AlphaCarb process. In a second step, such separated solids are dewatered to the solids content as desired. Decanter technology has proven itself to be the optimum regarding technology for this process step to dewater the corresponding waste waters. A typical example of a solids and water balance in the AlphaCarb process shall be illustrated here as follows: Coating pigment: Consumption for pre-coat 120 t/day 60 quality (dry) Consumption for top-coat 60 t/day 90 quality (dry) + 60 t/day china clay (dry) Material losses at coater: Target: 3 sheet breaks per day of 2,5 t solids each => 150 t 5% reject ( 3 % losses) Total re-use in the coating colour cycle in the AlphaCarb process In combination with the flocculation agent CALCIFLOC the decanter provides a total separation of solids from waste water and so allows the increase in solids concentration as desired without any problems. The total amount of solids as pigments, binders, etc. is gained back. Page 2 of 13

4 The solids/water balance of the grinding of fresh calcium carbonate together with rejects to pigment slurry with a solids content of 75 % is as follows: Rejects amount Concentration Treatment Slurry Rejects per day Solids Water Waste water per day Grinding fresh carbonate to 75 % solids slurry per day 150 t 5 % Decanter with CALCIFLOC 25 t 30 % 7,5 t 17,5 t 125 t clear 45 t powder With the help of the decanter technology excellent solids contents are achieved. Typically, rejects with up to 30 % solids content are realised. This is the reason why the amounts of fresh carbonate needed for the grinding process are much lower and have in this example only to be a little more than 40 % of the total usage of pre-coat carbonate. The waste water coming out of the decanter is clear. After having defined the size of the decanter needed based on the figures of the solids/water balance, the grinding system being a corresponding satellite plant to be installed next to the decanter to manufacture the pigment slurry is designed. This grinding system consists of grinders which are specifically designed for the new process. The grinding system is fully integrated into the existing coating colour preparation plant. The installation of an AlphaCarb System grinding plant needs between 50 and 200 m² of space depending on the tonnage per year including the silo for dry powdered pigment used as raw material. For an AlphaCarb CRT plant, between 10 and 50 m² of space are convenient. The AlphaCarb System grinding plant (as satellite plant in a paper or cardboard plant) Rejects originated from the coating process and the cleaner coming from the decanter Silo for powder Storage of pigment powder (silo) Reception tank Grinder I Grinder II Transfer tank Coating colour preparation or mixing department Seite 6 von 13 Page 3 of 13

5 The production process flow in the AlphaCarb CCT process is as follows: - dry delivery of the pigment as needed, e.g. calcium carbonate, in form of powdered material having a particle size of about 30 % below 2 µm, Alpha-System grinding plant New installation Available at customer s plant Storage tanks for slurry Silo for powder 30% below 2 micron AlphaCarb System grinding equipment Rejects 60% below 2 micron (pulp) 75% below 2 micron (coating) 90% below 2 micron (coating) Delivery of powdered pigment Storage of powder Wet grinding Dispersing to paper machine to coating colour preparation - dispersing the desired powdered pigments together with the recycled coating colours being dewatered in the decanter to solids contents of 75 to 80 % by weight. The innovative and value-adding part of the process is the fact to recycle the rejects which are currently lost and to use them as medium for the pigment dispersion - optimising the pigment slurry properties like viscosity, anti-sedimentation behaviour by adding the special dispersing aid CALCILAN which has been developed to be used in the AlphaCarb process - wet grinding of the desired pigment to well-defined fine particle-sized pigment qualities, like calcium carbonate slurries "60 % below 2 µm" or "90 % below 2 µm", or to any other pigment quality as desired which can be almost freely defined - running of the AlphaCarb System grinding plant is fully automatic for 365 days per year. Very limited line management is easily done by the existing crew of the coating colour preparation plant. No additional personnel is needed to run the AlphaCarb process. Due to the fact that the delivery of the total system is done by Alpha, the user is independent of external pigment slurry deliveries - modular design and construction of the AlphaCarb System grinding plant is at any time open to install additional production capacities and/or to implement any changes in material flow. The pigments manufactured in the AlphaCarb process can be used in pre-coat and/or top-coat. Page 4 of 13

6 Which is the new role of the user in this new process? The new process defines a new role for the user: TRADITIONAL PROCESS AlphaCarb - PROCESS RAW MATERIAL DEPOSIT Mining Wet grinding to final pigment product Fineness: % < 2 µm Storage of slurry (75% of pigment) Transport of slurry Water content: 25% Dry grinding to achieve coarse pre-product PAPER MANUFACTURING PLANT Storage of slurry (75% of pigment) Preparation of coating colour Application of coating colour Creation of high-cost residues which currently are disposed COATED PAPER Quality : Standard Fresh water for wet grinding Preservatives Bacterizides 25% more transportation volume due to the fact that 25% water content have to be transported in addition. In total that means truck loads p.a. just in Germany. Preservatives Bacterizides Waste water Waste disposal Downcycling to low-value filler RAW MATERIAL DEPOSIT Mining Dry grinding to powder preproduct Fineness: 30% < 2 µm Storage powder pre-product Transport of powder ( = 100% pre-product) PAPER MANUFACTURING PLANT Storage of powder pre-product Wet grinding to final pigment Fineness: % < 2 µm Preparation of coating colour Application of coating colour Creation of high-value residues Re-using of such residues COATED PAPER Most properties show quality improvements compared to standard no preservatives and bacterizides Much lower volume to be transported, because water content of 25% is avoided. This leads to truck loads less just in Germany and so is environmentally and cost friendly. no preservatives and bacterizides Waste water and residues are re-used environmentally friendly in wet grinding of preproduct to pigment. No residues are wasted! Increased dry pick strength Higher paper gloss Improved print uniformity 06/2001 Legend Green:beneficial, economical and environmentally friendly Red: disadvantageous, non-economical and environmentally unfriendly 06/2001 Legend Green:beneficial, economical and environmentally friendly Red: disadvantageous, non-economical and environmentally unfriendly In future, the user produces "his" pigment slurry or at least parts of his demand on-site by himself. This enables the user to get the full benefit to influence the properties of the coating pigment. For example, a 60 % below 2 µm quality for pre-coating can be targeted at exactly any point between 55 and 65. This helps to compensate slight deviations currently occurring in the coating process or it enables the user to spontaneously fulfil specific requirements, an option which is definitely not given as long as standard pigment qualities as currently delivered in form of standard pigment slurries have to be used. Which environmental benefits does this new process offer? By using the new technology, the user favourably effects the environment: - transportation volume is reduced by 25 % when changing from pigment slurry transportation to transportation of pigment in powdered form, - recycling of 100 % of the rejects into the wet grinding process relieves the strain on sewage plants and landfills Page 5 of 13

7 Which economical benefits does this new process offer? The user saves money: - high-value coating colour containing parts of the rejects are put back into the coating process and are no longer financial losses, - costs of disposal on the landfill or for the waste water treatment are reduced. Such costs will further increase drastically with upcoming changes in the corresponding laws in some areas in 2005 already, - transportation costs can be cut by approximately 25 % due to the fact that no water has to be transported as it is currently practiced if pigment slurries are used. Saving potential AlphaCarb procedure Category Kind of saving Amount based on total savings 1) Cost for after treatment and waste disposal (landfill) 38 % 2) Transportation costs (Powder instead of slurry) 10 % 3) Raw material cost (recycling of coating colors) 27 % 4) Raw material cost (recycling of cleaner reject) 19 % 5) Raw material cost (production of slurry in-house) 6 % Comment: This evaluation is based on the average values of 10 typical case studies. An individual investigation of the saving potential results for each client in a specific amount of percentages based on the total saving. The absolute saving potential, in per year, can be achieved and visualized relatively easily by using an individual investigation called feasibility study % 27% 6% 10% 38% Seite 11 von 13 All profitability calculations carried out up to now showed savings in these areas, which add up in each individual case to millions of Euro. Page 6 of 13

8 Which technical benefits does this new process offer? Compared with the usage of conventional slurries, the AlphaCarb process leads to several outstanding technical benefits, mainly an improvement in printability as well as optical properties. - lower need of binder / higher pick resistance - higher print gloss (especially for matte papers) - lower tendency of mottling, but - lower water vapour transition (blistering) in case that the lower amount of binder needed is taken care of by using less binder or a porous binder. Further technical benefits are: - improved coating colour conditioning and in consequence: - higher opacity - better gloss of the paper coat and, regarding runnability AlphaCarb offers a higher safety margin in pre-coating and is less sensitive against blade streaks in top-coating. This is mainly due to specific grinding beads as used in the AlphaCarb process. Whereas standard grinding beads break after a relatively short period of time, the specific grinding beads show wear on the surface, but they do not break. Comparison of Grinding Beads Usual grinding beads after use: clear deviations from spherical form, inhomogeneity in the form of dark inclusions becomes visible, sharp breaking edges, parts of beads missing AlphaCarb grinding beads after use: still in ideally spherical shape Page 7 of 13

9 Comparison of coatings Traditional Coating - thin covering layer, poor of binder - coating - migration of binder into base paper - base paper Properties of traditional coating: - pick resistance lower - print gloss lower - mottling tendency higher - porosity higher AlphaCarb Coating - coating of binder fixed on the pigment particles without penetration into base paper - base paper Properties of the AlphaCarb coating: - pick resistence higher - print gloss higher - mottling tendency lower - porosity lower The following two pages shall visualize the excellent quality of coatings which are the result of the use of the AlphaCarb process. For direct comparison, in both cases combinations of pre-coat and top-coat based on coating colours are shown which have been manufactured on the one hand using standard calcium carbonate slurries and on the other hand in the AlphaCarb process. The first picture shows a standard coating as currently produced in the paper industry by purchasing 60 % below 2 µm calcium carbonate slurry for the pre-coat and purchasing 90 % below 2 µm calcium carbonate slurry for the top-coat. The second picture shows the coating which resulted under identical circumstances when using the corresponding pigment slurries manufactured in the AlphaCarb process. The new process is able to guarantee steep particle size distributions as requested by the market in form of CC qualities. Page 8 of 13

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12 In the meantime, the potential of re-gained coating colour wastes regarding binder recovery has been detected by doing trials. The result of such trials is herewith brought to your attention. It has been proven that amounts of binder which are contained in the coating colour wastes are not only not down-cycled in the AlphaCarb process, but are re-gained by 100 %. Corresponding trials have been carried out by grinding precipitated coating colour waste together with fresh calcium carbonate in the AlphaCarb process not adding any fresh binder. The pigment slurry gained by doing so was applied as pre-coat on standard raw paper, and, to be honest, for this trial without adding any further binder or additives as it is usually done when preparing a pre-coating colour. The following picture visualizes very clearly the outstanding quality of pigment slurries manufactured in the AlphaCarb process. Sample A represents the result of pigment slurry manufactured in the AlphaCarb process. Such pigment slurry was used in the standard formulation for the preparation of coating colour without compensation for the relatively higher amount of binder created by recycling binder in the new process. The optimisation compared to the sample C which was manufactured using purchased standard pigment slurry can be easily detected. Sample B resulted in the use of pigment slurry manufactured in the AlphaCarb process used directly as coating colour without any addition of binder. A real adhesion to the raw paper was detected which proofs that binder is recycled in the AlphaCarb process. Clearly detected was a real adhesion to the raw paper with all the benefits as usually given by this effect. The resulting bonding strength was for sure not as high as usual. This can easily been explained by the fact that the amount of binder as delivered from the recycling waste before grinding was just smaller than the standard amount of binder as usually used. Positively surprising is the fact that even when checking for the pick resistance good results were achieved. Page 11 of 13

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14 To test the process in practice, a mobile AlphaCarb satellite grinding plant having a scale of 1:5 and a production capacity of 25 t/day 60 or 15 t/day 90 finenesse as available for trials and tests on-site at interested parties. Which references do exist for this new process? It seems to be reasonable that existing and interested users of the new process do not like to put their cards open on the table due to the fact that they do receive a temporary differentiation potential and the mentioned benefits. We are more than prepared to fulfil your requirement to get into direct contact with individual parties using the process. But you have to be aware that we have to check the possibilities in each individual case with the corresponding user. Summary: The AlphaCarb process relieves the strain on the environment, delivers higher-value coating pigments, offers incredible saving potentials and improved surface properties. Outlook: We are keen that AlphaCarb is a future-oriented technology and we would like to give answers to all kind of upcoming questions in detail. Page 13 of 13