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EP4536599A1 - Procédé de traitement de boues d'usine de papier ou de carton pour réutilisation - Google Patents

Procédé de traitement de boues d'usine de papier ou de carton pour réutilisation

Info

Publication number
EP4536599A1
EP4536599A1 EP22945327.9A EP22945327A EP4536599A1 EP 4536599 A1 EP4536599 A1 EP 4536599A1 EP 22945327 A EP22945327 A EP 22945327A EP 4536599 A1 EP4536599 A1 EP 4536599A1
Authority
EP
European Patent Office
Prior art keywords
sludge
cationic polymer
paper
pulp
conditioned
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22945327.9A
Other languages
German (de)
English (en)
Inventor
Peng Zhou
Sari KRAPU
Suhua WU
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kemira Oyj
Original Assignee
Kemira Oyj
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kemira Oyj filed Critical Kemira Oyj
Publication of EP4536599A1 publication Critical patent/EP4536599A1/fr
Pending legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
    • C02F11/147—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using organic substances
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
    • C02F1/56—Macromolecular compounds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
    • D21C5/02—Working-up waste paper
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/01—Waste products, e.g. sludge
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
    • C02F11/127—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering by centrifugation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F2001/007—Processes including a sedimentation step
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/26—Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof
    • C02F2103/28—Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof from the paper or cellulose industry
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/04—Flow arrangements
    • C02F2301/046—Recirculation with an external loop
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/04—Disinfection

Definitions

  • the present disclosure generally relates to treating sludges removed from paper or board production, such as recycled fibre (RCF) production.
  • the disclosure relates a method for treating said sludge in order to improve reusability thereof, particularly, though not exclusively as conditioned sludge in said paper or board production processes.
  • RCF recycled fibre
  • Papermaking processes involve large amount of water and aqueous media. Water is employed as carrier and matrix to aid forming the pulp into continuously moving wet mat of fibre.
  • the modern processes aim at minimizing both fresh-water consumption and production of aqueous effluents, and wastewaters to be treated i.e. sludges.
  • aqueous effluents are constantly removed from paper or board production. With said aqueous effluents, a variety water of soluble and/or water immersible substances and solids are removed as well.
  • Substances and solids not retained in the cellulosic fibre web comprise organic, inorganic and microbiological material. They originate from the fibre source, either virgin or recycled, from additives fed to the process and from the process itself, namely side reactions and microbial growth in this nutrient rich aqueous environment. They are not bound to the cellulosic fibre web mainly because of their size, but also due to their shape or charge.
  • Recycling untreated sludge back to the papermaking may lead to technical challenges in the machine runnability, such as to deteriorated drainage and retention, bringing bacteria (back) to the system and/or worsening of wet end.
  • Inorganic micro-particles and fines typically cause poor drainage leading to speed decline, vacuum load and vapor consumption rise. Further, when micro-particles and fines cannot retain in the cellulosic fibre web, the system becomes dirty.
  • the finished paper/board product obtained thereof may have deteriorated quality, such as weaker strength caused by inorganic content from the recycled sludge impeding the inter-fibre bonding. In the products, this can also be seen as dusting and fluffing and as need for more dry strength agent.
  • a method for producing conditioned sludge comprises obtaining a sludge from a paper or board mill and treating said sludge with addition of at least a first cationic polymer to obtain a conditioned sludge.
  • the present method has shown to provide advantages for both the paper and/or board-making process, and additionally to the wastewater treatment.
  • solid material from the sludges can be recovered, and recycled back to the papermaking processes as flocs in size and shape suitable to be retained in the cellulosic fibre webs.
  • the embodiments of the method have proven to provide further advantages for the papermaking process and products thereof.
  • a use of conditioned sludge obtained by a method of the present invention in a paper or board mill provides advantages for both the papermaking process and products thereof, as well as to the wastewater treatment.
  • Fig. 1 schematically shows schematically a conventional process
  • Fig. 2 schematically shows schematically a process according to an example embodiment
  • Fig. 3 schematically shows schematically a process according to another example embodiment.
  • papermaking refers to both papermaking and boardmaking.
  • paper mill, paper machine, paper product, and like refer to both paper and board equally.
  • the sludge from a paper or board mill refers to aqueous medium comprising solids removed from the paper-making process to aqueous effluents.
  • the water content is preferably decreased to limit the sludge volume. However, keeping the sludge as slurry provides easier handling and transport thereof.
  • primary sludge refers to sludge obtained from primary wastewater treatment of the paper or board mill aqueous effluents. They follow typical wastewater treatments, where the solid material is removed in the primary phase. Typical process steps comprise settling, sedimentation and/or air flotation. The solids are recovered to be treated according to the present process and aqueous phase further treated in a secondary treatment.
  • ash refers to inorganic particles, the main component of primary sludge. Ash comes from recycled wastepaper, virgin fibre and fillers, such as ground calcium carbonate, precipitated calcium carbonate and/or clay.
  • the secondary treatment comprises biotreatment, referring to decreasing the waste load by microbes consuming mostly carbohydrates still contained in the aqueous phase recovered from the primary treatment.
  • the solids, i.e. the “secondary sludge” recovered from the secondary treatment comprise mostly microbial mass, typically bacteria.
  • the conditioned sludge as used herein comprises solid flocs formed by the cationic polymer (s) with solids in the sludge during the treatment of the present disclosure. It may be in the form of heterogenous mixture of aqueous medium with said flocs, or it may be more or less drained (i.e. at least part of the aqueous medium reduced or removed) in the form of moist or wet flocs. According to a specific embodiment where the conditioned sludge is subjected to separation, the conditioned sludge may be in a form of a thin or thick slurry, or as moist solids, where the water content is less than 20 %-wt.
  • the cellulosic fibres in the pulp may originally be produced by any suitable pulping method, i.e. they may originate from chemical pulping, mechanical pulping or chemi-mechanical pulping.
  • the cellulosic fibres may usually be wood-based fibres, but it is possible that at least some of them are non-wood-based fibres, e.g. cellulosic fibres originating from annual plants.
  • the pulp according to the present invention usually comprises a significant amount of recycled fibres or fibres originating from broke.
  • the degree of recycling of the cellulosic fibres may be high, so that the cellulosic fibres of the pulp comprise at least 50 weight-%, preferably at least 70 weight-%, more preferably 100 weight-%, of recycled fibre material, calculated from total amount of fibres, as dry.
  • the recycled cellulosic fibre material comprises at least 40 weight-%, preferably at least 50 weight-%, of fibre material originating from old corrugated containerboard (OCC) .
  • a paper or board mill sludge is treated with at least one cationic polymer to improve the reuse of said sludge as conditioned sludge.
  • the method can be defined to comprise obtaining a sludge from a paper or board mill and treating said sludge with addition of at least a first cationic polymer to obtain a conditioned sludge.
  • the sludge from a paper or board mill comprises primary sludge, or preferably, it is a primary sludge from a paper or board mill.
  • the primary sludge contains fibre, fine fibre, ash, paper-making chemicals, water-soluble residues, and other matter not attached to the fibre structure of the paper or board product formed.
  • said fines/ash/fibres are flocculated or aggregated to larger bundles which may be retained in the paper structure when the conditioned sludge is returned to the paper or board manufacturing process.
  • An example of a primary sludge composition may be described by characteristics compiled to table 1.
  • Table 1 An example of a primary sludge composition.
  • the present method is suitable for treating secondary sludges as well. According to a specific embodiment, the present method is suitable for treating combined primary and secondary sludges.
  • the dosage of the cationic polymer (s) may be surprisingly low in relation to the dry solids present in the sludges. Accordingly, in an embodiment of the present method and use, the dosage in the treating step of the first cationic polymer is 0.5 –10 kg/t of sludge dry solids, preferably 1 –5 kg/t of sludge dry solids, where t refers to ton, hence 1000 kg of sludge dry solids. Where the treatment comprises a combination of first and second cationic polymers, the dosage of each cationic polymer may be relatively lower than that of embodiments where the first cationic polymer is used alone.
  • the cationic polymer may be added in liquid form or in dry form, preferably in dry form as a particulate material. If the cationic polymer is in dry form, it is dissolved before its addition to the pulp. Irrespective if the polymer is in liquid form or dry form, it is usually diluted with water to a suitable dosing concentration before addition to the pulp.
  • Any cationic polymer used in the present invention may be obtained by any suitable polymerisation method for copolymerisation.
  • a cationic polymer may be obtained by suspension polymerisation, such as solution polymerisation or gel polymerisation; dispersion polymerisation; or emulsion polymerisation.
  • a cationic polymer is obtained by solution polymerisation or gel polymerisation.
  • the cationic polymer (s) may be obtained by copolymerisation comprising one or more cationic monomers.
  • the cationic polymer is obtained by copolymerisation of at least 10 mol-%, preferably at least 15 mol-%, more preferably at least 20 mol-%of solely cationic monomer (s) .
  • the cationic polymer may be obtained by copolymerising 10 –50 mol-%, preferably 20 –40 mol-%, more preferably 15 –30 mol-%of cationic monomer (s) with another preferably neutral charge monomer (s) .
  • the first cationic polymer has a charge from 10 to 50 mol-%, preferably from 20 to 40 mol-%, more preferably from 15 to 30 mol-%.
  • the charge value is relative to the amount of cationic monomer used in the polymerization. It has been observed that when at least 10 mol-%of cationic monomers is present in the polymerisation, the obtained cationic polymer is provided with good ability to associate with the solid material present in the sludge, e.g. through electrostatic forces, and at the same time its ability to interact also with the anionically charged cellulosic fine fibres present in the sludge is improved.
  • the cationic polymer may be obtained by copolymerization of a polyamide or acrylamide, cationic monomers and ⁇ 1 mol-%, preferably ⁇ 0.5 mol-%, more preferably ⁇ 0.1 mol-%of anionic monomers.
  • the cationic copolymer is free of anionically charged structural units, i.e. the copolymerisation is performed in the absence of anionic monomers.
  • the polymer thus preferably consists of structural units that originate from non-ionic monomers, i.e. amide (s) or acrylamide (s) , and from cationic monomers. Even in that case a minor amount of anionically charged groups may be formed to the polymer structure during polymer preparation, e.g. during drying.
  • the first cationic polymer has a standard viscosity at 25°C from 2 to 5.5 mPa ⁇ s, preferably measured using Brookfield DVII T viscometer with UL adapter. Standard viscosity is measured at 0.1 weight-%polymer content in an aqueous 1 M NaCl solution, using Brookfield DVII T viscometer equipped with UL adapter, at 25 °C. In general, the standard viscosity of the polymer gives an indication of the length and/or weight of the polymer chains of the polymer.
  • the standard viscosity SV of the cationic polymer is at from 2 to 5.5 mPa ⁇ s, the polymer is able to effectively associate with the solids present in the sludge (s) . It is assumed that the cationic polymer has an improved ability to tie anionic fine fibres to bundles or flocs large enough to be retained in the cellulosic fibre structure when recycled and added to the pulp.
  • the first cationic polymer is selected from polyamines and/or polyacryl amides (PAMs) .
  • PAMs polyacryl amides
  • Polyacryl amides are preferred polymers for the first cationic polymer.
  • polymers are formed of repeating units of monomers, and hence polymers may be defined by the monomers which through polymerisation or copolymerisation yield said polymers.
  • the cationic monomer (s) may be selected from 2- (dimethylamino) ethyl acrylate (ADAM) , [2- (acryloyloxy) ethyl] trimethylammonium chloride (ADAM-Cl) , 2- (dimethylamino) ethyl acrylate benzylchloride, 2- (dimethylamino) ethyl acrylate dimethylsulphate, 2-dimethylaminoethyl methacrylate (MADAM) , [2- (methacryloyloxy) ethyl] trimethylammonium chloride (MADAM-Cl) , 2-dimethylaminoethyl methacrylate dimethylsulphate, [3- (acrylamido) propyl] tri
  • the cationic polymer may be selected from polyamines comprising dimethylamine and epichlorohydrin monomers, wherein dimethylamine provides the cationic charge.
  • the treating in the present method and use comprises the addition of the first cationic polymer, an addition of at least one second cationic polymer.
  • the treatment is easier to control and adapt to specific characteristics of the sludge at hand. For example, viscosities, charges, and dosages of first and second cationic polymers can be chosen to provide desired flocculation.
  • the present inventors have found most beneficial to add the first and the second cationic polymer in sequence.
  • the preferred order for additions is adding 1) the first cationic polymer and 2) the second cationic polymer. This procedure allows the first cationic polymer to level the charges for a period of time, before the solids are flocculated with the addition of the second cationic polymer.
  • the second cationic polymer has a standard viscosity at 25°C from 3 to 5.5 mPa ⁇ s, preferably measured like the first cationic polymer, i.e. using Brookfield DVII T viscometer with UL adapter. Compared to the first cationic polymer the second cationic polymer has preferably a higher standard viscosity. This applies accordingly to the molecular weight. Hence, according to a preferred embodiment, the second cationic polymer has a molecular weight higher than that of the first cationic polymer.
  • the second cationic polymer has a charge which is higher than that of said first cationic polymer. This has been found experimentally to provide controlled flocculation and optimised cationic polymer dosages.
  • the dosage of the second cationic polymer in the treating step may be at least 0.5 kg/t of sludge dry solids, such as 0.5 –7 kg/t, preferably 1 –5 kg/t of sludge dry solids.
  • the second cationic polymer may be selected from cationic polyacrylamides. More specifically, the second cationic polymer may comprise monomers selected from 2- (dimethylamino) ethyl acrylate (ADAM) , [2- (acryloyloxy) ethyl] trimethylammonium chloride (ADAM-Cl) , 2- (dimethylamino) ethyl acrylate benzylchloride, 2- (dimethylamino) ethyl acrylate dimethylsulphate, 2-dimethylaminoethyl methacrylate (MADAM) , [2- (methacryloyloxy) ethyl] trimethylammonium chloride (MADAM-Cl) , 2-dimethylaminoethyl methacrylate dimethylsulphate, [3- (acrylamido) propyl] trimethylammonium chloride (APTAC) , or [3- (methacryla
  • the first and second cationic polymers may both be copolymerised from a polyacrylamide monomer and a cationic monomer with proviso that the amount of said cationic monomers is higher in the second cationic polymers relative to the amount of said cationic monomers in the first cationic polymer.
  • the conditioned sludge obtained from the treatment according to the present method may be recycled back to the papermaking process.
  • the conditioned sludge may be added as such, or alternatively it may be subjected to a further physical or chemical process step. Adding the conditioned sludge as such, without further process steps is useful as it requires no specific separation equipment nor maintenance thereof. Further, slurries are conveniently mixed to the pulp at the site of addition.
  • a typical physical step is separation.
  • the conditioned sludge may subjected to a separation using at least one or more separation techniques for heterogenous mixtures.
  • Separation method (s) for the conditioned sludge may be selected to be one or more of filtration, centrifugation, sedimentation, screening and/or decantation.
  • Preferred separation methods comprise screening and/or centrifugation.
  • the aim of the separation is to collect the solids from the conditioned sludge as a slurry.
  • Preferably at least some of the aqueous phase is removed from the solids. With the aqueous phase, some chemicals and/or microbes may be discarded whereby they are not returned to the papermaking process.
  • the flocs comprising the cationic polymer (s) associated with solids may be recovered and recycled back to the papermaking, to fibre web forming.
  • some chemicals and/or excess water may be removed. Especially, removing smallest particles and stickies with the excess water is beneficial.
  • the major advantage gained by separation is the reduction of the sludge volume.
  • the cationic polymer (s) the majority of solids flocculated, some small particles still remain suspended in the aqueous phase. These small particles will not be retained in the fibre web produced from the pulp and hence they do not contribute thereto.
  • these small particles are removed and will not disturb the process to which the conditioned sludge is added.
  • Another type of impurities which can be reduced by aqueous phase separation and discarding are stickies which tend to stay dispersed or dissolved to the aqueous phase.
  • the conditioned sludge may be reused in a paper or board mill, wherein the method further comprises adding the conditioned sludge to pulp.
  • the conditioned sludge returns to the pulp some fine fibres, ashes and other solids removed with aqueous effluents but as said solids after treatment according to the present disclosure interact with the cationic polymer (s) , they behave in the pulp like other larger particles in the process, and hence are retained in the fibre web and contribute to the product formed thereof.
  • the site of the addition of the conditioned sludge may be selected in the present method or use. Accordingly, the conditioned sludge may be added to the pulp to at least one site in the paper or board mill may be selected from a pulper, a dump tower, a mixing chest, a machine chest, and/or a fan pump, preferably to a mixing chest or fan pump, most preferably to a mixing chest.
  • addition to pulper takes place at an early stage of the process, and other embodiments provide the addition at a later stage of the process, such as at a mixing chest or fan pump.
  • a later addition mechanical stages are avoided which contributes to keeping the flocs formed by cationic polymer addition untangled and together.
  • addition to mixing chest or fan pump provides improved control the sludge reuse for drainage, retention, and strength. It also helps to reduce energy consumption as recirculation of the sludge components in the re-pulping system needed in the early addition can be avoided.
  • a further advantage of the addition of conditioned sludge at a later stage of the process, such as to a mixing chest or fan pump, is easier increase of the sludge ratio in a controlled manner thereby leading to reduced raw material costs.
  • Improved sludge retention obtainable through addition at a later stage, that is closer to paper or board production, is also desired.
  • the pre-formed micro-flocs contribute to water removal in the wire section.
  • the paper process equipment surfaces benefit from reduced deposition through good fixation and retention.
  • the conditioned sludge may be added to the pulp in a significant amount.
  • the conditioned sludge may be added to the pulp in an amount of 1 – 10 %-wt, preferably 2 –8 %-wt, more preferably 3 –6 %-wt, such as 5 %-wt of the total pulp weight (dry weight/dry weight) .
  • the present experiments have shown that surprisingly high proportion of pulp may be replaced with the conditioned sludge without disturbance in the process or deterioration of the end product quality. Compared to pulps where no sludge was used or untreated sludge was used, some product characteristics were even found to be improving with conditioned sludge produced according to the present method and use.
  • conditioned sludge in a paper or board mill, wherein the conditioned sludge is obtained by a method as here described.
  • the conditioned sludge may be used at least for replacing a part of pulp, for improving dewatering and retention, for improving runnability, for decreasing solid waste and decreasing chemical oxygen demand in effluent, for obtaining a cleaner effluent in a paper mill waste-water treatment, or for improving paper or board product strength.
  • two or more of said effects are obtained by the present use simultaneously.
  • FIG. 1 shows a conventional stock preparation process without sludge additions. Schematically the process may be presented beginning from a pulper 100. Pulper produces pulp from cellulose fibres with aid of water and chemicals. In case recycled material is used, it gently slushes the recycled paper or board raw material into a pumpable pulp. Water is fed to the pulper via line 401. The pulp is stored in dump tower 110. The next operations, screening 120 and fractionation 130, separate the fibres in the pulp by size, especially the fibre length. The long fibres are next filtered in disc filter 140a and the short fibres in disc filter 140b wherefrom aqueous effluent may be discarded.
  • the long fibres are stored in storage tower 160a (and short fibres in storage tower 160b) .
  • the pulp from storage tower 160 a/b is mixed in mixing chest 170 with broke fed from broke storage tower 310 via line 301.
  • the pulp from machine chest 180 is mixed with white water from wire section and pumped with a fan pump 190 to the head box 200.
  • the steps after the head box, where the fibre mat is formed and pulp is drained are depicted as unit 300.
  • the black arrows in Figure 1 indicate the fibre stock flow through the stock preparation process and the dash lines indicate aqueous flows recycled within, stored in water storage tanks 410 and 420, or removed from the stock preparation process to the wastewater treatment and/or sludge reuse via line 402.
  • the conditioned sludge may be reused in a paper or board mill, wherein the method further comprises adding the conditioned sludge to the pulp.
  • Embodiments, where the conditioned sludge 500 is added to the pulp in early stage (s) is depicted in Figure 2.
  • the site of addition of the conditioned sludge is at pulper 100, via line 501, or at dump tower 110 via line 502 or a combination thereof.
  • This embodiment enables both macro-and micro-stickies to be at least partly removed in the normal cleaning process (mainly at screening 120) . Thereby separate purification of the conditioned sludge is not needed.
  • Embodiments, where the conditioned sludge is added to the pulp in later stages of pulping are depicted in Figure 3.
  • Other embodiments provide the addition at a later stage (s) of the process, such as at a mixing chest 170 via line 511, machine chest 180 via line 512, fan pump 190 via line 513, or any combination thereof.
  • a later stage (s) of the process such as at a mixing chest 170 via line 511, machine chest 180 via line 512, fan pump 190 via line 513, or any combination thereof.
  • Figure 3 depicts addition to all these sites, according to different embodiments, one, two or more addition sites may be employed dependent on the conditioned sludge characteristics and/or process controls.
  • Advantages related to later addition of the conditioned sludge include avoiding mechanical stages provision of improved control the sludge reuse for drainage, retention, and strength, and further reduction of energy consumption.
  • the primary sludge had pH of 5.93, a solids content of 8.75 weight-%, ash content (ash in solids) of 60.8 weight-%.
  • the dilution water was prepared consisting of 70 weight-%calcium acetate, 20 weight-%sodium sulphate, and 10 weight-%sodium bicarbonate. The conductivity was adjusted to 4 mS/cm and the pH to 7.
  • the OCC liner board sample had a dry content of 94 weight-%, ash content of 15 weight-%, a grammage of 120 g/m 2 .2 cm x 2 cm sized pieces of the OCC board were soaked in 85°C dilution water for 5 minutes.
  • the pulp (2.5 weight-%) was hot-disintegrated with a Lorentzen &Wettre Pulp Disintegrator at 30000 rpm for 10 minutes, after which the pulp was diluted to 1.25 weight-%consistency. The pulp was left to cool down to room temperature, and the pH was adjusted to 7.
  • One set was created from mixture that contained the pulp and 50 kg of the primary sludge (untreated) per ton of pulp, based on the dry solids weight of the stock and the sludge.
  • One of the sets of hand-sheets was created from pulp that contained the pulp and 50 kg of polymer A-treated sludge per ton of pulp, based on the dry solids weight of the stock and the sludge.
  • the polymer A-treated sludge contained 2.0 kg of polymer A per ton of sludge, based on the dry solids weight of the sludge and polymer A.
  • Another set of hand- sheets was created from pulp that contained the pulp and 50 kg of polymer B-treated sludge per ton of pulp, based on the dry solids weight of the stock and the sludge.
  • the polymer B-treated sludge contained 5 kg of polymer B per ton of sludge, based on the dry solids weight of the sludge and polymer B.
  • the fourth set of hand-sheets was created from mixture containing the pulp and 50 kg of sludge treated with combination of polymers A and B-treated in sequence, based on the dry solids weight.
  • the sludge treated with combination of polymers A and B consisted of the primary sludge treated with 2.0 kg of polymer A followed by treating with 3.0 kg of polymer B per ton of sludge, based on the dry solids weight of the polymer A and polymer B solutions and the sludge.
  • the polymer A was a medium molecular weight cationic polyacrylamide having a charge of 20 mole-%, a standard viscosity of 3.5 mPa ⁇ s.
  • the polymer B was a high molecular weight cationic polyacrylamide having a charge of 40 mole-%and a standard viscosity of 4.15 mPa ⁇ s.
  • Ref 1 shows folding of the sheets without sludge, i.e. prepared from the pulp only.
  • Ref 2 shows folding of sheets containing the untreated sludge.
  • Examples 3, 4 and 5 show folding of the sheets containing polymer-treated sludge according to the present invention.
  • Comparison of Ref 1 and Ref 2 indicates that adding sludge to the pulp adversely affects the strength of paper sheets made from the resulting pulp. Treating the sludge with a single polymer prior to incorporating the treated sludge into the pulp, results in reduced folding strength loss of the resulting sheets. The combined use of two polymers in the sludge treatment further reduced the loss of sheet strength as compared with treatment with one polymer alone.
  • the sludge was primary sludge from WWTP of a paper mill mainly using OCC as raw material to produce duplex board and kraft liner board.
  • the primary sludge used in experiments had pH of 6.7, a solids content of 3.9 weight-%, ash content (ash in solids) of 60.8 weight-%.
  • the diluted stock was then subjected to rapid mixing of about 1000 rpm for another 15 seconds.
  • the stock containing the sludge was then treated with retention program (adding retention polymer in an amount of 0.25 kg/t, rapid mixing for 5 seconds, followed by addition of silica sol in an amount of 0.4 kg/t, rapid mixing for another 10 seconds.
  • the stock in the reaction vessel was then drained through a 0.25 mm wire under vacuum of about 200 mPa. After the drainage was completed, the drainage time (avalue which is automatically computed and shown) was then recorded.
  • Ref 11 shows the result without any sludge addition.
  • Ref 12 showed that addition of untreated sludge had deteriorated the drainage.
  • Examples 13-15 clearly show the decrease in drainage time compared to the reference sample, indicating that sludge treatment by a single polymer resulted in much better drainage.
  • the combined use of two polymers in the sludge treatment significantly improved the drainage as compared with treatment with one polymer.
  • all results obtained with the conditioned sludges (Polymer A, Polymer B and combination of polymers A and B) according to the present invention provided better drainage, i.e. shorter drainage times than the reference sample 11 without any sludge addition.

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  • Hydrology & Water Resources (AREA)
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  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Separation Of Suspended Particles By Flocculating Agents (AREA)
  • Paper (AREA)
  • Treatment Of Sludge (AREA)

Abstract

L'invention concerne un procédé relatif au traitement de déchets, plus particulièrement des boues provenant de la production de papier ou de carton, comme la production de fibres de carbone recyclées. L'invention concerne un procédé de traitement desdites boues afin d'améliorer leur réutilisation, en particulier, en tant que boues conditionnées dans lesdits procédés de production de papier ou de carton. L'invention concerne également des utilisations dans un broyeur de papier ou de carton desdites boues conditionnées obtenues par ledit procédé.
EP22945327.9A 2022-06-10 2022-06-10 Procédé de traitement de boues d'usine de papier ou de carton pour réutilisation Pending EP4536599A1 (fr)

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Application Number Priority Date Filing Date Title
PCT/CN2022/098119 WO2023236185A1 (fr) 2022-06-10 2022-06-10 Procédé de traitement de boues d'usine de papier ou de carton pour réutilisation

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EP4536599A1 true EP4536599A1 (fr) 2025-04-16

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EP (1) EP4536599A1 (fr)
KR (1) KR20250022765A (fr)
CN (1) CN119343321A (fr)
WO (1) WO2023236185A1 (fr)

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JP4239034B2 (ja) * 2006-05-24 2009-03-18 王子製紙株式会社 無機粒子の製造方法およびその製造プラント
CN103469697A (zh) * 2012-06-06 2013-12-25 江苏五洲纸业有限公司 一种造纸污泥纸板的生产方法
FI20165978L (fi) * 2016-12-16 2018-06-17 Kemira Oyj Menetelmä veden poistamiseksi lietteestä
CN107445420A (zh) * 2017-07-24 2017-12-08 佛山金盛联合纸业有限公司 一种造纸污泥的回用方法
CN109912175A (zh) * 2019-03-29 2019-06-21 嘉兴卓盛生物科技有限公司 一种基于微粒的造纸污泥回用系统

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KR20250022765A (ko) 2025-02-17
WO2023236185A1 (fr) 2023-12-14
CN119343321A (zh) 2025-01-21

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