Classifications

• • 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
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/06—Paper forming aids
  • D21H21/10—Retention agents or drainage improvers
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F1/00—Wet end of machines for making continuous webs of paper
  • D21F1/66—Pulp catching, de-watering, or recovering; Re-use of pulp-water
  • D21F1/82—Pulp catching, de-watering, or recovering; Re-use of pulp-water adding fibre agglomeration compositions
• • 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
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/36—Biocidal agents, e.g. fungicidal, bactericidal, insecticidal agents

Definitions

• the present invention relates to a device and a method for increasing the yield (getting more final product from a given incoming amount of raw materials and additives), as well as for enabling an increase in productivity (amount per time unit) and an increased amount of production (amount of production per given amount of pollutant to an end recipient), and at the same time to improve purification of process water and waste water, respectively, by decreasing the waste water flow and the amount of pollutants in the waste water.
• the method comprises increased recycling (recovery, closing) of process water, in combination with utilization of substances to be included as materials in an end product formed, instead of constituting pollutants in the waste.
• equivalent or improved dewatering properties are achieved in the production process, thereby enabling increased productivity and/or amount of end product formed, in relation to the maximum amount of effluent to the recipient allowed for the activity.
• oxidizing agent functions both as a type of ionizer (polarizer) of, as well as a type of catalyst for polarization between, particles, substances and additives suspended in the water.
• polarizer ionizer
• the effect is influenced by factors such as the concentration of oxidizing agent, the degree of installation, position and order of water flows in the process, mixing methods, suspension characteristics of pollutants, choice and properties of chemical additives (retention agents, etc.), dosage of additives and dosing positions, as well as other parameters.
• the said effect goes beyond prevailing and common effects that can be achieved by strong oxidizing agents and that are used, to a limited degree, in this type of industry in order among other things to kill microbiological cultures, to decompose pollutants comprising COD and BOD, to bleach substances in the end product, etc., as is known from FI 110683B, e.g.
• the method results in an economical gain, by decreasing the discharge of substances (pollutants) in the waste water, instead to be recycled to the process as raw materials, and by enabling an increased productivity and/or production capacity by improved dewatering properties for the web of material formed during production.
• This objective arises by a) gradually increased requirements, established by the authorities and relating to amounts of pollutant effluents allowed from the process industries, as well as b) the need for the industry constantly to try to increase productivity and profitability by increasing the utilisation of added raw materials, decreasing the amount of cost-increasing additives, and by trying to increase production.
• waste water means material-containing (polluted) process water that is led to an external purification plant outside the process plant, and thereafter, after processing, to the recipient.
• External waste water purification takes place by a combination of chemical, physical and biological purification methods. It is of utmost importance to minimize the amount of pollutants in the waste water as well as the amount of waste water, in order to minimize investment and operational costs for a purification plant.
• water treatment and water purification within pulp and paper industry comprises three separate steps or parts.
• the first part is cleaning and treatment of incoming raw water for the plant.
• such water is taken from a lake or a large stream.
• the second part comprises purification of the internal process water
• the third part comprises purification of polluted water that is not intended to be re-used (closed) in the process and that therefore is led away therefrom as final waste water.
• the measures for the second step purification (within the plant) could partly be of the same basic technical nature as the measures undertaken in the third step, but could also be of totally different nature.
• the pollutants in the form of suspended substances and acid-consuming substances, leaving the production process by the waste water consist to a major part of raw material substances such as cellulose material and additives. These substances would have given an increased production yield if they could have been better kept and utilised as a part of the end product instead of leaving the plant by the waste water.
• Internal measures to decrease effluents in the form of waste water for external purification include modifications of the production processes, in order to generate less effluents, as well as various methods for recycling internal process water (so called white water) used in the plant, in order to recycle raw materials in such water to the produced end product.
• white water used in the plant
• Fresh water is constantly supplied to the process water system (which also means that roughly the same amount of water leaves the system in the form of waste water).
• the major part of the process water is recycled to the paper machine. This closing decreases water consumption and loss of raw materials.
• flocculants are charged to increase retention of materials in the formed product. It is important in this case that the flocculation results in flocks of material with beneficial dewatering properties, since the dewatering is of decisive importance to the productivity of a paper machine.
• Biopurification is meant the use of cultures of micro- organisms in order to decompose pollutants and acid-consuming materials, other bacterial cultures, etc. It is also known in a few pulp and paper mills to use ozone in the last (external) purification step, after extensive biological treatment. In these cases, ozone is above all used in large amounts to oxidize high-molecular materials, being very hard to decompose in a biological purification plant, into substances of lower molecular size that can thereafter be decomposed in a subsequent biological purification step.
• ozone is also used to kill bacteria, see FI 110683B e.g.
• a method is described of using ozone to kill micro-organisms in the internal process water in paper mill.
• the technique moreover can be formed such that material separated from the process water in the purification steps can be recovered as a marketable product, i.e. be completely or partly recycled in the production process, instead of, as now, constituting a load on the external waste water purification, then an economically profitable incentive has been introduced for a gradual improvement of the purification technique.
• a cost has been converted into "profitable" recovery, as well as increased productivity, i.e. a purification that pays its own cost or even more.
• the present application relates to the accomplishment of chemically affecting the substances in the process water, thereby becoming more reactive in order to accumulate to form larger aggregates, so called flocculation, and also so that the substances will more easily react with chemicals added to improve flocculation, the now said being achieved by mixing in an oxidizing agent such as ozone gas in the process water.
• an oxidizing agent such as ozone is used for a different purpose than what has been done previously in the process line.
• the oxidizing agent may be ozone or some other oxidizing agent having an potential of oxidation of preferably above 1.5 V.
• ozone has been used previously in external purification in order to improve separation of COD.
• Ozone has also been used as a bactericide in the internal process water, and as a bleaching agent.
• ozone is used to achieve a flocculation, or to render it more effective, of substances in the flow of fibre pulp as well as in the process water.
• the result thereof is a decrease in the amount of substances that leave the production by the waste water, which means an increased yield in relation to used raw material, as well as a decreased load on the external purification plant, resulting in an economical contribution to the pulp and/or paper mill, instead of becoming a costly problem of depositing.
• the process water quality is also generally improved by addition of oxidizing agents, preferably ozone, thus enabling decreased water consumption for the production process for paper and pulp (increasing the degree of recycling, i.e. increasing the degree of closing). Bacteria and bacteria growth is reduced, otherwise leading to odour, formation of slime and disturbances in substance flocculation.
• oxidizing agents preferably ozone
• the improved flocculation properties that can be achieved by addition of oxidizing agents, will also result in an improved function (increased degree of separation) for the mechanical equipment for treatment of process water, such as screens, filters and similar.
• the function is also improved for settling and flotation equipment, intended for separation of materials from the process water. In particular, it is fragments of cellulose fibres and other particulate substances that in this way are more efficiently separated from the process water.
• the flocculation of substances and the process of forming fibre material into a fibre network is of central importance to the production result.
• the addition of an oxidizing agent will give a beneficial structure of the fibre network during forming of the network, thus increasing retention of substances in the network, and at the same time, separation of water from the fibre network is facilitated due to the changed network structure.
• utilisation of the material is improved (increased retention), as well as so called runnability (less frequent disturbances during production) for the various process steps in pulp and paper production.
• the treatment with the oxidizing agent is also colour-reducing, resulting in that the most often darker colour of the sludge can be reduced to a suitable nuance, as desired.
• a higher dosage of the oxidizing agent will be more colour-reducing than a lower dosage. This affects the possibility to recycle the sludge as a part of the products, without affecting the colour of the material.
• Fig. 1 shows a schematic drawing of material and water flows in pulp and paper production, in which an ionization and oxidation step 12 has been introduced in the process
• Fig. 2 shows an embodiment example of the mixing-in of ozone gas according to the present invention.
• Fig. 1 shows a schematic drawing of material and water flows in pulp and paper production, in which an ionization and oxidation equipment 12 has been introduced in the process, preferably just before the forming equipment 14.
• Raw materials 1 and water 2 are supplied to the production process 3.
• the product 5 is produced and water vapour 4 and polluted output process water 6 leaved the production process 3.
• the output process water 6 is purified in an external purification plant 7 for waste water, from which one part leaves as sludge 8 for deposit and/or incineration, and the purified water 9 is let out to the recipient (i.e. the environments). Looking closer into the production process 3, it can be seen that raw material 1 and water 2 are supplied to a pulp and stock preparer 10.
• Also recycled process water 15, 20 is supplied to the pulp and stock preparer, from the storage tank 19 for white/process water and the forming equipment 14 (preferably a paper machine), respectively.
• the pulp/water mixture 11 resulting form the pulp and stock preparer 10 is thereafter exposed to an ionization and oxidation step 12 (see Fig. 2).
• the ionized and oxidized output water 13 from the ionization and oxidation equipment 12 is thereafter introduced in the forming equipment 14.
• the water flow 11, 13 is also treated with retention agents.
• the distance between the pulp and stock preparer 10 and the forming equipment 14 can be relatively large. It is preferred that the ionization and oxidation equipment 12 is situated more or less in direct connection with the forming equipment 14.
• the forming equipment 14 produces the paper product 5 by distributing the treated, fibre-carrying water 13 (the pulp suspension) onto a forming wire. A part 15 of the white water 15, 16 from the forming equipment 14 is recycled directly to the pulp and stock preparer 10, in the so called short circulation, another part 16 goes to internal purification equipment 17. Furthermore, water also leaves as water vapour 4 that is let out.
• the internal purification equipment 17 may for example contain various screening steps and/or flotation steps, in which a part 18 of the water can be re-used and therefore be sent to a storage tank 19 in order to be recycled to the pulp and stock preparer 10.
• the water 6 that contains a higher concentration of reject material than water 16 and 18, and that is not led to the storage tank for process water 19, is sent to external purification equipment 7 (such as flotation basins) that separates bio-sludge 8 and water 9 that is considered to be adequately purified and that is therefore returned to the environments. Under certain circumstances, parts of the bio-sludge 8 can be returned to the production process 3 at the ionization and oxidation equipment 12.
• FIG. 2 One embodiment example of the mixing-in of ozone is shown in Fig. 2, i.e. the ionization and oxidation equipment 12 that is inserted between the pulp and stock preparer 10 and the forming equipment 14 (see Fig. 1).
• a pulp/water mixture 11 typically having a pulp concentration of between 0.5 and 5 %, is pumped into a container 27 (the mixture is normally diluted with internal process water that in turn contains pulp concentrations of normally below 0.5 %).
• Ozone gas 24 is added to the bottom of the container 27, by being injected into the container 27 in the form of small bubbles 25, in order thereby to increase contact surfaces against the pulp/water mixture 11.
• the ozone gas 24 can be generated by using an ozone generator.
• a stirrer Preferably, a stirrer
• the container 27 is positioned inside the container 27, in order to stir the pulp/water mixture 11 and further to increase the possibilities for the ozone gas bubbles 25 to react with the substances in the pulp/water mixture 11.
• other stirring means for the pulp/water mixture 11 can be used.
• the top of the container 27 is provided with outlet pipes 21, 22 for remaining ozone gas 24 that has passed the pulp/water mixture 11 without having reacted.
• the remaining ozone gas 24 can either be led via pipe 21 to an ozone-destroyer, or it can be returned to the ozone generator via pipe 22, for re-use in order thereafter to be recycled to the container 27.
• the ozone gas 24 is preferably added in the above described reactor vessel 27. However, it can also be added in a longer pipe in which the ozone gas 24 is mixed with the pulp mixture 11.
• the process water 11 should be stirred during the reaction time.
• the dwell time for the liquid 11 in vessel 27 is a function of the volume of the vessel 27 and the liquid volume flow through vessel 27. If the concentration of ozone is high in the ozone gas 24, the contact time may be shorter in order to achieve the same effect of the ozone gas (the so called Ct factor, where gas concentration and reaction time is a product factor that weighs the importance of changes in gas concentration and reaction time, respectively).
• Stirring can take place either by a stirrer 23 in a container 27, or by a so called static mixer in a pipe through which process water 11 and ozone gas mixture 24 are pumped.
• the ozone gas 24 can be added e.g. by being bubbled 25 into the process water 11, at as small gas bubbles as possible, in order to achieve a contact surface with the process water 11 that is as large as possible.
• Mixing-in can take place e.g. by bubbling equipment, e.g. acting from the bottom of a container 27 in which the process water 11 is contained.
• Mixing-in can also take place via a mixing-in pump such as a type of turbine pump, or by adding ozone gas 24 into a pipe by aid of a so called ejector or by a dosing lance.
• the mixing of the process water 11 and the added ozone gas 24 should be as good as possible. If it is desired to recycle parts of the bio-sludge 8 that is separated in the external purification 7 (see Fig. 1), parts of the sludge 8 can be recycled to the container 27 in which the ozone gas 24 is added to the process water 11.
• oxidizing agents can be used at greater or less extent, and in combination. It is also conceivable that the part of the white water 15 from the forming equipment 14, that is recycled directly to the pulp and stock preparer 10, is exposed to an ionization and oxidation step. Furthermore, water 20 from storage tank 19 can be exposed to an ionization and oxidation step in direct connection with the pulp and stock preparer 10.

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Pest Control & Pesticides (AREA)
• Paper (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)
• Treatment Of Water By Oxidation Or Reduction (AREA)
• Removal Of Specific Substances (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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• 2004
  • 2004-09-10 SE SE0402178A patent/SE0402178D0/xx unknown
• 2005
  • 2005-09-12 AT AT05783356T patent/ATE486999T1/de not_active IP Right Cessation
  • 2005-09-12 PL PL05783356T patent/PL1786974T3/pl unknown
  • 2005-09-12 EP EP05783356A patent/EP1786974B1/de not_active Not-in-force
  • 2005-09-12 US US11/662,359 patent/US20090277598A1/en not_active Abandoned
  • 2005-09-12 WO PCT/SE2005/001324 patent/WO2006041369A1/en active Application Filing
  • 2005-09-12 DE DE602005024576T patent/DE602005024576D1/de active Active
  • 2005-09-12 ES ES05783356T patent/ES2355799T3/es active Active

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