Classifications

• • 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
• • 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
  • D21H21/18—Reinforcing agents
  • D21H21/20—Wet strength agents
• • 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
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/04—Addition to the pulp; After-treatment of added substances in the pulp
  • D21H23/06—Controlling the addition
  • D21H23/14—Controlling the addition by selecting point of addition or time of contact between components

Definitions

• the present invention relates to a method at a paper machine for reducing the spreading of agents added to the process in a continuous process for preparation of pulp for a paper machine, whereby a flowable paper pulp including fibres and process liquid and having a consistency of not more than 10% is conducted to the headbox of the paper machine.
• the present invention also relates to an arrangement at the pulp preparation for a paper machine in order to restrict a spreading of additional agents in the further process, whereby the process comprises an inlet for a flowable pulp having a consistency of not more than 10 % and including a fibre material and a process liquid, a closed cycle system including a headbox for the paper machine, as well as means for adding said additional agent.
• a paper machine is defined as a machine for manufacturing paper as a continuous web.
• the expression pulp preparation as used in the present patent application indicates a process where starting from a pulp mass comprising fibres, usually a cellulose material, and having a more or less firm consistency, a paper pulp mass is prepared under mixing to be transferred further to the head ⁇ box, whereby the pulp mass includes not more than 10 % fibre material, normally at least 1 %, suitably 2 to 7 % and usually 3 to 5 %, as well as added process liquid, usually water.
• a pulp preparation includes a so called pulper where a fibre material from a cellulose process is resolved during decomposition and agitation, and mixed with process water.
• Traditional papermaking includes a process where a pulp mass which essentially comprises a fibre material and process liquid is conducted via a headbox for de-watering on a wire. A multitude of further steps and arrangements are associated to the process, including vessels where the consistency typically is 3 to 5 %, whereby much surplus liquid is conducted in an upstream direction back into the process.
• a traditional process includes a recovering by means of, e.g., flotation in recovering devices, after which the clear water from the flotation is recycled in the pulp preparation.
• titanium dioxide will lose in optical effect, and yet a part will be lost in the form of, for example, deposition in the system. Additionally, there are, of course, the drawbacks caused by separate arrangements for fibre recovery, costs of investments and operating and costs depending on a contamination and cleaning of the systems, as well as the more complicated process chemistry which a recovery in line with prior art requires.
• the object of the present invention is to avoid the drawbacks which until now have been connected to the use of pigments and especially in connection with a change of the paper grade.
• the present invention is based on the astonishing realization that by raising the consistency of the pulp at an early stage of the process it is, in practice, possible to cut the arrangement which in traditional papermaking is called the long circulation, i.e. a circulation system where white water in accordance with traditional arrangements can run from the wire pit of the paper machine upstream in the system up to the point where pulp is added, for example to a pulper.
• the long circulation i.e. a circulation system where white water in accordance with traditional arrangements can run from the wire pit of the paper machine upstream in the system up to the point where pulp is added, for example to a pulper.
• a flow of valuable additional agents directed upstream can be prevented, for example a flow of titanium dio ' xide and other pigments which otherwise partially would be lost and partially contaminate the whole chain of process .
• the method according to the present invention is characterized in that the consistency of the pulp is increased, prior to the introduction of said additional agent and suitably at a separate process stage, to a value of more than 10% by removing process liquid, in that this process liquid is conveyed upstream in the process, while compensating process liquid, which suitably can contain additional agents, is added downstream in the direction of the process.
• a process according to the present invention is characterized in that separating means are arranged prior to the means for introducing the additional agent, seen in the direction of the process, but after said inlet, whereby these separating means are arranged to separate process liquid from the flowable pulp so that the consistency of the pulp will increase to a value of more than 10%, in some cases favorably even up to 50%.
• the arrangement further includes means for conveying the liquid which has been separated from the process liquid in an upstream direction in the process, as well as means for a downstream introduction of process liquid from said circulation in order to compensate the separated process liquid.
• This latter process liquid can, as such, contain more or less additional agent (s) .
• Figure 1 as a principle drawing discloses an arrangement ac ⁇ cording to one embodiment of the present invention
• Figure 2 generally discloses a paper machine arrangement in accordance with an especially favorable embodiment.
• a paper machine typically includes an inlet for a fiber containing material, i.e. cellulose which usually is provided in the form of dry sheets or, at so called integrated plants, directly from a cellulose plant in the form of a fibre containing process liquid.
• a fiber containing material i.e. cellulose which usually is provided in the form of dry sheets or, at so called integrated plants, directly from a cellulose plant in the form of a fibre containing process liquid.
• a pulp preparation including a so called pulper 2 where the sheets are disintegrated and mixed with process water, for example from a tank 3, to constitute a so called stock or papermaking pulp.
• the pulp passes through different process stages 4a, 4b, 4c, 4d, 4e ... which in this context are essentially ir ⁇ relevant, and finally it is spread via the paper machine's headbox 5 onto a wire 6.
• the wire runs through a machinery 7 where the process liquid to an extensive portion is exhausted by suction in the form of so called white water, while the moist remaining pulp
• the white water also to some degree contains chemicals that will do be retained in the paper. These chemicals follow with the process water which to some parts is used in the so called short circulation for dilution purposes at such process stages where said chemicals are needed as such, or where they in any case cause only minor harm.
• White water used for other purposes is cleaned in different processes and cleaning stages, on one hand to recover the chemicals and, on the other hand, to obtain a clean water which can be used in other parts of the process. Each such cleaning process, is, however, to some extent incomplete and additionally requires both energy, time and apparatus .
• the system according to the present invention differs essentially from the known technology described above.
• a separation has only been adopted in order to prevent chemicals that disturb lower processes from flowing downwards, while the idea is quite new that a prevention of valuable additive agents from contaminating upstream also may be realized in a corresponding manner.
• the removing separation of process liquid is favorably effected by means of such a thickening technique which is known per se from, for example, production of cellulose, bleaching and de-inking.
• a thickening technique which is known per se from, for example, production of cellulose, bleaching and de-inking.
• Such arrangements are usually capable of increasing the consistency of the fibre containing pulp mass from an initial value of 2 to 10%, in the present case typically in the order of about 4 to 6%, to a final value of even up to 50% and possibly even higher.
• the separation is performed by means of a pressing which favorably takes place prior to a beating 4c.
• the pressing at the thickening favorably then takes place in a screw or band press 8a of a type known per se, so that the slushed pulp after pressing obtains a dry matter content of ⁇ more than 10%, especially within an interval of 20 to 50%, suitably 25 to 40%, favorably at least 30%.
• the process liquid which is separated during the pressing is conveyed 11 back in the upstream direction into the process, suitably back to the pulper 2.
• the liquid which has been separated from the process is suitably replaced 13 in a dispersing device 12 with an essentially corresponding amount of liquid taken from the circulation of the paper machine.
• a dispersing device 12 with an essentially corresponding amount of liquid taken from the circulation of the paper machine.
• this takes place in an arrangement according to the applicants international patent application No PCT/FI99/00143, or alternatively by means of a screw arrangement or a mixer of some other type.
• the dispersing device 12 is favorably arranged in the process direction essentially directly behind the separation 8, 8a.
• the main introduction 14 of critical added agents such as very expensive pigments and coloring agents takes place in con ⁇ nection with the addition of liquid to the dispersing device 12 (see Figure 2) , which provides an effective intermixing of the additional agents in as early a stage as possible after the concentration.
• Figure 2 shows that additional agents also can be introduced 14a, 14b at later stages in the process. Since the introduction of at least a part of the additional agent (s) favorably takes place at the same time as the introduction 13 of replacing liquid it is of little consequence if the replacing liquid is taken from such a part of the process where the residual content of additional agent (s) could be even high.
• this concentration can be reduced by arranging a suction box 15 under the wire at such a point where a fibre web already has been formed, so that the fibre web functions as a filter.
• This suction box 15 is worked by a light vacuum whereby a careful filtration and a very clean white water is achieved. This filtration reduces the amount of material so that this white water normally can be conducted 16 to an overflow 17 without any need for any additional recovering.

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Citations (4)

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• 2004
  • 2004-06-28 FI FI20040884A patent/FI116575B/sv active IP Right Grant
• 2005
  • 2005-06-28 ES ES05761319.2T patent/ES2458297T3/es active Active
  • 2005-06-28 CN CN2005800216541A patent/CN1997794B/zh active Active
  • 2005-06-28 EP EP05761319.2A patent/EP1766135B1/en active Active
  • 2005-06-28 WO PCT/FI2005/050246 patent/WO2006000649A1/en active Application Filing
  • 2005-06-28 US US11/631,000 patent/US20080257509A1/en not_active Abandoned
  • 2005-06-28 JP JP2007517324A patent/JP4828528B2/ja active Active
  • 2005-06-28 PL PL05761319T patent/PL1766135T3/pl unknown

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