Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
  • D21B1/00—Fibrous raw materials or their mechanical treatment
  • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
  • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
  • D21B1/00—Fibrous raw materials or their mechanical treatment
  • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
  • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
  • D21B1/14—Disintegrating in mills
  • D21B1/16—Disintegrating in mills in the presence of chemical agents

Definitions

• This invention relates to a method of making mechanical and chemi-mechanical papermaking pulp by disintegrating and beating wood material in at least two steps.
• One object of the invention is to carry out the disinte ⁇ gration and beating in such a manner, that the total energy consumption is substantially reduced, as will be be described in the following.
• the beating of cellulose-containing material at low pulp concentration is a method, which has been employed since long in order to improve the paperforming propert ⁇ ies of the fibres. This applies, however, only to fibres free of lignin or substantially free of lignin, such as fibres produced according to the sulphate or sulphite method.
• pulps manufactured mechanically such as thermomechanical pulp (TMP) or chemi-mechanical pulp (CTMP)
• beating at low concentration so-called post- -refining, was not considered applicable other than as a method for increasing the light-scattering capacity of the pulps and for reducing slightly the fibre length and thereby improving the formation at the making of paper.
• thermomechanical pulp with fibre-modifying chemicals Experiments have been carried out previously to treat thermomechanical pulp with fibre-modifying chemicals. It was then found, that by treating the defibered pulp with ozone prior to the refining in a two-step process the en consumption could be lowered by up to 30%. This, however could be achieved only at the expense of the yield.
• the wood material in a first step is coarse-disintegrated at a concentration of above 20%.
• the energy input here shal be at maximum 800 kWh/ton wood material.
• the acid groups included in the wood material thereafter shall be neutra ized entirely or partially, and the material be diluted with water of a temperature corresponding to the softeni temperature of the lignin.
• the dilution water shall have ion strength of at maximum 0.05 mole per litre.
• the coars -disintegrated material then shall be beaten at a concen ⁇ tration of 1-10% with an energy input of totally a maximu of 500 kWh/ton material.
• the present invention is based on the idea that there is a relation between the disintegration of the wood materia to fibres and the way, in which the energy pulses are transferred to the material, i.e. whether the energy puls are transferred in liquid phase or steam phase. Attention also is to be paid to the thermal and physical state of the wood material when the energy pulses are being trans ⁇ ferred.
• the energy input in the first coarse-defibering step must be low.
• the first high concentration step can be at atmospheric pressure or pressurized and be carried out by tearing (shredding), chip pressing, plug screwing (type Impressa- finer or PREX) or by defibering in a refiner.
• the final beating then takes place in one or several step at low pulp concentration, i.e. at a concentration of 1-10%.
• the temperature at the beating shall be at least as high as the softening temperature of the stiffest amorphous wood polymer, that the acid groups of the wood polymers substantially are ionized, and that the ion strength of the process water is sufficiently low.
• FIG. 1 is a flow sheet of an embodiment of the method according to the invention
• Figs. 2—4 are diagrams of properties and energy consump ion of a pulp manufactured according to Fig. 1
• Fig. 5 is a flow sheet of a second embodiment of the invention.
• Figs. 6- ⁇ show properties and energy consumption at the method according to said second embodiment.
• the flow sheet according to Fig. 1 illustrates the manu acture of thermomechanical pulp for newsprint.
• Chips from spruce were steamed in a first step and preh ed.
• the preheated chips then were disintegrated in a pressurized refiner with an energy consumption of 700 kWh/ton.
• 3 kg NaOh were added in the beating zone of the refiner for neutralizing aci groups included in the wood material.
• To the defibered material dilution water with a temperature of 80 C and ion strength of 2.0 mmole/1 was added in order to' obtai a pulp concentration of 3%.
• the pulp then was beaten in five subsequent steps at a specific edge load of 0.3-0.5 ws/ and a total net energy consumption of 150 kWh/ton pulp corresponding to a gross energy consumption of 250 kWh/ ton pulp to a freeness of 150 ml CSF and a mean fibre length (PML) of 1.8 mm, i.e. about equal to TMP-pulp manufactured in conventional manner with an energy con ⁇ sumption of 1750 kWh/ton pulp.
• PML mean fibre length
• the total energy consumption at the method according to the invention thus, was reduced from 1750 to 950 kWh/ ton pulp.
• TMP mean particle length measured according to SIFI pulp measuring system
• the manufacture of TMP according to the invention is com pared in Fig. 2, 3 and 4 with TMP manufactured conventio ally with single-step refining in twin-disc refiner, whi is the least energy consuming TMP-process existing with the present state of art.
• Fig. 2 shows the tensile index as a function of the elec energy consumption. It appears clearly from the Figure, the increase in tensile inde at a certain electric ene consumption is considerably greater for TMP manufacture according to the invention.
• Fig. 3 shows the tear index as a function of the tensil index for TMP according to the invention and convention TMP. It appears that the development of the tear index for the respective TMP is about the same, i.e. at optim ation of the low concentration beating according to the invention the fibre cutting and thereby the serious de ⁇ crease in tear index are substantially entirely avoided which cutting and decrease occur usually at conventiona low concentration beating of mechanical pulps.
• Fig. 4 shows how the light-scattering coefficient (s) develops at conventional TMP and TMP manufactured accor ing to the invention. It appears that the s-development requires as low an electric energy input as the tensile index development, i.e. the saving of electric energy t a certain s-value is of equal size as the saving of el ⁇ ectric energy to a certain tensile index value.
• This example relates to the manufacture of chemi-mechan al pulp (CTMP or CMP) according to the flow sheet shown in Fig. 5.
• CMP chemi-mechan al pulp
• impregnation chemicals which can be sulphites, peroxide, oxygen gas, ozone and/or liquor, can take place prior to the first defibering step, after this step but prior to the final beating, after the fina beating, or at combinations of these. In the flow sheet shown the impregnation is carried out prior to the first defibering step.
• the first defibering step at high concentration is carri out in the same way as in Example 1.
• washing is very essential, so that according to the invention th beating shall take place at low ion strength. The washin therefore, is carried out prior to the final beating. In cases when the chemical treatment is carried out as the last process step, washing takes place even after this step.
• the final beating takes place in the same way as accordi to Example 1, but process temperature and chemical envir ment must be adjusted to the special properties, which t wood polymers have assumed by treatment with impregnatio chemicals. It is essential to pay regard to the number of sulphonic acid groups, which have been introduced by possible sulphite treatment. As an increasing amount of sulphonic acid groups reduces the softening temperature of the lignin, the temperature of the process water can be lower than at the manufacture of TMP-pulp according to Example 1. A sufficiently high temperature at the manufacture of CTMP is 4 ⁇ °C. From a brightness point of view it is advantageous to use the lowest possible temp ⁇ erature. By sodium sulphite treatment both the sulphonic acid groups and the carboxylic acid groups ate ionized from the beginning.
• the pulp then was beaten with a specific edge load of 0.3-0.5 Ws/m in five subsequent steps with a net energy consumption of 150 kWh/ton correspond ing to a gross energy consumption of 250 kWh/ton for obtaining a pulp with a freeness of 250 ml CSF and a mean fibre length (PML) of 1.7 mm, i.e. as a convention ally manufactured CTMP-pulp produced in one step with an energy consumption of 1750 kWh/ton.
• PML mean fibre length
• the en ⁇ ergy consumption was reduced from the conventional 1750 kWh/ton to 850 kWh/ton.
• Fig. 6 the tensile index is shown as a function of the energy consumption for a CTMP-pulp manufactured accor ing to the invention and for pulp manufactured convention ally. Compared at a certain tensile index, for example 40 kNm/kg, conventional refining consumes about 1750 kWh/ ton pulp while at the method according to the invention only about 850 kWh/ton are consumed.
• the light-scattering coefficient of the CTMP-pulp manuf ⁇ actured according to the invention as a function of the energy consumption is shown in the diagram in Fig. 8 compared with conventionally manufactured pulp. It shows here that according to the invention the energy consumpt ⁇ ion to a certain light-scattering index is substantially lower.
• This example relates to the manufacture of highly sulfon- ated CTMP or CMP, i.e pulp containing more than 4 g of bound sulphur per kg wood material.
• Chips from spruce were impregnated with a sodium sulphite solution containing about 120 g of sodium sulphite per litre in an amount corresponding to a charge of about 12%.
• the chips were preheated at a temperature of 140 C for 10 minutes, whereafter they were coarse-disintegrate with an energy consumption of about 400 kWh/ton wood.
• the defibration was carried out in a pressurized chip refiner, and the yield obtained was 93-94%.
• This embodiment is an example of how in the first step extruders can be used for coarse-disintegrating wood material. According to the example an extruder of the type Bivis was used.
• Spruce chips were steamed in the usual manner at 100 C for 10 minutes, whereafter they were fed into a Bivis- machine. At the defibration in the machine 2-3% sodium sulphite solution was charged so that the sulfonation degree of the material amounted to 1.5 g of sulphur per kg wood. The electric energy consumtion was about 400 kWh/ton wood when the material passed through the four compression zones of the twin-rscrew. After discharge, the fibre material was diluted to about 5% pulp concen ⁇ tration at about 70°C, whereafter the suspension was pumped to beating in seven steps in a low concentration refiner. After the fifth beating step, the freeness of the pulp was about 250 ml CSF, the tensile index was
• the total energy consumption for the manufacture of chemi-mechanical pulp (CTMP) to a freeness value of 250 ml CSF by the method according to the invention thus, amounts to 650 kWh/ton, which is to be compared with about 1750 kWh/ton according to the best conventi ⁇ onal technique for obtaining the same freeness value.
• CTMP chemi-mechanical pulp

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Paper (AREA)

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• 1988
  • 1988-05-06 SE SE8801731A patent/SE461103B/sv not_active IP Right Cessation
• 1989
  • 1989-04-05 JP JP50517689A patent/JPH03504256A/ja active Pending
  • 1989-04-05 WO PCT/SE1989/000172 patent/WO1989010998A1/en active IP Right Grant
  • 1989-04-05 EP EP19890905472 patent/EP0413736B1/en not_active Expired - Lifetime
  • 1989-04-05 DE DE89905472T patent/DE68909231T2/de not_active Expired - Fee Related
  • 1989-05-02 CA CA000598482A patent/CA1320067C/en not_active Expired - Fee Related
• 1990
  • 1990-11-05 FI FI905482A patent/FI91787C/fi not_active IP Right Cessation

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