Solid material comminution or disintegration – Processes – With application of fluid or lubricant material
Reexamination Certificate
1999-06-24
2001-03-20
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Processes
With application of fluid or lubricant material
C241S023000, C241S028000
Reexamination Certificate
active
06202946
ABSTRACT:
The present invention relates to a method and device for defibrating a fibre-containing material, as disclosed in the introduction of the appended independent claims. The invention also relates to the use of a multi-peripheral pin mill for defibrating fibre-containing material.
The concept “fibre-containing material” is later to be understood as a wide concept comprising wood chips, grass and other fibre-containing materials originating from the vegetable kingdom, which have been crushed to pieces of appropriate sizes so that they can be fed into the pin mill. The concept also includes inorganic fibres, such as mineral and glass wood fibres.
The concept “defibration” covers the separation of fibres from each other, wood or other raw materials in the vegetable kingdom, or other components. In this text, the concept also covers the fibrillation of separate fibres.
In principle, mechanical pulp is manufactured in two ways, i.e. by grinding logs of wood to ground pulp against pulp-stone, or by defiberizing wood chips in a disc refiner, or pulper; in this case, the pulp is called refined mechanical pulp. Both these processes may be carried out either in atmospheric pressure or under pressurized conditions. In the latter case, one speaks of pressure ground pulp, and correspondingly thermo-mechanical pulp (TMP). The principle of both the processes is to separate the wood fibres mechanically and with the help of heat generated in connection with the treatment. The mechanical energy applied to the fibre material is changed into heat, softening the intermediate lamella (which is lignin), and thus promoting defibration. By pressurizing the processes, the softening of the intermediate lamella is promoted.
Both the grinding and defibration techniques force the fibre bundles separated from the fibre material to become subject to hydraulic forces. In addition, the fibres have to travel out of the pulper through a small discharge gap. The following drawbacks may be said to relate to the said known methods:
power consumption is big, because the fibres are to a great extent separated by heat;
small limited capacity;
the flow through the pulper has to be promoted additionally by pressurized forced feed;
a further drawback related with defibration solutions is that transverse blades promoting defibration and fibrillation essentially reduce production.
When fibres are used in special products such as concrete or gypsum based sheet products, the fibres needed are dispersed (in case of chemical pulp) e.g. from high-quality chemical pulp dried in ball mills in a sheet form, which is expensive. Sometimes also waste paper is used.
In the cleaning of waste paper fibres (de-inking process), the dispersion process is relatively ineffective when carried out in big tanks and using fast rotating blades. Dispersion and separation of printing ink pigment particles take place in the collision point of the blades, but this “finished product” circulates and burdens the whole process until all the fibres are separated from each other, and even the last pigment particles are detached from the fibres (which is hardly ever achieved). In this overlong process, the finished products have to undergo the same process over and over again, and quite unnecessarily, so that the fibres are further quite unnecessarily cut into pieces.
Thus, there has prevailed a need to develop a new and efficient method and device for defibrating fibre-containing material.
The object of the present invention is to provide a new and efficient method and device for defibrating fibre-containing material.
This object is achieved by a method and device in accordance with the invention, which are characterized by what is disclosed in the characterizing part of the appended claims.
Devices operating with the pin mill principle are previously known, for example, from the Danish patent publication DK 104778, and the Finnish patent applications FI 945945, FI 946048, and FI 955474. Characteristic of these devices is that two concentric rotors equipped with collision surfaces are fitted into a housing. The rotors are fitted within each other in the housing and arranged to rotate to opposite directions. According to another alternative, a rotor equipped with collision surfaces and a stator concentric with the rotor and equipped with collision surfaces are fitted into the housing.
A feed orifice opening to the centre of the rotors or the rotor and stator are arranged at the end of the housing, and a discharge orifice opening to the periphery of the outermost rotor or stator is arranged on the wall of the housing.
The fibre-containing material is led to the housing via the feed orifice and is made to flow in the housing together with a suspension produced by air or added liquid through the collision surfaces of the nested rotors or the nested rotor and stator to the discharge orifice and further as a discharge flow out of the housing.
Defibration may be carried out either without added water or by adding water. The used liquid is suitably either water or an aqueous solution.
The defibration process may be processed in many ways. The fibre-containing material (wood chips) may be pretreated by an aqueous solution which includes peroxide, sodium carbonate or sodium hydroxide. By using peroxide, it is possible to simultaneously bleach the product. Alternatively, the treatment with additives may be performed solely in the pin mill, or the said treatment methods may be combined.
For promoting the defibration, it is also possible to subject the fibre-containing material to a pretreatment with aqueous vapour of about 130° C., when desired, before the fibre-containing material is led to the pin mill. Alternatively, or in addition to this pretreatment, defibration in the pin mill may be carried out in pressurized conditions, advantageously in such an overpressure (about 1.7 bar) that a vapour saturation temperature of about 130° C. is achieved.
According to an embodiment of the invention, the established fibre suspension is in total or partly circulated back to the pin mill one time or several times.
The method according to the invention is very well suited for the defibration of different grasses. Defiberizing grasses with present methods is problematic, because the grass walls contain a large amount of silica minerals, generating indissoluble deposits in the process equipment. When processing grasses with a sulphate cellulose method, it is not possible to effectively recover black lye because of this problem. By treating this kind of grass material in a pin mill, the silica minerals are released, whereafter they can be separated from the fibre-containing material. The obtained fibre material may be used as such as mechanical pulp, or it may be processed further in the pulping process.
The method of the invention is very well adapted for use in the treatment of waste paper, in which the fibres are separated from printing ink pigments. In the re-use of waste paper (de-inking), the dispersion of fibres and the separation of ink pigment take place in a very short time as compared with the old methods, and each “unit” is subjected to an exactly identical treatment and made “first time right” without unnecessary inconvenient repetitions.
According to one embodiment, one or more mineral components may be fed into the pin mill together with the fibre-containing material.
For example, if the fibre-containing material consists of wood chips or mechanical, semi-chemical or chemical pulp suitable for the manufacture of paper, the mineral component may be a filler adapted for paper manufacture, e.g. titanium dioxide or the like. The problem with known processes with titanium dioxide is weak retention which again leads to operating troubles, environmental stress, and unprofitable production economy. By treating the fibre-containing material in the pin mill together with a mineral component, a good contact is provided between the fibre and the mineral particle so that the said problems are eliminated or considerably reduced. When the fibre-containing material is treated in the p
Lydon James C.
Megatrex Oy
Rosenbaum Mark
LandOfFree
Method and apparatus of defibrating a fibre-containing material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus of defibrating a fibre-containing material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus of defibrating a fibre-containing material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2548139