Solid material comminution or disintegration – Apparatus – Cooperating comminuting surfaces
Reexamination Certificate
1999-08-23
2001-03-27
Ostrager, Allen M. (Department: 3725)
Solid material comminution or disintegration
Apparatus
Cooperating comminuting surfaces
C241S246000, C241S261200, C241S261300
Reexamination Certificate
active
06206309
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for treating lignocellulosic fibrous material in a refiner with opposed refining means rotating relative to each other, one of which is stationary and one rotary, and which are preferably provided with refining elements, which form a refining gap with a refining zone for working the material therebetween. The present invention also relates to such method and apparatus in which the material is supplied to a feed zone located radially inside the refining zone. The present invention also relates to a feeding device for the lignocellulosic material.
The present invention more particularly relates to the manufacture of various types of mechanical pulps, such as refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemi-mechanical pulp (CMP) and chemi-thermo-mechanical pulp (CTMP). The starting material in accordance with the present invention can be wood chips, one-year plants as wheat, straw, bagasse or more or less worked pulp.
BACKGROUND OF THE INVENTION
The working of fibrous material in the known refiners most often is carried out in an ineffective manner. A significant portion of the energy input to these refiners is used for transporting the fibrous material through the refiner, wherein friction and heat losses occur which do not result in the alterations of the fibrous material which are required for developing the pulp quality and for making the refining process effective. It is therefore apparent that the energy consumption is higher than that required for achieving the desired mechanical working; i.e., the desired pulp quality.
SUMMARY OF THE INVENTION
In accordance with the present invention, this and other problems have now been solved by the discovery of a method for refining lignocellulosic material between a pair of relatively rotary refining elements forming an annular outer refining zone and a central feed zone therebetween, the method including feeding the lignocellulosic material to the central feed zone, accelerating the lignocellulosic material through the central feed zone towards the annular outer refining zone without lignocellulosic material build up in the central feed zone and substantially without working the lignocellulosic material in the central feed zone, the density of the lignocellulosic material in the central feed zone being a maximum of about 10 kg/m
3
, and mechanically working the lignocellulosic material in the annular outer refining zone wherein the relatively rotary refining elements have a relative speed of greater than about 50 m/sec. Preferably, the density of the lignocellulosic material in the central feed zone is a maximum of about 1 kg/m
3
.
In accordance with the present invention, apparatus has also been discovered for feeding lignocellulosic material to a refiner including a pair of relatively rotary refining members including a corresponding pair of refining elements forming a refining gap and comprising an annular outer refining zone, and a central feed zone therebetween, a central feed conduit having a predetermined diameter for feeding the lignocellulosic material to the refiner, the apparatus including a feed member for mounting in the central feed zone in front of the central feed conduit, the feed member including a front axial screw and at least one substantially radial rear wing displaced rearwardly from the front axial screw, the front axial screw having a diameter substantially corresponding to the predetermined diameter, and the at least one rear wing adapted to extend into the refining gap substantially to the annular outer refining zone. Preferably, the pair of relatively rotary refining members includes a stationary refining member and a rotary refining member, the central feed conduit being disposed in the stationary refining member and the feed member being disposed on the rotary refining member. In a preferred embodiment, the apparatus includes between about 2 and 4 of the substantially radial rear wing members.
In accordance with oen embodiment of the appartus of the present invention, the at least one rear wing member includes an outer end which is curved from the intended direction of rotation of the rotary refining member.
The present invention offers a solution to the above problems, in that the residence time of the material in the feed zone is shortened, and substantially without mechanical working the cellulosic material passes through the feed zone to the radially outer refining zone. The residence time should be less than about 2.5 sec, preferably less than about 1 sec.
By means of a central feeding device the cellulosic material is fed in and accelerated outward without material build-up in the feed zone. In this manner, the material density in the feed zone is restricted to a maximum of about 10 kg/m
3
, and preferably to a maximum of about 1 kg/m
3
. In this way, contact of the material with the refining means in the feed zone is reduced, and thus the energy consumption in the form of frictional heat is reduced. Any proper mechanical working does not take place in the feed zone, and the energy consumption in this zone preferably should be less than about 5% of the total energy consumption.
Instead, the energy input is transferred to the refining zone, where the relative speed between the refining elements is now quite high, and preferably exceeds about 50 m/sec even in the inner portion of the refining zone.
REFERENCES:
patent: 3902673 (1975-09-01), Berggren
patent: 3957214 (1976-05-01), Berggren
patent: 4220290 (1980-09-01), Johansson
patent: 4253613 (1981-03-01), Reinhall
patent: 5040736 (1991-08-01), Obitz
patent: 150727 (1984-08-01), None
patent: 467 463 (1992-07-01), None
Danielsson Ove
Johansson Ola
Svedberg Peter
Hong William
Lerner David Littenberg Krumholz & Mentlik LLP
Ostrager Allen M.
Valmet Fibertech Aktiebolag
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