FEEDING ELEMENT FOR FIBROUS MATERIAL

Abstract: A feeding element intended for refiners with two opposed refining means (11, 12), one of which is stationary and one rotary, which are provided with refining elements (14, 15), which between themselves form a refining gap (17) with a refining zone (16) for working lignocellulosic fibrous material. A feeding device (20, 22) is located centrally inside the refining gap (17). The feeding element (30) is intended to be placed on the rotary refining means (12) in the refining gap (17) directly outside the feeding device (20, 22). The feeding element (30) is formed with at least one feeding bar (31), where the upper edge (33) of each feeding bar projects out on at least one side of the bar.

Description: Feeding element for fibrous material This invention relates to a device for working lignocellulosic fibrous material in a refiner with opposed refining means rotating relative to each other, one of which is stationary and one rotary, provided with refining elements, which between themselves form a refining gap with a refining zone for working the material. The material is supplied through a central opening in the stationary refining means to a feed zone located radially inside the refining zone. The invention, more precisely, relates to a feeding element for the material, which is intended to be placed directly outside a central feeding device on the rotary refining means. The feeding element according to the invention can be used in a refiner for the manufacture of various types of mechanical pulps, such as refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemi- mechanical pulp (CMP) and chemi-thermomechanical pulp (CTMP). The starting material can be wood chips or more or less worked pulp. In the inner portion of the feed zone the effect of the centrifugal force on the supplied material is low. This implies, that the material supplied through the opening in the stationary refining means is not fed sufficiently rapidly through the feed zone to the outside located refining zone. As a result therof, the material can clog in the feed zone, which results in friction losses and non- uniform feed, which in its turn deteriorates the pulp quality. In order to overcome these problems, mechanical feeding devices can be arranged in the feed zone. But even if the material by means of central feeding devices is transported out through the feed zone, problems can arise when it enters the refining zone in the refining gap. The material can there be braked and subjected to an ineffective mechanical action, which causes heat development and not the desired working of the material. This results in unnecessarily high energy consumption. The feeding element according to the present invention offers a solution of the aforesaid problems, in that it brings about a continued effective feed of the material and at the same time its acceleration from the feed zone and a distance into the refining gap. Due to the effective feed, the energy consumption in the refiner is reduced. The refining element according to the invention comprises at least one feeding bar where the upper edge of each feeding bar projects out at least on one side of the bar. The feeding element is intended to be placed on the rotary refining means in the refining gap directly outside the central feeding device, which can be attached on the rotary refining means or be a separate screw feeder extending in to the refining gap between the refining means. The feeding bar or bars of the feeding element can be angular in relation to the radius in order bring about optimum feeding. Alternatively, the feeding bar or bars can be radial in order to allow reversing with maintained feeding. In this case the upper edge of the feeding bar projects out symmetrically on both sides of the bar. The characterizing features of the invention are apparent from the attached claims. The invention is described in greater detail in the following by way of embodiments thereof, with reference to the accompanying drawings, in which Fig. 1 is a cross-section through a refiner with a feeding element according to the invention; Fig. 2 shows a central feeding device; Fig. 3 is a section according to HI-III in Fig. 2; Fig. 4 is a section according to IV-IV in Fig 2; Fig. 5 shows an embodiment of a feeding element; Fig. 6 is a section according to VI- VI in Fig. 5, and Fig. 7 shows a variant of the embodiment shown in Fig. 6. The refiner shown in Fig. 1 comprises a refiner housing 10, in which a stationary refining means 11 (in this case the end wall of the refiner housing) and an opposed rotary refining means 12 attached on a rotary shaft 13 are provided. The refining means 11,12 are provided with refining elements 14 and, respectively, 15, which between themselves form a refining zone 16 in a refining gap 17. The refimng gap 17 comprises a feed zone 18 located inside the gap. The stationary refining means 11 is formed with a central feed opening 19 for the material to be worked. A screw feeder 20 for the material is connected to the feed opening 19. The refiner housing 10 is provided with an outlet 21 for the material passing through the refining gap where it is worked. On the rotary refining means a central feeding device 22 is located, which comprises a circular disk 23 with strips 24 extending from a position close to the centre radially outward to the circumference of the disk. The number of strips can be one or more, preferably 2-4. The strips along the greater portion of their upper edges are provided with a roof 25, which projects out symmetrically on both sides of the strips. The disk 23 is formed with a hub 26, from which three radial strips 24 extend. The roof 25 leaves an opening at the hub and follows the strips 24 outward. The height of the strips decreases outward in order to adapt to the outside located and outward tapering refining zone 16. The disk 23 has a diameter corresponding to the diameter of the feed opening 19. The feeding device 22 is designed symmetrically in order to bring about feed in both rotation directions. Alternatively, the feeding device can be designed for rotation in only one direction. It is also possible, that the central feeding device consists of a screw feeder 20, which then extends in through the feed opening 19. A feeding element 30 is located on the rotary refimng means 12 in the refining gap 17 directly outside the feeding device 22. The feeding element 30 is formed with one or several radial feeding bars 31. The feeding element can extend as a zone around the entire refining means 12 or consist of a portion of a zone and together with other feeding elements extend around the refining means 12. According to Fig. 5, the number of feeding elements is three, but also other numbers can be suitable. In order to bring about an increased feeding effect, the feeding bars 31, instead, can be angular in relation to the radius. This implies, however, that they operate only in one rotation direction. The feeding bars 31 of the feeding element 30 are formed with upper edges 33 projecting out symmetrically on both sides of the bars. The upper surface of these upper edges 33 shall be flat, and the feeding bars 31 extend across the refining gap 17 to the opposed stationary refining means 11, the corresponding zone of which shall have smooth surface. The distance between the upper edges 33 of the feeding bars and the opposed refining means 11 shall be short. The feeding element 30 shall be so placed on the rotary refining means 12, that a feeding bar 31 is located directly in front of a strip 24 on the feeding device 22. According to Fig. 6, the projecting upper edges 33 of adjacent feeding bars 31 are arranged spaced from each other, so that they bridge grooves 32 only partially. According to the variant shown in Fig. 7, these upper edges, instead, are designed so as to totally bridge the grooves 32, so that closed radial channels are formed. Radially outside the feeding elements 30 both refining means 11,12 are provided with refining elements for working the material. The refiner shown has plane refining means, but it is also possible to give the outer portion of the refining gap conical shape. Alternatively, the radially outer portion of the feeding element 30 can be provided with conventional bars for working the material in co-operation with bars on the opposed stationary refining means 11. The number of conventional bars shall then be higher than the number of feeding bars. The material, which by the screw feeder 20 is fed into the refiner, is caught under the roof 25 and accelerated outward along the strips. The material is transferred from the feeding device 22 to the grooves 32 of the feeding element 30 which effectively move the material into the refining zone 16 of the refining gap 17. Owing to the projecting upper edges 33 of the bars 31, the feed along the grooves 32 takes place with the effect of the centrifugal force without being braked against the opposed stationary refining means 11. The material thereby is transferred effectively and uniformly to the refining zone 16 without being disturbed by rearward flowing steam. The working takes place longer away from the centre and thereby at a higher relative speed between the refining means 11,12. On a whole, this implies reduced specific energy consumption for working the material to pulp. The alternative with an outer zone of conventional bars on the feeding element 30 implies, that the transition from feeding to refining proceeds softer, which can result in a more uniform material flow through the refiner. The invention, of course, is not restricted to the embodiments shown, but can be varied within the scope of the patent claims.

Claims: Claims 1. A feeding element intended for refiners with two opposed refining means (11,12), one of which is stationary and one rotary, which are provided with refining elements (14,15), which between themselves form a refining gap (17) with a refining zone (16) for working lignocellulosic fibrous material, and where a feeding device (20,22) is located centrally inside the refining gap (17), characterized in that the feeding element (30) is intended to be placed on the rotary refining means (12) in the refining gap (17) directly outside the feeding device (20,22), that the feeding element (30) is formed with at least one feeding bar (31), where the upper edge (33) to each feeding bar projects out on at least one side of the bar. 2. A feeding element as defined in claim 1, characterized in that each feeding bar ( 31 ) i s located radially with upper edges (33), which project out symmetrically on both sides of the bar. 3. A feeding element as defined in claim lor2, characterized in that it is formed with several feeding bars (31), where the projecting upper edges (33) of adjacent bars (31) are arranged spaced from each other. 4. A feeding element as defined in claim lor2, characterized in that it is formed with several feeding bars (31), where the projecting upper edges (33) of the bars (31) bridge grooves (32), so that closed channels are formed. 5. A feeding element as defined in any one of the preceding claims, characterized in that the feeding bars (31) extend over the entire feeding element (30), counted in radial direction. 6. A feeding element as defined in any one of the claims 1-4, characterized in that the outer portion of the feeding element (30), counted in radial direction, is provided with conventional bars for working the material. 7. A feeding element as defined in any one of the preceding claims, characterized in that it extends as a zone around the entire refining means (12). 8. A feeding element as defined in any one of the claims 1-6, characterized in that a plurality of bars together are arranged to form a zone around the refining means (12).

Inventors: VIRVING NILS, VIRVING, NILS
Applicants: SUNDS DEFIBRATOR IND AB, VIRVING NILS, SUNDS DEFIBRATOR INDUSTRIES AB, VIRVING, NILS
Application year: 1998
Main classification: D21B1
IPC codes: B02C7, D21B1, D21D1