Patent Application
20080272216
(Not Applicable)
The present invention relates to a refiner for refining a fibrous slurry and, more particularly, to a refiner including inlet and outlet structure that effects better performance.
Refiners for a fibrous slurry are used for developing fiber to increase surface area and fibrils and for cutting fibers to reduce their length. Low consistency refining was generally understood with respect to lignocellulosic material, as referring to a refiner fed by pumped slurry having a consistency of about 2-5% fiber. Modern pumping techniques accommodate consistency up to about 16% fiber (sometimes referred to as “medium consistency”). In these types of refiners, flow control is accomplished on the discharge of the machine by a single throttling valve in a single discharge line. This is in contrast to the control of so-called high consistency refiners, where the feed is metered by a device upstream of the refiner.
Conventional two zone refiners maintain a common discharge from both refining zones and therefore, small differences in the refiner plate bar depth between the two zones or other factors can change the relative pumping capability of each zone. This can result in one zone pulling more than one-half of the total flow being supplied to the refiner, which then provides uneven refining in the two zones since the thrust in the zones and the power applied is equal. Another deficiency is that the zone with the lower flow will have a smaller operating gap and therefore have a greater tendency for plate contact and increased wearing of the refining plate surfaces. This problem of uneven flow is particularly noticeable at material flows that are at the minimum volumetric capacity of the machine where operation may be desirable due to the lower refining intensities available at the lower flows.
Conventional refiners additionally require space between an inlet and the grinding surfaces in order to accelerate the slurry for processing. The required space reduces the effective work area of the machine.
It would be desirable to accelerate the incoming flow more closely to the geometry of the rotating plates of the refiner. It would also be desirable to distribute the incoming flow such that it is more uniformly distributed annularly around the inner periphery of the refining zone. It would also be desirable to configure the refiner discharge such that there would be minimal acceleration required to discharge the slurry flow.
In an exemplary embodiment, a fibrous slurry refiner includes a casing, a rotor secured to a rotor shaft, the rotor being disposed within the casing and rotatable via the rotor shaft, and a first plurality of grinding surfaces secured to the rotor and a second plurality of grinding surfaces disposed facing the first plurality of grinding surfaces and being fixed in the casing. An inlet housing made up of an inlet plate, an axial cylinder and a spiral inlet opening for each of the plurality of grinding surfaces directs the fibrous slurry toward a set of facing first and second grinding surfaces and imparts a rotary flow to the fibrous slurry. The inlet axial cylinder is preferably substantially circular, wherein a spiral inlet opening is positioned tangentially relative to a center of inlet plate. The inlet housing may include a spiral channel extending from the inlet opening to the center of the inlet plate. In this context, the center of the inlet defines an axial channel that directs the fibrous slurry toward the grinding surfaces.
The refiner may include a first set of first and second grinding surfaces on one side of the casing and a second set of first and second grinding surfaces on an opposite side of the casing, wherein the refiner includes a pair of inlet plates, one on each side of the casing. In this regard, the casing may include a pair of outlet channels, one on each side of the casing, the outlet channels being positioned to receive flow from the grinding surfaces. The outlet channels are preferably configured to minimize a disturbance on the casing caused by discharge of the flow. In this context, the pair of outlet channels may be substantially volumetrically equal. In one arrangement, the casing includes a substantially circular housing disposed surrounding the grinding surfaces, wherein the outlet channels are defined along an outer circumference of the substantially circular housing.
In another exemplary embodiment, an inlet plate for a fibrous slurry refiner includes an inlet opening that imparts a rotary flow to the fibrous slurry.
In yet another exemplary embodiment, a casing for a fibrous slurry refiner includes a pair of outlet channels, one on each side of the casing, wherein the outlet channels are configured to minimize a disturbance on the casing caused by discharge of a refined slurry.
In still another exemplary embodiment, a method of refining a fibrous slurry in a refiner includes the steps of flowing the fibrous slurry through a pair of inlet plate openings; accelerating and imparting rotary flow to the fibrous slurry via the inlet housing; directing the accelerated and rotary flow fibrous slurry to a plurality of grinding surfaces; and refining the fibrous slurry with the grinding surfaces.
These and other aspects and advantages of the present invention will be described in detail with reference to the accompanying drawings, in which:
It should be understood that the present invention is applicable to a variety of refiners for mechanically treating a slurry of fibrous material, wherein the machine has at least two refining zones located substantially symmetrically on either side of a vertical plane perpendicular to the refiner shaft. A refiner 10 of this type is shown in
An inlet plate 26 is provided on each side of the plane 20. The inlet plates 26 direct the fibrous slurry toward the grinding surfaces 16, 18 and facing grinding surfaces 68, 60.
In this manner, the inlet plates 26 serve to expand an effective work area of the machine. That is, with the conventional structure, space is required to accelerate the pulp before reaching the grinding surfaces. With the inlet opening 28 on a tangent of the inlet plate 26 in conjunction with the voluted channel 30, the inlet plate 26 imparts a centrifugal velocity and rotary flow to the slurry, thereby improving the performance of the refiner.
With reference to
With the structure and operation of the refiner described herein, the dual inlet plate design serves to maximize available edge length and additionally keeps pulp inlet flow velocities within limits while fitting within a reasonable geometry window. Moreover, the dual inlets prevent suspected side-to-side dewatering effects through disc rotor ports. The tangential inlet configuration facilitates optimization of pulp flow to the inner diameter without re-acceleration of pulp and potential dewatering. Moreover, the configuration allows spiral inlet geometry in two planes to accommodate space necessary to reinforce plate holder for low deflections. The tangential and circumferential discharge configuration facilitates a force equilibrium on opposite sides of the casing, thereby improving refiner performance.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/915,802, filed May 3, 2007, the entire content of which is herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60915802 | May 2007 | US |
