GB2043493A

GB2043493A - Apparatus for separating impurities from stock

Info

Publication number: GB2043493A
Application number: GB8005129A
Authority: GB
Original assignee: Beloit Walmsley Ltd
Current assignee: Beloit Walmsley Ltd
Priority date: 1979-02-16
Filing date: 1980-02-15
Publication date: 1980-10-08
Also published as: GB2043493B; FI72359C; FI800467A; SE8001252L; FI72359B; DE3005518C2; DE3005518A1

Abstract

In known stock purifying apparatus centrifugal force is utilized to separate out the impurities, the impure stock being introduced into the centrifuging chamber of the apparatus at the radially outermost zone and thus requiring to be at a suitable pressure to counter centrifugal forces. In the present apparatus the impure stock is introduced via an inlet (16) in the form of a scroll (30), the scroll leading into the centrifuging chamber (10) at the axially central region thereof where the lowest pressure prevails. The scroll imparts a spiral motion to the stock so that it easily merges with the stock which is being centrifuged by an impeller (20) in an end wall (14) opposite the scroll inlet. Due to the introduction of the impure stock in a low pressure region, running costs are reduced as the impure stock does not require pressurising to the extent required in the relevant prior art. <IMAGE>

Description

SPECIFICATION Improvements in and relating to stock preparation plant This invention relates to stock preparaion plant, and more particularly to apparatus of the type designed to accept stock containing various impurities and to separate it into two or more fractions, whereby the quality of the stock leaving an "accepts" outlet of the apparatus is higher than that of the input, and the impurities are led away through one or more "rejects" outlets.

In one such apparatus the stock is introduced into a cylindrically, horizontal container and is caused to swirl around therein by means of a rotor or impeller carried on one of the end walls of the container. As a result of the movement of the stock, the heavier fraction thereof is thrown outwardly and led away through an outlet, possibly including a trap, for dumping. The lighter impurities tend to take up a central position within the container around or within a vortex or core extending through the encircling stock and are led off through a light rejects outlet arranged centrally in the end wall of the container opposite to that carrying the rotor or impeller. The heavy rejects and the light rejects having been separated out and led away, the remaining stock forms the accepts and passes through a filter in the wall carrying the rotor or impeller for use or for further treatment.In such apparatus the inlet stock containing the impurities is generally introduced at the periphery of the container, often tangentially to assist and increase the swirling motion of the main body of the stock inside the container.

It has been found that, if the inlet stock is introduced into the container at a lower pressure zone thereof, the whole unit can be operated at a lower pressure than was formerly the case. Typical pressures on the casing of a 22" and 55"diameter container during operation are 14 psi and 70 psi respectively, whilst the pressure at the centre of the unit is atmospheric. Obviously, therefore, by introducing the stock at or near the centre of the cylindrcial container, the necessity for pressurizing the inlet is avoided, and running costs are reduced. The centrifugal motion within the container is mainly created by the action of the rotor or impeller, and therefore the displacement of the stock inlet from the casing periphery to the centre of the unit will not greatly affect the motion producing the separation into fractions.Nevertheless by imparting a specific shape in the inlet, the stock movement can be influenced.

According to the present invention, in a horizontal stock separation apparatus having a rotor in one end wall thereof, the stock inlet is in the form of a scroll located substantially centrally in the end wall opposite to the rotor.

The scroll is preferably in the form of a spiral type opening into an annulus, and conveniently may be associated with light rejects outlet which exists through the wall, for instance in the form of a combined single casting.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side elevational view of a stock separation apparatus according to the present invention; Figure 2 is a corresponding top plan view; Figure 3 is an end elevational view taken from the left hand side of Fig. 1; and Figures 4 and 5 are respectively side and end elevations of a combined inlet and outlet casting embodying a scroll similar to that shown schematically in Figs. 1 to 3.

Referring firstly to Figs. 1 to 3 a horizontal cylindrical container 10 has end plates 1 2 and 1 4 which together with the cylindrical casing form a treatment chamber for stock separation. End wall 1 2 carries centrally thereon, a combined inlet and outlet fitting indicated generally by the reference 1 6 designed to permit introduction of stock through an inlet S and to allow the removal of light rejects through an outlet LR. The cylindrical casing of container 10 embodies a heavy rejects outlet 1 8 from which impurities of a substantial nature may be led away.

End wall 1 4 carries an impeller or rotor 20 provided with a drive mechanism 22 to cause movement of the stock within the container 10, and end wall 14 also embodies a filter or screen 24 through which stock free from heavy and light rejects can pass into a small chamber 26 from which the stock may be led away through an accepts outlet 28 in the direction of arrow A.

In previous constructions the impurity containing stock has been led into a container 10 at the periphery of the casing thereof, often in a tangential direction so that incoming stock has joined the swirling contents of container 10 in the outer regions where pressure is greatest due to centrifugal forces. In the present invention the inlet stock is introduced through the end wall 1 2 and substantially central thereof at a point at which the internal pressure of the apparatus is substantially atmospheric. The stock is introduced in the direction of the arrow S through a combined fitting which also serves to allow removal of the light rejects in the direction of the arrow LR.

The combined fitting 1 6 is shown in greater detail in Figures 4 and 5, from which it will be seen that the inlet and outlet, although combined in the same casting, are formed by separate channels within the casing. The inlet develops into a scroll 30 so that as the stock enters the chamber 10 it also has a component of the swirling movement existing within the container 1 0. This scroll 30 surrounds but is isolated from outlet 32 in the form of a straight bore extending through the casing and serving to allow the light rejects to pass out freely therefrom as they enter the vortex or core which tends to be set up within the apparatus when the rotor 20 is operating.

It will be seen therefore that the stock inlet is formed by a scroll in the shape of a spirally wound pipe opening into an annulus and surrounding the central outlet pipe for the light rejects.

Claims

1. A stock preparation apparatus comprising a rotor in one end wall thereof and a stock inlet in the form of a scroll located substantially centrally in the end wall opposite to the rotor.

2. Apparatus as claimed in claim 1, in which the scroll is in the form of a spiral opening into an annulus.

3. Apparatus as claimed in claim 1 or 2, in which the scroll is associated with a light rejects outlet.

4. Apparatus as claimed in claim 3, in which the scroll and light rejects outlet are in the form of a single casting.

5. A stock separation apparatus constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.