The invention relates to a disc refiner having a direct coupled feed screw press delivering pulp to a central cavity in the disc refiner.

In such a disc refiner pulp consistence is regulated by means of the screw press which is directly coupled to the refiner. The pulp is fed into the screw press more or less as a pulp plug delivered into a centralcavity in the disc refiner. During refining energy is released in the form of heat, whereby steam is developed between the refiner discs. A portion of this steam will go out with the treated pulp, some steam will go out with the treated pulp, some steam will, however, tend to escape upstream. While the pulp is delivered as a plug like mass in the screw press this steam cannot readily escape upstream, as for instance in a conventional high con¬ sistence refiner.

The object of the present invention is to provide for an escape passage for steam tending to escape upstream in a disc refiner to which pulp is directly delivered through a screw press.

The invention therefor provide for a disc refiner having a direct coupled feed screw press delivering pulp to a central cavity in the disc refiner, a steam escape passage from said cavity extending out through the press screw of said screw press.

Preferably, the press screw may have a hollow shaft through which said steam may escape. The press screw may further preferably end at a distance from the opposing disc in the cavity area so that the steam may expand in the central cavity. In a preferred embodiment the press screw may have a central coaxial extension comprising the steam escape passage, said extension extending into

the central cavity and centrally into a pulp beater arranged in the central cavity. A such construction enhances separation of pulp and steam in this area thereby avoiding that pulp enters said steam escape passage. If the disc refiner is of the type having radially extending wall portions in the central cavity, this will enhance the separation of steam and pulp.

The pulp plug delivered from the screw press will enter the central cavity in the disc refiner. In this cavity the pulp flow will be allowed to equalize.

Objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings in which a disc refiner and feed screw press is disclosed in longitudinal section.

The disclosed disc refiner 1 is of conventional construction and has two refiner zones. A screw press 2, also known per se, is directly coupled to the disc refiner 1 and deliver pulp into a central cavity 5 of the disc refiner. For a more detailed description of the disclosed disc refiner reference is made for instance to SE-B 7808424-1, cfr. also NO-application No. 841840.

The conventional screw press 2 includes a conical screw 3 surrounded by a screen 4.

A pulp beater 6 is arranged in the central cavity and is mounted on the rotor shaft 7 of the disc refiner for rotation therewith.

As shown in the drawing the conical screw 3 terminates at a distance from the opposite disc in the central cavity. The screw has, however, a centrally coaxial extension 8 extending into the central cavity and into the pulp beater 6. The screw 3 is hollow in that it includes an

axially extending bore 9. In the outer end portion (to the right in the Figure) of the screw 3 a bore 10 extends transversally crossing said axial bore 9 thereby providing a passage connection to a chamber 11. Steam from the central cavity 5 may escape through the axial bore 9 and into the chamber 11 through the transversal bore 10. From the chamber 11 steam may flow out through a conduit 12.

The disclosed disc refiner 1 is adapted for refining of medium consistence chemical pulp. Pulp is delivered to the screw press 2 as shown with arrow 13. During the process the screw 3 will remain filled with pulp and will deliver pulp centrally in the disc refiner 1, that is in the central cavity 5. By increased energy expenditure, heat will develop, resulting in the developing of steam between the refiner discs. Such steam may escape upstream through the axial bore 9, transversal bore 10 and out through chamber 11 and conduit 12.

The extension 8 allows for a separation of pulp and steam in the central cavity 5. The radial wall portions 14 in the refiner will also add to a such separation effect.

The invention provides a controlled evacuation of steam from a disc refiner. The escaping steam may be directed to any conventional place through conduit 12.