AU683531B2

AU683531B2 - Crusher

Info

Publication number: AU683531B2
Application number: AU14922/95A
Authority: AU
Inventors: Kurt Eidner; Johannes Krecher; Tieu Le Van
Original assignee: LENTJES KRAFTWERKSTECHNIK; Babcock Lentjes Kraftwerkstechnik GmbH
Current assignee: Babcock Lentjes Kraftwerkstechnik GmbH
Priority date: 1994-04-15
Filing date: 1995-03-17
Publication date: 1997-11-13
Anticipated expiration: 2015-03-17
Also published as: AU1492295A; DE4412924A1; RO115702B1; GR1002373B; YU5495A; CN1040183C; CN1124675A; SI9500127A

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant: BABCOCK LENTJES KRAFTWERKSTECHNIK GmbH Invention Title:

CRUSHER

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The following statement is a full description of this invention, including the best method of performin~g it known to me/us: Crusher The invention concerns a crusher with the features of the generic part of patent claim 1.

In mills of this type (VBG Kraftwerkstechnik 70 (1990) pp. 587- 590) the crusher wheel, acting as a blower, draws in hot flue gases from a furnace, which gases dry during the comminution the material to be ground fed to the mill. Provided that a beater part is included before the crusher wheel on the same mill shaft, the flue gases and the material to be ground are mixed w*th each other to a certain extent before the reach the crusher wheel. If such a beater part is not present, as is the case in pure crushers of the generic type, there will be a danger that the flue gas flow and the material to be ground S will impact the crusher wheel unevenly distributed. The consequence of this will be that some axial zones of the crusher wheel are impacted by the hot flue gas and others by the material to be ground. As a result of this some zones will eoeoo be subjected to a heavy thermal load and others to a strong erosion. Due to this uneven load the crusher wheel cannot be used in an optimum manner as far as the mill's throughput, S stability and consistency are concerned.

The object of the invention is to distribute the load on the crusher wheel of the generic mill in a more uniform manner.

.:ee.

e The invention achieves this objective in a generic mill by the characterising features of patent claim 1. Advantageous developments of the invention are subject matter of the subsidiary claims.

The protrusions of the agitators cause a turbulence of the flow of the flue gas/material to be ground at their entry into the crusher wheel. As a consequence, the material to be ground will be evenly distributed in the flue gas flow and over the crosssection of the crusher wheel. In this manner the crusher wheel will be more uniformly loaded as far as temperature and erosion i are concerned; consequently the crusher wheel can have an optimum design and the operating time of the mill can be extended.

An embodiment of the invention is illustrated in the drawing and will be explained in detail below. The following is shown in: Fig.l a longitudinal section of the crusher, and Fig.2 detail Z of Fig.l.

The crusher illustrated is used for the comminution of raw lignite while applying hot flue gas as drying and carrier gas.

The crusher has a mill housing 1 with a funnel-shaped entry section 2 and an exit section 3. A dust duct (not illustrated) leading to a coal dust burner is connected to the exit section S 3 via a transition piece or a separator. A crusher wheel 4 rotates in the mill housing 1, which crusher wheel is provided on a unilaterally mounted mill shaft 5. The mill shaft 5 is driven by a motor 6. In the vicinity of the crusher wheel 4 the mill housing 1 is provided with a cladding on its inside.

The crusher wheel 4 has an axial inlet and a radial outlet and comprises two discs 7, 8 joined with each other, between which agitators 9 are provided. The rear disc 8 is secured on the mill shaft 5 and is protected by a baffle plate 10 placed in front of it. The front disc 7 has an annular shape, while the opening of the disc 7 represents the axial inlet of the crusher wheel 4, into which the inlet section 2 of the mill housing 1 merges. The agitators 9 are made of wear-resistant plates, which are basically flat and by means of holders are secured on the discs 7, 8 of the crusher wheel 4.

The material to be ground, e.g. raw lignite, is fed to the mill through a chute which is connected to the inlet section 2 of the mill housing i. At the same time the crusher wheel 4, acting as a blower, draws in hot flue gases through the chute

I

-3 from the furnace of a boiler cinnected to it as a drying and carrier gas to dry the material to be ground during the comminution. The material to be ground slides through the funnel-shaped inlet section 2 up to the rear section of the crusher wheel 4. The material to be ground is seized by the agitators 9 and is thrown against the baffle plate in the mill housing until it is comminuted to that extent, that it is taken along by the carrier gas and discharged through the exit section 3. Due to this charging of the crusher wheel 4 with the material to be ground, the agitators 9 on that part which is facing the rear disc 8 are subjected to an increased attack by erosion. At the same time the hot carrier gas comes into contact preferably with the front section of the agitator 9.

Therefore the load on the crusher wheel 4 is quite uneven as far as temperature and erosion are concerned. To prevent this oe disadvantage, the agitators 9 are constructed as described *e below.

The inward facing edge of the agitator 9, which extends parallel to the mill shaft 5, projects inwards on a portion of its width and protrudes into the inlet cross-section of the Scrusher wheel 4. The protrusion 11 formed in this manner is situated on that part of the agitator which is facing the inlet or annular disc 7 of the crusher wheel 4. The protrusion 11 can be formed integrally with the agitator 9 or welded on subsequently. The width of the protrusion 11 is approximately 1 S to 40% of the width of the agitator 9. Preferably a value of to 20% is chosen. The height of the protrusion 11 is 10 to 100% of the total height of the agitator 9. The side edges of the p-otrusion 11 can be at a right angle to the mill shaft 5 or at an angle relative to it. As Fig.2 shows, the protrusion 11 may have a trapezoidal shape.

The protrusions 11 which protrude into the inlet cross-section of the crusher wheel 4 pick up a portion of the fed in material to be ground, due to which the agitators 9 engage the material to be ground over their entire width, so that the entire agitator 9 comes into contact with the material to be ground.

Simultaneously the protrusions 11 cause turbulence in that portion of the material to be ground which is picked up by them as well as in the hot carrier gas introduced with it. It dries the whirling raw material to be ground in this region and is cooled off by this, so that the drawing off of unused hot strands of carrier gas will be prevented and the carrier gas will obtain a more uniform temperature over the cross-section of the crusher wheel 4.

The exact position of the protrusions 11 on the inlet side of the agitator 9 depends from the operating conditions of the mill. Therefore the protrusion 11 can be adjustable in the longitudinal direction of the agitator 9. The position is to be chosen so, that the crusher wheel 4 would be impacted as evenly as possible by the material to be ground and the hot carrier e. S gas. According to the drawing the protrusion Ii commences very m close to the front annular disc 7 of the crusher wheel 4. This *e S position is considered as particularly advantageous.

Depending on the design of the crusher the crusher wheel 4 can be equipped with eight to sixteen agitators 9. All these agitators 9 may oe provided with protrusions 11. It is, S however, also feasible that only some agitators 9 would have a protrusion 11. If the number of agitators 9 is even, at least two agitators, situated opposite each other, should have a protrusion 11 to prevent an imbalance of the crusher wheel 9.

Although such a symmetrical arrangement is advantageous, due to oeeo the heavy weight of the crusher wheel 4 certain imbalances can be accepted by an asymmetrical arrangement of the agitators provided with protrusions 11.

I I

Claims

1. Crusher which has a crusher wheel secured on a mill shaft inside a mill housing, which has an axial inlet and a radial outlet and wherein agitators are arranged between two discs, characterised in that the inward facing edge of the agitator on a portion of the width of the agitator protrudes inwards into the inlet cross-section of the crusher wheel and that the protrusion faces the inlet of the crusher wheel and has a width which is 1 to 40% of the width of the agitator.

2. Crusher according to claim 1, wherein the width is 5 to 20% of the width of the agitator.

3. Crusher according to claim 1 or claim 2, characterised in that the maximum height of the protrusion o is the height of the entire agitator. 20

4. Crusher according to any of the preceding claims, characterised in that all agitators of the crusher wheel are provided with protrusions.

Crusher according to any of claims 1 to 3, 25 characterised in that only some agitators of the crusher wheel are provided with protrusions.

6. Crusher according to claim 5, characterised in e that those agitators which are provided with protrusions 30 are arranged symmetrically in the crusher wheel.

7. Crusher according to any one of the claims 1 to 6, characterised in that the protrusion is adjustable in the longitudinal direction of the agitator. W «\\MELB0\homeS\Piniyanka\Keep\Bpeci\l<922.95 CLAIMS.doc 15/08/97 I -6

8. Crusher substantially as herein described with reference to the drawings. Dated this 18th day of August 1997 BABCOCK LENTJES KRAFTWERKSTECHNIK GmnbH By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent Attorneys of Australia ft. ft.. \\MELBOI\home\f'iyaflka\Keep\speci\14922.95 CLAIM4S.doc 15/08197 Abstract The crusher wheel of a crusher has agitators between two discs the inward facing edge of the agitator protruding inwards on a portion of the width of the agitator into the inlet cross-section of the crusher wheel The protrusion (11) faces the inlet of the crusher wheel and has a width which is 1 to 40%, preferably 5 to 50%, of the width of the agitator (Fig.l) .e. e *0 r *Q