GB2454667A

GB2454667A - Method of and apparatus for crushing stone

Info

Publication number: GB2454667A
Application number: GB0722269A
Authority: GB
Inventors: Michael Harris
Original assignee: M G H RECYCLING Ltd
Current assignee: M G H RECYCLING Ltd
Priority date: 2007-11-13
Filing date: 2007-11-13
Publication date: 2009-05-20
Also published as: GB0722269D0

Abstract

A method of crushing granite and the like comprises heating the granite and then immediately applying percussive forces to the heated granite. Apparatus for carrying out the method may comprise an oven 1 having an inlet 2 and an outlet 3, means for heating the granite 6 as it passes between the inlet 2 and the outlet 3 of the oven 1, and a crusher 5 connected to the outlet 3 to receive and crush the heated granite.

Description

METHOD OF AND APPARATUS FOR CRUSHING STONE

Field of the Invention

This invention relates to a method of crushing stone, particularly granite, and to an apparatus for use in the method.

Background to the Invention

Railway ballast typically consists of granite chips or pieces, and after ex-tended use needs replacing with fresh material, since breakdown of the material adversely affects its ability to maintain the desired railway track geometry.

While a large proportion of ballast is subjected to cleaning and grading to permit io its re-use, some of it needs to be discarded, and this is typically crushed to re- duce the size of the chips so that the material can be put to other uses, for ex-ample in road or path surfacing.

There are two difficulties with the processing of spent ballast for new use: crushing the granite causes a high degree of wear on the crushing equipment; i5 and the ballast is often contaminated with oil from railway vehicles, which might render it unsuitable for some uses, and which is difficult to remove.

In general, the crushing of granite and similar hard igneous rock requires large forces and consequently massive machinery to carry out. The wear ex-perienced by such machinery is substantial. The operation is therefore costly.

Summary of the Invention

The present invention provides a method of crushing granite and the like, comprising heating the granite and then immediately applying percussive forces to the heated granite.

Preferably, the granite is passed through an oven, where it is preferably heated to a temperature sufficient to cause the surface of the granite to become incandescent, and into a rotary crusher.

The invention also provides an apparatus for crushing granite and the like, the apparatus comprising an oven having an inlet and an outlet, means for heating the granite as it passes between the inlet and the outlet of the oven, and a crusher connected to the outlet to receive and crush the heated granite.

The crusher may be of any conventional form, but is preferably of the type where a rotor carrying crushing teeth acts in conjunction with an anvil plate to apply the percussive forces to the granite.

The oven may be in the form of a tunnel through which the granite pieces pass in contra-flow to a flame, for example from a gas burner. It will be appre- ciated that other heating methods than a gas flame may be employed, for ex-ample a liquid-fuel burner or electrical heating.

It has been found that heating the granite to an elevated temperature, preferably such that the surface of the granite becomes incandescent, permits the crushing to occur with substantially less force and with significantly reduced wear on the components of the crusher. An added advantage is that the heat-ing burns off organic contaminants such as oil on the surface of the granite, which is especially useful in the case of spent railway ballast. Where there is a likelihood of contaminants on the granite, provision will need to be made for the cleaning of the gases emerging from the oven.

Since the chips of material emerging from the crusher will have been heated, they will be dry, rendering them suitable for use with other surfacing CV) materials such as asphalt.

The lower energy consumption in the crusher will at least partially corn-pensate for the increased energy use in the heating stage.

The method and apparatus of the invention are useful in the treatment of granite and similar igneous rocks, quartz pebbles, and like materials which are difficult to crush conventionally.

Brief Description of the Drawing

The drawing is a diagrammatic sectional view illustrating a crushing ar-rangement according to an exemplary embodiment of the invention.

Detailed Description of the Illustrated Embodiment

Referring to the drawing, a tubular oven 1 has an inlet hopper 2 and an outlet port 3, and is set at an angle for gravity flow to deliver granite chips or pieces 4 from the hopper 2 to discharge through the outlet port 3 into a rotary crusher 5. A gas burner jet 6 is mounted at the outlet end of the oven and is supplied with fuel gas via a supply pipe 7, The oven 1 may be mounted for ro- tation about its longitudinal axis, to permit rotation by means of an external mo-tor (not shown). Internal vanes or screws (also not shown) within the oven may cause agitation of the pieces 4 as they pass through the oven, ensuring uniform heating.

The crusher 5 consists of a feed hopper 8 over a crushing chamber 9, in which is mounted a rotor 10 formed as a series of hexagonal discs with spacers in between, each disc being angularly displaced from the next so that the teeth defined by the angles in the hexagons arrive progressively adjacent to an anvil plate 11, which has vertically-extending ribs and grooves aligned with the discs.

The rotor may be driven by a motor, suitably an hydraulic motor, mounted on the exterior of the apparatus, and not illustrated in the drawing. A toothed back-plate 12 protects the rear of the rotor and keeps it free from clogging by dust and small particles. Co C\J Ci')

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Claims

1. A method of crushing granite and the like, comprising heating the granite and then immediately applying percussive forces to the heated granite.

2. A method according to Claim 1, comprising passing the granite through an oven and then into a rotary crusher.

3. A method according to Claim 1 or 2, comprising heating the gran-ite until the surface thereof becomes incandescent.

4. Apparatus for crushing granite and the like, comprising an oven having an inlet and an outlet, means for heating the granite as it passes be-tween the inlet and the outlet of the oven, and a crusher connected to the outlet to receive and crush the heated granite.

5. Apparatus according to Claim 4, wherein the crusher is of the type in which a rotor carrying crushing teeth acts in conjunction with an anvil plate to apply the percussive forces to the granite.

6. Apparatus according to Claim 4 or 5, wherein the oven is in the C\J form of a tunnel through which the granite pieces pass in contra-flow to a flame, for example from a gas burner.

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7. Apparatus for crushing granite and the like, substantially as de-scribed with reference to, and/or as shown in, the drawing.