IE930538A1 - A quarrying process and apparatus - Google Patents

Abstract

A process for quarrying limestone below the natural water table in a quarry includes preparing and blasting rock face below the water table. A sump is excavated at a base of the rock face and a portable submersible pump is lowered into this sump to lower the water level adjacent the rock face and maintain the water level at a pre-set desirable level. The blasted rock can then be removed and delivered to a processing plant for reduction in a controlled manner to produce selected limestone products. A portion of the water discharged from the sump is preferably delivered to a spray system in the processing plant for dust suppression.

Description

This invention relates to a quarrying process and apparatus, in particular for quarrying limestone located below the natural water table in a quarry.

According to the invention, there is provided a process 5 for quarrying limestone which is located below the natural water table in a quarry, comprising the steps: (a) drilling one or more bore holes in a rock face which extends below the natural water table in a quarry, charging each bore hole with a blasting compound and blasting the rock face, (b) excavating a sump at a base of the rock face, (c) lowering a mobile submersible pump into the sump and operating the pump to lower the water level in the quarry adjacent the rock face to a pre-set desirable level, (d) loading the blasted rock into a dump truck and transporting the rock to a hopper for controlled rock feed to an impact crusher for reducing the rock to a nominal size of less than 75 mm, (e) discharging scalpings from the impact crusher to a scalpings stockpile and discharging crushed rock from the impact crusher to a primary vibrating screen, separating vibrating size -10 delivering (f) the rock material on the primary screen, delivering material of nominal mm to a stockpile and selectively larger'' nmaXdriai''’. From the psinary (Ji 'ci'-l : SECTION 2o AND Dul.E 23 JNL NoJZfi........OF vibrating screen to either hammer mills for reducing the material to powdered lime, or alternatively delivering the material to a granulator for reduction of the material to stone of nominal size less than 10 mm.

Advantageously, the water discharged from the pump can be delivered into an underground cavern for disposal of the water.

In one embodiment of the invention the process includes the step of sensing the water level in the sump and operating the pump to maintain the water level in the sump within pre-set limits for maintaining the water level in the quarry adjacent the rock face at the pre-set desirable level.

In another embodiment the process includes the step of spraying water onto the rock material as it is transported around the rock processing plant for suppressing dust.

In a further embodiment the process includes the step of supplying the water for suppressing dust from the water discharged from the sump by the submersible pump.

In another embodiment, the process includes the step of discharging the larger material from the primary vibrating screen onto a screen discharge conveyor having an outlet end positioned over a feed hopper for the granulator, a feed conveyor for the hammer mills having an inlet end positioned below the outlet end of the screen discharge conveyor and above the hopper, selectively operating a material flow control flap pivotally mounted adjacent the outlet end of the screen discharge conveyor for dropping material onto the feed conveyor for the hammer mills or for deflecting material into the feed hopper for the granulator.

In another embodiment the process includes the steps of discharging material from the granulator to a secondary vibrating screen, separating the material into fine grit material which is delivered to a grit stockpile and delivering larger material from the second vibrating screen to a stockpile of material of nominal size -10 mm.

In a further embodiment the process includes the step of recirculating the larger material discharged from the secondary vibrating screen for re-entry to the granulator.

In another aspect the invention provides apparatus as will be hereinafter described for carrying out a quarrying process according to the invention.

The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:Fig. 1 is a diagrammatic illustration of a quarrying process according to the invention; Fig. 2 is a diagrammatic illustration of a rock processing plant used in the process; Fig. 3 is a perspective view of portion of a quarry having a rock face located beneath the natural water table; Fig. 4 is a diagrammatic illustration of a submersible pump used in the process shown mounted in a sump formed in the quarry for reducing the water level in the quarry according to the process; Fig. 5 is a perspective view of a rock processing plant according to the invention for carrying out the quarrying process; Fig. 6 is a perspective view of an impact crusher portion of the processing plant; Fig. 7 is a perspective view of a granulator portion of the processing plant; Fig. 8 is a detail perspective view of portion of the processing plant; Fig. 9 is a detail elevational view of the processing plant shown in Fig. 8; and Fig. 10 is a diagrammatic illustration of portion of the processing plant.

Referring to the drawings, a process and apparatus for quarrying limestone according to the invention will be described .

Referring briefly first to Fig. 3, there is illustrated a quarry 10 having an upper portion 12 with a floor 13, the upper portion 12 having been quarried down to adjacent the natural water table of the quarry 10. The present invention advantageously allows the removal of further rock from the quarry 10, this rock being located below the natural water table. The illustration shows a hole 14 in the floor 13 of the quarry 10 from which rock has been excavated .

According to the process of the invention a number of bore holes are drilled into a rock face 15, spaced-apart along a top edge 16 of the rock face 15. Each hole is charged with a blasting compound and the rock face 15 is blasted, the blasted rock 17 falling into the hole 14.

Next a digger enters the hole 14 and excavates a sump 20 at a base of the rock face 15. A submersible pump assembly 22 (see Fig. 4) is lowered by any suitable means, such as a crane 24 for example, into the sump 20. The pump assembly 22 comprises a tubular housing 25 having a pair of spaced-apart legs 26 on an underside of the housing 25. A submersible pump 28 is mounted within the housing 25. A power cable 29 and water discharge hose 30 extend from the pump 28 outwardly up over the rock face . An eye 32 and lifting cable 33 are attached at the top of the housing 25. A pair of spaced-apart level sensors 35, 36 are mounted vertically spaced-apart on the housing 25 and have associated cables 37 leading to a controller for the pump 28. The pump 28 is operated to lower the water level within the hole 14 to enable removal of the blasted rock 17. The pump 28 operates to reduce the water level to the level of the low level sensor 36 and then the pump 28 is switched off. Water will gradually fill the sump 20 until it reaches the high level sensor 35 which will again operate the pump 28 to reduce the water level to the low level sensor 36. Advantageously, the water discharged from the pump 28 can be delivered into an underground cavern for disposal of the water. It will be appreciated that the pump assembly 22 can be readily easily dropped into the sump 20 and also removed from the sump 20 before blasting the rock face.

Once the water level within the hole 14 has been reduced a loader 38 enters the hole 14 and loads the blasted rock 17 into a dump truck 40. The dump truck transports the rock to a hopper 42 at an inlet of an impact crusher 43. Chains 45 suspended at an outlet of the hopper 42 control the feed of rock into the impact crusher 43. Within the impact crusher 43, rock is reduced to a nominal size of less than 75 mm. Scalpings are discharged from the impact crusher 43 on a laterally extending conveyor 47 to a scalpings stockpile 48. Crushed rock discharged from the impact crusher 43 is delivered by means of a conveyor 49 to a primary vibrating screen 50.

The primary vibrating screen 50 separates the rock material, delivering material sized -10 mm via a conveyor 52 to a stockpile 53. Larger material, typically sized between 10-75 mm is discharged from the vibrating screen onto a screen discharge conveyor 55 having an outlet end positioned over a feed hopper 57 for a granulator 58. A feed conveyor 60 for delivering material to hammer mills 62 has an inlet end 63 positioned below the outlet end 56 of the screen discharge conveyor 55 and above the hopper as can be more clearly seen in Figs. 7 to 9. A flow control flap 65 is pivotally mounted on a support frame 66 for the screen discharge conveyor 55 adjacent the outlet end 56. This flap 65 is pivotable by means of a push rod 68 mounted on the frame 66 from a neutral position as shown in Fig. 8 in which material is allowed drop off the outlet end 56 of the conveyor 55 onto the inlet end 63 of the feed conveyor 60 for the hammer mills 62. The flap 65 may be moved to a deflecting position shown in broken outline in Fig. 9 covering the inlet end 6 3 of the conveyor 60 and deflecting material from the conveyor 55 into the hopper 57. Thus, advantageously the flow of material can be readily easily controlled for delivery to either the hammer mills 62 or the granulator 58.

Material delivered to the hammer mills 62 is crushed into a powder form and delivered to a powdered lime stockpile.

Referring to Fig. 2, the material delivered into the hopper 57 is fed via a conveyor 70 to an inlet of the granulator 58. Material discharged from the granulator feeds along a conveyor 72 to a secondary vibrating screen 73. This material is then separated, fine grit being delivered by a laterally extending conveyor 75 to a grit stockpile 76. Larger material is delivered from the secondary vibrating screen 73 through a chute 78 to a stockpile 79 of material of nominal size -10 mm. Where more grit is required the larger material may be recirculated from the vibrating screen 73 along a recirculating conveyor 82 for delivery onto the conveyor 70 feeding the granulator 58.

Fig. 10 shows apparatus 90 for selectively controlling the discharge of material from the secondary vibrating screen 73. The apparatus 90 comprises a channel-section transfer chute 91 mounted at an outlet 9 2 of the secondary vibrating screen 73. A discharge end of the transfer chute 91 has a central divider 94, defining two outlets for the transfer chute 91, namely a first recycling outlet 95 which discharges on to the recirculating conveyor 82 and a second outlet 96 which discharges into the chute 78. A deflector plate 98 is movably mounted within the transfer chute 91 to funnel material from the secondary vibrating screeen 73 to one of the outlets 95, 96. In the drawing, the deflector plate 98 is arranged for delivery of material to the recirculating conveyor 82. The position of the deflector plate 98 for delivery of material to the chute 78 is shown in broken outline.

Although not illustrated in the drawings, the apparatus includes a spray system having a number of spray heads located above the conveyors, screens and other apparatus for discharging a water spray onto the material as it is moved around the processing plant for suppressing dust. Advantageously, the water may be supplied from the pump 28 evacuating the sump 20.

The invention is not limited to the embodiment hereinbefore described which may be varied in both construction and detail.

Claims (5)

1. A process for quarrying limestone which is located below the natural water table in a quarry, comprising the steps: (a) drilling one or more bore holes in a rock face which extends below the natural water table, charging each hole with a blasting compound and blasting the rock face, (b) excavating a sump at a base of the rock face, (c) lowering a mobile submersible pump into the sump and operating the pump to lower the water level in the quarry adjacent the rock face to a pre-set desirable level, and maintaining the water level at said pre-set desirable level, (d) loading the blasted rock into a dump truck and transporting the rock to a hopper for controlled rock feed to an impact crusher for reducing the rock to a nominal size of less 20 than 75 mm, (e) discharging scalpings from the impact crusher to a scalping stockpile and discharging crushed rock from the impact crusher to a primary vibrating screen, 25 (f) separating the rock material on the primary vibrating screen, delivering material of nominal size -10 mm to a stockpile and selectively delivering larger material from the primary vibrating screen to either hammer mills for reducing the material to powdered lime, or alternatively delivering the material to a granulator for reduction of the material to stone of nominal size less than 10 mm.

2. A process as claimed in claim 1 including the step of sensing the water level in the sump and operating the pump to maintain the water level in the sump within pre-set limits for maintaining the water level in the quarry adjacent the rock face at the pre-set desirable level.

3. A process as claimed in claim 1 or claim 2 including the step of spraying water onto the rock material as it is delivered through the rock processing plant for suppressing dust.

4. A process as claimed in claim 3 including the step of supplying the water for suppressing dust from the water discharged from the sump by the submersible pump.

5. A process as claimed in any preceding claim including the step of discharging the larger material from the primary vibrating screen onto a screen discharge conveyor having an outlet end positioned over a feed hopper for the granulator, a feed conveyor for the hammer mills having an inlet end positioned below the outlet end of the screen discharge conveyor and above the hopper, selectively operating a material flow control flap pivotally mounted adjacent the outlet end of the screen discharge conveyor for dropping material onto the feed conveyor for the hammer mills or for deflecting material into the feed hopper for the granulator. A process as claimed in any preceding claim including the steps of discharging material from the granulator to a secondary vibrating screen, separating the material into fine grit material which is delivered to a grit stockpile and larger material delivered to a stockpile of material of nominal size -10 mm. 10 7 15 8 A process as claimed in claim 6 including the step of recirculating the larger material discharged from the secondary vibrating screen for re-entry to the granulator. A process substantially as hereinbefore described with reference to the accompanying drawings. Apparatus for carrying out the process as claimed in any preceding claim substantially as hereinbefore described with reference to the accompanying drawings .