US3820847A

US3820847A - Method of mining a deposit of rock salt or the like

Info

Publication number: US3820847A
Application number: US00307145A
Authority: US
Inventors: C Jacoby
Original assignee: Akzona Inc
Current assignee: Akzona Inc
Priority date: 1972-11-16
Filing date: 1972-11-16
Publication date: 1974-06-28
Anticipated expiration: 1991-06-28

Abstract

There is disclosed a method for mining (rubblizing for transport to a processing plant) a mineral deposit comprised mainly of a hard ''''rock salt'''' type sodium chloride; potash; or the like mineral salt; having occasional inclusions therein of foreign materials which are of different heat conducting/absorbing characteristics. The method would apply to any mineral body which is of hard rock-like form having similar heat conductive and petro-fabric characteristics. Such mineral deposits may be either of sedimentary, or dome, or diaper form; and the method of the invention may be utilized when mining such deposits by any advancing face, or stope mining systems, or the like. The invention employs steam as a tool for shocking and splitting and rubblizing in-situ such mineral deposits; in such manner as to provide substantial mining cost economies, as well as substantial reductions in the percentages of undesirable ''''fines'''' in the mined products, compared to previously suggested and/or conventional mining techniques.

Description

United StatesPatent [191 Jacoby [111 3,820,847 [451 Ju e 28, 1974 METHOD OF MINING A DEPOSIT OF ROCK SALT OR THE LIKE Charles H. Jacoby, Dalton, Pa.

[73] Assignee: Akzona Incorporated, Asheville,

[22] Filed: 'Nov. 16, 1972 [21] Appl. No.: 307,145

[75] Inventor:

Primary Examiner-Ernest R. Purser Attorney, Agent, or FirmBean & Bean 5 7] ABSTRACT There is disclosed a method for mining (rubblizing for transport to a processing plant) a mineral deposit comprised mainly of a hard rock salt type sodium chloride; potash; or the like mineral salt; having occasional inclusions therein of foreign materials which are of different heat conducting/absorbing characteristics. The method would apply to any mineral body which is of hard rock-like form having similar heat conductive and petro-fabric characteristics. Such mineral deposits may beeither of sedimentary, or dome, or diaper form; and the method of the invention may be utilized when mining such deposits by any advancing face, or stope mining systems, or the like. The invention employs steam as a tool for shocking and splitting and rubblizing in-situ such mineral deposits; in such manner as to provide substantial mining cost economies,

as well as substantial reductions in the percentages of undesirable fines in the mined products, compared to previously suggested and/or conventional mining techniques.

zsiaieipr He e 1 METHOD OF MINING A DEPOSIT OF ROCK SALT OR THE LIKE BACKGROUND AND BRIEF SUMMARY OF THE INVENTION Rock salt mechanical mining processes typically involve the use of pneumatically, hydraulically, or electrically powered augers, or drills of the hammer or core type, for driving holes into the mine face (while also in some cases undercutting the face); and then blasting the material out of the mine face by use of high'explosive placements in the bore holes. This brings the mineral down upon the mine floor in a form quite suitable to be loaded for transport. However, such methods are overall quite expensive. Also, because rock salt is of an especially brittle and crystalline nature such processes invariably produce undesirably large percentagesof fines incidental to the undercutting and/or drilling and blasting operations.

The present invention derives from the discovery that when a jet of saturated steam is directed against a solid body of mineral rock salt or the like, it will bore into the body of mineral and act thereon in a unique manner. This is primarily because, as explained for example in U.S. Pat. No. 2,907,456, a typical rock saltdeposit comprises a mixture of water-soluble salt crystals havmize attendant mechanical pulverization and production of fines during the process. The term mine face as used herein refers to a body of mineral that is to be broken away from its native situs and rub'blized so as to be readily available for transport.

THE DRAWING The invention is illustrated by way of example in the accompanying drawing, wherein:

FIG. 1 is an illustration'of a fragment of typical runof-mine rock salt, comprised generally of intergrown pure sodium chloride salt crystals of diathermanous characteristics but having inclusions therein of anhydrite crystals and/or other foreign matters which are of due to the fact that a rock salt deposit comprises a ing different heat conducting/absorbing characteristics.

I have discovered that jets of steam may be employed to solvate and penetrate into a rock salt mine face and- /or to undercut the rock salt face so as to thereupon shock and loosen and heave the mineral from its situs, without the usual mechanical type fracturing of the mineral salt body; thereby providing an improved mining technique. Jets of steam, when employed in accordance with the invention, act upon the mineral body in a manner as to provide results that cannot be attained by use of other systems such as employ conventional drilling and blasting; dry-air jets; melting; nuclear shock or thermal-stressing; electron beam systems; or the like, such'as are suggested for example in US. Pats. Nos. 213,789; 1,025,029; 2,866,622; 2,712,351; 2,781,754; 3,205,953; 3,393,289; 3,422,911; 3,556,600. Reference is also made to U.S. Pat. No. 950,363 of Feb. 22, 1910 describing a method for mining gilsonite, a homogonously heat-transmitting type carbonaceous/asphaltum mineral deposit having inclusions of interstitial water/moisture therein. This patent teaches the use of heat for causing the mineral to flake or. slake away in response to expansion of the heattreated water content of the deposit. Any form of heat supply such as dry heat or steam may be utilized forthe purpose of mining such carbOn/asphaltum type minerals, thereby clearly distinguishing from the present invention.

It appears that the improved results of the present invention derive from the fact that steam jets operate upon a crystalline rock-salt type mineral deposit with a unique combination mineral-solvating and crystalseparating action, as well as with an aero/hydrodynamic flushing" action thereon as an opening is being driven into the rock salt. Saturated steam or superheated steam is preferably employed.

The primary object of the present invention is to reduce the expense of loosening and/or breaking out hard rock salt type minerals from a mine face; and to minidensely compact and pressure-plasticized-together aggregate of salt crystals which are by nature of individually glass-like and highly frangible mechanical characteristics. Therefore, applications thereto such as by dry heat; or of electron beams or melting devices or the like; or by conventional blasting methods or the like inherently operate to adversely convert the mineral and- /or pulverize large quantities of the mineral-body.

As distinguished-from such previously employed and- /or suggested mining methods, in accordance with the present invention a small diameter jet of steam is initially, directed against the mine face of rock salt, whereby the mineral body locally receiving the steam jet impact is subjected to a novel combination condensate -solvating, heat-stressing and aero/hydro-dynamic flushing action. Inasmuch as steam condensates provide a solvating action against salt, and the temperature of steam is quite uniform and moderate (even when In accordance with the present invention hard rock salt or the like may be advantageouslymined by use of tools such as are illustrated at FlGS. 2-3; whereby steam, either at normal or superheated steam temperatures will be directed against and progressively fedinto the mine face. As the hole into the rock salt mine face deepens, the rock salt body surrounding the hole hecomes progressively heated omnidirectionally of the hole. This phenomenon is accentuated, due to-the fact rocks.

HOwever,-as explained in US. Pat. No. 2,907,456, a rock salt deposit typically consists of a mixture of bodies having different heat absorbing/transmitting characteristics. Hence, the heat treatment process of the present invention causes these bodies to heat to different degrees; and thus causes them to strain relative to each other thereby inducing the phenomenon of slipfaulting along the salt crystal boundary areas thereof. FIG. 1 illustrates a typical mass of rock salt as found in nature, comprising in the majority a body of viscoplasticized together sodium chloride crystals designated which is of outstanding diathermanous characteristic, having occasional inclusions therein as illustrated at 12 of relatively athermanous minerals such as shale, anhydrite, or the like.

Thus, it will be understood that as the mining system of the invention progresses against a mine face as illustrated at 14 (FIGS. 2, 3) the high heat conductivity characteristic of the pure rock salt content of the deposit causes the salt body ambient of the steam jet opening to'become quite rapidly and uniformly heated to considerable distances away from the opening,

whereupon the rock salt body behind the mine face soon reaches its relatively low.shock temperature. At this time the operator of the system is made aware of the fact that the rock salt body has been split by reason of the sudden occurrence of audible seismic vibrations emanating from the rock salt mine face; and because of emissions of wisps of steam from fissures appearing in the heretofore solid rock salt mine face, such as are illustrated at 16 (FIGS. 2-3). This is clear evidence that the rock salt body has now been split into physically separate blocks, in accordance with the present invention.

It is to be understood that the mining operation is to be conducted in such manner that'maximum benefit of the unique splitting phenomena as explained hereinabove will be attained in order to provide an economic.

mining operation, and in order to minimize the production of undesirable fines. Thus, in most cases it may be preferred to initially provide an undercut as is well understood in the mining art, comprising an opening extending under and across the bottom of the rock salt fact 10; a typical undercut opening being illustrated at 20 (FIGS. 2-3). Thus, as the rock salt body thereabove is progressively penetrated and split as explained hereinabove, it is thereby relieved to rubblize the fall down upon the mine floor in response to the differential thermal reactions within the mineral body behind the face.

In any case, the steam jet holeswill preferably be driven into the rock salt body in such angular relationships as to maximize the subsequently occurring mineral deposit splitting effects, while at the same time minimizing the production of fines.

As shown herein by way of example at FIG. 3, the invention may be practiced by means of a portable boiler 22 to which is furnished any suitable supply of water. Heat may be supplied to the boiler in any suitable manner, such as by means of an electric heater; nuclear energy generator; or any type fuel burner; such as may be preferred. In any case the steam jet tube or lance as indicated generally at 24 will be supply-coupled to the boiler and arranged to be manually controlled in its operation such as by means of a suitable valve as is indicated at 26. As will be evident from the illustration at FIG. 3, the combination boiler and steam lance unit may be provided so as to be readily portable by a workman from place-to-place throughout the mine workings, and may be manually operable and tiltable to any desired angle for driving holes into the mine face such as are indicated at 28. Also, it is to be understood that whereas the steam lance, when being employed to drive holes into the mine face may be equipped with small diameter nozzles (such as of the order of A to 1 inch diameter) the discharge end of the lance may be alternatively provided with a flat or spade-shaped nozzle so as to adapt the device to open horizontally extended undercuts into and under the mine face such as indicated at 20.

FIG. 2 illustrates by way of further example a-modifled form of device for practicing the invention, wherein a lance 24 is slidably mounted upon a carrier 32 which in turn is mounted upon a vertical post 34 supported by any suitable boiler carrying vehicle such as indicated at 36. The carrier 32 is. motorized and geared to the post 34 so as to be vertically movable on i the post under control of the machine operator. Thus,

' it will be appreciated that the lance 24 may be mounted on the post 34 so as to be controlled to climb and/or lower thereon to any desired level, and then to be di rected against and into the mine face 14 at any desired elevation and/or desired angle, as the mining operation progresses. I

As illustrated at 40 (FIGS. 2-3) an expandable packer is preferably carried by the lance 24 at a position just behind the nozzle end thereof. The packer may be of any appropriately sized and suitable type and which is normally retracted but is expandable whenever desired by the machine operator from his position externally of the mine face. For example, the packer 40 may be of a type such as shown ineither of the US. Pats. Nos. 3,420,304; 3,575,237; or 3,690,375. 'In any case, the device will provide a facility whereby, after a hole has been'driven into the'face until the rock salt body has beensplit as explained hereinabove, the operator may (from externally of the face) actuate the packer so as to seal off the normal steam and brine debris exit annulus around the steam lance. The operator may then open the steam control valve'26 so as to deliver steam at an extremely high pressure into the split" areas of the mineral body radiating from the nozzle of the steam lance, as is illustrated at 42 (FIGS. 2-3), for the purpose of further splitting the rock salt body behind the face and heaving it outwardly and down upon the mine floor.

I claim:

1. The method of mining a face of mineral of the rocksalt type or the like which comprises a mixture of minerals'including a water-soluble mineral and another less Soluble mineral, said minerals having different thermalexpansion characteristics, said method comprising;

d re insaist s g in t n ner a so as to subject the, locus thereof to a combination 2. The method of mining as set forth in claim 1, wherein a plurality of spaced apart openings are thusly advanced into the mineral face to cooperate in splitting the mineral body behind the face.

3. The method of mining as set forth in claim 2, wherein said steam delivery tube is first employed to provide an undercut into and under the mine face.

4. The method of mining as set forth in claim 1, wherein said jet of steam is directed against and into the mineral face by means of an elongate tube terminating in a nozzle end portion; the nozzle end portion of said tube being progressively advanced into the mineral face as the opening thereinto deepens.

5. The method of mining as set forth in claim 4, wherein said steam delivery tube is equipped with an expandable packer adjacent the nozzle end portion thereof; said packer being expandable at will by the operator from externally of the mine face; and wherein subsequent to advancement of said tube into the mine face, said packer is operator-actuated to seal the steam exit annulus around said tube whereupon the operator causes steam to be delivered through said nozzle behind the mine face under high pressure so as to heave mineral in fragmented form away from the mine face.

6. The method of mining as set forth in claim 4, wherein said steam delivery tube is first employed to provide an undercut into and under the mine face.

7. The method of mining as set forth in claim 6, wherein said steam delivery tube is equipped with an expandable packer adjacent the nozzle end portion thereof; said packer being expandable at will by the operator from externally of the mine face; and wherein subsequent to advancement of said tube into the mine face, said packer is operator-actuated to seal the steam exit annulus around said tube whereupon the operator causes steam to be delivered through said nozzle behind the mine face under high pressure so as to heave mineral in fragmented form away from the mine face.

Claims

1. The method of mining a face of mineral of the rock salt type or the like which comprises a mixture of minerals including a water-soluble mineral and another less soluble mineral, said minerals having different thermal-expansion characteristics, said method comprising; directing a jet of stream against the mineral face so as to subject the locus thereof to a combination heating and solvating reaction and dynamic-flushing action, whereby a progressively deepening opening into the face is effected while incidental thereto the mineral body generally environmental to the opening and at substantial distances therefrom is rapidly heated due to the rapid heat conducting characteristics of the mineral body, whereby the mineral body is caused to split environmental to the opening and at substantial distances therefrom into physically individual fragments of mineral readily available for mechanical handling.

2. The method of mining as set forth in claim 1, wherein a plurality of spaced apart openings are thusly advanced into the mineral face to cooperate in splitting the mineral body behind the face.