WO2001064556A1

WO2001064556A1 - Method of transporting slimes

Info

Publication number: WO2001064556A1
Application number: PCT/ZA2001/000026
Authority: WO
Inventors: Geoffrey Robert Sawyer; Laurence Joel Solomons
Original assignee: Hersol Manufacturing Laboratories Cc
Priority date: 2000-03-01
Filing date: 2001-02-28
Publication date: 2001-09-07
Also published as: AU5006801A

Abstract

A method of transporting slimes which includes the steps of adding a suspension agent to the slimes at least at a first location, transporting the slimes from the first location to a second location, and adding a dewatering agent to the slimes at least at the second location.

Description

METHOD OF TRANSPORTING SLIMES

BACKGROUND OF THE INVENTION

The invention relates generally to a method of transporting slimes in a backfill system eg in mining and other underground applications and is also concerned with a method of modifying properties of the slimes to facilitate its transport, and placement in a support application

Slimes generated during mining operations, comprises particles of crushed ore which are of such a size that they settle very slowly in water Slimes can be used effectively in underground support applications but practical problems exist in transporting the slimes to a placement point and then in dewateπng the slimes so that the particles can compact and form effective support structures

SUMMARY OF THE INVENTION

The invention provides a method of transporting slimes which includes the steps of adding a suspension agent to the slimes at least at a first location, transporting the slimes from the first location to a second location, and adding a dewateπng agent to the slimes at least at the second location

The suspension agent acts as a viscosity modifier and the applicant has found that through the use of a suitable suspension agent the relative density of the slimes can be significantly increased As slimes is a by-product of ore processing, during a mining operation, the composition of the slimes depends on the type of ore processed The composition of the suspension agent used thus depends on the composition of the particular slimes to which it is to be added

According to one aspect of the invention the suspension agent includes at least

10% - 90% by weight of polyacry c acid, 10% - 90% by weight of sodium polyacrylate, 0% - 10% by weight of sodium carboxy methyl cellulose, 0% - 10% by weight ammonium polyacrylate, and 0% - 10% by weight glucono phosphates

The applicant has found that this type of suspension agent is suitable for use with a variety of rocks encountered particularly on South African gold mines

It is to be understood though that the relative proportions of the aforementioned ingredients may be varied according to requirement to take account of the type of ore which is being processed

In South African platinum mines and in certain diamond and gold mines however the nature of the rheology is such that the abovementioned suspension agent is not particularly effective A suspension agent which includes lignosulphate, gnosulphonate, or a salt thereof has been found to be particularly effective This suspension agent may be provided as a mixture or as a blend with carboxy methyl cellulose or its salts In the method of the invention the dewatenng agent may be added to the slimes at a plurality of points at the second location This may be done in any appropriate way but preferably the dewatenng agent is added to the slimes at a rate which is proportional to a flow rate of the slimes and the second location, in relation to a direction of flow of the slimes, is before a slimes placement point

The dewatenng agent may be positioned in a container which is located inside a slimes flow line and the dewatenng agent may be pressurised thereby to expel the dewatenng agent through at least one opening in the container, into the slimes

The pressuπsation may be effected in any appropriate way but preferably the dewatenng agent is pressurised by the slimes in the flow line

The composition of the dewatenng agent may also vary according to the type of ore which has given rise to the slimes The dewatenng agent preferably includes at least

10% - 25% by weight polyacrylamide, 5% - 15% by weight of carboxy methyl cellulose,

5% - 15% by weight of aluminium sulphate,

0% - 10% by weight polyamines,

0% - 10% by weight modified starches,

0% - 10% by weight dimethyl diallyl ammonium chloride, 0% -10% by weight organic coagulants, and water

Up to 60% water may be included in the dewatenng agent The dewatenng agent may be added to the slimes by making use of a dosage unit which includes a container in which the dewatenng agent is housed, the container being located inside a slimes flow line and including at least one opening, and a device which is exposed to slimes flow in the flow line thereby to pressurise the dewatenng agent inside the container and so cause the dewatenng agent to be expelled from the container through the said opening into the said flow line

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of examples, with reference to the accompanying drawings, in which Figure 1 is a flow diagram of a method of transporting slimes according to the invention,

Figures 2 and 3 are respectively side views, partly sectioned, of different dosage units for use in the method of the invention, and

Figure 4 is a schematic illustration of a gel manufacturing unit for use in the process of the invention

DESCRIPTION OF PREFERRED EMBODIMENTS

The applicant has found that the relative density of slimes can be significantly increased if a suspension agent of an appropriate type is introduced into the slimes It is believed that the suspension agent acts as a viscosity modifier by coating the particles in the slimes with electrically charged particles The repulsive forces between like electrical charges result in a greater number of particles remaining in suspension when compared to untreated slimes The applicant has found that the addition of the suspension agent allows finer particles 45 microns or smaller to be used in the slimes Traditional systems of which the applicant is aware have a lower limit on particle size of 100 microns

The slimes with the added suspension agent is transported using pipes and pumps In prior art systems of which the applicant is aware the slimes is disposed to settle and the particles move out of suspension and can be deposited on the walls of the transport pipes The applicant has found that it is advantageous to make use of two components in the suspension agent which have varying operating times These are respectively sodium polyacrylate which acts immediately on the particles in suspension and polyacrylic acid which is slow acting in that it reacts with the scale deposited on the pipes, dissolving the scale, then acting on the slimes In this sense the polyacrylic acid additionally acts as a de-scaling agent

By way of example the applicant has found, in relation to slimes formed at the Elaπdsrand Mine in South Africa that the following composition of suspension agent increases the relative density of the slimes by a factor of up to 2 80% by weight of polyacrylic acid, 10% by weight of sodium polyacrylate, and 10% by weight of sodium carboxy methyl cellulose

This composition is given merely by way of a desirable example for different slimes require different proportions of the ingredients in the suspension agent In certain instances the addition of ammonium polyacrylate or glucono phosphates can enhance the suspension/viscosity modification property of the slimes On the other hand in South African platinum mines and in certain diamond and gold mines however the nature of the rheology is such that the abovementioned suspension agent is not particularly effective A suspension agent which includes lignosulphate gnosulphonate, or a salt thereof has been found to be particularly effective This suspension agent may be provided as a mixture or as a blend with carboxy methyl cellulose or its salts

Figure 1 is a flow chart illustrating a method of transporting slimes in an underground mining operation

In a first reduction step 12, slimes 14 is produced as a by-product of ore processing The suspension agent 16 which, as noted, also acts as a viscosity modifier, is added to the slimes The point at which the suspension agent is added is not material provided that it is added prior to long distance transport of the slimes

The suspension agent may be added to the slimes using any suitable technique For example if the suspension agent is added to slimes in a storage bin then a metered quantity of suspension agent may be added through a suitable discharge nozzle which directs the suspension agent directly into the storage bin

In an optional step 18 the slimes may be stored and an additional quantity of the suspension agent 20 may be added to the slimes This may be required if storage of the slimes has resulted in settling of the particles in suspension

The slimes is transported using conventional techniques, to an underground location where it is separated (step 22) by the addition of a dewatenng agent or gel 24 The dewatenng gel acts as an agglomerator and charge neutraliser thereby separating the slimes into water 26 and backfill 28 consisting of the solid particles in the slimes The backfill is then used in the filling or erection of support walls and pillars in a step 30 using techniques which are known in the art and which for this reason are not further described herein

The applicant has found that the various chemicals operate on different size particles in suspension By way of example, it has been found, in relation to the aforementioned slimes produced at Elandsrand Mine in South Africa, that the following composition of the agent causes separation of the slimes 20% by weight of non-ionic polyacrylamide,

8% by weight of carboxy methyl cellulose, 4% by weight of aluminium sulphate, 4% by weight of polyamines, 2% by weight of modified starches, 2% by weight of organic coagulants, and

60% by weight of water

It is to be realised however that the composition of the dewatenng gel is dependent on the sizes of the particles in suspension and that an efficient use of the gel may require the proportions of the ingredients in the dewatenng gel to be varied It may also be desirable to add dimethyl diallyl ammonium chloride

The modified starches are of a form which is known in the art and may, for example be of a form which is sold under the trade mark Stygel-T Similarly the organic compounds are also known in the art and, for example, may be of a type sold under the trade mark Bucman 8089

As has been indicated the manner in which the suspension agent is added to the slimes is not particularly critical On the other hand it is important to add the dewatenng agent to the slimes in a more precise manner Figure 2 depicts a dosage unit 60 for adding the dewatenng agent to the slimes

The dosage unit 60 includes an outer housing 62 and an inner container 64 The housing 62 has an upstream end 66 which is connected by means of a quick-fit connector 68, of a kind which is known in the art, to a slimes flow line 70 Slimes flows through the line 70 in the direction of an arrow 72 through an opening 74 in an end wall 76 of the housing

At a downstream end 78 the housing 62 is connected to the remainder of the slimes flow line Preferably the dosage unit 60 is positioned close to the backfill

A pin 80 which traverses the housing 62 positions the container 64 correctly inside the housing Spacers may be positioned between the container and an inner wall of the housing to assist in this regard The housing 62 may be detached from the slimes flow line and, once the pin is removed, the container may be extracted from the housing This is necessary to replenish the container once its contents have been dispensed The container 64 is of tubular shape and is elongate It includes a plurality of openings 82 in its wall The container is sealed at its upstream and downstream ends 84 and 86 respectively

Near its upstream end 84 the container includes a slimes inflow hole or holes 88

At least one of the ends 84 86 may be removable, when the container 64 is not inside the housing, to allow the dewatenng agent to be placed inside the container

As slimes flows in the direction 72 through the line 70 it passes through the opening 74 into the housing 62 A portion of the slimes enters the container through the hole or holes 88 and helps to dissolve or disperse the gel, le the dewatenng agent, inside the container The slimes which flows on the outer side of the container moves at a relatively faster speed than when inside the line 70 The higher speed exerts a ventuπ-type action on the gel inside the container and assists in extracting the gel through the openings 82 The gel is therefore, on the one hand, loosened by the slimes, and on the other hand extracted from the container with a ventuπ-type action The gel is thereby dispersed into the slimes in a manner which is roughly dependent on the flow rate of the slimes through the housing

When the gel has been depleted the container is removed from the housing and replaced with a fresh container The empty container is then refilled To do this one of the ends 84, 86 is removed and the container is placed inside a plastic bag with the open mouth of the container uppermost Gel is placed into the container through the upper mouth and once the container is filled the removed end is reengaged with the container The plastic bag is then sealed On site the bag is severed and the filled container is removed, when required, so that it is ready for re-insertion into the housing 62

Figure 3 shows a dosage unit 90 according to a second form of the invention In this instance the unit includes an outer housing 92 and an inner container 94 The container 94 at an upstream end 96 has a thread formation 98 which is engageable with a complementary thread information on the housing 92 so that an open end 100 on the container faces into a slurry flow line 102 The housing 92 has a removable section 104 which, once detached from the remainder of the housing, allows the container 94 to be extracted from the housing

The container 94 at its downstream end 106, has a solid end cap 108 which seals the tubular section of the container A plurality of holes 110 are formed in the wall of the container near the end 106

A piston member 112 is shdably located inside the container slightly downstream of pressure control holes 114 in the wall of the container

When slimes flows through the line 102 it enters the container through the opening

100 and exerts pressure on the upstream side of the member 112 This pressure is transferred to a dewatenng gel 116 inside the container on the downstream side of the member 112 The gel is thereby pressurised and in this way is extruded to some extent through the holes 110 at the downstream end of the container

The increased speed flow on the outer side of the container gives rise to a ventuπ- type action which assists in extracting gel through the holes 110 The gel/slimes mixture then moves downstream to the point of placement With the arrangement shown in Figure 3 the rate at which the gel is mixed with the slimes is more proportional to the slimes flow rate than with the arrangement shown in Figure 2.

Figure 4 illustrates apparatus 200 for the manufacture of the dewatering agent or gel. The apparatus includes a liquid tank 202 and a powder hopper 204. Liquid is transported by a pipe 206 to a spiral air-agitated mixing vessel 208 which is pivotal about a point 210.

The powder in the hopper 204 is a mixture of polyacrylamide, carboxy methyl cellulose, polyamines, modified starches and organic coagulants in the proportions which have been referred to hereinbefore. The liquid in the tank 202 is a mixture of water, aluminium sulphate and dimethyl diallyl ammonium chloride.

The powder hopper 204 feeds into a carousel powder feeder 212. The feeder 212 includes an upper disc 214 which rotates about an axis 216 and includes holders 218A and 218B which are positionable at positions X and Y. As the holder 218A is rotated to position X, powder is fed into the holder 218A. A bottom edge 220 of the powder hopper abuts the disk 214. This ensures that the volumes of powder fed into the holders 218A and 218B respectively, are constant with each revolution of the disk 214 and precisely determinable.

As the disk 214 rotates further and the holder 218A moves to position Y, the cup is brought into alignment with a hole 222 formed in a lower disk 224. Powder contained in the holder 218A falls through the hole 222 into the mixing vessel 208. The mixing vessel 208 includes a spiral air agitator 226. The air agitator acts on the mixture of liquid and powder to form a gel. Once the gel is formed, the mixing vessel 208 pivots about the axis 216 and delivers the gel to a sachet 228.

The sachet 228 is sealed and used in the dosage unit illustrated in Figure 2 or 3.

Claims

1 A method of transporting slimes which includes the steps of adding a suspension agent to the slimes at least at a first location, transporting the slimes from the first location to a second location, and adding a dewatering agent to the slimes at least at the second location

2 A method according to claim 1 wherein the dewatering agent is added to the slimes at a plurality of points at the second location

3 A method according to claim 1 or 2 wherein the dewatering agent is added to the slimes at a rate which is proportional to a flow rate of the slimes and the second location, in relation to a direction of flow of the slimes, is before a slimes placement point

4 A method according to any one of claims 1 to 3 wherein the dewatering agent is housed in a container which is located inside a slimes flow line and the dewatering agent is pressurised thereby to expel the dewatenng agent, through at least one opening in the container, into the slimes

5 A method according to claim 4 wherein the dewatenng agent is pressurised by the slimes in the flow line

6 A method according to any one of claims 1 to 5 wherein the dewatering agent includes 10% - 25% by weight polyacrylamide,

5% - 15% by weight carboxy methyl cellulose, 5% - 15% by weight aluminium sulphate, 0% - 10% by weight polyamines; 0% - 10% by weight modified starches, 0% - 10% by weight dimethyl diallyl ammonium chloride, 0% - 10% by weight organic coagulants; and water

A method according to any one of claims 1 to 6 wherein the suspension agent includes at least one of the following: hgnosulphate, lignosulphonate; a salt of hgnosulphate, a salt of lignosulphonate

A method according to claim 7 wherein the suspension agent includes carboxy methyl cellulose

A method according to any one of claims 1 to 6 wherein the suspension agent includes at least

10% - 90% by weight polyacrylic acid, 10% - 90% by weight sodium polyacrylate;

0% - 10% by weight sodium carboxy methyl cellulose, 0% - 10% by weight ammonium polyacrylate, and 0% - 10% by weight glucono phosphates

A suspension agent for use in the method of claim 1 which includes at least- 10% - 90% by weight polyacrylic acid,

10% - 90% by weight sodium polyacrylate,

0% - 10% by weight sodium carboxy methyl cellulose,

0% - 10% by weight ammonium polyacrylate, and 0% - 10% by weight glucono phosphates

A suspension agent for use in the method of claim 1 which includes at least hgnosulphate, lignosulphonate, a salt of hgnosulphate, a salt of lignosulphonate

A dewatenng agent for use in the method of claim 1 which includes at least

10% - 25% by weight polyacrylamide, 5% - 15% by weight carboxy methyl cellulose, 5% - 15% by weight aluminium sulphate, 0% - 10% by weight polyamines, 0% - 10% by weight modified starches,

0% - 10% by weight dimethyl diallyl ammonium chloride,

0% - 10% by weight organic coagulants, and water

A dosage unit for adding a dewatering agent to shmes which includes a container in which the dewatenng agent is housed which is located inside a shmes flow line and which includes at least one opening, and a device which is exposed to shmes flow in the flow line thereby to pressurise the dewatenng agent inside the container through the said opening into the said flow line