WO1998013180A1

WO1998013180A1 - Operational mixtures for sawing rocks and use of these mixtures

Info

Publication number: WO1998013180A1
Application number: PCT/FR1997/001538
Authority: WO
Inventors: Daniel Huet
Original assignee: Wheelabrator Allevard S.A.
Priority date: 1996-09-27
Filing date: 1997-08-29
Publication date: 1998-04-02
Also published as: EP0932485B1; FR2753913B1; AR009367A1; EP0932485A1; FR2753913A1; BR9711574A; SA98190175A; AU4121797A

Abstract

The invention concerns operational mixtures for sawing hard rocks such as for example granite, these mixtures containing at least one thixotropic compound and not necessarily containing lime.

Description

OPERATIONAL MIXTURES FOR ROCK SAWING AND IMPLEMENTATION OF THESE MIXTURES

The invention relates to operating sawing mixtures as well as to the use of these mixtures.

The invention relates more particularly to the sawing of hard rocks such as: granite, gneiss, mica schist, pegmatite, and in general, all magmatic, metamorphic or even sedimentary rocks having a high hardness.

In the rest of the text, reference will essentially be made to sawing granite, that is to say sawing a rock containing essentially micas, feldspar and quartz in variable proportions.

It is understood, however, that other types of rock can be sawn using machines using operating mixtures of the invention.

The sawing of granite is sometimes carried out using a multi-blade chassis.

Machines incorporating such chassis are known to those skilled in the art, and will therefore not be described in detail here.

The operating mixtures conventionally used for sawing granite include lime mixed with metallic shot.

In old sawing machines, lime was used to combat oxidation. This lime is used today to increase the viscosity of sawing process mixtures and to facilitate the transport of metallic shot.

The presence of this lime leads to significant recycling costs for used sawing process mixtures, in order to comply with environmental directives. In fact, to facilitate the hydrocycloning of a sawing operating mixture containing lime, water is added to the mixture to lower the viscosity. Water loaded with lime is an unacceptable industrial effluent.

It is therefore an object of the invention to provide operating mixtures for sawing hard rocks such as granite which are free of lime.

The sawing process mixtures of the invention surprisingly improve the efficiency of sawing.

In particular, the productivity of a machine with a multi-blade chassis is greatly improved.

The rock sawing operating mixtures according to the invention comprise at least one thixotropic compound.

Initially, thixotropy qualified the property of a body to transform itself reversibly and gradually from the gel state to the fluid state.

The term thixotropy is used here in a more general sense. Any body whose apparent viscosity tends to decrease over time when a constant stress or shear rate is applied to it is said to be thixotropic; provided that after removing this constraint or this shear speed and after a sufficient rest time, its initial structure is regenerated. And this, whether this initial structure is a gel or not.

In the case where the thixotropic compound is a gel, it is reversible, that is to say that to liquefy it, simple mechanical stirring is sufficient.

If necessary, another physical modification (temperature, pH) can participate in the liquefaction. Chemical gels, for which crosslinking points can form by chemical reaction are excluded.

Some nail polishes, lipsticks, some oily solutions, some cellulose derivatives are thixotropic in the sense defined above.

Due to the presence of at least one thixotropic compound in an operating sawing mixture according to the invention, this mixture itself is thixotropic.

A sawing operating mixture according to the invention may further comprise a granular material of predetermined hardness as a function of the average hardness of the rock to be sawed. In this embodiment, the mixture further comprises a compound in an amount chosen to set the pH of the mixture at a predetermined value.

In one embodiment, the mixture comprises mixed metal hydroxides.

According to one embodiment, at least one of the thixotropic compounds is a clay mineral chosen from the group comprising: kaolinite, berthierine, amesite, chrysolite, illites and vermiculites, chlorites, smectites, pyrophyllites, talc, inter-layered clay minerals.

According to another embodiment, at least one of the thixotropic compounds is a powder of clay rocks consisting essentially of a mixture of clay minerals chosen from the group comprising: kaolinite, berthierine, amesite, chrysolite, illites and vermiculites, chlorites, smectites, pyrophyllites, talc, interstratified clay minerals.

The mixture comprises, in a particular embodiment of the invention, bentonite.

Bentonites are clay minerals from the montmorillonite group.

The bentonite used can be of natural origin.

It can be sodium bentonite, sometimes called "High Grade", "High Yield" or "Western". It may be a calcium bentonite.

The bentonite used can also be an activated calcium bentonite, made sodium by chemical treatment.

The bentonite used can also be a bentonite treated with an organic dopant such as cellulose derivatives, acrylic acid or derivatives thereof.

The granular material with a hardness equal to or greater than the average hardness of the rock to be sawn is chosen from the group comprising metals and metal alloys, ceramics, rocks.

In one embodiment, this granular material is carbon steel shot.

In one embodiment, the compound making it possible to fix the pH of the sawing operating mixture is sodium carbonate Na ₂ O-,.

Other natural or synthetic compounds making it possible to fix a basic pH for the operating sawing mixture can be used.

The metal hydroxides contained in the mixture, in one embodiment of the mixture, have a chemical composition of the type:

Li _m D _d T (OH) _{(m + 2d + 3 + na)} A _n cL where m is the number of Li ions, between 0 and about l, D represents the divalent metal ions, d is the number of D ions, between 0 and approximately 4,

T represents the trivalent metal ions, A represents the monovalent or polyvalent anions of valence n, other than OH ~, a is the number of anions A,

(m + 2d + 3 + na) being greater than or equal to 3.

The operating mixture may comprise a polymer which reversibly transforms from the gel state to the fluid state when it undergoes a stress or a shear rate.

The various components of the mixture can be mixed in water.

In the absence of mechanical agitation of the mixture, any abrasive granular material such as steel shot remains in suspension and does not sediment in the mixture.

The invention also relates to the application of the sawing operating mixtures presented above to sawing a hard rock chosen from the group comprising metamorphic rocks, magmatic rocks and sedimentary rocks of significant hardness such as slate, slate shale , carbonate rocks, siliceous rocks.

According to a possible application, the rock to be sawn is formed essentially of quartz, alkali feldspar, plagioclase, mica and amphibole and is part of the granitoids. The rock to be sawed can be an ornamental granitoid chosen from the group comprising: porphyroid granites, pegmatites, saccharoid granites, fine-grained granites.

Thirdly, the invention relates to a machine implementing the application of a sawing process mixture to sawing hard rocks.

This sawing machine includes:

- Means for supplying the sawing process mixture to the cutting zone;

- Means for permanent recycling of the operating mixture making it possible to prevent dust and particles from sawing being incorporated into the mixture.

In one embodiment, this machine has a multi-blade chassis.

Other objects and advantages of the invention will appear during the following description of two embodiments given by way of examples.

Figure 1 is a schematic rheogram of a sawing operating mixture according to the invention, this rheogram being compared to theoretical behaviors of fluids.

The operating mixtures obtained according to the invention are shear thinning and thixotropic.

FIG. 1 shows part of a rheogram 1 of an operating mixture according to the invention. On the abscissa is plotted the derivative with respect to the time of the deformation.

On the ordinate, the shear stress is reported.

Figure 1 also shows: a theoretical rheogram 2 of a Newtonian fluid; a theoretical rheogram 3 of a BINGHAM body; a theoretical rheogram 4 of a shear-thinning body obeying a power law or OSTWALD law; a theoretical rheogram 5 of a shear-thinning body obeying a HERSHEL-BULKLEY type law.

Depending on the composition of the operating sawing mixture, a theoretical model of power law or BINGHAM body type will be closer to the rheogram of the operating mixture than another theoretical model.

Other theoretical models are a priori possible such as those of SHANGRAW, WILLIAMS CARREAU, CROSS, or EYRING and still others, more complex, available in the literature.

In the rest of the text, reference will be made to the body of BINGHAM which constitutes a fairly good approximation of the rheograms obtained with the operating mixtures presented in the examples. According to this rheological model, beyond the flow threshold τ _c , BINGHAM bodies behave like mewtonian liquids.

In other words:

T <τ _c Σ = 0 r> τ _c T = τ _c + ∑

T being the shear stress; Σ being the derivative compared to the time of the deformation; α being a coefficient called plastic viscosity.

Unlike the apparent viscosity of the sawing process mixture, which can vary and in particular decrease with increasing shear, the plastic viscosity a is a constant corresponding to the slope of the theoretical rheogram.

τ _c is also a constant (yield point or yield value) corresponding to the ordinate at the origin of the theoretical rheogram.

Since the operating mixtures are thixotropic, their apparent viscosity is not fixed for a given value of the stress or the speed of deformation, but also depends on another parameter: time.

Under these conditions, the experimental mode adopted for plotting rheograms is important.

It is not equivalent to proceed by increasing values of r _c or Σ or decreasing of τ _c or Σ. One can consider drawing hysteresis curves with increasing and then decreasing shear, as when a fluidizing gel with hysteresis is studied.

To avoid the problems presented above and to simplify the rheological measurements in the vicinity of the sawing machine, the viscosity of the operating fluid was measured using a viscometer of the FANN type, in the examples presented below.

It is a cylindrical rotary rheometer; a fixed stator and a rotor coaxial with the stator defining an air gap containing the operating sawing mixture.

In the examples considered, the FANN rheometer has two speeds.

Other rheometers can be used, in particular rheometers of the plate cone type, rheometers with forced oscillations.

Plateau cone type rheometers are sometimes considered preferable for the characterization of thixotropic or antithixotropic liquids, since it is considered that, in this type of rheometer, the mechanical history is the same for all the layers of the material tested.

However, significant corrections must be made to the results obtained with this type of rheometer to take account of the sliding layers on the walls. These corrections are more complex for cone / plate rheometers than for cylindrical rheometers.

The use of cylindrical rheometers for the study of the thixotropic mixtures of the invention requires very narrow air gaps, difficult to manufacture with precision.

But coaxial cylindrical rheometers eliminate the effects of thermalization and ensure a constant thermal environment.

The FANN rheometer makes it possible to determine the flow threshold τ _c , the plastic viscosity α which can be related to the theoretical model of BINGHAM.

The FANN rheometer also makes it possible to determine the stress from which the frost effect disappears, if any.

It is preferable that this rheometer is not used to characterize an operating mixture containing shot. Separation means, for example magnetic, are used to separate the shot from a sample of the operating mixture for which it is desired to determine the rheological characteristics presented above.

We now describe two embodiments of sawing operating mixtures according to the invention. Example 1

A sawing operating mixture is prepared, the composition of which is as follows: - water: 400 liters;

- Rhodopol 23P: 2.5 kg;

- Na ₂ C0 ₃ : added in an amount necessary to obtain a pH of 10.

Rhodopol (registered trademark) is a xanthan-based polymer.

The results obtained are:

- plastic viscosity: 8 centipoise; - flow threshold: 2200 lbf.pd ² ;

- gels: 1200 to 1500 lbf.pd ² .

The Poise P is the CGS unit for dynamic viscosity. 10P = lPa.s = 1 Poiseuille (PI).

The conventional Anglo-Saxon unit lbf.pd ² can be converted into an international system unit by taking into account the following correspondence:

1 lbf. pd ² ≈ 47.88 Pa ≈ 47.88 N / m ²

By observing the evolution of the shot in a test tube containing this mixture, one notes that the speed of the sedimentation of the particles depends on their diameter (law of Stokes), but also on the speed with which the effect of freezing appears.

If the mixture shows real progress compared to those currently used by sawyers, it should however be noted that, if it remains too long without agitation, it tends to polymerize and take on a gelatinous appearance.

The mixture resumes its fluid appearance after vigorous stirring which cannot be obtained by hand but requires a mechanical stirrer, as a test after a rest of eight days has demonstrated.

Example # 2

This mixture is based on the interaction of bentonite and Polyvis (registered trademark).

Bentonite is a montmorillonite, that is to say a clay mineral belonging to the group of smectites.

Given its great qualities of absorption and dispersion, bentonite knows many uses: drilling mud, molding sand, concrete, ion exchanger.

Clay minerals such as bentonite are used as thixotropic thickeners, especially for household detergents.

In the field of drilling, it is known to use thixotropic fluids containing bentonite.

The use of a drilling fluid containing bentonite and a product called Polyvis (registered trademark) is also known in the field of drilling, in particular oil drilling.

We can refer to US document n ° 4,664,843. The Polyvis product is described therein as a composition containing mixed metal hydroxides of the type MgA10H _{4 # 7} Cl _0ι3 .

Or more generally, compounds of the type:

where m corresponds to the number of Li ions, between 0 and approximately 1;

D denotes divalent metal ions; d denotes the number of divalent metal ions D, between 0 and about 4;

T represents trivalent metal ions; A represents monovalent or polyvalent anions of valence n other than OH ~; a being the number of anions A; and m + 2d + 3 + na being equal to or greater than 3.

The Polyvis product is incorporated into a bentonite-rich mud in the field of drilling, in particular oil drilling, to quickly cement the drilling walls, the cement obtained acquiring significant mechanical resistance in a short time, the objective being, in particular , to avoid water coming into the wellbore.

Surprisingly, the use of a mixture containing this Polyvis product and bentonite has proved particularly advantageous in the field of sawing hard rocks such as granite.

The table below presents the results obtained for various mixtures.

The amounts of Na ₂ C0 ₃ , bentonite and Polyvis are given per m ³ of water in this table. Na ₂ C0 ₃ Bentonite Polyvis Viscosity Threshold Gel (kg) (kg) (kg) Drainage plastic (lbf.

(centi- (lbf.pd ² ) pd ² ) poises)

2 20 0 - - -

2 80 0 8 800 400 to 800

2 80 1.5 8 1200 800 to 1000

2 95 3 10 1,700 1,000 to 1,200

To obtain a good suspension of the shot, the rheology values must be kept fairly high, on the order of:

- plastic viscosity: 10 centipoise;

- flow threshold: 1500 to 1700 lbf.pd ² ;

- gel 0/10: 1000 to 1200 lfb.pd ² .

The sedimentation of the shot in this mixture is first much slower than with the mixture presented in Example 1, and this whatever the size of the shot particle, then zero as soon as the kinetic energy does not has more effect.

Results for a final concentration of 2 to

2.5 kg of a ₂ C0 ₃ , 80 to 90 kg of bentonite, 2.5 to 3 kg of Polyvis per m ³ of water is all the more spectacular when a simple manual stirring sets the fluid assembly in motion shot. Other clay minerals from the smectite group such as beidellite, saponite, stevensite and nontronite can be considered.

Clay minerals belonging to the group of chlorites, illites and vermiculites or even to the group of pyrophyllites and talc can be envisaged just like attapulgite, sepiolite.

In general, any composition comprising at least one clay mineral and a greater or lesser amount of Polyvis making it possible to obtain the rheological properties presented above falls within the scope of the invention.

The rheofludifying and thixotropic mixtures of the invention allow:

- better distribution of the shot along the blade, wire or saw during the sawing operation;

- Avoid the clogging problem, frequent in the prior art and very problematic when restarting the sawing installation after a prolonged shutdown. Indeed, the operational sawing mixtures freeze as soon as they are not agitated and any sedimentation of solid particles becomes impossible or very slow;

- Operation of the sawdust suction pumps easier than in the prior art.

The sawing process mixtures of the invention do not necessarily contain lime. It is no longer necessary to add water to the mixture to facilitate cycloning.

Mechanical agitation by mechanical stirring, injection of gas or air, vibration of walls or ultrasound allows an easy restart of a sawing installation, even after a prolonged shutdown.

The thixotropy of the operating mixture can be maintained, even with large quantities of rock powder or steel.

Claims

1. Operative mixture for sawing rocks, characterized in that it comprises at least one thixotropic compound.

2. Operating mixture according to claim 1, characterized in that it further comprises a granular material of predetermined hardness as a function of the average hardness of the rock to be sawn.

3. Operative sawing mixture according to claim 1 or 2, characterized in that it further comprises a compound in an amount chosen to fix the pH of the mixture at a predetermined value.

4. Operating sawing mixture according to any one of the preceding claims, characterized in that it contains mixed metal hydroxides.

5. Operating mixture according to any one of the preceding claims, characterized in that at least one of the thixotropic compounds is a clay mineral chosen from the group comprising: kaolinite, berthierine, amesite, chrysolite, illites and vercmiculites, chlorites, smectites, pyrophyllites, talc, interstratified clay minerals.

6. Operating sawing mixture according to any one of the preceding claims, characterized in that at least one of the thixotropic compounds is a powder of argillaceous rocks essentially consisting of a mixture of clay minerals chosen from the group comprising: kaolinite, berthierine, amesite, chrysolite, illites and vermiculites, chlorites, smectites, pyrophyllites, talc, interlayered clay minerals.

7. Operating sawing mixture according to any one of the preceding claims, characterized in that it comprises bentonite.

8. Operating sawing mixture according to any one of claims 2 to 7, characterized in that the granular material is chosen from the group comprising metals and metal alloys, ceramics, rocks.

9. sawing process mixture according to any one of claims 2 to 8, characterized in that it comprises carbon steel shot.

10. Operating sawing mixture according to any one of claims 3 to 9, characterized in that the compound making it possible to fix the pH of the mixture at a predetermined value is sodium carbonate Na ₂ C0 ₃ .

11. Operating sawing mixture according to any one of claims 4 to 10, characterized in that the mixed metal hydroxides have a chemical composition of the type:

^Li m ^D d ^{T (} ° ^H > (m ₊ 2d + 3 + na) ^A n 'a where m is the number of Li ions, between 0 and about l,

D represents the divalent metal ions, d is the number of D ions, between 0 and about 4,

(m + 2d + 3 + na) being greater than or equal to 3.

12. Operating sawing mixture according to any one of claims 1 to, characterized in that it comprises a polymer transforming reversibly from the gel state to the fluid state when it undergoes a stress or a shearing speed.

13. Operating mixture according to any one of claims 9 to 12, characterized in that, in the absence of mechanical agitation of the mixture, the steel shot remains in suspension and does not sediment in the mixture.

14. Application of the operating sawing mixture presented in any one of claims 1 to 13 to sawing a hard rock chosen from the group comprising metamorphic rocks, magmatic rocks and sedimentary rocks of significant hardness such as slate, slate shales, carbonate rocks, siliceous rocks.

15. Application of the operating sawing mixture according to claim 14, characterized in that the rock to be sawn is formed essentially of quartz, alkali feldspar, plagioclase, mica and amphibole and is part of the granitoids.

16. Application of the operating sawing mixture according to claim 15, characterized in that the rock to be sawed is an ornamental granito selected from the group comprising: porphyroid granites, pegmatites, saccharoid granites, fine grain granites.

17. Sawing machine implementing the application presented in any one of claims 14 to 16, this machine comprising: - means for supplying the sawing process mixture to the cutting zone;

means of permanent recycling of the operating mixture making it possible to prevent dust and particles from sawing being incorporated into the mixture.

18. Sawing machine according to claim 17, characterized in that it comprises a multi-blade chassis.

MODIFIED RFVFNDICATIONS

[received by the International Bureau on 28 January 1998 (28.01.98); sell ⁱ cations 1-18 replaced by amended claims 1-17 (4 pages)]

1. Operative mixture for sawing rocks, characterized in that it comprises at least one thixotropic compound, and, moreover, a granular material of predetermined hardness as a function of the average hardness of the rock to be sawn.

2. sawing process mixture according to claim 1, characterized in that it further comprises a compound in an amount chosen to fix the pH of the mixture to a predetermined value.

3. sawing process mixture according to claim 1 or 2, characterized in that it contains mixed metal hydroxides.

4. Operating mixture according to any one of the preceding claims, characterized in that at least one of the thixotropic compounds is a clay mineral chosen from the group comprising: kaolinite, berthierine, amesite, chrysolite, illites and veremiculi es, chlorites, smectites, pyrophyllites, talc, interstrati ted clay minerals.

5. Operative sawing mixture according to any one of the preceding claims, characterized in that at least one of the thixotropic compounds is a powder of clay rocks consisting essentially of a mixture of clay minerals chosen from the group comprising: kaolinite, berthierine, amesite, chrysolite, illites and vermiculites, chlorites, smectites, pyrophyllites, talc, clay minerals interstja & ti iés.

6. Operating sawing mixture according to any one of the preceding claims, characterized in that it comprises bentonite.

7. Operating sawing mixture according to any one of the preceding claims, characterized in that the granular material is chosen from the group comprising metals and metal alloys, ceramics, rocks.

8. Operating sawing mixture according to any one of the preceding claims, characterized in that it comprises carbon steel shot.

9. Operating sawing mixture according to any one of claims 2 to 8, characterized in that the compound making it possible to fix the pH of the mixture at a predetermined value is sodium carbonate Na ₂ C0 ₃ .

10. Operating sawing mixture according to any one of claims 3 to 9, characterized in that the mixed metal hydroxides have a chemical composition of the type:

Lim ^D d ^T < ^0H ) (m + 2d + 3 + na) ^A _& n where m "st the number of ions i, between 0 and about 1, D represents the divalent metal ions, d is the number of D ions, between 0 and around 4,

T represents the trivalent metal ions, A represents the monovalent or polyvalent anions of valence n, other than OH ~, a is the number of anions A, (m + 2d + 3 + na) being greater than or equal to 3.

11. Operating sawing mixture according to claim 1 or 2, characterized in that it comprises a polymer transforming reversibly from the gel state to 1 • fluid state when it undergoes a stress or a shearing speed.

12. Operating mixture according to any one of claims 8 to 11, characterized in that, in the absence of mechanical agitation of the mixture, the steel shot remains in suspension and does not sediment in the mixture.

13. Application of the operating sawing mixture presented in any one of claims 1 to 12 to sawing a hard rock chosen from the group comprising metamorphic rocks, magmatic rocks and sedimentary rocks of significant hardness such as slate, slate shales, carbonate rocks, siliceous rocks.

14. Application of the operating sawing mixture according to claim 13, characterized in that the rock to be sawn is formed essentially of quartz, alkaline feldspar, plagioclase, mica and amphibole and is part of the granitoids.

15. Application of the operating sawing mixture according to claim 14, characterized in that the rock to be sawed is an ornamental granito selected from the group including: porphyroid granites, pegmatites, saccharoid granites, fine-grained granites.

16. Sawing machine implementing the application presented in any one of claims 13 to 15, this machine comprising:

- Means for supplying the sawing process mixture to the cutting zone;

- means for permanent recycling of the operating mixture, making it possible to prevent dust and particles from sawing being incorporated into the mixture.

17. Sawing machine according to claim 16, characterized in that it comprises a multi-blade chassis.

MODIFIED SHEET (ARTICLE 19.