FR2753913A1 - ROCK SAWING MIXTURES AND THE USE OF SAID MIXTURES - Google Patents

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

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

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

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

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

 Sawing granite is sometimes done using a multi-blade frame.

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

 The operating mixtures conventionally used for sawing granite comprise lime mixed with metal shot.

 In ancient sawing machines, lime was used to combat oxidation.

 This lime is nowadays used to increase the viscosity of the operating sawing mixtures and to facilitate the transport of the metal shot.

 The presence of this lime leads to significant recycling costs for used sawmill operating mixtures, in order to comply with environmental guidelines. Indeed, to facilitate the hydrocycloning of a lime-containing sawing process mixture, water is added to the mixture to lower its viscosity. Water laden with lime is an unacceptable industrial effluent.

 An object of the invention is therefore to provide hard sawing operating mixtures of hard rocks such as granite which are devoid of lime.

 The sawing operating blends of the invention surprisingly improve sawing efficiency.

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

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

 Initially, thixotropy qualified the property of a body to transform 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 it is applied a constant stress or shear rate is called thixotropic; provided that after removal of this constraint or shear rate 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, simple mechanical agitation is sufficient.

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

 Some nail polish, 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.

 An operating sawing 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 sawn.

 In this embodiment, the mixture further comprises a compound in an amount selected to set the pH of the mixture to a predetermined value.

 In one embodiment, the blend comprises mixed metal hydroxides.

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

 According to another embodiment, at least one of the thixotropic compounds is a clay rock powder 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 may be sodium bentonite, sometimes referred to as "High Grade", "High Yield" or "Western".

 It may be a calcium bentonite.

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

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

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

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

 In one embodiment, the compound for setting the pH of the sawing process mixture is sodium carbonate Na 2 CO 3.

 Other natural or synthetic compounds for setting a basic pH for the sawing mix may be used.

The metal hydroxides contained in the mixture, in one embodiment of the mixture, have a chemical composition of the type
LimDd T (OH) (m + 2d + 3 + na) A na
where m is the number of Li ions, between 0 and about 1,
D represents the divalent metal ions,
d is the number of D ions, ranging from 0 to about 4,
T represents the trivalent metal ions,
A represents 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 working mixture may comprise a polymer reversibly converted from the gel state to the fluid state when it experiences stress or shear rate.

 The various constituents 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 blends presented above to the sawing of a hard rock selected 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 one possibility of application, the sawing rock is formed mainly of quartz, alkali feldspar, plagioclase, mica and amphibole and is part of the granitoids.

 The sawing rock may be an ornamental granitoid selected from the group consisting of: porphyritic granites, pegmatites, saccharoid granites, fine-grained granites.

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

This sawing machine includes
- Feeding means of operating sawing mixture up to the cutting zone
- Permanent recycling means of the operating mixture to prevent dust and particles from sawing are incorporated into the mixture.

 In one embodiment, this machine is multi-blade chassis.

 Other objects and advantages of the invention will become apparent from the following description of two embodiments given by way of examples.

 FIG. 1 is a schematic rheogram of an operating sawing mixture according to the invention, this rheogram being compared with theoretical fluid behaviors.

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

 FIG. 1 shows a part of a rheogram 1 of an operating mixture according to the invention.

 On the abscissa, the derivative is plotted against 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 body of
BINGHAM;
a theoretical rheogram 4 of a rheofluidifying body obeying a power law or OSTWALD law
a theoretical rheogram of a rheofluidifying body obeying a HERSHEL type law
BULKLEY.

 Depending on the composition of the operating sawing mixture, a theoretical model of the 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 others, more complex, available in the literature.

 In the remainder of the text, reference will be made to the BINGHAM body which is a fairly good approximation of the rheograms obtained with the operating mixtures presented in the examples.

 According to this rheological model, beyond the threshold of flow rc, the BINGHAM bodies behave like Mewtonian liquids.

In other words T <tc T c
T> T cr = T c + tz
T being the shear stress
z being the derivative with respect to the time of the deformation
a being a coefficient called plastic viscosity.

 In contrast to the apparent viscosity of the sawing process mixture, which can vary and in particular decrease as shear increases, the plastic viscosity a is a constant corresponding to the slope of the theoretical rheogram.

is also a constant (yield point or
T 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 rate of deformation, but also depends on another parameter: time.

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

 It is not equivalent to proceed by increasing values of rc or z or decreasing by #C OR 2.

 We can consider drawing hysteresis curves with increasing and 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 FANN type viscometer, in the examples presented below.

 It is a cylindrical rotational 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 is at two speeds.

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

 The 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 tested material.

 But important corrections must be made to the results obtained with this type of rheometer to account for 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 gaps, which are 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 Tact the plastic viscosity a that can be related to the theoretical model of BINGHAM.

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

 It is preferred that this rheometer not be used to characterize an operating mixture containing shot. Separating means, for example magnetic, are used to separate the shot from a sample of the operating mixture whose rheological characteristics described above are desired to be determined.

 Two embodiments of operating sawing mixtures according to the invention are now described.

Example # 1
An operating sawing mixture is prepared whose composition is as follows
- water: 400 liters
- Rhodopol 23P: 2.5 kg
Na2CO3: added in an amount necessary to obtain a pH of 10.

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

The results obtained are
- plastic viscosity: 8 centipoise;
- flow threshold: 2200 lbf.pd2
- gels: 1200 to 1500 lbf.pd2.

 Poise P is the CGS unit of dynamic viscosity.

10P = 1Pa.s = 1 Poiseuille (P1).

The conventional British unit lbf.pd2 can be converted into a unit of the international system taking into account the following correspondence
1 lbf. pd2 47.88 Pa 47.88 N / m2
By observing the evolution of the shot in a test tube containing this mixture, it is found that the speed of the sedimentation of the particles depends on their diameter (Stokes' law), but also on the speed with which the gel effect appears.

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

 The mixture resumes its fluid appearance after vigorous stirring which can not be achieved 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, a clay mineral belonging to the smectite group.

 Given its high absorption and dispersion qualities, bentonite has many uses: drilling muds, molding sand, concrete, ion exchangers.

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

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

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

 Reference can be made to US 4,664,843.

 The Polyvis product is described therein as a composition containing mixed metal hydroxides of the MgAlOH4 7c10 .3 type.

Or more generally compounds of the type LimDdT (OH) (m + 2d + 3 + na) A where m corresponds to the number of ions
Li, ranging from 0 to about 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 valence anions other than OH
where a is the number of anions A; and
m + 2d + 3 + na being equal to or greater than 3.

 The Polyvis product is incorporated in a bentonite-rich sludge in the field of drilling, in particular oil drilling, to rapidly cement the drilling walls, the cement obtained acquiring a significant mechanical resistance in a short time, the objective being, in particular , 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 CO 3, bentonite and Polyvis are given per m3 of water in this table.

<tb> Na2CO3 <SEP> Bentonite <SEP> Polyvis <SEP> Viscosity <SEP> Threshold <SEP> Gel
<tb><SEP> (kg) <SEP> (kg) <SEP> (kg) <SEP> Plastic <SEP> Flow <SEP> (lbf.
<tb><SEP> (centi- <SEP> (lbf.pd2) <SEP><SEP> pu2) <SEP>
<tb><SEP> poises)
<tb><SEP> 2 <SEP> 20 <SEP> 0 <SEP> - <SEP> - <SEP> -
<tb><SEP> 2 <SEP> 80 <SEP> 0 <SEP> 8 <SEP> 800 <SEP> 400 <SEP> to
<tb><SEP> 800
<tb><SEP> 2 <SEP> 80 <SEP> 1.5 <SEP> 8 <SEP> 1200 <SEP> 800 <SEP> to
<tb><SEP> 1000
<tb><SEP> 2 <SEP> 95 <SEP> 3 <SEP> 10 <SEP> 1700 <SEP> 1000 <SEP> to
<tb><SEP> 1200
<Tb>

To obtain a good suspension of the shot, it is necessary to maintain fairly high rheology values of the order of
- plastic viscosity: 10 centipoises
- flow threshold: 1500 to 1700 lbf.pd2
gel 0/10: 1000 to 1200 lfb.pd2.

 The sedimentation of the shot in this mixture is at first much slower than with the mixture presented in Example 1, and whatever the particle size of the shot, then zero as soon as the kinetic energy has more effect.

The results for a final concentration of 2 to 2.5 kg of Na2CO3, 80 to 90 kg of bentonite, 2.5 to 3 kg of
Polyvis per m3 of water is all the more spectacular that a simple manual stirring puts back in motion the whole fluid shot.

 Other clay minerals from the smectite group such as beidellite, saponite, stevensite and nontronite can be considered.

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

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

The rheofludifying and thixotropic mixtures of the invention allow
- a better distribution of the shot along the blade, the wire or the saw during the sawing operation
- To avoid the clogging problem, common in the prior art and very problematic when restarting the sawing facility after a prolonged shutdown. Indeed, the operating sawing mixtures are frozen when they are not agitated and any sedimentation of solid particles becomes impossible or very slow
it is easier to operate the sludge suction pumps than in the prior art.

 The operating sawing mixtures of the invention do not necessarily comprise lime.

 It is no longer necessary to add water to the mixture to facilitate cycloning.

 Mechanical stirring by mechanical stirring, gas or air injection, wall vibration or ultrasound allows easy restarting of a sawing plant, even after prolonged shutdown.

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

Claims (18)

 1. Operating mixture of 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. The sawing process mixture according to claim 1 or 2, characterized in that it further comprises a compound in an amount selected to set the pH of the mixture to a predetermined value.  4. sawing process mixture according to any one of the preceding claims, characterized in that it contains mixed metal hydroxides.  5. Process mixture according to any one of the preceding claims, characterized in that at least one of the thixotropic compounds is a clay mineral selected from the group consisting of: kaolinite, berthierine, amesite, chrysolite, illites and vercmiculites, chlorites, smectites, pyrophyllites, talc, interstratified clay minerals.  6. sawing process mixture according to any one of the preceding claims, characterized in that at least one of the thixotropic compounds is a clay rock powder consisting essentially of a mixture of clay minerals selected from the group consisting of: kaolinite, berthierine, amesite, chrysolite, illites and vermiculites, chlorites, smectites, pyrophyllites, talc, interstratified clay minerals.  7. sawing process mixture according to any one of the preceding claims, characterized in that it comprises bentonite.  8. sawing process mixture according to any one of claims 2 to 7, characterized in that the granular material is selected from the group consisting of metals and metal alloys, ceramics, rocks.  9. Sawing operating mixture according to any one of claims 2 to 8, characterized in that it comprises carbon steel shot.  10. Sawing operating mixture according to any one of claims 3 to 9, characterized in that the compound for setting the pH of the mixture to a predetermined value is Na2 CO3 sodium carbonate.  11. Sawing process mixture according to any one of claims 4 to 10, characterized in that the mixed metal hydroxides have a chemical composition of the type  LimDd T (OH) (m + 2d + 3 + na) A n  at  where m is the number of Li ions, between 0 and about 1,  D represents the divalent metal ions,  d is the number of D ions, ranging from 0 to about 4,  T represents the trivalent metal ions,  A represents 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.  12. Sawing process mixture according to any one of claims 1 to 3, characterized in that it comprises a polymer reversibly converted from the gel state to the fluid state when it undergoes a stress or a shear rate. .  13. Operating mixture according to any one of claims 9 to 12, characterized in that, in the absence of mechanical stirring of the mixture, the steel shot remains in suspension and does not sediment in the mixture.  14. Application of the sawing operating blend presented in any one of claims 1 to 13 to the sawing of a hard rock selected from the group consisting of metamorphic rocks, magmatic rocks and sedimentary rocks of high hardness such as slate, slate schists, carbonate rocks, siliceous rocks.  15. Application of the sawing mix according to claim 14, characterized in that the sawing rock is essentially formed of quartz, alkali feldspar, plagioclase, mica and amphibole and is part of the granitoids.  16. Application of the sawing mix according to claim 15, characterized in that the sawing rock is an ornamental granitoid selected from the group consisting of: porphyritic granites, pegmatites, saccharoids granites, fine-grained granites.  Sawing machine implementing the application presented in any one of claims 14 to 16, this machine comprising  - Feeding means of operating sawing mixture to the cutting zone;  - Permanent recycling means of the operating mixture to prevent dust and particles from sawing are incorporated into the mixture.  18. Sawing machine according to claim 17, characterized in that it comprises a multi-blade frame.