CA1208918A - Calcined serpentine useful as sandblasting agent - Google Patents
Calcined serpentine useful as sandblasting agentInfo
- Publication number
- CA1208918A CA1208918A CA000454993A CA454993A CA1208918A CA 1208918 A CA1208918 A CA 1208918A CA 000454993 A CA000454993 A CA 000454993A CA 454993 A CA454993 A CA 454993A CA 1208918 A CA1208918 A CA 1208918A
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- Prior art keywords
- tailings
- sandblasting
- silica
- calcined
- dust
- Prior art date
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Abstract
A B S T R A C T
There is provided a sintered angular shape granular sandblasting material obtained by the calci-nation of asbestos tailings at a temperature of from 1300°C to 1450°C, said asbestos tailings being charac-terized by having a MgO:SiO2 ratio lower than 1.0, the granular sandblasting material being characterized by a cold compression mechanical strength of prom 10 to 160 MPa, by a granulometry of -40 to +150 mesh (Tyler), and by being substantially free of dust.
There is provided a sintered angular shape granular sandblasting material obtained by the calci-nation of asbestos tailings at a temperature of from 1300°C to 1450°C, said asbestos tailings being charac-terized by having a MgO:SiO2 ratio lower than 1.0, the granular sandblasting material being characterized by a cold compression mechanical strength of prom 10 to 160 MPa, by a granulometry of -40 to +150 mesh (Tyler), and by being substantially free of dust.
Description
~20~
PRIOR ART
Silica in the form of quartz particles is a material of general use in sandblasting applications~
In sandblasting operations, the grain of silica is advantageous because it is efficient as an abrasive medium. A high speed stream of silica parti-cles has been found useful for the removal of scale and rust from iron and steel, thus generating a clean and roughened surface appropriate for machining or coating.
As a sandblasting agent, silica presents a certain number of drawbacks:
- Silica, specially in processes where new surfaces are generated on t~e silica grains by either abrasion or impact, has been found extremely active where in contact with living organism. This is particularly true when silica dust is inhaled, such conditions being held responsible for silicosis, a widely spread disease in areas exposed to high level of silica dust.
- Secolldly, on a technical point of view, silica used for sandblasting i~ obtained by mining depo~its of ~ilica which is then sieved and sometimes ground to proper mesh size before use. These operations frac-ture silica particles leaving their structure weakened by microfractures, thus rending said particles rather fragile upon impact. This relative weakness of the silica grains explains the large amount of dust gener-ated when the material is used under conditions of ~20~9~1L8 severe mechanical attrition. The friability of silica grains when used for sandblasting prevents its re-cycling, thus adding substantially to the cost of the operation.
It should also be appreciated ~hat the handling of silica for sandblasting purposes necessarily generates dust and thus represents a major industrial health problem. Dust from silica is known to be re-sponsible for the serious diseases known as silicosis.
SUMMARY OF THE INVENTION
In accordance with the present invention the drawbacks of natural silica grains used in sandblasting operations is unexpectedly overcome by providing a modi-~ied serpentine granular material.
The present invention provides a novel sinter-ed angular shaped granular sandblasting material derived from the calcination of asbestos tailings at a tempera-ture o~ from 1300 to 1450C, the starting asbestos tailings being characterlzed by an MgO:SiO2 ratio lower than 1Ø Furthermore, the sandblasting material of the present invention is characterized by a cold compression mechanical strength of from 10.0 to 160 MPa and a granulometry in the range of -40 to ~150 mesh (Tyler) and by being substantially free of dust, that is parti-cles smaller than 200 mesh (Tyler).
DESCRIPTION OF THE INVENTION
Serpentine is an hydrated variety of magnesium silicate and occurs naturally in very large amounts, particularly as rejects or tailings from asbestos mining~ A thermal treatment should in principle be able to transform this serpentine into an anhydrous magnesium silicate as follows:
3MgO.2SiO2.2H2O ~ 3MgO-2Sio2 ~ 2H2o Asbestos tailings However, it is well known to those familiar in the art of calcined products that a calcining operation of serpentlne, specially when accompanied by gas evo-lution from the calcined species, may lead to a very fragile and porous entity.
For example, in the course of the manufacture of quick lime, limestone, a relatively hard and dense material, is transformed into a friable and porous mass by loss of carbon dioxide.
When serpentine tailings are calcined at a temperatur~ required fox its dehydration, between 750 and 850C, we have noted a pattern similar to limestone has heen noted whereby the mass becomes quite soft and easily converted into ~ine dust following the thermal treatment.
The heat treatment at 750C to 850C is ~uite efficient for the removal of any residual chrysotile fibers from those tailings, but the end product is next to useless as sandblasting material because of its softness and poor mechanical strength.
An obvious solution to this weakness of the calcined material would be to raise the calcining temperature to such a value that ~here would be a partial melting of the magnesium silicate in order to generate a ceramic bond between the particles. Upon ex-amination of the phase diagram for the system MgO/SiO2, one can note that the melting temperature for the 3MgO.2SiO2 is in the area of 1700 - 1800C. Such a high temperature of fusion therefore precludes the economical use of a material calling for such treatment.
However, contrary to what could be expected fxom the 3MgO.2SiO2 system, it has been ~ound that a thermal treatment at a much lower temperature, in the range of 1250 to 1325C, gave a highly sintered material having excellent mechanical properties, allowing its use as sandblasting foundry sands. The ~am; nation under microscope shows that grains of calcined tailings are quite angular in their shape and very di~ferent from the 5mooth surface of mined sand which has acquired a pol-ished surace by attrition oE the asperi~ies over theages.
Without going into limitative theoretical considerations, we can explain this unexpected case of ceramic bonding by a close examination of the chemistry involved in the course of the thermal treatment. It must be noted here that a serpentine tailing contains, beside MgO and SiO2, up to 9% of iron oxides expressed ~2~
as FeO and Fe2O3 combined. When the material is sub-jected to heat, the first reaction is a dehydration as noted above.
3MgO.2SiO2.2H2O.n~eO.Fe2O3) 750 850 C ~
2H2O + 3MgO.2SiO2.n(FeO,Fe203) This dehydration is completed at 900C. Above that temperature, the production of ~orsterite predomi-nates, up to 1200C. ~his production of forsterite is accompanied by an evolution of free silica.
PRIOR ART
Silica in the form of quartz particles is a material of general use in sandblasting applications~
In sandblasting operations, the grain of silica is advantageous because it is efficient as an abrasive medium. A high speed stream of silica parti-cles has been found useful for the removal of scale and rust from iron and steel, thus generating a clean and roughened surface appropriate for machining or coating.
As a sandblasting agent, silica presents a certain number of drawbacks:
- Silica, specially in processes where new surfaces are generated on t~e silica grains by either abrasion or impact, has been found extremely active where in contact with living organism. This is particularly true when silica dust is inhaled, such conditions being held responsible for silicosis, a widely spread disease in areas exposed to high level of silica dust.
- Secolldly, on a technical point of view, silica used for sandblasting i~ obtained by mining depo~its of ~ilica which is then sieved and sometimes ground to proper mesh size before use. These operations frac-ture silica particles leaving their structure weakened by microfractures, thus rending said particles rather fragile upon impact. This relative weakness of the silica grains explains the large amount of dust gener-ated when the material is used under conditions of ~20~9~1L8 severe mechanical attrition. The friability of silica grains when used for sandblasting prevents its re-cycling, thus adding substantially to the cost of the operation.
It should also be appreciated ~hat the handling of silica for sandblasting purposes necessarily generates dust and thus represents a major industrial health problem. Dust from silica is known to be re-sponsible for the serious diseases known as silicosis.
SUMMARY OF THE INVENTION
In accordance with the present invention the drawbacks of natural silica grains used in sandblasting operations is unexpectedly overcome by providing a modi-~ied serpentine granular material.
The present invention provides a novel sinter-ed angular shaped granular sandblasting material derived from the calcination of asbestos tailings at a tempera-ture o~ from 1300 to 1450C, the starting asbestos tailings being characterlzed by an MgO:SiO2 ratio lower than 1Ø Furthermore, the sandblasting material of the present invention is characterized by a cold compression mechanical strength of from 10.0 to 160 MPa and a granulometry in the range of -40 to ~150 mesh (Tyler) and by being substantially free of dust, that is parti-cles smaller than 200 mesh (Tyler).
DESCRIPTION OF THE INVENTION
Serpentine is an hydrated variety of magnesium silicate and occurs naturally in very large amounts, particularly as rejects or tailings from asbestos mining~ A thermal treatment should in principle be able to transform this serpentine into an anhydrous magnesium silicate as follows:
3MgO.2SiO2.2H2O ~ 3MgO-2Sio2 ~ 2H2o Asbestos tailings However, it is well known to those familiar in the art of calcined products that a calcining operation of serpentlne, specially when accompanied by gas evo-lution from the calcined species, may lead to a very fragile and porous entity.
For example, in the course of the manufacture of quick lime, limestone, a relatively hard and dense material, is transformed into a friable and porous mass by loss of carbon dioxide.
When serpentine tailings are calcined at a temperatur~ required fox its dehydration, between 750 and 850C, we have noted a pattern similar to limestone has heen noted whereby the mass becomes quite soft and easily converted into ~ine dust following the thermal treatment.
The heat treatment at 750C to 850C is ~uite efficient for the removal of any residual chrysotile fibers from those tailings, but the end product is next to useless as sandblasting material because of its softness and poor mechanical strength.
An obvious solution to this weakness of the calcined material would be to raise the calcining temperature to such a value that ~here would be a partial melting of the magnesium silicate in order to generate a ceramic bond between the particles. Upon ex-amination of the phase diagram for the system MgO/SiO2, one can note that the melting temperature for the 3MgO.2SiO2 is in the area of 1700 - 1800C. Such a high temperature of fusion therefore precludes the economical use of a material calling for such treatment.
However, contrary to what could be expected fxom the 3MgO.2SiO2 system, it has been ~ound that a thermal treatment at a much lower temperature, in the range of 1250 to 1325C, gave a highly sintered material having excellent mechanical properties, allowing its use as sandblasting foundry sands. The ~am; nation under microscope shows that grains of calcined tailings are quite angular in their shape and very di~ferent from the 5mooth surface of mined sand which has acquired a pol-ished surace by attrition oE the asperi~ies over theages.
Without going into limitative theoretical considerations, we can explain this unexpected case of ceramic bonding by a close examination of the chemistry involved in the course of the thermal treatment. It must be noted here that a serpentine tailing contains, beside MgO and SiO2, up to 9% of iron oxides expressed ~2~
as FeO and Fe2O3 combined. When the material is sub-jected to heat, the first reaction is a dehydration as noted above.
3MgO.2SiO2.2H2O.n~eO.Fe2O3) 750 850 C ~
2H2O + 3MgO.2SiO2.n(FeO,Fe203) This dehydration is completed at 900C. Above that temperature, the production of ~orsterite predomi-nates, up to 1200C. ~his production of forsterite is accompanied by an evolution of free silica.
2 ~MgO.2SiO2~n(Feo~Fe2o3 ~ C >
3 ~2MgO.SiO2)-2i3n(FeO~Fe2O3 ~ + Si2 Forsterite Free silica As the temperature reaches 1300C, the system evolves towards the production of enstatite which is, in fact, a recombination of previously liberated silica with forsterite. This reaction is known to be rapid above 1300C.
2MgO SiO ~ SiO 1300C ~ 2(MgO SiO ) Forsterite Enstatite The mixture of forsterite and enstatite in the proportion delimited by the starting serpentine has a very hiyh melting point above 1700C as indicated beEore. However, the presence of iron oxides in the tailings allows the formation of rather fusible iron silicates such as gruenerite and fayalite. Therefore, we explain the unexpected low sintering temperature of serpentine tailings by the formation of gruenerite (iron metasilicate) and fayalite (iron orthosilicate) from the silica made available by the production of forsterite and the already present iron oxides.
For the contemplated uses of calcined tailings, the ~ardness of grains is always a consideration of im-portance. However, in the case of sandblasting material, the requirement on hardness becomes the determinant factor. It has been noted that the basicity index (1~) which is the MgO to SiO2 ratio does vary from mine to mine. Also, it has been noted that a low basicity index (MgO:SiO2 ratio) (i.e. 1~ smaller than 1.00) corresponds to a lower refractoriness and an easier vitrification thus leading to a harder ,product obtained at lower temperatures.
This point is well illustrated by Table I, where the hardening resulting from sintering is noted for two different types of tailings of high and low basicity index.
Those results clearly show the advantage of using an acid tailings (1~1) if no refractoriness but rather great mechanical strength is required from the end product.
TABLE I
COMPARISON OF HEAT SINTERING OF TAILINGS
SOURCES Chem. ~nalysis Cold compression strength (MPa) after firing at indicated temperature MgOsio2 1~ 1150C 1200C 1250C 1300C 1400C1440C
Bell ~ines35 %40.3% 0.86 1.04 0.63 4.35 10.29 68.74157.84 Quebec Carey Mines40.5~37.1% 1.09 2.02 1.98 2.02 1.93 2.484.73 Quebec ~2~
It will be readily noted that Bell tailings (1~ = 0.86) are advantageous for the production of sand-blasting material because they are more easily sintered at a temperature of around 1300C. The mechanical strength under those conditions is substantially higher than what is observed with more basic tailings as repre-sented by Carey material (1~ = 1.09~.
SANDBLASTING
For sandblasting operation, two criteria are of paramount importance to obtain high performances, that is the hardness of grains and their angular shape.
All other factors being kept equal, an angular material will lead to more efficient abrasion while a better hardness of the grains will allow a higher percentage of recycling of the sandblasting agent.
Since a tailings with a basicity index lower than one can be sintered at a lower temperature than basic tailings, it would be obvious to select such low basicity tailings as starting material. We have found in practice that tailings such as those of Bell Mine, with a basicity index of the order of 0.86, when fired for one hour at 1300C, gave a high performance material for sandblasting.
The calcined material has to be sieved in order to give an adequate sandblasting agent. For coarse sandblasting, a granulometr~ of 16 to +60 mesh (Tyler) has been found adequate whereas for finer work -.i, including p~lishing, the mesh size can be from -40 to values as low as +150 mesh (Tyler).
Using standard methods in sandblasting indus-try, it has now been established that calcined tailings are more efficient than silica as sandblasting agent while generating less dust and being more easily re-cycled. Those advantageous performances are clearly shown by Tables II and III.
TABLE II
SANDBLASTING OF UNIT SURFACE OF MILD STEEL
Material usedMesh sizeUnit su.rface cleaned/min.
for sandblasting (Tyler) (cm2/min.) Laboratory test Field test Calcined tailings Bell, 1300C -16 ~60 82.1 3716 Silica Ottawa/ round-30 +60 52.5 2601 shaped grains Silica Xndusmin, angular -20 ~50 79.7 shaped grains i TABLE III
Mesh size Calcined tailings Ottawa sand Indusmin Sand Slag sand (Tyler~ Bell 1300C
Initial10 usesInitial10 usesInitial10 uses Initial 10 uses (%) (~) (%) (%) (%) (%) +20 43.715.7 0.2 0.2 18.0 0.5 20~7 5.
+3~ 28~524.7 9.7 5.0 41.7 4.1 32.8 11.3 +40 15.123.0 43.6 38.3 20.6 8.6 20.5 12.6 +50 12.612.8 13.6 21.~ 12O3 11.0 13.7 11.9 +60 0.13.9 2~.3 5.9 3~4 ~.0 4.5 5.6 +80 0 5.0 11.1 7.4 ~.7 10.7 4~3 8.7 Dust 014.9 1.5 21.6 1.3 59.1 3.5 44.5 Total~ 100.0100.0100.0 100.0 100.0 100.0 100.0 100.0 It will be readily not~d from Table II that material having round grains is not very efficient for sandblasting. The comparison of either calcined tailings or angular silica (Indusmin) to smooth silica is very illuminating on that point: the unexpected improvement obtained with a grain having an angular structure is of 50% over the smooth grains. It must be underlined that the ratio of field performances between calcined tailings and silica (1.42) is very close to the same ratio determined at a smaller scale, in laboratory test (1.56).
However, beside intrinsic abrading power, one must take into account the sturdiness of abrading grains since too soft a material will prevent economic re-cycling o~ the sandblasting agPnt. Examination of Table III shows clearly the advantage of using calcined tailings over other products that reveal themselves, upon use, as either too fragile or too friable to allow recycling. It is obvious that any material containing from 20 to 50% of fines is not worth a recycling oper--ation.
From observations confirmed ~y field tes~s, i~
can be said that calcined tailings still can be used ef-ficiently as sandblasting agent after 20 cycles whereas other material like silica cannot stand lO cycles.
Therefore, it is obvious from these data that calcined tailings, because of their angular shape and good hardness resulting of sintering in the course of the firing operation, appear as a significantly superior material for sandblasting. Beside its intrinsic abrad-ing performances, it generates less dust and allows recycling.
Table IV illustrates clearly the better hard-ness o~ grain shown by calcined tailings in comparison with a silica having an angular shape (Indusmin). This hardness must be understood as the resistance to frac-ture and is best appreciated by repetitive uses of thesand while evaluating the increase fraction of dust.
Indusmin silica sand is used because its performances as an abrasive, as per Table II, are only slightly lower than calcined tailings. It will be readily noted that the attrition on the Indusmin sand is much more severe than in the case of calcined tailingsO
~18 TABTE IV
ATTRITIQN OF THE GRANULES PER CYCLE
Per cent fraction smaller than B0 mesh (Tyler) Number of cycles Calcined tailings Indusmin Bell, 1300C
0 0 1.3 2 2.98 11~57
2MgO SiO ~ SiO 1300C ~ 2(MgO SiO ) Forsterite Enstatite The mixture of forsterite and enstatite in the proportion delimited by the starting serpentine has a very hiyh melting point above 1700C as indicated beEore. However, the presence of iron oxides in the tailings allows the formation of rather fusible iron silicates such as gruenerite and fayalite. Therefore, we explain the unexpected low sintering temperature of serpentine tailings by the formation of gruenerite (iron metasilicate) and fayalite (iron orthosilicate) from the silica made available by the production of forsterite and the already present iron oxides.
For the contemplated uses of calcined tailings, the ~ardness of grains is always a consideration of im-portance. However, in the case of sandblasting material, the requirement on hardness becomes the determinant factor. It has been noted that the basicity index (1~) which is the MgO to SiO2 ratio does vary from mine to mine. Also, it has been noted that a low basicity index (MgO:SiO2 ratio) (i.e. 1~ smaller than 1.00) corresponds to a lower refractoriness and an easier vitrification thus leading to a harder ,product obtained at lower temperatures.
This point is well illustrated by Table I, where the hardening resulting from sintering is noted for two different types of tailings of high and low basicity index.
Those results clearly show the advantage of using an acid tailings (1~1) if no refractoriness but rather great mechanical strength is required from the end product.
TABLE I
COMPARISON OF HEAT SINTERING OF TAILINGS
SOURCES Chem. ~nalysis Cold compression strength (MPa) after firing at indicated temperature MgOsio2 1~ 1150C 1200C 1250C 1300C 1400C1440C
Bell ~ines35 %40.3% 0.86 1.04 0.63 4.35 10.29 68.74157.84 Quebec Carey Mines40.5~37.1% 1.09 2.02 1.98 2.02 1.93 2.484.73 Quebec ~2~
It will be readily noted that Bell tailings (1~ = 0.86) are advantageous for the production of sand-blasting material because they are more easily sintered at a temperature of around 1300C. The mechanical strength under those conditions is substantially higher than what is observed with more basic tailings as repre-sented by Carey material (1~ = 1.09~.
SANDBLASTING
For sandblasting operation, two criteria are of paramount importance to obtain high performances, that is the hardness of grains and their angular shape.
All other factors being kept equal, an angular material will lead to more efficient abrasion while a better hardness of the grains will allow a higher percentage of recycling of the sandblasting agent.
Since a tailings with a basicity index lower than one can be sintered at a lower temperature than basic tailings, it would be obvious to select such low basicity tailings as starting material. We have found in practice that tailings such as those of Bell Mine, with a basicity index of the order of 0.86, when fired for one hour at 1300C, gave a high performance material for sandblasting.
The calcined material has to be sieved in order to give an adequate sandblasting agent. For coarse sandblasting, a granulometr~ of 16 to +60 mesh (Tyler) has been found adequate whereas for finer work -.i, including p~lishing, the mesh size can be from -40 to values as low as +150 mesh (Tyler).
Using standard methods in sandblasting indus-try, it has now been established that calcined tailings are more efficient than silica as sandblasting agent while generating less dust and being more easily re-cycled. Those advantageous performances are clearly shown by Tables II and III.
TABLE II
SANDBLASTING OF UNIT SURFACE OF MILD STEEL
Material usedMesh sizeUnit su.rface cleaned/min.
for sandblasting (Tyler) (cm2/min.) Laboratory test Field test Calcined tailings Bell, 1300C -16 ~60 82.1 3716 Silica Ottawa/ round-30 +60 52.5 2601 shaped grains Silica Xndusmin, angular -20 ~50 79.7 shaped grains i TABLE III
Mesh size Calcined tailings Ottawa sand Indusmin Sand Slag sand (Tyler~ Bell 1300C
Initial10 usesInitial10 usesInitial10 uses Initial 10 uses (%) (~) (%) (%) (%) (%) +20 43.715.7 0.2 0.2 18.0 0.5 20~7 5.
+3~ 28~524.7 9.7 5.0 41.7 4.1 32.8 11.3 +40 15.123.0 43.6 38.3 20.6 8.6 20.5 12.6 +50 12.612.8 13.6 21.~ 12O3 11.0 13.7 11.9 +60 0.13.9 2~.3 5.9 3~4 ~.0 4.5 5.6 +80 0 5.0 11.1 7.4 ~.7 10.7 4~3 8.7 Dust 014.9 1.5 21.6 1.3 59.1 3.5 44.5 Total~ 100.0100.0100.0 100.0 100.0 100.0 100.0 100.0 It will be readily not~d from Table II that material having round grains is not very efficient for sandblasting. The comparison of either calcined tailings or angular silica (Indusmin) to smooth silica is very illuminating on that point: the unexpected improvement obtained with a grain having an angular structure is of 50% over the smooth grains. It must be underlined that the ratio of field performances between calcined tailings and silica (1.42) is very close to the same ratio determined at a smaller scale, in laboratory test (1.56).
However, beside intrinsic abrading power, one must take into account the sturdiness of abrading grains since too soft a material will prevent economic re-cycling o~ the sandblasting agPnt. Examination of Table III shows clearly the advantage of using calcined tailings over other products that reveal themselves, upon use, as either too fragile or too friable to allow recycling. It is obvious that any material containing from 20 to 50% of fines is not worth a recycling oper--ation.
From observations confirmed ~y field tes~s, i~
can be said that calcined tailings still can be used ef-ficiently as sandblasting agent after 20 cycles whereas other material like silica cannot stand lO cycles.
Therefore, it is obvious from these data that calcined tailings, because of their angular shape and good hardness resulting of sintering in the course of the firing operation, appear as a significantly superior material for sandblasting. Beside its intrinsic abrad-ing performances, it generates less dust and allows recycling.
Table IV illustrates clearly the better hard-ness o~ grain shown by calcined tailings in comparison with a silica having an angular shape (Indusmin). This hardness must be understood as the resistance to frac-ture and is best appreciated by repetitive uses of thesand while evaluating the increase fraction of dust.
Indusmin silica sand is used because its performances as an abrasive, as per Table II, are only slightly lower than calcined tailings. It will be readily noted that the attrition on the Indusmin sand is much more severe than in the case of calcined tailingsO
~18 TABTE IV
ATTRITIQN OF THE GRANULES PER CYCLE
Per cent fraction smaller than B0 mesh (Tyler) Number of cycles Calcined tailings Indusmin Bell, 1300C
0 0 1.3 2 2.98 11~57
4 5.66 22.~6 6 8.81 35.21 8 12.09 ~8.05 14.9 59.1 It will be noted from Table IV that the rate o~ attrition is about 3.8 times less after two uses and about 4 times less after ten uses of calcined asbestos tailings when compared to Indusmin.
The present invention will be more readily under~tood by reerring to the following Example.
EX~MPLE 1 In a Matfer vacuum sandblas~ing chamber (5 pound chamber), a 30 cm by 30 cm mild steel plate heavily coated with rust was clamped. A stream of sand-hlasting tailings (prepared from tailings from Bell mine, 1~: 0.36 and calcined at 1300C, -16 mesh, ~60 mesh Tyler) was directed from a 10 mm nozzle with an air presence of 100 psi. The angle of the stream in refer-ance to the steel plate was 45 at a distance of 15 cm.
The rate o~ cleaning of the surface was 82.1 cm /min.
With Ottawa silica, the rate of cleaning was 52.5 cm2/min. and with Indusmin sand, 79.7 cm2/min. In field tests the rate of cleaning was 3~716 cm2/min. for the sandblasting tailings of the present invention and only 2.601 cm2/min. for Ottawa round shaped grains.
!
The present invention will be more readily under~tood by reerring to the following Example.
EX~MPLE 1 In a Matfer vacuum sandblas~ing chamber (5 pound chamber), a 30 cm by 30 cm mild steel plate heavily coated with rust was clamped. A stream of sand-hlasting tailings (prepared from tailings from Bell mine, 1~: 0.36 and calcined at 1300C, -16 mesh, ~60 mesh Tyler) was directed from a 10 mm nozzle with an air presence of 100 psi. The angle of the stream in refer-ance to the steel plate was 45 at a distance of 15 cm.
The rate o~ cleaning of the surface was 82.1 cm /min.
With Ottawa silica, the rate of cleaning was 52.5 cm2/min. and with Indusmin sand, 79.7 cm2/min. In field tests the rate of cleaning was 3~716 cm2/min. for the sandblasting tailings of the present invention and only 2.601 cm2/min. for Ottawa round shaped grains.
!
Claims
1. A sintered angular shape granular sand-blasting material obtained by the calcination of asbestos tailings at a temperature of from 1300°C to 1450°C, said asbestos tailings being characterized by having a MgO:SiO2 ratio lower than 1.0, the granular sandblasting material being characterized by a cold compression mechanical strength of from 10 to 160 MPa, by a granulometry of -40 to +150 mesh (Tyler), and by being substantially free of dust.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000454993A CA1208918A (en) | 1984-05-24 | 1984-05-24 | Calcined serpentine useful as sandblasting agent |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000454993A CA1208918A (en) | 1984-05-24 | 1984-05-24 | Calcined serpentine useful as sandblasting agent |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1208918A true CA1208918A (en) | 1986-08-05 |
Family
ID=4127922
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000454993A Expired CA1208918A (en) | 1984-05-24 | 1984-05-24 | Calcined serpentine useful as sandblasting agent |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1208918A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5374593A (en) * | 1992-02-21 | 1994-12-20 | Les Sables Olimag, Inc. | Preparation of refractory materials from asbestos tailings |
| US5576255A (en) * | 1992-02-21 | 1996-11-19 | Les Sables Olimag, Inc. | Refractory sand composition |
-
1984
- 1984-05-24 CA CA000454993A patent/CA1208918A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5374593A (en) * | 1992-02-21 | 1994-12-20 | Les Sables Olimag, Inc. | Preparation of refractory materials from asbestos tailings |
| US5453408A (en) * | 1992-02-21 | 1995-09-26 | Les Sables Olimag, Inc. | Forsterite-rich refractory sand composition |
| US5576255A (en) * | 1992-02-21 | 1996-11-19 | Les Sables Olimag, Inc. | Refractory sand composition |
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