CA2084319A1 - Process for producing calcined material useful as a sandblasting agent and the material thus produced - Google Patents
Process for producing calcined material useful as a sandblasting agent and the material thus producedInfo
- Publication number
- CA2084319A1 CA2084319A1 CA 2084319 CA2084319A CA2084319A1 CA 2084319 A1 CA2084319 A1 CA 2084319A1 CA 2084319 CA2084319 CA 2084319 CA 2084319 A CA2084319 A CA 2084319A CA 2084319 A1 CA2084319 A1 CA 2084319A1
- Authority
- CA
- Canada
- Prior art keywords
- process according
- dross residue
- sandblasting
- product
- dross
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K3/00—Materials not provided for elsewhere
- C09K3/14—Anti-slip materials; Abrasives
- C09K3/1409—Abrasive particles per se
- C09K3/1418—Abrasive particles per se obtained by division of a mass agglomerated by sintering
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
- B24C11/00—Selection of abrasive materials or additives for abrasive blasts
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
- C04B35/111—Fine ceramics
- C04B35/1115—Minute sintered entities, e.g. sintered abrasive grains or shaped particles such as platelets
Abstract
Abstract:
The invention relates to a process for producing a sintered material suitable for use in particular as a sandblasting agent. The process involves mixing particles of aluminum dross residue and particles of serpentine-containing asbestos tailings to form a solids mixture and heating the solids mixture in an oxidizing atmosphere (e.g. air) at a temperature in the range of 1250-1600°C for a period of time long enough to form a sintered product. After cooling, the product is ground to an appropriate particle size, e.g. minus 70 Tyler mesh. The material has high fracture toughness and is suitable for sandblasting applications. The product generally contains regions of spinel and .alpha.-alumina sintered with regions of olivine.
The invention relates to a process for producing a sintered material suitable for use in particular as a sandblasting agent. The process involves mixing particles of aluminum dross residue and particles of serpentine-containing asbestos tailings to form a solids mixture and heating the solids mixture in an oxidizing atmosphere (e.g. air) at a temperature in the range of 1250-1600°C for a period of time long enough to form a sintered product. After cooling, the product is ground to an appropriate particle size, e.g. minus 70 Tyler mesh. The material has high fracture toughness and is suitable for sandblasting applications. The product generally contains regions of spinel and .alpha.-alumina sintered with regions of olivine.
Description
- 208~319 ~rocess for producina calcined material useful as a sandblastina aaent and the material thus ~roduced BACKGROUND OF THE INVENTION
I. FIELD OF THE INVENTION
This invention relates to a process for producing a particulate heat-treated material useful, in particular, as a sandblasting agent, and the material thus produced.
II. DESCRIPTION OF THE PRIOR ART
Canadian Patent 1,208,918 granted to Ceram-SNA Inc.
on August 5, 1986 discloses a process for producing a sandblasting agent comprising small particles of a modified serpentine material. This material is produced by the calcination of asbestos tailings having a basicity index (1~) (i.e. an MgO:SiO2 ratio) lower than 1.0 at a calcination temperature of 1300 to 1450-C. The resulting material is said to have a cold compression mechanical strength of from 10.0 to 160 MPa and a granulometry in the range of minus 40 to plus 150 Ty _ mesh and is substantially free of dust (i.e.
particles smaller than 200 Tyler mesh).
Serpentine is an hydrated variety of magnesium silicate that occurs naturally in very large deposits, and is available .,~,.!
in large amounts, particularly as rejects or tailings from asbestos mining. A thermal treatment should in principle be able to transform this material into an anhydrous magnesium silicate as ~ollows:
3MgO.2SiO2.2H20 ~ 3MgO-2SiO2 + 2H20 (asbestosta~gs) .
However, it is well known to those familiar in the art of calcined products that a calcining operation carried out on serpentine, especially when accompanied by gas evolution from the calcined species, may lead to a very fragile and porous product. Nevertheless, the patentees of the above-mentioned patent reported that the use of temperatures within the specific range mentioned above produces a granular material hard enough to be used as a sandblasting agent.
Despite this assertion, we have found that the product , ~ .
2o8~319 produced according to this process, while having a relatively high hardness range of 6.5 to 7 Mohs, does not in fact have a - high fracture toughness and consequently may not be as useful for sandblasting applications as materials of higher fracture toughness.
While it may initially seem desirable to use particles of high hardness for sandblasting applications, such particles may nevertheless be brittle and may consequently have a tendency to disintegrate rapidly to dust during use.
OBJECTS OF THE INVENTION
Accordingly, an ob~ect o~ the present invention is to provide a process for producing a heat treated material suitable in particular ~or sandblasting that has good fracture toughness, durability and sandblasting capabilities.
Another ob;ect of the present invention, at least in its preferred forms, is to provide such a process capable of being operated relatively economically in terms of the cost of the starting materials and the energy input required.
Yet another object of the present invention, at least in its preferred forms, is to utilize waste aluminum dross resi-due to form a useful and valuable product that causes little or no environmental pollution when disposed of after use.
~QMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a process for producing a sintered particulate material suitable for use as a sandblasting agent. The process involves mixing particles of aluminum dross residue and particles of serpentine-containing material, preferably asbestos tailings, to form a solids mixture, heating the -solids mixture to a temperature in the range of 1250-1600C
for a period of time long enough to form a sintered product, allowing the product to cool and then grinding the sintered product to a predetermined particle size range.
According to another aspect of the invention there is provided a particulate sandblasting material comprising regions of alumina and spinel sintered with olivine.
The invention has the advantage that a durable material .;~ ' ' :
-` 20~3t g of suitable fracture toughness for use as a sandblasting agent can be produced at relatively low cost from materials that are often discarded as waste. Furthermore, the process makes it possible to utilize aluminum dross residue in an effective manner and thus avoid the problems associated with conventional disposal of this waste material (i.e. the generation of ammonia and unacceptable leaching of fluorides or salts~.
BRIEF DESCRIPTION OF THE ~RAWINGS
Figure 1 is a phase equilibrium diagram of oxide systems of silicon, magnesium and aluminum;
Figure 2 is a schematic representation of a grinding process carried out on a product according to the invention;
Figure 3 is a graph showing the size distributions of the starting materials and product produced according to a preferred form of the present invention; and Figure 4 is a graph of relative sandblasting speeds for three sandblasting products, one being according to the invention.
DETAI~ED DESCRIPTION OF THE INVENTION
We have unexpectedly found that the process of Canadian Patent 1,208,918 can be modified or changed to produce a material that i5 highly suitable as a sandblasting agent by heating a mixture of an aluminum dross residue and serpentine, preferably from asbestos tailings, rather than by calcining serpentine alone. Surprisingly, these two materials strongly sinter together at the relatively low temperatures of 1250-1600-C (more preferably 1300-1500-C) to produce a particulate product usually containing regions of alumina and magnesium spinel and regions of olivine strongly sintered together. The resulting particles tend to be larger than those of the original starting materials and are generally in the range of 0 to about 4 inches in diameter prior to any grinding that may be carried out. The hardness value of alumina itself is 9 Mohs and thus the alumina content of the sintered product may increase the overall hardness of the resulting sandblasting agent. However, the fracture toughness of the resulting : ..... . , :
: ~ . . . .
.
' -' ~'.~; : ..
208~319 sintered material is very high (although difficult to measure quantitatively) and this makes the product suitable as a sandblasting agent when reduced to an appropriate particle size range. An indication of high fracture toughness is the generation of little dust (particles smaller than 200 Tyler mesh) during sandblasting operations and the product of the invention is satisfactory in this respect.
Aluminum dross residue is used in the present invention as a source of alumina and is preferred to the use of either pure alumina or alumina from other sources because its use surprisingly results in thorough sintering with the serpentine-containing asbestos tailings during the heat treatment. This in turn results in the formation of large product particles which can then be ground and classified.
The use of pure alumina, for example, results in the production of small easily fractured particles. It therefore ~ ;
seems that the impurities in the dross residue (e.g. AlN) facilitate the sintering process, but it is not at present clear why this should be the case. In any event, we have found that products of the present invention made when using plasma dross residue as an alumina source result in less consumption of the sandblasting agent in sandblasting tests compared with sandblasting agents produced according to the Ceram-SNA Inc. patent, or when using pure alumina in the process of the invention. This indicates that a stronger and harder product may be produced.
Aluminum dross is formed whenever aluminum or an aluminum alloy is melted in air or other oxidizing atmosphere and is thus obtained in large quantities in aluminum production and fabrication plants. The dross is normally treated to remove recoverable aluminum metal in order to leave a dross residue -~
of reduced metal content. The precise way in which the aluminum is removed from the dross affects the nature of the dross residue and, to a certain extent, the way in which the dross residue should be treated before it is used in the present invention. For this reason, a description of dross treatment methods is provided briefly below.
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First of all, aluminum-containing dross may be heated by a thermal plasma while being agitated in a rotatable furnace according to the method described in prior Canadian Patent No.
1,255,914 issued on June 20, 1989. This procedure causes residual metal particles in the dross to melt and coalesce and form a continuous phase which can then be tapped off. If the plasma is produced by means of a plasma torch operated with nitrogen gas, aluminum nitride may be present in the resulting dross residue as well as alumina. Steps are often taken to avoid the formation of aluminum nitride in this way because it decomposes to alumina and ammonia gas when exposed to moisture, for example when dumped in landfill sites, and the resulting generation of ammonia is considered to be an unacceptable pollutant (limited to 25 ppm by the EPA in the United States). However, for the reasons given below, the presence of aluminum nitride in the dross residue is advantageous in the present invention.
A more conventional way of treating aluminum dross to remove contained aluminum is to heat the dross in a conventional furnace with a salt mixture which reduces the surface tension of the molten aluminum and causes the aluminum droplets to coalesce. Disadvantageously, this produces a dros5 of high salt content which i8 polluting if discarded in this form. Moreover, this salt-containing dross cannot be used directly in the process of the present invention because the salt adversely affects the nature of the fused product and eventually leaches out of the material to cause pollution.
The dross residue from the salt process should therefore first be subjected to a washing step with water in order to dissolve away the salt content before being used in the present invention. After such washing, the dross contains hydrated alumina and should be heated to a temperature above at least 250C for a sufficient time to remove chemically combined water.
The dross residue produced by either of the above processes has a high alumina to silica ratio (the silica '~ .'s .-.. : .. . . . : - . , -:...
: ~ ~ . - :. - .
2as~3ls content, if any, usually amounts to just a few percent). The dross residue usually contains a minimum of 50~ alumina (or alumina precursor) and generally at least 75%. The dross residue normally also contains magnesium oxide (in the form of spinel, MgAl204), if the dross was initially formed on magnesium-containing aluminum alloys. Other components are usually CaO, silica, other refractory oxides and a small percentage of residual aluminum metal.
A typical range of compositions of plasma treated dross residue is shown in ~able 1 below.
~' L Composition Percentage (wt.) Al23 50-100 AlN 0-30 Al metal 0-10 ¦ MgO 0-50 ¦
SiO2 0-10 NaF 0-4 CaF2 0-~
' , ~
Dross residue from the salt process, after washing with water to remove most of the salt, would have a similar composition but would contain up to 10% by wt of residual salt (e.g. NaCl, MgCl2 and/or KCl).
When AlN is present in the dross residue, during the dehydration of the serpentine in the asbestos tailings, the released water contributes to the hydrolysis of the AlN
according to the following chemical reaction:
2AlN + 3H20 ~ Al203 + 2NH3t .
~. . :', ~' , - ' ' ' .
: - . .
- ;
: ., ~ .. .
,.. '' . ' ' ~, . ~ ~ .
Any remaining AlN (depending on the quantity of the AlN
present) is directly oxidized at temperatures above 1250C as follows:
2AlN + 2 2 A1203 ~ N2t ~ hese two reactions generally lead to a product which contains }ess than 1.0% AlN after the heat treatment, which has the advantage that once the product has been used, it can be discarded without causing unacceptable environmental pollution due to the generation of ammonia.
Furthermore, the oxidation of aluminum nitride indicated above is exothermic and thus heat is generated while this reacticn takes place during the heat treatment of the starting materials. Consequently, less external heat is then required to raise the temperature to the calcination range and to maintain it there than would be the case for an alumina-containing material containing no such aluminum nitride. The presence o~ aluminum nitride in the starting material is therefore desirable in the present invention. Nost pre~erably, the alumina-containing material (dross residue) contains at least 16 % by weight of AlN.
A 5imilar heat contribution can be made by the oxidation of residual metallic aluminum contained in the dross residue.
At temperatures above about 850-C, the following strongly exothermic reaction takes place, again reducing the amount of external heating required for the process:
2Al + 2 2 ' Al23 Advantageously, the amount of residual metallic aluminum in the dross residue is about 8 % by weight. When the metallic Al content is too high (e.g. more than 8 ~ and especially more than 10 % by weight), unreacted metallic Al may remain in the product after the heat treatment, adversely , . ~ . .. .. .
7., , ,, , ~ ., , , . . '.... ' '' ' , .' ~ '. ': ' 2~8~319 affecting the properties of the sintered material. This should be avoided, if possible.
The heat content (energetic value) of plasma dross residue containing AlN and metallic Al has been estimated at 1250 kWh/tonne, so it is not surprising that the external heat input can be significantly reduced when such material is used.
Another surprising discovery is that the fluorides normally present in dross residue, which can lead to environmental pollution due to leaching, seem to be stabilized by the serpentine when used in the reaction of the present invention, perhaps as MgF2, and seem to become bound to the mineral structure rather than remaining free. The resulting sandblasting agent, after use, can thus also be discarded without risk of environmental pollution from this source.
It will therefore be seen that there are many advantages to using aluminum dross residue, and particularly plasma dross, as a starting material in the present invention while concerns about possible pollution caused by the resulting product as a result of the impurities in the dross are not 20 realized.
The amount of aluminum dross residue required in the solids mixture subjected to the heat treatment in order to produce an effective increase in fracture toughness o~ the sintered particles is generally about 5 to 50% by weight, the 25 remainder being serpentine-containing material, preferably asbestos tailings.
While serpentine-containing material from sources other than asbestos tailings may be used in the process o~ the present invention, it is found that asbestos tailings are 30 preferred not only because they are inexpensive and readily available in large amounts, but also because they tend to have more uniform composition range and thus produce a consistent product. For example, chemical analyses of serpentine-containing materials from various asbestos tailings range as 35 follows: SiO2, 33-44%; MgO, 30-44%; FeO, 0-6%; Fe203, 0.1-5%;
Alz03, 0.2-1.5~; CaO, trace-5%; and H20, 12-15% by weight.
While the asbestos tailings preferably have a basicity ,;. : . . -, ~ . .
.
, . . ~ ~ . . : . - .
index (lB) lower than l, as in the Ceram-SNA product described above, those having higher basicity indices may be used, although the required heat treatment temperatures are then undesirably higher in order to obtain products of suitable properties. It seems that materials having lower basicity indices reduce the vitrification temperature and lead to a stronger product.
Both the aluminum dross residue and the asbestos tailings should be in the form o~ relatively fine particles so that fairly thorough mixing can be achieved quite easily. In the case of the dross residue, the preferred size range is less than 1 inch to larger than 100 Tyler mesh. In the case of the asbestos tailings, the preferred size range is less than 3/4 inch to larger than 1/16 or even 1/8 inch. If necessary, the starting materials may be ground to produce particles in these size ranges.
The heat treatment is carried out by heating the mixture in an oxidizing atmosphere (preferably air) at a temperature of 1250 to 1600-C, preferably 1300 to 1500-C, usually for 30 to 90 minutes or as long as required to produce the desired calcination (moisture removal) and sintering. The heat treatment is most preferably carried out in a rotatable kiln to bring about gentle agitation of the reacting solids, but could alternatively be carried out using a rotary batch furnace, a vertical shaft furnace or any other suitable furnace or oven.
X-ray diffraction analysis of the products according to the invention normally shows the presence of two major phases, namely magnesium spinel (MgAl2O4) and forsterite (Mg2SiO4).
Corundum (~-Al203) and enstatite (MgO.SiO2) are also usually present. In fact, the product usually comprises olivine (a solid solution of forsterite, fayalite [2FeO.SiO2] and enstatite) sintered with magnesium spinel and corundum (when there is not enough magnesium oxide available to transform completely the alumina to spinel). Figure l of the accompanying drawings illustrates (in the hatched area A) the localization of the resulting reacted product in the - - . : - . -. ~. . ~ ,, . " , . : ,, . . - .
MgO.SiO2.Al203 phase diagram.
The product produced by the heat treatment, after -suitable cooling, is generally too large to be used directly as a sandblasting agent and is consequently ground to about minus 16 to plus 70 Tyler mesh, preferably using a grinding process of the kind illustrated in Figure 2 of the accompanying drawings. This grinding process involves passing the as-sintered material which, as noted above, may be in the form of particles up to 4 inches in diameter, first through a jaw crusher to produce particles 3/4 inch in size or smaller, and then through a cone crusher to produce particles 3/16 inch in size or smaller. The product is passed through a screen (preferably 16 Tyler mesh) and the particles retained on the screen are further crushed in a horizontal hammer mill until they are sized to pass through the screen. The resulting ~ ~ -material is fed to a 70 Tyler mesh screen. The plus 70 Tyler mesh material is generally suitable as a sandblasting agent.
The minus 70 Tyler mesh material may be suitable as a finer sandblasting material or may be used for other applications.
While the product of the invention is primarily intended ior use as a sand~lasting agent, its high alumina content makes it suitable in refractory applications, e.g. as foundary sand for moulds. When used as such, the product may be used, for example, in cast iron foundries at temperatures up to 1600-C.
The process of the present invention is illustrated and the advantages of the invention are confirmed by the following Examples, which are not intended to limit the scope of the present invention.
Exam~le 1 Plasma dross residue from the Guillaume-Tremblay plant, Quebec, containing 16% by weight of AlN and 8% by weight of metallic Al and serpentine-containing asbestos tailings from Thetford Mines, Quebec, were mixed together to the extent that the plasma dross residue made up 27% by weight of the result-ing mixture. The mixture was heated at a temperature of 1433'C for 60 minutes in a rotary furnace open to the . .- ~ ~. . . .
. . - .
, . -:- , ~ - - :
.. ~,; .. , - -,. :.
.
atmosphere. The product was allowed to cool and was then subjected to chemical analysis, indicating the following composition: :
.
CompositionPercentage (by wt) ¦
ioz 36.00 I
MgO 29.70 I
¦ CaO 0.67 l Fe23 6.57 Al23 27.60 MnO 0.26 N~20 0.63 i K20 0.13 I
¦ Tio2 o. os AlN <0.5 The product was also sub~ected to X-ray di~raction analysis with the following results:
Relative Phase or Chemical concentration compound formula ¦Major Forsterite Mg2SiO4 ¦Major Spinel MgAl204 I .
Nedium Corundum ~-Al20 I I
¦Minor Enstatite MgS io ,- . ,. ~ -.- , .:
- .. , .. . ,: - .- - , .
~. .. - . ... - . . . ~ . . . -The size distributions of the starting materials and reacted material is shown in Figure 3 of the accompanying drawings. From this, it will be seen that the reacted material was, before grinding, of coarser particle size than both the plasma dross residue and the asbestos tailings used as the starting materials.
The product was then subjected to a grinding process of the type shown in Figure 2 and the size distribution of the resulting product is shown in Table 4 be}ow.
~AB~ 4 _ .
Screen (Tyler mesh) Retained %
100 19 ' ~ ~
¦ PAN 22 Example 2 The following test was carried out in order to assess the heat benefit of the aluminum nitride and metallic aluminum contents of plasma dross residue during the heat treatment of the invention.
Plasma dross residue containing 16 % by weight of AlN and 8 % by weight of metallic Al was used in the following.
Tests were carried out calcining 100% asbestos tailings, a mixture of 75% by weight of asbestos tailings and 25% by weight of plasma dross residue and a mixture of 50% by weight of asbestos tailings and 50% by weight of plasma dross residue at the same temperature for the same time and measuring the consumption of oil required to operate the furnace. The results are shown in Table 5 below.
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r~
208~319 .
TAsLB 5 OIL CONSUMPTION PER POUND OF REACTED MATERIAL HEATED AT 1350c ¦ Matenal heat treated Oil consumption, L/lb Ener~y Sa~ing, %
¦ 100% Asbestos residue 0.114 I
75% Asbestos residue/0.087 23.7 25% Plasma Dross Residue ¦
. I
50% Asbestos residue/0.077 32.5 ¦ 50% Plasma Dross Residue From the result shown in this Table, it can be seen that the use of the plasma dross residue results in a significant energy saving for the operation of the heat treatment derived from the oxidation of metallic aluminum and aluminum nitride to alumina. ~hese energy savings amount to approximately 24 and 33% for the 25% and 50% plasma dross mixtures compared 15 with alumina alone.
~xample 3 The ~ollowing test was carried out to compare the e~ects o~ the u~e o~ plasma dross residue o~ the type used in Example 2 above and pure alumina, respectively, on the sintering properties of the heat treated mixture with asbestos tailings. The results are shown in Table 6 below.
~A ' _: , _. , ~ ~ ' , . _ ' ' ' ,, ` - ' ' ' ' ' f .
20843~9 SINTERING PROPERTIES OF NOVALTM AND PURE ALUMINA
WITH THE ASBESTOS TAILING RESIDUE
¦ Sample, Calanation Composition of the mixture, % by wt Remarks # temperature, C Asbestos Tailings Dross 1 1426 90 10 strongly sintered product 2 1432 50 50 strongly sintered product 3 1421 25 75 strongly sintered product (5% metallic Al) Asbestos Tailings Alumina ¦
I. FIELD OF THE INVENTION
This invention relates to a process for producing a particulate heat-treated material useful, in particular, as a sandblasting agent, and the material thus produced.
II. DESCRIPTION OF THE PRIOR ART
Canadian Patent 1,208,918 granted to Ceram-SNA Inc.
on August 5, 1986 discloses a process for producing a sandblasting agent comprising small particles of a modified serpentine material. This material is produced by the calcination of asbestos tailings having a basicity index (1~) (i.e. an MgO:SiO2 ratio) lower than 1.0 at a calcination temperature of 1300 to 1450-C. The resulting material is said to have a cold compression mechanical strength of from 10.0 to 160 MPa and a granulometry in the range of minus 40 to plus 150 Ty _ mesh and is substantially free of dust (i.e.
particles smaller than 200 Tyler mesh).
Serpentine is an hydrated variety of magnesium silicate that occurs naturally in very large deposits, and is available .,~,.!
in large amounts, particularly as rejects or tailings from asbestos mining. A thermal treatment should in principle be able to transform this material into an anhydrous magnesium silicate as ~ollows:
3MgO.2SiO2.2H20 ~ 3MgO-2SiO2 + 2H20 (asbestosta~gs) .
However, it is well known to those familiar in the art of calcined products that a calcining operation carried out on serpentine, especially when accompanied by gas evolution from the calcined species, may lead to a very fragile and porous product. Nevertheless, the patentees of the above-mentioned patent reported that the use of temperatures within the specific range mentioned above produces a granular material hard enough to be used as a sandblasting agent.
Despite this assertion, we have found that the product , ~ .
2o8~319 produced according to this process, while having a relatively high hardness range of 6.5 to 7 Mohs, does not in fact have a - high fracture toughness and consequently may not be as useful for sandblasting applications as materials of higher fracture toughness.
While it may initially seem desirable to use particles of high hardness for sandblasting applications, such particles may nevertheless be brittle and may consequently have a tendency to disintegrate rapidly to dust during use.
OBJECTS OF THE INVENTION
Accordingly, an ob~ect o~ the present invention is to provide a process for producing a heat treated material suitable in particular ~or sandblasting that has good fracture toughness, durability and sandblasting capabilities.
Another ob;ect of the present invention, at least in its preferred forms, is to provide such a process capable of being operated relatively economically in terms of the cost of the starting materials and the energy input required.
Yet another object of the present invention, at least in its preferred forms, is to utilize waste aluminum dross resi-due to form a useful and valuable product that causes little or no environmental pollution when disposed of after use.
~QMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a process for producing a sintered particulate material suitable for use as a sandblasting agent. The process involves mixing particles of aluminum dross residue and particles of serpentine-containing material, preferably asbestos tailings, to form a solids mixture, heating the -solids mixture to a temperature in the range of 1250-1600C
for a period of time long enough to form a sintered product, allowing the product to cool and then grinding the sintered product to a predetermined particle size range.
According to another aspect of the invention there is provided a particulate sandblasting material comprising regions of alumina and spinel sintered with olivine.
The invention has the advantage that a durable material .;~ ' ' :
-` 20~3t g of suitable fracture toughness for use as a sandblasting agent can be produced at relatively low cost from materials that are often discarded as waste. Furthermore, the process makes it possible to utilize aluminum dross residue in an effective manner and thus avoid the problems associated with conventional disposal of this waste material (i.e. the generation of ammonia and unacceptable leaching of fluorides or salts~.
BRIEF DESCRIPTION OF THE ~RAWINGS
Figure 1 is a phase equilibrium diagram of oxide systems of silicon, magnesium and aluminum;
Figure 2 is a schematic representation of a grinding process carried out on a product according to the invention;
Figure 3 is a graph showing the size distributions of the starting materials and product produced according to a preferred form of the present invention; and Figure 4 is a graph of relative sandblasting speeds for three sandblasting products, one being according to the invention.
DETAI~ED DESCRIPTION OF THE INVENTION
We have unexpectedly found that the process of Canadian Patent 1,208,918 can be modified or changed to produce a material that i5 highly suitable as a sandblasting agent by heating a mixture of an aluminum dross residue and serpentine, preferably from asbestos tailings, rather than by calcining serpentine alone. Surprisingly, these two materials strongly sinter together at the relatively low temperatures of 1250-1600-C (more preferably 1300-1500-C) to produce a particulate product usually containing regions of alumina and magnesium spinel and regions of olivine strongly sintered together. The resulting particles tend to be larger than those of the original starting materials and are generally in the range of 0 to about 4 inches in diameter prior to any grinding that may be carried out. The hardness value of alumina itself is 9 Mohs and thus the alumina content of the sintered product may increase the overall hardness of the resulting sandblasting agent. However, the fracture toughness of the resulting : ..... . , :
: ~ . . . .
.
' -' ~'.~; : ..
208~319 sintered material is very high (although difficult to measure quantitatively) and this makes the product suitable as a sandblasting agent when reduced to an appropriate particle size range. An indication of high fracture toughness is the generation of little dust (particles smaller than 200 Tyler mesh) during sandblasting operations and the product of the invention is satisfactory in this respect.
Aluminum dross residue is used in the present invention as a source of alumina and is preferred to the use of either pure alumina or alumina from other sources because its use surprisingly results in thorough sintering with the serpentine-containing asbestos tailings during the heat treatment. This in turn results in the formation of large product particles which can then be ground and classified.
The use of pure alumina, for example, results in the production of small easily fractured particles. It therefore ~ ;
seems that the impurities in the dross residue (e.g. AlN) facilitate the sintering process, but it is not at present clear why this should be the case. In any event, we have found that products of the present invention made when using plasma dross residue as an alumina source result in less consumption of the sandblasting agent in sandblasting tests compared with sandblasting agents produced according to the Ceram-SNA Inc. patent, or when using pure alumina in the process of the invention. This indicates that a stronger and harder product may be produced.
Aluminum dross is formed whenever aluminum or an aluminum alloy is melted in air or other oxidizing atmosphere and is thus obtained in large quantities in aluminum production and fabrication plants. The dross is normally treated to remove recoverable aluminum metal in order to leave a dross residue -~
of reduced metal content. The precise way in which the aluminum is removed from the dross affects the nature of the dross residue and, to a certain extent, the way in which the dross residue should be treated before it is used in the present invention. For this reason, a description of dross treatment methods is provided briefly below.
;' , .
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, ~ . .
First of all, aluminum-containing dross may be heated by a thermal plasma while being agitated in a rotatable furnace according to the method described in prior Canadian Patent No.
1,255,914 issued on June 20, 1989. This procedure causes residual metal particles in the dross to melt and coalesce and form a continuous phase which can then be tapped off. If the plasma is produced by means of a plasma torch operated with nitrogen gas, aluminum nitride may be present in the resulting dross residue as well as alumina. Steps are often taken to avoid the formation of aluminum nitride in this way because it decomposes to alumina and ammonia gas when exposed to moisture, for example when dumped in landfill sites, and the resulting generation of ammonia is considered to be an unacceptable pollutant (limited to 25 ppm by the EPA in the United States). However, for the reasons given below, the presence of aluminum nitride in the dross residue is advantageous in the present invention.
A more conventional way of treating aluminum dross to remove contained aluminum is to heat the dross in a conventional furnace with a salt mixture which reduces the surface tension of the molten aluminum and causes the aluminum droplets to coalesce. Disadvantageously, this produces a dros5 of high salt content which i8 polluting if discarded in this form. Moreover, this salt-containing dross cannot be used directly in the process of the present invention because the salt adversely affects the nature of the fused product and eventually leaches out of the material to cause pollution.
The dross residue from the salt process should therefore first be subjected to a washing step with water in order to dissolve away the salt content before being used in the present invention. After such washing, the dross contains hydrated alumina and should be heated to a temperature above at least 250C for a sufficient time to remove chemically combined water.
The dross residue produced by either of the above processes has a high alumina to silica ratio (the silica '~ .'s .-.. : .. . . . : - . , -:...
: ~ ~ . - :. - .
2as~3ls content, if any, usually amounts to just a few percent). The dross residue usually contains a minimum of 50~ alumina (or alumina precursor) and generally at least 75%. The dross residue normally also contains magnesium oxide (in the form of spinel, MgAl204), if the dross was initially formed on magnesium-containing aluminum alloys. Other components are usually CaO, silica, other refractory oxides and a small percentage of residual aluminum metal.
A typical range of compositions of plasma treated dross residue is shown in ~able 1 below.
~' L Composition Percentage (wt.) Al23 50-100 AlN 0-30 Al metal 0-10 ¦ MgO 0-50 ¦
SiO2 0-10 NaF 0-4 CaF2 0-~
' , ~
Dross residue from the salt process, after washing with water to remove most of the salt, would have a similar composition but would contain up to 10% by wt of residual salt (e.g. NaCl, MgCl2 and/or KCl).
When AlN is present in the dross residue, during the dehydration of the serpentine in the asbestos tailings, the released water contributes to the hydrolysis of the AlN
according to the following chemical reaction:
2AlN + 3H20 ~ Al203 + 2NH3t .
~. . :', ~' , - ' ' ' .
: - . .
- ;
: ., ~ .. .
,.. '' . ' ' ~, . ~ ~ .
Any remaining AlN (depending on the quantity of the AlN
present) is directly oxidized at temperatures above 1250C as follows:
2AlN + 2 2 A1203 ~ N2t ~ hese two reactions generally lead to a product which contains }ess than 1.0% AlN after the heat treatment, which has the advantage that once the product has been used, it can be discarded without causing unacceptable environmental pollution due to the generation of ammonia.
Furthermore, the oxidation of aluminum nitride indicated above is exothermic and thus heat is generated while this reacticn takes place during the heat treatment of the starting materials. Consequently, less external heat is then required to raise the temperature to the calcination range and to maintain it there than would be the case for an alumina-containing material containing no such aluminum nitride. The presence o~ aluminum nitride in the starting material is therefore desirable in the present invention. Nost pre~erably, the alumina-containing material (dross residue) contains at least 16 % by weight of AlN.
A 5imilar heat contribution can be made by the oxidation of residual metallic aluminum contained in the dross residue.
At temperatures above about 850-C, the following strongly exothermic reaction takes place, again reducing the amount of external heating required for the process:
2Al + 2 2 ' Al23 Advantageously, the amount of residual metallic aluminum in the dross residue is about 8 % by weight. When the metallic Al content is too high (e.g. more than 8 ~ and especially more than 10 % by weight), unreacted metallic Al may remain in the product after the heat treatment, adversely , . ~ . .. .. .
7., , ,, , ~ ., , , . . '.... ' '' ' , .' ~ '. ': ' 2~8~319 affecting the properties of the sintered material. This should be avoided, if possible.
The heat content (energetic value) of plasma dross residue containing AlN and metallic Al has been estimated at 1250 kWh/tonne, so it is not surprising that the external heat input can be significantly reduced when such material is used.
Another surprising discovery is that the fluorides normally present in dross residue, which can lead to environmental pollution due to leaching, seem to be stabilized by the serpentine when used in the reaction of the present invention, perhaps as MgF2, and seem to become bound to the mineral structure rather than remaining free. The resulting sandblasting agent, after use, can thus also be discarded without risk of environmental pollution from this source.
It will therefore be seen that there are many advantages to using aluminum dross residue, and particularly plasma dross, as a starting material in the present invention while concerns about possible pollution caused by the resulting product as a result of the impurities in the dross are not 20 realized.
The amount of aluminum dross residue required in the solids mixture subjected to the heat treatment in order to produce an effective increase in fracture toughness o~ the sintered particles is generally about 5 to 50% by weight, the 25 remainder being serpentine-containing material, preferably asbestos tailings.
While serpentine-containing material from sources other than asbestos tailings may be used in the process o~ the present invention, it is found that asbestos tailings are 30 preferred not only because they are inexpensive and readily available in large amounts, but also because they tend to have more uniform composition range and thus produce a consistent product. For example, chemical analyses of serpentine-containing materials from various asbestos tailings range as 35 follows: SiO2, 33-44%; MgO, 30-44%; FeO, 0-6%; Fe203, 0.1-5%;
Alz03, 0.2-1.5~; CaO, trace-5%; and H20, 12-15% by weight.
While the asbestos tailings preferably have a basicity ,;. : . . -, ~ . .
.
, . . ~ ~ . . : . - .
index (lB) lower than l, as in the Ceram-SNA product described above, those having higher basicity indices may be used, although the required heat treatment temperatures are then undesirably higher in order to obtain products of suitable properties. It seems that materials having lower basicity indices reduce the vitrification temperature and lead to a stronger product.
Both the aluminum dross residue and the asbestos tailings should be in the form o~ relatively fine particles so that fairly thorough mixing can be achieved quite easily. In the case of the dross residue, the preferred size range is less than 1 inch to larger than 100 Tyler mesh. In the case of the asbestos tailings, the preferred size range is less than 3/4 inch to larger than 1/16 or even 1/8 inch. If necessary, the starting materials may be ground to produce particles in these size ranges.
The heat treatment is carried out by heating the mixture in an oxidizing atmosphere (preferably air) at a temperature of 1250 to 1600-C, preferably 1300 to 1500-C, usually for 30 to 90 minutes or as long as required to produce the desired calcination (moisture removal) and sintering. The heat treatment is most preferably carried out in a rotatable kiln to bring about gentle agitation of the reacting solids, but could alternatively be carried out using a rotary batch furnace, a vertical shaft furnace or any other suitable furnace or oven.
X-ray diffraction analysis of the products according to the invention normally shows the presence of two major phases, namely magnesium spinel (MgAl2O4) and forsterite (Mg2SiO4).
Corundum (~-Al203) and enstatite (MgO.SiO2) are also usually present. In fact, the product usually comprises olivine (a solid solution of forsterite, fayalite [2FeO.SiO2] and enstatite) sintered with magnesium spinel and corundum (when there is not enough magnesium oxide available to transform completely the alumina to spinel). Figure l of the accompanying drawings illustrates (in the hatched area A) the localization of the resulting reacted product in the - - . : - . -. ~. . ~ ,, . " , . : ,, . . - .
MgO.SiO2.Al203 phase diagram.
The product produced by the heat treatment, after -suitable cooling, is generally too large to be used directly as a sandblasting agent and is consequently ground to about minus 16 to plus 70 Tyler mesh, preferably using a grinding process of the kind illustrated in Figure 2 of the accompanying drawings. This grinding process involves passing the as-sintered material which, as noted above, may be in the form of particles up to 4 inches in diameter, first through a jaw crusher to produce particles 3/4 inch in size or smaller, and then through a cone crusher to produce particles 3/16 inch in size or smaller. The product is passed through a screen (preferably 16 Tyler mesh) and the particles retained on the screen are further crushed in a horizontal hammer mill until they are sized to pass through the screen. The resulting ~ ~ -material is fed to a 70 Tyler mesh screen. The plus 70 Tyler mesh material is generally suitable as a sandblasting agent.
The minus 70 Tyler mesh material may be suitable as a finer sandblasting material or may be used for other applications.
While the product of the invention is primarily intended ior use as a sand~lasting agent, its high alumina content makes it suitable in refractory applications, e.g. as foundary sand for moulds. When used as such, the product may be used, for example, in cast iron foundries at temperatures up to 1600-C.
The process of the present invention is illustrated and the advantages of the invention are confirmed by the following Examples, which are not intended to limit the scope of the present invention.
Exam~le 1 Plasma dross residue from the Guillaume-Tremblay plant, Quebec, containing 16% by weight of AlN and 8% by weight of metallic Al and serpentine-containing asbestos tailings from Thetford Mines, Quebec, were mixed together to the extent that the plasma dross residue made up 27% by weight of the result-ing mixture. The mixture was heated at a temperature of 1433'C for 60 minutes in a rotary furnace open to the . .- ~ ~. . . .
. . - .
, . -:- , ~ - - :
.. ~,; .. , - -,. :.
.
atmosphere. The product was allowed to cool and was then subjected to chemical analysis, indicating the following composition: :
.
CompositionPercentage (by wt) ¦
ioz 36.00 I
MgO 29.70 I
¦ CaO 0.67 l Fe23 6.57 Al23 27.60 MnO 0.26 N~20 0.63 i K20 0.13 I
¦ Tio2 o. os AlN <0.5 The product was also sub~ected to X-ray di~raction analysis with the following results:
Relative Phase or Chemical concentration compound formula ¦Major Forsterite Mg2SiO4 ¦Major Spinel MgAl204 I .
Nedium Corundum ~-Al20 I I
¦Minor Enstatite MgS io ,- . ,. ~ -.- , .:
- .. , .. . ,: - .- - , .
~. .. - . ... - . . . ~ . . . -The size distributions of the starting materials and reacted material is shown in Figure 3 of the accompanying drawings. From this, it will be seen that the reacted material was, before grinding, of coarser particle size than both the plasma dross residue and the asbestos tailings used as the starting materials.
The product was then subjected to a grinding process of the type shown in Figure 2 and the size distribution of the resulting product is shown in Table 4 be}ow.
~AB~ 4 _ .
Screen (Tyler mesh) Retained %
100 19 ' ~ ~
¦ PAN 22 Example 2 The following test was carried out in order to assess the heat benefit of the aluminum nitride and metallic aluminum contents of plasma dross residue during the heat treatment of the invention.
Plasma dross residue containing 16 % by weight of AlN and 8 % by weight of metallic Al was used in the following.
Tests were carried out calcining 100% asbestos tailings, a mixture of 75% by weight of asbestos tailings and 25% by weight of plasma dross residue and a mixture of 50% by weight of asbestos tailings and 50% by weight of plasma dross residue at the same temperature for the same time and measuring the consumption of oil required to operate the furnace. The results are shown in Table 5 below.
, ~- ,: . . .:
. . . . ~, ' i.~:: . . . . .
r~
208~319 .
TAsLB 5 OIL CONSUMPTION PER POUND OF REACTED MATERIAL HEATED AT 1350c ¦ Matenal heat treated Oil consumption, L/lb Ener~y Sa~ing, %
¦ 100% Asbestos residue 0.114 I
75% Asbestos residue/0.087 23.7 25% Plasma Dross Residue ¦
. I
50% Asbestos residue/0.077 32.5 ¦ 50% Plasma Dross Residue From the result shown in this Table, it can be seen that the use of the plasma dross residue results in a significant energy saving for the operation of the heat treatment derived from the oxidation of metallic aluminum and aluminum nitride to alumina. ~hese energy savings amount to approximately 24 and 33% for the 25% and 50% plasma dross mixtures compared 15 with alumina alone.
~xample 3 The ~ollowing test was carried out to compare the e~ects o~ the u~e o~ plasma dross residue o~ the type used in Example 2 above and pure alumina, respectively, on the sintering properties of the heat treated mixture with asbestos tailings. The results are shown in Table 6 below.
~A ' _: , _. , ~ ~ ' , . _ ' ' ' ,, ` - ' ' ' ' ' f .
20843~9 SINTERING PROPERTIES OF NOVALTM AND PURE ALUMINA
WITH THE ASBESTOS TAILING RESIDUE
¦ Sample, Calanation Composition of the mixture, % by wt Remarks # temperature, C Asbestos Tailings Dross 1 1426 90 10 strongly sintered product 2 1432 50 50 strongly sintered product 3 1421 25 75 strongly sintered product (5% metallic Al) Asbestos Tailings Alumina ¦
4 1425 90 10 dus~ calcined product I
1360 50 50 lightly sintered product I . I
6 1230 25 75 not sintered L . product Samples nos. 1, 2 and 3 were produced according to the pre~ent invention and show very hard sintering.
Samples 4, 5 and 6 were produced in the same way, except that alumina was used instead of the plasma dross residue.
The samples show progressively less sintering with increasing alumina content.
Example 4 The following tests were carried out to illustrate the durability (fracture toughness) of various products when used for sandblasting.
Sandblasting tests were carried out with (a) commercial sand (MarcoT~ 24), (b) products according to Canadian Patent 1,208,918 (JetmagT~ 30-60) and (c) products according to the present invention JetplusT~ 30-60.
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- - ? `
. *"
, j ~ - . . .
The results are shown in Table 7 below.
PERFOR~LANCECOMPARISON OFTHE D~ERENTSAND BLASllNG MED~A
l M~ur~ ¦ SAND BLA~lrNG MEDLA
5properties Je~mag 3~60Marco 24Jetplus 30 . .
~epth ol 0.004~ 0.0036~0.0036 penetration, inch Sand consumpt~on, 2.31 _ l39 Lbst7lS ft2 1644 1873 Sandblasting spa:d,1.77 1.49 1.39 f~min.
Figure 4 is a graph showing the relative sandblasting speeds of the three materials.
Clearly these results show a significant advantage for the product o~ the present invention.
Example 5 Asbestos tailings (75 kg) were mixed with plasma dross residue (25 kg) from the Guillaume-Tremb}ay plant, Quebec, and ~
the mixture was heated at 1350-1500 C for 45 minutes in a ~ --pilot rotary kiln. The product thus obtained was analyzed for - -its AlN content, which was found to be below 0.5% by weight and thus essentially non-polluting when disposed of after use of the material as a sandblasting agent.
,} . - .
- .
., . i ,~ .. . - .. . . . ~. ,
1360 50 50 lightly sintered product I . I
6 1230 25 75 not sintered L . product Samples nos. 1, 2 and 3 were produced according to the pre~ent invention and show very hard sintering.
Samples 4, 5 and 6 were produced in the same way, except that alumina was used instead of the plasma dross residue.
The samples show progressively less sintering with increasing alumina content.
Example 4 The following tests were carried out to illustrate the durability (fracture toughness) of various products when used for sandblasting.
Sandblasting tests were carried out with (a) commercial sand (MarcoT~ 24), (b) products according to Canadian Patent 1,208,918 (JetmagT~ 30-60) and (c) products according to the present invention JetplusT~ 30-60.
~, . . ... .. . .............. . . . .. . .
- - ? `
. *"
, j ~ - . . .
The results are shown in Table 7 below.
PERFOR~LANCECOMPARISON OFTHE D~ERENTSAND BLASllNG MED~A
l M~ur~ ¦ SAND BLA~lrNG MEDLA
5properties Je~mag 3~60Marco 24Jetplus 30 . .
~epth ol 0.004~ 0.0036~0.0036 penetration, inch Sand consumpt~on, 2.31 _ l39 Lbst7lS ft2 1644 1873 Sandblasting spa:d,1.77 1.49 1.39 f~min.
Figure 4 is a graph showing the relative sandblasting speeds of the three materials.
Clearly these results show a significant advantage for the product o~ the present invention.
Example 5 Asbestos tailings (75 kg) were mixed with plasma dross residue (25 kg) from the Guillaume-Tremb}ay plant, Quebec, and ~
the mixture was heated at 1350-1500 C for 45 minutes in a ~ --pilot rotary kiln. The product thus obtained was analyzed for - -its AlN content, which was found to be below 0.5% by weight and thus essentially non-polluting when disposed of after use of the material as a sandblasting agent.
,} . - .
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Claims (20)
1. A process for producing a sintered material suitable for use in particular as a sandblasting agent, which comprises:
mixing particles of aluminum dross residue and particles of serpentine-containing material to form a solids mixture;
heating the solids mixture in an oxidizing atmosphere at a temperature in the range of 1250-1600°C for a period of time long enough to form a sintered product;
allowing the product to cool; and grinding the sintered product to a predetermined particle size range.
mixing particles of aluminum dross residue and particles of serpentine-containing material to form a solids mixture;
heating the solids mixture in an oxidizing atmosphere at a temperature in the range of 1250-1600°C for a period of time long enough to form a sintered product;
allowing the product to cool; and grinding the sintered product to a predetermined particle size range.
2. A process according to claim 1 wherein said material is a salt dross residue.
3. A process according to claim 1 wherein said alumina-containing material is a plasma dross residue.
4. A process according to claim 1 wherein said dross residue contains at least one heat-generating material selected from the group consisting of aluminum nitride and metallic aluminum, said heat-generating material reacting exothermically in said oxidizing atmosphere during said heating step.
5. A process according to claim 1 wherein said dross residue is a plasma dross residue having a composition as indicated below:
6. A process according to claim 1, wherein said dross residue is salt dross residue having been subjected to washing with water to remove most salt therein and having a composition as indicated below:
7. A process according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6 wherein the amount of said dross residue in said solids mixture is in the range of 5 to 50% by weight.
8. A process according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6 wherein said serpentine-containing material comprises asbestos tailings.
9. A process according to claim 8 wherein said asbestos tailings have the following composition: SiO2, 33-44%; MgO, 30-44%; FeO, 0-6%; Fe2O3, 0.1-5%; Al2O3, 0.2-1.5%; CaO, trace-5%; and H2O, 12-15% by weight.
10. A process according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6 wherein said sintered product is ground to a size smaller than 70 Tyler mesh.
11. A process according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6 wherein said heat treatment is carried out for a period of 30 to 90 minutes.
12. A process according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6 wherein the size of the particles of the dross residue is in the range of less than 1 inch to larger than 100 Tyler mesh.
13. A process according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6 wherein the size of the particles of the asbestos tailings is in the range of less than 3/4 inch to larger than 1/16 inch.
14. A process according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6 wherein the serpentine-containing material has a basicity index (1.beta.) of less than 1.
15. A process according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6 wherein the solids mixture is heated to a temperature in the range of 1300-1500°C.
16. A particulate sandblasting material comprising regions of magnesium spinel and alumina sintered with olivine.
17. A material according to claim 16 having a particle size of minus 16 to plus 70 Tyler mesh.
18. A material suitable in particular for sandblasting according to claim 16 or claim 17, when produced by a process according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6.
19. The use of a material according to claim 16 or claim 17 as a sandblasting agent.
20. The use of a material according to claim 16 or claim 17 as a foundry sand.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2084319 CA2084319A1 (en) | 1992-12-02 | 1992-12-02 | Process for producing calcined material useful as a sandblasting agent and the material thus produced |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2084319 CA2084319A1 (en) | 1992-12-02 | 1992-12-02 | Process for producing calcined material useful as a sandblasting agent and the material thus produced |
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| Publication Number | Publication Date |
|---|---|
| CA2084319A1 true CA2084319A1 (en) | 1994-06-03 |
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ID=4150779
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2084319 Abandoned CA2084319A1 (en) | 1992-12-02 | 1992-12-02 | Process for producing calcined material useful as a sandblasting agent and the material thus produced |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111440007A (en) * | 2020-03-16 | 2020-07-24 | 华南理工大学 | Method for preparing porous building thermal insulation material by using asbestos tailing silicon magnesium residues |
-
1992
- 1992-12-02 CA CA 2084319 patent/CA2084319A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111440007A (en) * | 2020-03-16 | 2020-07-24 | 华南理工大学 | Method for preparing porous building thermal insulation material by using asbestos tailing silicon magnesium residues |
| CN111440007B (en) * | 2020-03-16 | 2021-07-20 | 华南理工大学 | Method for preparing porous building thermal insulation material by using asbestos tailing silicon magnesium residues |
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