ZA200305964B - Silicate binders including calcium bearing curing agent. - Google Patents
Silicate binders including calcium bearing curing agent. Download PDFInfo
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- ZA200305964B ZA200305964B ZA200305964A ZA200305964A ZA200305964B ZA 200305964 B ZA200305964 B ZA 200305964B ZA 200305964 A ZA200305964 A ZA 200305964A ZA 200305964 A ZA200305964 A ZA 200305964A ZA 200305964 B ZA200305964 B ZA 200305964B
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- ZA
- South Africa
- Prior art keywords
- weight
- curing agent
- alkali metal
- silicate
- per cent
- Prior art date
Links
- 239000003795 chemical substances by application Substances 0.000 title claims description 41
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 title claims description 13
- 239000011230 binding agent Substances 0.000 title description 8
- 239000011575 calcium Substances 0.000 title description 6
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical group [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 title description 4
- 229910052791 calcium Inorganic materials 0.000 title description 4
- 238000000034 method Methods 0.000 claims description 50
- 239000002245 particle Substances 0.000 claims description 23
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 22
- 239000000203 mixture Substances 0.000 claims description 22
- 229910052910 alkali metal silicate Inorganic materials 0.000 claims description 18
- 239000011236 particulate material Substances 0.000 claims description 15
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 14
- 239000000292 calcium oxide Substances 0.000 claims description 12
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 11
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims description 11
- 239000004115 Sodium Silicate Substances 0.000 claims description 9
- 229910052911 sodium silicate Inorganic materials 0.000 claims description 9
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical group [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 9
- 239000007787 solid Substances 0.000 claims description 8
- 229910052783 alkali metal Inorganic materials 0.000 claims description 5
- 150000001340 alkali metals Chemical class 0.000 claims description 5
- 239000000428 dust Substances 0.000 claims description 5
- 239000011872 intimate mixture Substances 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 235000019738 Limestone Nutrition 0.000 claims description 4
- 238000001354 calcination Methods 0.000 claims description 4
- 239000006028 limestone Substances 0.000 claims description 4
- 239000003513 alkali Substances 0.000 claims description 3
- 239000006227 byproduct Substances 0.000 claims description 3
- 239000007864 aqueous solution Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 description 8
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 7
- 239000004568 cement Substances 0.000 description 6
- 239000000243 solution Substances 0.000 description 6
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 4
- 235000011941 Tilia x europaea Nutrition 0.000 description 4
- 239000004571 lime Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000011369 resultant mixture Substances 0.000 description 3
- 150000004760 silicates Chemical class 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229910000604 Ferrochrome Inorganic materials 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 238000003723 Smelting Methods 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 239000005864 Sulphur Substances 0.000 description 2
- 239000004411 aluminium Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000000440 bentonite Substances 0.000 description 2
- 229910000278 bentonite Inorganic materials 0.000 description 2
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 2
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 2
- 239000012717 electrostatic precipitator Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000005065 mining Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 102000020897 Formins Human genes 0.000 description 1
- 108091022623 Formins Proteins 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000011449 brick Substances 0.000 description 1
- 239000001175 calcium sulphate Substances 0.000 description 1
- 235000011132 calcium sulphate Nutrition 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- UHZZMRAGKVHANO-UHFFFAOYSA-M chlormequat chloride Chemical compound [Cl-].C[N+](C)(C)CCCl UHZZMRAGKVHANO-UHFFFAOYSA-M 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 235000013379 molasses Nutrition 0.000 description 1
- 238000005453 pelletization Methods 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 235000019353 potassium silicate Nutrition 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 235000019351 sodium silicates Nutrition 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 229910021653 sulphate ion Inorganic materials 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B34/00—Obtaining refractory metals
- C22B34/30—Obtaining chromium, molybdenum or tungsten
- C22B34/32—Obtaining chromium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/14—Agglomerating; Briquetting; Binding; Granulating
- C22B1/24—Binding; Briquetting ; Granulating
- C22B1/242—Binding; Briquetting ; Granulating with binders
- C22B1/243—Binding; Briquetting ; Granulating with binders inorganic
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Metallurgy (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Environmental & Geological Engineering (AREA)
- Geology (AREA)
- Geochemistry & Mineralogy (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Inorganic Chemistry (AREA)
- Silicates, Zeolites, And Molecular Sieves (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Description
© WO 02/064846 PCT/GB02/00430
SILICATE BINDERS INCLUDING CALCIUM BEARING CURING AGENT t This invention relates to the use of alkali meta! silicates for binding or agglomerating particulate material and, in particular, to the use of alkali metal silicates in ‘ 5 combination with a curing agent to bind particulate material.
The need to agglomerate particulate materials to assist in the processing or handling of such materials exists in many industries and one such industry is the mining and extractive industry.
During the mining and processing of ores large amounts of fine material are generated. In the reduction of chrome based ores to produce ferrochrome the smeiting furnaces currently in operation cannot handle large concentrations of fine material so there is a need to agglomerate this material. Agglomeration processes currently in use include processes which produce pellets, briquettes and blocks with a variety of shapes using a variety of binder systems such as sodium silicate, bentonite, cement or lime 16 combined with molasses.
Commercial methods for agglomerating chrome ore fines utilising bentonite as a binder include the Outokumpu process (South African patent 78/4945) and Showa Denko process (US Patent 3 993 471 and South African Patent 83/7277) and a commercial method using sodium silicate as a binder in a pelletisation process is disclosed in a patent by J.J. Marsh (South African Patent 95/10532). The capital investment required for these pracess routes is very large and high temperatures are required for the curing processes.
An alternative to the above process routes is a block making process which requires much less capital investment, the blocks being cured at temperatures between . 20° C and 50° C as compared to 1400° C for both the Outokumpu and Showa Denko processes and 300° C to 400° C for the agglomerating process that utilises sodium silicate. Thus the block making process is much less expensive to operate.
The block making process comprises mixing the mineral fines with a binder, forming the mixture produced into a block, compacting under pressure and/or consolidating by vibrating in a mould, demoutding and then allowing the blocks to harden at ambient temperature so that the blocks are hard and do not break easily after 24 hours.
The most commonly used binder for the blocking of chrome ore fines is cement because it allows the blocks to be shaped before they set. The use of cement is, ’ however, undesirable because the amount of cement used leads tc a decrease in the productivity of a smelting furnace and impurities introduced with the cement (such as . 35 sulphur and phosphorus) can affect the quaiity of metal eventuaily produced from the ore.
Sodium silicate has been evaluated as an alternative binder in place of cement in the blocking of chrome fines. The result has been unsatisfactory due to the poor green strength of the blocks produced and the extended time period required for the curing of the blocks at temperatures between 20° C to 50° C.
A method wherein a silicate can be employed in an efficient agglomerating process at ambient temperatures or just above has now been devised. The process can . provide a delayed setting time, enabling bodies to be readily shaped and the bodies produced have a good green strength.
According to the invention a method of binding the particles of a particulate material comprises preparing a composition comprising the particulate material, an alkali metal silicate and a curing agent, forming said composition into a shaped body and allowing said mixture to cure so as to form a rigid shaped body, wherein said curing agent is a composition comprising an intimate mixture of calcium carbonate and calcium oxide in which the calcium oxide comprises from 10 to 90 per cent by weight of the intimate mixture.
The calcium oxide and calcium carbonate are present as an intimate mixture and the curing agent is believed to be more effective in controlling the reaction rate of the alkali metal silicate if the curing agent comprises particles which contain both calcium oxide and calcium carbonate rather than consisting of a mixture of particles of calcium oxide and particles of calcium carbonate.
One particularly useful form of curing agent which can be employed in this invention is the by-product dust formed during calcination of limestone. During the calcination process a proportion of the lime becomes entrained in the exhaust gases and must be removed therefrom, typically by means of bag fiiiers, wet scrubbers, electrostatic precipitators or gravel bed filters. The composition of this dust depends upon the conditions under which it was produced and the composition of the limestone used in the kiln. The major component is usually calcium oxide (lime) but, in view of exposure of the dust to carbon dioxide in the exhaust gases, a further significant component is calcium carbonate. Generally, sulphate, usually in the form of calcium sulphate is present and the major non-calcareous contaminants are compounds of silicon and aluminium, probably derived from clay which is present in the limestone.
Preferably, the curing agent contains from 20 to 80 per cent by weight calcium oxide and, more preferably, from 30 to 70 per cent by weight calcium oxide.
Preferably, the curing agent contains at least 5 per cent by weight calcium carbonate and more preferabiy at ieast 15 per cent calcium carbonate. Generally, not more than 40 per cent by weight calcium carbonate is present. ,
The curing agent is preferably a finely divided solid and preferably it has a weight mean particle size below 100 pm, as determined by Malvern Mastersizer, using the . method detailed hereinafter. More preferably, the curing agent has a weight mean particle size below 50 um and a weight mean particle size below 25 ym is even more preferable.
Usually, the curing agent will have a weight mean particle size above 5 pm.
d WO 02/064846 PCT/GB02/00430 in general, any alkali metal silicate can be used in the process of the invention ' but sodium or potassium silicates are preferred and, generally. sodium silicate is more : economical to use. Alkali metal silicates are available with a range of silicate to alkali , metal ratios and, in general, silicates having any ratio are suitable for use in the invention.
However, a silicate having a molar ratio of SiO, to M,0, where M is an alkali metal, above 1.6 is preferred since such silicates are generally cheaper and are less corrosive than those having a lower SiO; to M,O molar ratio. Preferably, the molar ratio, SiO, to M0 is in the range 1.6 to 3.3. More preferably, the ratio is in the range 1.6 to 2.6 and, even more preferably, is in the range 1.8 to 2.3.
The alkali metal silicate can be employed in any suitable form. Aqueous solutions having a range of concentrations and a range of SiO; : M,O ratios are readily available commercially and these are convenient for use in this invention. Generally, these solutions will have a solids content in the range 35 to 55 per cent by weight, expressed as weight of SiO, plus MO. More preferably, the solids content is in the range 40 to 50 per cent by weight, expressed as SiO; plus M20.
A wide range of proportions of alkali metal silicate to curing agent can be used.
Generally, the ratio of silicate to curing agent is in the range 1:1to 10 : 1 by weight and, preferably, the ratio of silicate to curing agent is in the range 1.5: 1 to 7 : 1, the silicate being expressed as weight of SiO, plus M,0O present.
There is no restriction on the nature of the particulate material which can be agglomerated using the silicate and curing agent. Typical particulate materials include powdered coal, crushed ores, particulate waste products, ferrochrome, silicon carbide, tailings from precious metal extraction and waste from the steel industry. One particularly useful embodiment of the method of the invention is the formation of agglomerated masses of ore particles which, in the non-agglomerated form, are too small to process effectively. The method of the invention has been found to be particularly useful in the recovery of small particles of chrome-bearing ores, particularly chromite ores, which would normally severely affect the efficiency and safe operation of the smelting furnace during processing, because of their size. In the method of this invention, when applied to such small particles, the particles which are agglomerated using alkali metal silicate and curing agent usually have a very wide range of particle size. The method is suitable for 1 agglomerating material containing particles ranging in size from about 0.5 um to about 30 mm. . it is preferable for the particulate materia: to have a iow water content and preferred particulate material contains less than 5 per cent water by weight.
The rigid shaped bodies which are formed using the method of the invention may take any suitable form. The method can, for example, be used to produce granules or pellets in a granulator or pelletiser or to produce moulded or extruded bodies of any desired shape. .
In a particular embodiment of the method of the invention the rigid bodies are blocks or bricks and these blocks are particularly preferred in the recovery of small particles of chrome ores.
In this particular embodiment, a pre-mix of the dry, particulate ore and the curing agent is first prepared. To this is added the alkali metal silicate solution. The components are usually mixed in proportions which provide from 1.0 to 4.5 parts, preferably from 1.5 to 3.5 parts, by weight of an alkali metal silicate expressed as weight of SiO, plus M,O present and from 0.25 to 2.0 parts, preferably from 0.5 to 1.5 parts by weight of the curing agent with respect to 100 parts by weight of the particulate ore, expressed as dry weight.
After the components have been thoroughly mixed, the resultant mixture is transferred to a mould, compacted, demoulded and allowed to cure to form the rigid body. Usually, the mixture will cure at ambient temperature, but slight heating can accelerate the process.
The mixture is usually cured at a temperature in the range 15 to 65° C. Generally, the blocks will be sufficiently hard to use after a curing period in the range 20 to 24 hours.
The cured blocks preferably have an unconfined compressive strength of at least 1 MPa.
Usually, the blocks have an unconfined compressive strength up to 3 MPa. These blocks can be used to satisfactorily process chrome ores which would normally be too finely divided to process satisfactoriiy.
Test procedures
Weight Mean Particle Size
The weight mean particle size of materials used in this invention 1s determinea using a Malvern Mastersizer model S, with a lens range up to 300 mm RF and MS1 sample presentation unit. This instrument, made by Malvern Instruments, Malvern,
Worcestershire, uses the principle of Mie scattering, utilising a low power He/Ne laser.
Before measurement the sample is dispersed in isopropanol for 1 minute using a 3000 rpm stirrer to form a suspension. This suspension is stirred before and whilst it is subjecied to the measurement procedure outlined in the instruction manual for the instrument, utilising the 300 mm RF lens range in the detector system. The Maivern .
Mastersizer measures the particle size distribution of the inorganic material based on the volume of the particles. The weight mean particle size (dso) or 50 percentile is readily obtained from the data generated by the instrument.
© WO 02/064846 PCT/GB02/00430
Green Strength
This test is performed on moulded blocks which have been allowed to cure for 30 minutes after gemouiding. A block is weighed and placed on a sieve shaker which is , operated for 30 seconds at 50 cycles per second. The material is then separated into 5 pieces larger than 15 mm across and fines (less than 15 mm across). The proportion of fines. is determined by weighing.
The method of the invention provides an economical means of binding together particulate material to form agglomerates which are non-dusty and can be easily handled. -
The rate of cure of the agglomerates is such that the initial mixture can be prepared and formed into an appropriate shape before setting, but the body has an adequate green strength to allow demoulding after a short period and a sufficiently strong rigid body is produced in a reasonable time.
The invention is illustrated by the following non-limiting examples.
Example 1 in order to assess the performance of various silicate/curing agent combinations these systems were tested in the absence of particulate material, since it is easier to observe the curing in such model systems.
The curing agent used in this example was a by-product from a lime calcination process. It was recovered from the electrostatic precipitators used to remove dust from the exhaust gases on a South African lime calciner. The principal components of this material were as follows (weight percentages); the calcium content is a measure of the
CaO, Ca(OH), and CaCO; present : calcium (as Ca®) 66.5% silicon (as SiO) 13.0% aluminium (as Al,03) 7.4% iron (as Fe,03) 1.9% magnesium (as MgO) 1.8% sulphur (as SO3) 0.5% ’ titanium (as TiO) 0.4% manganese (as MnO) 0.3% . The ‘oss or ignition {125C° C to constant weight) was 7.4% by weight.
This sample was estimated to contain 22.2 % CaCO; by weight. 45 g of sodium silicate solution having an SiO, to Na,O molar ratio of 2.6 and a solids content of 43.6% by weight (SiO; plus M;0) was placed in a 500 cm’ beaker. In a 200 cr beaker a slurry was prepared fom a measured amount of curing agent and 24 g of water. This slurry was added to the silicate with gentle stirring (about 200 rpm). The stirring was continued until the mixture became very thick, after which the mixture was tested with a spatula for gelling. The gel point was taken to be the point at which the mixture ceased to flow and maintained a semi-solid structure. Results are given in
Table 1 below.
Table 1 —_—n—
Wt. of curing agent (g) Time to gel point (min)
EE RE
EE
EE
15 4
Example 2
Small scale agglomerated blocks were prepared as follows, using fine particulate chromite ore as used in current block-making processes employed in South Africa. This ore contained 3% moisture by weight. A dry mixture of 100 parts chromite ore and 1.5 parts of the curing agent used in Example 1 was prepared by blending in a beaker with a spatula. 5 parts by weight of sodium silicate solution, molar ratio of SiO; to Na,0, 2.1, solids content, 48.2 per cent by weight, was added to this mixture and quickly stirred in with a spatula. This resultant mixture was transferred to a cylindrical mould 32 mm diameter which was standing on a base plate. The mixture was consolidated within the mould using an appropriately sized ram and a light mallet. The moulded cylindrical block (32 mm diameter x approximately 35 mm high) was then removed from the mould and allowed to cure overnight at room temperature.
The unconfined compressive strength (UCS) was measured using a Zwick
Universal Testing Machine Type No. Z030, 24 hours after the block was prepared. Two blocks were tested and found to have a mean UCS of 1.33 MPa with a standard deviation of 0.32 MPa. 25 .
Example 3
Cylindrical blocks were prepared in a similar manner to that described in
Example 2, except that the chromite ore was dried in an oven at 105° C until it contained an undetectable amount of water and the blocks were cured with 5 weight parts of 2.5 molar ratio silicate solution having a solids content of 46.7 per cent by weight and
0.5 weight parts of the same curing agent as used in Examples 1 and 2 per 100 weight parts chromite ore.
The mean UCS after 24 nours was 4.36 MPa with a standard deviation of 0.64 MPa on 4 samples.
Example 4
Fine chromite ore, as used in Example 2, was mixed with the curing agent used in Example 1 in the ratio 100 parts ore to 0.75 parts curing agent by weight. 3.5 parts by weight sodium silicate solution, having a molar ratio of 2.5 : 1, SiO to Na,O, was added to the ore/curing agent mix with stirring and the resultant mixture formed into blocks as described in Example 2 above. After demoulding and standing at room temperature for mins, the Green Strength was measured using the test described hereinbefore. The percentage of fines after testing was 28 per cent for blocks made according to this example and 70 per cent for blocks made without any curing agent. \
Claims (14)
1. A method of binding the particles of a particulate material comprising preparing a composition comprising the particulate material, an alkali metal silicate and a curing L} agent, forming said composition into a shaped body and allowing said mixture to cure so as to form a rigid shaped body, wherein said curing agent is a composition comprising an intimate mixture of calcium carbonate and calcium oxide in which the calcium oxide comprises from 10 to 90 per cent by weight of the intimate mixture.
2. A method according to claim 1 characterised in that the curing agent comprises particles which contain both calcium oxide and calcium carbonate.
3. A method according to claim 1 or 2 characterised in that the curing agent comprises by-product dust formed in the calcination of limestone.
4. A method according to any one of the preceding claims characterised in that the curing agent comprises from 30 to 70 per cent by weight calcium oxide.
5. A method according to any one of the preceding claims characterised in that the curing agent comprises at least 5 per cent by weight calcium carbonate.
6. A method according to any one of the preceding claims characterised in that the curing agent has a weight mean particle size below 100 pm.
7. A method according to any one of the preceding claims characterised in that the alkali metal silicate is sodium silicate.
8. A method according to any one of the preceding claims characterised in that alkali metal silicate has a molar ratio of silicate to alkali metal, expressed as SiO, : M0, where M is an alkali metal, in the range 1.6 to 3.3.
gS. A method according to any one of the preceding claims characterised in that the , silicate is in the form of an aqueous solution having a solids content in the range 35 to 55 per cent by weight, expressed as percentage SiO, pius MO where M is an alkali metal. ’
10. A method according to any one of the preceding claims characterised in that the alkali metal silicate and curing agent are present in a ratio between 1 : 1 and 10 : 1 by
© WO 02/064846 PCT/GB02/00430 weight, alkali metal silicate to curing agent, the alkali metal silicate being expressed as weight of SiO, plus M,O present, where M is an alkali meta:
11. A method according to any one of the preceding claims characterised in that the particulate material contains less than 5 per cent water by weight.
12. A method according to any one of the preceding claims characterised in that the amount of alkali metal silicate mixed with the particulate material is such that the shaped body comprises from 1.0 to 4.5 per cent by weight alkali metal silicate expressed as weight of SiO, plus M,0 present, where M is an alkali metal.
. 13. A method according to any one of the preceding claims characterised in that the amount of curing agent mixed with the particulate material is such that the shaped body comprises from 0.25 to 2.0 per cent by weight curing agent.
14. A method according to any one of the preceding claims characterised in that the shaped body is a block having an unconfined compressive strength in the range 1 MPa to 3 MPa.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0103278A GB0103278D0 (en) | 2001-02-12 | 2001-02-12 | Silicate binders |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| ZA200305964B true ZA200305964B (en) | 2004-07-08 |
Family
ID=9908459
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| ZA200305964A ZA200305964B (en) | 2001-02-12 | 2003-08-01 | Silicate binders including calcium bearing curing agent. |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP1360339A1 (en) |
| GB (1) | GB0103278D0 (en) |
| WO (1) | WO2002064846A1 (en) |
| ZA (1) | ZA200305964B (en) |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2205043A (en) * | 1937-11-17 | 1940-06-18 | George S Mican | Iron oxide briquette |
| JPS53104514A (en) * | 1977-02-25 | 1978-09-11 | Akira Konishi | Method of reusing dust produced in producing ferrosilicon |
| GB1600711A (en) * | 1977-06-22 | 1981-10-21 | Midrex Corp | Briquet and method of making same |
| GB2028787B (en) * | 1978-08-19 | 1982-09-22 | Foseco Int | Blast furnace operation |
| RU2083681C1 (en) * | 1994-07-12 | 1997-07-10 | Волгоградский государственный технический университет | Briquette for production of pig iron and steel |
| DE19708376C1 (en) * | 1997-03-01 | 1998-07-02 | Gasteier & Bilke Verfahrenstec | Use of a briquette made from waste materials as an additive for smelting furnaces in an iron foundry |
-
2001
- 2001-02-12 GB GB0103278A patent/GB0103278D0/en not_active Ceased
-
2002
- 2002-01-31 EP EP02710140A patent/EP1360339A1/en not_active Withdrawn
- 2002-01-31 WO PCT/GB2002/000430 patent/WO2002064846A1/en not_active Application Discontinuation
-
2003
- 2003-08-01 ZA ZA200305964A patent/ZA200305964B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| GB0103278D0 (en) | 2001-03-28 |
| EP1360339A1 (en) | 2003-11-12 |
| WO2002064846A1 (en) | 2002-08-22 |
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