MORAES DA GAMA, Evandro (Rua Contria, n° 101 apto. 305,Bairro Barroca, -21, Belo Horizonte Minas Gerais, 30480, BR)
CLAIMS
1 - Process for preparing metakflex, metakflex and process for obtaining products that use metakflex characterized by comprising: a) calcining of clayey soils at a temperature in the range of 500 and 800 0 C; b) addition of quicklime;
2 - Process for preparing metakflex according to claim 1 , characterized by using clayey soils from mine decapping, refuse and clay overburden. 3 - Process for preparing metakflex according to claim 1 , characterized by comprising the group consisting of clayey soils, Apophyllite, Kaolinite, Serpentine, Garnierite, Pyrophyllite, Talc, Muscovite, Phlogopite, Biolite, Lepidolite, Margarite, Clorite, Sepiolite.
4 - Process for preparing metakflex according to claim 1 , cha- racterized by comprising the group consisting of overburden spoil, mine spoil from iron, manganese, limestone, granite, gneisse and slate mining or from any other type of rock having a clay cap with the presence of kaolinite and aggregate minerals.
5 - Process for preparing metakflex according to claim 1 , cha- racterized by the addition of quicklime between 1 and 10%.
6 - Process for preparing metakflex according to claim 1 , characterized by comprising the transformation of overburden deposits and refuse dams into a high strength binder.
7 - Process for preparing metakflex, characterized by a process for identifying clayey soils.
8 - Process for preparing metakflex according to claim 7, characterized in that the identification method comprises the following steps: a) sieving the soil; adding a mass M of 500 ml distilled water and methylene blue; obtaining the mixture concentration of 10%; stirring at 700 +- 100 tr/min during 5 minutes until total dissolution; adding 5 to 10 cm 3 according to the clay fraction of the soil followed by stirring; depositing a drop of the solution onto a filter paper; adding the soil and water solution to the me- thylene blue solution in amounts between 5 cm 3 and 15 cm 3 ; b) determining the mineralogy; d) determining the calcining temperature and the calcining of the qualified soil; d) adding up to 40% of quicklime and water to the calcined soil in a mixer;
9 - Metakflex, characterized by comprising a compound of: a) metakaolin; b) quicklime; 10 - Metakflex according to claim 9, characterized by constituting an intermediate compound to be added to products and processes.
11 - Metakflex according to claim 10, characterized by comprising products of the group consisting of. a) ore pellets; b) mortar for civil construction; c) concrete and precast materials; d) mineral slurries; e) dam filters in the form of mortar and landfill caps in the form of covering; f) a binder for mineral slurries and cold and hot ore pelletizing; g) a binder for charcoal and coal fines; h) a binder for powder residues resulting from iron metallurgy;
12 - Process for obtaining products that use metakflex, according to claim 11 , characterized by comprising the addition of metakflex at a ratio between 0.1 and 99% by weight.
13 - Process for obtaining products that use metakflex, according to claims 11 and 12, characterized by comprising the obtaining of concrete, replacing up to 70% of Portland cement with metakflex.
14 - Process for obtaining products that use metakflex, according to claims 11 and 12, characterized by comprising the obtaining of additives for mineral slurry and pelletizing, the addition of 3% and 15% by weight of metakflex. 15 - Process for obtaining products that use metakflex, according to claims 11 and 12, characterized by comprising the obtaining of charcoal pellets, the addition between 2 and 15% of metakflex at 98% or 85% of coal fines. |
Title: "PROCESS FOR PREPARING METAKFLEX, METAKFLEX AND PROCESS FOR OBTAINING PRODUCTS THAT USE METAKFLEX"
The present invention relates to a high strength binder produced from clayey soils calcined at low temperatures with the addition of lime. The present application further relates to a process for identifying clayey soils for the production of metakflex.
The process for obtaining a high strength binder product, as well as products and processes that use metakflex are also disclosed.
MetaKflex is a high strength binder produced from clayey soils calcined at low temperatures with the addition of lime.
This high strength binder is manufactured from clayey solids calcined at low temperatures, in the range of 500-800 0 C. Calcining is performed in a controlled and fast manner, using the calcining technology disclosed in patent application Pl 9809941-8. The calcined product is called metakaolin. Adding quicklime to metakaolin at the ratio of 0.1% to 10% with the addition of water at defined ratios creates a high strength binder. Metakflex may be used as:
- An additive for cements, concretes and mortars for the manufacture of precast products, mortars for civil construction. - Dam filters in the form of mortar, landfill caps in the form of covering.
- A binder for mineral slurry and hot and cold ore pelletizing.
- A binder for charcoal and coal fines.
- A binder for powder residues resulting from iron metallurgy. Prior art
Clayey soils resulting from the weathering of igneous rocks, such as granites, metamorphic rocks, such as gneiss and sedimentary rocks as limestone, arkose, pisolite, among others, contain a large proportion of clay. Clays are rocks and rocks, in turn, are formed by minerals. These minerals are divided into two classes: Silicates and Non-Silicates. The clay minerals are part of the Silicate group, in the subclass called Phyllosilicates. When referring to clay as a mineral, the most commonly used expression is clay
mineral.
Phyllosilicates are largely composed of products from rock weathering, almost always being part of the structural constitution thereof. Their properties are closely related to the release and retention of plant nutrients, to water storage in the soil between dry and wet periods and to the accessibility of the soil to atmospheric gases and organisms.
Examples of phyllosilicates:
Apophyllite KCa 4 (Si 4 OiO) 2 F • 8H 2 O
Kaolinite AI 4 (Si 4 O 10 )(OH) 8
Serpentine Mg 6 (Si 4 Oi 0 )(OH) 8
Garnierite (Ni, Mg) SiO 3 nH 2 O
Pyrophyllite AI 2 (Si 4 O 10 )(OH) 2
Talc Mg 3 (Si 4 O 10 )(OH) 2
Muscovite KAI 2 (AISi 3 O 10 )(OH) 2
Phlogopite KMg 3 (AISi 3 O 10 )(OH) 2
Biolite K(Mg Fe) 3 (AISi 3 O 10 )(OH) 2
Lepidolite K 2 Li 3 AI 3 (Mg Fe) 3 (AISi 3 O 10 )(O 1 OH F) 4
Margarite CaAI 2 (AI 2 Si 2 O 10 )(OH) 2
Clorite (Mg 1 Fe", Fe" 1 , Al) 3 (AI 1 Si) 4 O 10 (OH) 2 *
(Mg,Fe",Fe"',AI) 3 (OH) 6 Sepiolite Mg 6 (Si 3 O 13 )(OH) 2 *6H 2 O
Clayey soils having a clay fraction composition and a high content of kaolinite, when calcined in a controlled and fast manner, generate a binder product called metakaolin.
The meta prefix in the term is used to denote change. It is a borrowing from Greek meaning after, along with, beyond. The scientific use of the prefix is used for a combining form denoting the least hydrated of a series. In the case of metakaolin, the change that is taking place is dehydroxylization, brought on by the application of heat over a defined period of time.
At about 100-200 degrees C, clay minerals lose most of their adsorbed water. The temperature at which kaolinite loses water by dehydroxyli- zation is in the range of 500-800 0 C. This thermal activation of a mineral is also referred to as calcining. Beyond the temperature of dehydroxylization, kaolinite retains two-dimensional order in the crystal structure and the product is termed metakaolin. The key in producing metakaolin for use as a supplementary cementing material, or pozzolan is to achieve as near to complete dehydroxylization as possible without over heating. Successful processing results in a disordered, amorphous state, which is highly pozzolanic, called metakaolinite. Thermal exposure beyond a defined point will result in sintering and the formation of mullite, which is dead burnt and not reactive.
As already mentioned, in order to obtain metakaolin, kaolinite needs to go through a process called calcining, as described in document Pl 9809941 -8. The strong binding properties of metakaolinite are closely related to the formation of a large physicochemical absorption surface of metakaolinite. The mineralogical composition of clayey soils with the presence of minerals, such as kaolinite, goethite and muscovite, which go through a fast calcining process, increases the specific surface to values in the magnitude of 40 m 2 /g. This increase in the specific surface favors the kinetics of the reaction between metakaolinite and lime forming aluminum silicates. When small percentages of lime are added to metakaolinite or metakaolin, a binder herein named metakflex is created.
Metakflex, in turn, may be used as a binder for several products, enhancing their mechanical, chemical and physicochemical properties.
Metakflex has technical, economical, ecological and social advantages in relation to the artificial pozzolans. Metakflex does not need the addition or mixture of limestone, as is the case of artificial pozzolans. Metakflex is a binder in itself. With the addition of water, Metakflex becomes a slur- ry having low heat release, being a mixture of easy handling.
Metakflex may be produced from clayey soils considered to be overburden, which normally constitute the capping of mines of: limestone,
iron ore, manganese, granite, gneisses, slate, among others. In the case of pozzolans, clays are needed, rather than clayey soils.
This fact directly affects the storage of overburden materials t- hrough controlled overburden deposits. The controlled overburden deposits in iron, manganese, granite, gneiss and slate mining or any other type of rock mining having a clay cap with the presence of kaolinite and aggregate minerals are dead stocks of overburden. These stocks cause environmental impact. This stock may be transformed into metakflex. Therefore, what would be considered useless and an environmental liability will become a high qua- lity binder after calcining.
Washing and classification procedures, called CONCENTRATION in the mining industry, are used for iron ore, manganese, phosphate, among others, generating clay spoil. This spoil material is stocked in refuse dams. The refuse dams are sources of environmental concern and represent a high cost for the industries. The refuse processed through fast calcining are transformed into metakflex.
Metakflex has great advantages in relation to other binders. It may be manufactured from clayey soils that are normally placed in overburden deposits without any further application. It may be produced from refuse from mining iron, manganese and phosphates that are normally stocked in refuse dams. Therefore, it significantly contributes to improve the environment, generating a noble product from mining refuse in dams. The binding power is activated with percentages of lime of up to 10% and there is no need to add limestone, as is the case in another patent application (PI0204653- 9).
The production of metakflex is directly related to the reduction of CO 2 emissions to the atmosphere, because its production releases process water and does not reach temperatures above 800 0 C, therefore, being within the limits established in the KYOTO Treaty. The metakflex product is obtained by clean technology being an ecological product made from clayey soils, overburden and clay refuse. U- sing a fast and controlled calcining process, at temperatures in the range of
650 to 800°C with the addition of quicklime varying between 1 and 10%, depending on the desired resistance, metakflex will become a high mechanical strength binder with several industrial applications.
Products obtained using metakflex: Mortar for civil construction, with total replacement of cement with metakflex.
Concrete for civil construction. The concrete may receive up to
70% of metakflex in replacement of Portland cement. This addition will result in a decrease in the luminescence and exudation of lime, generating a more workable and durable concrete. This process may also be used for producing precast materials for civil construction.
The ore fines are normally agglomerated with Bentonite. Bento- nite is a rare and high cost mineral clay. Iron ore fines, 95% below 0.044 mm, for instance, are currently agglomerated with Bentonite at the ratio of 90% iron ore fines, 5% Bentonite and the other 5% divided between limestone and coal. With the use of metakflex, Bentonite and limestone may be removed.
The pellet may be cold agglomerated or calcined with metakflex. Metakflex will provide the pellet with mechanical strength compatible with that obtained by the addition of Bentonite. Similarly, the manganese fines may also be cold and hot agglomerated with metakflex.
The present invention may also be understood by the non- limiting examples listed below.
EXAMPLE 1 - Analysis process for identifying clayey soils capable of producing metakflex Checking the potential of a clayey soil for manufacturing metakflex involves an analysis process comprising the four steps described below.
1 st Step - The soil should be classified by means of sieving u- sing the sequence of 80 μm,5 mm and 50 mm sieves. Use an amount M, close to 3Og. Mass M is placed in a container with 500 ml of distilled water and methylene blue. The methylene blue solution shall be less than one month old, have a concentration of 10% and be stored free from light. The solution, soil, distilled water and methylene blue, should be stirred in a suita-
ble apparatus, at the speed of 700 +- 100 tr/min during 5 minute until total dissolution of the soil. Add 5 to 10 cm 3 according to the clay fraction of the soil and stir during 1 minute. Remove a drop of the solution with a glass rod and deposit it onto a filter paper, placed on a non-absorbent support. The spot formed on the filter paper shall be dark blue surrounded by a colorless wet zone. This drop shall also form a central deposit with a diameter between 8 and 12 mm. Add to the soil and water solution the methylene blue solution in amounts between 5 cm 3 and 15 cm 3 until the spot on the filter paper produced by the drop forms a light blue halo within the wet area of the spot. At this phase, stop adding methylene blue and collect a drop at every minute, repeating the test. If 5 drops with light blue color remain, the test is positive.
VBS absorption rate calculation. V is the absorbed volume of methylene blue and M is the mass of soil retained in the 50 mm sieve.
For the sample in the sieving assay in which Dmax is less than 5 mm:
VBS = V/M
For the sample in which Dmax is greater than 50 mm:
VBS = (V/M) x C
Wherein C is the ratio or percentage of the 0/5 mm fraction wi- thin the 0/50 mm fraction. If VBS is greater than 12, the second step may start.
2 nd Step - Determining the mineralogy of the clay fraction of the soil under study. The clay fraction determined by the VBS of the first step shall have at least 50 of clay, this clay being composed of at least 20% kaoli- nite, quartz between 10 and 45%, goethite between 2 and 10% and muscovi- te, 20% at most. Anatase and rutile at percentages of 2% at most. The soil with the clay fraction within these specifications will pass to the third step.
3 rd Step - Determining the calcining temperature and the calcining of the qualified soil. The granulometry of the soil must be below 40 μm. The 20Og sample will pass through the following calcining intervals: Elevating temperature in function of time, from O 0 C to 380 0 C during 1 hour. After 1 hour, leave 2 minutes at 380 0 C. Elevating temperature in function of time,
from O 0 C to 750 O 0 C during 2 hours. After 1 hour, leave 2 minutes at 750 0 C. Elevating temperature in function of time, from O 0 C to 800 0 C during 2 hours and from 800 0 C to 1000 0 C in 30 minutes. Leave 30 minutes at 1000 0 C.
At each level, calculate the dehydroxylization coefficient and re- peat the methylene blue test in the calcined soil. The selected temperature will be that in which the dehydroxylization coefficient is greater than 0.9 and in which VBS is greater than 0.3. In addition to these two parameters, the material shall form a golden halo at the methylene blue spot with the calcined soil. The temperature with the dehydroxylization coefficient greater than 0.90 and VBS greater than 0.30 and the golden halo as described will be the temperature indicated for calcining. This soil will then pass to the fourth step.
4 th Step - After the calcining temperature is selected, a sample of 1 kg of soil with granulometry below 40 μm will be calcined. This calcined soil will be placed at a lab mixer with a maximum amount of 40% quicklime and water at low speed during 30 seconds and, right after that, at high speed during 4 minutes.
EXAMPLE 2 - Use of metakflex in producing a mineral slurry
Determining the amount of water for manufacturing the slurry is made by means of the standard Vicat test in Brazil. The measurements shall be between 1 and 10 mm. The slurry formed will be carefully thickened and placed in a special mold formed by cylinders of 2 cm in diameter and 4 cm in height. After the slurry is in the mold, it is conserved in closed plastic bags during 7 days at a temperature of 20 0 C. After 7 days, the test specimens are removed from the mold and burst in a press with a controlled deformation speed of 1.27 mm/min in an uniaxial compression test. The calcined soil that is above 10 MPa may be used as raw material for manufacturing metakflex.
EXAMPLE 3 - Obtaining charcoal pellets
The charcoal used in iron metallurgy plants suffers degradation of 20% in volume when handled for stocking due to its fragility. This degrada- tion produces fines that are stocked in the form of small or large piles. These piles often are subject to spontaneous combustion causing accidents and deaths. The addition of between 5 and 10% metakflex at 90% or 95% coal
fines with controlled moisture at a pelletizing table forms coal pellets with a strength between 2 and 4 Kgf/cm 2 . This pellet may be stocked and after that it may be taken to a metallurgical furnace and burned producing as refuse charcoal ash and aluminous slag resulting from the small addition of metak- flex. Metakflex stores an excess of water due to its granulometry. This water transference from metakflex to the coal fines, after the virtual saturation of the charcoal fines, provides the coal pellet with a strength above 2 Kgf/cm 2 . EXAMPLE 4 - Obtaining an additive Additive for mineral slurries for increasing weather exposure and resistance. Mineral slurries are high viscosity emulsions having a concentration of up to 95% of solids. These slurries are formed by refuse from the treatment of ores such as iron, manganese, phosphate, gold, silver, among o- thers. These slurries are produced through conical concentrators. The mineral slurries may be stocked in dams. Contrary to the current refuse dams cal- led sludge dams, the mineral slurry dams reduce the stock area in up to 80%. However, the stock of mineral slurry in dams and the use of this slurry as filling in underground mines for improving safety and reducing environmental impact requires an increase in mechanical strength. This increase in mechanical strength is obtained by means of a friction angle and the cohesion of the mineral slurry. These mineral slurries when metakflex is added enhance the mechanical properties in up to 60%. This addition may vary from between 3% and 15% by weight of metakflex.