Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR DRY RECYCLING AND PROCESSING OF STEEL SLAG
Field of the Invention
The present invention belongs to the field of recycling and more specifically
to dry processing and recycling of steel slag, removing the metal fraction of
the
slag in such an innovative process and through the metal-free material.
Through the process of the present invention, one can produce granules of
ore shot and steel shot, sealing blocks, apparent blocks, building blocks,
interlocking floors in all models, caissons, guides, masonry mortar, adhesive
mortar, floor on floor mortar, pumpable mortars, grouts, colored grouts,
flexible
grouts, epoxy grouts, epoxy mass for production of floors, grouts of several
strengths replacing natural lower aggregates such as sand, crushed stone by
steel
slag in their particle sizes with the addition of cement at 0.1% to 40%. The
product
obtained by the process of the present invention is particularly used in
replacement
of 100% of the conventional cement produced by a cement produced from steel
slag, applying additives from 0.1% to 30% additives, depending on the
application
of each product.
Background of the Invention
All literary processes described to date for the process to control expansion
of steel slag are to develop a route from the wet process, ie, via a
discontinuous
process and which demands high availability of time and space to hydration by
water of steel slag, which makes it unfeasible, ecologically and financially.
Summary of the Invention
The present invention aims to provide a process for recycling and
transforming steel slag by a dry route, generating basic raw materials for
obtaining,
for example the following products:
1. Interlocking floors of low, medium and high mechanical strength applicable
to
conditions of light, medium and heavy traffic in order to provide mechanical
strength that meets current standards.
2. Apparent and structural sealing blocks, normal finishing and fine finishing
for
internal and external environments.
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3. Mortars of type AC I, AC II, AC III, adhesive mortar, "floor on floor"
mortar,
pumpable mortars and designed mortars.
4. Flexible grout, colored grouts and epoxy grouts.
5. Epoxy mass for the production of floors
6. Grout for structures, anchoring of equipment, recovery and all possible
applications for this product.
7. Feedstock rich in CaO and MgO for the manufacture of cement, using steel
slag,
is this composition of cement mortars and grouts, tiles, blocks and grouts.
8. Metallic iron the following particle sizes:
a. greater than 2 mm for the manufacture of steel blocks to return in the
production process of steel fabrication in steel industry.
b. Less than 2 mm for the manufacture of steel shot.
Moreover, the process aims to obtain results as:
1. The removal of metal, for inhibiting expandability.
2. Obtaining raw materials of higher strength of steel slag and with different
particle sizes for fine aggregate, and
3. Obtaining raw materials of lower strength but high in calcium and
magnesium oxide, to obtain fines for cement replacement.
In case of removal of metal, the steel slag, mainly composed by adding
silica (SiO2), limestone and other components of a lower percentage, is
intended to
perform the final purification of the steel, which can reach temperatures of
1350
and 1400 C, so that the components undergo sintering process and is
incorporated
into metallic iron steel slag.
In addition, metallic iron may be incorporated in different particle sizes and
in different oxidation states, ranging from metal iron (Fe ) to iron monoxide
(FeO)
and iron oxide (Fe2O3). The presence of iron in different oxidation states,
mainly
iron monoxide (FeO-Fe+2), will give an extremely magnetic character to the
slag,
which will compete with the magnetism of metallic iron. Thus, it is used an
innovative process of separation of metallic iron (as shown in the flow chart
of the
drawings).
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Brief Description of Figure
Figure 1 is a process flow diagram for recycling and processing of steel slag
according to the present invention.
Detailed Description
Within the context of Figure 1, it will be observed that the process of the
present invention basically comprises the following steps:
(A) comminution and breakdown by impacting mills, at a dry route;
(B) particle size classification in different sizes by screening, respecting
the
range of 0.074 mm to 12.50 mm, for use in the final products;
(C) magnetic separation in magnetic separators developed exclusively for
the separation of metallic iron in the different particle size fractions;
(D) release of the slag associated with metallic iron through a stage of
impact at impacting mills;
(E) drying the material through the rotary dryer, determining the route of
control and treatment process of expandability of steel slag, by a dry route.
(F) new classification by screening, and
(G) new magnetic separation for final purification of the metal.
Raw materials of higher strength
Regarding the extraction of raw materials for added strength, the process
according to the present invention has 100% economic sustainability, in which
the
main goal is to get all the basic raw materials for manufacture of floors,
blocks,
mortars, grouts and especially replacement of cement, from steel slag, after
removal of the metal components.
Once done the process of disintegration, release and clearance of grains of
the slag, non-magnetic fraction is used to render the grains for different
applications, so you may need to meet the following additional steps depending
on
each intended application:
(1) define the optimal particle size for production of concrete blocks;
(2) define the grading curve for optimal packing of the grains to achieve
maximum strength and lower cement consumption;
(3) define the particle size for the formulation of the mortar;
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(4) define the particle size of the formulation of grout.
It is important to remember that at the process of separation of metallic
components involving several stages of crushing, screening, magnetic
separation
at different particle size stages and final release of the slag, are
automatically
generated the basic raw materials for manufacture of floors, blocks, mortar
and
grouts.
Raw Materials of lower strength
In relation to obtaining raw materials of lower strength, the item of greater
economic sustainability of the project is to obtain compounds rich in CaO and
MgO, which can produce raw material for cement replacement, considering that
this component is the item major cost in the production of products to be
developed.
In this same concept of recovering processing of metallic iron there is
generated a component rich in CaO and MgO for the production of cement
replacement, whereby it may be necessary to fulfill the following process
steps:
(1) identification and separation of compounds rich in CaO and MgO, and
(2) setting the particle size to produce cement substitute.
Laboratory Tests
Laboratory tests were performed, and the obtained parameters to adjust the
recovery process of metallic material and obtaining of raw matter. In the
tests
performed, the following steps occur:
1. Processing 4,000 kg of steel slag;
2. Comminution, breakdown, separation by different ranges of particle size;
3. Magnetic separation in different particle size ranges;
4. Breakdown, release and final cleaning of metal;
5. Obtaining the raw materials, all non-magnetic fractions;
6. Identification and chemical analysis of all non-magnetic compounds;
7. Separation of slag with high and low strength;
8. Size classification of slag with higher strength, separation by range of
particle size;
9. Separation of the slag of lower strength and grinding below 325 mesh;
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10. Composition of particle size, with the slag of higher strength, for the
manufacture of the products described above;
11. Definition of trace (relative of steel slag cement x water x additive) for
interlocking floors of steel slag;
Apparent blocks, for closure and structural
12. Composition of the particle size for the manufacture of steel slag blocks;
13. Definition of trace (relative to steel slag cement x water x additive) for
blocks of steel slag;
14. Production of steel slag blocks;
15. Test of mechanical strength (to compression), water and moisture
absorption;
Concrete blocks
16. Composition of the particle size for the manufacture of steel slag blocks;
17. Definition of trace (relative to steel slag cement x water x additive) for
blocks of steel slag;
18. Production of steel slag blocks;
19. Test of mechanical strength (to compression), water and moisture
absorption;
Floors of high strength
20. Composition of the particle size for the manufacture of high strength
floors;
21. Definition of trace (relative to steel slag cement x water x additive) for
floors with high mechanical strength;
22. Test of mechanical strength (to compression), water and moisture
absorption;
Mortar
23. Composition of the particle size for manufacturing mortar;
24. Definition of trace (relative to steel slag cement x water x additive) for
mortar;
25. Test of strength and pullout index;
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Grouting Mass
26. Composition of the particle size for manufacturing of grouting mass;
27. Definition of trace (relative to steel slag cement x water x additive) for
grouting;
28. Mechanical strength and weathering test (weather degradation);
Production of Replacement for Cement
Once identified the raw material of lower mechanical strength rich in CaO
and MgO, the raw material was comminuted to -325 mesh, then the additive of
cement replacement by inserting special additives (slag activators), and
implementation of test for different traces for different applications.
In more detail, it may be noted that the invention provides a process with a
dry route for the control of expansion factors (CaO, MgO and metallic iron),
contained in the steel slag.
During processing, it was found that the slag, when heated in a controlled
manner (residence time of 30 seconds at +1300 C), actives binding properties
of
the slag, as well as facilitates removal of friable material (free CaO and
MgO),
elements which, under normal conditions, react with water to form expandable
hydroxides (Ca0H2 and Mg0H2).
The main steps involved in the process and treatment of steel slag are
feeding scum, primary crushing, drying, secondary crushing, metal separation,
particle size classification, dust collectors and storage of aggregates.
These steps can be described in greater detail as follows:
Feeding of slag: occurs by means of a vibratory feeder in which the slag in
the primary crusher is measured;
Primary crushing: through the mill, the size of gross slag is reduced;
Drying: crushed slag is exposed at a controlled manner to determined
temperature and time;
Secondary crushing: the friable material is separated into mill, whose
principle of operation is the impact.
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Magnetic Separation: after the grinding, fractionated slag is found with
reduced content of calcium oxide (CaO) and magnesium oxide (MgO), so that all
material is led to Magnetic Separation system.
Magnetic separation according to the invention takes place by means of
randomly designed magnets with different intensities (Gauss) to capture
particulate
matter of different particle sizes.
After clearing the Metallic iron and part of the oxides (which cause
expansion), the material is transported to the screening system.
Size classification: After the classification in vibrating screen, there is
obtained a controlled steel aggregate with permitted levels of CaO, MgO and
iron
oxides, which do not react when mixed with water and cement, eliminating the
expansion.
Dust collectors: it is further provided a step of sleeve filtering that
collects
fine friable materials, arising from the dryer, the mill and the size
classification
system.
Storage of aggregates: The steel crushed stone classified as superfine,
fine, medium and coarse size is stored in a covered location and is ready to
be
used in the production of artifacts.
The steel aggregate, after being treated by the process of the present
invention replaces, with huge environmental gains, natural fine aggregates
commonly used in the production of artifacts, such as crushed stone and sand.
The steel crushed stone can be used in the production of concrete artifacts
such as interlocking floors, sealing blocks, building blocks, caissons,
guides, curb,
concrete, as well as adhesive mortars, floor on floor mortar, pumpable mortar,
grout, colored grouts, flexible grouts, epoxy grouts, epoxy masses.
In turn, the fines produced during processing of slag have a cement
function, and can be used in addition to the conventional cement, or in some
cases
by additives, or used to replace 100% of the conventional cement, by a cement
produced by steel slag, applying additives from 0.1% to 30% of additives
depending on the application and degree of strength of each product.
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With a demonstrative purpose, analytical results are shown below, which
demonstrate the control of expandability of the slag processed according to
the
present invention.
TAG TYPE OF STANDARD RESULT STANDARD RESULT
ANALYSIS
14185 Expansibility DNIT ME 113/09 0.38% Up to 3%
14182 Durability ASTM C88-05 2.0%
<12% (coarse aggregate)
ASTM C33/C33M 11
<10% (small aggregate)
14182 Los Angeles ABNT NBR 7211:09 16% <23%
Abrasion
141096 Compressive NBR 9780/87 and Average > 35 MPa
Strength NBR 9781/87 38.1%
141097 Compressive NBR 9780/87 and Average > 35 MPa
Strength NBR 9781/87 45.9%
It is therefore a process of recycling and transforming of steel slag by a dry
route of great importance to the objective pursued, fully meeting the proposed
objectives and fulfilling at a practical and efficient manner the intended
functions,
providing advantages inherent to its applicability, with specific and
innovative
characteristics and provided with fundamental requirements of novelty and
inventive activity, required to obtain patent protection.
