Title of Invention

PROCESS FOR PRODUCING IRON ORE AGGLOMERATES WITH USE OF SODIUM SILICATE CONTAINING BINDER

Abstract The present invention relates to a process for producing iron ore agglomerates comprising agglomerating fine iron ore particles in the presence of a binder system wherein the binder system comprises a binder and an alkali metal silicate and wherein the alkali metal silicate is present in an amount of between 0.0001 to 0.08 percent by weight, based on the total weight of dry iron ore agglomerate, wherein the binder system is free of synthetic polymer, and preferably comprises carboxymethyl cellulose as binder.
Full Text The invention relates to a process for producing iron ore agglomerates.
Such a process is known from US 6,293, 994, which discloses a process of making fired
mineral pellets by mixing particulate mineral material with moisture and binder
comprising substantially water-soluble organic polymer and alkali metal silicate in a dry
weight amount which is either (a) above 0.13% based on moist mix or (b) above 0.08%
based on moist mix and at least three times the dry weight of substantially water-soluble
organic polymer. The preferred polymer is a synthetic polymer formed of water-soluble
ethylenically unsaturated monomer or monomer blend. The high amount of alkali metal
silicate in the pellets described in US 6,293, 994 generally is undesirable, because
silicates can slow down the reduction process in steel making operations by blocking the
pathways the reducing gases use to permeate the pellet, which leads to an increase in
energy costs.
Furthermore, the use of such high amounts of alkali metal silicate results in green pellets
that have a high tendency to deform, which in turn may lead to pellets of different size
and shape, resulting in an inefficient process for preparing fired pellets.
The object of the present invention is to provide iron ore agglomerates with improved
physical properties.
The present invention provides a process for producing iron ore agglomerates comprising
agglomerating fine iron ore particles in the presence of a binder system wherein the
binder system comprises a binder and an alkali metal silicate and wherein the alkali metal
silicate is present in an amount of between 0. 0001 to 0.08 percent by weight,
based on the total weight of dry iron ore agglomerate, wherein the binder
system is free of synthetic polymer. The process of the invention leads

to iron ore agglomerates with increased cold compression strength, preheat
strength, and dry crush strength relative to the use of conventional binder systems
comprising the same binder. Furthermore, small amounts of the alkali metal silicate
are already sufficient to obtain a significant improvement in the physical properties
of the agglomerates. Moreover, the specified amount of alkali metal silicate causes
the agglomerates obtained with the process of the invention to have a similar or
only slightly higher degree of deformation than binder systems where alkali metal
silicate is absent. In contrast, binder systems comprising a larger amount of alkali
metal silicate exhibit a significant increase in the degree of deformation, which is
undesirable. In addition, the use of alkali metal silicate in accordance with the
invention may enable a reduction of the amount of binder without a significant loss
in physical properties of the obtained agglomerates.
The amount of alkali metal silicate preferably is at most/0.07 percent by weight
(wt%), and most preferably at most 0.06 wt%, based on the total weight of dry iron
ore agglomerate. By "dry iron ore agglomerate" is meant the total of all ingredients
used in the formation of the iron ore agglomerate except water. Preferably, the
amount of alkali metal silicate is at least 0.02 wt%, and most preferably at least
0.04 wt%, based on the total weight of dry iron ore agglomerate. It was found that
pellets prepared using a binder system comprising at least 0.04 wt% of alkali metal
silicate generally have a smooth surface and. a higher resistance to abrasion,
whereas pellets prepared using a binder system comprising less than 0.04 wt% of
alkali metal silicate generally exhibit a rough surface, which can lead to the
generation of fines or debris during processing of the formed pellets, e.g. during
transport of the pellets.
The alkali metal silicate usually is a sodium silicate, but other alkali metal silicates
can be used. Examples of sodium silicates are sodium metasilicate and the
commercially available water glass. In the sodium silicates, the molar ratio

Na2O:SiO2 generally is in the range of 2:1 to 1:5, preferably in the range of 1:1 to
1:4. The amount of alkali metal silicate in the binder system generally is at least 1
wt%, preferably at least 10 wt%, and most preferably at least 15 wt%, and
generally it is at most 99 wt%, preferably at most 85 wt%, and most preferably at
most 75 wt%, based on the total weight of the binder system.
The alkali metal silicate preferably is well dispersed in the particles to be
agglomerated. The silicate can be added to the iron ore particles in the form of a
dry powder, an aqueous suspension, an aqueous solution, etc. Preferably, the
alkali metal silicate is added in the form of an aqueous solution.
The binder in the binder system of the invention can be an inorganic binder or an
organic binder, or a mixture thereof. Examples of inorganic binders are bentonite
and hydrated lime. In the context of the present application alkali metal silicate is
not considered to be an inorganic binder. Examples of organic binders are
polymers including:
(1) Water-soluble natural polymers, such as guar gum, starch, alginates, pectins,
xanthan gum, dairy wastes, wood related products, lignin, and the like;
(2) Modified natural polymers such as guar derivatives (e.g. hydroxypropyi guar,
carboxymethyl guar, carboxymethylhydroxypropyl guar), modified starch (e.g.
anionic starch, cationic starch), starch derivatives (e.g. dextrin), and cellulose
derivatives, such as alkali metal salts of carboxymethyl cellulose, hydroxyethyl
cellulose, hydroxypropyi cellulose, carboxymethylhydroxyethyl cellulose, methyl
cellulose, lignin derivatives (e.g. carboxymethyl lignin), and the like.
The aforesaid polymers may be used alone or in various combinations of two or
more polymers.

The binder system is free of synthetic polymers. Examples of synthetic polymers
are polyacrylamides, such as partially hydrated polyacrylamides, methacrylamide
and polymethacrylamide, polyacrylates and copolymers thereof, polyethylene
oxides, and the like.
A further aspect of the present invention is a process for producing iron ore
agglomerates comprising agglomerating fine iron ore particles in the presence of a
binder system wherein the binder system comprises carboxymethyl cellulose or a
salt thereof and an alkali metal silicate. The use of the combination of
carboxymethyl cellulose and alkali metal silicate leads to agglomerates with
increased physical properties, such as cold compression strength, preheat
strength, and dry crush strength. In addition, the reducibility of the iron in the
agglomerates generally is higher than is observed when a binder system
comprising an inorganic binder is used in the agglomeration process.
The invention further concerns a binder system comprising carboxymethyl
cellulose and an alkali metal silicate. The amount of alkali metal silicate in the
binder system generally is at least 1 wt%, preferably at least 10 wt%, and most
preferably at least 15 wt%, and generally it is at most 99 wt%, preferably at most
85 wt%, and most preferably at most 75 wt%, based on the total weight of the
binder system.
The carboxymethyl cellulose or the salt thereof (both are referred to as "CMC")
preferably is substantially water-soluble. Preferred salts of carboxymethyl cellulose
are alkali metal salts of carboxymethyl cellulose. Of these alkali metal salts the
sodium salt is preferred. The CMC used in the present invention generally has a
degree of substitution (the average number of carboxymethyl ether groups per
repeating anhydroglucose chain unit of the cellulose molecule) of at least 0.4,
preferably at least 0.5, and most preferably at least 0.6, and at most 1.5, more

preferably at least 1.2, and most preferably at most 0.9. Generally, the average
degree of polymerization of the cellulose furnish is at least 50, preferably at least
250, and most preferably at least 400, and generally it is at most 8,000, preferably
at most 7,000, and most preferably at most 6,000. it is more preferred to use
sodium carboxymethyl cellulose having a Brookfield viscosity in a 1% aqueous
solution of more than 2,000 cps at 30 rpm, spindle #4. Still more preferred is
sodium carboxymethyl cellulose having a Brookfield viscosity in a 1% aqueous
solution of more than about 4,000 cps at 30 rpm, spindle #4.
A series, of commercially available binders containing sodium carboxymethyl
cellulose especially useful in the present invention is available from Akzo Nobel,
under the trademark Peridur™.
The manner in which the binder is added to the particulate material depends on the
type of material being agglomerated, the type of binder being used, and the
desired results. For example, the binder may be added as a dry powder, an
aqueous suspension, an aqueous solution, an aqueous gel, an aqueous sol
(colloidal system), etc.
The amount of binder employed also varies with the results desired. For example,
when an organic binder is used, the amount of binder may range from 0.0025 to
0.5 wt.%, based on the weight of the iron ore particles, with a preferred range
being 0.005 to 0.2 wt.%. In the case of an inorganic binder, the amount of binder
may range for example from 0.1 to 3 wt.%, based on the weight of the iron ore
particles.
The binder and the alkali metal silicate can be added to the iron ore particles
together, one after the other, etc. This is not critical, so long as care is taken to

ensure that when the agglomeration takes place, the binder and the additive are
present to perform.
The process of the invention is useful in agglomerating fine iron ore particles. The
invention, however, is not limited to iron ores and is also useful in the
agglomeration of fine particles of other metal ores. This invention is particularly well
adapted for the agglomeration of materials containing iron, including iron ore
deposits, ore tailings, cold and hot fines from a sinter process, iron oxides from
dust collected in systems, or aqueous suspensions of iron ore concentrates from
natural sources or recovered from various processes. Iron ore or any of a wide
variety of the following minerals may form a part of the material to be
agglomerated: taconite, magnetite, hematite, Iimonite, goethite, siderite, franklinite,
pyrite, chaicopyrite, chromite, ilmenite, and the like.
The size of the material being agglomerated varies according to the desired
results. For example, when the particulate material being agglomerated is iron ore,
100% of the particles may be less than 80 mesh, preferably, 90% are less than 200
mesh, and most preferably, 75% are less than 325 mesh.
It is also envisaged to use conventional additives, for instance a base such as
sodium hydroxide, soda, or other additives such as sodium citrate, sodium oxalate,
etc. These additives, their purpose, and their use are known to the skilled person.
Many processes for the agglomeration of particles, especially metal-based
particles, are known in the art. Examples of such processes are peptization,
briquetting, sintering, etc. The binder system used in accordance with the invention
is particularly suitable for pelltization. In the mining industry it is common practice
to agglomerate or pelletize finely ground beneficiated mineral ore concentrate to
facilitate processing and handling/shipping of the ore. After the mineral ore has

been mined, it is frequently wet ground to liberate and separate unwanted gangue
minerals from the desired material, e.g. iron in the case of iron ore. The processed
wet ground ore is screened to remove large particles, which can be recycled for
further grinding. The screened fines are then vacuum filtered to reduce the
moisture content to an acceptable range for pelltization. The filtered mineral ore is
known in the art as "concentrate". A second process involves "dry grinding" and
beneficiation of the mineral ore, in which case the moisture required for
pelltization is added afterwards.
After beneficiation, a binding agent is added to the wetted mineral ore concentrate
and the binder/mineral ore composite is conveyed to a balling drum or other means
for pelletizing the ore. The binding agent serves to hold or bind the mineral ore
together, so that the individual agglomerates can be transported without losing
their integrity en route to further processing and induration.
Following the balling drum operation, the pellets are formed, but they are still wet.
These wet pellets are commonly referred to as "green pellets" or "green balls".
These green pellets are thereafter transported to a kiln and heated in stages to an
end temperature of about 1,300-1,350°C. In the pelletizing process, the wet green
pellets are loaded into the furnace for further processing. The moisture in the
pellets is removed by induration at temperatures normally between 400-600°C.
Following drying in the furnace, the pellets are transported to the preheat zone.
This is an additional heating stage to further increase the pellets' hardness before
they are transported to the kiln and/or final firing stage. Heating generally occurs at
900-1,200°C to bind the pellets together (e.g. to oxidize magnetite or crystallize
hematite). From the preheat zone, the pellets are dropped 10-15 feet from the
grate to the kiln. This is where the preheat strength is needed to prevent the pellets
from chipping and breaking apart into dust particles. Finally, the preheated pellets
are fired at a temperature of between 1,300 and 1,350°C.

The ability of the pellets to withstand breakage throughout processing can be
approximated by performing standard tests that measure the strength the pellets
will need at each stage of processing, (e.g. wet crush strength, dry crush strength,
preheat strength, and cold compressive strength).
The present invention is illustrated in the following Examples.
Examples
In the following Examples green pellets of iron ore comprising various compounds
in the amounts indicated in Table 1 were prepared. The green pellets were
prepared by agglomerating iron ore concentrate in the presence of a binder and a
binder additive. The amounts of binder and/or sodium silicate (in percent by
weight) shown in Table 1 are based on the total weight of the iron ore concentrate.
The iron ore concentrate employed in the Examples of Table 1 was Brazilian
hematite ore. The binder is Peridur 330 (ex Akzo Nobel), which comprises sodium
carboxymethyl cellulose and sodium carbonate, and the sodium silicate
(Na2O:SiO2 is 1:3.3) used in these experiments is supplied by PQ Corporation.
The process of making agglomerates are generally known to the skilled person.
The process is described in detail in US 6,071,325, which discloses a process of
making agglomerates of 2,500 grams in a rotating airplane tire (approximately 40
cm diameter).
First the binder was mixed into the dry concentrate and homogenized. Then, the
alkali metal silicate was mixed with the required amount of water (moisture content
between 8 and 9 wt%) and subsequently thoroughly mixed with the concentrate
and the binder (using a Mullen Mixer model No. 1 Cincinnati Muller, manufactured
by National Engineering Co. or the like). Pellet "seeds" were formed by placing a
small portion of the concentrate in the rotating tire and adding atomized water to
initiate pellet growth. Seed pellets with a size between 3.5 and 4 mm were retained
and kept apart for the formation of pellets with the desired size of 11.2 and 12.5

mm. Finished green pellets were produced by placing 165 grams of seed pellets
described above in the rotating tire and adding a portion of the remaining
concentrate mixture over a 3-minute growth period. Atomized water was added if
necessary.

The moisture content, the drop number, and the wet and dry compressive
strengths of the obtained green pellets were measured.
Wet drop number
The Wet drop number was determined by repeatedly dropping a green pellet
having a size between 11.2 and 12.5 mm from a height of 46 cm onto a
horizontally placed steel plate until a visible crack formed in the pellet surface. The
number of times the pellet was dropped up to the point of fracture/cracking was
determined. The average number of times averaged over 20 green pellets is
referred to as the "Wet drop number".
Wet compressive strength
20 wet green pellets having a size of between 11.2 and 12.5 mm were stored in an
airtight container. One by one the pellets were removed and placed in a standard
measuring device in which a plunger of a scale was lowered onto the green pellet
at a speed of 25 mm per minute. The maximum applied force at which the pellet

cracked was determined. The average force averaged over 20 green pellets is
referred to as the Wet compressive strength.
Deformation
A minimum of 20 wet green pellets having a size of between 11.2 and 12.5 mm
were stored in an airtight container. One by one the pellets were removed and
placed in a standard measuring device in which a plunger of a scale was lowered
onto the green pellet at a loading rate of 25 mm per minute. The machine (Model
Lloyd Texture Analyser TA-Plus, controlled by PC with Nexygen version 4.5
software) is equipped with a 50 N load-cell and has a probe diameter of 10 mm.
The deformation/deflection of the green pellet is recorded while increasing the
force. The deformation is defined as the change in diameter of the green pellet at a
force of 1 N, provided that the pellet is not ruptured at this point.
Dry compressive strength
20 green pellets having a size of between 11.2 and 12.5 mm were dried in an oven
at 105°C for a minimum of two hours. Following drying, the dried pellets were
placed one by one in a standard measuring device in which a plunger of a scale
was lowered onto the green pellet at a speed of 25 mm per 10 seconds. The
maximum applied force at which the pellet cracked was determined. The average
force averaged over 20 green pellets is referred to as the Dry compressive
strength.
The values obtained for the above parameters are tabulated in the Table below.


From the above Table it can be deduced that the pellets of Examples 1-4, which
are in accordance with the invention, show an increased dry compressive strength
compared to the pellets obtained using a binder system comprising only the
Peridur binder (Comparative Example 1). At the same time the pellets of Examples
1-4 show an improvement in wet drop number and only a slight increase in
deformation, whereas the pellets of Comparative Example 2 reveal a significantly
higher deformation and wet drop number. Consequently, the pellets of
Comparative Example 2 will be deformed in the steel making process to a much
higher extent than the pellets of the invention, rendering the process for preparing
fired pellets less efficient compared to processes using the pellets of the invention.
It is further noted that the appearance of the green pellets of Examples 2-4 is
smooth and non-sticking, whereas the green pellets of Comparative Example 1 are
rough. The pellets of Examples 2-4 will generate a lower amount of fines or debris,
e.g. during transport of these pellets, compared to the pellets of Comparative

Example 1. Although the green pellets of Comparative Example 2 are smooth, they
are sticky, causing undesirable clustering of the pellets during processing.

We Claim:
1. A process for producing iron ore agglomerates comprising agglomerating fine
iron ore particles in the presence of a binder system wherein the binder system comprises
a binder and alkali metal silicate and wherein the alkali metal silicate is present in an
amount of between 0.0001 to 0.07 percent by weight, based on the total weight of dry
iron ore agglomerate, wherein the binder system is free of synthetic polymer.
2. The process as claimed in claim 1 wherein the binder is carboxymethyl cellulose.
3. The process as claimed in either of claims 1 and 2 wherein the amount of alkali
metal silicate is between 0.04 and 0.07 percent by weight, based on the total weight of
dry iron ore agglomerate.
4. The process as claimed in any one of the preceding claims wherein the alkali
metal silicate is sodium silicate.


The present invention relates to a process for producing iron ore agglomerates comprising
agglomerating fine iron ore particles in the presence of a binder system wherein the
binder system comprises a binder and an alkali metal silicate and wherein the alkali metal
silicate is present in an amount of between 0.0001 to 0.08 percent by weight, based on the
total weight of dry iron ore agglomerate, wherein the binder system is free of synthetic
polymer, and preferably comprises carboxymethyl cellulose as binder.

Documents:

01910-kolnp-2006-abstract.pdf

01910-kolnp-2006-claims.pdf

01910-kolnp-2006-correspondence others-1.1.pdf

01910-kolnp-2006-correspondence others-2.1.pdf

01910-kolnp-2006-correspondence others.pdf

01910-kolnp-2006-correspondence-1.3.pdf

01910-kolnp-2006-description(complete).pdf

01910-kolnp-2006-form-1.pdf

01910-kolnp-2006-form-18.pdf

01910-kolnp-2006-form-3-1.1.pdf

01910-kolnp-2006-form-3.pdf

01910-kolnp-2006-form-5.pdf

01910-kolnp-2006-g.p.a.pdf

01910-kolnp-2006-international publication.pdf

01910-kolnp-2006-international search authority report.pdf

01910-kolnp-2006-pct form.pdf

1910-KOLNP-2006-(05-01-2012)-FORM-27.pdf

1910-KOLNP-2006-ABSTRACT 1.1.pdf

1910-KOLNP-2006-AMANDED CLAIMS.pdf

1910-kolnp-2006-assignment.pdf

1910-KOLNP-2006-CANCELLED PAGES.pdf

1910-KOLNP-2006-CORRESPONDENCE 1.1.pdf

1910-KOLNP-2006-CORRESPONDENCE-1.2.pdf

1910-kolnp-2006-correspondence1.3.pdf

1910-KOLNP-2006-DESCRIPTION (COMPLETE) 1.1.pdf

1910-kolnp-2006-examination report.pdf

1910-KOLNP-2006-FORM 1 1.1.pdf

1910-KOLNP-2006-FORM 13.1.1.pdf

1910-kolnp-2006-form 13.2.pdf

1910-KOLNP-2006-FORM 13.pdf

1910-kolnp-2006-form 18.pdf

1910-KOLNP-2006-FORM 2.pdf

1910-kolnp-2006-form 26.pdf

1910-KOLNP-2006-FORM 3 1.1.pdf

1910-kolnp-2006-form 3.2.pdf

1910-KOLNP-2006-FORM 3.pdf

1910-KOLNP-2006-FORM 5 1.1.pdf

1910-kolnp-2006-form 5.pdf

1910-kolnp-2006-gpa.pdf

1910-kolnp-2006-granted-abstract.pdf

1910-kolnp-2006-granted-claims.pdf

1910-kolnp-2006-granted-description (complete).pdf

1910-kolnp-2006-granted-form 1.pdf

1910-kolnp-2006-granted-form 2.pdf

1910-kolnp-2006-granted-specification.pdf

1910-KOLNP-2006-OTHERS 1.1.pdf

1910-KOLNP-2006-OTHERS.pdf

1910-kolnp-2006-others1.2.pdf

1910-KOLNP-2006-PA.pdf

1910-KOLNP-2006-PETITION UNDER RULE 137.pdf

1910-KOLNP-2006-RECEIPT.pdf

1910-KOLNP-2006-REPLY TO EXAMINATION REPORT.pdf

1910-kolnp-2006-reply to examination report1.1.pdf


Patent Number 248716
Indian Patent Application Number 1910/KOLNP/2006
PG Journal Number 32/2011
Publication Date 12-Aug-2011
Grant Date 09-Aug-2011
Date of Filing 07-Jul-2006
Name of Patentee AKZO NOBEL N.V.
Applicant Address VELPERWEG 76, NL-6824 BM ARNHEM
Inventors:
# Inventor's Name Inventor's Address
1 SCHMITT JAMES JOHN 7636 DUSK STREET LITTLETON, CO 80125
2 SMEINK RONALD GEERT TUBANTENLAAN 1 NL-7312 TP APELDOORN
PCT International Classification Number C22B 1/24
PCT International Application Number PCT/EP2004/014017
PCT International Filing date 2004-12-08
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/529,000 2003-12-12 U.S.A.