Briquette production and extrusion of iron ore

Abstract

The present invention relates to the use of polyacrylamide and sodium silicate for the cold agglomeration of iron ore, the polyacrylamide playing both the role of binder and activator of the sodium silicate.

Description

Title of the invention: Briqueting and extrusion of iron ore. Technical field of the invention and prior art.

[0001] Traditionally, pig iron is produced in blast furnaces by reducing iron ore through mixing with coke. Sintering, which involves moistening a poorly homogeneous coke-ore mixture and then drying it, is the main process. Agglomeration by pelleting using a plate-type apparatus is also used.

[0002] Coke produces a significant amount of CO2, and the entire steel industry must develop processes that do not use this product.

[0003] The trend is to modify blast furnaces, with ore reduction using gas or hydrogen, to reduce CO2 in pig iron production.

[0004] Furthermore, direct reduction methods (DR1) use both electrical energy to heat the ore, and gas or hydrogen to reduce the ore to a fairly low temperature of 900°C giving a solid porous iron.

[0005] For this, it is essential to produce briquettes or extrudates, as rich as possible in iron oxide, and having significant mechanical strength at high temperatures.

[0006] This search for briquettes and extrudates, with a high iron oxide content, with high mechanical strength at high temperature, requires the following additives:

[0007] 1. A binder for obtaining high-resistance pellets or extrudates at low temperatures resistance. The best low-temperature binders are: - Bentonite is widely used, but has the disadvantage of increasing impurities in the final product. - Organic binders, for example, starch, molasses, tars, lignosulfonate, polyvinyl alcohol, polyacrylamide, CMC... But these binders do not provide resistance at high temperatures. - A high-temperature binder known for a very long time through its use in foundry sands, but which gives no binding effect at low temperatures. This is sodium silicate.

[0008] 2. A sodium silicate activator. Indeed, in order for it to act as a binder, the silicate must be activated: - Either by an acid formed after briquetting, and in particular, esters, which hydrolyze with the basicity of the silicate, and which transform the silicate into colloidal silica, which, upon drying, has a very high agglomerating power; - Either by CO2, widely used in porous foundry sand, but which requires very long processing times on very compact briquettes; - Either by lime, which has a strong binding power in the form of calcium silicate. - Or other divalent metal compounds, magnesium oxide, talc, olivine, ... But most of these activators have a long reaction time and require storage at room temperature for 3 to 20 days.

[0009] 3. Portland cement or aluminous cement which brings significant impurities.

[0010] 4. Various ingredients having ancillary functions: nanomaterials, such as nano Carbon tubes to increase strength, glycerin, triethanolamine, fine iron or oxide dust, ... Invention

[0011] It has been discovered that polyacrylamide, which is a good cold binder, can also act as an activator for sodium silicate during the drying and heating of the briquettes. Furthermore, this process allows for very rapid activation of the silicate with virtually immediate drying and heat treatment. The process is also applicable to waste from the metallurgical industry, ferroalloys, and ores such as nickel, chromium, etc.

[0012] The invention therefore relates to the use of only polyacrylamide and sodium silicate for the cold agglomeration of iron ore characterized in that the polymer plays both the role of binder and activator of sodium silicate.

[0013] The invention relates to the use of polyacrylamide as a binder and sole activator of sodium silicate in a cold agglomeration process of iron ore.

[0014] The polyacrylamides used are either homopolymers of acrylamide, or copolymers, with other monomers.

[0015] Given the variability of iron ore in chemical composition, in particular in impurities, physical composition, in particular particle size distribution or hydrophilicity and in moisture content, it is necessary for each ore to define the most suitable polyacrylamide by compaction, drying, and baking tests.

[0016] In practice, polyacrylamide is chosen from anionic, cationic, amphoteric or non-ionic acrylamide copolymers according to the variability of the ore to obtain suitable compositions and particle sizes determined by test.

[0017] These polyacrylamides are characterized by their composition, molecular weight and molecular distribution, branching rate, hydrophilicity or hydrophobicity...

[0018] The basic polyacrylamide is a polymer of acrylamide.

[0019] We then distinguish: - Anionic copolymers where acrylamide is copolymerized with a monomer anionic: especially acrylic acid or AMPS (acrylamidopropane sulfonate), maleic acid, vinylsulfonic acid, itaconic acid, vinylphosphonic acid in the form of sodium, potassium or ammonium salts, ... - Cationic copolymers containing a cationic comonomer: dimethylamino ethyl (metha)acrylate, dimethylamino propyl acrylamide, DADMAC (dimethyl diallyl ammonium chloride) or similar monomers quaternized by methyl chloride, methyl sulfate, benzyl chloride.

[0020] In addition to anionic monomers, non-ionic monomers can be introduced which can also impart hydrophilicity or hydrophobicity, such as polyoxyethylene glycol acrylate, butyl acrylate, ...

[0021] These polymers can be further branched or partially crosslinked by versatile monomers: methylene bis acrylamide, polyethylene glycol diacrylate... or heat-crosslinking monomers such as methylolacrylamide.

[0022] With the possibility of using amphoteric polymers from anionic and cationic monomers.

[0023] These polymers can have molecular weights from a few thousand up to 25 million. The required particle size is determined by tests, e.g., 0-300 microns / 0-500 microns / 0-800 microns. Process

[0024] The process for producing briquettes or extrudates generally consists of mixing: - The binder, - Sodium silicate, - The activator, - A certain quantity of water from the ore or added, - And various other ingredients.

[0025] which are molded in a mechanical press, in the form of "briquettes", at a pressure close to 200 bar, i.e. 35 kN / cm linear, or in vacuum extruders, to avoid the inclusion of air bubbles at high pressure. The extruded product is cut into pieces of various sizes.

[0026] These briquettes and extrudas are then dried between 150°C and 400°C, at a fairly low speed, to avoid their explosion by sudden vaporization of the water.

[0027] More specifically, the process for obtaining agglomerates of iron ore fines comprises the following steps: a) Mix the polyacrylamide, sodium silicate and the ore in a mixer under defined conditions; b) Adjust the moisture content for compaction within a range of 2 to 10% preferably c) Adjust the moisture content for extrusion from 5 to 20%, preferably 9 to 18%, then perform the extrusion using a vacuum extruder and finally dry the extrudates at a temperature of 100 to 250°C for 30 minutes to 2 hours or, c) Adjust the moisture content for extrusion from 5 to 20%, preferably 9 to 18%, then perform the extrusion using a vacuum extruder and finally dry the extrudates at a temperature of 100 to 250°C for 30 minutes to 2 hours.

[0028] The test to confirm the quality of the agglomerated product then consists of heating to 900°C to measure their resistance.

[0029] The current requirements for molding treatments are: - Cold resistance, - Resistance after drying, - Resistance after heating to 900°C.

[0030] In practice, no activator other than polyacrylamide is added to treat sodium silicate.

[0031] According to the invention, the silicate is in solid form in the form of powders, beads or microbeads or in liquid form by adjusting the amount of water required for mixing.

[0032] In practice, the following dosages are used: 0.01% to 2% by weight of polyacrylamide polymer relative to the total weight of the agglomerate formed and 0.1% to 5% by weight of active sodium silicate relative to the total weight of the agglomerate formed.

[0033] In other words, 0.01% to 2% by weight of polyacrylamide polymer is mixed with respect to the total weight of the agglomerate formed and 0.1% to 5% by weight of active sodium silicate is mixed with respect to the total weight of the agglomerate formed.

[0034] In a particular embodiment, a hydrophobic polyacrylamide is added to reduce sensitivity to humidity.

[0035] The invention also relates to the briquettes obtained by the process described above, the briquettes having a press recycling of less than 20%, a green briquette burst test greater than 80%, a dry briquette burst strength greater than 99% and a DCS greater than 200 kg.

[0036] According to another characteristic, the briquettes obtained are of very high purity unlike bentonite as a binder or lime as an activator of sodium silicate.

[0037] Finally, the briquettes according to the invention are dried and baked without aging, unlike other activators. Examples

[0038] The purpose of these examples is to illustrate the high quality and good properties of the agglomerated products obtained.

[0039] The concentrated iron ores used in the examples are the concentrate of magnetite and hematite ores (concentrated and crushed).

[0040] Magnetite #1 is a float concentrate with an Fe content of approximately 68%, a particle size of less than 100 pm, a D80 of 74 pm, and a Blaine index between 2300 and 2500. The magnetite concentrate originates from Ukrainian deposits. The Blaine index is a unit, expressed in cm² / g, measuring the specific surface area in the particle and powder domain.

[0041] Hematite #2 is ground hematite, with an Fe content of about 66%, a particle size of less than 300 pm with a D80 = 100 pm, a Blaine index between 1950 and 2100. The hematite comes from Canadian deposits in particular.

[0042] Hematite #3 is a floated hematite, with an Fe content of about 69%, a particle size of less than 100 pm with a D80 = 74 pm, a Blaine index between 2100 and 2300. The hematite comes from Canadian deposits in particular.

[0043] The tests were carried out by varying the dosage and nature of the organic binders and iron ores, as illustrated in the examples below.

[0044] To prepare these agglomerates, in a first step, the polymer is mixed with sodium silicate in solid or liquid form and homogenized with the necessary amount of water (moisture content between 2 and 5% by weight) to obtain a binding mixture. The ore concentrate is mixed with the agglomerate mixture using a KitchenAid® type mixer (up to 3 kg of concentrate) and an Eirich, Lödige, or Hobart type mixer (more than 3 kg of concentrate and up to 40 kg).

[0045] After a mixing time of 4 to 8 minutes, the ore concentrate is introduced into the inlet hopper of a tangential wheel compactor (roller press) or a vacuum extruder.

[0046] The agglomerates produced with the compactors are called briquettes and have a size of between 30 and 50 mm for volumes of between 5 and 10 cm3. The compactors can be of the brand Köppern and affiliates (Komarek and Euragglo) or Sahut-Conreur.

[0047] The agglomerates produced with the extruder are called plugs and have a size between 30 and 50 mm for volumes between 2.5 and 5 cm3. The extruders can be of the brand Verdes or JC STEELE and affiliates (Handle).

[0048] These agglomerates are placed in the low temperature oven, which is set for example at 105°C, for a time between 30 minutes and 2 hours to dry them completely.

[0049] Several tests were carried out to confirm the quality of the agglomerated product, which exhibits high physical resistance to handling and vibration during transport.

[0050] In this context, it refers to a series of tests during which different parameters were measured:

[0051] 1. Appearance test of the briquettes: visual test, the agglomerate must be well formed, the The shape is that of a rectangular pebble or a cylinder. A smooth exterior and efficient interlocking are desired (no gaps, cracks or layering).

[0052] 2. Press recycling: The principle of this test is to measure the percentage The fine ore aggregate required for a complete briquetting process is sieved to 6.3 mm immediately after pressing to check the quality of the pellets. At this stage, the green pellets have a drop height of 1.5 m, which is sufficient to verify their strength. The weight of each portion (above and below 6.3 mm) is measured. The proportion of each portion is expressed as a percentage of the total mixture weight. Results are given as a percentage – good results are between 0 and 20%.

[0053] 3. Burst tests: This test measures the resistance of the briquettes during the Transport between the roller press and the kiln. The wet drop count is determined by repeatedly dropping 500 g of briquettes from a height of 2 m onto a horizontally placed steel plate, through an open, vertical plastic tube. The tube diameter is 20 cm. After the first drop, all the briquette particles (fines, pieces, or briquettes) are collected and returned to the plate for a second drop. After this second drop, everything is collected again and weighed. The results are given as a percentage over 10 mm. The limit is 80% of good quality briquettes.

[0054] 4. Low-temperature dry hardness: agglomerates placed in an oven at a The temperature should be kept below 250°C, preferably between 90°C and 150°C, for a period of 15 minutes to 2 hours to ensure complete drying. After drying, 20 dry agglomerates are placed individually in a standard hardness tester, such as those sold under the SCAINE brand. The maximum force applied at which the pellet cracks or breaks is determined. The average of these 20 measurements is called the "dry compressive strength" (DCS). Results are given in kg / agglomerate. It should be noted that 500 kg is the upper limit of the manual test, a limit that is perfectly validated for excellent quality.

[0055] 5. Hardness after 900°C: the agglomerates are placed in a 900°C oven for The burnt pellets are left for 20 minutes to remove organic matter. They are then placed individually in a standard hardness tester, such as those sold under the SCAINE brand. The maximum force at which the pellet cracked is determined. The average of these 20 measurements is called "dry compressive strength" (DCS). Results are given in kg / pellet. It should be noted that 500 kg is the upper limit of the manual test, a limit that is perfectly validated for excellent quality.

[0056] 6. Water Resistance Tests: The agglomeration of certain very fine ores or More hydrophilic materials can lead to low water resistance in the agglomerates, and therefore possible disintegration of the briquettes during storage / transport. To mitigate this, we propose adding a water-repellent agent, if necessary, to make the dry briquettes water-resistant for several weeks. Twenty briquettes are then completely submerged in water-filled containers and left for several days to several weeks. Visual checks are carried out at defined intervals.

[0057] 7. Drum and Abrasion Test: Method for providing a measurement relative for the evaluation of the resistance of iron ores to granulometric degradation by impact (tumbling in the drum) and abrasion (formation of fines). A portion of agglomerates (2 kg, or approximately 50 briquettes) is placed in a circular drum for a total of 200 revolutions at 25 rpm. The drum is opened, and all the material present is sieved to a particle size between 6.3 mm and 500 sq m. The Drum Index is expressed as the percentage by mass of material larger than 6.3 mm, and the Abrasion Index as the percentage by mass of material smaller than 500 sq m. The standard values ​​used here are: - Drum index: 80% > 6.3 mm - Abrasion index: 10% < 500 qm. Example 1:

[0058] The tests in this example are carried out on a tangential wheel press. We use a concentrate of iron ore from Ukraine, floated magnetite, with an Fe content of 68.1%, a particle size of less than 100 µm, with a D80 = 74 µm, a Blaine index between 2300 and 2500. We adjust the moisture content and add our bonding formula as shown in Table 1.

[0059] The PAM used is an acrylamide / sodium acrylate (70-30) copolymer with a molecular weight of 18 million and a particle size of 0 to 800 microns.

[0060] Sodium silicate is used in powder form; it is a silicic acid, sodium salt (MR>3.2). Sodium silicate is a well-known binder for briquetting and is primarily used in the recycling of steel fines. It offers good performance in hot processes, allowing the agglomerates to withstand the high temperatures of furnaces (blast furnaces, converters, electric arc furnaces).

[0061] [Tables 1] Table 1 Moisture (%) Binders (%) PAM Silicate Powder Example 1 S 1

[0062] Table 1: Example 1

[0063] We mix for 4 minutes in an intensive mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the press at a pressure of 200 bar, or 30 kN / m linear, and perform the following measurements (Table 2):

[0064] [Tables2] Table 2 Recycling Press (%) Bursting Test Green Briquettes Bursting Test Dry Briquettes DCS (kg) Dry (105°C) DCS (kg) Firing (900°C) Drum Index (¾) Abrasion Index (%) Example 1 20 83 99.8 239 195 86 9

[0065] Table 2: Example 1

[0066] Example 1 shows that the use of PAM and sodium silicate gives good results for green briquettes (press recycling and burst tests on green briquettes), which was known as a property given by PAM.

[0067] The example shows that this formula also gives very good results on dry briquettes, burst tests show no breakage or generation of fine particles, and the compressive strength is very high, exceeding the requirements (200 kg).

[0068] Example 1 shows that the formula is also good for hot tests, where the PAM has disappeared, the compressive strength shows that the briquettes retain their integrity and their strength at a value acceptable for the process.

[0069] Example 1 shows that the formula gives good results for the Drum and Abrasion Indices, this indicates that the briquettes can be handled and transported without damage for the final process (passage in the kiln). Example 2:

[0070] We use the same equipment and the same sample of iron ore concentrate as in Example 1. We adjust the moisture content and add another binding formula as shown in Table 3. The objective is to determine whether PAM alone can work for cold-bonded briquettes.

[0071] [Tables3] Table 3 Moisture (%) Binders (%) PAM Silicate Powder Example 2 5 1 0

[0072] Table 3: Example 2

[0073] We mix for 4 minutes in a high-powered mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the press at a pressure of 200 bar, or 30 kN / m linear, and perform the following measurements (Table 4):

[0074] [Tables4] Table 4 Recycling Press (%) Bursting Test Green Briquettes Bursting Test Dry Briquettes DCS (kg) Dry (1053°C) DCS (kg) Firing (900°C) Drum Index (%) Abrasion Index (%) Example 18 82.5 99.1 155 67 61.8 29.4

[0075] Table 4: Example 2

[0076] Example 2 shows that the use of PAM alone gives good results for green briquettes (press recycling and burst tests on green briquettes), which was known as a property given by PAM.

[0077] The example shows that this formula also gives very good results on dry briquettes, burst tests show no breakage or generation of fines, but the compressive strength is too low to meet the requirements after firing at 900°C.

[0078] Example 2 shows that the formula cannot be validated due to the poor results obtained during the hot tests, during which the PAM disappeared.

[0079] Example 2 shows that the formula gives poor results for the Drum and Abrasion Indices, the bonds of the polymer alone are not strong enough to withstand multiple handling and transport. Example 3:

[0080] We use the same equipment and the same sample of iron ore concentrate as in Example 1. We adjust the moisture content and add another bonding formula as shown in Table 5. The objective is to determine whether sodium silicate alone can work for cold-bonded briquettes.

[0081] [Tables5] Table 5 Moisture (%) Binders (%) PAM Silicate Powder Example 3 5 0

[0082] Table 5: Example 3

[0083] We mix for 4 minutes in an intensive mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the press always at the same pressure and we carry out the following measurements (table 6):

[0084] [Tables] Table 6 Recycling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes Example 3 52 33.2 71.3

[0085] Table 6: Example 3

[0086] Example 3 shows that the use of sodium silicate alone does not give good results; the green briquettes are too fragile and too weak to withstand drops and transport from the press to the oven.

[0087] Example 3 shows that the formula cannot be validated due to poor results in recycling and bursting tests (green and dry). Therefore, drying, baking, and index tests (drum and abrasion) were not performed. Example 4:

[0088] We use the same sample of iron ore concentrate as in Example 1. We adjust the moisture content and add another bonding formula as shown in Table 7. The objective is to determine whether CMC can be used for cold-bonded briquettes.

[0089] CMC, carboxymethylcellulose, is a binder used for granulating iron ore, similar to PAM polymers. It is a cellulosic derivative with long carbon chains. It is known to have binding properties comparable to those of PAM polymers, with good pelletizing properties and good strength (in its green, dry, and baked states). We tested CMC at the same dosage as PAM.

[0090] [Tables7] Table 7 Moisture (%) Binders (%) CMC Silicate Powder Example 4 5 1 ?

[0091] Table 7: Example 4

[0092] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the roller press and perform the following measurements (Table 8):

[0093] [Tables8] Table 8 Recycling Rolling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes DCS (kg) Dry (105%) Drum Index (%) Abrasion Index (%) Example 4 1S 82.1 99.6 115 57.6 32.7

[0094] Table 8: Example 4

[0095] Example 4 shows that the use of CMC gives good results for the recycling of green briquettes and that burst tests do not reveal any breakage or generation of fine particles, which was known as a given property of CMC.

[0096] Example 4 reveals that this formula gives poor results on dry briquettes, the compressive strength being too low to meet the requirements (200 kg). This binder formula is not validated, therefore hot tests (900°C) were not carried out.

[0097] Example 4 shows that the formula gives poor results for the Drum and Abrasion Indices, the bonds with the CMC are not strong enough to withstand multiple handling and transport. Example 5:

[0098] We use the same equipment and the same sample of iron ore concentrate as in Example 1. We adjust the moisture content and add another binder formula as shown in Table 9. The objective is to determine whether other well-known binders can produce cold-bonded briquettes that meet the technical requirements; here we test bentonite.

[0099] Bentonite is a well-known binder for granulating iron ore, used for decades. Bentonite is a clay-type montmorillonite with a high silicate content, which gives the pellets good plasticity and strength (both in the green, dry, and baked states).

[0100] [Tables9] Table 9 Moisture (%) Binders (%) Bentonite Silicate Powder Example 5 5 "5 "J

[0101] Table 9: Example 5

[0102] We mix for 5 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the press at the same pressure and perform the following measurements (Table 10):

[0103] [TableauxlO] Table 10 Recycling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes DC S (kg) Dry (105*0) Drum Index (%) Abrasion Index (%) Example 5 20 SS,7 85 70 61.7 34.3

[0104] Table 10: Example 5

[0105] Example 5 shows that the use of bentonite gives good results for the recycling of green briquettes and that burst tests do not reveal any breakage or generation of fines, which was known as a property given by bentonite and because we set the humidity level at a higher level to maintain a good bonding phenomenon.

[0106] Example 5 reveals that this formula gives poor results on dry briquettes, the compressive strength being too low to meet the requirements (200 kg). This binder formula is not validated, therefore hot tests (900°C) were not carried out.

[0107] Example 5 reveals that the formula gives poor results for the Drum and Abrasion Indices, the bonds with the bentonite are not strong enough to withstand multiple handling and transport. Example 6:

[0108] We use the same equipment and the same sample of iron ore concentrate as in Example 1. We adjust the moisture content and add another bonding formula as shown in Table 11. The objective is to determine whether bentonite at a higher dosage can be used for cold-bonded briquettes.

[0109] [Tableauxll] Table 11 Moisture (%) Binders (%) Bentonite Silicate Powder Example 6 5 4

[0110] Table 11: Example 6

[0111] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the press always at the same pressure and we carry out the following measurements (table 12):

[0112] [Table 12] Table 12 Recycling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes DCS (kg) Dry (WS°C) Drum Index (%J) Abrasion Index (%) Example 6 16 893 91 88.7 60.1 32.8

[0113] Table 12: Example 6

[0114] Example 6 reveals that this formula with a higher dosage of bentonite gives poor results on dry briquettes; the compressive strength is too low to meet the requirements (200 kg). The hot test was therefore not carried out because the formula was disqualified.

[0115] Example 6 shows that the formula gives poor results for the Drum and Abrasion Indices, the bonds with the bentonite are not strong enough, even at higher dosages, to withstand multiple handling and transport. Example 7:

[0116] The tests in this example are carried out on a tangential wheel press. We use an iron ore concentrate from Canada. This is crushed hematite, with an Fe content of 66.8%, a particle size of less than 300 µm with a D80 = 100 µm, and a Blaine index between 1950 and 2100.

[0117] We use the same binding formula as in Example 1. The objective is to verify the effectiveness of the formulas on other types of iron ore concentrates. We adjust the moisture content and add our binding formula as shown in Table 13.

[0118] [Tables 13] Table 13 Moisture (%) Binders (%) P AM Silicate powder Example 7 7.5 1 ?

[0119] Table 13: Example 7

[0120] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the press at a pressure of 200 bar, i.e., 30 kN / m linear, and perform the following measurements (Table 14):

[0121] [Tables 14] Table 14 Recycling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes DCS (kg) Dry (10°C) DCS (kg) Firing (90°C) Drum Index (%) Abrasion Index (%) Example 13 84.1 99.8 231 180 84.9 9.1

[0122] Table 14: Example 7

[0123] Example 7 shows that the use of PAM and sodium silicate gives good results for green briquettes (press recycling and burst tests on green briquettes), which was known as a property given by PAM.

[0124] The example shows that this formula also gives very good results on dry briquettes, burst tests show no breakage or generation of fine particles, and the compressive strength is very high, exceeding the range of requirements (200 kg).

[0125] Finally, Example 7 shows that the formula is also good for hot tests, where the PAM has disappeared. The compressive strength shows that the briquettes retain their integrity and strength, within the required range.

[0126] Example 7 shows that the formula gives good results for the Drum and Abrasion Indices, this indicates that the briquettes can be handled and transported without damage for the final process (passage in the kiln). Example 8:

[0127] We use the same equipment and the same sample of iron ore concentrate as in Example 6. We adjust the moisture content and add another bonding formula as shown in Table 15. The objective is to determine whether PAM alone can work for cold-bonded briquettes.

[0128] We use the same bonding formula as in Example 2. The objective is to verify the effectiveness of the formulas on other types of iron ore concentrates.

[0129] [Tables 15] Table 15 Moisture (%) Binders (%) PAM Silicate Powder Example 8 7.5 1 0

[0130] Table 15: Example 8

[0131] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the press always at the same pressure and we carry out the following measurements (table 16):

[0132] [Tables 16] Table 16 Recycling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes DCS (kg) Dry ( 105 <c) dcs (kg.) cuisson (900ac) indice de tambour d’abrasion (%) exemple 8 19 84 99 173 18,1 63,1 30,7

[0133] Table 16: Example 8

[0134] Example 8 shows that the use of PAM alone gives good results for green briquettes (press recycling and burst tests on green briquettes), which was known as a property given by PAM.

[0135] The example shows that this formula also gives very good results for dry briquettes, burst tests show no breakage or generation of fines, but the compressive strength after firing at 900°C is too low to meet the requirements (200 kg).

[0136] Example 8 shows that the formula cannot be validated due to the poor results obtained during hot tests, where the PAM disappeared.

[0137] Example 8 shows that the formula gives poor results for the Drum and Abrasion Indices, the bonds of the polymer alone are not strong enough to withstand multiple handling and transport. Example 9:

[0138] We use the same equipment and the same sample of iron ore concentrate as in Example 6. We adjust the moisture content and add another bonding formula as shown in Table 17. The objective is to determine whether sodium silicate alone can work for cold-bonded briquettes.

[0139] We use the same bonding formula as in Example 3. The objective is to verify the effectiveness of the formulas on other types of iron ore concentrates.

[0140] [Tableauxl7] Table 17 Moisture (%) Binders (%) PAM Silicate Powder Example 9 7.5 0

[0141] Table 17: Example 9

[0142] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the press always at the same pressure and we carry out the following measurements (table 18):

[0143] [Tables 18] Table 1S Recycling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes Example 9 59 35.2 68.9

[0144] Table 18: Example 9

[0145] Example 9 shows that the use of sodium silicate alone does not give good results; the green briquettes are too fragile and too weak to withstand drops and transport from the press to the oven.

[0146] Example 9 shows that the formula cannot be validated due to poor results in recycling and bursting tests (green and dry). Therefore, drying, baking, and index tests (drum and abrasion) were not performed. Example 10:

[0147] We use the same iron ore concentrate sample as in Example 9. We adjust the moisture content and add another bonding formula as shown in Table 19. The objective is to determine whether CMC can be used for cold-bonded briquettes with this type of iron ore concentrate. We test CMC at the same dosage as PAM.

[0148] We use the same bonding formula as in Example 6. The objective is to verify the effectiveness of the formulas on other types of iron ore concentrates.

[0149] [Tables 19] Table 19 Moisture (%) Binders (%) CMC Silicate Powder Example 10 7.5 1 2

[0150] Table 19: Example 10

[0151] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the roller press and carry out the following measurements (Table 20):

[0152] [Tables20] Table 20 Recycling Press (¾) Burst Test Green Briquettes Burst Test Dry Briquettes. DCS (kg) Dry (105°C) Drum Index (H) Abrasion Index (%) Example 10 16.4 S2 99.7 122 59.4 34.1

[0153] Table 20: Example 10

[0154] Example 10 shows that the use of CMC gives good results for the recycling of green briquettes and that burst tests do not reveal any breakage or generation of fine particles, which was considered to be a property given by CMC.

[0155] Example 10 shows that this formula gives poor results for dry briquettes, the compressive strength being too low to meet the requirements (200 kg).

[0156] Example 10 shows that the formula cannot be validated due to poor DCS results at 105°C and hot tests. The same bonding phenomenon observed with PAM (high DCS) is not observed. The compressive strength is very low, which makes this formula unsuitable.

[0157] Example 10 shows that the formula gives poor results for the Drum and Abrasion Indices, the bonds with the CMC are not strong enough to withstand multiple handling and transport. Example 11:

[0158] We use the same equipment and the same sample of iron ore concentrate as in Example 6. We adjust the moisture content and add another binder formula as shown in Table 21. The objective is to determine if other well-known binders can produce cold-bonded briquettes that meet the technical requirements; here we test bentonite.

[0159] We use the same bonding formula as in Example 4. The objective is to verify the effectiveness of the formulas on other types of iron ore concentrates.

[0160] [Tables21] Table 21 Moisture (%) Binders (%) Bentonite Silicate Powder Example 11 8.1 ? •A

[0161] Table 21: Example 11

[0162] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the press at the same pressure and perform the following measurements (Table 22):

[0163] [Tables22] Table 7 7 Recycling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes DCS (kg) Dry (105*0) Drum Index (%) Abrasion Index Example 11 19 87 §4 75 6 63.1 36.4

[0164] Table 22: Example 11

[0165] Example 11 shows that the use of bentonite gives good results for the recycling of green briquettes and that burst tests do not reveal any breakage or generation of fines, which was known as a property given by bentonite and because we set the humidity level at a higher level to maintain a good bonding phenomenon.

[0166] Example 11 reveals that this formula gives poor results on dry briquettes, the compressive strength being too low to meet the requirements (200 kg). This binder formula is not validated, therefore hot tests (900°C) were not carried out.

[0167] Example 11 reveals that the formula gives poor results for the Drum and Abrasion Indices, the bonds with the bentonite are not strong enough to withstand multiple handling and transport. Example 12:

[0168] We use the same equipment and the same sample of iron ore concentrate as in Example 6. We adjust the moisture content and add another bonding formula as shown in Table 23. The objective is to determine whether bentonite at a higher dosage can be used for cold-bonded briquettes.

[0169] We use the same bonding formula as in Example 5. The objective is to verify the effectiveness of the formulas on other types of iron ore concentrates.

[0170] [Tables23] Table 23 Moisture (%) Binders (%) Bentonite Silicate Powder Example 12 S ,8 4 2

[0171] Table 23: Example 12

[0172] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the press at the same pressure and perform the following measurements (Table 24):

[0173] [Tables24] Table 24 Recycling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes DCS (kg) Dry (105°C) Drum Index (1¾) Abrasion Index (%) Example 12 17.2 88.8 90.4 89.5 61.8 33.5

[0174] Table 24: Example 12

[0175] Example 12 shows that the use of bentonite gives good results for recycling green briquettes and that burst tests reveal no breakage or generation of fines, which was known to be a property of bentonite and because we fixed the moisture content at a higher level to maintain good bonding. The higher dosage allows the briquettes to be more plastic.

[0176] Example 12 reveals that this formula with a higher dosage of bentonite gives poor results on dry briquettes; the compressive strength is too low to meet the requirements (200 kg). The hot test was therefore not carried out because the formula was disqualified.

[0177] Example 12 reveals that the formula gives poor results for the Drum and Abrasion Indices, the bonds with the bentonite are not strong enough, even at higher dosages, to withstand multiple handling and transport. Example 13:

[0178] The tests in this example are carried out on an extruder. We use the same sample of iron ore concentrate as in Example 1. We adjust the moisture content and add our bonding formula as shown in Table 25. The objective is to determine whether bentonite at a higher dosage can be used for cold-bonded briquettes.

[0179] We use the same bonding formula as in Example 5. The objective is to verify the effectiveness of the formulas on other types of iron ore concentrates.

[0180] [Tables25] Table 25 Moisture (%) Binders (%) PAM Silicate powder Example 13 11.9 1 "5

[0181] Table 25: Example 13

[0182] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the machine and carry out the following measurements (Table 26):

[0183] [Tables26] Table 26 Recycling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes DCS (kg) Dry (105°C) DCS (kg) Firing (POO°C) Drum Index (W) Abrasion Index (%) Example 13 92 99.9 224 189 88.7 7.8

[0184] Table 26: Example 13

[0185] Using an extruder requires significantly increasing the moisture content of the mixture compared to a tangential wheel press. The agglomerates are more moist, therefore the properties of the green agglomerates are improved.

[0186] Example 13 shows that the use of PAM and sodium silicate works well for this equipment due to the plasticity imparted by PAM. This binder formula gives good results for green agglomerates (press recycling and burst tests on green agglomerates), which was known to be a property conferred by PAM.

[0187] The example shows that this formula also gives very good results on dry agglomerates, burst tests show no breakage or generation of fine particles, and the compressive strength is very high, exceeding the requirements (200 kg).

[0188] Example 13 shows that the formula is also good for hot tests, where the PAM has disappeared, the compressive strength shows that the briquettes retain their integrity and their strength at a value acceptable for the process.

[0189] Example 13 shows that the formula gives good results for the Drum and Abrasion Indices due to the small size of the agglomerates (2.5 to 5 cm3). The agglomerates can be handled and transported without damage for the final process (passing through the kiln). Example 14:

[0190] We use the same equipment and the same sample of iron ore concentrate as in Example 13. We adjust the moisture content and add our bonding formula as shown in Table 27. The objective is to determine whether bentonite can be used for cold agglomeration.

[0191] [Tables27] Table 27 Moisture (%) Binders (%) Bentonite Silicate Powder Example 14 14.1 1.2

[0192] Table 27: Example 14

[0193] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the machine and carry out the following measurements (Table 28):

[0194] [Tables28] Table 28 Recycling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes DCS (kg) Dry (105°C) Drum Index (¾) Abrasion Index {%) Example 14 24 82 80 69.3 56.4 29.8

[0195] Table 28: Example 14

[0196] Example 14 shows that the use of bentonite gives results in line with the requirements for burst tests, which do not reveal any breakage or generation of fines, which was known as a property given by bentonite and because we set the humidity level at a higher level to maintain a good bonding phenomenon.

[0197] Example 14 reveals that the passage through the extruder is not optimal, difficulty in forming structured agglomerates, hence the creation of a non-negligible proportion of small pieces.

[0198] Furthermore, Example 14 indicates that this formula gives poor results on dry briquettes, as the compressive strength is too low to meet the requirements (200 kg). This binder formula is not validated, therefore hot tests (900°C) were not carried out.

[0199] Example 14 reveals that the formula gives poor results for the Drum and Abrasion Indices; the bonds with the bentonite are not strong enough, despite the smaller size of the agglomerates, to withstand multiple handling and transport. Example 15:

[0200] The tests in this example are carried out on an extruder. We use an iron ore concentrate from Canada. This is crushed hematite, with an Fe content of 66.8%, a particle size of less than 300 pm with a D80 = 100 pm, a Blaine index between 1950 and 2100.

[0201] We use the same bonding formula as in Example 1. The objective is to verify the effectiveness of the formulas on other types of iron ore concentrates.

[0202] We adjust the humidity level and add our bonding formula as shown in Table 29.

[0203] [Tables29] Table 29 Moisture (%) Binders (¾) PAM Silicate powder Example 15 15.2 1 ■'J

[0204] Table 29: Example 15

[0205] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the machine and carry out the following measurements (Table 30):

[0206] [Tables30] Table 30 Recycling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes DCS (kg) Dry (105°C) DCS (kg) Firing (900°C) Drum Index (%) Abrasion Index (%) Example 15 5.5 89.1 99.9 230 187 88.9

[0207] Table 30: Example 15

[0208] Using an extruder requires significantly increasing the moisture content of the mixture compared to a tangential wheel press. The agglomerates are more moist, therefore the properties of the green agglomerates are improved.

[0209] Example 15 shows that the use of PAM and sodium silicate works well for this equipment due to the plasticity imparted by PAM. This binder formula gives good results for green agglomerates (press recycling and burst tests on green agglomerates), which was known to be a property conferred by PAM.

[0210] The example shows that this formula also gives very good results on dry agglomerates, burst tests show no breakage or generation of fine particles, and the compressive strength is very high, exceeding the requirements (200 kg).

[0211] Example 15 shows that the formula is also good for hot tests, where the PAM has disappeared, the compressive strength shows that the briquettes retain their integrity and their strength at a value acceptable for the process.

[0212] Example 15 shows that the formula gives good results for the Drum and Abrasion Indices due to the small size of the agglomerates (2.5 to 5 cm3). The agglomerates can be handled and transported without damage for the final process (passing through the kiln). Example 16:

[0213] We use the same equipment and the same sample of iron ore concentrate as in Example 13. We adjust the moisture content and add our bonding formula as shown in Table 31. The objective is to determine whether bentonite can be used for cold agglomeration.

[0214] [Tables31] Table 31 Moisture (%) Binders (%) Bentonite Silicate Powder Example 16 18.4 1 ?

[0215] Table 31: Example 16

[0216] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the machine and carry out the following measurements (Table 32):

[0217] [Tables32] Table Recycling Press (%) Burst Test Green Briquettes Burst Test Dry Briquettes DCS (kg) Dry (105°C) Drum Index (%) Abrasion Index Example 16 19 85 82 69.3 54.1 77 7

[0218] Table 32: Example 16

[0219] Example 16 shows that the use of bentonite gives results in line with the requirements for burst tests, which reveal no breakage or generation of fines, which was known as a property given by bentonite and because we set the humidity level at a higher level to maintain a good bonding phenomenon.

[0220] Example 16 reveals that the passage through the extruder is not optimal, difficulty in forming structured agglomerates, hence the creation of a non-negligible proportion of small pieces.

[0221] Furthermore, Example 16 indicates that this formula gives poor results on dry agglomerates, the compressive strength being too low to meet the requirements (200 kg). This binder formula is not validated, therefore hot tests (900°C) were not carried out.

[0222] Example 16 reveals that the formula gives poor results for the Drum and Abrasion Indices, the bonds with the bentonite are not strong enough, despite the smaller size of the agglomerates, to withstand multiple handling and transport. Example 17:

[0223] The agglomeration of certain very fine or more hydrophilic minerals can lead to low water resistance in the agglomerates, and therefore possible disintegration of the briquettes during storage / transport. To overcome this, we propose adding a water-repellent agent to make the dry briquettes water-resistant for several weeks.

[0224] This water-repellent agent is a modified PAM, acrylamide / 2 Ethylhexyl-lacrylate copolymer (40 / 60 by weight) with a molecular weight of 2 to 4 million daltons.

[0225] We use an iron ore concentrate from Canada. It is a floated hematite, with an Fe content of 69%, a particle size less than 100 pm with a D80 = 74 pm, a Blaine index between 2100 and 2300.

[0226] We chose this mineral because it demonstrated a significant hydrophilic tendency. We use the same bonding formula as in Example 1, the objective being to verify the effectiveness of the water-repellent agent (Table 33).

[0227] [Tables33] Table 33 Humidity (H) Binders (%) PAM Water Repellent Agent Powdered Silicate Example 17 6.1 1 0.7 2

[0228] Table 33: Example 17

[0229] We mix for 4 minutes in a high-performance mixer and let it rest for 10 to 15 minutes in a covered bucket. We then place the mixture in the press at the same pressure and perform the following measurements (Table 34):

[0230] [Tables34] Table 34 Recycling Press (¾) Bursting Test Green Briquettes Bursting Test Dry Briquettes DCS (kg) Dry (105°C) After 1 month immersion Example 17 5.1 90 99.9 241 192

[0231] Table 34: Example 17

[0232] The results are consistent with those of Examples 1 and 6; the water-repellent agent did not show any adverse effects on the compaction and physical properties of the briquettes. Twenty briquettes were then completely immersed in containers filled with water and left for several days to several weeks. The results are shown in Table 35 below:

[0233] [Tables35] Table 35 Visual Appearance of Briquettes Time (days) 1 10 15 30 60 Example 17 Whole briquettes, no fines, clear water Whole briquettes, no fines, clear water Whole briquettes, no fines, clear water Whole briquettes, no fines, clear water Whole briquettes, no fines, clear water

[0234] Table 35: Example 17

[0235] These results show that our water-repellent agent makes the goats water-resistant for very long periods, thus allowing the transport of the briquettes over long distances.

[0236] The obvious advantages of this process are as follows: - Allows you to directly obtain the necessary resistances for agglomeration, drying and cooking. - Avoid difficult handling of lime. - Only marginally increase the impurities in the iron ore. Only silica from silicate is included. - A treatment volume much smaller than bentonite. - The treatment by drying and cooking is practically immediate, avoiding the 3 to 20 days of storage. - Financially enabling agglomeration at the level of metallurgical plants instead of buying more expensive agglomerated products. - To waterproof agglomerated products if necessary. For transport or storage.

[0237] This corresponds to a significant simplification of the process of agglomerating iron ore, metallurgical waste and other ores.

Claims

Claims

1. Use solely of polyacrylamide and sodium silicate for the cold agglomeration of iron ore, characterized in that the polymer acts as both a binder and an activator of the sodium silicate.

2. Use according to claim 1, characterized in that the polyacrylamide is in the form of a homopolymer or copolymer.

3. Use according to the preceding claim, characterized in that the polyacrylamide is chosen from anionic, cationic, amphoteric or non-ionic acrylamide copolymers depending on the variability of the ore to obtain suitable compositions and particle sizes determined by test.

4. A method for obtaining agglomerates of iron ore fines comprising the following steps: a) Mixing the polyacrylamide, the sodium silicate and the ore in a mixer under defined conditions; b) Adjusting the humidity for compaction in a range of 2 to 10%, preferably 3 to 8% of the mixture in the case of compaction; Carrying out the agglomeration using a device such as a briquette press (with tangent wheels). Drying the agglomerates obtained at a temperature of 100 to 250°C for 30 minutes to 2 hours. c) Adjusting the humidity for extrusion from 5 to 20%, preferably 9 to 18%. Carrying out the extrusion using a vacuum extruder. Drying the extrudates at a temperature of 100 to 250°C for 30 minutes to 2 hours.

5. A method according to claim 4, characterized in that no activator is added to treat the sodium silicate.

6. Method according to claim 4, characterized in that the silicate is in solid form in the form of powders, beads or microbeads or in liquid form by adjusting the quantity of water required for the mixture.

7. Method according to claim 4, characterized in that the following dosages are used: 0.01% to 2% by weight of polyacrylamide polymer relative to the total weight of the agglomerate formed and 0.1 to 5% by weight of active sodium silicate relative to the total weight of the agglomerate formed.

8. Method according to claim 4, characterized in that a hydrophobic polyacrylamide is added to reduce the sensitivity to humidity.

9. Briquettes obtained by the process according to claim 4, characterized in that they have a press recycling of less than 20%, a burst test of green briquettes greater than 80%, a burst resistance of dry briquettes greater than 99% and a DCS greater than 200 kg.

10. Briquettes obtained by the process according to claim 4, characterized in that they are of very high purity unlike bentonite as binder or lime as activator of sodium silicate.

11. Briquettes obtained by the process according to claim 4, characterized in that they are dried and cooked without aging unlike other activators.