EP0203854B1

EP0203854B1 - An improved process for agglomerating ore concentrate utilizing emulsions of polymer binders or dry polymer binders

Info

Publication number: EP0203854B1
Application number: EP86401064A
Authority: EP
Inventors: Meyer Robert Rosen; Lawrence Marlin; Gregory John Dorns-Tauder
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1985-05-21
Filing date: 1986-05-20
Publication date: 1992-08-05
Anticipated expiration: 2006-05-20
Also published as: IN167404B; EP0203854A2; EP0203854A3; AU598465B2; CA1332515C; AU5758386A; IN167405B; BR8602322A; IN171505B; SU1556544A3

Description

1. Field of the Invention

This invention relates generally to methods for agglomerating or pellitizing mineral ore concentrate. More specifically, this invention relates to methods for agglomerating or pelletizing mineral ore concentrate using a binder system comprising a polyacrylamide-based water soluble polymer binder systems in either water-in-oil emulsions or as dry powders in combination with a clay.
A separate patent application EP-A-0 203 855 (Application No. 86 401 065.7) of the same applicant deals with a method for agglomerating or pelletizing mineral on concentrate using the same polyacrylamide-based, water-soluble polymer in water-in-oil emulsions or as dry powder, but without the presence of a clay.

2. Description of the Prior Art

It is customary in the mining industry to agglomerate or pelletize finely ground mineral ore concentrate so as to further facilitate the handling and shipping of the ore. Mineral ore concentrates can include iron oxides, copper oxides, barytes, lead and zinc sulfides, and nickel sulfides. Agglomerates of coal dust and nonmetallic minerals used to make bricks or ceramics are also formed. Agglomerate forms can include pellets, briquettes, and sinters.
Methods of pelletizing mineral ore concentrate are frequently used in mining operations where the ore is a low grade iron ore. Examples of low grade iron ores are taconite, hematite, and magnetite. Numerous other low grade ores exist wherein pelletizing of the ground particles is beneficial to the handling and shipment of the mineral ore. After the mineral ore has been mined, it is frequently ground and screened to remove large particles which are recycled for further grinding. Typically, an ore is passed through a 100 mesh (0.149mm) screen. The screened mineral ore is known as a "concentrate".
For example, taconite mineral ore concentrate after grinding and screening has an average moisture content of between about 6 to about 11 percent. The moisture content of the mineral ore concentrate can be selectively altered. The moisture content affects the strength of the pellets that are formed later in the process.
After screening, the mineral ore concentrate is transported on a first conveyor means to a balling drum or another means for pelletizing mineral ore concentrate. Prior to entering the balling drum, a binding agent is applied or mixed into the mineral ore concentrate. Commingling the binding agent with the mineral ore concentrate occurs both on the conveyor means and in the means for pelletizing. The binding agents hold the mineral ore concentrate together as pellets until after firing.
Balling drums are apparatuses comprising long cylindrical drums which are inclined and rotated. The mineral ore concentrate is simultaneously rotated about the balling drum's circumference and rolled in a downward direction through the drum. In this manner the mineral ore concentrate is rolled and tumbled together to form roughly spherical-shaped pellets. As the pellets grow in size and weight they travel down the incline of the drum and pass through the exit of the drum at which point they are dropped onto a second conveyor means which transports them to a kiln for firing.
Inside the balling drum, different factors influence the mechanisms of union of the mineral ore concentrate. These factors include the moisture content of the ore, the shape and average size of the mineral ore particles, and the distribution of concentrate particles by size. Other properties of the mineral ore concentrate that influence the pelletizing operation include the mineral ore's wettability and chemical characteristics. The characteristics of the equipment used, such as its size and speed of rotation, can effect the efficiency of the pelletizing operation. The nature and quantity of the agglomerating or binding agent used in the concentrate is also a factor that determines part of the efficiency of the pelletizing operation.
The formation of agglomerates begins with the interfacial forces which have a cohesive effect between particles of mineral ore concentrate. These include capillary forces developed in liquid ridges between the particle surfaces. Numerous particles adhere to one another and form small pellets. The continued rolling of the small pellets within the balling drum causes more particles to come into contact with one another and adhere to each other by the capillary tension and compressive stress. These forces cause the union of particles in small pellets to grow in much the same manner as a snowball grows as it is rolled.
After the balling drum operation, the pellets are formed, but they are still wet. These pellets are commonly known as "green pellets" though taconite pellets, for example, are usually black in color. Green pellets usually have a density of about 130 lb/ft³ in sizes between about 1/2 inch and about 3/8 of an inch. The green pellets are transported to a kiln and heated in stages to an end temperature of approximately 2800°F. After heating, fired pellets are extremely hard and resist cracking upon being dropped and resist crushing when compressed.
Two standard tests are used to measure the strength of pellets whether the pellets are green pellets or fired pellets. These tests are the "drop" test and the "compression" test. The drop test requires dropping a random sampling of pellets a distance, usually about 18 inches or less, a number of times until the pellets crack. The number of drops to crack each pellet is recorded and averaged. Compression strength is measured by compressing or applying pressure to a random sampling of pellets until the pellets crumble. The pounds of force required to crush the pellets is recorded and averaged. These two tests are used to measure the strength of both wet and fired pellets. The drop and compressive test measurements are important because pellets, proceeding through the balling drum and subsequent conveyor belts, experience frequent drops as well as compressive forces from the weight of other pellets travelling on top of them.
The tumble strength of fired pellets can also be tested. The tumble strength test is designed to measure impact abrasion resistance of fired pellets. To test tumble strength equal weight samples of a selected size of pellets such as 1/2 inch pellets are rotated in a drum at a standard speed for equal amounts of time. The sample of fired pellets is then removed from the drum and sized on a 1/4 inch screen. The amount of small particles and fines that pass through the screen is compared between samples. High percentages of fines indicate that, during shipment, the pellets can be expected to deteriorate. A high rate of deterioration during shipment results in higher costs in smelting the pellets and poor furnace performance. Tumbled test results are also used to calculate a "Q-index". The Q-index was derived by the American Society for Testing and Materials (ASTM) and is described in the ASTM publication E279-65T. A high Q-index such as a value of about 94 or greater is an indication that the fired pellets are impact and abrasion resistant.
Thermal shock resistance is a factor which must be taken into consideration in any process for agglomerating mineral ore concentrate. Increases in a pellet's thermal shock resistance improve that pellet's ability to resist internal pressures created by the sudden evaporation of water when the pellet is heated in a kiln. If the pellet has numerous pores through which the water vapor can escape thermal shock resistance is improved. If the surface of the pellet is smooth and continuous without pores the pellet has an increased tendency to shatter upon rapid heating. This causes a concurrent increase in the amount of "fines" or coarse particles in the pelletized mineral ore. A binder which increases the pores formed in a pellet improves that pellet's ability to resist thermal shock.
Both the binder agent and pelletizing apparatus used to form pellets from a mineral ore concentrate can affect the pellet size distribution obtained during the pelletizing operation. It is desirable to form pellets having a diameter of approximately 1/2". It is also desirable to have a low variation between the diameter sizes of the pellets formed during a pelletizing operation. Pellets having a diameter of more than about 1/2" are less capable of being reduced in a furnace because of their increased surface area. Pellets having a diameter of about 1/2" are easily reduced in a furnace and result in fuel efficiency in the operation of the furnace as compared to reducing pellets of larger diameters. Pellets having a size distribution averaging less than 3/8" have an increased resistance to gas flow within a furnace. The increased resistance to gas flow decreased furnace productivity and adversely affects the fuel rate consumption of the furnace during operation. Desirable permeability of pellets to gas flow within a furnace is obtained when the pellets are large, evenly sized, and have an approximately even distribution of surface area. An even distribution of surface area is obtained with spherical pellets as compared to pellets that vary in their geometrical shapes. The optimum pellet size for furnace operations is between about 3/8" and about 1/2" diameter.
Bentonite (montmorillonite) is used as a binding agent in the pelletizing operations for clay mineral ore concentrate such as taconite ore concentrate. Bentonite produces a high strength pellet having an acceptable drop strength, compressive strength, and thermal shock resistance. Bentonite also provides moisture control in the formation of pellets made from mineral ore concentrate. Moisture control in the formation of pellets is important because the rate of growth of pellets increases with increased moisture. This increase in the rate of growth of the pellets is due to the increased efficiency of the agglomerate coalescence. Commercially available bentonite has a typical layer structure, a high particle surface area, and a specific affinity for water. Bentonite's ability to act as a binding agent in pelletizing operations for mineral ore concentrates is believed to result from the immobilization of water contained in a mineral ore concentrate. Bentonite is believed to immobilize water in the mineral ore concentrate by adsorbing free water into the surface layers of the bentonite clay. The addition of bentonite to a mineral ore concentrate decreases the water available for participating in the pelletization of the mineral ore concentrate which leads to a desirable retardation in the pellet growth process during the ball mill operation.
Bentonite has the disadvantage of increasing the silica content of the pellets that are formed. Bentonite is converted to silica when pellets containing bentonite are fired at about 2400°F or higher. Bentonite also imparts a significant concentration of alkalis to the pellets. Silica decreases the efficiency of blast furnace operations used in smelting of the ore. For this reason bentonite requires a higher energy expenditure than do organic binders in the blast furnace.
The presence of silica and alkalis in pellets of mineral ore concentrate impacts the hot metal quality and furnace operating efficiency during steel production. For these reasons rigid specifications exist for the presence of these contaminates in pellets of mineral ore concentrates and it is desirable to keep the presence of these contaminates in pellets as low as possible. Specifically, silica separates from the mineral ore in the cohesive zone to form slag. The addition of a 1% concentration of bentonite or 24.4 lbs./tonne provide an undesirable 0.85% silica or silicon dioxide (SiO₂) and alumina or aluminum oxide (Al₂O₃). This concentration of silica and alumina decreases the iron content of a pellet about 0.6%. Additionally, the quantity of slag is undesirably higher with this concentration of bentonite. An increased quantity of slag within the furnace decreases the productivity and fuel rate consumption of the furnace during the smelting operation. The increase in slag during the smelting operation resulting from the presence of bentonite in the mineral ore concentrate pellets also affects hot metal sulfur control. Other disadvantages of the presence of bentonite in pellets include an increased shipping expense because of the additional weight added to the pellets by bentonite, and an increase in the requirement for limestone and coke during the smelting operation. An increase in the limestone and coke used during the smelting operation reduces the amount of iron ore than can be converted to iron at a constant volume within a blast furnace.
The use of bentonite to form pellets of a mineral ore concentrate adds alkalis which are oxides of sodium, potassium, and zinc. These alkalis are reduced in the stack zone of a blast furnace, descend into the blast furnace and are vaporized and recirculated in the stack zone. The phenomenon occurs with alkalis because of the low boiling points of these metals. The presence of alkalis in the blast furnace causes both the pellets and coke to deteriorate and form scabs on the furnace wall which increase the fuel rate consumption and decrease the productivity of the smelting operation. The decrease of productivity of the smelting operation results from a decrease in the gas permeability of the pellets. When the scabs become too large to adhere to the walls of the blast furnace the scabs fall from the walls and cause a burning of tuyeres, a cooling of the hot metal, and a disruption of the smelting operation. The disruption of the smelting operation can result in quality control problems during the production of steel, as well as safety problems. An additional safety problem that occurs with the use of high concentrations of bentonite in the formation of pellets is an increased exposure to asbestos. Bentonite contains asbestos which can be carried through the process to plant effluent water.
Other binding agents have proven to be better binders than bentonite. These agents or "ore binding polymers" include organic binders such as poly(acrylamide), polymethacrylamide, carboxymethyl cellulose, hydroxyethyl cellulose, carboxyhydroxyethyl cellulose, poly(ethylene oxide), guar gum, and others. The use of organic binders in mineral ore pelletizing operations is desirable over the use of bentonite because organic binders do not increase the silica content of pellets and they improve the thermal shock resistance of the pellets. Organic binders burn during pellet firing operations and cause an increase in the porosity of the pellets. Firing conditions can be modified to improve the mechanical properties of fired pellets for organic binder systems.
Some organic binders used in mineral ore pelletizing operations are dissolved in an aqueous solution which is sprayed onto the mineral ore concentrate prior to entering the balling drums. This application of an aqueous solution increases the moisture content above the natural or inherent moisture content of the mineral ore concentrate which requires a greater energy expenditure during the firing operation of the pellets. This increased moisture content also causes an increased likelihood of shattering due to inadequate thermal shock resistance during firing. Pellet formation is improved with the use of organic binders, but the drop strength and compression strength of the pellet are frequently below that desired or achieved with bentonite.
Other binders commonly used for agglomerating mineral ore concentrate include a mixture of bentonite, clay and a soap, Portland cement, sodium silicate, and a mixture of an alkali salt of carboxymethylcellulose and an alkali metal salt. The agglomerates made from these binding agents frequently encounter the problems described above of insufficient pellet strength or insufficient porosity for the rapid release of steam during induration with heat. Additionally, these binding agents are usually applied to a mineral ore concentrate in aqueous carrier solutions or as dry powders. Aqueous carrier solutions increase the amount of energy required to fire the pellets and increase the incidence of pellet shattering due to inadequate thermal shock resistance.
U.S. Patent Number 3,893,847 to Derrick discloses a binder and method for agglomerating mineral ore concentrate. The binder used is a high molecular weight, substantially straight chain water soluble polymer. This polymer is used in an aqueous solution. The polymers disclosed as useful with the Derrick invention include copolymers of acrylamide as well as other polymers. The Derrick invention claims the use of polymers in an "aqueous" solution. The use of water as a carrier solution for the binding agents increases the moisture of the agglomerates or pellets that are formed. The higher moisture content increases the energy required to fire the pellets and can increase the rate of destruction of the pellets during induration due to the rapid release of steam through the agglomerate.
The use of organic polymers regardless of the molecular weight of the organic polymer or the form in which it is applied to a mineral ore concentrate can result in formation of pellets having dissimilar geometric shapes. The application of organic polymers in solution, emulsion, and dry powder forms in conjunction with inorganic salts such as sodium carbonate have resulted in the formation of non-spherical pellets. The formation of non-uniform, non-spherical pellets results in a greater variation in the surface area of the pellets which results in uneven reduction of the pellets in the furnace during the smelting operation and undesirably higher levels of fines being generated.
The non-uniform, non-spherical formation of pellets resulting from the use of organic polymer binding systems and inorganic salts results from an undesirable alteration in the pellet growth process due to the presence of the inorganic salt and its interaction with surface moisture. Moisture control is important because the rate of growth of pellets increases with increased moisture.
In two articles by Clum et al. entitled, "Possible Binders for Pelletizing of Magnetic Taconite Concentrates", Mining Engineering 30 (1) page 53, 1978, and "Substitutes For Western Bentonite In Magnetic Taconite Pellets", Society of Mining Engineers of AIME, preprint 76-B-11, 1976, pellets of magnetic concentrate with Wisconsin clay, hydroxyethyl celluose, poly(ethylene oxide), and a quar gum derivative. The binder systems used in the pelletizing operations of these articles are undesirable because the binder systems include four distinct components, and an undesirable high concentration of polymer. It is undesirable to use four distinct components in a binder system because of increased manufacturing difficulties, expenses of manufacturing, and decreased predictability in the performance of the binder system with various mineral ore concentrates. The decrease in predictability of the binder system with various mineral ore concentrates results from the increased complexity of the binder system resulting from the introduction of additional components to the pelletizing operation. The high concentration of polymer in the binder system used in these articles results in an increased cost that can make using these articles undesirable over other commercially available binder systems.
Organic polymers have been used as bentonite extenders wherein the polymers themselves do not significantly add to the strength of the resulting pellets. Additionally, various synthetic and natural resins and modified resins have been used in conjunction with bentonite to pelletize mineral ores. As disclosed in an article by Das Gupta et al., "Additives To Increase Bentonite Effectiveness In Iron Ore Pelletizing", Society of Mining Engineers of AIME, preprint 78-B-97 at page 1 the use of polymers with bentonite has resulted in less than desirable pellet (1) formation or (2) reducibility and behavior in a blast furnace. Additionally, this article reports undesirable economic factors resulting from high concentration of the resins required to effectively pelletize a mineral ore concentrate.
An article of R.L. SMYTHE, entitled "The use of synthetic polymer as a drying aid in pelletizing", has been published is the Aus. IMM Newcastle and District Branch, Pellets and Granules Symposium, Oct. 1974, pages 151-156.
This SMYTHE article emphasizes the necessity of using a solution of polyacrylamide polymer, for improving the drying of green pellets, when this polymer is normally in a dry powder form; and, in addition, it is disclosing the use of this specific polymer as a substitute for the bentonite as a drying aid in pelletizing.
At last US-A-3-860 414, published in 1975, is disclosing the use of a water soluble graft copolymer of acrylic acid and a polyhydroxy polymeric compound, optionally in combination with a bentonite, as binding agent in the agglomeration of finely divided iron ores, such as taconite.
This prior US patent is strictly limited to the use of a very specific organic binder which is not at all connected to a polyacrylamide-based polymer.
The industry is lacking a method for agglomerating mineral ore concentrate utilizing a two component low water polymer binder system, wherein moisture control is provided during pellet formation and wherein the pellets formed from the mineral ore concentrate have high mechanical strength properties.

SUMMARY OF THE INVENTION

The present invention is directed to a process for agglomerating a particulate material, which is preferably a mineral ore concentrate, and more preferably a taconite ore concentrate comprising commingling said particulate material with a binder system comprising an organic polymer and a clay and agglomerating said composition to form green pellets,
characterized in that the said binder system comprises two essential components, i.e. :

(i) a first component which is a binding amount of a polyacrylamide-based, water soluble polymer under the form of either a dry powder or a water-in-oil emulsion and,
(ii) a second component which is a clay, preferably bentonite, applied to said particulate material to obtain a dose of up to about 4.5 kg (10 pounds) per tonne of said particulate material.

Furthermore the present invention includes a process for manufacturing fired, agglomerated, mineral ore pellets comprising :

(a) commingling a binder system comprising an organic polymer and a clay onto a mineral ore concentrate to form a composition wherein said mineral ore concentrate has a sufficient moisture content to activate said polymer;
(b) agglomerating said composition to form green pellets by a means for pelletizing mineral ore concentrate and,
(c) firing said green pellets by a means for applying sufficient heat to indurate said pellets,
characterized in that said binder system comprises two essential components. i.e.
- (i) a first component which is a binding amount of a polyacrylamide-based, water soluble polymer under the form of a dry powder, and
- (ii) a second component which is bentonite applied to said mineral ore concentrate to obtain a concentration of up to about 4.5 kg (10 pounds) per tonne of said mineral ore concentrate.

Moreover the invention includes also a process for manufacturing fired, agglomerated mineral ore pellets comprising :

(a) commingling a binder system comprising an organic polymer and a clay onto a mineral ore concentrate to form a composition ;
(b) agglomerating said composition to form green pellets by a means for pelletizing mineral ore concentrate and,
(c) firing said green pellets by a means for applying sufficient heat to indurate said pellets,
characterized in that said binder system comprises two essential components, i.e. :
- (i) a first component which is a binding amount of a polyacrylamide-based, water soluble polymer under the form of a water-in-oil emulsion, and
- (ii) a second component which is bentonite, applied to said mineral ore concentrate to obtain a concentration of up to about 4.5 kg (10 pounds) per tonne of said mineral ore concentrate.

At last the invention includes a process for producing taconite ore pellets comprising:

(a) commingling a binder system comprising an organic polymer and a clay onto a taconite ore concentrate to form a composition ;
(b) pelletizing in a balling drum said composition to form green pellets, and,
(c) firing said green pellets for indurating them with heat,
characterized in that said binder system comprises two essential components, i.e. :
- (i) a first component which is a binding amount of a polyacrylamide-based, water soluble polymer under the form of a dry powder or a water-in-oil emulsion, and,
- (ii) a second component which is bentonite in a concentration of up to about 4.5 kg (10 pounds) of bentonite per tonne of said taconite ore concentrate.

DETAILED DESCRIPTION OF THE INVENTION

This invention is a method for agglomerating particulate material such as a mineral ore concentrate with a two component binder system. The first component of the binder system is one or more polyacrylamide-based water soluble, ore binding polymers in an amount sufficient to bind the particulate material. The polymers are applied to the particulate material in at least one of either a water-in-oil emulsion system or a dry powder system. The second component of the binder system is a clay which is desirably bentonite. The clay or bentonite is applied to the particulate material as a powder to obtain a concentration in the particulate material of up to about 4.5 kg (10 pounds) per tonne. The commingled polymers, clay, and particulate material composition can be in any sequence. The commingled composition then enters a standard means for pelletizing or a balling drum. The means for pelletizing further commingles the ingredients and forms wet or "green" pellets. The pellets are then transferred or conveyed to a furnace or kiln where they are indurated by heat at temperatures above about 1800°F and more preferably at about 2800°F. After induration, the pellets are ready for shipping or further processing in a smelting operation such as a blast furnace.
Suitable polyacrylamide-based polymers useful as the first component of the binder system of this invention can include water soluble homopolymers, copolymers, terpolymers, and tetrapolymers. In a water-in-oil emulsion system the selected polymer is produced by polymerizing its monomeric water-in-oil emulsion precursor. Suitable polymers can be anionic, amphoteric, or nonionic. In this invention synthetic and natural polymers of high or low molecular weights, as characterized by their intrinsic viscosities, can be used. This invention is not limited to polymers of a particular intrinsic viscosity.
Polyacrylamide-based polymers suitable for use with this invention must provide a binding activity to a particulate material and be capable of being used in at least one of two delivery systems. The delivery systems are either a water-in-oil emulsion system or a dry powder system. Binding polymers suitable for use in this invention are particularly desirable when they are of a high molecular weight. The particular molecular weight of a polymer is not limiting upon this invention.
Useful measurements of a polymer's average molecular weight are determined by either the polymer's intrinsic viscosity or reduced viscosity. In general, polymers of high intrinsic viscosity or high reduced viscosity have a high molecular weight. An intrinsic viscosity is a more accurate determination of a polymer's average molecular weight than is a reduced viscosity measurement. A polymer's ability to form pellets of mineral ore concentrate is increased as the polymer's intrinsic viscosity or reduced viscosity is increased. The most desirable polymers used in the process of this invention have an intrinsic viscosity of from about 0.5 to about 40, preferably from about 2 to about 35 and most preferably from about 4 to about 30 dl/g as measured in a one normal (N) aqueous sodium chloride solution at 25°C.
Polyacrylamide-based soluble polymers include, among others, those polymers which polymerize upon addition of vinyl or acrylic monomers in solution with a free radical. Typically, such polymers have ionic functional groups ouch as carboxyl, sulfamide, or quaternary ammonium groups. Suitable polymers can be derived from ethylenically unsaturated monomers including acrylamide, acrylic acid, and methylacrylamide. Alkali metal or ammonium salts of these polymers can also be useful.
Desirable polymers for use in this invention are preferably of the following general formula:

wherein R, R₁ and R₃ are independently hydrogen or methyl, R₂+ is an alkali metal ion, such as Na+ or K+, R₄ is either

(1) -OR₅ wherein R₅ is an alkyl group having up to 5 carbon atoms;
(2)
wherein R₆ is an alkyl group having up to 8 carbon atoms;
(3)
wherein R₇ is either methyl or ethyl;
(4) phenyl;
(5) substituted phenyl;
(6) -CN; or
(7)

Under certain conditions, the alkoxy or acyloxy groups in the polymer can be partially hydrolyzed to the corresponding alcohol group and yield a tetrapolymer of the following general formula:

wherein R, R₁, R₂+, R₃, a, b, and d are as previously defined, R₄ is -0R₅ or

wherein R₅ and R₇ are as defined previously, c is from about 0.2 to about 20 percent, and e is from about 0.1 to less than about 20 percent.
The preferred copolymers are of the following formula:

wherein R₂+ is an alkali metal ion, such as Na+ or K+, and f is from 5 to about 90, preferably from about 30 to about 60 percent, g is from 5 to about 90, preferably from about 30 to about 60 percent with the proviso that (f)+(g) equal 100 percent, and (d) is an integer of from about 1,000 to about 500,000.
The preferred terpolymers are of the following formula:

wherein R₂+ is Na+ or K+, R₇ is methyl, ethyl, or butyl and f is from about 5 to about 90, preferably from about 30 to about 60 percent, g is from about 5 to 90, preferably from about 30 to 60 percent, h is from about 0.2 to about 20, with the proviso that (f)+(g)+(h) equal 100 percent and d is as previously defined.
The preferred tetrapolymers are of the following formula:

wherein R₁, R₂+, R₃, R₇, f, g, h, d, and e are as previously defined.
Other desirable water soluble polymers for use with this invention include those derived from homopolymerization and interpolymerization of one or more of the following water soluble monomers: acrylamide and methacrylamide and derivatives including acrylamido- and methacrylamido monomers of the formula:

wherein R₁₃ is a hydrogen atom or a methyl group; wherein R₁₄ is a hydrogen atom, a methyl group or an ethyl group; wherein R₁₅ is a hydrogen atom, a methyl group, an ethyl group or -R₁₆-SO₃X, wherein R₁₆ is a divalent hydrocarbon group having from 1 to 13 carbon atoms, preferably an alkylene group having from 2 to 8 carbon atoms, a cycloalkylene group having from 6 to 8 carbon atoms, or phenylene, most preferably -C(CH₃)₂-CH₂-,-CH₂CH₂-,

-CH(CH₃)-CH₂-,

and

X is a monovalent cation such as a hydrogen atom, an alkali metal atom (e.g., sodium or potassium), an ammonium group, an organoammonium group of the formula (R₁₇) (R₁₈) (R₁₉) NH+ wherein R₁₇, R₁₈, R₁₉ are independently selected from a hydrogen atom, an alkyl group having from 1 to 18 carbon atoms (it may be necessary to control the number and length of long-chain alkyl groups to assure that the monomer is water soluble) such as 1 to 3 carbon atoms, an aryl group such as a phenyl or benzyl group, or a hydroxyalkyl group having from 1 to 3 carbon atoms such as triethanolamine, or mixtures thereof, and the like. Specific examples of water-soluble monomers which can be homopolymerized or interpolymerized and useful in the process of this invention are acrylamido- and methacrylamido- sulfonic acids and sulfonates such as 2-acrylamido-2-methylpropanesulfonic acid (available from the Lubrizol Corporation under its trade name, and hereinafter referred to as, AMPS), sodium AMPS, ammonium AMPS, organoammonium AMPS. These polymers can be effective binding agents for mineral ore concentrates in about the same concentrations or binding amounts used for the polyacrylamide based polymer binders.
These water soluble monomers can be interpolymerized with a minor amount (i.e., less than about 20 mole percent, preferably less than about 10 mole percent, based on the total monomers fed to the reaction) of one or more hydrophobic vinyl monomers. For example, vinyl monomers of the formula

wherein R₂₀ is a hydrogen atom or a methyl group and R₂₁ is

a halogen atom (e.g., chlorine), -O-R₂₃,

R₂₄ or

wherein R₂₅ is an alkyl group, an aryl group or an aralkyl group having from 1 to 18 carbon atoms, wherein R₂₂ is an alkyl group having from 1 to 8 carbon atoms, R₂₃ is an alkyl group having from 1 to 6 carbon atoms, preferably 2-4 carbon atoms, R₂₄ is a hydrogen atom, a methyl group, an ethyl group, or a halogen atom (e.g., chlorine), preferably a hydrogen atom or a methyl group, with the proviso that R₂₀ is preferably a hydrogen atom when R₂₂ is an alkyl group. Specific examples of suitable copolymerizable hydrophobic vinyl monomers are alkyl esters of acrylic and methacrylic acids such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, isobutyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, etc.; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, etc.; vinylbenzenes such as styrene, alpha-methyl styrene, vinyl toluene; vinyl ethers such as propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, methyl vinyl ether, ethyl vinyl ether, etc.; vinyl halides such as vinyl chloride, vinylidene chloride, etc.; and the like.
The preferred water soluble monomers of these water soluble polymers are acrylamide, AMPS and sodium AMPS. The preferred hydrophobic monomers are vinyl acetate, ethyl acrylate, styrene and methyl methacrylate.
Examples of suitable polymers for use with this invention in water-in-oil emulsions are listed in Table 1. This table provides a representative listing of suitable polymers for use in the water-in-oil emulsions, but does not encompass every suitable polymer or limit the polymers that can be used with this invention.
A second class of polymers includes those polymers used with this invention in dry powder form. These polymers must be water soluble, but do not necessarily lend themselves to the formation of water-in-oil emulsions. Typically, polymers which form water-in-oil emulsions are also useful with the invented method as dry powder. Table 2 represents listings of polymers which are desirable for use with this invention in powder delivery systems. The powders listed in Table 2 do not encompass all polymers which can be used as powders in this invention.
The second component of the binder system of this invention is a material that can be mixed with the particulate material prior to agglomeration which partially dries the resulting green pellets by adsorbing and stabilizing free water or moisture present in the particulate material. Desirably, the second component of the binder system of this invention is a clay. Suitable clays include Wisconsin Clay and most desirably Bentonite Clay. When the second component of the binder system of this invention is clay it is most desirable to use a pure clay. With the increasing scarcity of high quality moisture absorbing clays such as bentonite, clay compositions wherein, for example, bentonite and an extender or other additive is present can be effective for use as the second component in the binder system of this invention.
When the second component of the binder system of this invention is a clay and particularly bentonite, some binding action of the particulate material is provided by the clay. In the doses or concentrations of clay to particulate material used with this invention, the binding effect of the clay is negligible.
Another component of this invention is the invertible water-in-oil emulsion. The invertible water-in-oil emulsion system is a suspension of droplets comprised of both water soluble, high molecular weight polymers and water in a hydrophobic substance. Examples of suitable emulsion systems and methods to form suitable emulsions are found in U.S. Patent Number 4,485,209 to Fan et al., U.S. Patent Number 4,452,940 to Rosen et al., and the parent application U.S. Serial Number 736,237 of this invention each of which are herein incorporated by reference.
Desirable hydrophobic liquids used in these emulsion systems are isoparaffinic hydrocarbons. A suitable isoparaffinic hydrocarbon is that sold by the Exxon Corporation known as Isopar® M. Other suitable hydrophobic liquids for use as the external phase in an emulsion system include benzene, xylene, toluene, mineral oils, kerosenes, petroleum, paraffinic hydrocarbons, and mixtures of these.
In the most desirable embodiments of this invention, which include a polymer binding agent in a water-in-oil emulsion, two surfactants are used to form the emulsion. A first surfactant is used to form the water-in-oil emulsion system. After the water-in-oil emulsion system is formed, a second surfactant is added. The second surfactant is a water soluble inverting surfactant which, is believed, permits the inversion of the water-in-oil emulsion to an oil-in-water emulsion upon contact with the inherent or added moisture present in the mineral ore concentrate. Upon inversion of the water-in-oil emulsion the polymer is forced out of the internal aqueous phase and made available to the surface of the mineral ore concentrate. This release of the polymer onto the surface of the mineral ore concentrate allows for rapid commingling of the polymer with the mineral ore concentrate. Emulsions that do not contain inverting surfactants can be used with this invention.
The surfactants suitable for use in forming emulsions of this invention are usually oil-soluble having a Hydrophile-Lipophile Balance (HLB) value of from about 1 to about 10 and preferably from about 2 to about 6. These surfactants are normally referred to as water-in-oil type surfactants. Suitable surfactants include the acid esters such as sorbitan monolaurate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate, mono and diglycerides, such as mono and diglycerides obtained from the glycerolysis of edible fats, polyoxyethylenated fatty acid esters, such as polyoxyethylenated (4) sorbitan monosterate, polyoxyethylenated linear alcohol, such as Tergitol 15-S-3 and Tergitol-25-L-3 supplied by the Union Carbide Corporation, polyoxyethylene sorbitol esters, such as polyoxyethylene sorbital beeswax derivative, polyoxyethylenated alcohols such as polyoxyethylenated (2) cetyl ether, and the like.
Water-soluble inverting surfactants which can be used include polyoxyethylene alkyl phenol, polyoxyethylene (10 mole) cetyl ether, polyoxyethylene alkyl-aryl ether, quaternary ammonium derivatives, potassium oleate, N-cetyl N-ethyl morpholinium ethosulfate, sodium lauryl sulfate, condensation products of higher fatty alcohols with ethylene oxide, such as the reaction product of oleyl alcohol with 10 ethylene oxide units; condensation products of alkylphenols and ethylene oxide, such as the reaction products of isooctylphenol with 12 ethylene oxide units; condensation products of higher fatty acid amines with five, or more, ethylene oxide units; ethylene oxide condensation products of polyhydric alcohol partial higher fatty esters, and their inner anhydrides (mannitol-anhydride, called Mannitan, and sorbitol-anhydride, called Sorbitan). The preferred surfactants are ethoxylated nonyl phenols, ethoxylated nonyl phenol formaldehyde resins, and the like.
The inverting surfactant is used in amounts of from about 0.1 to about 20, preferably from about 1 to about 10 parts per one hundred parts of the polymer.
The mixture of both the aqueous phase and the oil phase of the emulsions used in this invention can contain about 20 to about 50 and preferably from about 22 to about 42 percent weight of the hydrophobic liquid and the hydrophobic monomers, based upon the total weight of the composition.
The aqueous solution used to form the emulsion systems of this invention can contain a mixture of water soluble monomers. These monomers have a water solubility of at least 5 weight percent and include acrylamide, methacrylamide, acrylic acid, methacrylic acid, and their alkali metal salts, aminoalkyl acrylate, aminoalkyl methacrylate, dialkylaminoalkyl acrylate, dialkylamino methacrylate and their quaternized salts with dimethyl sulfate or methyl chloride, vinyl benzyl dimethyl ammonium chloride, alkali metal and ammonium salts of 2-sulfoethylacrylate, alkali metal and ammonium salts of vinyl benzyl sulfonates, maleic anhydride, 2-acrylamide-2-methylpropanesulfonic acid, and the like. The preferred monomers are acrylamide, acrylic acid, and sodium salt of 2-acrylamido-2-methylpropanesulfonic acid.
If acrylic acid is used as a monomer it is reacted with a base, preferably with an equivalent amount of base, such as sodium hydroxide, so that the sodium acrylate solution has a pH of from about 5.0 to about 10.0, preferably from about 6.5 to about 8.5, depending on the type and amount of base employed. This solution is combined with another water soluble monomer, such as acrylamide, and then with water to form the aqueous phase.
Hydrophobic monomers which can be useful in forming the emulsion systems of this invention include one or more of vinyl esters such as vinyl acetate, alkyl acrylates such as ethylacrylate, alkyl methacrylates such as methacrylate, vinyl ethers such as butylvinyl ether, acrylonitrile, styrene and its derivatives such as alpha-methylstryrene, N-vinyl carbazole, and the like.
Appropriate reactors and catalysts are also used with this invention. These compounds can vary. Examples of suitable reactors and catalysts can be found in the Fan and Rosen patents identified above.
Emulsions used in this invention are made by any suitable method. A desirable method for making emulsions is disclosed in U.S. Patent Number 4,485,209 to Fan. This invention is not limited to a particular emulsion or method for producing an emulsion.
An advantage to the use of water-in-oil emulsions in the formation of pellets is that the amount of water added to the mineral ore concentrate is greatly reduced from that required to deliver polymers in aqueous solutions, thus resulting in an energy savings upon firing of the pellets. Also, the hydrophobic liquid or oil in the inverted water-in-oil emulsion system is consumed during the firing operation. The burn out of the oil droplets from the interior of the pellets increases the porosity of the pellets in much the same manner as does the burning of the organic binder or polymer from the interior of the pellets. This increase in porosity is believed to improve the release of water vapor from the pellets and decrease the occurrence of thermal shock upon firing of the pellets.
An additional benefit realized by the use of a water-in-oil emulsion system to deliver a polymer binder to mineral ore concentrate in pelletizing operations is a decrease in the amount of contact time required for sufficient commingling of the polymer binder with the mineral ore concentrate. The contact time of a polymer after the emulsion is sprayed onto the mineral ore concentrate need only be sufficient to allow activation of the polymer on the surface of the mineral ore concentrate. The amount of time can vary depending upon the emulsion system used and the concentration of the polymer binder within the emulsion system as well as the total amount of polymer binder sprayed upon the mineral ore concentrate. In desirable embodiments of this invention, sufficient time for commingling of the polymer binder system into the mineral ore concentrate occur by spraying the water-in-oil emulsion onto the mineral ore concentrate just upstream of where the concentrate enters the bailing drum.
Application of a water-in-oil emulsion at the mineral ore concentrate treatment site can be accomplished by applying the emulsion to the mineral ore concentrate through any conventional spraying apparatus. The clay is sprinkled from a vibrating hopper or other dispersing means onto the mineral ore concentrate and the composition is conveyed towards the balling drum. The activation of the polymers onto the surface of the mineral ore concentrate is rapid, and because the polymers are evenly spread or commingled throughout the mineral ore concentrate, the time required for sufficient commingling to initiate pellet formation is about one minute or less.
This invention also includes the application of binding polymer systems to mineral ore concentrate that are dry powders. In these embodiments the dry powdered polymers are mixed together with the powdered clay or added separately. The resulting powder composition is sprinkled onto the mineral ore concentrate as the concentrate is conveyed towards the balling drum. The vibration of the conveyor means and the action of the balling drum commingles the powders into the mineral ore concentrate. Upon sufficient contact time with the moisture in the mineral ore concentrate, the polymers are adsorbed onto the surface of the concentrate. Suitable contact time can be essentially instantaneous, but often is between about 1 minute to 3 hours or more. Further commingling occurs in the mixing within the bailing drum. The use of the dry powder polymer embodiments of this invention eliminates the need for emulsion spraying equipment. The useful range of the concentration of the polymer on an active basis is between about 0.001 percent to about 0.3 percent based on weight of bone dry concentrate. A desirable range is between about 0.001 percent and about 0.1 percent. These ranges are applicable for both dry and emulsified applications of polymer binder systems. The most desirable concentration of the polymer when applied to a wet mineral ore concentrate is between about 0.01 and about 2.0 pounds of polymer per tonne of mineral ore concentrate. A wet mineral or concentrate has between about 8 and about 11 percent water.
The invention is further understood from the examples below, but is not to be limited to the examples. The numbered examples represent the present invention. The lettered examples do not represent this invention and are for comparison purposes. Temperatures given are in °C unless otherwise stated. The following designations used in the examples and elsewhere herein have the following meanings:

LABORATORY EXPERIMENTAL PROCEDURE

In these examples taconite pelletizing consists of a two step procedure. Initially, seed balls are prepared from the taconite ore using bentonite clay as a binder. These seed balls are passed through screens to obtain seed balls or a size that pass through a #4 U.S. mesh screen having a 0.187 inch opening, but not through a #6 U.S. mesh screen having a 0.132 inch opening. The seed balls are then used with additional concentrate and the binder of interest to prepare the larger green pellets. Finished green pellets are sieved to be in a size range between 13.2mm to 12.5mm. This can be accomplished by using USA Sieve Series ASTM-E-11-70. Following sieving, the green pellets are tested for wet crushing strength and wet dropping strength. Additional green pellets are dried (not fired) and tested for both dry crushing and dry dropping strength. For the examples cited, all testing was done with either wet or dry green pellets.
Seed ball formation in these examples is begun with a sample of 900 grams (bone dry weight) of taconite concentrate containing between 8 to 11% moisture. The concentrate is sieved through a 9, 10, or 12 mesh screen and spread evenly over an oil cloth. Next 7.0 grams of bentonite clay is spread evenly over the top of the concentrate and mixed until homogenous. The mixture is incrementally added to a revolving rubber drum having approximately a 16 inch diameter and a 6 inch cross section. The drum is rotated at 64 revolutions per minute. Humidity is not controlled in these examples. Just prior to addition of concentrate, the inside of the drum is wet with water from a spray bottle. While rolling, several handfulls of the bentonite-concentrate mixture is added to the drum. Distilled water is added when the forming agglomerates begin to develop a dull appearance. As seed pellets are formed, they are screened to separate and obtain pellets which pass through a #4 U.S. mesh screen, but not through a #6 U.S. mesh screen. Captured fines are re-added to the balling drum and oversized seeds are rejected. The procedure of readding captured fines is repeated several times until sufficient seed pellets of the desired size have been produced. The seed pellets are then rolled for one minute to finish the surface. Formed seed pellets can be placed in a sealed container containing a damp cloth so as to retard dehydration of the pellets.
Green pellet formation in these examples is begun with a sample of 1800 grams (bone dry weight) of mineral ore containing between 8 to 11% moisture. The concentrate is added into a 12 inch diameter Cincinnati Muller and mixed for 1.0 minute. Thereafter, an amount of binder to be used in the example is uniformly distributed over the surface of the concentrate. In examples using emulsion polymers, the emulsified polymers are uniformly delivered dropwise from a syringe. For those examples which employ powdered polymers, the powder is dry blended with the clay or added separately and the resulting mixture is then uniformly sprinkled over the concentrate in the muller. The muller is then turned on for three minutes to mix the binder with the concentrate. The uniform mixture is then screened through an #8 U.S. mesh screen.
After moistening the inside of the rotating balling drum of tire, about 40 grams of seed pellets are added to the tire. Then the concentrate and binder mixture is incrementally fed into the tire over a period of six minutes with intermittent use of distilled water spray. During the initial portion of this process, small amounts of the concentrate and binder mixture are added each time the surface of the pellets appear shiny. Typically, the latter portion of the six minute rotating period requires an increased amount of the concentrate and binder mixture when compared to the initial part of the rotating period. Water spray is applied each time the surface of the pellets takes on a dull appearance. After the six minute rotating period is complete, the bailing drum is rotated one additional minute to "finish off" the pellet surface. No water spray is used during the final one minute period. Following completion of this procedure, the green pellets are screened for testing purposes to a size between 13.2mm and 12.5 mm.
Compression testing in these examples is performed by using a Chatillon Spring Tester of a 25 pound range (Model LTCM - Serial No. 567). Twenty green pellets are crushed in the tester within 30 minutes of pellet completion at a loading rate of 0.1 inches per second. The pounds of force required to crush each pellet is averaged for the twenty pellets and is herein called the wet crush strength. An additional twenty pellets are dried for one hour at 350°F. While these pellets are still warm to the touch, the crushing procedure is repeated to obtain the dry crush strength average measured in pounds per square inch (psi).
Drop testing in these examples is performed with twenty green pellets which are tested within 30 minutes of their formation. These pellets are dropped one at a time from a height of 18 inches onto a steel plate. The number of drops to obtain pellet failure is recorded. Pellet failure is determined when a crack in a pellet of approximately a 0.7 mm or greater occurs. The average for twenty wet pellet drops is reported. Twenty additional green pellets are dried by the procedure set out for the compression test and then each is dropped from a 3 inch height. The average number of drops to obtain pellet failure for twenty pellets is determined and recorded.
The tumble test measures impact and abrasion resistance of fired pellets. In this test twenty-five pounds of +1/2 inch pellets are rotated in a drum at twenty-five revolutions per minute for eight minutes. This sample of pellets is then removed and sized at 1/4 inch. A high percentage of fines after screening indicates that the pellets will experience undesirably high frequencies of deterioration during shipment. The results or the tumble test are used to calculate the Q-index.
The definition of acceptable or target mechanical properties is defined in these examples, within limits of experimental error, by comparing the critical green pellet property as measured by the 18 inch green drop test. Desirable pellets have an 18 inch green drop test value at a minimum of about 7 plus or minus about 1. Desirable pellets are also spherical and have a moist or dry surface. Undesirable pellets have a wet surface. Surface appearance descriptors are shown below.

DRY:: Smooth, dull appearing. This result is acceptable.
MOIST:: Moderately rough, shiny surface indicating a continuous film of moisture. This result is acceptable.
WET:: Irregular shiny surface with shallow peaks and valleys. Sticky to the touch and material is easily transferred to the hand. This result is undesirable.

Pellets having wet drop numbers above about 7.0 and wet crush numbers above about 3.0 are useful to the industry. Pellets having dry drop numbers greater than about 2.0 and dry crush numbers above about 4 are acceptable to the industry. Comparisons of pellet mechanical properties for different binders need to be made at approximately equal pellet moisture contents. Wet pellet properties are important because wet pellets are transported by conveyors and are dropped from one conveyor to another during their movement. Dry properties are important because in kiln operations pellets can be stacked 6 to 7 inches high or more. The pellets at the bottom of such a pile must be strong enough so as not to be crushed by the weight of the pellets on top of them. Dry pellets are also conveyed and must resist breakage upon dropping.
Unless otherwise stated in the following examples, the term, water-in-oil emulsion, refers to a water-in-oil emulsion containing an inverting surfactant. In these emulsions the oil phase is Isopar®M. The polymer binding agent PAM/NaA/VA is in a mole ratio of 47.5/47.6/4.9. The mineral ore concentrate is a taconite ore concentrate.

EXAMPLE A

This example illustrates plant trial data wherein bentonite was used alone to form green pellets from taconite ore concentrate. The bentonite was used with the taconite ore concentrate at a concentration of 15 pounds per tonne. The data of this example is provided for comparative purposes and is the control data for comparison with the examples of the invention. The results of this example are presented in Table 3. TABLE 3

System Property Bentonite Control 15 lb/Tonne

18" Green Drop No. 8.3

Wet Crush, psi 2.12

Dry Crush, psi 9.25

Surface Appearance dry

Pellet Shape spherical

EXAMPLES B AND C AND EXAMPLES 1 AND 2

The experimental procedure described above was used for these examples with the exception that the pellets were produced in a full size commercial bailing drum facility. In these examples green pellets of taconite ore concentrate are formed. The samples of green pellets are formed with a PAM/NaA/VA binding agent in a water-in-oil emulsion. The mole percent of PAM/NaA/VA is 47.5/47.6/4.9. The oil used in the external phase was Isopar®M. The intrinsic viscosity of the polymer binding agent was 23 dl/g.
The results of the examples are presented in table 4.
These examples demonstrate that the use of a PAM/NaA/VA emulsion along with low doses of bentonite produce a taconite binder system that provides improved green pellets when compared to the polymer binder agent used alone or with Na₂CO₃. These examples demonstrate that by terminating the use of Na₂CO₃ with a polymer binding agent and substituting a small amount of bentonite the pellets formed become spherical and have an acceptably moist appearing surface. Example 1 demonstrates that the 18 inch green drop test values were equivalent (using a plus or minus 1 for experimental error) to the bentonite control of Example A.

EXAMPLES D AND E AND EXAMPLES 3 AND 4

The experimental procedure described for Example 1 was also used to produce the pellets of these examples. The results of these examples are presented in Table 5.
These examples are similar to those of Examples B and C and Examples 2 and 3. These examples use a higher concentration of the polymer binding agent. The resulting green pellets of these examples are more desirable than those obtained in Examples B and C and Examples 2 and 3.
The pellets obtained from Examples 3 and 4 are markedly superior to those of Example A.
The value of the green drop test for Example 3 doubled when compared to Example 1. This increase in the green drop test value is the result of increasing the polymer binding agent from 0.6 to 0.8 pounds of emulsion per tonne.

EXAMPLE F AND EXAMPLE 5

The experimental procedure described for Example 1 was used in this example. The dose of the PAM/NaA/VA to the taconite ore concentrate is 0.6 pounds of emulsion per tonne and 4 pounds of bentonite per tonne. A full size balling drum was uniformly operated for eight hours to provide the green pellets of Example 5. The results obtained for the green pellets are presented in Table 6.
The fired pellet data for the eight hour run of the balling drum in this example is not obtainable. This data is not available because the steel sample baskets melted during the test. Fired pellet data was for Example 5 obtained based on a total plant output (6 balling drums) and comprised pellets made with the PAM/NaA/VA polymer binding agent and bentonite system. Data for a bentonite system is provided for comparative purposes (Example F). The data represents results obtained from an 8 hour run using only bentonite followed by a 16 hour run using a polymer binder system of this invention followed by a final 8 hour run using only bentonite.

All Q-index values were essentially the same and acceptable. The fired pellet data is presented in Table 7.

TABLE 7

	Q-Index	Binder	% -200 Mesh	Fired Compression psi
8 Hours	93.6	Bentonite 17 lb/tonne	4.5	421
16 Hours	93.5		4.5	433
16 Hours	93.2	PAM/NaA/VA and Bentonite	4.3	448
8 Hours	93.6	Bentonite 17 lb/tonne	5.3	419

EXAMPLE 6

The experimental procedure described for Example 1 was used to prepare and test the samples of green pellets for this example. This example was conducted using a full size commercial bailing drum. The system was allowed to equilibrate for about 30 minutes prior to taking data and making the next incremental change of the bentonite dose. The polymer binder agent used in this example was PAM/NaA/VA at a dose of 0.6 pounds per tonne of taconite ore concentrate. Test number 1 of this example contained no bentonite and the data is presented for comparative purposes only. The data of the green pellets obtained in this example are presented in Table 8.

TABLE 8

Test No.	lb. Bentonite/Tonne	18"Green Drop No.	Dry Crush psi	Surface Appearance	Pellet Shape
1	0	6.8	1.35	wet	spherical
2	1	7.5	1.70	wet-moist	spherical
3	2	7.8	2.38	wet-moist	spherical
4	3	8.3	2.08	moist	spherical
5	4	7.4	2.20	moist	spherical
6	5	9.9	2.63	moist	spherical
7	6	11.3	2.82	moist	spherical

This example demonstrates the relative surface drying effect of various low doses of bentonite in green pellets. The tests were conducted using 6 pounds of bentonite per tonne of taconite ore concentrate provided the best 18 inch drop test and surface appearance.

EXAMPLE 7

The experimental procedure described for Example 6 was used to prepare and test the green pellets of this example. The polymer binding agent of this example was a PAM/NaA/VA polymer at a dose of 0.8 pounds per tonne of taconite ore concentrate. The results of the green pellets obtained from this example are presented in Table 9 . As in Example 6, test No. 1 of this example contained no bentonite and the data is presented for comparative purposes only.
This example demonstrates that increasing concentrations of bentonite with a polymer binding agent improve green pellet physical characteristics. The green pellets obtained with a bentonite dose of 6 pounds per tonne provided the best results of this example and produced an excellent pellet.

EXAMPLES G, H AND I AND EXAMPLE 8

The laboratory experimental procedure described above was used to prepare and test the samples of green pellets of taconite ore concentrate of these examples. The polymer binder in Example 8 was applied as an emulsion. The results of the tests on green pellets obtained in these examples are presented in Table 10.
These examples demonstrate the appearance of an undesirable wet surface with little or no amounts of bentonite. The absence of bentonite produces a wet surface. The presence of small amounts of bentonite eliminates the occurance of wet surfaces.
The comparison of these examples also demonstrates that the use of a PAM/NaA/VA polymer binding agent with bentonite improves the green drop data for the resulting pellets.
These examples demonstrate a significant increase in the 18 inch green drop and dry crush tests experienced when the bentonite dose is increased.

EXAMPLE 9

The laboratory experimental procedure described above was used to prepare and test the green pellets of taconite ore concentrate of this example. This example uses a PAM/NaA/VA polymer binding agent applied in an emulsion containing 29.5 percent active polymer. All samples apply bentonite in a dose of 4 pounds per tonne of taconite ore concentrate. A test wherein no polymer agent was utilized is provided for comparative purposes only. The results of data obtained on the green pellets of this example are presented in Table 11.
This example demonstrates the significant increase in green drop test values obtained by increasing the dose of the polymer binding agent in a polymer binder system including small doses of bentonite. Also, of note is that the surface wetness of the green pellets is reduced and eliminated as the concentration of the polymer is increased. Even though increased concentrations of the polymer binding agent provide additional dryness to the resulting green pellets it is less expensive to obtain equivalent degrees of dryness by the addition of bentonite than with the use of additional polymer.

EXAMPLE 10

The laboratory experimental procedure described above was used to prepare and test the green pellets of taconite ore concentrate of this example. This example uses polymer binding agents made of poly(acrylamide) and sodium acrylate copolymers in a water-in-oil emulsion. Each of the tests of this example used a bentonite dose of 4 pounds per tonne and 1 pound of polymer per tonne of taconite ore concentrate. The tests wherein no polymer binding agent or no bentonite were used are provided for comparative purposes only. The results of data obtained on the green pellets obtained from this example are presented in Table 12.

TABLE 12

Mole % AM/NaA	Dose lb/tonne	18" Green Drop No.	Surface Appearance
85/15	1.0	8.1	moist
76/24	1.0	6.7	moist
59/41	1.0	6.8	moist
59/41	0.6	4.2	moist
No Polymer Control		4.0	wet
No Bentonite Control	3.1	wet

This example demonstrates that polymer binding agents of poly(acrylamide) and sodium acrylate are effective in the polymer binding system of this invention.

EXAMPLE 11

The laboratory experimental procedure described above was used to prepare and test the sample of green pellets of taconite ore concentrate of this example. In this example a powdered nonionic poly(acrylamide) binding agent was used. This binding agent is commercially available under the trade name BEN EX®. Bentonite was used in this example in concentrations of 4 pounds per tonne of taconite ore concentrate. The results of data obtained on the green pellets obtained in this example are presented in Table 13. As in some of the previous examples, the test including no polymer (the results summarized in the first column of the results of Table 13) is presented for comparison purposes only.
This example demonstrates that a powdered polymer binding agent is operable in the binder system of this invention. This example also demonstrates that doses of the polymer binding agent as high as 0.6 pound per tonne of to taconite ore concentrate are necessary with this polymer binding agent.

Example 12

The laboratory experimental procedure described above was used to prepare and test the samples of green pellets of taconite ore concentrate of this example. In this example a powdered copolymer of poly(acrylamide) and sodium acrylate is used as the polymer binding agent. This polymer binding agent is commercially available as SUPERFLOC 206. This example uses bentonite in a dose of 4 pounds per tonne of taconite ore concentrate. The test wherein no polymer binding agent was used is provided for comparison purposes only. The results of data obtained on the green pellets obtained from this example are presented in Table 14 .

TABLE 14

Pellet Properties	Pounds Polymer Per Tonne
	Control 0.0	0.24
18" Green Drop No.	4.0	8.1
Wet Crush, psi	4.7	3.5
Dry Drop No.	3.0	2.5
Dry Crush, psi	5.6	6.3
Surface Appearance	wet	moist
Pellet Shape	spherical	spherical
% Moisture	8.1	9.3
Initial Concentrate Moisture	9.3%	9.8%

This example demonstrates that a powdered copolymer of poly(acrylamide) and sodium acrylate is operable in the polymer binding system in this invention.

EXAMPLE 13

The laboratory experimental procedure described above was used to prepare and test the samples of green pellet of taconite ore concentrate of this example. This example uses polymer binding agents of acrylamide with a bentonite dose of 4 pounds per tonne. In each test the polymer binding agent is applied in a water-in-oil emulsion. The acrylamide polymer binding agents of this example comprise either all acrylamide monomers or copolymers of poly(acrylamide) and sodium acrylate. The results of data obtained on the green pellets obtained from this example are presented in Table 15.
This example demonstrates that various poly(acrylamide) based polymers are suitable for use in the polymer binding system of this invention. This example also demonstrates that increasing the concentration of the polymer binding agent in the binding system of this invention improves the physical characteristics of the green pellets obtained.

EXAMPLE J

The laboratory experimental procedure described above was used to prepare and test the sample green pellets of taconite ore concentrate of this example. The polymer binding agents used in this example are copolymers of poly(acrylamide) and dimethyl diallyl ammonium chloride (DMDAC) in a water-in-oil emulsion. The polymer binding system of this example contains a bentonite dose of 4 pounds per tonne of taconite ore concentrate. The results of data obtained on the green pellets obtained from this example are presented in Table 16.

TABLE 16

Polymer	Dose lb/tonne	18" Green Drop No.	Surface Appearance	% Moisture
50/50 PAM/DMDAC	0.8	4.2	moist	---
70/30 PAM/DMDAC	0.8	4.1	moist	---
	2.0	4.1	moist
Control	0.0	4.1	wet/moist	9.5

The example demonstrates that the two cationic copolymers tested, which were 30% active polymers, did not function within the polymer binder system of this invention at the doses tested.

Claims

A process for agglomerating a particulate material, which is preferably a mineral ore concentrate, and more preferably a taconite ore concentrate comprising commingling said particulate material with a binder system comprising an organic polymer and a clay and agglomerating said composition to form green pellets,
characterized in that the said binder system comprises two essential components, i.e. :
(i) a first component which is a binding amount of a polyacrylamide-based, water soluble polymer under the form of either a dry powder or a water-in-oil emulsion and,

(ii) a second component which is a clay, preferably bentonite, applied to said particulate material to obtain a dose of up to about 4.5 kg (10 pounds) per tonne of said particulate material.
A process for manufacturing fired, agglomerated, mineral ore pellets comprising :
(a) commingling a binder system comprising an organic polymer and a clay onto a mineral ore concentrate to form a composition wherein said mineral ore concentrate has a sufficient moisture content to activate said polymer;

(b) agglomerating said composition to form green pellets by a means for pelletizing mineral ore concentrate and,

(c) firing said green pellets by a means for applying sufficient heat to indurate said pellets,
characterized in that said binder system comprises two essential components, i.e.
(i) a first component which is a binding amount of a polyacrylamide-based, water soluble polymer under the form of a dry powder, and

(ii) a second component which is bentonite applied to said mineral ore concentrate to obtain a concentration of up to about 4.5 kg (10 pounds) per tonne of said mineral ore concentrate.
A process for manufacturing fired, agglomerated mineral ore pellets comprising :
(a) commingling a binder system comprising an organic polymer and a clay onto a mineral ore concentrate to form a composition ;

(b) agglomerating said composition to form green pellets by a means for pelletizing mineral ore concentrate and,

(c) firing said green pellets by a means for applying sufficient heat to indurate said pellets,
characterized in that said binder system comprises two essential components, i.e. :
(i) a first component which is a binding amount of a polyacrylamide-based, water soluble polymer under the form of a water-in-oil emulsion, and

(ii) a second component which is bentonite, applied to said mineral ore concentrate to obtain a concentration of up to about 4.5 kg (10 pounds) per tonne of said mineral ore concentrate.
A process for producing taconite ore pellets comprising:
(a) commingling a binder system comprising an organic polymer and a clay onto a taconite ore concentrate to form a composition ;

(b) pelletizing in a balling drum said composition to form green pellets, and,

(c) firing said green pellets for indurating them with heat,
characterized in that said binder system comprises two essential components, i.e. :
(i) a first component which is a binding amount of a polyacrylamide-based, water soluble polymer under the form of a dry powder or a water-in-oil emulsion, and,

(ii) a second component which is bentonite in a concentration of up to about 4.5 kg (10 pounds) of bentonite per tonne of said taconite ore concentrate.
The process of anyone of claims 1 to 4, wherein said polymers are of the following general formula:
wherein R, R₁ and R₃ are indepently hydrogen or methyl, R₂+ is an alkali metal ion, such as Na+ or K+, R₄ is either
(1) -OR₅ wherein R₅ is an alkyl group having up to 5 carbon atoms ;

(2)
wherein R₆ is an alkyl group having up to 8 carbon atoms ;

(3)
wherein R₇ is either methyl or ethyl ;

(4) phenyl ;

(5) substituted phenyl ;

(6) -CN ; or

(7)

and wherein (a) is from about 5 to about 90, preferably from about 30 to about 60 percent, (b) is from 0 to about 90, preferably from about 30 to about 60 percent ; (c) is from about 0 to about 20 percent with the proviso that (a)+ (b) + (c) equal 100 percent, and (d) is an integer of from about 1,000 to about 500,000.
The process of claim 5, wherein said polymers are tetrapolymers of the following general formula:
wherein R, R₁, R₂+, R₃ a, b and d are as defined in claim 5, R₄ is -OR₅ or
wherein R₅ and R₇ are as defined in claim 5, c is from about 0,2 to about 20 percent, and e is from about 0.1 to about 20 percent.
The process of claim 5, wherein said poly(acrylamide) based polymers are derived from monomer units of acrylamide, sodium acrylate, vinyl acetate, and mixtures of these and preferably from monomer units of acrylamide and sodium acrylate.
The process of anyone of claims 1 to 4, wherein said binding amount of said polymers is applied at an active polymer concentration between about 0.001 percent and about 0.3 percent by weight.
The process of anyone of claims 1 to 4, wherein said polymers are derived from monomer units of acrylamide and methacrylamide and derivatives thereof of the formula :
wherein R₁₃ is a hydrogen atom or a methyl group ; R₁₄ is a hydrogen atom, a methyl group or an ethyl group ; R₁₅ is a hydrogen atom, a methyl group, an ethyl group or -R₁₆-SO₃X, wherein R₁₆ is a divalent hydrocarbon group having 1 to 13 carbon atoms and X is a monovalent cation.
A product of the process of anyone of claims 1 to 4.