Normally, iron ore pellets are produced through a process in whi- ch the iron ore is mixed with the necessary additives to adapt the desired chemical composition to be further pelletized in rotatory disks or drums.

The resultant elements are the pellets-iron ore agglomerates- of semi-spherical shape, which are transported to a straight grate furnace, where they undergo a thermal processing with temperatures up to about 1360°C. Right after the discharge of the pelletizing furnaces in the production process, the iron ore pellets undergo different handling stages. The first stage consists of stocking through piling. The second stage consists of ship- ping, through the reclaim and loading of vessels, followed by a marine trans- portation stage, which will take the pellets to the clients, who will accomplish the stage of discharge of pellets.

The pellet can undergo stocking stages in the user's patio and feeding of furnaces or reactors, where the reduction of iron ore will occur; or undergo an intermediary stage, and further stock load and discharge in barge or train, in order to transport the pellets to the user's patio.

The necessary time so that the flux, from the exit of the straight grate furnace to reduction in blast furnace or reactors of direct reduction, be completed varies usually from 3 to 6 months and the stock stages are made in outdoors patios.

Concerning the physical aspect, the handling of pellets or of any other iron ore agglomerate, through the mechanical attrition forces between each pellet or agglomerate, leads to the generation of fine particles-smaller than 0,5 mm. In this granulometry range, these fine particles are dragged by

any airflow stronger than 5m/s-winds-, very common during the handling while transporting-operations in apron conveyers, operations with trucks, operations with vessels, operations with tractors and power shovels-, or e- ven during the stock period in piles. The dragging of these fines is extremely undesirable and harmful to the environment since it is classified as a source of dust generation.

Due to its high specific surface, the amount of fines that is not dragged by the wind and is adhered to the pellets volume or other iron ore agglomerate, which are fed in the reduction reactors for the production of primary iron, jeopardizes the good performance of the reduction process t- hrough expressive production decrease, besides the increase of combustible consumption-coal, coke, natural gas-, high cost materials in these proc- esses. In this case, a main contact of the fine with hot gases inside the re- duction reactors allows the occurrence of bridges formation and conse- quently, the formation of great masses of pellets aggregate with fines charac- terizing the sticking. These aggregates prevent the adequate flux of gases in the reactors, causing preferential fluxes or even the airtigthtness of the reac- tors. Specifically in the process of direct reduction of iron ore pellets in the reactors of direct reduction-where melting does not occur-, at temperatures higher than 600°C, the sticking tendency is more expressive, since this stick- ing is related to a surface phenomenon in which fibrous iron is formed. Sev- eral invention patents relate the application of superficial oxides coverage and/or oxides mixtures in iron ore pellets to minimize the formation of fibrous iron and the sticking effect. However, the fixation of these oxides coverage and/or oxides mixtures during the handling of pellets are equally subject to abrasion efforts and the consequent generation of fines smaller than 0,5 mm.

Another problem, concerning the degradation or aging of the iron ore pellets - process characterized by the degradation of the physical and metallurgical properties as time goes by and during the stock of pellets or another iron ore agglomerate, before its use in the reduction reactors. The mechanism of the iron ore agglomerates aging process-pellets, sinters and briquettes-is con- nected to the decomposition of some phases that contain calcium, and the

formation of new compounds through reactions with water and carbon diox- ide contained in the atmosphere. The water penetrates in the superficial po- res of the iron ore agglomerates, reacting with the CaO present, forming cal- cium hydroxide [Ca (OH) 2]. The contact of the calcium hydroxide with the carbon dioxide (C02) in the atmosphere at ambient temperature leads to the formation of calcium carbonate (CaC03, free energy AG =-28, 2270kcal/mol, at 25 °C). This process is followed by volumetric expansion, causing the deg- radation of the physical structure of the iron ore agglomerates. This mecha- nism is described in equations 1-4.

CaO + H20 o Ca (OH) 2 (1) C02 + H20-> H2CO3 (2) 2H2CO3 + Ca (OH) 2- Ca (HCO3) 2 + 2H20 (3) Ca (HCO3) 2- CaCOs + H20T + COst (4) The water-H20-cited in equations 1 and 2 can originate from the water added in the agglomerates right after the discharge of the furnace for dust contention or from rainy water, air humidity, among others. As an example, we can say that in iron ore pellets stored for long periods of time, it is possible to observe the appearance of white dots in their surfaces which are the calcium carbonate precipitated mentioned in equation 4-the contact of these white dots with hydrochloric acid causes effervescence and shows evident presence of CaC03.

This invention deals with a new type of iron ore agglomerate or other type of material-pellets, sinters, briquettes-with reduced generation of abrasion fines, sticking, degradation by aging, dust emission, and its pro- duction process.

The innovative concept of the invention is based on the applica- tion of polymers or acrylic copolymers and polymers or vinyl acetate copoly- mers or synthetic oils, ranging from 0,14 to 1% in agglomerate mass, to form a protective layer-coating-in the surface of the substratum agglomerate-, whose physical, chemical and mechanical properties enable the new ag- glomerate to resist the abrasion efforts during handling, minimizing the gen- eration of fines and consequently the reduction of 80 to 95 % of dust emis-

sion. With the reduction of the quantity of fines, the deleterious effect of the sticking inside the reactors decreases. In the case of direct reduction proc- ess, the protective layer increases the fixation of the oxides and/or of oxides mixtures added, significantly reducing the formation of fibrous iron and stick- ing. The protective layer also provides superficial waterproofing of the ag- glomerates, obstructing the penetration of humidity through the surface, minimizing the advance of the degradation mechanism by aging and han- dling, characterized by the generation of a maximum weight of 1 % of smaller agglomerate particles of 6,3 mm.

The protective layer is constituted of acrylic polymers or vinyl a- cetate-structures composed of carbon, hydrogen and other elements as radicals, formed from small units called"mers", or acrylic copolymers or vinyl acetate-polymers constituted of different units of repetition or"mers"-, or synthetic oils that can have esters basis.

The use of polymers and copolymers is widely spread in the ag- glomeration area, especially in the iron ore pelletizing process, as in patent US 5,171, 781 where Farrar et al teaches the use of polymers as agglomera- tive. The agglomerative is added to the iron ore with the other additives be- fore the pelletizing in rotatory disks or drums, as described previously.

Other application known to technicians related to the subject, described for example in patent US 5,271, 859, where Roe teaches us how to use polymers as dust suppressor when applied in surfaces at temperatures up to 316 °C. But, in none of them he taught or evaluated the effects that the incorporation in the surface and in polymers pores and acrylic copolymers, polymers and vinyl acetate copolymers or synthetic oils, after the formation of the protective layer, provide the iron ore pellets with characteristics claimed in this invention. We will further discuss and evidence abrasion, degradation, dust emission and reduction of sticking tendency indexes reached by the pel- let of this invention.

The addition of saturated hydrocarbons-petroleum paraffin-, to the surface of the iron ore pellets is also presented as a good constituent for the formation of the protective layer, however with some disadvantages re-

garding the polymers, copolymers and synthetic oils proposed as additives in this invention. The main disadvantage, evidenced in table 1, is the effective- ness for fixation of the additive to the pellet when its surface is above 100 °C.

The use of copolymers and/or acrylic polymers or vinyl acetate, or synthetic oils, or even petroleum paraffin should meet the following prem- ises to guarantee the efficiency of the protective layer : To not completely vaporize during the application of the protective layer, considering that the temperature of the pellets during the ap- plication is between 150 and 300°C ; To be able to fixate the oxides and/or mixture of oxides used to a- void the formation of fibrous iron, and that are in the surface of the iron ore pellets in proportions that vary from 2 to 5 parts for every 1000 parts of pellets, guaranteeing a sticking level lower than 10% measured through procedure IS011256 at 850°C, and lower than 15% measured through the same procedure at 950°C ; To enable the application through spray or immersion; To not contain sulfur, chlorine, heavy metals, benzene, potassium, sodium or phosphorus; In the case of iron ore pellets, to check resistance to abrasion after the application, measured through the resistance level to wear though abrasion-IS03271-lower than 2,0% ; Based on the information exposed so far, the inventor led theo- retical studies and experiments in laboratory scale (in the facilities of Samar- co Mineração S. A. ), besides in industrial production scale experiments with iron ore pellets, with the addition of copolymers and polymers, henceforth generically denominated polymers, and synthetic oils of esters basis in low percentile, to block the effects of degradation by aging, to increase pellets resistance to wear through abrasion, to reduce the generation of fines smaller than 0,5mm, to reduce dust emission, to reduce sticking tendency, and to drastically minimize the use of water during its handling.

In the experiments accomplished in laboratory scale, the follow- ing procedure was used.

Representative samples of finished iron ore pellets were col- lected, that is, after the burning thermal processing, for the accomplishment of rehearsals of wear through abrasion, according to procedure IS03271. To simulate the temperature conditions of pellets in the discharge of pelletizing furnaces, and to evaluate the behavior of additives in these conditions, the samples were heated in hothouses at different temperature levels.

To generate reference data, fifty percent of the samples were submitted to wear tests through abrasion without the addition of polymers, synthetic oils or petroleum paraffin. The other fifty percent of the remaining samples received applications of polymers, synthetic oils and petroleum par- affin. All samples were submitted to wear tests through abrasion-IS03271.

The table 1 shows the results of wear tests through abrasion- IS03271-for polymers, synthetic oil and petroleum paraffin respectively.

Table 1-Resistance to Abrasion Indexes (Percentile smaller than 0,5 mm) Vinyl Petroleum Acrylic Synthetic Natural Acetate Paraffin Polymers Oils Polymers Abrasion index of pellets at ambient ,. 5, 20 temperature. Abrasion index after pellets stratifia - 1, 35 2,30 2,55 0,90 tion at ambient temperature. Abrasion index after pellets stratifia tion at a temperature of 50 °C Abrasion index after pellets stratifica- - 4,15 1,75 2,25 1,30 tion at a temperature of 100 °C Abrasion index after pellets stratifica- - 4,40 1,45 1,75 1,75 tion at a temperature of 200 °C In table 1, the data identified as NATURAL represents samples of references composed of pellets without additives and at ambient tempera- ture.

After analysis of the curves we can conclude that: 1) With the addition of polymers and/or synthetic oils it is possible to obtain data on the resistance index to wear through abrasion lower than 2,0%, and these results are repeated with pellets temperature varying from

the temperature of discharge of pelletizing furnaces (about 250°C) until am- bient temperature. In the case of polymers, this effect is more evident with increase of pellets temperature, since the water loss contained in the poly- mers emulsion collaborates to the rise of the temperature of vitreous transi- tion of the polymers adhered to the surface of pellets and more concentrated, allowing the formation of the protective layer as soon as the pellets cool off.

For synthetic oils one can notice that, in spite of the good results in the tem- perature ranges tested, there is a tendency to efficiency reduction, if the tem- perature increase continues. In fact, vaporization of the oil during the tests was observed, although much less expressive than in petroleum paraffin, which will be commented next.

2) After the addition of petroleum paraffin it is possible to obtain values of the resistance index to wear through abrasion lower than 2,0%.

However, this result is only obtained for pellets in temperatures between 50°C and ambient temperature. For temperatures higher than 50°C, the petro- leum paraffin lose its efficiency in the reduction of wear through abrasion, result- ing in values very close to the reference samples for this index and intense va- porization of this additive at this temperature range was once observed.

At the same time, sticking rehearsals were made, according to standard ISO11256, to evaluate the behavior of pellets during reduction in direct reduction reactors, regarding this phenomenon. In these tests bauxite was used as oxide to minimize the formation of fibrous iron.

The data identified as natural belongs to the reference samples, that is, without addition of bauxites, polymers, petroleum oils or paraffin.

The sequence of rehearsals and the accomplishment of differen- tiated tests among additives were based on the individual behavior of each additive during rehearsals. With this focus, it sticking tests with synthetic oils were not accomplished, since the vaporization behavior in temperatures higher than 200°C had already been detected and, therefore, the paraffin re- sults were adopted, presenting a more critical situation of vaporization than the oils, as well as a good reference for the synthetic oils, once the tempera- ture of test ISO11256, reaches 850°C.

Tables 2 and 3 show results obtained with petroleum and poly- mers paraffin, respectively.

Table 2-Sticking Evaluation tests (ISO11256) for petroleum paraffin Pellets condition Sticking Index (%) Natural 72,3 With Bauxite stratification 48,9 With Petroleum Paraffin stratification 69,1 With Bauxite and Paraffin stratification 13,4 Table 3-Sticking Evaluation tests (ISO11256) for polymers Pellets Condition Sticking Index Natural 42, 36 % With Bauxite stratification 20, 15 % With Bauxite stratification, after abrasion 44, 05 % With Bauxite and Polymers stratification 11, 64 % With Bauxite and Polymers stratification, after abrasion 26, 97 %

Through tests whose results are represented in tables 2 and 3, it was possible to obtain the following conclusions : A) Observing the data in table 2, we can notice that the efficiency of the protective layer with petroleum paraffin increases when the mixture of this additive with bauxite is processed. This conclusion confirms the theory that the protective layer has a property to fixate the oxide used to inhibit the formation of fibrous iron. However, during tests, the effect of high tempera- ture on the petroleum paraffin led to intense vaporization of this additive, causing blockage in the exhaustion pipes of the apparatus set for the accom- plishment of tests, which was enough to begin tests with polymers.

B) Preliminary tests showed that the protective layer processed with the polymers mixture with bauxite is more efficient than when only the polymers is added. Base on this affirmation, sticking tests were accom- plished, with samples undergoing two situations: 1) Right after the processing of coverage with oxide or the poly- mers+ oxide mixture; 2) Right after the resistance test to wear of pallets through abrasion

with oxide coverage or the polymers+ oxide mixture; The goal in these tests is to test the resistance of the protective layer in fixating the oxides, the bauxite in this case, even under aggressive handling conditions.

With this focus, table 3 shows the efficiency of the protective la- yer in fixating the bauxite, since the result of the sticking test resulted in 26,97%, which is considered a very satisfactory result in the circumstances of the test, comparing to the natural sample or to the bauxite sample after the abrasion test which was of 44,05%.

In none of the tests with polymers any blockage or obstruction in the exhaustion pipes was detected in the apparatus set for the accomplish- ment of tests.

To confirm sticking results of the protective layer using polymers mixture with bauxite, tests were accomplished varying the quantity of bauxite added, maintaining the same polymers amount and the results are shown in table 4.

Table 4-Sticking Evaluation tests (ISO11256) for polymers mixture with bau- xite at different of bauxite proportions. Pellets Condition/Test Temperature Sticking Index With Bauxite and Polymers stratification, with 0,45 % of Bau- xite weight. 5, 64 % Tested at 850 °C With Bauxite and Polymers stratification, with 0,25 % of Bau- xite weight. 5, 90 % Tested at 850 °C With Bauxite and Polymers stratification, with 0,45 % of Bau- xite weight. 13. 20 % Tested at 950 °C With Bauxite and Polymers stratification, with 0,25 % of Bau- xite weight. 37, 20 % Tested at 950 °C Based on the conclusions of the analysis of table 3, concerning

the good capacity of the protective layer with polymers for fixating bauxite, the evaluation of table 4 shows that the increase of bauxite added, keeping the same polymers quantity, allows the protective layer to be resistant enou- gh to guarantee very low values in the sticking index, even when the test is led outside normal temperature conditions, that is, in higher temperatures which in this case was of 950°C.

Other tests were conducted, such as chemical analyses, using chromatography and X-ray spectrometry methodology, and the presence of sulfur, chlorine, heavy metals, benzene, potassium, sodium or phosphorus in the polymers as well as in the petroleum paraffin was not detected. These tests were not accomplished for the synthetic oil with ester base.

The addition of polymers and synthetic oils, in the industrial pro- cess is best accomplished through the preparation of the polymers or acrylic copolymers solution, polymers or vinyl acetate copolymers or synthetic oils diluted in 50 to 80 % in water, comprehending mixture and homogenization, and further transport of the solution until the application site, where the stratification of iron ore pallets through aspersion is obtained, in the pro- portion of 0,7 to 2% in mass of the agglomerate flux or ore, inside transfer chutes or through screening process, not limited to these points.