High carbon content iron-base briquettes and process for preparing same

Abstract: A process for preparing high carbon content briquettes includes providing a particulate material which includes iron particles including iron oxide in an amount of at least about 4% based on weight of the material, and carbon particles in an amount greater than about 2% based on weight of the material; and subjecting the material to briquetting temperature and pressure so as to provide stable agglomerate briquettes of the material.

Description: The invention relates to a process for preparing high carbon content briquettes and to a high carbon content briquette. Those briquettes are useful as feed material, particularly in iron and steel making processes. The production of suitably stable agglomerates from fine or coarse particles of iron oxide for use as feed material in iron and steel making furnaces is a well-established and rapidly expanding field. Production of such agglomerates are accomplished by means of bonding particles using suitable cementing particles or binders, followed by sintering, firing and cementing procedures. Hot briquetting is a process whereby iron ore particles are agglomerated using compacting techniques and the proper combination of chemical reduction, heat and pressure. Briquettes produced using such techniques are commercially known as hot briquetted iron (HBI). The hot briquetting technique, without binders, has been successfully completed using highly metallized materials which contain from about 0.01% up to a maximum of 2% carbon. When the carbon content exceeds 2%, known compacting techniques do not provide a sufficiently stable agglomerate material. Thus, the need exists for a process for preparing briquettes from starting material having a higher carbon content. JP-A-62227045 discloses hot pressure-molding of prereduced iron are having a metallization degree of 30-80 % in admixture with carbonaceous material, thereby obtaining moldings exhibiting thermoplasticity of the metallic iron component. The SU-A-852952 informs that a higher quality C-containing Fe ore briquettes are obtained more efficiently by mixing the ore with coal containing 35-40 wt. % volatiles, heating the mixture to a temperature at which the volatile components begin to evolve. The gaseous-product reduce the ore to 35-40 %, and the mixture containing 4-7 % C is then hot pressed at 275° C using 300-1200 kg/sq.cm. Partial 33-40 % reduction of the ore yields a plastic, easily deformed mixture, and the 4-7% C content is the optimal one. US-A-4,731,112 discloses a method of producing a ferroalloy comprising: forming compacts consisting essentially of a mixture of from 50 % to 88 % metallized direct reduced iron fines which fines are from 60 % to 97 % metallized, from 5 % to 15 % solid carbonaceous material, and from 7 % to 35 % of an oxide of a metal selected from the group consisting of, silicon, nickel, chromium, manganese, titanium, vanadium, molybdenum, and cobalt, charging only said compacts, additional solid carbonaceous material to provide additional heat and reactive carbon, and slag formers to a melting furnace; and burning said solid carbonaceous material to reduce the oxides in said compacts, to melt the constituents, and to form a high alloy melt. In GB-A-2103249 a method of producing castings using reduced iron as a raw material is disclosed which employs a vertical type shaft furnace construction, while a briquette which is produced by pressure molding reduced iron may be used as the raw material. The method comprises the steps of filling the hearth of a shaft furnace with a solid carbonaceous material, blowing hot air into the furnace adjacent the hearth of the shaft furnace, allowing the solid carbonaceous material to mix with the reduced iron, and utilizing the resulting waste gas heat for preheating said hot air. The briquette has a solid carbonaceous material and/or an inorganic binder incorporated therein. The surface of the briquette is formed with a coating of inorganic oxide having a melting point lower than that of the briquette. The density of the briquette is 4 g/cm 3 or above. It is therefore the primary object of the present invention to provide a process whereby high-carbon content iron particles can be agglomerated so as to provide a suitable stable briquette. It is a further object of the present invention to provide a process for preparing high carbon content briquettes with no additional binders, and containing no fused slag or vitreous phases. It is a further object of the present invention to provide a high carbon content briquette which is useful as a feed material in iron and steel making furnaces, and which has excellent physical properties. Further objects and advantages of the present invention will appear hereinbelow. The problems are solved by the technical features defined in the independent claims 1 and 12. Particular embodiments of the invention are given in the dependent claims. In accordance with the present invention, the foregoing objects and advantages have been readily attained. According to the invention, a process is provided for preparing high carbon content briquettes, which process comprises the steps of providing a particulate material comprising iron particles including iron oxide in an amount of at least 4% based on weight of said material, and carbon particles in an amount greater than 2% based on weight of said material, wherein said carbon particles comprise cementite in an amount between 85% and 95% based on weight of said carbon particles; and subjecting said material to briquetting temperature and pressure so as to provide stable agglomerate briquettes of said material. In further accordance with the present invention, a high carbon content briquette is provided, which briquette comprises a stable agglomerate of iron particles and carbon particles, said iron particles including metallized iron and iron oxide, said iron oxide being present in an amount of at least 4% based on weight of said briquette, and said carbon particles being present in an amount greater than 2.0% based on weight of said briquette, wherein said carbon particles comprise cementite in an amount between 85% and 95% based on the weight of said carbon particles. The invention relates to a high carbon content briquette which is useful as feed material for iron and steel making processes, and to a process for preparing high carbon content briquettes. In accordance with the invention, and advantageously, a process is provided whereby iron particles containing a substantial amount of carbon can be agglomerated into useful feed material briquettes without the need for additional binders and the like. In accordance with the invention, high carbon content briquettes, or high carbon briquettes (HCB), are produced starting with a particulate material containing iron particles and carbon particles, wherein the iron contains metallized or reduced iron as well as iron oxide, and wherein carbon is present in an amount greater than about 2.0%, preferably between about 2.1% and about 6.5%, based upon weight of the starting particulate material. This is an advantage over known processes which require that the material include carbon in far smaller amounts, typically between about 0.01% up to a maximum of 2.0%. It has been found in accordance with the present invention that stable agglomerates or briquettes can be prepared even with the increased amount of carbon when the iron particles include specific amounts of metallized iron and iron oxide. According to the invention, the starting particulate material preferably includes at least 80% total iron, more preferably between 88% and 93% total iron with respect to weight of the starting particulate material, and it is preferred that the material include metallized or reduced iron in an amount between 85% and 89% with respect to weight of the starting material, and iron oxide in an amount between 4% and 6% with respect to weight of the starting material. The starting particulate material may suitably be fine or coarse particles. It is particularly preferred that the starting particulate material have a particle size in the range of from 0.1 mm to 10 mm. Suitable starting particulate matter may be characterized by granulometric analysis showing 11.5% to 18.62% + 16 mesh, from 32.7% to 36.83% + 100 mesh, and from 40% to 57.22% - 100 mesh. Still further in accordance with the present invention, the starting particulate material is preferably provided having a binding index, or ratio of iron oxide (Fe+2) to metallized iron of between 0.03 and 0.05. The carbon particle portion of the starting particulate material is present in the form of cementite (Fe 3 C) and preferably graphite, and includes between 85% and 95% cementite and preferably between 5% and 15% graphite with respect to weight of the carbon particles. Such carbon particles, particularly cementite, are known to be sufficiently hard that briquetting through the application of temperature and pressure is difficult. In accordance with the present invention, however, the starting particulate material characterized as set forth above can be subjected to briquetting temperature and pressure, preferably a temperature of between 650°C and 750° C and a pressure of between 250 kg/cm 2 and 350 kg/cm 2 , such that the metallized iron and iron oxide, or wustite, flow into voids and spaces between the high carbon content particles, especially the cementite particles, so as to directly bond the iron particles to the carbon particles so as to form a stable agglomerate briquette as desired. The process as set forth above in accordance with the present invention can readily be used to provide briquettes of agglomerated particulate material, which are particularly useful as feed materials for iron and steel making processes, and which briquettes comprise stable agglomerate of iron particles and carbon particles wherein total iron is present in an amount of at least 80% weight, and carbon is present in an amount of greater than about 2.0% weight, preferably between 2.1% and 6.5% weight with respect to the briquettes. The total iron content of the briquettes is preferably between 88% and 93%, and the metallized iron portion of this iron is preferably present in an amount between 85% and about 89% based on weight of the briquettes. Briquettes prepared in accordance with the present invention are characterized by a density of between 4.4 g/cm 3 and 5.6 g/cm 3 , and a breakdown index of between 1.4% (wt.) and 1.6% (wt.) - 6 mm. As used herein, the breakdown index is the percent of ore fines from briquettes having a size less than a given size here 6 mm, after the briquettes have been subjected to a standard breakdown test. This breakdown index exhibited by briquettes according to the present invention is advantageous in that the briquettes, although made using high carbon content materials, exhibit density and breakdown indexes which are as good as values found in connection with conventional hot briquetted iron using starting materials having a maximum carbon content of 2%. Thus, in accordance with the present invention, a briquette and process for preparing same are provided wherein the starting materials can acceptably have a far greater carbon content, and the finishing briquette is nevertheless an extremely suitable feed material for the desired processes. Furthermore, the high carbon content material used in accordance with the present invention is advantageous due to the high energy content and the energy and associated cost savings provided by use of same. Briquettes in accordance with the present invention are also characterized by enhanced weather resistance due to the reduced tendency to react with moisture, and the lower tendency of the carbides to react with water. As set forth above, the starting particulate material for use in accordance with the present invention is not restricted to the use of fines, but could also include coarse or lumpy material due to the fact that the briquette forming process of the present invention effectively welds the particles together, and the strength of the resulting briquettes depends primarily on the strength of the bonds between the particles. The high carbon content briquettes of the present invention have excellent physical strength for withstanding transport and handling in steel and iron shops, and further exhibits a lower level of fines and dust which contain free carbon, thereby reducing environmental pollution associated with the handling of same. This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein.

Claims: A process for preparing high carbon content briquettes, comprising the steps of: providing a particulate material comprising iron particles including iron oxide in an amount of at least 4% based on weight of said material, and carbon particles in an amount greater than 2% based on weight of said material, wherein said carbon particles comprise cementite in an amount between 85% and 95% based on weight of said carbon particles; and subjecting said material to briquetting temperature and pressure so as to provide stable agglomerate briquettes of said material. A process according to claim 1, wherein said subjecting step causes said iron and said iron oxide to flow between said carbon particles so as to directly bond said iron particles and said carbon particles. A process according to claim 1, wherein said providing step comprises providing said particulate material comprising at least 80% total iron including said iron oxide in an amount between 4% and 6%, and comprising said carbon particles in an amount between 2.1% and 6.5% based on weight of said particulate material. A process according to one of the claims 1 to 3, wherein said providing step comprises providing said material consisting essentially of said iron particles and said carbon particles, whereby said briquettes are substantially free of binders. A process according to one of the claims 1 to 4, wherein said providing step comprises providing said material wherein said carbon particles comprise cementite in an amount between 85% and 95% based on weight of said carbon particles, and graphite in an amount between 5% and 15% based on weight of said carbon particles. A process according to one of the claims 1 to 5, wherein said providing step comprises providing said material including total iron in an amount between 88% and 93% based on weight of said material, particularly providing said material including metallized iron in an amount between 85% and 89% based on weight of said material. A process according to one of the claims 1 to 6, wherein said providing step comprises providing said material including metallized iron and said iron oxide at a ratio by weight of said iron oxide to said metallized iron of between 0.03 and 0.05. A process according to one of the claims 1 to 7, wherein said briquetting temperature and pressure comprise a temperature of between 650°C and 750°C and a pressure of between 250 kg/cm 2 and 350 kg/cm 2 . A process according to one of the claims 1 to 8, wherein said subjecting step provides briquettes containing iron and carbon wherein said carbon is present in an amount greater than 2% based on total weight of said briquettes. A process according to one of the claims 1 to 9, wherein said subjecting step provides said briquettes having a density of between 4.4 g/cm 3 and 5.6 g/cm 3 , and a breakdown index of between 1.4% (wt.) and 1.6% (wt.) - 6 mm. A process according to one of the claims 1 to 10, wherein said particulate material has a particle size in a range of from 0.1 mm to 10 mm. A high carbon content briquette, which is obtainable by a process according to at least one of the claims 1 to 11, comprising a stable agglomerate of iron particles and carbon particles, said iron particles including metallized iron and iron oxide, said iron oxide being present in an amount of at least 4% based on weight of said briquette, and said carbon particles being present in an amount greater than 2.0% based on weight of said briquette, wherein said carbon particles comprise cementite in an amount between 85% and 95% based on weight of said carbon particles. A briquette according to claim 12, wherein said briquette comprises total iron in an amount of at least 80% based on weight of said briquette, and wherein said iron oxide is present in an amount between 4% and 6% based on weight of said briquette, and wherein said carbon particles are present in an amount between about 2.1% and 6.5% based on weight of said briquette. A briquette according to claim 12 or 13, wherein said carbon particles comprise graphite in an amount between 5% and 15% based on weight of said carbon particles. A briquette according to claim 12 or 13, wherein said briquette comprises iron in an amount between 88% and 93% based on weight of said briquette, wherein said metallized iron is preferably present in an amount between 85% and 89% based on weight of said briquette. A briquette according to one of the claims 12 to 15, wherein said iron oxide and said metallized iron are present at a ratio of said iron oxide to said metallized iron of between 0.03 and 0.05. A briquette according to one of the claims 12 to 16, wherein said briquette is characterized by a density of between 4.4 g/cm 3 and 5.6 g/cm 3 , and a breakdown index of between 1.4% (wt.) and 1.6% (wt.) - 6 mm. A high carbon content briquette, which is obtainable by a process according to at least one of the claims 1 to 11, consisting essentially of iron particles and carbon particles, said iron being present as metallized iron and iron oxide, said iron oxide being present in an amount of at least 4% based on weight of said briquette, and said carbon particles being present in an amount greater than 2.0% based on weight of said briquette. , wherein said carbon particles comprise cementite in an amount between 85% and 95% based on weight of said carbon particles, A briquette according to claim 18, wherein said iron particles and said carbon particles are bonded substantially directly together.

Inventors: CARRASQUERO DAVID, MASSO EMILIO QUERO, CARRASQUERO, DAVID, MASSO, EMILIO QUERO
Applicants: ORINOCO IRON C A A CORP OF VEN, ORINOCO IRON, C.A. A CORPORATION OF VENEZUELA
Application year: 1999
Main classification: C22B1
IPC codes: C22B5, C22B1, C21B5, C21B13