Patent Application
20240384363
The present invention relates to solid agglomerates. More specifically, the present invention relates to solid agglomerates for use in steel reduction furnaces.
One of the main pieces of equipment where the iron reduction process takes place is called a Blast Furnace, and its function is to cause the separation of Fe iron from its Fe2O3 ore. This separation takes place by means of chemical reduction, which involves separating a metal from its oxide, and is carried out using a reducing agent. This reducing agent is a material that must be more attractive to oxygen, under the conditions of the operation, than the metal to be reduced. Main reducing agent used in the steel industry is coke, which comes from mineral coal.
Steel industry relies heavily on metallurgical coal, which accounts for a large proportion of the final cost of the steel produced. Mineral coal for integrated coking steelmaking is called coking coal, which is an essential substance in the reduction of iron ore to metallic iron, as it combines with oxygen to create carbon dioxide, iron and slag.
The class of coal commonly used for steelmaking is bituminous coal (soft coal) which forms a solid mass when heated (coking coal); on the other hand, if it does not soften or aggregate when heated, it is called non-coking coal.
Today, the use of agglomerates in the steel industry is becoming increasingly common. Agglomeration process consists of grouping fine-grained materials with the aim of obtaining a larger product through the use of binders. Through this process it is possible to obtain, for example, high-quality metal agglomerates or coal briquettes, taking advantage of the small fractions that are usually discarded. In some cases, coal agglomerates can replace coking coal and metal agglomerates can replace iron ore.
Among the different agglomeration processes, the coal briquetting technique has been gaining ground in the industry. This technique, which can be used for both mineral and vegetable coal, generally involves the following steps: (i) granulometric balancing of the coal or biomass particles; (ii) mixing of binders (agglomerants); (iii) mechanical compaction; and (iv) drying of the briquettes. The documents below describe examples of coal briquettes and its respective production processes.
Document U.S. Pat. No. 8,585,786B2, for example, describes a method and system for briquetting solid fuel, such as coal. In this document, the solid fuel is conveyed through a continuous feed solid fuel treatment plant, treated with electromagnetic energy and briquetted after treatment.
Document WO2014098413A1 describes a coal briquette and a method for manufacturing it. Said method for manufacturing coal briquettes comprises the steps of (i) supplying pulverized coal, (ii) producing a mixture obtained by mixing between 1 and 5 parts by weight of a hardening agent and between 5 and 15 parts by weight of a binder in relation to 100 parts by weight of pulverized coal, and (iii) shaping the mixture. In the step of supplying the pulverized coal, the pulverized coal comprises (i) more than 0 and not more than 50% by weight of low-grade coal and (ii) a balance of coal ash. The low-grade coal has between 25% by weight and 40% by weight of a volatile fraction (dry basis) and has a crucible expansion number of more than 0 and less than 3.
Document WO2013152959A1 describes a process for producing a briquette containing coals, where the coals together with a binder system are subjected to mixing with the introduction of steam and the mixture obtained is subjected to pressing to form briquettes. Here, at least one of the steps: (i) drying the carbon carriers before mixing, (ii) setting the temperature of the carbon carriers to be mixed with the binder system before mixing in a predefined temperature range, (iii) heat treatment of the briquettes after pressing, is carried out by means of direct or indirect interaction with superheated steam. Residual steam obtained is used as at least part of the steam introduced during mixing.
Document AU2008203855B2 describes a process for forming a briquette comprising low rank coal and aggregate material, characterized in that it comprises: drying a feed of low rank coal to produce a dry coal with a moisture content of between 8 and 16% by weight; mixing the dry coal with an aggregate material; and compacting the dry coal and aggregate material mixture into briquettes.
As mentioned above, coal briquettes can be used in the process of reducing iron ore or its agglomerates in steelmaking furnaces. However, if used directly in the furnace without prior coking treatment, these briquettes end up sticking together, forming so-called “bunches”. This is because, inside the furnace, the heat causes the surfaces of the briquettes to soften, favoring the bonding of one briquette with another or with the ore.
As a result, there is no solid agglomerate in the state of the art, such as coal briquettes, which can be used directly inside reduction furnaces without prior treatment, under penalty of forming bunches and making the process unfeasible.
The invention proposed here solves the problems of the state of the art described above in a simple and efficient way.
The first objective of the present invention is to provide a solid agglomerate for use in a steelmaking furnace that does not require prior coking treatment.
A second objective of the present invention is to provide a solid agglomerate for use in a steelmaking furnace that prevents the agglomerates inside the furnace from sticking together (forming bunches) when it are heated.
In order to achieve the objectives described above, the present invention provides a solid agglomerate for use in a steel reduction furnace, comprising a core formed by a first composition and a coating formed by a second composition, where the second composition comprises at least one compound that acts as an inert sacrificial material during the reduction process inside the steel furnace.
Detailed description presented below refers to the attached figures and its respective reference numbers.
First of all, it should be noted that the following description is based on a preferred embodiment of the invention. As will be evident to anyone skilled in the art, however, the invention is not limited to this particular embodiment.
The present invention therefore provides a solid agglomerate A, illustrated in
Solid agglomerate A of the present invention can be, for example, a fuel coal briquette or a metallic agglomerate, such as a pellet or a ferrous briquette.
In the case of the fuel briquette, preferably the first composition, which forms the core N, comprises at least one coking coal and at least one binder. N core material, therefore, is the coking material commonly used in fuel briquettes. More preferably, the first composition, which forms the N core, comprises 60 to 70% by mass of coking coal and 6 to 10% by mass of binder.
Preferably, the second composition, which forms the R coating, comprises a non-coking coal, or residue thereof, and at least one binder. Coal in the R coating composition can be, for example, coke grindings or coal waste in general, low-quality coals, etc. It's worth noting here that any inert coal waste (non-coking) can be used in the R-coating composition. This way, when heating inside the reduction furnace, the R-coating material won't coking, which prevents sticking between the surfaces of the agglomerates and, consequently, the formation of bunches.
More preferably, the second composition, which forms the R-coating, comprises 70 to 95% by mass of non-coking coal, coke grindings, coal waste or any combination thereof, and 5 to 15% by mass of binder.
In a second embodiment of the present invention, the solid agglomerate A is a metallic agglomerate, such as a ferrous pellet or briquette. In this case, an inert material, preferably metallic, is used in the R-coating of the agglomerate to act as a sacrificial material. Core N would be formed by the material of interest.
Solid agglomerate A of the present invention can be manufactured in any existing geometric shape, so that the scope of protection of the present invention is not limited to the oval shape shown in
Thus, as explained above, the present invention provides a solid agglomerate A for use in a steelmaking furnace that does not require prior coking treatment since the sacrificial material in the coating prevents the agglomerates from sticking together (forming bunches) inside the furnace when it is heated.
Numerous variations on the scope of protection of this application are allowed. This reinforces the fact that the present invention is not limited to the particular configurations/embodiments described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1020210184108 | Sep 2021 | BR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/BR2022/050317 | 8/12/2022 | WO |
