Solid Carbonized Agglomerate, and Its Manufacturing Method

This Application is a continuation-in-part of U.S. application Ser. No. 19/127,283, filed May 5, 2025, which is a 371 national phase application of PCT/BR2023/050282, filed Aug. 25, 2023, which claims the benefit of priority of Brazilian Application No. 1020220232628 filed Nov. 16, 2022, the contents of each of which are incorporated herein by reference.

The present invention relates to solid agglomerates. More specifically, the present invention relates to solid agglomerates for use in blast furnaces.

One of the main functions of metallurgical furnaces is the reduction of iron, where the metal is separated from its oxide, in the case of iron, usually ores rich in FeO, which are transformed into Fe. This separation occurs by means of chemical reduction, which involves separating a metal from its oxide, and is carried out using a reducing agent. This reducer is a material that must be more attractive to oxygen, under the conditions of the operation, than the metal to be reduced. The main source of reducing agent used in the steel industry is coke, which comes from mineral coal.

The 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 essential for the manufacture of coke, which in turn is indispensable in the reduction of iron ore to metallic iron in blast furnaces. In this process the fuel combines with oxygen to create carbon dioxide, which transforms the iron oxides into iron and separates it from the slag.

Today, the use of agglomerates in the steel industry is becoming increasingly common. The 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 metallic agglomerates or coal briquettes, taking advantage of the small fractions that are usually discarded. In some cases, coal pellets can replace coking coal and metal pellets 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 coal and charcoal, 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 their 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 transported 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. This coal briquette manufacturing method comprises the steps of (i) pulverized coal supply, (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 pulverized coal supply stage, the pulverized coal comprises (i) more than 0 and no more than 50% by weight of low-grade coal and (ii) a balance of coal ash. Low-grade coal has between 25% and 40% by weight of a volatile fraction (dry base) and has a crucible expansion number of more than 0 and less than 3.

Document WO2013152959A1 describes a process for the production of a briquette containing coals, where the coals together with a binding 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 binding 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. The 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 by the fact that it comprises: drying a low rank coal feed 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. Document WO2011108466A1, for example, describes a process to produce ferro-coke by carbonizing an agglomerate comprising mineral coal and iron ore. The process produces ferro-coke which, in a blast furnace, is more reactive than the coke it contains with CO2. The ferro-coke production process in document WO2011108466A1 comprises the carbonization at a temperature above 800° C. of a mixture composed of coal and iron ore to produce ferro-coke.

The process in document WO2011108466A1 ends up not being ecologically sustainable since it requires significant amounts of energy to carbonize the agglomerate and does not provide for the use of renewable carbonaceous material.

In addition, the agglomerates in the state of the art present difficulties in their production at the coking stage. The coking of these agglomerates is commonly carried out in coking plants, which are a silicon carbide refractory. In this scenario, the iron oxide present in the agglomerate reacts with the silicon oxide from the coking plant and forms low melting point phases that corrode the refractory, representing an operational hazard.

In addition, state-of-the-art agglomerates only provide catalysis of the gasification reaction (Boudouard reaction) of the agglomerate in the blast furnace at high temperatures, which implies greater energy expenditure to reach these temperatures.

This invention solves the problems described above in the prior art in a simple and efficient way.

A first objective of the present invention is to provide a solid carbonized agglomerate for use in a blast furnace and a method of manufacturing it in which the carbonization method is carried out at relatively low temperatures.

A second objective of the present invention is to provide a solid carbonized agglomerate for use in a blast furnace and a method of manufacturing it that combines the catalysis of calcium and iron sources, such as residues.

A third objective of the present invention is to provide a solid carbonized agglomerate for use in a blast furnace and a method of manufacturing it that uses a reasonable amount of biocarbon, increasing the ecological sustainability of the fuel.

A fourth objective of the present invention is to provide a solid carbonized agglomerate for use in blast furnaces and a method of manufacturing it that does not react with the refractory material in the coking plant, thus increasing the safety of agglomerate production.

In order to achieve the objectives described above, the present invention provides a method of manufacturing a solid carbonized agglomerate for use in a blast furnace, characterized by the fact that it comprises the steps of: mixing at least one source of carbon, at least one source of calcium and at least one binder; mechanically shaping the mixture of the at least one source of carbon, the at least one source of calcium and the at least one binder so as to form a shaped solid agglomerate; and pyrolyzing the shaped solid agglomerate at a temperature greater than or equal to 600° C. and less than 800° C.; wherein the solid agglomerate comprises 25 to 35% by mass of the at least one source of calcium.

The present invention also provides a carbonized solid agglomerate for use in a blast furnace, comprising in its composition: at least one source of carbon; at least one source of calcium; and at least one binder; wherein, after the mechanical shaping of the solid agglomerate, the solid agglomerate is at a temperature greater than or equal to 600° C. and less than 800° C.; in which the solid agglomerate comprises 25 to 35% by mass of at least one source of calcium ().

First of all, it should be noted that the following description will be 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 provides a method of manufacturing a solid carbonized agglomerate for use in a blast furnace, characterized by the fact that it comprises the steps of: mixingat least one source of carbon, at least one source of calciumand at least one binder; mechanicallythe mixture of the at least one source of carbon, the at least one source of calciumand the at least one binderso as to form a shaped solid agglomerate; and pyrolyzingthe shaped solid agglomerateat a temperature of greater than or equal to 600° C. and less than 800° C.; wherein the solid agglomerate comprises 25 to 35% by mass of the at least one source of calcium.

It should be noted that this certificate of incorporation refers to an improvement of a solid carbonized agglomerate and the process for manufacturing it as described in BR102022023262-8, which will be explained below for a better understanding of the invention.

A coked solid agglomerate for use in a steel furnace is described, comprising biocarbon, mineral coal and at least one binder. For the purposes of this description, biocarbon means any charcoal of plant origin produced according to substantially sustainable standards. Preferably, this biocarbon has a low inorganic content (less than 1%).

Once submitted to mechanical shaping, the solid agglomerate undergoes a pyrolysis process at a temperature greater than or equal to 700° C. and less than 800° C. This heat treatment cokes the carbonaceous material in the mixture and increases the interaction and anchoring between all the components of the solid agglomerate, improving its mechanical strength. In addition, the pyrolysis of the solid agglomerate promotes its drying and pre-reduction, increasing its calorific value and preparing it for use in steel furnaces.

Preferably, the pyrolysis of the solid agglomerate is carried out in a rotating cylindrical reactor.

Preferably, the solid agglomerate comprises 10 to 75% by mass of biocarbon. More preferably, the solid agglomerate comprises 50 to 65% by mass of biocarbon.

Preferably, the solid agglomerate comprises 25 to 90% by mass of coal. More preferably, the solid agglomerate comprises 25 to 50% by mass of coal.

Preferably, the solid agglomerate contains 5 to 10% by mass of a binder, which has the function of keeping the compounds in the solid agglomerate bound together. The use of a binder also allows for the use of smaller-grained compounds in the composition of the solid agglomerate.

Optionally, the solid agglomerate also contains 5 to 15% by mass of an iron-based compound, such as iron oxide or metallic iron. The source of iron used is preferably steelmaking waste, such as sludge from steelmaking processes. Mixing an iron-based compound with the agglomerate produces an iron-containing agglomerate. As is well known, due to the catalytic effect of the iron content of the iron-containing agglomerate, the reaction of the carbonaceous material starts from a lower temperature compared to conventional coke and, as a result, a reduction effect can be expected and, as a result, one can expect a reducing effect on the reducing agent ratio (RAR) by lowering the temperature of the thermal reserve zone when iron-containing agglomerate is used as a charge material in the steel furnace.

A process for manufacturing a solid coked agglomerate for use in a steelmaking furnace is also described, comprising the steps of (i) mixing biocarbon, coal and at least one binder, (ii) mechanically shaping the mixture of biocarbon, coal and at least one binder to form a solid agglomerate, and (iii) pyrolyzing the solid agglomerate at a temperature greater than or equal to 700° C. and less than 800° C.

Preferably, the mixing stage is carried out with 10 to 75% by mass of biocarbon. More preferably, the mixing stage is carried out with 50 to 65% by mass of biocarbon.

Preferably, the mixing stage is carried out with 25 to 90% by mass of coal. More preferably, the mixing stage is carried out with 25 to 50% by mass of coal.

Preferably, the mixing stage is carried out with 5 to 10% by mass of a binder.

Optionally, the mixing step additionally involves mixing 5 to 15% by mass of an iron-based compound such as iron oxide or metallic iron to form an iron-containing agglomerate.

It should be noted that, due to temperatures lower than 800° C., solid agglomerate and the process of making it have considerable energy savings in the manufacturing process.

Coked solid agglomerate can be used in blast furnaces and sintering ovens. Solid agglomerate containing iron can be used to replace small coke in blast furnaces.

illustrates a flowchart of the manufacturing method for solid carbonized agglomerate. Preferably, the manufacturing method comprises mixingat least one source of carbon, at least one source of calciumand at least one binder, mechanically shapingthe mixture using rotating rollers to form a briquette-shaped agglomerate, and pyrolyzingthe shaped agglomerateat a temperature of between 600° C. and 800° C. so that the material is carbonized.

Optionally, after the mechanical shaping step, the method of the present invention comprises dryingthe shaped agglomeratein an oven at 105° C. for two hours with the humidity inside the oven being less than 1%.

Preferably, the step of pyrolyzingthe shaped agglomerateis carried out in a cylindrical rotary reactor. This heat treatment causes the carbonaceous material in the mixture to be carbonized and increases the interaction and anchoring between all the components of the solid agglomerate, improving its mechanical strength. In addition, the pyrolysis of the solid agglomerate promotes its drying and pre-reduction, increasing its calorific value and preparing it for use in blast furnaces.

Preferably, at least one source of carbonis at least one of the following: biocarbon, coal and/or metallurgical coal. For the purposes of this description, biocarbon means any charcoal of plant origin produced according to substantially sustainable standards. Preferably, this biocarbon has a low inorganic content (less than 1%).

Preferably, at least one source of calciumis a source of calcium oxide from at least one of the following: primary sources of calcium (limestone) or calcium-containing steel waste.

Preferably, at least one binderis an organic binder, such as starch.

Preferably, the mixing stepis carried out with 60 to 90% by mass of source of carbon. More preferably, the step of mixingis carried out with 60 to 80% by mass of source of carbon. Preferably, source of carbonis formed with up to 70% by mass of biocarbon and between 30 and 100% by mass of coal.

Preferably, the mixing stepis carried out with 0 to 10% by mass of at least one binder. More preferably, the mixing stepis carried out with 5 to 10% by mass of at least one binder.

Preferably, the step of mixingcomprises mixing 10 to 40% by mass of at least one source of calcium. More preferably, the step of mixingcomprises mixing 25 to 35% by mass of at least one source of calcium. More preferably, the step of mixingcomprises mixing 27 to 32% by mass of at least one source of calcium.

The present invention additionally provides a carbonized solid agglomerate for use in a blast furnace, comprising in its composition: at least one source of carbon; at least one source of calcium; and at least one binder; wherein, after mechanical shapingof the solid agglomerate, the solid agglomerate is subjected to a pyrolyzing stepat a temperature greater than or equal to 600° C. and less than 800° C.; wherein the solid agglomerate comprises 25 to 35% by mass of at least one source of calcium.

Once it has undergone mechanical shaping, the shaped agglomerategoes through a pyrolysis stageat a temperature preferably between 600° C. and 800° C. More preferably, the pyrolyzing stepis carried out at a temperature greater than or equal to 600° C. and less than 700° C. Optionally, the pyrolyzing stepis carried out at a temperature greater than or equal to 700° C. and less than 800° C.

Optionally, before pyrolyzingthe agglomerate, the shaped agglomerateis driedin an oven at 105° C. for two hours with the humidity inside the oven being less than 1%.