Coking solid agglomerates and method for producing same

Abstract

The invention relates to a solid agglomerate for use in a steelmaking furnace. In this case, the invention provides a coking solid agglomerate for use in a steel furnace, the composition of which comprises biochar, mineral coal and at least one binder, in which, after mechanical shaping of the solid agglomerate, it is subjected to a pyrolysis stage at a temperature greater than or equal to 700 DEG C and less than 800 DEG C. The invention also provides a preparation method of the coking solid agglomerate.

Description

Technical Field

[0001] The present invention relates to solid agglomerates. More specifically, the present invention relates to solid agglomerates for use in steelmaking furnaces. Background Art

[0002] One of the main functions of a metallurgical furnace is iron reduction, in which iron Fe is separated from its ore Fe2O3. This separation is achieved by chemical reduction, which involves separating the metal from its oxide and using a reducing agent to do so. This reducing agent is a material that must be more attractive to oxygen than the metal to be reduced under the operating conditions. The main reducing agent used in the steel industry is coke from mineral coal.

[0003] The steel industry heavily relies on metallurgical coal, which accounts for a large proportion of the final cost of the steel produced. The mineral coal used for integrated coke-making steelmaking is called coking coal, which is the basic material for reducing iron ore to metallic iron because it combines with oxygen to produce carbon dioxide, iron, and slag.

[0004] The type of coal commonly used in steelmaking is bituminous coal (soft coal) (coking coal) that forms solid lumps when heated; on the other hand, if it does not soften or agglomerate when heated, it is called non-coking coal.

[0005] Today, the use of agglomerates in the steel industry has become increasingly common. The agglomeration method includes grouping fine-grained materials with the aim of obtaining a larger product by using a binder. Through this process, high-quality metal agglomerates or coal briquettes can be obtained, for example, using small particle size grades that are usually discarded. In some cases, coal briquettes can replace coking coal and metal agglomerates can replace iron ore.

[0006] Among different agglomeration methods, the coal briquetting technology is taking its place in the industry. This technology can be used for both mineral coal and plant coal and generally includes the following steps: (i) size balancing of coal or biomass particles; (ii) mixing of a binder (agglomerant); (iii) mechanical compaction; and (iv) drying of the briquettes. The following documents describe examples of coal briquettes and their respective production methods.

[0007] For example, document US8585786B2 describes a method and system for briquetting solid fuels (such as coal). In this document, the solid fuel is conveyed through a continuous feed solid fuel treatment device, treated with electromagnetic energy, and briquetted after treatment.

[0008] Document WO2014098413A1 describes a coal briquette and a method for manufacturing the same. The method for manufacturing the coal briquette includes the following steps: (i) supplying pulverized coal, (ii) preparing a mixture obtained by mixing 1 to 5 parts by weight of a hardening agent and 5 to 15 parts by weight of a binder with 100 parts by weight of pulverized coal, and (iii) molding the mixture. In the pulverized coal supply stage, the pulverized coal contains (i) low-rank coal in an amount greater than 0 and not greater than 50% by weight and (ii) the balance of coal ash. The low-rank coal has a volatile component (dry basis) of 25% to 40% by weight and a crucible swelling number greater than 0 and less than 3.

[0009] Document WO2013152959A1 describes a method for producing a briquette containing coal, in which coal is mixed with a binder system in the presence of introduced steam, and the obtained mixture is subjected to pressing to form a briquette. Here, at least one of the steps: (i) drying the carbon carrier before mixing, (ii) setting the temperature of the carbon carrier to be mixed with the binder system within a predetermined temperature range before mixing, (iii) heat-treating the briquette after pressing by direct or indirect interaction with superheated steam. The obtained residual steam is used as at least a part of the steam introduced during mixing.

[0010] Document AU2008203855B2 describes a method for forming a briquette containing low-rank coal and an aggregate material, characterized in that it includes: drying a low-rank coal feed to produce dry coal having a moisture content between 8% and 16% by weight; mixing the dry coal with the aggregate material; and compacting the dry coal and aggregate material mixture into a briquette.

[0011] As described above, coal briquettes can be used in a method for reducing iron ore or its agglomerates in a steelmaking furnace. For example, document WO2011108466A1 describes a method for producing iron-coke by carbonizing an agglomerate containing mineral coal and iron ore. This method produces iron-coke, which is more reactive with CO2 in a blast furnace than the coke contained therein. The iron-coke production method in document WO2011108466A1 includes carbonizing a mixture composed of mineral coal and iron ore at a temperature higher than 800 °C to produce iron-coke.

[0012] The method in document WO2011108466A1 is not ecologically sustainable because it requires a large amount of energy to carbonize the agglomerate and does not provide for the use of renewable carbon materials.

[0013] The present invention solves the problems described in the prior art in a simple and efficient manner. Summary of the Invention

[0014] A first object of the present invention is to provide a coking solid agglomerate for use in a steel furnace and a method for manufacturing the same, in which the coking method is carried out at a relatively low temperature.

[0015] A second object of the present invention is to provide a coking solid agglomerate for use in a steel furnace and a method for manufacturing the same, which uses a reasonable amount of biochar, thereby increasing the ecological sustainability of the fuel.

[0016] To achieve the above object, the present invention provides a coking solid agglomerate for use in a steel furnace, which comprises biochar, mineral coal and at least one binder. After the solid agglomerate is mechanically formed, it is subjected to a pyrolysis stage at a temperature of greater than or equal to 700 °C and less than 800 °C.

[0017] The present invention also provides a method for manufacturing a coking solid agglomerate for use in a steelmaking furnace, which comprises the following steps: (i) mixing biochar, mineral coal and at least one binder, (ii) mechanically forming the mixture of biochar, mineral coal and at least one binder to form a solid agglomerate, and (iii) pyrolyzing the solid agglomerate at a temperature of greater than or equal to 700 °C and less than 800 °C. Detailed Description

[0018] First of all, it should be noted that the following description will be based on the preferred embodiments of the present invention. However, it is visible to those skilled in the art that the present invention is not limited to this specific embodiment.

[0019] The present invention provides a coking solid agglomerate for use in a steel furnace, which comprises biochar, mineral coal and at least one binder in its composition. For the purposes of this description, biochar refers to any plant-derived charcoal produced according to substantially sustainable criteria. Preferably, the biochar has a low inorganic content (less than 1%).

[0020] Once it has undergone mechanical forming, the solid agglomerate undergoes a pyrolysis process at a temperature of greater than or equal to 700 °C and less than 800 °C. This heat treatment cokes the carbonaceous materials in the mixture and increases the interaction and anchoring between all components of the solid agglomerate, thereby improving its mechanical strength. In addition, the pyrolysis of the solid agglomerate promotes its drying and pre-reduction, thereby increasing its calorific value and making it ready for use in a steel furnace.

[0021] Preferably, the pyrolysis of the solid agglomerate is carried out in a rotary cylindrical reactor.

[0022] Preferably, the solid agglomerate of the present invention comprises 10-75% by mass of biochar. More preferably, the solid agglomerate of the present invention comprises 50-65% by weight of biochar.

[0023] Preferably, the solid agglomerates of the present invention contain 25-90% by mass of mineral coal. More preferably, the solid agglomerates of the present invention contain 25-50% by weight of mineral coal.

[0024] Preferably, the solid agglomerates of the present invention contain 5-10% by mass of a binder, which has the function of keeping the compounds of the solid agglomerates bound together. The use of the binder also allows the use of compounds with smaller grain sizes in the composition of the solid agglomerates.

[0025] Optionally, the solid agglomerates of the present invention further contain 5-15% by weight of an iron-based compound, such as iron oxide or metallic iron. Mixing the iron-based compound with the agglomerates produces iron-coke agglomerates. As is well known, due to the catalytic action of the iron content in the iron-coke, the reaction of the carbonaceous material starts at a lower temperature than that of conventional coke. Therefore, when the iron-coke is used as a charge in a steelmaking furnace, a reduction effect on the reductant ratio (RAR) can be expected by reducing the temperature in the heat reserve zone.

[0026] The present invention also provides a method for manufacturing a coking solid agglomerate for use in a steelmaking furnace, comprising the steps of: (i) mixing biochar, mineral coal, and at least one binder, (ii) mechanically forming the mixture of biochar, mineral coal, and at least one binder to form solid agglomerates, and (iii) pyrolyzing the solid agglomerates at a temperature greater than or equal to 700°C and less than 800°C.

[0027] Preferably, the mixing stage is carried out with 10-75% by mass of biochar. More preferably, the mixing stage is carried out with 50-65% by mass of biochar.

[0028] Preferably, the mixing stage is carried out with 25-90% by mass of mineral coal. More preferably, the mixing stage is carried out with 25-50% by mass of mineral coal.

[0029] Preferably, the mixing stage is carried out with 5-10% by mass of the binder.

[0030] Optionally, the mixing step also involves mixing 5-15% by mass of an iron-based compound such as iron oxide or metallic iron to form iron-coke agglomerates.

[0031] The solid agglomerates and their manufacturing method according to the present invention have a mass yield of 95%, while the agglomerates of the prior art have a mass yield of about 70%. In addition, significant energy savings in the manufacturing method are achieved at a temperature below 800°C.

[0032] The coking solid agglomerates of the present invention can be used, for example, in blast furnaces, sintering furnaces, and coking plants. The solid agglomerates containing iron (iron-coke) can be used, for example, to replace small coke in blast furnaces.

[0033] Accordingly, as described above, the present invention provides a coking solid agglomerate for use in a steel furnace and a method for manufacturing the same, wherein the coking process is carried out at a relatively low temperature. Additionally, a reasonable amount of biochar is used in the agglomerate and in the manufacturing method, thereby increasing the ecological sustainability of the fuel and reducing CO2 emissions.

[0034] Many variations are allowed within the scope of protection of this request. This strengthens the fact that the present invention is not limited to the specific configurations / embodiments described above.

Claims

1. A coking solid agglomerate for use in a steelmaking furnace, characterized in that its composition comprises biochar, mineral coal and at least one binder, wherein, After the mechanical shaping of the solid agglomerate, it undergoes a pyrolysis stage at a temperature of at least 700 °C and less than 800 °C.

2. The solid agglomerate according to claim 1, characterized in that it contains 10 - 75% by mass of biochar.

3. The solid agglomerate according to claim 1 or 2, characterized in that it contains 25 - 90% by mass of mineral coal.

4. The solid agglomerate according to any one of claims 1 to 3, characterized in that it contains 5 - 10% by mass of binder.

5. The solid agglomerate according to any one of claims 1 to 4, characterized in that it further contains 5 - 15% by mass of an iron-based compound.

6. The solid agglomerate according to claim 5, characterized in that the iron-based compound is at least one of iron oxide and metallic iron.

7. Method for manufacturing a coking solid agglomerate for use in a steel furnace, characterized in that, Comprising the following stages: Mixing biochar, mineral coal and at least one binder; Mechanically shaping the mixture of biochar, coal and at least one binder to form a solid agglomerate; and Pyrolyzing the solid agglomerate at a temperature of at least 700 °C and less than 800 °C.

8. The method according to claim 7, characterized in that the mixing step is carried out with 10 - 75% by mass of biochar.

9. The method according to claim 7 or 8, characterized in that the mixing step is carried out with 25 - 90% by mass of mineral coal.

10. The method according to any one of claims 7 to 9, characterized in that the mixing step is carried out with 5 - 10% by mass of binder.

11. The method according to any one of claims 7 to 10, characterized in that the mixing step further comprises mixing 5 - 15% by mass of an iron-based compound.