A pelletized ore and its preparation method and application

Abstract

The present application relates to the technical field of pellets, and specifically discloses a pellet, a preparation method thereof, and an application thereof. In the pellets disclosed in the present application, the sodium content is ≤0.031wt%, and the potassium content is ≤0.019wt%. The present application also provides a preparation method and application of the above-mentioned pellets. The present application uses a humic acid extract with a high humic acid content and a low alkali metal content as a binder to prepare pellets, which can obtain pellets with a high grade of valuable metals and high compressive strength; and the prepared pellets without the introduction of alkali metals will not, on the one hand, deteriorate the reduction expansion metallurgical properties of the pellets during the later blast furnace smelting process, and will have no effect on the blast furnace smelting process; on the other hand, it will not produce harmful substances and is environmentally friendly.

Description

Technical Field

[0001] The present application relates to the technical field of pelletized ore, and in particular to a pelletized ore and a preparation method and application thereof. Background Art

[0002] The steel industry is a key pillar of my country's economic development. With growing awareness of ultra-low emissions and carbon emissions reductions, the industry is placing higher demands on optimizing blast furnace charge structures. Pellets, a high-quality raw material essential for achieving this, are now making up an increasing portion of steel companies' blast furnace charge.

[0003] Currently, most pelletizing plants use inorganic bentonite as a pellet binder. However, production practice has shown that approximately 90% of the bentonite remains in the pellets after high-temperature roasting, significantly reducing the total iron grade. Adding organic binders to iron pellets improves the total iron grade of the pellets because the organic matter contained in them is completely decomposed and burned during the preheating and roasting process, leaving no inorganic residue. Consequently, major steel companies and research institutions at home and abroad have increased their research on the use of organic binders in pellet production. However, by the time the pellets are preheated, the organic binder has completely decomposed and burned, leaving the primary crystallization between the mineral particles insufficient to meet production requirements. This results in the preheated pellets easily breaking and pulverizing, generating large amounts of dust in the rotary kiln, which poses both operational and environmental hazards. Consequently, organic binders have not been widely used.

[0004] In recent years, some scientific researchers have developed a sodium humate binder composed of an organic and inorganic composite. The strength of the pellets prepared using the sodium humate binder can meet the production requirements, and the total iron grade of the finished pellets is higher than that of the pellets obtained with the same amount of bentonite added. However, since the sodium humate binder is extracted from lignite using NaOH, the Na element will be introduced during the extraction process; and studies have shown that the alkali metals (mainly Na and K) contained in the pellets will lower the softening temperature of the ore, causing the ore to melt and drip before it is fully reduced, increasing the direct reduction heat consumption in the lower part of the blast furnace; alkali metals will also cause abnormal expansion of the pellets, strengthen the gasification reaction ability of the coke, and cause the strength after the reaction to drop sharply and pulverize, causing the permeability of the material column to deteriorate seriously, endangering the smooth progress of the smelting process; and, liquid or solid alkali metals will adhere to the furnace lining, shortening the service life of the furnace lining. Therefore, when the sodium humate binder is added in a high amount to the pellets, the Na introduced by it will cause the pellets to melt and drip before it is fully reduced. + It will harm the production process and shorten the life of the blast furnace lining. In addition, for some iron oxide minerals with multiple metal elements, such as chromite, when sodium humate binder is used for agglomeration, the Na in the binder + It can easily form toxic sodium chromate with chromite, causing harm to on-site workers and the environment. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present application provides a pelletized ore and a preparation method and application thereof.

[0006] In a first aspect, the present application provides a pellet, wherein the sodium content in the pellet is ≤0.031 wt %, and the potassium content in the pellet is ≤0.019 wt %.

[0007] Preferably, the pellets have a reduction degree of ≥78.8%, a dripping temperature ≥1405° C., a remelting range ≥148° C., and a reduction expansion ratio ≤17.33%.

[0008] Furthermore, the sodium content in the pellets is ≤0.029wt%, the potassium content is ≤0.017wt%, the reduction degree is 84.4-87.7%, the dripping temperature is 1434-1483°C, the remelting range is 165-191°C, and the reduction expansion rate is ≤17.33%.

[0009] Preferably, the compressive strength of the pellets is ≥2763N / piece, and the total iron grade is ≥65.70%.

[0010] Preferably, the pellets are prepared by using humic acid extract as a binder; the performance parameters of the humic acid extract are: humic acid content ≥68.59%, total acid groups ≥5.05mmol / g, Na ≤0.66wt%, and K ≤0.36wt%.

[0011] The preparation method of the humic acid extract used in this application specifically comprises the following steps:

[0012] Low-rank lignite or weathered coal is used as raw material, 20-50wt% triethanolamine aqueous solution is used as extracting liquid, and the reaction is carried out at a temperature of 40-70°C for 1-3 hours. After the reaction is completed, the reaction liquid is filtered, and the filtrate is dried and ground to obtain the humic acid extract; the humic acid content in the raw material is ≥45wt%.

[0013] The humic acid extract used in this application is a composite binder. The organic matter contained in this binder decomposes and burns during the preheating and roasting of the metal oxide ore agglomerates. Compared to using inorganic binders, the inorganic matter remaining in the finished pellets after preheating and roasting is significantly less, resulting in a higher valuable metal grade in the resulting pellets than pellets prepared with inorganic binders.

[0014] In addition, since the humic acid binder contains functional groups that can chelate with metal elements, the binder can undergo chemical adsorption on the surface of metal oxide mineral particles. Compared with bentonite that only undergoes physical adsorption on the surface of metal oxide minerals, the finished pellets prepared with humic acid binder have better green strength.

[0015] Compared with organic binders, humic acid amine contains inorganic substances contained in the raw materials themselves. These inorganic substances can react with other oxidized minerals during the preheating and roasting of the pellets, producing a small amount of liquid phase at a lower temperature, which helps the crystallization and recrystallization process and improves the consolidation strength of the finished pellets.

[0016] Since humic acid binder does not introduce alkali metal elements, it will not deteriorate the reduction expansion properties of the pellets, will not affect the subsequent blast furnace smelting process, and will not form harmful substances with some polymetallic oxide minerals. It is an environmentally friendly and efficient binder.

[0017] In a second aspect, the present application provides a method for preparing the above-mentioned pellets, which specifically comprises the following steps:

[0018] The humic acid extract is added to the metal oxide ore raw material and mixed evenly, and then water is added for pre-grinding. Then, green balls are obtained through pelletizing. The green balls are dried, preheated, and roasted in sequence to obtain the pelletized ore.

[0019] Preferably, the weight ratio of the humic acid extract to the metal oxide ore powder raw material is (0.5-1.5):100.

[0020] In a specific embodiment, the weight ratio of the humic acid extract to the metal oxide ore powder raw material can be 0.5:100, 1:100, or 1.5:100.

[0021] In some specific embodiments, the weight ratio of the humic acid extract to the metal oxide ore powder raw material can also be (0.5-1):100 or (1-1.5):100.

[0022] Through experimental analysis, it is known that the mechanical properties and metallurgical properties of the pellets can be further improved by controlling the weight ratio of the humic acid extract to the metal oxide ore powder raw material within the above range.

[0023] Preferably, the content of particles with a particle size of less than 200 mesh in the metal oxide ore powder raw material accounts for more than 90%.

[0024] Through experimental analysis, it is known that the mechanical properties and metallurgical properties of the pellets can be further improved by controlling the particle size of the metal oxide ore powder raw material within the above range.

[0025] Preferably, the drying step is as follows: drying the green balls obtained by pelletizing at 90-110° C. until the moisture content is below 2%.

[0026] Preferably, the preheating conditions are: preheating temperature 780-1000° C., preheating time 8-20 min; the calcination conditions are: calcination temperature 1050-1300° C., calcination time 8-20 min.

[0027] Furthermore, the preheating conditions are specifically as follows: preheating temperature 780-880° C., preheating time 15-20 min.

[0028] The inventors of the present application have conducted experiments and found that controlling the process parameters of drying, preheating and roasting to the above conditions can further improve the mechanical properties and metallurgical properties of the pellets.

[0029] In a third aspect, the present application provides the use of the above-mentioned pellets in preparing blast furnace charge.

[0030] In summary, the technical solution of this application has the following effects:

[0031] The present application utilizes a humic acid extract having performance parameters of humic acid content ≥ 68.59%, total acid groups ≥ 5.05 mmol / g, Na ≤ 0.66 wt%, and K ≤ 0.36 wt% as a binder to obtain finished pellets with high compressive strength and low alkali metal content. The pellets have a high degree of reduction, dripping temperature, and softening range, that is, the pellets provided by the present application have excellent metallurgical properties.

[0032] During the preparation of pellets, the present application further improves the mechanical and metallurgical properties of the pellets by screening the weight ratio between the raw materials, the particle size of the metal oxide ore powder raw materials and specific process parameters. DETAILED DESCRIPTION

[0033] The present application is further described in detail below in conjunction with examples, comparative examples and performance testing experiments. These examples should not be construed as limiting the scope of protection claimed in this application.

[0034] The sources and component contents of the iron ore concentrate used in this application are shown in Table 1 below.

[0035] Table 1 Source and component content of iron ore concentrate

[0036]

[0037]

[0038] Preparation Example

[0039] Preparation Example 1

[0040] Preparation Example 1 provides a humic acid binder.

[0041] The preparation method of humic acid binder is specifically as follows:

[0042] The lignite raw material (from Guizhou, the humic acid content was 45.3wt% as determined by the detection method specified in DB21 / T 3239-2020) was dried and ground to a particle size of less than 100 mesh, and 1kg of lignite powder was mixed with 5kg of 35wt% triethanolamine aqueous solution (liquid-solid ratio 5:1); the mixed liquid was placed in a reaction temperature environment of 55°C and heated in a water bath at a stirring speed of 400r / min for 1h; after the reaction, the reaction liquid was filtered to obtain a filtrate.

[0043] The filtrate was then dried at 75° C. to obtain a solid product, which was then ground using an agate mortar to a particle size of less than 100 mesh to obtain a humic acid binder having the following properties: a humic acid content of 69.83%, a total acid group of 5.54 mmol / g, a Na content of 0.64 wt%, a K content of 0.32 wt%, and a Si content of 3.32 wt%.

[0044] Preparation Example 2

[0045] Preparation Example 2 provides a humic acid binder.

[0046] The preparation method of humic acid binder is specifically as follows:

[0047] The lignite raw material (from Guizhou, the humic acid content was 45.3wt% as determined by the detection method specified in DB21 / T 3239-2020) was dried and ground to a particle size of less than 100 mesh, and 1kg of lignite powder was mixed with 5kg of 20wt% triethanolamine aqueous solution (liquid-solid ratio 5:1); the mixed liquid was placed in a reaction temperature environment of 55°C and heated in a water bath at a stirring speed of 400r / min for 1h; after the reaction, the reaction liquid was filtered to obtain a filtrate.

[0048] The filtrate was then dried at 75° C. to obtain a solid product, which was then ground using an agate mortar to a particle size of less than 100 mesh to obtain a humic acid binder having the following properties: a humic acid content of 68.59%, a total acid group of 5.05 mmol / g, a Na content of 0.60 wt%, a K content of 0.32 wt%, and a Si content of 5.48 wt%.

[0049] Preparation Example 3

[0050] Preparation Example 3 provides a humic acid binder.

[0051] The preparation method of humic acid extract is specifically as follows:

[0052] The lignite raw material (from Guizhou, the humic acid content was 45.3wt% as determined by the detection method specified in DB21 / T 3239-2020) was dried and ground to a particle size of less than 100 mesh, and 1kg of lignite powder was mixed with 5kg of 35wt% sodium hydroxide aqueous solution (liquid-solid ratio 5:1); the mixed liquid was placed in a reaction temperature environment of 55°C and heated in a water bath at a stirring speed of 400r / min for 1h; after the reaction, the reaction liquid was filtered to obtain a filtrate.

[0053] The filtrate was then dried at 75° C. to obtain a solid product, which was then ground using an agate mortar to a particle size of less than 100 mesh to obtain a humic acid binder having the following properties: a humic acid content of 71.83%, a total acid group of 5.61 mmol / g, a Na content of 5.02 wt%, a K content of 0.61 wt%, and a Si content of 8.20 wt%.

[0054] Example

[0055] Example 1-2

[0056] Examples 1-2 each provide an iron pellet.

[0057] The humic acid binder in Examples 1-2 is derived from Preparation Examples 1-2, respectively.

[0058] The preparation method of iron pellets in the above embodiment comprises the following specific steps:

[0059] Raw material mixing and milling pretreatment: Take 5.15 kg of magnetite concentrate (particle size of -200 mesh, accounting for 90.5%, raw material moisture 3%), add 50 g of humic acid binder, mix the two and add water to the mixture until the moisture content is 7%, and then use a mill for milling pretreatment for 5 minutes to obtain the raw material for pelletizing.

[0060] Preparation of iron ore pellets: The above-mentioned pelletizing raw materials that have been pre-treated by grinding are pelletized using a disc pelletizing machine. During the pelletizing process, the disc speed is maintained at 18r / min, the disc inclination angle is 45°, the pelletizing time is fixed at 12min, and the moisture content of the raw balls is controlled at about 8%. Finally, qualified raw balls with a diameter of 10-12mm are obtained.

[0061] The green balls are then dried at 100°C to constant weight, preheated (preheating temperature 820°C, preheating time 15 minutes) and roasted (roasting temperature 1250°C, roasting time 10 minutes) to obtain iron pellets.

[0062] Examples 3-6

[0063] Examples 3-6 each provide an iron pellet.

[0064] The difference between the above embodiment and embodiment 2 is that the weight ratio of the humic acid binder to the metal oxide ore powder raw material is different, as shown in Table 2.

[0065] Table 2 Weight ratio of humic acid binder to metal oxide ore powder raw material in Examples 2-6

[0066]

[0067]

[0068] Examples 7-11

[0069] Examples 7-11 each provide an iron pellet.

[0070] The difference between the above embodiment and embodiment 2 is that the preheating conditions are different (the dry bulbs obtained in embodiment 2 are used for preheating), specifically:

[0071] In Example 7, the preheating temperature is 750° C. and the preheating time is 20 min.

[0072] In Example 8, the preheating temperature is 780° C. and the preheating time is 20 min.

[0073] In Example 9, the preheating temperature is 880° C. and the preheating time is 15 minutes.

[0074] In Example 10, the preheating temperature is 920° C. and the preheating time is 10 min.

[0075] In Example 11, the preheating temperature is 1000° C. and the preheating time is 8 minutes.

[0076] Example 12

[0077] This embodiment provides an iron pellet.

[0078] The difference between this embodiment and embodiment 2 is that the raw material of the metal oxide ore powder is 5.15 kg of chromite concentrate powder (chromite concentrate powder with a particle size less than 200 mesh accounts for 94.2%, and the raw material moisture content is 3%).

[0079] Example 13

[0080] This embodiment provides an iron pellet.

[0081] The difference between this embodiment and embodiment 2 is that the raw material of the metal oxide ore powder is 5.15 kg of hematite concentrate powder (hematite concentrate powder with a particle size less than 200 mesh accounts for 96.4%, and the raw material moisture content is 3%).

[0082] Comparative Example

[0083] Comparative Example 1

[0084] This comparative example provides an iron pellet.

[0085] In this comparative example, CMC was used as an organic binder to prepare iron pellets. The specific method was as follows:

[0086] Raw material mixing and milling pretreatment: Take 5.15kg of magnetite concentrate (magnetite concentrate with a particle size of less than 200 mesh accounts for 90.5%, and the raw material moisture content is 3%), add 25g of CMC binder thereto, mix the two and add water to the mixture until the moisture content is 7%, and then use a mill for milling pretreatment for 5 minutes to obtain the raw material for pelletizing.

[0087] Preparation of iron ore pellets: The above-mentioned pelletizing raw materials that have been pre-treated by grinding are pelletized using a disc pelletizing machine. During the pelletizing process, the disc speed is maintained at 18r / min and the disc inclination angle is 45°; the pelletizing time is fixed at 12min, and the moisture content of the raw balls is controlled to be about 8%, and finally qualified raw balls with a diameter of 10-12mm are obtained; the raw balls are then dried to constant weight at 100°C, and after preheating (preheating temperature 950°C, preheating time 10min) and roasting (roasting temperature 1250°C, roasting time 10min), iron ore pellets are obtained.

[0088] Comparative Example 2

[0089] This comparative example provides an iron pellet.

[0090] In this comparative example, bentonite is used as an inorganic binder to prepare iron pellets. The specific method is as follows:

[0091] Raw material mixing and milling pretreatment: Take 5.15kg of magnetite concentrate (magnetite concentrate with a particle size less than 200 mesh accounts for 90.5%, and the raw material moisture content is 3%), add 50g of bentonite thereto, mix the two and add water to the mixture until the moisture content is 7%, and then use a mill for milling pretreatment for 5 minutes to obtain the raw material for pelletizing.

[0092] Preparation of iron ore pellets: The above-mentioned pelletizing raw materials that have been pre-treated by grinding are pelletized using a disc pelletizing machine. During the pelletizing process, the disc speed is maintained at 18r / min and the disc inclination angle is 45°; the pelletizing time is fixed at 12min, and the moisture content of the raw balls is controlled to be about 8%, and finally qualified raw balls with a diameter of 10-12mm are obtained; the raw balls are then dried to constant weight at 100°C, and after preheating (preheating temperature 950°C, preheating time 10min) and roasting (roasting temperature 1250°C, roasting time 10min), iron ore pellets are obtained.

[0093] Comparative Example 3

[0094] This comparative example provides an iron pellet.

[0095] In this comparative example, sodium humate binder (purchased from Yichun Zhongxiang Biotechnology Co., Ltd.) was used as a composite binder to prepare iron pellets. The specific method is as follows:

[0096] Raw material mixing and milling pretreatment: Take 5.15kg of magnetite concentrate (magnetite concentrate with a particle size less than 200 mesh accounts for 90.5%, and the raw material moisture content is 3%), add 50g of sodium humate binder, mix the two and add water to the mixture until the moisture content is 7%, and then use a mill for milling pretreatment for 5 minutes to obtain the raw material for pelletizing.

[0097] Preparation of iron ore pellets: The above-mentioned pelletizing raw materials that have been pre-treated by grinding are pelletized using a disc pelletizing machine. During the pelletizing process, the disc speed is maintained at 18r / min and the disc inclination angle is 45°; the pelletizing time is fixed at 12min, and the moisture content of the raw balls is controlled to be about 8%, and finally qualified raw balls with a diameter of 10-12mm are obtained; the raw balls are then dried to constant weight at 100°C, and after preheating (preheating temperature 950°C, preheating time 10min) and roasting (roasting temperature 1250°C, roasting time 10min), iron ore pellets are obtained.

[0098] Comparative Example 4

[0099] Comparative Example 4 provides an iron pellet.

[0100] The difference between this comparative example and Example 2 is that the humic acid binder is derived from Preparation Example 3.

[0101] Performance testing

[0102] The properties of the green balls, preheated balls and finished iron pellets in Examples 1-13 and Comparative Examples 1-4 were tested according to the following test methods.

[0103] (1) Drop strength of green balls: Select green balls of the same diameter (10-12 mm, based on the average value of the qualified ball diameter d ± 0.5 mm) and let them fall freely from a height of 0.5 m onto a 10 mm thick steel plate. Repeat the process until the green balls show obvious cracks or break. The number of times they fall until they break is the drop strength, and the average number of drops for 10 balls is used as the drop strength index.

[0104] Test results: as shown in Table 3.

[0105] (2) Compressive strength of green balls and finished iron ore pellets: The compressive strength of green balls and finished iron ore pellets was tested with reference to the determination method of GB / T14201-1993.

[0106] Test results: as shown in Table 3.

[0107] (3) TFe grade in pellets: The TFe grade of finished iron pellets was tested with reference to the determination method in GB / T 6730.6-2016.

[0108] Test results: as shown in Table 3.

[0109] (4) Contents of Na and K in pellets: The contents of Na, K, and Si in humic acid extracts were determined according to the detection method specified in MT / T 1014 “Determination of trace elements—Inductively coupled plasma atomic emission spectrometry”.

[0110] Test results: as shown in Table 3.

[0111] (5) Metallurgical properties of pellets: GB / T13241-91 is used to test the reducibility of pellets, and GB / T34211-2017 is used to test the soft melting performance of pellets.

[0112] Test results: as shown in Table 4.

[0113] Table 3 Performance test results of green balls, preheated balls and iron pellets in Examples 1-13 and Comparative Examples 1-4

[0114]

[0115]

[0116] Table 4 Metallurgical properties test results of iron pellets in Examples 1-13 and Comparative Examples 1-4

[0117]

[0118] In combination with Table 3 and Table 4, according to the test results of Examples 1-13 and Comparative Examples 1-4, it can be seen that the present application uses a humic acid extract having performance parameters of humic acid content ≥68.59%, total acid groups ≥5.05 mmol / g, Na ≤0.66 wt%, and K ≤0.36 wt% as a binder to obtain finished pellets with high compressive strength and low alkali metal content, and the pellets have a high degree of reduction, dripping temperature and remelting range, that is, the pellets provided by the present application have excellent metallurgical properties.

[0119] In the process of preparing pellets in Comparative Examples 1-4, an organic binder CMC, an inorganic binder bentonite, or a sodium humate binder was selected to prepare the pellets. A relatively high content of metallic sodium was introduced into the finished pellets, which reduced the reduction degree and softening temperature of the pellets and worsened the reduction expansion of the pellets. This may cause the ore to melt and drip before it is fully reduced, increasing the direct reduction heat consumption in the lower part of the blast furnace, thereby limiting the application of the pellets.

[0120] By comparing the test results of Example 2 with those of Examples 3-6, in the process of preparing pellets, the present application further improves the compressive strength and metallurgical properties of the pellets by controlling the weight ratio of the humic acid binder to the metal oxide ore powder raw material to (0.5-1.5):100.

[0121] Comparing the test results of Example 2 with those of Examples 7-11, the present invention improves the compressive strength and metallurgical properties of the pellets by controlling the preheating conditions to: 780-1000°C for a preheating time of 8-20 minutes. Furthermore, the present invention controls the preheating temperature to 780-880°C for a preheating time of 15-20 minutes.

[0122] Combined with the test results of Example 2 and Examples 12-13, the present application uses magnetite concentrate, chromite concentrate powder, and hematite concentrate powder as metal oxide ore raw materials, and uses the provided humic acid amine as a binder for preparing pellets, and can obtain high-quality iron pellets.

[0123] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A pelletized ore, characterized in that: The sodium content of the pellets is ≤0.031wt%, and the potassium content is ≤0.019wt%. The reduction degree of the pellets is ≥78.8%, the dripping temperature is ≥1405°C, the remelting range is ≥148°C, and the reduction expansion rate is ≤17.33%. The pellets are prepared by using ammonium humate as a binder; the performance parameters of the ammonium humate are: humic acid content ≥ 68.59%, total acid groups ≥ 5.05 mmol / g, Na ≤ 0.66 wt%, K ≤ 0.36 wt%; The method for preparing the pellets specifically comprises the following steps: The ammonium humate is added to the metal oxide ore powder raw material and mixed evenly, and then water is added for pre-grinding treatment, and then green balls are obtained through pelletizing. The green balls are then dried, preheated, and roasted in sequence to obtain the pellets. The weight ratio of the ammonium humate to the metal oxide ore powder raw material is (0.5-1.5):

100.

2. The pelletized ore according to claim 1, characterized in that: The sodium content in the pellets is ≤0.029wt%, the potassium content is ≤0.017wt%, the reduction degree is 84.4-87.7%, the dripping temperature is 1434-1483°C, the soft melting range is 165-191°C, and the reduction expansion rate is ≤17.33%.

3. The method for preparing pellets according to any one of claims 1 to 2, characterized in that: The specific steps include: The ammonium humate is added to the metal oxide ore powder raw material and mixed evenly, and then water is added for pre-grinding treatment, and then green balls are obtained through pelletizing. The green balls are dried, preheated, and roasted in sequence to obtain the pellets.

4. The method for preparing pellets according to claim 3, wherein: The specific drying step is: drying the green balls obtained by ball making at 90-110° C. until the moisture content is below 2%.

5. The method for preparing pellets according to claim 3, characterized in that: The specific preheating conditions are: preheating temperature 780-1000° C., preheating time 8-20 min; the specific calcination conditions are: calcination temperature 1050-1300° C., calcination time 8-20 min.

6. The method for preparing pellets according to claim 5, characterized in that: The preheating conditions are specifically: preheating temperature 780-880° C., and preheating time 15-20 min.

7. Use of the pellets according to any one of claims 1 to 2 in preparing blast furnace charge.

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