JP2022033594A - Method for manufacturing sintered ore - Google Patents

Abstract

To provide a method for manufacturing a sintered ore, capable of post-adding a coagulation material in a step of granulating a sintering raw material while together using a low flammable carbonaceous material and a high flammable carbonaceous material as the coagulation material and improving a sintering yield by a preferable mixing ratio of the high flammable carbonaceous material to the total coagulation material (a preferable mixing ratio of the low flammable carbonaceous material to the high flammable carbonaceous material).SOLUTION: A low flammable carbonaceous material consisting of at least one of coke breeze and anthracite and a high flammable carbonaceous material being a carbonaceous material having a combustion start temperature lower than that of the low flammable carbonaceous material are used as the coagulation material of a sintering raw material. The mass ratio of the carbon content of the high flammable carbonaceous material to that of the coagulation material is 25-75 mass%, and at least one of the low flammable carbonaceous material and the high flammable carbonaceous material is added in the latter half of the step of granulating the sintering raw material.SELECTED DRAWING: Figure 2

Description

The present invention is a method for producing a sinter for producing a sinter for a blast furnace raw material, and in particular, a highly combustible carbonaceous material having a lower combustion start temperature than coke and smokeless coal is used as a coagulant (coal material). Regarding the manufacturing method of sinter.

Currently, the main raw material for blast furnace pig iron is sinter. Sintered ore is usually produced as follows. First, as raw materials (sintered raw materials) for sintering ore production, iron raw materials such as iron ore (powder), iron-containing miscellaneous raw materials such as scale and iron-making dust, MgO-containing auxiliary materials such as sinter, and CaO-containing limestone. A by-material, return ore, carbonaceous material (condensing material) as a fuel for sintering (condensing) the sintered ore by heat of combustion, and the like are mixed at a predetermined ratio. The mixed compounded raw material is granulated to obtain a compounded raw material granulated product. Next, the compounded raw material granulated product is mounted on a pallet (sintered pallet) of a downward suction type dwightroid (DL) type sintering machine from a hopper to form a packed raw material (sintered packed bed). do. The charcoal material in the packed bed is ignited by an ignition furnace (igniter) from the upper part (surface) of the formed packed bed. Then, air is sucked from below the pallet while continuously moving the pallet. Oxygen is supplied into the packed bed of the raw material by suction, combustion of the carbonaceous material in the packed bed of the raw material proceeds from the upper part to the lower part, and the packed bed of the raw material is sequentially sintered by the combustion heat of the carbonaceous material. The sintered portion (sintered cake) obtained by sintering is sintered to a predetermined particle size by pulverization, sieving, etc., and becomes a sintered ore which is a raw material of a blast furnace.

Coke and anthracite are mainly used as the carbonaceous material (condensing material) for sintering. The coke for sintering is a coke having a particle size unsuitable for use in a blast furnace (usually 40 mm or less) crushed to 3 mm or less suitable for use in sintering in the process of producing coke for a blast furnace. Sintering is also called powder coke as opposed to lump coke for blast furnace. Anthracite is one of the categories (brown coal, bituminous coal, anthracite) given to coal, and is the most carbonized coal. Coal with a fuel ratio (fixed carbon / volatile content (mass ratio)) of 4 or more, or simply coal with a carbon content of 90% by mass or more, is classified as anthracite.

Various methods for producing sinter have been proposed in order to produce sinter suitable as a raw material for blast furnaces. For example, Patent Document 1 states that in the production of sintered ore, low-temperature combustion solid fuel (sub-bituminous charcoal, lignite, or a mixture of sub-bituminous charcoal and lignite) having a combustion reaction start temperature of less than 450 ° C. is about 800 ° C. A method for producing a sintered ore using a solid fuel containing 10 mass% or more of char) obtained by carbonization at a relatively low temperature is disclosed. By using the low temperature combustion solid fuel as a solid fuel together with coke breeze, anthracite or carbon-containing dust, the combustibility of the solid fuel is substantially improved and the productivity is improved.

Patent Document 2 and Patent Document 3 disclose a technique for post-adding a carbonaceous material (coagulant) (coal material post-addition sintering method). The post-carbonation addition sintering method is a method of granulating a sintering material other than the carbon material, or after granulating the sintering material other than the carbon material, and then adding the carbon material to the granulated material of the sintering material other than the carbon material. Is a technique for producing a sintered raw material granulated product by adding the above.

Patent Document 2 discloses a post-addition sintering method for a coal material using a coal material having a volatile content of 10 mass% or less as the coal material, and even when a coal char obtained by thermally decomposing brown coal or the like is used, granulation is performed. It is possible to obtain a sinter material that can increase the grain size of the particles and improve the combustibility of the coal material. By producing the sinter using the obtained sinter material, the combustion yield and production rate of the sinter can be obtained. It is stated that it can be enhanced.

Patent Document 3 discloses a post-additional sinter method for coal using coal having a logger index of 10 or less as a raw material for sintering coal, and NOx generated when sinter is produced. It is described that the amount of emissions can be reduced and the raw material for the sintering coal can be selected simply by calculating the logger index of coal without producing the sintering coal from coal.

International release WO2010-106756 Japanese Unexamined Patent Publication No. 2018-3081 Japanese Unexamined Patent Publication No. 2020-56086

As described above, Patent Document 1 discloses a technique of using a low-temperature combustion solid fuel together with coke or anthracite as a solid fuel. Further, Patent Documents 2 and 3 disclose a method for sintering after adding carbonaceous material. However, until now, coke and / and anthracite (coke and anthracite are classified as low-combustible carbonaceous materials described later) and high-combustible carbonaceous materials having a lower combustion start temperature than low-combustible carbonaceous materials have been coagulated. A method for producing sinter, in which a coagulant (part or all) is added afterwards in the granulation process of the sinter raw material, has not been studied.

The present invention is a step of sintering in a method for producing a sintered ore in which a coagulant is post-added in the granulation process of a sintering raw material while using a low-combustible carbonaceous material and a high-combustible carbonaceous material in combination as a coagulant. It is an object of the present invention to present a preferable compounding ratio of a highly combustible carbonaceous material (a preferable compounding ratio of a low combustible carbonaceous material and a highly combustible carbonaceous material) with respect to the total coagulant that enables improvement of retention.

(1) High combustible charcoal, which is a low combustible coal material composed of at least one of coke breeze and anthracite, and a charcoal material having a lower combustion start temperature than the low combustible coal material, as the coagulant of the sintered raw material. Using wood,
The carbon content of the highly combustible carbonaceous material has a mass ratio of 25% by mass to 75% by mass with respect to the carbon content of the coagulating material.
A method for producing a sinter, in which at least one of the low-combustible carbonaceous material and the high-combustible carbonaceous material is added in the latter half of the granulation step of the sintered raw material.
(2) Described in (1), as the sintering raw material, a low-oxidation iron-based raw material, which is an iron-based raw material containing metallic iron or divalent iron ions, is blended in an amount of 2% by mass or more with respect to the all-new raw material. How to make sinter.

According to the present invention, when a low-combustible carbonaceous material and a high-combustible carbonaceous material are used in combination as a coagulant, the carbon content of the high-combustible carbonaceous material is 25% by mass in mass ratio with respect to the carbon content of the coagulant. The yield of sintering can be improved by adding at least one of the low-combustible carbonaceous material and the high-combustible carbonaceous material in an amount of about 75% by mass in the latter half of the granulation step of the sintering raw material.

It is a schematic explanatory drawing explaining the firing state in a sintered packed bed. It is a figure which shows the relationship between the blending ratio of lignite char and coke breeze, and the sintering heat pattern. It is a figure which shows the experimental result of Test 1. It is a figure which shows the experimental result of the test 2. It is a figure which shows the experimental result of the test 3. It is a figure which shows the experimental result of the test 4.

First, a low-combustible carbonaceous material and a high-combustible carbonaceous material used as raw materials (sintered raw materials) for producing sinter, and low-oxidation iron-based raw materials will be described in order, and then the embodiments of the present invention will be described. explain.

(Low combustible carbonaceous material and high combustible carbonaceous material)
The carbonaceous material (condensing material) of the sintered raw material is classified into a low combustible carbonaceous material and a high combustible carbonaceous material.
The low-combustible carbonaceous material is coke and anthracite, and the high-combustible carbonaceous material is a carbonaceous material having higher combustibility than the low-combustible carbonaceous material. Specifically, the low combustible coal material and the high combustible coal material are classified based on the combustion start temperature obtained by the differential thermal balance, and the low combustible coal material is a coal material exceeding 550 ° C and has high combustion. The sex charcoal material is a charcoal material having a temperature of 550 ° C. or lower.

Examples of the highly combustible coal material include coal char and biomass charcoal (such as Abra palm kernel shell charcoal and charcoal char produced by carbonizing wood). The ignition temperature of coke is about 670 ° C and the ignition temperature of smokeless coal is about 690 ° C, while the ignition temperature of coal char (semi-coke, brown coal char, and subbituminous coal char) is about 430 ° C to 550 ° C. The ignition temperature of biomass coal (Abra palm coke) is as low as about 470 ° C. Coal char and biomass charcoal (Abra palm kernel shell coal) have similar flammability because the ignition temperature is about the same.

Here, the coal char is a coal material (char) produced by carbonizing, for example, bituminous coal, lignite, and subbituminous coal having low cohesiveness at 700 to 900 ° C. as raw coal. The charcoal materials produced by carbonizing low-viscosity bituminous coal, lignite, and subbituminous coal are called semi-coke, lignite char, and subbituminous coal char, respectively. These coal materials are produced by carbonizing coal (including mixed coal) as a raw material in a pyrolysis furnace (for example, a rotary kiln).
Further, the biomass charcoal is a charcoal material produced by heat-treating biological resources (biomass) such as Abra palm kernel and wood as a material. Abra coconut husk charcoal (PKS charcoal) is a solid carbide produced by heat-treating (dry distillation) Abra coconut husk (Palm Kernel Shell). The method for producing PKS charcoal is described in JP-A-2014-218713 (Hara et al.), And details thereof will be omitted.

(Low-oxidation iron-based raw material)
The low-oxidation iron-based raw material contains at least one of metallic iron or ferrous ion and has an oxidation heat generating property. The mineral phase contains at least one of metallic iron (Fe), wustite (FeO), and magnetite (Fe _{3O 4 )} . Examples include scales (mill scales and scarfing scales generated at steelworks) and converter dust.
In the sintering process under high temperature, metallic iron (Fe), ustite (FeO), and magnetite (Fe 3O ₄ ) are oxidized, for example, metallic iron (Fe) and ustite (FeO) are magnetite _{(Fe 3 O} ). ₄ ) and hematite (Fe ₂ O ₃ ) are changed, and magnetite (Fe ₃ O ₄ ) is changed to hematite (Fe ₂ O ₃ ). Since these oxidation reactions are exothermic reactions, a low-oxidation iron-based raw material can also be used as an exothermic source.

In the method for producing a sinter of the present invention, a low combustible carbonaceous material and a high combustible carbonaceous material are used in combination as a coagulant as a sinter raw material, and the carbon content contained in the high combustible carbonaceous material is the total coagulant. The mass ratio is 25% by mass to 75% by mass with respect to the carbon content to be obtained, and at least one of a low combustible carbonaceous material and a high combustible carbonaceous material is added in the latter half of the granulation step of the sintering raw material. By using such a blending ratio and post-addition, the yield of sintered products is improved. The rationale is based on the examples described later. Here, the low-combustibility carbonaceous material used as the coagulant is composed of at least one of coke breeze and anthracite. Further, the highly combustible coal material used as a coagulant may be a mixture of one type of raw material or a mixture of a plurality of types of raw materials (for example, a mixture of a plurality of types of coal char, coal char and biomass charcoal). It may be a mixture, a coal charcoal produced from a mixed coking coal in which a plurality of coking coals are mixed, etc.).

In the present invention, as the coagulant, a high combustible carbonaceous material having a lower combustion start temperature than the low combustible carbonaceous material is used together with the conventional low combustible carbonaceous material (coke powder, anthracite). Since the combustion start temperature is different between the low combustible carbon material and the high combustible carbon material, the combustion position (combustion zone) of both is different in the sintering process in which sintering proceeds by downward suction. By burning multiple coal materials with different combustion characteristics in the sintering process within the range where the mixing ratio of the low combustible carbon material and the high combustible carbon material is appropriate, the combustion zone in the layer height direction of the sintered packed bed. The width of the combustion zone can be expanded and the extension of the high temperature holding time of the combustion zone is achieved.

Further, in the present invention, at least one of the low-combustible carbonaceous material and the high-combustible carbonaceous material is post-added in the granulation step (at least one of the low-combustible coal material and the high-combustible coal material to be post-added). , Hereinafter also referred to as post-added carbonaceous material). That is, in the granulation process of producing a granulated raw material (granulated material of a sintered raw material) from a sintered raw material using a granulator, first, the sintered raw material excluding the post-added carbonaceous material is first produced. Put it in a granulator, mix it, adjust the humidity, and start granulation. Subsequently, the post-added carbonaceous material is later put into the granulator (in the middle of the granulation process) to produce a sintered raw material granulated product. By adding the post-added carbonaceous material at an appropriate timing later, the post-added carbonaceous material is covered with the sintered raw material granulated product, that is, it is not included in the granulated material and adheres to the surface layer of the granulated material. Or it exists as a non-adherent independent grain. By using the sintered raw material granulated product (blended raw material granulated product) on which the post-added carbon material is outer, it is possible to adjust the timing of the combustion start of the post-added carbon material in the sintering step. The post-added carbonaceous material may be any one of a low combustible carbonaceous material and a high combustible carbonaceous material.

Post-addition in the granulation step is performed, for example, as follows. For granulation, a piston flow type tubular granulator whose central axis tilts downward toward the downstream side is used, and a small conveyor is inserted from the downstream outlet to a predetermined position inside the granulator. do. When the sintered raw material excluding the post-added carbonaceous material (hereinafter, also referred to as the post-added pre-added sintered raw material) is charged from the upstream inlet, the charged sintered raw material moves to the downstream side while being mixed and granulated. The post-added coal material is placed on a conveyor and carried from the downstream outlet of the granulator to the internal upstream side. The post-added carbonaceous material is added at a predetermined position to the granulated product of the post-addition pre-saturated raw material that has been granulated and moved from the upstream side in the granulator, and the entire sintered raw material is further granulated, and the downstream outlet. Is discharged as a sintered raw material granulated product (blended raw material granulated product).

The granulation time of the post-addition pre-sintered raw material until the post-addition carbonaceous material is added is 80% or more and 96% or less with respect to the total granulation time of the sintered raw material, that is, the timing of post-addition is granulated. The time is preferably in the range of 80% to 96% of the total granulation time of the sintered raw material in the step. If the post-addition is earlier than 80% of the total granulation time, it cannot be sufficiently avoided that the post-addition carbonaceous material is included in the granulated product. Further, if the post-addition is slower than 96% of the total granulation time, the granulation treatment of the post-added carbonaceous material becomes insufficient. Here, the total granulation time in the granulation step does not include the time (mixing time) in which the sintering raw material is simply mixed until it is charged into the granulator and water is added. In sintering, a drum mixer is mainly used, which is a constant velocity piston flow type. Therefore, the post-addition position can correspond to the distance in the machine length direction of the drum mixer.

Further, under the above-mentioned compounding ratio and post-addition timing conditions, an iron-based raw material containing metallic iron and / or divalent iron ions (low-oxidation iron-based raw material) is used as a sintering raw material for all new raw materials. It may be blended in an amount of 2% by mass or more. In the sintering process, metallic iron and divalent iron ions in the low-oxidation iron-based raw material are oxidized, and the heat of oxidation further improves the yield.

Hereinafter, the progress of the combustion reaction in the sintered packed bed will be described with reference to the drawings.
In FIG. 1, as a sintering raw material, a high combustible carbonaceous material (brown coal char, etc.) and a low oxidation degree iron source (mill scale, etc.) are used together with a conventional low combustible carbonaceous material (powder coke, etc.). It is explanatory drawing explaining the firing state in the sintered packed bed at the time of use. 1 (A) is a schematic diagram showing the state in the sintered packed bed at time t ₁ , FIG. 1 (B) is a schematic diagram showing the state in the sintered packed bed at time t ₂ , and time t ₂ is time t. It is the time after a predetermined time has elapsed from ₁ . Further, FIG. 1C corresponds the temperature and oxygen concentration distribution in the sintered packed bed in the layer height direction at time t2 to the position in the layer height direction in the sintered packed bed of _FIG . 1B. It is a figure shown by. It should be noted that each graph showing the temperature and oxygen concentration in FIG. 1C shows that the temperature and the concentration increase from the left to the right.

In the sintering step, combustion proceeds downward from the surface of the ignited sintered packed bed. As shown in FIG. 1 (A), the sintered packed bed being sintered is divided into three regions at the top and bottom in the layer height direction depending on the progress of sintering. Specifically, the sintered cake that has been sintered is on the upper layer side, the sintered raw material before sintering is on the lower layer side, and the combustion reaction of the coagulant and the low degree of oxidation are in the intermediate portion sandwiched between them. There is an oxidation (combustion) zone in which the oxidation reaction of the iron source occurs. As shown in FIGS. 1 (A) and 1 (B), sintering progresses with the passage of time (from time t ₁ to time t ₂ ), and the oxidation (combustion) zone descends.

As shown in FIG. 1 (B), the oxidation (combustion) zone is further divided into three regions A, B, and C in order from the lower side to the upper side in the layer height direction according to the progress of the combustion reaction and the oxidation reaction. .. In the region A, the combustion reaction of the highly combustible carbonaceous material mainly occurs, in the region B, the combustion reaction of the low combustible carbonaceous material mainly occurs, and in the region C, the oxidation reaction of the low-oxidation iron source occurs. Hereinafter, the combustion reaction and the progress of the oxidation reaction in the oxidation (combustion) zone will be described with reference to FIGS. 1 (B) and 1 (C).

When the oxidation (combustion) zone falls on the lower unsintered layer of sintered raw material, the highly combustible carbonaceous material having a low combustion start temperature among the coagulants first starts combustion and then disappears. That is, the lower surface of the oxidation (combustion) zone is the combustion start position of the highly combustible carbonaceous material, and the combustion range of the highly combustible carbonaceous material is the lower portion (A region) of the oxidation (combustion) zone. As shown in FIG. 1 (C), when the temperature in the sintered layer rises due to the combustion of the highly combustible carbonaceous material, the low combustible carbonaceous material having a high combustion start temperature starts combustion and then disappears. Since the low-combustible carbonaceous material starts burning later than the high-combustible carbonaceous material, the combustion range is the middle portion (B region) of the oxidation (combustion) zone which is the upper side of the A region. Here, as shown in FIG. 1 (C), in the region B, the combustion of the low combustible carbonaceous material creates a high temperature environment, but the combustion of the low combustible carbonaceous material consumes oxygen and generates CO. Since the atmosphere is reduced, the oxidation of the low-oxidation iron source is suppressed. In the upper part (C region) of the oxidation (combustion) zone, which is the upper side of the B region, the low combustible carbonaceous material burns and disappears, so that the consumption of oxygen in the atmosphere supplied from above decreases and CO Since the amount of oxygen generated is also reduced, the oxidation of the low-oxidation iron source is promoted, and the heat of oxidation is generated by this oxidation reaction.

In this way, a plurality of raw materials having different oxidation (combustion) conditions (two types of coagulants of low-combustible carbonaceous material and high-combustible carbonaceous material, and low-oxidation iron-based raw materials) are blended into the sintered raw material. As a result, multi-stage combustion can be realized as shown in the regions A to C of FIG. 1 (B), and the combustion and oxidation regions (oxidation (combustion) zone) in the layer height direction expand as the sintering progresses. .. As a result, the high temperature holding time at an arbitrary position in the layer height direction is extended, and the product yield is expected to be improved. In the above description, the case where the low-oxidation iron-based raw material is blended with the sintered raw material has been described, but even when the low-oxidation iron-based raw material is not blended, the low-combustibility carbonaceous material and the high-combustible carbonaceous material are not blended. With the two types of coagulant, it is possible to realize multi-stage combustion in regions A and B in FIG. 1 (B). Since the oxidation (combustion) region in the layer height direction is expanded as compared with the case where only low combustible carbonaceous material is used, it is expected that the product yield will be improved.

However, in order to realize multi-stage combustion in which the combustion of the high combustible carbon material and the combustion of the low combustible carbon material are continuous as described above, the mixing ratio of the low combustible carbon material and the high combustible carbon material is appropriate. Need to be. Therefore, the present inventors have burned the blending ratio (blending ratio) of the low-combustible carbonaceous material and the high-combustible carbonaceous material before carrying out the examples described later, which are the basis of the above-mentioned blending ratio and the timing of post-addition. A batch experiment was conducted to investigate the effect of the layering temperature on the change over time (hereinafter referred to as heat pattern). Hereinafter, the batch experiment will be described. In the batch experiment, coke breeze was used as the low combustible coal material and lignite char was used as the high combustible coal material.

In the batch experiment, a cylindrical pot with a diameter of 100 mm and a height of 160 mm was used. Five samples (blending raw materials) containing a coagulant with different blending ratios of coke breeze and lignite char (combined ratio based on carbon content mass ratio, which will be described later) were prepared, and each was sintered and the temperature inside the sintered layer. Was measured. The temperature was measured at a depth of 140 mm from the upper surface in the height direction of the sintered layer and at the center of the pot in the horizontal direction, and the heat pattern at the position inside the sintered layer was investigated.

FIG. 2 shows the heat pattern of each sample measured in the batch experiment.
As shown in FIG. 2, the case where the lignite char content is 0% and the lignite char content is 100% has a lower maximum temperature than the case where the lignite char content is 25% or more and 75% or less. , The high temperature holding time was short. As shown in the examples described later, when the blending ratio of the lignite char is less than 25%, the effect of improving the combustion front descent speed, which is the effect of blending the highly combustible coal material, cannot be obtained, and the blending ratio of the lignite char is increased. If it exceeds 75%, it is considered that the product yield is lowered due to the high-speed combustion peculiar to the highly combustible coal material.

Further, an important configuration of the present invention is to post-add the coagulant at the final stage of the granulation process. If the coagulant is collectively granulated with other sintering raw materials, it will be included in the adhered powder layer of the granulated material. If it is included, the start of combustion of the coagulant is controlled by the heat transfer time of the adhering powder layer, and the difference in the combustion characteristics of the coagulant does not become apparent. As a result of various studies, the present inventors have found that it is necessary to post-add at least one of two types of coagulant (low combustible carbonaceous material and high combustible carbonaceous material) in the granulation process. I found it. Also in the above-mentioned batch experiment, when one or more kinds of coagulants (low combustible carbonaceous material and / and high combustible carbonaceous material) are added afterwards and the granulated sintered raw material granulated product is fired, the product yield is obtained. Has been obtained to improve.

An example showing the basis for determining the carbonaceous material composition ratio of the present invention will be described. In addition, among the test cases performed in the tests 1 to 4 described later, the case where the yield is 74.5% or more is an example. The present invention is not limited to the following examples. For example, using anthracite as a low-combustible coal material has the same effect.

In the examples, it was verified by using a method commonly known as a sintering pot test. The sintering pot test is a test in which a sintering raw material (blending raw material) containing a carbonaceous material as a fuel is charged into a container of a predetermined size, ignited from the upper surface, and sucked downward to proceed with sintering. .. Unlike the Dwightroid (DL) type sintering machine, the sintering pot test device does not move the packed bed of the raw material by the pallet, but it is a test device that can simulate sintering by the DL type sintering machine. As the test, four tests 1 to 4 described later were performed. First, the raw materials used in the test and the test method will be described, and then each test will be described in order. The sintered raw material in which the raw materials are mixed at a predetermined ratio is referred to as a compounded raw material.

(material)
Table 1 shows the results of industrial analysis and elemental analysis of the low-combustible and high-combustible coal materials used in the test. As shown in Table 1, powdered coke was prepared as a low combustible coal material, and lignite char, subbituminous coal char and semi-coke were prepared as high combustible coal materials.

For low-oxidation iron-based raw materials, scales derived from the lower process of the steelworks were prepared. The components of the scale were total iron content: 74% by mass, ferric iron: 66% by mass (as FeO), and metallic iron content: 4% by mass.

(Ingredient composition)
Table 2 shows the compounding ratio of each raw material for the compounding raw material (hereinafter referred to as the standard compounding material) used as the standard in this test. As shown in Table 2, the standard compounding raw material does not contain a highly combustible carbonaceous material and scale, and only the low combustible carbonaceous material (powdered coke) shown in Table 1 is used as the carbonaceous material. In addition, iron ore A to E are iron ores from different production areas, and the mixing ratio of coke breeze and return ore is 100% by mass of new raw materials (iron ore, sardine, fresh lime, and limestone). It was set to 4.5% by mass and 15.0% by mass.

Details will be described later, but in Tests 1 to 4, the above-mentioned highly combustible carbonaceous material (see Table 1) and / or the above-mentioned scale is blended in a predetermined amount based on the reference compounding raw material in Table 2 (the compounding raw material (see Table 1). Hereinafter, the comparative compounding raw material) was appropriately compounded and the experiment was conducted.

When a highly combustible coal material is blended with a standard blended raw material, the industry of all coal materials (low combustible coal material and highly combustible coal material) contained in each blended raw material (standard blended raw material and comparative blended raw material). The blending ratio was adjusted by substituting the low-combustible coal material, which is the standard compounding material, with the high-combustible coal material so that the amount of carbon in the analysis was the same.
In addition, when the scale is blended with respect to the standard blended raw material, the iron ore D is replaced with the scale so that the mass is the same, and the total estimated calorific value in both blended raw materials is the same (blending). The calorific value of oxidation generated when FeO and metallic iron in the scale are oxidized to Fe ₂ O ₃ is equivalent to the calorific value of oxidation generated when the replaced low-combustible coke is completely burned. In), the blending ratio was adjusted to reduce the blending amount of low-combustible carbonaceous material (powdered coke). As specific numerical values, the calorific value when carbon, FeO and metallic iron were burned and oxidized to CO and Fe ₂ O ₃ was set to 394 kJ / mol, 135 kJ / mol and 412 kJ / mol per 1 mol of each substance.
Further, when blending both the highly combustible carbonaceous material and the scale, first, the above-mentioned blending ratio of the highly combustible carbonaceous material is adjusted, and then the blending ratio of the above-mentioned scale is adjusted, and the blending of each raw material is performed. The ratio was decided.

Regarding the compounded raw materials used in each test, the details of the compounding ratio of the raw materials will be described later. First, the test methods in Tests 1 to 3 and the method for evaluating the results will be described below.

(Granulation method)
A cylindrical batch drum mixer having a diameter of 600 mm and a length of 800 mm was used as the granulator. The compounding raw material was added from the upstream side of the granulator, mixed for 4 minutes, and then water was added (humidity control) and mixed for another 4 minutes for granulation. The amount of water added depends on the type of carbonaceous material to be blended. This is because the amount of water absorption differs depending on each carbonaceous material. Specifically, the external number of each compounded raw material is 7.0% by mass in the case of coke breeze and 7.6% in the case of highly combustible coal, and the value is determined by the compounding ratio of coke breeze and highly combustible coal. did. In addition, in the case of post-adding charcoal material (low combustible charcoal material and / and high combustible charcoal material) instead of batch granulation, a part of the compounding raw material excluding the post-added charcoal material is added for preparation. After wetting, the mixture was mixed for 3 minutes and 50 seconds, then the charcoal material to be added later was added, and the mixture was further mixed for 10 seconds to granulate. After the completion of a series of mixing treatments, the water content of the raw material was measured and the water content was confirmed. The granulation time in this case is 4 minutes after humidity control.

(Charging / ignition method)
The pot test device used was a cylindrical pot with a diameter of 300 mm and a height of 500 mm. The granulated compounded raw material was vertically charged without segregation, and the surface of the raw material packed bed was ignited for 1 minute (calorific value 25 MJ / raw material t) to have a layer height of 500 mm and fired. For the suction negative pressure during firing, the valve opening on the suction side of the blower was adjusted so that the measured value under the pot was constant at 1300 mmAq (12.7 kPa) from the start of ignition.

(Sintering time)
The sintering time was measured as follows. A thermocouple was inserted under the pot and the temperature of the exhaust gas was measured. In the sintering step, when the combustion zone reaches the bottom of the sintered layer, the exhaust gas temperature under the pot starts to rise, eventually reaches a peak, and decreases when the combustion of the carbonaceous material is completed. Three minutes after the exhaust gas temperature reached its peak, the suction of the blower was stopped, and the sintering was completed. The sintering time was defined as the time required from the start of ignition to the peak of the exhaust gas temperature.

(Yield)
Yield was measured as follows. After firing, the obtained sintered cake was dropped four times from a height of 2 m, and the mass was determined with a particle size of +5 mm (5 mm or more) excluding the bedding ore as a sintered product. The ratio (% by mass) of the sintered product to the mass of the sinter cake excluding the bedding ore was defined as the product yield (+ 5 mm%).

(Combustion front descent speed)
The combustion front descent rate (mm / min) was calculated by dividing the layer height of the raw material packed bed of 500 mm by the above-mentioned sintering time.

(Production rate)
The production rate was calculated by the following formula (1) based on the above-mentioned sintering time.
Production rate (t / d / m ² ) = product quantity (t) / pot bottom area (m ² ) / sintering time (day) ・ ・ ・ (1)

<< Test 1 >>
In Test 1, an experiment was conducted to verify the appropriate mixing ratio of the low-combustible carbonaceous material and the high-combustible carbonaceous material and the effect of post-addition.
Table 3 shows the compounding conditions used in Test 1. As shown in Table 3, five kinds of compounding raw materials (R ₀ , R ₂₅ , R ₅₀ , R ₇₅ , R ₁₀₀ ) having different compounding ratios of low combustible carbonaceous material and high combustible carbonaceous material were prepared. For the compounding raw materials R ₂₅ , R ₅₀ , R ₇₅ , and R ₁₀₀ , the lignite char shown in Table 1 is used for the highly combustible carbonaceous material, and the carbon content in the industrial analysis is based on the standard compounding material R ₀ in Table 2. The coke breeze is replaced with lignite char so that the amount is the same. Specifically, the composition ratio (carbon content mass ratio) of the lignite char in terms of carbon content with respect to the total carbon material is 0% by mass (Comparative Example 1 and Comparative Example 6) for R ₀ and 25 mass for R ₂₅ . % (Comparative Example 2 and Example 1), R ₅₀ is 50% by mass (Comparative Example 3 and Example 2), R ₇₅ is 75% by mass (Comparative Example 4 and Example 3), and R ₁₀₀ is 100% by mass (Comparative Example 4 and Example 3). It was referred to as Comparative Example 5). Regarding the four types of compounded raw materials (R ₀ , R ₂₅ , R ₅₀ , R ₇₅ ) including low combustible carbonaceous material (powdered coke), specifically, the case where all the raw materials are granulated at once (the case of granulating all the raw materials at once (R 0, R 25, R 50, R 75). Comparative Examples 1 to 4) and a case (Comparative Example 6 and Examples 1 to 3) in which only powdered coke was added afterwards to granulate the whole raw material were provided, and a total of 9 types of sintered raw material granulated products were provided. Was produced, and the above-mentioned pot test was conducted using each of the sintered raw material granulated products.

(Test result of test 1)
FIG. 3 shows the results of Test 1. In FIG. 3, the case where all the raw materials are granulated at once is shown by a white circle, and the case where the coke breeze is added afterwards is shown by a black circle.
As shown in FIG. 3, when the lignite char compounding ratio is 0% by mass, the case where the coke breeze is added afterwards has a lower product yield than the case of batch granulation of all raw materials, but the combustion front descent rate. As a result, the production rate has improved. In addition, when the blending ratio of lignite char is 25, 50, 75% by mass, that is, when both lignite char and powdered coke are blended, the product yield and the combustion front descent rate are improved, resulting in significant production. The rate has improved.

<< Test 2 >>
In Test 2, an experiment was conducted to verify the difference in effect depending on the type of carbonaceous material to be added later.
Table 4 shows the sintered raw material granulated product used in Test 2. Comparative Example 3 and Example 2 in Table 3 are reprinted in Table 3. As shown in Table 4, Experiments 4 and 5 were carried out in which the types of carbonaceous materials to be added afterwards were different, with the carbon content mass ratio being constant at 50%. Specifically, in Comparative Example 3 of Test 1, all the raw materials were collectively granulated, in Example 2, only powdered coke was post-added, and in Example 3, only lignite char was post-added, and Example 4 was carried out. In, both coke breeze and lignite char were post-added.

(Test result of test 2)
FIG. 4 shows the results of Test 2.
As shown in FIG. 4, compared with the case of batch granulation of all sintered raw materials (without post-addition), when only one or both of lignite char and coke breeze are post-added, the product yield and combustion front drop. Speed and production rate have improved.

<< Test 3 >>
In Test 3, an experiment was conducted to verify the effect of the difference in the amount of scale compounded when the scale was compounded as a raw material.
Table 5 shows the sintered raw material granulated product used in Test 3. Example 5 in Table 5 is reprinted in Table 4. As shown in Table 5, the carbon content mass ratio of the lignite char is kept constant at 50% (however, the reduction of the coke breeze due to the scale compounding is not considered), and the scale compounding is performed under the condition that both the coke breeze powder and the lignite char are added afterwards. The experiment was carried out by changing the amount to 0, 1, 2, 5% by mass. The scale is substituted with iron ore D in Table 2 and blended, and the scale blending amount is the blending ratio (internal number) when the new raw material is 100% by mass. In addition, as described in the column of low combustible charcoal material of blending raw material type and blending ratio of Examples 6 to 8, the powder coke blending ratio (blending amount) is set in consideration of the heat of oxidation of the scale. Adjustments were made to reduce the amount equivalent to the amount of compounding and the amount of heat. Specifically, compared to Example 5 in which the powder coke blending ratio (blending amount) was 50% (carbon content mass ratio), in Examples 6, 7 and 8, 49.94% and 49. It was set to 89% and 49.72%. The blending amount of the highly combustible carbonaceous material is the same in Examples 5 to 8. The numerical values shown in Table 6 are the total carbon of the low-combustible carbonaceous material and the high-combustible carbonaceous material with respect to the compounding ratio of the low-combustible carbonaceous material and the high-combustible carbonaceous material of Examples 5 to 8 shown in Table 5. It is a value calculated assuming that the fractional mass (total carbon content mass of the coagulant) is 100% by mass.

(Test result of test 3)
FIG. 5 shows the results of Test 3.
As shown in FIG. 5, the yield improved as the scale compounding amount increased. However, when the blending amount was 2% or more, the improvement effect became mild. On the other hand, the combustion front descent rate decreased slightly as the scale compounding amount increased, but the productivity became slightly higher when the scale compounding amount was 2% or more.

<< Test 4 >>
In Test 4, an experiment was conducted to perform comparative verification of highly combustible carbonaceous materials.
Table 7 shows the sintered raw material granulated product used in Test 4. Example 2 in Table 7 is a reprint of Tables 3 and 4. As shown in Table 7, under the condition that the carbon content mass ratio of the highly combustible carbonaceous material is 50% and the coke breeze is added afterwards, other than the experiment in which the highly combustible carbonaceous material is lignite charcoal (Example 2). The experiments of Example 9 in which the highly combustible coal grade was sub-bituminous charcoal char and Example 10 in which the highly combustible coal grade was semi-coke were carried out.

(Test result of test 4)
FIG. 6 shows the results of Test 4.
As shown in FIG. 6, when the subbituminous coal char or semi-coke was used as the highly combustible coal material, the yield was improved as compared with the case where the lignite char was used. Productivity was improved for subbituminous coal chars compared to using lignite chars, but decreased with combustion front descent rate for semi-coke.

Claims (2)

As the coagulant of the sintering raw material, a low combustible carbonaceous material composed of at least one of coke breeze and anthracite and a high combustible carbonaceous material having a lower combustion start temperature than the low combustible carbonaceous material are used. Use,
The carbon content of the highly combustible carbonaceous material has a mass ratio of 25% by mass to 75% by mass with respect to the carbon content of the coagulating material.
A method for producing a sinter, in which at least one of the low-combustible carbonaceous material and the high-combustible carbonaceous material is added in the latter half of the granulation step of the sintered raw material. The sintering according to claim 1, wherein as the sintering raw material, an iron-based raw material having a low degree of oxidation, which is an iron-based raw material containing metallic iron or divalent iron ions, is blended in an amount of 2% by mass or more based on the total new raw materials. How to make ore.

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