JP7327293B2 - Method for producing molding for ferro-coke and method for producing ferro-coke - Google Patents

Description

The present invention relates to a method for producing molded products for ferro-coke by molding a mixture of coal, iron raw material and binder, and a method for producing ferro-coke by carbonizing the molded products.

In order to efficiently operate a blast furnace, coke produced by carbonizing coal in a coke oven is charged into the blast furnace. Coke charged into the blast furnace has the role of a spacer for improving ventilation in the blast furnace, a role of a reducing agent, and a role of a heat source. In recent years, techniques using ferro-coke have been developed from the viewpoint of improving coke reactivity.

Ferro-coke is made by pulverizing coal and iron raw materials, which are the main raw materials, in advance, drying them, stirring and kneading them in a kneader with a binder of several mass%, and then molding them with a double roll molding machine. It is produced by dry distillation in a vertical furnace. The properties of the binder used during molding are very important because it greatly affects not only the strength of the molded product but also the strength of the ferro-coke after carbonization.

In particular, the property required for the low softening point binder, which serves as a glue that binds particles together during molding, is to have an appropriate viscosity at the temperature during kneading. If the viscosity is too low, the particles cannot be adhered to each other and the strength of the molding cannot be increased. On the other hand, if the viscosity is too high, the binder cannot be dispersed throughout the raw material during kneading, resulting in uneven strength between portions with and without the binder. For this reason, coal tar pitch (soft pitch), which has an appropriate viscosity at the kneading temperature, is used in the production of ferro-coke.

Steelworks with blast furnaces that use ferro-coke are equipped with chamber-furnace coke ovens that produce coke, which is used as a reducing agent in the blast furnace. are manufacturing. Coal tar is produced as a by-product during the carbonization of coal, and is transported to a chemical plant where it is distilled and the residue is used to produce soft pitch. For this reason, steel mills have the advantage of being able to procure soft pitch as a binder, but since soft pitch is a solid or highly viscous liquid at room temperature, it is transported from the soft pitch manufacturing process to the ferro-coke molding manufacturing process. There is a problem that it takes time and effort to handle when using it as one. Here, if the coal tar produced in the chamber-type coke oven can be used directly as a binder, the steps of conveying coal tar to a chemical plant, distilling coal tar to produce soft pitch, and producing soft pitch can be eliminated.

On the other hand, if coal tar is used directly as a binder for ferro-coke moldings, when the ferro-coke moldings are charged into a ferro-coke carbonization furnace and carbonized to produce ferro-coke, the strength of the moldings is sufficiently increased. There was a problem that it could not be made high and powdered to reduce the yield of ferro-coke production. In order to address this decrease in the strength of the molded product, Patent Document 1 discloses a technique of measuring the mass ratio of the γ resin component contained in the low softening point binder and using a low softening point binder containing a γ resin component in a predetermined mass ratio or more. is disclosed.

JP 2016-222790 A

"Science and Technology of Coal", edited by the Japan Institute of Energy, published by Corona Publishing, 2013, 240 pages

According to the technique disclosed in Patent Document 1, it is possible to effectively increase the strength of the molded product by using a low softening point binder containing a γ resin component in a predetermined mass ratio or more. There is a problem that a low softening point binder whose amount is lower than a predetermined mass ratio cannot increase the strength of the molded product and cannot be used as a binder for the molded product for ferro-coke. The present invention has been made in view of such prior art, and its object is to increase the viscosity of a low softening point binder such as coal tar during kneading, and to obtain a high-strength ferromagnetic material by using the binder. An object of the present invention is to provide a method for producing a molding for ferro-coke, which can produce a molding for coke.

Means for solving the above problems are as follows.
(1) A method for producing a molded product for ferro-coke in which a binder is added to coal and an iron raw material to form a mixture, and the mixture is kneaded and molded, wherein the binder is obtained by carbonizing coal at 950 ° C. or less. A method for producing a molded product for ferro-coke, which is coal tar and is kneaded at 120° C. or higher for a predetermined time.
(2) The method for producing a molding for ferro-coke according to (1), wherein the coal tar is ferro-coke tar contained in the gas discharged during the carbonization of the molding for ferro-coke.
(3) The method for producing a molding for ferro-coke according to (1) or (2), wherein the predetermined time is longer than the time to complete volatilization of naphthalene contained in the coal tar at the kneading temperature.
(4) The method for producing a molding for ferro-coke according to any one of (1) to (3), wherein the kneading is performed at 180°C or lower.
(5) A method for producing ferro-coke, comprising carbonizing the molded product for ferro-coke produced by the method for producing a molded product for ferro-coke according to any one of (1) to (4) to produce ferro-coke. .

By carrying out the method for producing a molding for ferro-coke according to the present invention, the viscosity of a low softening point binder such as coal tar can be increased during kneading regardless of the content of the γ resin component. High-strength moldings for ferro-coke can be produced. As a result, the coal tar and ferro-coke tar contained in the gas discharged from the coke oven can be used as a binder without being distilled, so the production cost of ferro-coke moldings and ferro-coke can be reduced. .

1 is a diagram showing an example of a ferro-coke manufacturing process to which the method for manufacturing a ferro-coke molding according to the present embodiment can be applied; FIG. 4 is a graph showing the change over time in the amount of naphthalene generated from ferro-coke tar measured using an EGA-MS method (evolved gas mass spectrometry). 1 is a graph showing the relationship between strength and kneading time of molded products for ferro-coke kneaded at 120° C., 140° C., and 160° C. FIG.

Hereinafter, the present invention will be described through embodiments of the present invention. FIG. 1 is a diagram showing an example of a ferro-coke manufacturing process to which the method for manufacturing a ferro-coke molding according to the present embodiment can be applied. The manufacturing process of ferro-coke consists of a kneader 16 , a molding machine 20 and a carbonization furnace 24 .

A binder 14 is added to coal 10 and iron raw material 12 which are raw materials of ferro-coke, and kneaded using a kneader 16 to form a mixture 18 . This mixture 18 is molded in a molding machine 20 to produce moldings 22 for ferro-coke. This molded product 22 for ferro-coke is charged into a carbonization furnace 24 and carbonized to produce ferro-coke.

As the coal 10, for example, it is preferable to use non-slightly caking coal having a maximum Gieseler fluidity of 0 or more and 100 ddpm or less determined by the method specified in JIS M 8801. Iron ore may be used as the iron raw material 12, but iron-containing dust such as blast furnace dust, converter dust, rolling sludge, etc., which is by-produced in steelworks may also be used. The coal 10 and the iron raw material 12 are preferably pulverized and dried to a predetermined particle size or less using a pulverizer (not shown) before kneading. It is preferable to pulverize to a diameter of 3 mm or less. In the present embodiment, the particle size is a particle size that can be sieved using a sieve with openings that comply with JIS Z 8801-1. For example, a particle size of 3 mm or less is based on JIS Z 8801-1. It means the particle size that can be sieved under a sieve with an opening of 3 mm. As the binder 14, ferro-coke tar contained in gas discharged during ferro-coke carbonization is used.

By using the ferro coke tar as the binder 14, the ferro coke tar generated in the ferro coke production process can be directly recycled as a binder in the ferro coke production process. As a result, the production cost of ferro-coke moldings and ferro-coke can be reduced.

Coal used as a raw material for ferro-coke and coal used as a raw material for normal coke used as a reducing agent in a blast furnace are not necessarily of the same type. However, if the carbonization temperature is the same, the softening point of ferro-coke tar obtained by carbonization in the ferro-coke production process and the softening point of coal tar obtained in carbonization in the normal coke production process are equivalent. The strength of the molded product obtained when used as is also considered to be equivalent. Therefore, instead of ferro-coke tar, coal tar obtained by carbonization at a temperature equivalent to the carbonization temperature in the ferro-coke production process may be used as the binder 14 .

Carbonization in the ferro-coke production process is generally carried out at 950°C or lower, whereas carbonization in the normal coke production process is generally carried out at 1000°C or higher. Ferro coke tar obtained by carbonization at 950°C or lower has a lower carbonization temperature than coal tar obtained by carbonization at 1000°C or higher. According to Non-Patent Document 1, in contrast to low-temperature tar produced at 400 to 500° C., at temperatures exceeding 1000° C., components in the low-temperature tar undergo secondary decomposition, and are therefore called high-temperature tar. The composition of cold tar differs from that of hot tar. Ferro-coke tar is classified as low-temperature tar, and contains more components that volatilize at low temperatures compared to coal tar (high-temperature tar) obtained by dry distillation at temperatures of 1000°C or higher. Low softening point.

The kneader 16 is a kneading device that has a stirrer and can control the kneading temperature to a constant temperature. Coal 10 , iron raw material 12 and binder 14 are put into kneader 16 and kneaded at 120° C. or higher for a predetermined time to form mixture 18 .

Table 1 shows the main hydrocarbon components contained in the gas generated from ferro coke tar when heated to 160° C. measured using TCT-GCMS. As shown in Table 1, the gas generated from ferro-coke tar by heating includes naphthalene and the like removed by distillation during the process of producing soft pitch from coal tar. If such components can be removed during kneading, the viscosity of the ferro coke tar will increase, and the performance as a binder, that is, the performance for bonding particles together will greatly improve.

FIG. 2 is a graph showing changes over time in the amount of naphthalene generated from ferro-coke tar measured using the EGA-MS method (evolved gas mass spectrometry). In FIG. 2, the vertical axis represents the naphthalene signal intensity, and the signal intensity indicates the amount of naphthalene contained in the gas. The horizontal axis is the heating time (minutes) of the ferro coke tar. Since the ferro-coke tar was heated from room temperature, the volatilization amount of naphthalene increased from the start of heating and then decreased. As shown in FIG. 2(a), when the heating temperature was 120° C., the heating time until the generation amount became 0 was 4 minutes and 30 seconds. Further, as shown in FIGS. 2(b) and 2(c), when the heating temperature is 140° C., the heating time until the amount of generated naphthalene becomes 0 is about 5 minutes, and the heating temperature is 160° C. In this case, the heating time until the amount of generated naphthalene became 0 was about 6 minutes.

Further, as shown in FIG. 2, the higher the heating temperature of the ferro-coke tar, the longer the time from the start of heating until the volatilization amount of naphthalene becomes zero. This is probably because the heating time was lower than the boiling point of naphthalene (218° C.), so the amount of naphthalene volatilized from the ferro-coke tar increased as the heating temperature increased.

Thus, by kneading at 120° C. or higher for a predetermined time using the kneader 16, naphthalene, which is a low-molecular-weight hydrocarbon, can be volatilized from the ferro-coke tar. By removing low mass hydrocarbons such as naphthalene, the viscosity of the ferro coke tar is increased, thereby improving its performance as a binder.

The predetermined time for kneading in the kneader 16 is preferably longer than the time required for volatilization of naphthalene contained in the ferro-coke tar to be completed at each kneading temperature. That is, when the kneading temperature is 120°C, the kneading time is preferably 4 minutes and 30 seconds or longer, and when the kneading temperature is 160°C, the kneading time is preferably 6 minutes or longer. Thereby, the performance as a binder can be greatly improved at each kneading temperature.

Moreover, the predetermined time for kneading in the kneader 16 is preferably one minute or less after volatilization of naphthalene is completed. As shown in FIG. 2, naphthalene does not volatilize any more even if it is further heated after volatilization of naphthalene is completed. Therefore, from the viewpoint of reforming the ferro-coke tar, it is preferable that the predetermined time for kneading in the kneader 16 is longer than the time when volatilization of naphthalene is completed and one minute or less after volatilization of naphthalene is completed. .

Before using the ferro-coke tar as the binder 14, the point in time when the volatilization of naphthalene is completed is determined in advance. The volatilization tendency of naphthalene does not change with the sample amount of ferro coke tar. Therefore, the point at which volatilization of naphthalene is completed can be determined by heating a small amount of ferro-coke tar at a predetermined temperature and continuously measuring the volatile content on a laboratory scale. In addition, it is preferable to identify the ferro coke tar for each brand of coal 10 used for the carbonization in which the ferro coke tar was generated, and to grasp the point in time when volatilization of naphthalene is completed for each identified ferro coke tar. This makes it possible to more accurately grasp the time point at which volatilization of naphthalene is completed.

Furthermore, the kneading temperature is preferably 120° C. or higher and 180° C. or lower. If the kneading temperature is less than 120° C., the volatilization amount of naphthalene from the ferro coke tar is reduced, and the performance of the ferro coke tar as a binder is not significantly improved. On the other hand, if the kneading temperature is higher than 180° C., the viscosity of the ferro coke tar becomes too high, making it difficult to disperse the ferro coke tar in the kneading process, which is not preferable. The kneading temperature is more preferably 140° C. or higher and 160° C. or lower.

As described above, in the method for producing a molding for ferro-coke according to the present embodiment, ferro-coke tar is used as the binder 14 and kneaded at 120 ° C. or higher for a predetermined time to increase the viscosity of the ferro-coke tar and use it as a binder. improve performance. As a result, regardless of the content of the γ-resin component, it is possible to manufacture a ferro-coke molding having high strength while using the ferro-coke tar as the binder 14 .

In the method for producing a molded product for ferro-coke according to the present embodiment, the coal tar and ferro-coke tar contained in the gas discharged from the coke oven can be used as they are as a binder without being distilled. A large reduction in the manufacturing cost of products and a large reduction in the manufacturing cost of ferro-coke can be realized. In addition, ferro coke tar has a lower viscosity than conventionally used soft pitch. For this reason, soft pitch cannot be transported by piping unless it is heated to about 100°C, whereas ferro coke tar can be transported by piping only by heating it to about 50°C, which simplifies the heating mechanism during transportation. can.

It is preferable to knead until volatilization of naphthalene is completed at each kneading temperature, but it is not necessary to knead until volatilization of naphthalene is completed. As shown in FIG. 2, a large amount of naphthalene volatilizes at the initial stage of heating, and the volatilization amount of naphthalene is small for 1 to 2 minutes before the volatilization is completed. Therefore, for example, the kneading time may be ended within 2 minutes before volatilization of naphthalene is completed.

Also, in the present embodiment, an example using ferro coke tar as a binder was shown, but the binder is not limited to this. As the binder, coal tar contained in gas discharged when coke is carbonized at a carbonization temperature of 950° C. or less may be used. By carbonizing the coal at a carbonization temperature of 950° C. or less, the strength of the molded product can be increased, and a decrease in yield due to pulverization can be suppressed. Coal tar contained in the gas discharged when coke is carbonized at a carbonization temperature of 900° C. or lower, more preferably 850° C. or lower is used. Even when such coal tar is used, volatilization of naphthalene from the coal tar improves the viscosity and improves performance as a binder. However, ferro-coke tar is included in the gas generated at a maximum temperature of about 850 ° C during the carbonization of ferro-coke, and is available in the manufacturing process of ferro-coke, so ferro-coke tar can be used as a binder for ferro-coke manufacturing. more preferred.

Next, the effects of kneading temperature and kneading time on the strength of the ferro-coke molding will be described. In order to confirm the influence of the kneading temperature and kneading time on the strength of the molded product, a mixture was prepared by changing the kneading temperature and kneading time, and the strength of the molded product for ferro-coke produced by molding the mixture was measured. The ferro-coke molded product was obtained by mixing blended coal of two brands of coal and iron ore, adding ferro-coke tar as a binder, kneading and molding. The coal was ground to a particle size of 2 mm or less, and the iron ore was ground to a particle size of 3 mm or less. The content of coal blend is 70% by mass, and the content of iron ore is 30% by mass. The amount of the binder added is 5% by mass with respect to the total amount of coal and iron ore. The mixture was kneaded at 120° C., 140° C. and 160° C. using a high-speed stirring mixer as a kneader, and the mixture was molded using a double roll molding machine to obtain a molding. The roll size of the double roll molding machine was Φ650 mm×104 mm, and molding was performed at a rotation speed of 2 rpm and a linear pressure of 1.5 t/cm. The size of the molding is 30 mm×25 mm×18 mm (6 cc), and the shape is oval.

The strength of the molded product for ferro-coke was evaluated by ID strength (30/16). The ID strength is measured by placing 20 molded products in an I-type drum tester (cylinder with an inner diameter of 160 mm and a length of 700 mm), and rotating the molded product 30 times at a rotation speed of 20 rotations per minute around the center of the cylinder. It is the strength evaluated by the residual rate on a sieve with a mesh size of 16 mm.

For kneading, the temperature of the raw materials was continuously measured, and after 2 minutes from the start of kneading, ferro-coke tar was added, and then kneading was carried out for 3 to 8 minutes. FIG. 3 is a graph showing the relationship between the strength of ferro-coke moldings kneaded at 120° C., 140° C. and 160° C. and the kneading time. In FIG. 3, the vertical axis is the ID strength of the molding, and the horizontal axis is the kneading time (minutes) after adding the ferro coke tar.

As shown in FIG. 3, at any of 120° C., 140° C., and 160° C., the strength of the ferro-coke moldings increased significantly with the kneading time until volatilization of naphthalene was completed. On the other hand, after volatilization of naphthalene was completed, the strength of the molding for ferro-coke slightly increased, but no significant improvement was observed.

As for the kneading temperature, the higher the kneading temperature, the higher the strength of the molding. This is probably because more naphthalene can be volatilized from the ferro-coke tar at a higher temperature, so that the ferro-coke tar becomes heavier, thereby increasing the strength of the ferro-coke molding. In addition, the reason why the strength of the ferro-coke moldings improved even after volatilization of naphthalene was completed is thought to be that anthracene and pyrene, which have higher boiling points than naphthalene, volatilized, making the ferro-coke tar even heavier. be done. From these results, it was confirmed that kneading at 120° C. or higher mainly volatilizes the naphthalene contained in the ferro-coke tar and improves the performance as a binder, thereby improving the strength of the molded product for ferro-coke. . If the strength of the molded product for ferro-coke is improved, the strength of the ferro-coke produced by carbonizing the molded product is also improved. It is possible to produce ferro-coke with high strength by using a molded product for ferro-coke.

REFERENCE SIGNS LIST 10 Coal 12 Iron raw material 14 Binder 16 Kneader 18 Mixture 20 Forming machine 22 Molded product for ferro-coke 24 Carbonization furnace

Claims (3)

A method for producing a molded product for ferro-coke in which a binder is added to coal and an iron raw material to form a mixture, and the mixture is kneaded and molded,
The binder is coal tar obtained by carbonizing coal at 950° C. or less,
A method for producing a molding for ferro-coke, wherein the kneading is performed at 120° C. or higher and 180° C. or lower for a time longer than the time to complete volatilization of naphthalene contained in the coal tar. 2. The method for producing a molded product for ferro-coke according to claim 1, wherein said coal tar is ferro-coke tar contained in gas discharged during carbonization of said molded product for ferro-coke. 3. A method for producing ferro-coke, wherein the molded product for ferro-coke produced by the method for producing a molded product for ferro-coke according to claim 1 is carbonized to produce ferro-coke.

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