JP6179732B2 - Method of molding coal or a mixture of coal and metal oxide - Google Patents

Description

  The present invention relates to a method for molding coal or a mixture of coal and a metal oxide to obtain a coke raw material, a carburized material, ferro-coke and the like.

  Molding of coal or a mixture of coal and metal oxide is performed in a wide range of fields. For example, Patent Literature 1 and Patent Literature 2 describe that coal and crude tar are mixed and molded into a coke oven as coke raw materials. Patent Document 3 describes that, as a reducing agent in a blast furnace and a carburizing material for hot metal in a cupola, calcium is mixed with coal and molded and then charged into a coke oven. All of the techniques proposed in these patent documents are methods in which a raw material is molded using a binder such as tar during molding.

  In recent blast furnaces, the use of ferro-coke containing metallic iron in coke has been studied for the purpose of reducing carbon dioxide emissions (Non-patent Document 1). This ferro-coke is formed by adding a binder to a mixture of coal and iron ore, and the addition of the binder is indispensable.

Japanese Patent Laid-Open No. 62-34983 JP-A-60-110785 Japanese Patent Publication No. 8-16225

Materials and Processes, 21, 893 (2008) Granulation handbook; 202 (1991) Japan Powder Industrial Technology Association 1979 Research report on continuous molding coke manufacturing technology; 106-197 (1980) Japan Iron and Steel Federation (Continuous Forming Coke Research and Development Committee) Ohm Materials and Processes, 22, 742 (2009) Coal chemistry and industry; Sankyo Publishing Co., Ltd. 62 (1977) Proceedings of the Coal Science Conference (40), 64-65, 2003-10-23 Clay Science 6 (1), 14-21, 1966-12-05

  When manufacturing (molding) the ferro-coke, it is known that the strength of the molded product varies depending on the coal brand. For example, according to Non-Patent Document 2, the relationship between the hardness of the coal and the strength of the molded product indicates that the strength of the molded product decreases as the hardness of the coal increases. In addition, according to Non-Patent Document 3, it is disclosed that when the amount of binder added is constant, when moldings are produced by changing their blending ratio using a plurality of coal brands, the strength of each molding is different. Has been. These results indicate that it is necessary to change conditions such as the amount of binder added depending on the brand of coal.

  Non-Patent Document 4 shows the result of molding with a fixed coal brand using a raw material mixed with iron ore with different pore amounts and changing the amount of binder added. According to this, it is shown that when iron ore having a large amount of pores is used, it is necessary to increase the amount of binder added. In coal, as shown in Non-Patent Document 5, when the carbon content is 90 mass% or less, if the internal surface area is large, the added binder is easily absorbed. This suggests that there is a need to increase. In fact, even in the relationship between the hardness of the coal and the strength of the molded product in Non-Patent Document 2, it is clear that the strength of the molded product decreases as the hard glove index decreases.

  Generally, coal with a low carbon content has a low hard glove index, and coal with a low hard glove index (hereinafter also referred to as “HGI”) increases the strength of the molded product by increasing the amount of binder added. It is considered possible.

  However, the inventors have studied that coal groups having the HGI of 50 and the carbon content of 83 mass% (daf: dry ash free) and having substantially the same carbon content as the HGI are similarly fined. When a molding test was carried out with a constant amount of binder, it was found that the brand of coal was divided into a brand with a high molding strength and a brand with a low molding strength.

  An object of the present invention is to propose a molding method of coal or a mixture of coal and metal oxide, which can obtain a high molding strength by optimizing the amount of binder added.

  The inventors have come into contact with the problem that the strength of the molded product varies depending on the coal brand despite the fact that the hard glove index (HGI) and the coal content are almost the same. Went. As a result, the following knowledge was obtained. That is, it can be inferred that such a variation in strength has a difference in the adsorption area of the coal involved in the absorption of the binder in each coal brand. That is, in evaluating the adsorption area of coal, the adsorption area of coal obtained from the result of measuring the amount of methylene blue adsorption can give a more suitable evaluation than the internal surface area by the conventional BET measurement method and the like. I realized that.

  The object of the present invention was developed in view of such knowledge, and when molding a coal (including a mixture of two or more brands of coal. The same applies hereinafter) or a mixture of coal and a metal oxide, It is to propose a suitable molding method of coal or a mixture of coal and metal oxide by measuring the adsorption area of coal in advance and reflecting this in the amount of binder added.

  The present invention for solving the above-mentioned problems is that the coal or a mixture of coal and a metal oxide is kneaded with a binder and molded according to the adsorption area of each coal measured by a methylene blue adsorption test. The present invention provides a method for molding coal or a mixture of coal and metal oxide, wherein the molding is performed by determining the amount of addition.

In the method of molding coal or a mixture of coal and metal oxide according to the present invention configured as described above,
(1) According to the coal particle size distribution, kneading time and kneading temperature, the correlation formula between the minimum value of the binder addition rate that maximizes the strength of the molded product and the methylene blue adsorption area of the coal is investigated and used for molding. Determining the binder addition rate according to the methylene blue adsorption area of the coal to be
(2) Obtain the adsorption area S (10 ⁻³ m ² / cm ² ) measured by the methylene blue adsorption test of the coal to be used, and mold it at the binder addition rate a (mass%) obtained by the following equation (1). :
a = 0.104S + 4.5 (1),
Is considered to be a more preferable solution.

  According to the present invention, when producing a molded product of coal or a mixture of coal and metal oxide, methylene blue adsorption measurement is performed for each brand of coal before molding, and the adsorption area of each coal is obtained in advance. Therefore, it is possible to set an appropriate amount of the binder to be added, so that the binder can be added without excess or deficiency. As a result, according to the present invention, a high-strength coal molding or coal / metal oxide molding can be suitably produced.

It is a graph which shows the relationship between a BET internal surface area and the carbon content rate of coal. It is a graph which shows the relationship between the amount of pores by a mercury intrusion method, and the carbon content rate of coal. It is a graph which shows the relationship between a methylene blue (MB) adsorption area and carbon content. It is a graph which shows the relationship between a molded article strength and a BET internal surface area. It is a graph which shows the relationship between a molded object strength and the amount of pores by the mercury intrusion method. It is a graph which shows the relationship between a molded article strength and a methylene blue (MB) adsorption area. It is a graph which shows the relationship between molding strength and a binder addition rate. It is a graph which shows the relationship between an optimal binder addition rate and a methylene blue (MB) adsorption area. It is a graph which shows the relationship between the binder addition rate of the intensity | strength peak in a coal grinding | pulverization particle size of 0.4 mm and 1.5 mm, and a methylene blue (MB) adsorption area. It is a graph which shows the relationship between the binder addition rate of the intensity | strength peak in kneading | mixing temperature of 100 degreeC, and a methylene blue (MB) adsorption area. It is a graph which shows the relationship between the binder addition rate of the intensity | strength peak in kneading time 240 seconds, and a methylene blue (MB) adsorption area. It is a graph which shows the transition result of molding strength.

  In the method for producing coal or coal and metal oxide and molding, the present invention performs methylene blue adsorption measurement of each brand of coal before molding to determine the adsorption area of each coal, thereby It is to know the optimum addition amount.

  Hereinafter, the methylene blue (MB) adsorption test method will be described first. Prior to the explanation, the conventional method (BET method, mercury intrusion method) and the method of the present invention were compared with the relationship between the carbon content and the strength of the molded product. The relationship will be described. Next, based on these relationships, a method for molding coal or a mixture of coal and metal oxide of the present invention will be described.

<About the methylene blue adsorption method>
As shown in Non-Patent Documents 6 and 7, methylene blue adsorption is a technique used for measuring the specific surface area and cation exchange capacity of clay minerals. As a result of intensive studies on this measurement method, the inventors have found that the adsorption area determined by the methylene blue adsorption method correlates with the optimum value of the binder addition amount of the coal molding or the like, which results in the molding strength. We found that it becomes one of the governing factors. In this measurement method, methylene blue itself is considered to be adsorbed to the coal surface in a single layer. Therefore, the area of methylene blue adsorbed is calculated by multiplying the amount of methylene blue adsorbed by the area of one molecule of methylene blue (1.3 nm ² ). It is considered possible. The method for measuring the amount of methylene blue adsorbed on coal will be described below.

(1) Prepare 600 mL of methylene blue aqueous solution prepared so as to have a methylene blue concentration of 5 × 10 ⁻⁶ mol / L.
(2) The coal is pulverized to a target pulverization particle size at the time of molding (total amount is 2 mm or less). Sufficiently drying the coal in N _2.
(3) Weigh 1 g of coal, transfer it to a polypropylene container, add a small amount of ethanol water, and then quickly add 600 mL of methylene blue aqueous solution.
(4) Hold for 1 minute with stirring, and immediately filter through a membrane filter. All filtration bottles and sample bottles shall be made of polypropylene.
(5) Collect the filtrate and measure the absorbance (at 665 nm) of the filtrate with a visible spectrophotometer. Evaluate the methylene blue concentration of the filtrate from the absorbance and concentration calibration curve obtained in advance.
(6) The amount of methylene blue adsorbed is evaluated from the difference in aqueous methylene blue concentration before methylene blue adsorption and the aqueous solution concentration after the test. The methylene blue adsorption area per unit weight of coal is calculated from the size of one molecule of methylene blue.

<Relationship between conventional method (BET method, mercury intrusion method) and the present invention method and carbon content>
As a conventional method, the internal surface area of coal by BET measurement and the amount of internal pores of coal by mercury intrusion method were determined for coal having the properties shown in Table 1 below. The results are shown in FIGS. The coal used here is coal having a carbon content of 82 to 90 mass% (daf). As shown in FIG. 1, the relationship between the BET internal surface area and the carbon content is almost monotonously decreasing as the carbon content is increased. As shown in FIG. 2, the relationship between the amount of internal pores and the carbon content by the mercury intrusion method varies widely, but generally the amount of internal pores decreases as the carbon content increases. Here, the amount of internal pores shows a value of 5 microns or less, but the tendency was the same even with thresholds other than 5 microns.

  Meanwhile, FIG. 3 shows the relationship between the unit coal weight calculated from the methylene blue adsorption amount and the methylene blue adsorption area per unit coal particle outer surface area and the carbon content. As shown in FIG. 3, the methylene blue adsorption area generally decreases as the carbon content increases, but there is a case where the methylene blue adsorption area is low only for one brand (D charcoal) at a carbon content of 83 mass%.

<Relationship between the conventional method (BET method, mercury intrusion method) and the present invention method and the strength of the molded product>
Next, a molding test was performed on coals B to G having a carbon content of about 83 mass% by the conventional method and the present invention method. Kneading with a binder and molding were performed as follows. Coal was pulverized so that the total amount was 3 mm or less, that is, the average particle size was 0.6 to 0.9 mm. The iron ore was blended so that the Fe content in the fine powder was 65 mass% and 30 mass% with respect to the total raw material weight. The binder was added to 5 mass% with respect to the total raw material weight, and kneaded at 140 to 160 ° C. for 90 to 120 seconds with a high speed mixer. The kneaded raw material was used to produce briquettes with a double roll type molding machine. The roll size was 650 mm × 104 mm in diameter, and was molded at a peripheral speed of 0.2 m / s and a molding linear pressure of 3.3 to 3.8 t / cm. The size of the molded product is 30 mm × 25 mm × 18 mm (6 cc) and the shape is egg-shaped. The strength of the molded product was evaluated by using a type I drum test apparatus (cylindrical shape having an inner diameter of 130 mm × 700 mm) based on a residual rate of 16 mm or more after 30 rotations at a rotation speed of 20 rotations per minute (ID Strength 30/16).

  Regarding coals B to G, the relationship between the coal particle surface area determined by the BET method affecting the strength of the molded product and the amount of pores determined by the mercury intrusion method is shown in FIGS. The relationship with the adsorption area is shown in FIG. 4 and 5, it can be seen that the coal particle internal area by the BET method and the pore amount by the mercury intrusion method have a small correlation with the strength of the molded product. On the other hand, the molding strength shown in FIG. 6 has a high correlation with the methylene blue adsorption area. Presumably, the methylene blue adsorption studied in the present invention occurs only on the outer surface of the coal and in the vicinity of the outer surface, and is correlated with the adsorption site of the coal-based soft pitch (SOP) as a binder. The strength of the molded product was very high with only coal D having a carbon content of 83 mass%. As shown in FIG. 6, since the methylene blue adsorption area of D charcoal is small, the amount of binder absorbed into D charcoal during the kneading process performed during the molding test is small, and the function of the binder is sufficiently exhibited, so that the molded product It is inferred that the strength was high.

<Relationship between binder addition rate and MB adsorption area according to the present invention>
FIG. 7 shows the results of molding coals B to G with the molding conditions fixed and only the binder addition rate changed. With each brand, the strength of the molded product increases as the binder addition rate increases. It can be seen that the binder addition rate at which the strength of the molded product becomes the maximum value differs depending on the brand.

FIG. 8 shows the relationship between the methylene blue adsorption area and the optimum binder addition rate (evaluated with the minimum amount of binder addition rate at which the strength of the molded product is almost the maximum value from FIG. 7). A high correlation is recognized between the methylene blue adsorption area and the optimum binder addition rate, and it can be seen that the brand having a small methylene blue adsorption area has a high molding strength with a small amount of binder. These results determine the adsorption area was measured by methylene blue adsorption test of coal using ^{S (10 -3 m 2 / cm} 2), the following equation (1) a = 0.104S + 4.5 (1)
It can be seen that it is preferable to mold at the binder addition rate a (mass%) determined by the above.

  Compared with the evaluation test of FIG. 8, the influence on the optimum binder addition rate is shown in the case where the coal pulverization particle size is changed to 0.4 mm and 1.5 mm, the kneading temperature is 100 ° C., and the kneading time is 240 seconds. 11 shows. It can be seen that when the raw material conditions and the kneading conditions are changed significantly, the degree of influence of the methylene blue adsorption area is different from that in FIG. From this, if the raw material conditions and kneading molding conditions are kept constant, the optimum binder addition rate can be predicted by measuring the methylene blue adsorption area of each brand.

<Example 1>
This example is an example in which a molded product of a mixture of coal and iron ore was produced in an actual operation for producing ferro-coke. Coal used is C, D, G charcoal. As for the raw material conditions, each brand was pulverized so as to have an average particle size of about 0.8 mm and molded for each brand. The iron ore was blended so that the Fe content in the fine powder was 65 mass% and 30 mass% with respect to the total raw material weight. As the binder, coal-based soft pitch (SOP) was used, and the optimum binder amount was added based on FIG. Coal, iron ore, and binder were kneaded for 120 seconds at 155 ° C. with a high-speed mixer. The kneaded raw material was used to produce briquettes with a double roll type molding machine. The roll size was 1050 mm × 1000 mm in diameter, and was molded at a peripheral speed of 0.2 m / s and a molding linear pressure of 3.3 to 3.8 t / cm.

  The brand was changed in the order of coals D, G, and C, and each brand was molded for 2 hours. And, the binder to be added was changed to the brand, and the addition amount of the previous brand was changed for 30 minutes, and then changed to the optimum binder amount based on FIG. The transition result of the strength of the molded product is shown in FIG. The strength of the molded product was measured every 30 minutes. In coal D, molding was performed at a constant binder addition rate of 5 mass%, and after 3 hours, switching to coal G was performed, and the binder addition rate was changed to 6 mass% after 3.5 hours. Thereafter, the brand was changed to coal C after 6 hours, and the binder addition rate was changed to 6.6 mass% after 6.5 hours. After changing the brand, the strength of the molded product was low during the time zone when the binder addition rate was not optimal.

<Example 2>
In the same manner as in Example 1, the transition of the molding strength was examined for each of the mixture of coal D and G, the mixture of coal G and C, and the mixture of coal C and D, which were mixed at 1: 1. It was. At this time, the optimum binder amount was the average of the binder amounts of the two coals obtained based on FIG. As a result, the strength of the molded product approximated to FIG. 12 can be obtained, and it was confirmed that even a mixture of coal has the effect of the present invention.

  The method for molding coal or a mixture of coal and metal oxide according to the present invention can obtain a high molding strength by optimizing the amount of binder added, and includes coal, a mixture of two or more types of coal, and coal. In addition to being suitably used for molding a mixture with a metal oxide, the present invention can also be applied to molding of other granular materials that require the addition of a binder.

Claims (2)

When kneading and molding coal or a mixture of coal and metal oxide with a binder , depending on the coal particle size distribution, kneading time and kneading temperature, the binder addition rate that maximizes the strength of the molded product Based on the correlation between the minimum value and the adsorption area of each coal measured by the methylene blue adsorption test of coal, the molding is performed by determining the binder addition rate according to the methylene blue adsorption area of the coal used for molding A method for molding coal or a mixture of coal and metal oxide. The adsorption area S (10 ⁻³ m ² / cm ² ) measured by the methylene blue adsorption test of the coal to be used is obtained and molded at the binder addition rate a (mass%) obtained by the following equation (1). The shaping | molding method of the mixture of coal or coal and a metal oxide of Claim 1 to do .
a = 0.104S + 4.5 (1)

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