JP2022139102A - Method for producing molded product and method for producing molded coke - Google Patents

Abstract

To provide a method for producing a molded product and a method for producing molded coke as a technique for suppressing fusion between molded products during dry distillation relatively easily and quickly without limiting a condition for dry distillation and a raw material to be used.SOLUTION: A method for producing a molded product comprises the steps of: preparing single or multiple raw materials mainly composed of coal; heating the prepared raw materials; and molding the heated raw materials, wherein a temperature (Tb) of the raw materials is set at 75°C or higher to 250°C or lower in the step of molding when a fusion rate (α) of the molded product based on a definition below is 30 mass% or more. The fusion rate (α) is defined as a weight percentage of a dry distillation product in which two or more molded products are connected to total weight of a cooled dry distillation product after dry distillation in an inert gas atmosphere to a re-solidification temperature of the raw materials or higher in a state where a plurality of molded products obtained by molding the raw materials processed in the step of preparing the raw materials at a temperature of less than 75°C are adjacent to each other.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a method for producing molded products mainly composed of coal, which is a raw material for molded coke, and a method for producing molded coke by carbonizing the produced molded products.

Coke for ironmaking is produced by carbonizing coal to a temperature of 1000° C. or higher in a coke oven (steaming in the absence of air), and is used in a blast furnace, which is the main ironmaking equipment. The coke charged into the blast furnace contains a reducing agent that reduces iron ore, which is the main raw material in the ironmaking process, a heat source that supplies the heat necessary for the ironmaking reaction, and a solid/liquid/gas countercurrent reactor. It plays a role such as a spacer to ensure ventilation and liquid flow in the blast furnace. In general, it is considered necessary to increase the strength of coke to be used in order to achieve low reducing agent ratio operation, which is effective for energy saving and CO ₂ emission reduction of blast furnaces.

In the coke-making process using a chamber-type coke oven, which is the most widely used coke-making process, a large amount of highly caking coal must be used in order to produce high-strength coke. However, since strong coking coal is rare and expensive, there is a strong demand to produce high-strength coke while using less expensive inferior coal such as non-slightly coking coal.

As a promising process for producing high-strength coke using a large amount of inferior coal, the conventional molded coke production process has been researched and developed. Molded coke is a carbonized product obtained by preparing coal, which is the main raw material, in various steps, mechanically compacting and molding to produce high-density moldings, and then carbonizing the moldings. Molded coke is generally manufactured so that the shape of the molding is maintained.

Numerous processes related to molded coke have been studied so far. For example, as for the molding step, a cold molding method in which a binder is added to the coal and molded in a cold state, the coal is heated to around 400 ° C. where the coal exhibits caking property, and the coal itself has a caking property, so it can be used without a binder. There is a hot molding method for molding a molded product. As for the carbonization step, in addition to a method of carbonization in a chamber coke oven, a carbonization method using a moving bed carbonization furnace or a continuous vertical shaft furnace has been proposed. Among them, the process of charging the molded product obtained by cold forming from the upper part of the vertical shaft furnace, carbonizing it, and continuously discharging the molded coke from the lower part of the shaft furnace Steel companies have jointly researched and developed this process, and it has been developed to the point of practical application (commonly known as the Iron and Steel Federation type coke forming process). This method is promising because it is possible to increase the amount of inferior coal with poor cohesion, and it has features such as high productivity, high production elasticity, and low environmental load.

However, in the method of producing molded coke in a vertical shaft furnace, it is necessary to prevent moldings from fusing together during carbonization. This is because when moldings are fused together in a shaft furnace, a huge lump is formed, and if the lump is larger than the discharge port at the bottom of the furnace, the lump cannot be discharged, resulting in inoperability. In order to avoid this situation, a method has been reported in which the temperature is rapidly raised at the initial stage of carbonization to form a hardened layer of coke on the surface of the molding to prevent fusion. In addition, it has been reported that, as properties of raw materials, caking properties such as stickiness and expansibility affect the fusion bondability of molded products. Methods for controlling raw material properties include a method of blending coal with poor caking properties such as anthracite and semi-anthracite (Patent Document 1), a method of using coal with high ash content (Patent Document 2), and a method of softening and melting properties. A method of controlling the blending ratio of high, easily fused coal (hereinafter referred to as easily softening coal) has been proposed (Patent Document 3).

Japanese Patent No. 5017969 Japanese Patent No. 6016001 WO2016/125727

As described above, in order to suppress the fusion of the moldings during carbonization, it is effective to change the carbonization conditions or change the composition of the raw material coal to control the properties. However, the prior art has the following problems.

The method of changing the dry distillation conditions cannot be easily implemented because it affects the production schedule of the operation and the heat quantity of the dry distillation. Further, it is difficult to precisely control the caking property of raw coal for forming coke. One of the reasons for this is that the coal that is mainly used for forming coke has poor coking properties. is not subject to quality control (because it is not a property that should be given particular importance as a fuel). Therefore, even if it is the same brand of coal, if there is a large lot difference in coking properties and coal with higher coking properties than expected is received, the coal owned in the inventory of the molded coke plant , a situation may occur in which the caking property of raw coal cannot be adjusted. As a countermeasure, if new coal is procured for adjusting the caking property of the raw material coal, it will take extra time and not only hinder the operation schedule, but also cause an additional cost increase. Conversely, in order to increase the ability to adjust the cohesiveness of raw coal in order to respond to lot fluctuations, it is necessary to keep multiple types of coal in stock, which creates problems in terms of securing locations and managing inventory. become. Another reason is that the evaluation of low caking properties has low accuracy in the first place. There are various evaluation tests for caking (for example, JIS M 8801 crucible expansion test, fluidity test, etc.), but low caking areas have low detection sensitivity. Therefore, it may be difficult to control the properties of raw material coal with high accuracy.

An object of the present invention is to propose a method for manufacturing molded products as a technique for suppressing fusion between molded products during dry distillation in a relatively simple and rapid manner without limiting the dry distillation conditions and raw materials used. .

Therefore, the inventors have extensively studied the relationship between the conditions for producing molded coke, particularly the conditions for producing moldings, and the rate of coalescence during carbonization of molded coke. As a result, it was found that if the raw material temperature during molding is increased, the expansion of the molded product is suppressed, and the fusion rate of the molded coke during carbonization decreases. As a result of further investigation based on this discovery, it was confirmed that the raw material temperature during molding to prevent fusion in the shaft furnace differs depending on the ease of fusion bonding of the molded product. Based on these findings, the present invention has been completed.

That is, the present invention provides a method for producing a molded product, which includes the steps of preparing single or multiple coal-based raw materials, heating the prepared raw materials, and molding the heated raw materials. and
When the fusion rate (α) of the molded product based on the following <definition of fusion rate (α)> is 30 mass% or more, the temperature (Tb) of the raw material is set to 75°C or more and 250°C or less in the molding step. A method for producing a molding, characterized in that:
<Definition of fusion rate (α)>
A plurality of moldings obtained by molding the raw material processed in the raw material preparation step at a temperature of less than 75 ° C. are placed next to each other, and heated (dry distillation) in an inert gas atmosphere to the resolidification temperature of the raw material or higher. After completing the softening and fusion by cooling, a carbonized product is produced, and the percentage of the weight ratio of the carbonized product in which two or more moldings are connected to the total weight of the carbonized product is defined as the fusion rate. (α).

In addition, in the method for manufacturing a molded article according to the present invention configured as described above,
(1) The temperature (Tb (°C)) of the raw material in the molding step is determined according to the fusion rate (α (mass%)) so as to satisfy the following formulas (1) and (2). characterized by:
1.25×α+32.5≦Tb≦250 (1)
75≦Tb (2),
(2) The above <definition of fusion rate (α)> shall be as follows:
<Definition of fusion rate (α)>
A plurality of moldings obtained by molding the raw material processed in the step of preparing the raw material at 70 ° C. are placed next to each other, and heated (dry distillation) in an inert gas atmosphere to the resolidification temperature of the raw material or higher to soften and melt. After the bonding is completed, the carbonized product is produced by cooling, and the percentage of the weight ratio of the carbonized product in which two or more moldings are connected to the total weight of the carbonized product is defined as the fusion ratio (α). to be
(3) dry distillation of the molded product manufactured according to the method for manufacturing the molded product;
is considered to be a more preferable solution.

According to the present invention, in the step of molding, the temperature (Tb) of the raw material determined to be easily fused is controlled to 75° C. or more and 250° C. or less during molding. It is possible to relatively easily and quickly suppress fusion between moldings in a dry distillation furnace without being restricted by dry distillation conditions or raw materials used. Therefore, it is possible to stably produce molded coke.

It is a graph which shows the relationship of the shrinkage|contraction rate of the height direction of the molding with respect to the temperature during carbonization of the molding which molded coal in cold or hot. 4 is a graph showing the relationship between the temperature of raw materials during molding and the fusion rate of molded coke. Fig. 10 is a graph showing the relationship between the fusion rate of a molded product at a temperature of 70°C during molding of raw coal and the lower limit of the temperature during molding required to make the fusion rate less than 30 mass%.

The manufacturing method of the molding of the present invention generally includes the steps of preparing single or multiple coal-based raw materials, heating, and molding. In the present invention, the step of preparing the raw material refers to the step of producing the raw material in a state suitable for producing moldings, mainly using single or multiple coals. For example, it includes blending a plurality of coals, adding additives to coal, and adjusting the particle size and moisture content of the raw material of molded products containing coal. In this method, confirming that the raw material temperature during molding for preventing fusion when the molded product obtained in the molding step is carbonized differs depending on the ease of fusion of the molded product, Based on this finding, the present invention has been completed.

First, the results of a preliminary experiment confirming the principle of this finding are shown. Coal A with VM = 31.2 (% d.b.), log MF = 1.0, CSN = 1.0 was used for the experiment. After the coal A was air-dried, it was pulverized so that the content of particles of 0.1 mm or less was 100 wt %. 2 g of this pulverized sample is filled in a mold of φ16 mm, molded at room temperature at a pressure of 100 MPa (cold molding), or heated to 200 ° C. in an argon gas atmosphere and molded at the same pressure (hot molding), and cold molded. A product and a hot-formed product were obtained. When these moldings were heated to 900° C. in an electric furnace under nitrogen gas flow, the shrinkage ratio of the height to the initial height of the moldings was investigated. The results are shown in FIG.

From the results of FIG. 1, it can be seen that the cold-molded product expands from around 400° C., where coal exhibits softening and melting properties. On the other hand, the hot moldings showed no expansion during carbonization and contracted uniformly after 400°C. The higher the expansibility of the raw coal, the more likely it is that the moldings will fuse together during carbonization. The reason for the decrease in expandability due to hot compacting is presumed to be that a slight structural change in the coal molecules occurred during hot compacting, which had some effect on the thermal decomposition reaction during carbonization. The upper limit of the hot forming temperature of the present invention is about 250° C. at the highest, which is clearly higher than the conventional hot forming temperature that achieves bonding between coals by utilizing the caking property of coal. low. Conventionally, at a temperature of about 250° C., thermal decomposition reaction of coal does not occur, and it has been thought that the change in properties is limited. The novel part of the present invention is that it was found that even in this relatively mild heating temperature range (75 to 250° C.), the expansibility of coal and, in turn, the fusion properties of molded products change.

Next, the fusion rate (α) was investigated by changing the temperature during compounding and molding (details will be shown in the examples below). Here, the fusion rate (α) means that the raw material processed in the raw material preparation step is molded at a temperature of less than 75° C. to produce a molded product, and a plurality of molded products are adjacent to each other. After heating (dry distillation) in an inert gas atmosphere to the resolidification temperature or higher of the raw material to complete softening and fusion, the raw material is cooled to produce a dry distillation product, and 2 or more per total weight of the dry distillation product. It can be obtained as a percentage of the weight ratio of the dry distillation product to which the molding of is connected. Also, from the fusion rate obtained in the experiment at a certain molding temperature, the fusion rate in the case of molding at another temperature may be estimated. This fusion rate (α) is a value that indicates the easiness of fusion bonding of the carbonized product, and it can be judged that the higher the fusion rate (α), the easier the fusion of the molding. In addition, as a suitable example of "finishing the softening and fusion bonding by heating (dry distillation) in an inert gas atmosphere to the softening and melting temperature in a state in which a plurality of molded articles are adjacent to each other", a plurality of molded articles are adjacent to each other. It may be heated to at least 600° C. at a heating rate of 3-5° C./min. By heating to at least 600° C. at a rate of temperature increase of 3 to 5° C./min, the softening and melting of the molding is completed. Caking coal, which is suitably used as a raw material for coke production, softens and melts when heated, and solidifies again when the heating temperature is further raised. The temperature at which the softened and melted coal solidifies again is called the resolidification temperature, and the softening and melting is completed by the resolidification. That is, by heating the molded article to a resolidification temperature or higher, a melted material in which the molded articles adhere to each other is generated.

This knowledge was organized and formulated. The temperature (Tb (°C)) of the raw material at the time of molding to make the fusion rate less than 30 mass% according to the fusion rate (α (mass%)) of the molded product molded from the raw material at less than 75 ° C. It was found that the preferable range is determined so as to satisfy the following formulas (1) and (2):
1.25×α+32.5≦Tb≦250 (1),
75≦Tb (2).

Therefore, it is desirable to investigate the fusion rate (α) of the molded product molded at less than 75° C. of the raw material, and change the raw material temperature during the molding step to the above preferred range according to the result. If the temperature in the molding machine exceeds 250° C., the risk of facility troubles and disasters such as fires and explosions increases due to the gasification of flammable volatile matter. Therefore, it is desirable that the temperature during molding is 250° C. or lower.

Regarding the temperature control during molding in the step of molding the heated raw material, it varies depending on the method of the molding apparatus, but in a method such as a compression press that can directly heat the raw material, the raw material is heated at the time of molding, and the temperature of the raw material is kept above the lower limit. is desirable. On the other hand, in the case of an apparatus such as roll molding in which direct heating is difficult, it is effective to raise the temperature in a process (such as a compounding process) before the molding step. Especially in the molding step, it is desirable to control the heating temperature because the softening of the binder due to heating also affects the quality of the molding. However, in this case, it is necessary to determine the heating temperature so that the temperature of the raw material during molding is 75° C. to 250° C., taking into account the drop in raw material temperature due to heat removal up to the molding step. The temperature of the raw material during molding can be confirmed by measuring the temperature of the molding immediately after molding. Similarly, the molding temperature for determining the fusion rate (α) should be set so that the temperature of the raw material during molding is less than 75°C. In addition, since the molding temperature for determining the fusion rate is lower than the temperature of the molding step in the manufacturing method of the molded product of the present invention, the temperature drop from heating the raw material to molding is small, and the raw material before molding is low. If the temperature is less than 75°C, the temperature during molding is substantially the same as the temperature of the raw material, so molding is performed by controlling the temperature of the raw material before molding (the temperature of the raw material introduced into the molding machine). may

A low oxygen concentration is desirable as the atmosphere during heating and molding. When coal is heated in the presence of oxygen, the so-called weathering phenomenon may deteriorate the quality of the coal. An atmosphere with a low oxygen concentration is also desirable from the viewpoint of reducing the risk of fire, explosion, and the like. The oxygen concentration in the atmosphere during heating or molding is preferably 18% by volume or less, but if the quality deterioration of coal is practically minor or if sufficient measures are taken against the risk of fire and explosion, Heating and molding may be performed. In order to reduce the oxygen concentration, a method of creating an atmosphere containing an inert gas such as nitrogen or a method of increasing the partial pressure of water vapor in the atmosphere to reduce the oxygen concentration can be employed.

In order to investigate the relationship between the raw material temperature during molding and the cohesion rate of molded coke after carbonization, the blending ratio of various easily softening coals (coal with a button index CSN of JIS M 8801 exceeding 2.0) was changed. , the fusion rate was measured when the moldings molded by changing the temperature at the time of raw material kneading were carbonized. The molding method and dry distillation method of the molded product were as follows.

First, a binder was added to coal blends of multiple coal brands, and kneading and molding were carried out. Regarding the softening and melting characteristics of blended coal, the weighted average value (LogMF) of the logarithm of Gieseler's maximum fluidity is in the range of 0.4 to 1.1, and the ash content of blended coal is in the range of 10.0 to 10.5 mass%. did. The grain size of the coal was 2 mm or less in total. As binders, soft pitch and coal tar were added in an amount of 8.0 to 10.0 mass% of the weight before the raw materials. The mixture was kneaded at 100° C. to 200° C. using a high-speed stirring mixer as a kneader, and the kneaded material was molded using a double roll type molding machine. The roll size was 650 mmφ×104 mm, and molding was performed at a rotation speed of 2 rpm and a linear pressure of 1 to 4 t/cm. The size of the molding is 30 mm x 25 mm x 18 mm (6 cc) and the shape is oval.

The temperature of the molding immediately after molding was measured, and this temperature was taken as the molding temperature. The temperature during molding was about 70° C. to 150° C., which was consistent with the temperature of the raw material immediately before entering the molding rolls. That is, the temperature at the time of molding can be used as the temperature (Tb) of the material to be molded. Moreover, a high degree of correlation was observed between the temperature during molding and the temperature during kneading. That is, the temperature during molding can be adjusted by adjusting the temperature during kneading. The dry distillation of the molding was carried out by the following laboratory-scale dry distillation method (fixed bed). A dry distillation can of 200 mm long, 60 mm wide and 200 mm high was filled with 1.8 kg of the molding, and after dry distillation by program heating using an electric furnace, it was cooled in a nitrogen atmosphere. Program heating raises the temperature of the space between the moldings in the center of the molding layer from room temperature to 500°C at 15°C/min, and from 500 to 750°C at a rate of 3°C/min. was maintained for 143 minutes at . After cooling, the molded coke was taken out from the container, the weight ratio of the sample in which two or more molded cokes were fused together was calculated, defined as the fusion rate, and the relationship between the fusion rate and the temperature during molding was investigated. The temperature of the gap between the moldings in the center of the molding layer (or the internal temperature of the coal briquette near the center of the molding layer) at a rate of 2 to 20°C/min of 350 to 500°C. More desirably, if the temperature is 2 to 15° C./min and the maximum temperature is 700 to 1000° C., the fusion rate is almost the same. Evaluable. Of these, when the rate of temperature increase from 350 to 500° C. exceeds 20° C./min, the fusion rate increases significantly, making it difficult to detect the difference in the fusion rate due to the difference in properties of the molded product. Therefore, it is desirable to set the temperature increase rate within the preferred range.

FIG. 2 shows the relationship between the fusion rate and the temperature during molding. From the results of FIG. 2, it was found that the fusion rate at the same molding temperature increases as the easily softening coal blending ratio increases. In addition, it was confirmed that although the fusion rate decreases as the temperature rises during molding, the slope is constant regardless of the composition. In other words, it was found that the temperature of the raw material during molding at which the fusion rate reaches a specific value increases as the blending ratio of easily softening coal increases.

When coke briquettes are obtained by carbonizing coal briquettes in a shaft furnace, if the fusion rate exceeds a certain value, unloading of the coke briquettes will be delayed, making it difficult to discharge the coke from the furnace and hindering the operation of the furnace. known to increase probability. The inventor investigated the relationship between the fusion rate and operation troubles and found that smooth operation becomes difficult when the fusion rate is 30 mass % or more. FIG. 2 shows a line with a fusion rate of 30 mass % as an example of the upper limit for operation. Generally, if the fusion rate is below this line, operation can be carried out without major problems. However, depending on the type of furnace and operating conditions, there are cases where the fusion rate does not reach 30 mass%, which makes smooth operation difficult. Even in that case, it is clear that the raw material that exhibits a fusion rate of 30 mass% or more when molded at a temperature of less than 75° C. is a raw material that is easily fused. C., the fusion rate during operation can be lower than when molding at temperatures below 75.degree. That is, in the present invention, a raw material that is easily fused is specified based on the fusion rate α of the raw material molded product obtained under predetermined conditions, and when a raw material that is easily fused is used, the molding temperature is set to 75 to 75°C. By increasing the temperature to 250°C, the problem of suppressing fusion during carbonization is solved. By this method, it is possible to obtain the effect that if the fusion rate decreases, operational troubles can be reduced accordingly. The target value of how much the fusion rate during operation should be lowered can be appropriately set by those skilled in the art based on their operational experience. It is one embodiment of the present invention to adjust the molding temperature based on ease of use.

Under the conditions of FIG. 2, when the temperature during molding is further lowered from 70° C., the fusion rate tends to increase as the temperature decreases. In the present invention, the fusion rate α is obtained for a molded product molded at a temperature of less than 75°C, and when the fusion rate α is 30 mass% or more, the molding temperature in the molding step in the manufacture of the molded product is set to 75°C. C. or higher to suppress fusion. If the molding temperature when obtaining α is low, the value of α will be large. is evaluated as high (easily fused). Therefore, if the molding temperature when obtaining α is low, the temperature in the molding step is increased for a wider range of raw materials, and the fusion can be suppressed more reliably.

However, for a wider range of raw materials, if the molding temperature is raised in the molding step in the manufacture of the molded product, fusion can be reliably suppressed, but on the other hand, the amount of raw materials to be molded at high temperatures increases. As a result, there is also a disadvantage in terms of energy consumption. Therefore, in some cases, it is preferable to set the molding temperature for determining the fusion rate as high as possible. Considering this advantage and loss, it is preferable to set the molding temperature at 65° C. or more and less than 75° C., more preferably 70° C., when obtaining the fusion rate α. At this time, in the operation for obtaining the fusion rate α, it is not always necessary to perform molding at 70°C. can be estimated. As a method for estimating such a fusion rate, the fusion rate in the case of molding at 70° C. may be estimated by interpolation or extrapolation from a plurality of experimental results. can be estimated from In this way, the molding temperature in the molding step in the manufacture of the molded product can be determined based on the fusion rate α when molding is performed at 70°C.

Therefore, based on the relationship between the raw material temperature and the fusion rate for each raw material shown in FIG. FIG. 3 shows the results of determining the temperature of the raw material. Here, the fusion rate at a molding temperature of 70° C. represents the easiness of fusion of blended charcoal. The regression line in FIG. 3 indicates the lower limit temperature for reducing the fusion ratio to 30% or less when the raw material having the fusion ratio in the case of molding at 70° C. is carbonized. Therefore, if molding is performed at a temperature higher than this regression line, the fusion rate can be reduced to less than 30%. From this result, in order to prevent fusion between molded products during carbonization, it is necessary to raise the temperature of the raw material at the time of molding by a certain number or more according to the fusion rate of the raw coal at 70 ° C. You can see if you can control the wear. Based on this result, the preferred range of the present invention was defined.

The method for producing a molded article according to the present invention is not limited to the molded article that is the raw material for molded coke, and can be applied to other molded articles that pose a problem of fusion of the molded article due to heating.

Claims (4)

1. A method for producing a molded product, comprising the steps of preparing a single or multiple coal-based raw material, heating the prepared raw material, and molding the heated raw material, the method comprising:
When the fusion rate (α) of the molded product based on the following <definition of fusion rate (α)> is 30 mass% or more, the temperature (Tb) of the raw material is set to 75°C or more and 250°C or less in the molding step. A method for producing a molding, characterized in that:
<Definition of fusion rate (α)>
A plurality of moldings obtained by molding the raw material processed in the raw material preparation step at a temperature of less than 75 ° C. are placed next to each other, and heated (dry distillation) in an inert gas atmosphere to the resolidification temperature of the raw material or higher. After completing the softening and fusion by cooling, a carbonized product is produced, and the percentage of the weight ratio of the carbonized product in which two or more moldings are connected to the total weight of the carbonized product is defined as the fusion rate. (α). The temperature (Tb (°C)) of the raw material in the molding step is determined according to the fusion rate (α (mass%)) so as to satisfy the following formulas (1) and (2). The method for producing a molded article according to claim 1, wherein:
1.25×α+32.5≦Tb≦250 (1)
75≦Tb (2). The method for producing a molded product according to claim 1 or claim 2, wherein the <definition of fusion rate (α)> is as follows:
<Definition of fusion rate (α)>
A plurality of moldings obtained by molding the raw material processed in the step of preparing the raw material at 70 ° C. are placed next to each other, and heated (dry distillation) in an inert gas atmosphere to the resolidification temperature of the raw material or higher to soften and melt. After the bonding is completed, the carbonized product is produced by cooling, and the percentage of the weight ratio of the carbonized product in which two or more moldings are connected to the total weight of the carbonized product is defined as the fusion ratio (α). and A method for producing molded coke, wherein the molded product produced according to the method for producing a molded product according to any one of claims 1 to 3 is carbonized.

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