Method for manufacturing molded coke

Abstract

We propose a method for producing coke that is highly reactive and has high post-reaction strength. [Solution] A method for producing molded coke by molding a blended coal mixture of coal and carbon material, and then carbonizing the resulting agglomerated product, characterized in that the blended coal is prepared by blending coal having a particle size of 1 mm or less in proportion of 70% by mass or more, with biomass or carbon material obtained by heat-treating biomass having a particle size of 1 mm or less in proportion of 70% by mass or more, in a proportion of 1% by mass or more and 40% by mass or less relative to the total amount of coal and carbon material.

Description

[Technical Field]

[0001] This invention relates to a method for producing molded coke. [Background technology]

[0002] In blast furnaces, iron ore is alternately layered with coke, which is produced by the carbonization of coal. Coke plays a role in maintaining gas aeration from below within the blast furnace, as well as acting as a reducing agent for the iron ore and as a heat source within the furnace. In particular, to maintain aeration within the furnace, the coke needs to be of high strength, as the generation of coke powder due to reactions and friction within the blast furnace would reduce aeration.

[0003] In recent years, technologies for using highly reactive coke have been investigated to reduce CO2 emissions in the ironmaking process, and one such technology is ferrocoke containing iron. As described in Non-Patent Literature 1, ferrocoke is produced by mixing iron into molded coke, and due to the catalytic effect of iron, it exhibits high gasification reactivity with CO2 at high temperatures in the blast furnace (CO2 + coke → 2CO, hereinafter referred to as "reactivity"). By charging ferrocoke, the ferrocoke starts the gasification reaction in the blast furnace from a low temperature range, which is expected to reduce the reducing agent ratio by lowering the temperature of the heat retention zone in the blast furnace.

[0004] On the other hand, as the reactivity of coke increases, its post-reaction strength decreases, generating coke powder in the blast furnace. This makes it difficult to maintain aeration in the blast furnace, leading to an increase in the blast furnace reducing agent ratio and a decrease in productivity. Therefore, CRI (Coke Reaction Index) and CSR (Coke Strength after Reaction) are commonly used as indicators to manage the reactivity and post-reaction strength of coke. The measurement methods for CRI and CSR are specified in ISO 18894. Specifically, 200g of coke adjusted to a particle size of 20±1mm is reacted with 100% CO2 gas flowing at 5L / min at 1100°C for 2 hours, and the mass loss rate before and after the reaction is defined as CRI. Furthermore, the post-reaction coke is rotated 600 times in a Type I drum testing machine, and the mass yield on a 9.5mm sieve is defined as CSR.

[0005] Although highly reactive coke is thought to gasify and disappear even if coke powder is generated, it is important to manage and understand its reactivity and post-reaction strength for stable blast furnace operation.

[0006] Furthermore, in order to reduce CO2 emissions, the use of carbon-neutral carbon sources in the conventional applications of fossil fuels such as coal and oil is being considered, and it is hoped that carbon-neutral plant-based biomass raw materials will be used to replace raw materials for coke production.

[0007] Generally, lump coke used in blast furnaces is produced by carbonizing raw coal in a coke oven, which softens and melts the coal, causing it to bond together. Therefore, to produce high-strength coke, it is common to select and use coal that has good softening and melting properties.

[0008] However, plant-based biomass raw materials do not soften and melt like coal, and because they contain a high amount of oxygen, a challenge arises when used in combination with coal, as they can inhibit the softening and melting properties of the coal.

[0009] To address this issue, reducing the oxygen content in plant-based biomass raw materials is effective. A method has been devised to suppress the decrease in softening and melting properties by pre-heat-treating plant-based biomass to reduce its oxygen content and then mixing it with coal as a carbon material.

[0010] For example, Patent Document 1 proposes a method for evaluating blending quality when heat-treated biomass is blended into blended coal. It states that because the effect of oxygen in the heat-treated biomass is small, the degree of coalification (Ro) and the maximum fluidity (Gieseler) of the softened and melted biomass can be controlled.

[0011] Furthermore, biomass heat-treated at temperatures below 1000°C is more reactive than coke obtained by the carbonization of raw coal, and its blending increases the reactivity of the coke. In coke produced by blending such highly reactive heat-treated biomass with raw coal, the portion derived from the heat-treated biomass is more reactive than the portion derived from the raw coal.

[0012] Non-patent document 2 reports that the gasification reaction of coke does not proceed uniformly throughout, but rather preferentially degrades the reaction in highly reactive structures with low carbon crystallinity. Non-patent document 2 also states that the carbon matrix portion in coke can be classified into several optical structures based on the anisotropy observed under a polarizing microscope, depending on the difference in carbon crystallinity, but that isotropic and inert structures with low carbon crystallinity have a higher gasification rate and the reaction proceeds preferentially. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Publication No. 2014-77086 [Non-patent literature]

[0014] [Non-Patent Document 1] Yamamoto et al., Iron and Steel, Vol. 9 (2011), No.10, 501

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0015] Generally, there is a negative correlation between the reactivity (CRI) and the strength after reaction (CSR). It is known that when the CRI increases, the CSR decreases. Therefore, although high-reactivity coke is effective in reducing the reduction material ratio in the blast furnace, its strength after reaction is low. As a result, there is a problem that coke powder is generated in the blast furnace and there is a concern of deteriorating the ventilation in the furnace. The coexistence of high reactivity and high strength after reaction has been demanded.

[0016] The present invention has been made in view of the above problems, and an object thereof is to propose a method for manufacturing formed coke capable of manufacturing formed coke having high reactivity and high strength after reaction.

Means for Solving the Problems

[0017] The present invention for solving the above problems is as follows.

[0018] [1] A method for manufacturing formed coke by molding a blended coal obtained by mixing coal and a carbonaceous material, and carbonizing the obtained lump product to obtain formed coke, wherein biomass in which the proportion of particles having a particle size of 1 mm or less is 70% by mass or more, or a carbonaceous material obtained by heat-treating biomass, is blended in a proportion of 1% by mass or more and 40% by mass or less with respect to the total amount of the coal and the carbonaceous material to prepare the blended coal. A method for manufacturing formed coke, characterized in that.

[0019] [2] The method for manufacturing formed coke according to [1], wherein the volatile content of the carbonaceous material is 1% by mass or more and less than 40% by mass on an anhydrous basis.

[0020] [3] The method for producing molded coke according to [1] or [2], wherein the coal has a Gieseler maximum fluidity of 1 ddpm or more and 25,000 ddpm or less as a softening and melting characteristic obtained by adding a primary or secondary amine compound having an aromatic ring.

[0021] [4] The volume of the aggregate is 1 cm 3 More than 80cm 3 A method for producing molded coke according to any one of the above [1] to [3], wherein the blended coal is molded as follows. [Effects of the Invention]

[0022] According to the present invention, molded coke with high reactivity and high post-reaction strength can be produced. This makes it possible to use carbon-neutral biomass raw materials as blast furnace raw materials, thereby reducing CO2 emissions. [Brief explanation of the drawing]

[0023] [Figure 1] This figure shows the relationship between reaction time and post-reaction strength for the three levels of ferrocoke used in Example 1. [Figure 2] This figure shows the relationship between reaction temperature and post-reaction strength for the three levels of ferrocoke used in Example 2. [Modes for carrying out the invention]

[0024] (Method of manufacturing molded coke) Embodiments of the present invention will be described below. The method for producing molded coke according to the present invention is a method for producing molded coke by molding a blended coal mixture obtained by mixing coal and carbon material, and then carbonizing the resulting molded product.Hereinafter, the blended coal is prepared by blending coal having a particle size of 1 mm or less in proportion of 70% by mass or more, with biomass or carbon material obtained by heat-treating biomass having a particle size of 1 mm or less in proportion of 70% by mass or more, in a proportion of 1% by mass or more and 40% by mass or less relative to the total amount of coal and carbon material.

[0025] The inventors of the present invention have diligently studied ways to solve the above problems. One method for producing highly reactive coke other than ferrocoke is to blend in highly reactive raw materials other than iron. In particular, blending in highly reactive carbon materials (hereinafter also referred to as "carbon materials") increases the overall reactivity of the coke, and in the gasification reaction, the highly reactive parts react preferentially, thereby suppressing the reaction degradation of the carbon portion of the coke.

[0026] Among carbon materials, the lower the carbon crystallinity, the higher the gasification reactivity. Therefore, it is beneficial to blend carbon materials with low carbon crystallinity, and biomass is one such material. As mentioned above, biomass has high volatile content and high oxygen content, so when mixed with coal and carbonized, it inhibits the softening and melting properties of the coal. However, by reducing the volatile content of the biomass through heat treatment, the impact on softening and melting properties can be suppressed.

[0027] Because biomass itself is highly reactive, when the aforementioned heat-treated biomass is included in coke, the heat-treated biomass portion reacts preferentially. As a result, the reaction degradation of the coke substrate portion derived from the raw coal is suppressed, and the decrease in post-reaction strength can be suppressed.

[0028] The inventors of this invention have discovered that in molded coke, by blending coal with biomass or carbon material obtained by heat-treating biomass, which is more reactive than the carbon matrix portion of coke, and by preferentially gasifying the highly reactive carbon material portion, it is possible to suppress the reaction degradation of the carbon matrix portion of coke, thereby achieving both high reactivity and high post-reaction strength. Thus, the present invention was completed.

[0029] <Biomass> Biomass is a general term for a certain amount of accumulated animal and plant resources and waste derived from them (excluding fossil resources). The biomass used in this embodiment includes all types of biomass that produce carbonized material when thermally decomposed, such as agricultural, forestry, livestock, fisheries, and waste materials.

[0030] In this embodiment, it is preferable to use biomass with a high effective calorific value as the raw material for the molded coke produced, for example, woody biomass is preferred.

[0031] Woody biomass includes papermaking by-products such as pulp black liquor and chip dust, sawmilling by-products such as bark and sawdust, forest residues such as branches, leaves, canopies, and scraps, thinned timber from cedar, cypress, and pine, and special forest products such as spent logs for edible fungi, as well as forestry biomass such as fuelwood forests of oak, chestnut, and pine, and short-rotation forests of willow, poplar, eucalyptus, and pine. Woody biomass also includes general waste such as pruned branches from street trees in municipalities and garden trees in private homes, as well as industrial waste such as pruned branches from street trees in national and prefectural governments and garden trees in companies, and construction waste.

[0032] Agricultural biomass, including rice husks, wheat straw, rice straw, sugarcane residue, palm oil, etc., which are classified as agricultural biomass and originate from waste and by-products, as well as some agricultural biomass such as rice bran, rapeseed, and soybeans, which originate from energy crops, can also be suitably used as woody biomass.

[0033] Biomass generally contains a large amount of moisture and volatile matter, and has a low bulk density. Therefore, its low energy density and poor transport efficiency are major challenges for industrial use. For this reason, compaction, molding, and carbonization processes are widely used to increase the bulk density or energy density.

[0034] In recent years, the volume of carbonized or semi-carbonized biomass, and pellets molded from carbonized or semi-carbonized biomass (referred to as "black pellets"), has been increasing. In this invention, it is preferable to use carbonized or semi-carbonized biomass with a volatile content of 1 wt% DB or more and less than 40 wt% DB, i.e., 1% by mass or less than 40% by mass on an anhydrous basis, as a raw material for molded coke.

[0035] The volatile content of the biomass was measured according to the Japanese Industrial Standard (JIS) "Coal and Coke - Industrial Analysis Methods" (JIS M 8812:2004). The volatile content values ​​below are on an anhydrous basis.

[0036] Biomass containing 40% or more by mass of volatile matter can also be used as a raw material for molded coke in the present invention by first heat-treating it in an oxygen-free environment to adjust the volatile matter content to 1% or more by mass and less than 40% by mass, thereby becoming heat-treated biomass (an example of biomass).

[0037] The heat treatment of biomass is preferably carried out in an atmosphere where oxygen supply is cut off. The heat treatment of biomass is preferably carried out with the biomass contained in a container that forms a space where air inflow is inhibited and an inert gas flows through. The heat treatment of biomass can be carried out by heating the container containing the biomass and transferring heat from the container. In other words, the heat treatment of biomass can be carried out by heating the container while the biomass is contained within it.

[0038] The temperature at which biomass is heat-treated (hereinafter referred to as "heat treatment temperature") is preferably 300°C or higher. This effectively reduces the volatile content in the biomass to less than 40% by mass. On the other hand, if the heat treatment temperature exceeds 1100°C, the volatile content in the heat-treated biomass and the biomass may fall to less than 1% by mass, raising concerns that crack defects may be generated in the molded coke due to the difference in shrinkage rates with the surrounding coal when it is mixed with coal and carbonized in a subsequent stage. Therefore, it is preferable to set the heat treatment temperature of the biomass to 1100°C or lower.

[0039] Typically, the reaction rate of the thermal decomposition reaction of biomass during heat treatment is fast, so the time required for the thermal decomposition reaction to complete during heat treatment is short. Therefore, the time required for heat treatment is 1 minute or more. Preferably, the time for heat treatment (hereinafter referred to as "heat treatment time") is 10 minutes or more. This eliminates the temperature difference between the temperature of the biomass and the temperature of the container, allowing the entire biomass to be heat-treated uniformly. Furthermore, it becomes possible to reliably raise the temperature of the entire biomass to the heat treatment temperature uniformly (i.e., heat it evenly) and perform heat treatment, thereby suppressing variations in the quality of the heat-treated biomass.

[0040] On the other hand, while there is no particular upper limit to the heat treatment time, it is undesirable if the heat treatment time is too long because it increases the energy required for heat treatment and thus increases costs. Therefore, it is preferable to keep the heat treatment time to 60 minutes or less. Note that "heat treatment time" refers to the time from the moment the temperature of the biomass reaches a predetermined heat treatment temperature until it is maintained at that temperature.

[0041] The heat treatment of biomass can be carried out using heating equipment such as electric furnaces, rotary kilns, fluidized bed furnaces, screw furnaces, shaft furnaces, and carbonization furnaces.

[0042] <Coal> The properties of the raw material, coal, are important because the strength of the molded coke is maintained by the fluidity of the coal during the subsequent carbonization step. Therefore, coal with good fluidity is desirable. However, if the fluidity of the coal is too high, the agglomerates may fuse together during the subsequent carbonization step, especially when using a shaft furnace, making it difficult to remove the molded coke after carbonization. For this reason, it is preferable that the coal has a Gieseler maximum fluidity of 1 ddpm to 25,000 ddpm, obtained by adding a primary or secondary amine compound having an aromatic ring, such as DNPD (2,2-dinitropropane-1,3-diol).

[0043] The method for producing molded coke according to the present invention is not limited to any other steps, as long as a blended coal is prepared by blending coal having a particle size of 70% or more by mass with biomass or carbon material obtained by heat-treating biomass having a particle size of 70% or more by mass with a particle size of 1 mm or less by mass, in a ratio of 1% to 40% by mass relative to the total amount of coal and carbon material. For example, the method for producing molded coke according to the present invention includes a crushing step, a mixing step, a molding step, and a carbonization step. Each step will be described below, but the present invention is not limited thereto.

[0044] The crushing step is a process of crushing the raw materials, which are coal and biomass or carbon material obtained by heat-treating biomass (hereinafter sometimes simply referred to as "carbon material"). In the present invention, it is essential to prepare blended coal in the subsequent mixing step by blending coal with biomass or carbon material obtained by heat-treating biomass, in a proportion of 70% by mass or more of which has a particle size of 1 mm or less, at a ratio of 1% by mass to 40% by mass relative to the total amount of coal and carbon material. Therefore, in the crushing step, coal powder with a particle size of 1 mm or less and biomass or carbon material powder obtained by heat-treating biomass are obtained.

[0045] In this invention, unless otherwise specified, particle size refers to the maximum particle size. The particle size of the carbon material after heat treatment affects the porosity structure of the post-reaction coke because the carbon material reacts preferentially and deteriorates. In other words, if the particle size of the carbon material is small, the defect size after the reaction is also small, and therefore the effect on the post-reaction strength is small. However, if the particle size of the carbon material is large, the areas where the carbon material particles were present become coarse defects after the reaction, causing a decrease in post-reaction strength.

[0046] Furthermore, the particle size of the charcoal material also affects the strength of the agglomerated product during molding. If coarse charcoal particles are present, stress concentrates around them, becoming the starting point for fracture and thus reducing the strength of the agglomerated product. On the other hand, if the charcoal particles are fine, they fill the spaces between the charcoal particles during molding, increasing the density of the agglomerated product and improving its strength. For these reasons, the charcoal material is crushed so that the proportion of particles with a particle size of 1 mm or less is 70% by mass or more.

[0047] Furthermore, since the particle size of the coal affects the strength of the agglomerated product in the subsequent molding step, the proportion of particles smaller than 1 mm should be 70% by mass or more.

[0048] The method or apparatus for crushing coal and coal is not particularly limited. Cutter mills, hammer mills, pin mills, jet mills, ball mills, etc., may be used as the coal crushing apparatus.

[0049] In addition to crushing coal and carbon material separately, they may also be crushed after being mixed. However, as mentioned above, the particle size of the carbon material affects the subsequent product quality, so it is necessary to set the crushing conditions so that the particle size of the carbon material reaches a predetermined particle size.

[0050] The mixing step is the process of mixing the raw materials, coal and carbon material. In the present invention, it is essential to prepare the blended coal by blending coal having a particle size of 1 mm or less of 70% by mass or more of biomass or carbon material obtained by heat-treating biomass, with coal having a particle size of 1 mm or less of 70% by mass or more of biomass having a particle size of 1 mm or less, in a ratio of 1% by mass to 40% by mass relative to the total amount of coal and carbon material. As shown in the examples described later, this makes it possible to produce molded coke that achieves both high reactivity and high post-reaction strength.

[0051] The method of mixing coal and carbon material is not particularly limited. However, it is preferable to mix them thoroughly in order to prevent the carbon material from segregating in the agglomerated product during the subsequent molding step.

[0052] The molding step involves molding the blended coal, which is a mixture of coal and coal material, to obtain agglomerated material. The molding method of the blended coal is not particularly limited, but from the viewpoint of the strength and productivity of the resulting agglomerated material, a molding method using a double-roll type molding machine is preferred.

[0053] The appropriate size of agglomerates varies depending on the particle size of the coal, but if the agglomerates are too small, the strength may decrease. Therefore, the volume of the agglomerates should be 1 cm³. 3 It is preferable to keep the above. Also, if the aggregate is too large, sufficient molding pressure may not be applied during molding, which may reduce the density of the aggregate and thus the strength. For this reason, the volume of the aggregate should be 80 cm³. 3 The following is preferable: The volume of the aggregate is 3 cm³. 3 It is more preferable to make it 5 cm or more. 3 It is even more preferable to have the above. Also, the volume of the aggregate is 60 cm³. 3 The following is more preferable: 50cm 3 The following is even more preferable:

[0054] The carbonization step involves heat-treating the resulting agglomerate by heating it to over 900°C in an atmosphere that is devoid of air, in order to produce molded coke.

[0055] Heat treatment can be carried out using, for example, a shaft furnace, carbonization furnace, electric furnace, rotary kiln, fluidized bed furnace, screw furnace, etc.

[0056] Furthermore, regarding the evaluation method for the reactivity and post-reaction strength of molded coke, which is a highly reactive coke, highly reactive coke is particularly specialized in reaction within the role of coke, and its role in the blast furnace differs from that of ordinary coke that is not highly reactive. Therefore, it is considered that the measurement method for reactivity and post-reaction strength that can reproduce the gasification reaction of highly reactive coke in the blast furnace will differ from that for ordinary coke.

[0057] In conventional methods for general coke, first, the mass C of the coke sample before reaction is measured, then the mass A of the coke sample reacted with CO2 at 1100°C for 2 hours is measured, and finally, the mass B of the sample on a 9.5 mm sieve after rotating the reacted sample 600 times in a Type I testing machine is measured. The reaction rate is then evaluated based on the mass reduction rate of the sample after reaction with CO2 (i.e., ((mass C - mass A) / mass C) × 100 (%)), and the post-reaction strength of the coke is evaluated based on the ratio of mass B to mass A (i.e., (mass B / mass A) × 100 (%)) (see Shozo Murakami et al., Coke Circular, Vol. 23, 1974, pp. 82-87). However, with the above method, the reactivity and post-reaction strength of molded coke cannot be evaluated because molded coke, which is a highly reactive coke, is too reactive. Here, we decided to investigate an evaluation method using ferrocoke, another highly reactive coke, to see if it is possible to evaluate various highly reactive cokes.

[0058] Therefore, the inventors diligently investigated methods for evaluating the reactivity and post-reaction strength of highly reactive coke using ferrocoke. As a result, they found that the reactivity and post-reaction strength of highly reactive coke can be evaluated by the following method, and that the reaction state and amount of powder at the time of arrival at the bottom of the blast furnace can be reproduced with greater accuracy. • Reactivity of highly reactive coke: Mass loss rate after reaction at 1000°C in a CO2 atmosphere for 60 minutes. • Strength after high-reactivity coke reaction: The mass ratio on a 9.5 mm sieve after a sample reacted at 1000°C in a CO2 atmosphere for 60 minutes and rotated 600 times at a speed of 20 rpm in a Type I drum testing machine.

[0059] In other words, the inventors conducted reaction tests under various conditions to evaluate the reactivity and post-reaction strength of highly reactive coke. As a result, it became clear that even for samples where the measurement results were almost the same when measured using the conventional method with a reaction time of 120 minutes between coke and CO2, the difference could be detected by shortening the reaction time. Specifically, it was found that by setting the reaction time to 20 minutes or more and 110 minutes or less, it was possible to detect the difference between highly reactive cokes with different properties and evaluate the reactivity and post-reaction strength of highly reactive coke. It was also found that the difference in reactivity and post-reaction strength between highly reactive cokes with different properties was greatest when the reaction time was 60 minutes.

[0060] Furthermore, by setting the reaction temperature above the reaction start temperature of the highly reactive coke charged into the reaction vessel, preferably between 900°C and 1100°C, it is possible to prevent most of the sample from becoming pulverized, allowing for good detection of differences in reactivity and post-reaction strength between samples. It was also found that setting the reaction temperature to 1000°C maximizes the difference in post-reaction strength between highly reactive cokes with different properties.

[0061] Based on the above findings, the inventors have established a method for evaluating the post-reaction strength of highly reactive coke by measuring the mass C of a coke sample before reaction, measuring the mass A of a reactive coke sample reacted with CO2 at 1000°C for 60 minutes, measuring the mass B of the sample on a 9.5 mm sieve after rotating the reacted sample 600 times in a Type I testing machine, evaluating the reaction rate based on the mass reduction rate of the sample after reaction with CO2 (i.e., ((mass C - mass A) / mass C) × 100 (%)), and evaluating the post-reaction strength of highly reactive coke based on the ratio of mass B to mass A (i.e., (mass B / mass A) × 100 (%)). As described above, it has also been confirmed that the method for evaluating highly reactive coke discovered using ferrocoke can be applied to the molded coke of the present invention, which is similarly highly reactive.

[0062] In this way, molded coke that achieves both high reactivity and high post-reaction strength can be manufactured. [Examples]

[0063] The following describes examples of the present invention, but the present invention is not limited to these examples.

[0064] (Example 1) In Example 1, the effect of the reaction time between ferrocoke and CO2 on the post-reaction strength was evaluated. The properties of the three types of ferrocoke used in the test are shown in Table 1. In Table 1, FC represents the fixed carbon ratio of the ferrocoke, and T.Fe represents the iron content.

[0065] [Table 1]

[0066] Three types of ferrocoke A, B, and C with different properties (all with a reaction initiation temperature of less than 900°C) were prepared, and the difference in post-reaction strength among the samples over time was investigated. Specifically, 20 egg-shaped ferrocoke pieces measuring 30 mm × 25 mm × 18 mm (6 cc) were placed in a cylindrical reaction vessel, and the samples were reacted with CO2 at 1000°C for 30 minutes. The mass A of the sample after the reaction was measured. Subsequently, the ferrocoke sample after the reaction was rotated at 600 rpm at 20 rpm using a Type I testing machine, then placed on a sieve with a mesh size of 9.5 mm and sieved. The mass B of the sample remaining on the sieve was measured. The ratio of mass B to mass A was then calculated from the measured masses A and B, and the resulting ratio was defined as the post-reaction strength. The same measurement of post-reaction strength was performed for reaction times of 0 minutes, 60 minutes, 90 minutes, and 120 minutes. Figure 1 shows the relationship between reaction time and post-reaction strength for ferrocoke A to C.

[0067] The post-reaction strength of ferrocoke showed an increase in the difference in post-reaction strength between samples up to 60 minutes of reaction time, but conversely, the difference narrowed after 60 minutes. As a result, it was found that the post-reaction strength evaluation method used in the present invention can detect differences in post-reaction strength between samples when the reaction time is between 20 minutes and 110 minutes, the difference in post-reaction strength between samples increases when the reaction time is between 30 minutes and 90 minutes, and the difference is largest when the reaction time is 60 minutes.

[0068] (Example 2) In Example 2, the effect of the reaction temperature between ferrocoke and CO2 on the post-reaction strength was evaluated. The three types of ferrocoke used in the test were the same as those used in Example 1. Three types of ferrocoke with different properties, A, B, and C, were used to investigate the difference in post-reaction strength between samples as the reaction temperature progressed. Specifically, 20 ferrocoke units were placed in a cylindrical reaction vessel, and the samples were reacted with CO2 at a temperature of 900°C for 60 minutes. The mass A of the sample after the reaction was measured. Subsequently, the ferrocoke sample after the reaction was placed in the drum of a Type I testing machine, and after rotating the drum at 20 rpm for 600 times, it was placed on a sieve with a mesh size of 9.5 mm and sieved. The mass B of the sample remaining on the sieve was measured. Then, the ratio of mass B to mass A was calculated from the measured masses A and B, and the value of the obtained ratio was defined as the post-reaction strength. The post-reaction strength measurements described above were also performed for reaction temperatures of 800°C, 1000°C, and 1100°C. Figure 2 shows the relationship between reaction time and post-reaction strength for ferrocokes A to C.

[0069] The post-reaction strength of ferrocoke showed almost no difference between samples at a reaction temperature of 700°C, but the difference widened above 800°C, reaching its greatest extent at 1000°C. Above 1000°C, the difference in post-reaction strength narrowed with increasing reaction temperature, but the difference remained detectable up to 1100°C. However, when the reaction temperature was set to 1200°C, almost no difference between samples was detectable. As a result of these findings, it was found that the post-reaction strength measurement method used in this invention is effective at reaction temperatures between 800°C and 1100°C, with the greatest difference occurring at 1000°C.

[0070] (Example 3) In Example 3, as an evaluation of the ventilation effect in the blast furnace based on the post-reaction strength obtained by the evaluation method found with highly reactive ferrocoke, four types of formed cokes with different post-reaction strengths were used in the blast furnace, and the operation results under each condition were compared with the conditions of the reference example, and the reducibility and permeability were evaluated. As the ventilation resistance index, the K value (= (P B 2 - P T 2 ) / V 1.7 ) (P B : Blowing pressure (g / cm 2 ), P T : Top pressure (g / cm 2 ), V: Blowing volume (Nm 3 / min)) was used. The measurement conditions for the post-reaction strength were a reaction time of 60 minutes and a reaction temperature of 1000 °C. The results are shown in Table 2.

[0071]

Table 2

[0072] When formed cokes with post-reaction strengths of 58.6%, 49.5% and 38.6% were used, the gas utilization rate, which is an index of the reduction efficiency, improved and the reductant ratio decreased. The ventilation during this period was equivalent to that of the reference example or, even if it deteriorated, it was not a problem for blast furnace operation. On the other hand, when a formed coke with a low post-reaction strength of 28.7% was used, the ventilation resistance index increased significantly, and the tapping ratio decreased because the blast volume had to be reduced. From the above results, it was confirmed that the evaluation method of the post-reaction strength used in the present invention enables the evaluation of the ventilation effect when using formed coke in a blast furnace.

[0073] (Example 4) In Example 4, the relationship between the blending ratio of carbon material and the properties of molded coke was investigated. The sample preparation method was as follows. First, coal A with 20% by mass of volatile matter and carbon material B, which is biomass whose volatile matter was adjusted to 5.3% by mass by heat treatment, were prepared as raw materials. Coal A and carbon material B were crushed to a particle size of 1 mm or less using a crusher (crushing step), and then mixed according to the blending ratio shown in Table 3 (mixing step). The resulting blended coal was introduced into a stirrer, and asphalt pitch, soft pitch, and tar were added as binders at 3.5% by mass, 4.5% by mass, and 2.0% by mass, respectively, and kneaded while heating to 160°C. After that, it was molded in a molding machine with a roll size of 650 mmφ × 100 mm while applying pressure at a rotation speed of 2.0 rpm and 2 tons per 1 cm in the width direction (molding step), resulting in a size of 30 mm × 25 mm × 18 mm (6 cm 3 The material was formed into egg-shaped agglomerates. The resulting agglomerates were then carbonized using the following laboratory-scale method (fixed bed). Specifically, the agglomerates were packed into a carbonization vessel measuring 200 mm in length, 60 mm in width, and 200 mm in height, and carbonized for 4 hours and 20 minutes using programmed heating at a maximum of 850°C (carbonization step), after which they were cooled in a nitrogen atmosphere. Molded coke was thus produced.

[0074] The reactivity and post-reaction strength of the obtained molded coke were measured. The reactivity of the molded coke was evaluated by reacting 200g of molded coke with 100% CO2 gas flowing at 5L / min at 1000°C for 60 minutes, and measuring the mass loss rate before and after the reaction. The post-reaction strength of the molded coke was evaluated by rotating the molded coke after the above reaction at 600 rpm in a Type I drum testing machine, and measuring the mass yield of the mass on a 9.5mm sieve.

[0075] [Table 3]

[0076] Table 3 shows the reactivity and post-reaction strength of molded coke when the blending ratio of carbon material B is changed. At levels 1 to 6, reactivity increases as the blending ratio of carbon material B increases, and as previously observed, reactivity increases as the amount of highly reactive biomass increases. On the other hand, at levels 4 to 6, where the blending ratio of carbon material B exceeds 20%, the post-reaction strength decreases, showing a tendency for post-reaction strength to decrease with increasing reactivity, as previously observed. On the other hand, at levels 1 to 3, where the blending ratio of carbon material is 20% or less, the post-reaction strength increases even when the amount of carbon material increases. If the blending ratio of carbon material is 40% or less, it is possible to maintain equivalent post-reaction strength while having higher reactivity than molded coke at level 1, which does not contain carbon material.

[0077] Based on these results, it was confirmed that by blending biomass carbon material in a ratio of 1% to 40% by mass relative to the total amount of coal and carbon material, it is possible to increase the reactivity of molded coke while suppressing the decrease in post-reaction strength.

[0078] (Example 5) Table 4 shows the reactivity and post-reaction strength of molded coke when biomass carbon material C, which was adjusted to have a higher volatile content than carbon material B, was used. Carbon material C was prepared to have a volatile content of 20% by mass and a particle size of 1 mm or less, and then blended with coal A, which was also prepared to have a volatile content of 20% by mass and a particle size of 1 mm or less, at blending ratios of 0%, 2%, 5%, 30%, and 50% by mass relative to the total amount of coal A and carbon material C. Carbon material D with a volatile content of 40% by mass and carbon material E with a volatile content of 50% by mass were also evaluated similarly at a blending ratio of 30% by mass.

[0079] In Table 4, Level 7 is a comparative example that does not contain biomass carbon material, Levels 8-10 and Level 12 are inventive examples that contain biomass carbon material C or carbon material D, and Levels 11 and 13 are comparative examples in which the carbon material blending ratio and volatile content of the carbon material are outside the scope of the present invention.

[0080] [Table 4]

[0081] At levels 8-11, reactivity increased with increasing carbon material C content, and at carbon material C content up to 30% by mass, the post-reaction strength was higher than at level 7, which did not contain carbon material C.

[0082] Furthermore, comparing levels 10, 12, and 13 regarding the volatile content of the biomass carbon materials, carbon material C with a volatile content of 19.7% by mass and carbon material D with a volatile content of 40% by mass maintained the post-reaction strength of level 7, which does not contain any carbon material, even as their reactivity increased. In contrast, carbon material E with a volatile content of 50% by mass showed a decrease in post-reaction strength, indicating that sufficient post-reaction strength for molded coke cannot be obtained when the volatile content is 40% by mass or higher.

[0083] (Example 6) Table 5 shows the relationship between the overall fluidity of coal A mixed with carbonizer C and the fusion of molded products during carbonization. The fluidity of coal A at this time is the Gieseler maximum fluidity measured by adding 10% by mass of DNPD to the mixture of coal A and carbonizer C. The fusion rate is calculated as the mass percentage of molded coke after carbonization in which two or more molded coke pieces are fused together, and was calculated using the following formula. Fusion rate [%] = (Mass of molded coke fused after carbonization [g]) / (Total mass of molded coke after carbonization [g])

[0084] [Table 5]

[0085] At levels 14-16, the overall fluidity of the mixture of coal A and carbon fiber C was high, resulting in fusion of almost all molded coke. On the other hand, at levels 17 and 18, the overall fluidity of the mixture of coal A and carbon fiber C was below 25,000 ddpm, and the fusion rate decreased significantly. This indicates that fusion problems of molded coke can be avoided by keeping the fluidity of the coal, or the overall fluidity of the mixture of coal and carbon fiber, below 25,000 ddpm. [Industrial applicability]

[0086] According to the present invention, it is possible to produce coke that is highly reactive and has high post-reaction strength. This makes it possible to use carbon-neutral biomass raw materials as blast furnace raw materials, thereby reducing CO2 emissions.

Claims

1. A method for producing molded coke by molding a blended coal mixture made from coal and carbon material, and then carbonizing the resulting agglomerated product, A method for producing molded coke, characterized by preparing the blended coal by blending coal having a particle size of 1 mm or less in proportion of 70% by mass or more, with biomass or carbon material obtained by heat-treating biomass, which also has a particle size of 1 mm or less in proportion of 70% by mass or more, in a proportion of 1% by mass or more and 40% by mass or less based on the total amount of coal and carbon material.

2. The method for producing molded coke according to claim 1, wherein the volatile content of the carbon material is 1% by mass or more and less than 40% by mass on an anhydrous basis.

3. The method for producing molded coke according to claim 1 or 2, wherein the coal has a Gieseler maximum fluidity of 1 ddpm or more and 25,000 ddpm or less as a softening and melting characteristic obtained by adding a primary or secondary amine compound having an aromatic ring.

4. The volume of the aggregated material is 1 cm³ ３ 80cm or more ３ A method for producing molded coke according to claim 1 or 2, wherein the blended coal is molded as follows.

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