Method for pretreating feed material

Abstract

A method for pretreating a feed material, the method comprising: subjecting either coal that is outside the blast-furnace-production range or a coal-substitute solid fuel to a dry distillation treatment under such conditions that the maximum dry distillation temperature is 900°C or higher; separating the combustible substances resulting from the dry distillation treatment into a solid fuel, a liquid fuel, and a gaseous fuel; and blowing some or all of the solid fuel, liquid fuel, or gaseous fuel into a metallurgical furnace.

Description

Raw material pre-treatment method

[0001] The present invention relates to a method for pre-treating raw materials in a blast furnace ironmaking process, including a sintering machine and a carbonization furnace, and in particular to pre-treating and handling raw materials in the blast furnace ironmaking process, and to expanding raw material options and reducing CO2 emissions.

[0002] In the blast furnace method, coke and iron ore are charged from the top of the furnace, and hot air (high-temperature air over 1000°C) and reducing agents such as pulverized coal are blown in through the tuyere at the bottom of the furnace. As a result, the pulverized coal and coke burn, generating a great deal of heat and high-temperature reducing gases (CO and H2), which rise inside the furnace and heat up and reduce the iron ore that descends.

[0003] In addition to low ash and sulfur content, blast furnace coke must have an appropriate porosity and be strong enough to withstand high temperatures without pulverizing. Only a limited range of bituminous coal is used to produce coke that meets these requirements. This type of coal is called coking coal (a classification name for its use), and is distinguished from general coal, which is primarily used as fuel for power generation.

[0004] In a coke oven, crushed and mixed raw coal is placed in a carbonization chamber and indirectly heated at 1,000-1,300°C for 14-20 hours, followed by steaming (dry distillation) to produce coke. By-products of this process include fuel gas (COG) and tar.

[0005] International Publication No. 2023 / 190840 Japanese Patent Application Laid-Open No. 2000-104075 Japanese Patent Application Laid-Open No. 58-160395

[0006] Katsuhiko Yamamoto, Shinichi Misawa, Kazuhiko Koizuka, Ryohei Mimura, "Experiments on the development of applications through carbonization of refuse-derived fuel (RDF)," Journal of the Japan Society of Waste Management, Japan Society of Material Cycles and Waste Management, 2000, Vol. 11, No. 4 Uwe Essmann, "Biochar-pellets as substitute for fossil coal in metallurgical processes," Master's thesis Renewable Energy ENE500, University of Agder, 2018 Japan Institute of Energy, "Biomass Handbook (2nd Edition)," Japan Institute of Energy, 2009 Nippon Steel Corporation, "Recycling technology for general waste plastics using the coke oven chemical raw material recovery method," 58th Okochi Memorial Production Award, Okochi Memorial Society, 2011 Tatsuya Oki, Junichi Tanaka, Harada Taneomi, "Factors of Coal Grindability," Resources and Materials, Japan Society of Materials Science, 1996, Vol. 112, No. 1, pp. 37-42. Takuya Furuzono, Akihiro Hoshino, Tsuyoshi Teramae, Ikuo Hosoya, Toru Yamashita, "Fundamental Study on Grinding Characteristics of Semi-carbonized Pellets," Japan Institute of Energy 54th Coal Science Conference, 2017. Kazuhiko Nakaoji, Yoichi Nakamura, Katsumi Muroi, "Coal Deashing Technology and Its Practical Application," Hitachi Review, Hitachi Review, 1984, Vol. 66, No. 2,

[0007] In a blast furnace, which is a metallurgical furnace, the pulverized coal (PC; Pulverized Coal) injected through the tuyere is subject to fewer restrictions than coking coal, but the quality of the coal is still limited. Therefore, rather than injecting coal or coal substitute solid fuel (tuyere-injected solid fuel) directly through the tuyere, the coal is separated into solid, liquid, and gas in a high-temperature carbonization furnace such as a coke oven. The solid (char) is then injected through the blast furnace tuyere, the gas (COG) is reformed into high-temperature reducing gas and injected into the blast furnace, and the combustible matter in the liquid (tar, etc.) is injected through the blast furnace tuyere. This leads to "reduced decomposition heat of tuyere-injected solid fuel ⇒ increased effective heating value of the fuel ⇒ reduced tuyere-injected solid fuel ⇒ reduced blast furnace fuel ratio and combustion-supporting gas (oxygen)," resulting in reduced CO2 emissions. ２ It can reduce emissions.

[0008] According to the above method, renewable fuels with very high volatile matter (VM) (biopellet, biochar, etc.), refuse-derived fuels such as RDF (refuse-derived fuel; solid fuel produced from combustible municipal waste), and RPF (refuse paper and plastic fuel; solid fuel produced from combustible industrial waste) can be used as blast furnace fuel (reducing material) as a coal-alternative solid fuel. Here, impurities in the waste, such as heavy metals and alkalis, are chlorinated and volatilized by the chlorine in the waste in the high-temperature carbonization furnace and removed from the char, so there is no problem with operating the blast furnace as a metallurgical furnace.

[0009] The use of renewable fuels and waste-derived fuels allows for a reduction in fossil fuels (coal), eliminating the need for CO2 processing costs and energy derived from the reduced fossil fuels (coal) or alternative fuels.

[0010] The steel industry uses fossil fuels such as coal and natural gas as reducing agents and combustion fuel in blast furnaces, a metallurgical furnace, resulting in large amounts of CO2 emissions, and measures to reduce them are highly anticipated. Underground CO2 storage poses challenges, including the need for stable soil and local consensus. CO2 reuse (C recycling) and H2 reduction require large amounts of H2 and green electricity, creating significant economic hurdles, including infrastructure. The present inventors have devised a novel CO2 reduction method for blast furnaces (Patent Document 1). However, even without considering C recycling and underground storage, there is still room for further reductions in CO2 emissions. Furthermore, this invention can reduce the coke ratio to less than one-fifth of that of conventional methods, but reducing coke also reduces the by-product coke breeze. Because coke breeze is used as a sintering agent, the shortage of coke breeze must be compensated for by anthracite. However, anthracite's volatile matter (VM) cannot be effectively utilized thermally, generating tar and causing various problems.

[0011] According to Patent Document 1, the primary combustion heat (reaction of C + 0.5 × O2 = CO) of fuel injected into the blast furnace tuyere is high, and the heat of thermal decomposition (C i H j O k Materials with a low calorific value (calorific value of decomposition into 0.5kcal / 1000kcal / 2000kcal) are preferred, and low VM is also desirable. This is also why LV coal (low VM coal) has recently become the preferred choice for conventional blast furnace PCI (Pulverized Coal Injection) equipment. Biochar tuyere injection is being considered worldwide as a CO2 reduction measure, as biofuel has a very high VM. The idea is to carbonize biofuel (carbonized at 400-700°C) at collection sites, reduce its VM (increased calorific value) to the same level as anthracite or MV coal (medium VM coal), and then inject the resulting material into the furnace. However, the yield of char from biomass carbonization is only about 20%, and gases and tars are difficult to utilize effectively beyond the heat required for carbonization, resulting in low energy efficiency.

[0012] Meanwhile, greenhouse gas emissions from waste incineration in Japan amount to approximately 40 million tons, accounting for 3% of Japan's total emissions and equivalent to approximately 40% of emissions from the steel industry.

[0013] Increasingly, power generation equipment is being installed at municipal waste incineration facilities to effectively utilize waste heat. However, issues remain regarding incineration residues caused by chlorine, alkali, and heavy metals in the waste. Corrosion problems on boiler walls mean that power generation efficiency is low at approximately 15% nationwide, and energy efficiency, including self-consumption power, is even lower. Furthermore, from the perspective of reducing CO2 emissions, power generation using incinerators and RDF / RPF does not necessarily reduce CO2 emissions. Thermal recycling, however, offers the potential to reduce fossil fuel use for thermal power generation by increasing the amount of power generated. Biomass power generation and renewable fuel power generation also fall under the category of thermal recycling. To achieve substantial CO2 reductions, it is important to rationally implement material and chemical recycling.

[0014] In a method for pre-treating raw materials according to an embodiment of the present invention, coal or coal substitute solid fuel outside the range of coke production is carbonized under conditions where the carbonization temperature reaches a maximum of 900°C or higher, the combustible materials produced by the carbonization process are separated into solid fuel, liquid fuel, and gaseous fuel, and some or all of the solid fuel, liquid fuel, or gaseous fuel is then injected into a metallurgical furnace such as a blast furnace.

[0015] By using the above-mentioned pre-treatment method of raw materials, coal or coal substitute fuel (hereinafter referred to as coal, etc.) as the injected solid fuel can be replaced with char (C + Ash) with almost no volatile matter (VM) in a high-temperature carbonization furnace with a maximum temperature of 900°C or more. Since the decomposition heat of the solid fuel injected into the blast furnace tuyere is eliminated and the heat generation is increased, the blast furnace tuyere injection solid fuel ratio (kg / tp) and the oxygen ratio as a combustion support gas required to produce 1 ton of molten iron are lower than when coal, etc. is injected directly from the blast furnace tuyere. 3 / tp). This also makes it possible to use high VM fuels such as HV coal, biomass solid fuel, and waste-derived fuel as reducing materials for blast furnaces. Impurities in the waste, such as heavy metals and alkalis, are chlorinated and volatilized by the chlorine in the waste in the high-temperature carbonization furnace and removed from the char, so there is no disruption to blast furnace operation.

[0016] The above-mentioned pre-treatment method of raw materials increases the amount of gas (COG; Coke Oven Gas) generated in coke ovens and high-temperature carbonization furnaces (hereinafter referred to as high-temperature carbonization furnaces, etc.) compared to when coal is directly injected into a blast furnace. COG is mainly hydrogen, but CH ４ It also contains components such as H and CO2. ２ If it is converted into CO and heated and then injected into a blast furnace, it can promote the gas reduction of ore, thereby reducing the use of other fuels.

[0017] The above-mentioned raw material pretreatment method results in a larger amount of combustible liquids (such as tar and crude light oil, hereafter referred to as tar, etc.) being generated in high-temperature carbonization furnaces and other furnaces than when coal is directly injected into a blast furnace. Tar, etc., can also be used as combustion fuel in ironmaking equipment (hot stoves, coke ovens, and sintering machines), but it is preferable to use it as a reducing agent for tuyere injection, and even better, as oil (both a means of transportation and as tuyere injection fuel) for COM (Coal Oil Mixture), which is the means of transporting and injecting solid fuel into the blast furnace tuyere.

[0018] The char produced by the above-mentioned raw material pretreatment method can also be used as a coagulant for sintering machines, solving the problems that arise when using anthracite as a coagulant for sintering machines. Furthermore, when producing char for coagulant, COG and tar, which are by-produced in high-temperature carbonization furnaces, are increased in quantity and can be used as a reducing agent in blast furnaces, thereby reducing the fuel rate (reducing agent rate) in blast furnaces and, when COM is used, can also be used as the oil.

[0019] As described above, by pre-carbonizing coal in a high-temperature carbonization furnace, regardless of whether it is caking or not, and extracting the three phases of fuel - solid, liquid, and gas - and using them appropriately according to their phases, it is possible to reduce the amount of fossil fuel used in the entire iron-making facility, including the blast furnace, sintering machine, and coke oven.

[0020] FIG. 1 shows an overall flow diagram of this embodiment, in which char is supplied to a blast furnace from the lower tuyere. FIG. 2 shows an overall flow diagram of the reducing agent and coagulating agent before this embodiment is applied. FIG. 3 shows a flow diagram in which this embodiment is applied only to the blast furnace tuyere injection line of FIG. 2. FIG. 4 shows a flow diagram in which this embodiment is also applied to the coagulating agent for the sintering machine in addition to the flow diagram of FIG. 3. FIG. 5 compares the carbonaceous material processing flow diagram of this embodiment with the conventional PCI method. FIG. 6 shows a nitrogen / chlorine balance diagram according to the mixture ratio of coal and chlorine-containing fuel. FIG. 7 shows an overall flow diagram of this embodiment, in which char is supplied to a blast furnace from the top and lower tuyere. FIG. 8 shows a model of unreacted nuclei when chlorine-containing waste is formed into spherical briquettes. FIG. 9 shows Table 1 showing the components of RDF from Non-Patent Document 1. FIG. 10 shows Table 2 showing the proximate analysis values, elemental analysis values, and LCV values ​​for coking coal, LV coal, and HV coal, respectively. Fig. 11 is Table 3 showing a comparison of estimated carbon consumption results for the case in which LV coal is used in Fig. 2 and the case in which LV coal or HV coal is used in Fig. 3, in which this embodiment is applied to a blast furnace tuyere injection line. Fig. 12 is Table 4 showing the case in which LV coal or HV coal is used in Fig. 4, in which this embodiment is also applied to the sintering machine as an agglomerate. Fig. 13 is Table 5 showing the case in which LV coal or HV coal is used in Fig. 1, which serves as a model case for this embodiment. Fig. 14 is Table 6 showing a comparison of carbon consumption between the case in Fig. 1 and the case in Fig. 7, when the HV coal in Table 2 (Fig. 10) is used.

[0021] Several exemplary embodiments will be described below with reference to the accompanying drawings, which illustrate typical facilities related to the present embodiments, but note that the drawings do not show detailed information, including auxiliary facilities and combustion fuel.

[0022] Throughout the following description and the appended claims, each term is used in a way that is consistent with the definition known to those skilled in the art. However, it should be noted that some terms have the following meanings: "Lower furnace" refers to the cohesive zone and below it, or the region where the temperature (above 1200-1300°C, depending on the reduction rate of the ore) is such that the permeability deteriorates due to softening of the ore. "Partial combustion" refers to combustion that does not reach complete combustion. "Primary combustion" refers to the reaction of C + 0.5 O2 = CO, and the reaction of CO and H from coke and fuel injected into the tuyere. ２ , H ２ This refers to partial combustion that generates S, and the heat generated by primary combustion is called "primary combustion heat." Both "fuel ratio" and "reducing agent ratio" refer to the total weight (kg / tp) of coke and tuyere-injected fuel (also called tuyere-injected reducing agent) required to produce 1 ton of pig iron. In principle, the two terms are synonymous, but since reducing agent is often used to distinguish it from combustion fuel, both terms are used depending on the context. Note that unless otherwise specified, the fuel ratio does not include reducing gas (CO, H2) injected from the tuyere for top gas circulation, etc. "Low-temperature carbonization," "medium-temperature carbonization," and "high-temperature carbonization" are terms used to classify relatively slow pyrolysis methods by carbonization temperature, and although these terms have not been fully agreed upon even among those skilled in the art, here we define low-temperature carbonization as the temperature range for torrefaction, medium-temperature carbonization as the temperature range for general biochar (VM = approximately 5-25%) production, and high-temperature carbonization as the temperature range for coke or bio-coke (residual VM = several percent), with temperatures of "200-300°C," "400-700°C," and "900-1300°C," respectively.

[0023] The pulverized coal injection (PCI) method, which injects pulverized coal into a blast furnace, involves injecting pulverized coal into the blast furnace through the tuyere. The purpose of this method is to replace expensive, valuable coke (lump coke charged from the top of the blast furnace) with cheaper, non-caking coal, and finely pulverized coal (VM = 10-40%) is used to improve combustion efficiency. Therefore, even if anthracite or coke breeze (the off-yield of lump coke) is pulverized and used in special circumstances, it is clear that there is no rationale for pulverizing lump coke (the main product of a coke oven) and injecting it through the tuyere.

[0024] The operating method disclosed below has been devised in contradiction to the common sense of those skilled in the art, and generally speaking, rather than injecting coal directly into the blast furnace through the tuyere, carbide that has been subjected to high-temperature carbonization is intentionally introduced into the furnace, along with gas and liquid fuel that are by-produced in the gas refining equipment (ancillary equipment such as a high-temperature carbonization furnace).

[0025] Specifically, coal or coal-substitute solid fuel outside the scope of blast furnace coke production is first carbonized at temperatures of up to 900°C or higher to separate it into solid fuel as char (C and ash) and the remaining crude gas. Next, the crude gas is separated in a gas refinery into gaseous fuel as COG, liquid fuel such as tar, and residual liquid mainly consisting of water (corresponding to ammonia water in coal carbonization and wood vinegar in biomass carbonization). In other words, solid fuel (char), liquid fuel (tar, etc.), and gaseous fuel (COG) are extracted from the charged raw materials through the carbonization process and a process to separate combustibles.

[0026] Furthermore, for solid fuel, some or all of it is coarsely crushed in a coarse crusher to obtain coarse char, which is used as a coagulant for sintered ore. The solid fuel is then finely crushed so that the proportion of particles with a particle size of 0.1 mm or less is 70% or more, and some or all of this solid fuel is then injected through the blast furnace tuyeres at the bottom of the furnace. For gaseous fuel, some or all of it is reformed to produce (reducing) synthesis gas (reducing gas) mainly composed of CO and H2, which is then injected into the blast furnace body at a temperature of 800°C or higher. For liquid fuel, some or all of it is injected into the furnace through the blast furnace tuyeres at the bottom of the furnace.

[0027] This embodiment will be described in more detail below.

[0028] The most important role of the coke (lump coke) charged into a blast furnace is to maintain the air permeability and liquid permeability in the lower part of the furnace, and it is required to have high-temperature strength, a small particle size, and low reactivity. Therefore, raw coal, which has been blended with caking properties and VM, is carbonized in a coke oven at 1000-1300°C, and only the lump coke of the required particle size is finally charged into the blast furnace. Lump coke also serves as a reducing agent (for direct reduction and gas reduction) and a heat source (a source of thermal energy through combustion), and so far, far more coke has been charged than is necessary to ensure the air permeability and liquid permeability in the lower part of the furnace.

[0029] In contrast, the PCI method is a technology that uses inexpensive, non-caking coal to take on the role of coke's reducing agent and heat source. To increase combustion efficiency, the specific surface area is increased by finely pulverizing the coal so that the proportion of particles below 200 mesh (74 μm) is 70-80% or more. Coal quality has also been researched, ranging from HV coal (high VM coal) to LV coal (low VM coal), and there has been a shift from HV coal, which emphasizes combustion efficiency, to LV coal, which has a high calorific value as the PC ratio increases. In recent years, research has been conducted worldwide on mixing biomass-derived charcoal with PC as a CO2 reduction measure, but this is an extension of conventional PCI technology.

[0030] The inventor of the present application has devised a method for reducing CO2 in the blast furnace process (Patent Document 1). According to the method for reducing CO2 in the blast furnace process described in Patent Document 1, the fuel injected into the blast furnace tuyere generates a high primary combustion heat and a low thermal decomposition heat (C i H j O k = i × C + 0.5j × H2 + 0.5k × O2) is desirable to have as small a heat of decomposition as possible. The heat of thermal decomposition of coal is also the heat of thermal decomposition of VM (volatile matter), so LV coal is desirable for blast furnace tuyere injection fuel. This is a common issue with the conventional PCI method.

[0031] In order to solve the problem of difficulty in using HV coal, we have devised a method in which coal with a VM of 6% or more is not directly fed to the lower part of the blast furnace, but is instead carbonized into solid fuel (char) with a VM of <5% (preferably ≦1%) in a high-temperature carbonization furnace where the maximum temperature is 900°C or higher, and then combined with gaseous fuel (COG) and liquid fuel (tar, etc.) by-produced in the gas refining equipment attached to the high-temperature carbonization furnace, this is supplied to the blast furnace by the means most suitable for each fuel.

[0032] The high-temperature carbonization furnace is designed to block outside air and maintain a maximum carbonization temperature of 900°C or higher. It is equipped with gas purification equipment and is preferably installed near the blast furnace for logistics reasons. There are no restrictions on the type; equipment such as vertical coke ovens is acceptable, and many conventional coke ovens can be reused, including CDQ (coke dry quenching). While separate carbonization furnaces and cooling equipment are required to produce coke and char, shared gas purification equipment is acceptable. The carbonization temperature must be 900°C or higher because there is a correlation between the carbonization temperature and gasification (pyrolysis) of coal, and gasification, including H2, is completed at around 900°C.

[0033] FIG. 5 compares the conventional PCI method with this embodiment.

[0034] In the conventional PCI process, attempts have been made to use biomass to reduce CO2 emissions by mixing biochar (wood-based biochar is also called charcoal) with coal, with a VM of approximately 6-25%. Due to the properties of biomass (low bulk density, high moisture content, low carbonization yield, etc.), it is typically carbonized in a medium-temperature dry distillation furnace 14 at 400-600°C at biomass collection sites and then transported to the consumer (steelworks). Because the coal contains moisture, it is first dried in a dryer 13 to a moisture content of 1% or less, then pulverized in a pulverizer 7 before being injected into the blast furnace 1 through the tuyere (not shown) as PCI.

[0035] In this embodiment, coal and other fuels delivered to a steelworks are separated into solid fuel (char), liquid fuel (tar, etc.), gaseous fuel (COG), and a water-based residual liquid (corresponding to ammonia water in coal carbonization and wood vinegar in biomass carbonization) in a high-temperature carbonization furnace 2, and only the fuel excluding the residual liquid is supplied to a blast furnace 1. The char is finely pulverized in a fine pulverizer 7 to a particle ratio of 0.1 mm or less of 70% or more and then injected through a blast furnace tuyeres at the bottom of the blast furnace. The COG is partially burned in a reforming / heating furnace (hot stove) 5 or reformed into a reducing gas (synthetic gas) mainly composed of CO and H using a medium gas (HO, CO) before being injected into the blast furnace 1. Tar and other fuels are injected into the blast furnace through a blast furnace tuyeres at the bottom of the blast furnace. The solid fuel (char) is preferably pulverized using a fine pulverizer 7 for blast furnace injection.

[0036] Since the VM in the coal is separated in advance and char is injected from the blast furnace tuyeres, the endothermic reaction due to the thermal decomposition of coal (including the heat rise of the residual liquid removed in the high-temperature carbonization furnace 2 and the heat of thermal decomposition) disappears, and the calorific value (kJ / kg) increases. Therefore, the fuel ratio (kg / t) and oxygen ratio (Nm 3 / t) can be reduced.

[0037] The char is pulverized in a pulverizer 7 to increase its specific surface area (∝ combustion rate) and then injected through a dedicated injection lance in the lower tuyeres of the furnace. The grindability index, HGI (Hardgrove Grindability Index; the higher the number, the easier it is to grind), increases depending on the carbonization temperature and degree of carbonization (Non-Patent Documents 5 and 6). Therefore, HV coal, biomass fuels, etc. can also be easily pulverized by carbonization, reducing the energy required for pulverization.

[0038] Since COG is recovered at room temperature, when it is injected into a blast furnace as a reducing gas, it must be preheated to a temperature above the temperature of the injection point, otherwise it will become a cold heat source and cool the charge inside the furnace, which is not desirable. Even when it is injected into the shaft, it is desirable to heat it to 800°C or higher, but the gas contains hydrocarbon gases such as CH4, and if it is heated to 800°C or higher, soot will be generated due to the cracking phenomenon (CH4 = C + 2H2). Therefore, it is necessary to partially burn the hydrocarbons (C n H m It is desirable to reform the gas into a reducing gas (synthetic gas) mainly consisting of CO and H2 in a high-temperature atmosphere using a gas mixture (CO + 0.5n O2 = n CO + 0.5m H2) or a medium gas (H2O, CO2) before injecting it into the blast furnace. Injecting the reducing gas at an appropriate temperature and in an appropriate location increases the gas reduction rate and makes it possible to reduce the fuel ratio (reducing agent ratio) (Patent Document 1).

[0039] Tar and other materials are recycled chemically and used as reducing agents by being injected into the furnace through the tuyeres in the same way as in the conventional heavy oil injection method. It is preferable to inject them into the tuyeres at the bottom of the furnace using a dedicated injection lance similar to that used for heavy oil.

[0040] The effects of the above-described embodiments will be explained in light of the outside of the "steelworks boundary" shown in Figure 5. In the conventional PCI route, biochar is produced in a medium-temperature carbonization furnace 11, which is generally installed in a biomass collection area. Since the yield and VM of biochar are inversely correlated with the carbonization temperature, the yield of low-VM biochar suitable for PCI is low at 20-30%, and since by-product gases and tar are difficult to use for anything other than combustion heat in the carbonization furnace, the net energy yield of the carbonization furnace (= latent heat of recovered fuel / (latent heat of charged raw materials + external input heat)) is low.

[0041] In this embodiment, the high-temperature carbonization furnace 2 is installed within the steelworks, and since COG and tar derived from VM can be utilized within the plant, the charged raw material can be a high-VM fuel. Therefore, at the biomass collection site, fuel production equipment that prioritizes energy yield, such as a low-temperature carbonization furnace (semi-carbonization furnace) 15 at 200 to 300°C or a solidification facility 16 at less than 200°C, can be adopted.

[0042] Figures 2 (an example in which this embodiment is not applied; see Patent Document 1) and 3 (an example in which this embodiment is applied) summarize the flow within the steelworks boundary shown in Figure 5 into an ironmaking process flow that includes a coke oven 3 and a sintering machine 9. In both examples, gas reforming is assumed to be performed using partial combustion with oxygen in a hot stove (reforming / heating furnace) 5. The flow charts allow for the recycling of furnace top gas from which CO2 has been removed in a CO2 separator 4, and for the amount of reducing gas produced and heated in the hot stove 5 to be adjusted based on the amount of reducing gas required in the blast furnace 1. Furthermore, in both examples, anthracite is used to make up for the shortage of coke fines as a coagulant for the sintered ore produced in the sintering machine 9. The term "screen" is used in the flow charts to refer broadly to a classifier 10, and it may be a literal screen type, or may be a wind-powered classification or fluidized bed type (as is also true in other figures).

[0043] The amount of coagulant used per ton of pig iron is calculated by the ore ratio: OR (kg / tp; amount of ore charged per ton of pig iron), the sinter ratio: SR (%; percentage of sintered ore in the charged ore), and the coagulant ratio: C. str (kg / ts; amount of coagulated material per ton of sintered ore) OR × SR × C strOn the other hand, the amount of coke breeze supplied is determined by the coke ratio: CR (kg / tp; amount of coke per ton of hot metal), the lump coke ratio: R cc (%; lump coke weight yield relative to raw coal), coke breeze ratio: R fc (%; coke fines weight yield to raw coal) CR × R fc / R cc Therefore, the shortage of coking agent (coke powder) per ton of pig iron: L c (kg / tp) is L c = OR x SR x C str -CR×R fc / R cc (1) and the shortfall is generally made up by anthracite.

[0044] It is clear that the shortage increases as the first term on the right-hand side of equation (1) increases or the second term decreases (and vice versa). Self-fluxed sinter (sinter containing auxiliary materials for adjusting slag basicity) is highly reactive in the blast furnace, and as high-quality lump ore becomes scarce, SR (∝ first term) is on the rise. Meanwhile, CR (∝ second term) is also decreasing due to the increase in PC ratio and the trend toward CO2 reduction, resulting in a growing shortage of coke fines. According to the method described in Patent Document 1, CR can be reduced to less than one-fifth of that achieved by the conventional blast furnace method, making the shortage of coke fines a critical issue.

[0045] On the other hand, there have been problems with using anthracite in sintering machines, and the amount of anthracite used has been limited. Another feature of this embodiment is that "instead of using anthracite to make up for the shortage of coagulant, it is made up with char produced by high-temperature carbonization (carbonization) of coal, etc.", and at the same time, "liquid fuel (tar, etc.) and gaseous fuel (COG) produced as by-products in the carbonization are recovered, and the COG is reformed into a reducing gas (synthetic gas) mainly composed of CO and H2 using partial combustion or a medium gas (H2O, CO2), and then injected into the blast furnace body, and the tar, etc. are injected into the furnace from the tuyere at the bottom of the blast furnace."

[0046] The raw materials (coal, coal alternative fuels, etc.), equipment (high-temperature carbonization furnaces, gas refining equipment, etc.), and operating methods (carbonization temperature, carbonization time, etc.) required for this process can be shared with blast furnace injection char production, which means that equipment and operating efficiency can be increased synergistically. Figure 4 shows the integrated ironmaking process flow.

[0047] The "anthracite" and "LV coal" in Figure 3 are combined into "steam coal / coal alternative fuel" in Figure 4, and the entire amount is processed in the high-temperature carbonization furnace 2. A portion of the carbonized solid fuel (char) is used as a sintered ore agglomeration material as coarse char, and the remainder is injected into the blast furnace as fine char.

[0048] The destinations of the liquid fuel (tar, etc.) and gaseous fuel (COG) produced as by-products in the high-temperature carbonization furnace 2 in Figure 4 are the same as those in Figure 3, but the supply amount increases by the amount of sintered ore agglomeration material used in the sintering machine 9 added to the high-temperature carbonization furnace 2. In other words, in the past, even if anthracite was used as a agglomeration material, its VM latent heat could hardly be effectively utilized, but in this embodiment, it can be effectively recovered and utilized as liquid fuel and gaseous fuel.

[0049] The combustion time of the coagulant is roughly proportional to the square of the particle size. This determines the combustion pattern (combustion temperature and retention time in the sintering bed), which affects sinter quality and yield. Therefore, a narrow particle size range is desirable. Therefore, it is desirable to control the particle size within a range of, for example, 2–3 mm. However, fine classification of moist materials is difficult (the meshes tend to clog). Until now, even when using coke breeze, particles smaller than 1 mm and particles larger than 5 mm have been included. The char discharged from the high-temperature carbonization furnace is dry-cooled to approximately 150°C in a coke dry quenching (CDQ) system (not shown) for the purpose of sensible heat recovery, just like conventional coke, and then coarsely crushed. This completely dry char facilitates screening and air classification. Furthermore, undersize materials, for example, smaller than 2 mm, do not result in yield loss and can be fed to the blast furnace injection fine crusher 7, allowing the particle size range sent to the sintering machine 9 to be controlled within a narrow range. The exact particle size range is determined by factors such as the exhaust gas suction speed of the sintering machine and the FFS (Flame Front Speed), but it is desirable to use coarse powder with a particle size of at least 1 mm to 6 mm as a sinter ore agglomeration agent.

[0050] Since particle size control of the coagulant is also effective for coke breeze, in Figure 4, a line for charging coke breeze of, for example, less than 3 mm or more than 5 mm into the high-temperature carbonization furnace 2 is shown with an asterisk (*) in parallel with the line for supplying coke breeze to the mixer 8.

[0051] The pulverized char injection method in Figures 3 and 4 assumes pneumatic transport, similar to the conventional PCI process. Because high-temperature carbonized pulverized char contains almost no VM, pneumatic transport poses little risk of coal dust explosions. However, pneumatic or nitrogen transport introduces N2 into the furnace. Considering compatibility with CO2 separation (which is difficult to separate) and the top gas circulation system (which tends to concentrate N2), a reducing gas (such as top gas after decarbonation) is preferable. Because this is a pressurized system injecting char into a pressurized blast furnace, external air is less likely to enter the injection system. This allows for the use of preheated pneumatic gas, which increases the sensible heat of the injected char and gas, thereby reducing fuel and oxygen consumption. Indirect heating of the transport piping using an electric heater or steam from outside the pneumatic transport system is also an effective method for increasing the sensible heat of the injection.

[0052] Methods other than pneumatic transport can be used to inject pulverized char into the blast furnace tuyere, and when injecting liquid fuel (tar, etc.) at the same time, it is most rational to use a coal oil mixture (COM). Figure 1 shows the process flow.

[0053] COM12 is a facility that converts finely divided solid fuel into a slurry and transports it using oil such as heavy oil or tar as the transport medium. In Figure 1, finely divided char and liquid fuel such as tar are mixed in advance and injected into the blast furnace as COM fuel. Since the usual upper limit for slurry concentration (the proportion of solids in the total weight transported) is around 50%, when the feedstock is bituminous coal, auxiliary liquid fuel (reducing agent) such as heavy oil is added to prevent the slurry concentration from becoming too high. Furthermore, since the amount of finely divided char can be reduced in proportion to the amount of oil added, there is no deterioration in overall energy efficiency or CO2 emissions.

[0054] The yield of solid and liquid fuels in high-temperature carbonization furnaces (the ratio of recovered material to the weight of raw materials such as coal) varies depending on the raw material (e.g., coal) and VM. Generally, as VM increases, the yield of solid fuel decreases and the yield of liquid fuel increases. When wood-based biomass fuel is carbonized at 1000°C, the yield is roughly 20% solid, 55% liquid, and 25% gas (Non-Patent Document 2). Subtracting the approximately 30% yield of wood vinegar, which cannot be used as fuel (Non-Patent Document 3), from the 55% liquid yield results in a solid fuel:liquid fuel:gaseous fuel ratio of 20%:25%:25%, resulting in a slurry concentration of approximately 44% (<50%). When waste plastic is carbonized at high temperatures, the ratio of solid fuel:liquid fuel:gaseous fuel is 1:2:2 (Non-Patent Document 4), resulting in a slurry concentration of approximately 33% (<50%). In other words, depending on the type and blend ratio of the coal alternative fuel, auxiliary liquid fuels such as heavy oil may not be necessary. Even if coal alternative fuels are not used, CO2-free auxiliary liquid fuels such as biomass tar or E-fuel can be used instead of heavy oil.

[0055] By applying COM, it is possible to integrate the two control systems for the pneumatic and liquid systems into one, and the tuyere injection lance can also be integrated. Furthermore, the liquid vaporization heat can be used to protect the lance from the extreme temperatures inside the furnace. Also, although the liquid temperature of heavy oil-based COM is usually less than 100°C, it is easy to indirectly heat it up to near the boiling point of the liquid fuel (for example, 200°C, as both heavy oil and tar have a range of boiling points) before it is injected into the tuyere. By increasing the sensible heat of the solid and liquid fuels, the fuel ratio (kg / tp) and oxygen ratio (Nm 3 / tp) can be reduced. In addition, the vaporization of liquid fuel is promoted by heating, which improves the COM combustion rate.

[0056] The features of this embodiment, focusing on the process, have been described above. Next, the options for alternative coal fuels in this embodiment and their features will be described.

[0057] In this embodiment, biomass fuel (including semi-carbonized fuel) can of course be used as an alternative fuel to coal, but in addition, refuse-derived fuels (RDF, RPF, etc.) containing a certain amount of impurities can also be used. When using waste, impurities and non-combustible materials contained in the garbage are an issue, and pre-sorting and pre-processing are important, just like other methods of using refuse-derived fuel. However, the following points make it easier to use waste in this embodiment compared to other methods.

[0058] First, the method of burning waste to generate steam power has the problem that chlorides in the waste corrode metal walls, including boiler walls, and generate large amounts of dioxins. This is the cause of the low power generation efficiency of incinerators, and even when power generation is done using RDF with a chlorine concentration controlled to around 1% or less, it leads to increased countermeasure burdens and restrictions on the amount of RDF that can be fed, which undermines the cost advantage (economic viability) of waste-to-energy and hinders its widespread adoption.

[0059] Another method, similar to this embodiment, involves chemical recycling of waste plastics (waste plastics) by mixing them with raw coal and charging them into a coke oven (Patent Document 2, Non-Patent Document 4). The advantage of this method is that, in the high-temperature, reducing atmosphere of the coke oven, over 90% of the chlorine contained in the waste plastics is converted into HCl and detoxified as ammonium chloride (NH4Cl) when cooled with ammonia water containing ammonia derived from nitrogen derived from the raw coal. However, despite the ability to detoxify 5.3 kg / t-coal (150 mol / t-coal) of chlorine per ton of charged coal, the coke strength begins to decrease for reasons other than chlorine even with only 1-2 wt% of waste plastic (approximately 0.2-0.4 kg / t-coal in chlorine), limiting the effective waste plastic loading ratio to a few wt%. Furthermore, this method is limited to waste plastics as a coal alternative fuel, and does not target biomass fuels or waste materials other than plastics.

[0060] This embodiment, like Patent Document 2, uses a high-temperature carbonization furnace and can neutralize chlorine in the raw materials. However, because it produces coarse or fine char instead of coke, there are no raw material constraints necessary for coke strength, allowing the waste plastic charging ratio to be increased up to the balance limit with coal-derived ammonia (5.3 kg-Cl / t for coking coal). According to Patent Document 2, it is possible to increase the chlorine content of waste plastics with 2 wt% chlorine up to 26 wt% of the raw coal. Since the N and Cl content in coal and the N content in waste plastics are 0.045 wt%, 1.59 wt%, and 0.4 wt%, respectively, the weight ratio of nitrogen (N) to chlorine (Cl) in the raw materials charged to the high-temperature carbonization furnace (N / Cl) is 3.0. If the waste plastics were replaced with RDF while using the same coal, the RDF described in Non-Patent Document 1 would contain the components shown in Table 1 in Figure 9. As shown in Table 1, although the chlorine content is high (>1 wt%), a maximum of 37 wt% of RDF can be charged while the N / Cl ratio is 3.0. Note that the RDF carbonized material in Table 1 (Fig. 9) is RDF carbonized at 500°C.

[0061] The above is a charging restriction for detoxifying hydrogen chloride generated from chlorine in the charging materials with ammonia generated from nitrogen also in the charging materials, but in this embodiment, the chlorine can be effectively utilized in the furnace before being detoxified, thereby further increasing the RDF charging rate. Before explaining this point, impurities in waste will be explained in relation to it.

[0062] RDF, a solid fuel derived from municipal waste, has quality issues in that it contains impurities such as heavy metals and alkalis in addition to chlorine. When RDF is used as fuel for thermal power generation, it causes problems such as deposits and material corrosion on boiler walls, just like chlorine, and increases the cost of treating exhaust gas and fly ash.

[0063] When using RDF as blast furnace tuyere injection fuel, issues arise, including pig iron quality and RDF quality, which affects blast furnace operation, as well as RDF properties (proximate analysis values: FC, VM, ash, and moisture content). For example, the RDF shown in Figure 9 (Table 1) (Non-Patent Document 1) cannot be used as blast furnace tuyere injection fuel because its VM is too high and the heat of decomposition cools the lower part of the furnace. The RDF char shown in Figure 9 (Table 1) (Non-Patent Document 1) is obtained by carbonizing RDF at 500°C. However, due to the low char yield (approximately 30%), the ash content of the char is concentrated / increased to 43.3% dry, making it unsuitable for tuyere injection fuel.

[0064] It is well known that if chlorine is contained in the raw materials charged into a high-temperature carbonization furnace, chlorine (Cl2) and hydrogen chloride (HCl) will be generated by thermal decomposition. It is also well known that high-temperature chlorine-based gases chlorinate many oxides and metals to produce chlorides with high vapor pressures, and this has been used for heavy metal recovery, etc., as the chlorination roasting method (chlorination volatilization method).

[0065] In this embodiment, the high-temperature reducing atmosphere of the high-temperature carbonization furnace and the chlorine carried in the raw materials such as waste are actively utilized, and the charge materials are subjected to reductive chlorination roasting in parallel with the carbonization, and heavy metals and alkalis in the ash are chlorinated and volatilized, thereby improving the quality of the carbide and deashing it.

[0066] The chlorination reaction of a metal element M to its oxide is expressed by the following formula: MO a + b × Cl2 = MCl 2b + a / 2 × O2 ΔG 0 0<0 (2) Standard free energy change (ΔG 0 ) is ΔG 0 The reaction will not proceed unless the reaction is <0, but the chlorination reaction is 0 <0. Chloride volatilization has been considered for use in treating heavy metals in incineration ash from municipal waste, but because it was assumed to be in an oxidizing atmosphere, it was thought that the heavy metals that could be volatilized were limited. However, the atmosphere inside a high-temperature dry distillation furnace is one in which CO and H2 gases are generated and carbide (C) is produced, and the following reaction also occurs in parallel: C + 1 / 2 x O2 = CO ΔG0 C <0 (3) CO+1 / 2×O2=CO2 ΔG 0 CO <0 (4) H2+1 / 2×O2=H2O ΔG 0 H2 <0 (5)

[0067] Multiplying equations (3), (4), and (5) by a and adding them to equation (2) gives MO a + a × C + b × Cl2 = MCl 2b + a × CO ΔG 0 0+ΔG 0 C (6) MO a + a × CO + b × Cl2 = MCl 2b + a × CO2 ΔG 0 0+ΔG 0 CO (7) MO a + a × H2 + b × Cl2 = MCl 2b + a × H2O ΔG 0 0+ΔG 0 H2 (8) At 300 to 1200°C, -500 < ΔG 0 C ,ΔG 0 CO ,ΔG 0 H2 <-300 kJ / mol, and the free energy change in equations (6), (7), and (8) is significantly lower than that in equation (2), making the reduction-chlorination reaction more likely to proceed in terms of free energy. Note that chlorine is consumed in the reaction with hydrogen to produce hydrogen chloride (H2 + Cl2 = 2HCl), so it is important to check whether the free energy change is lower than the standard free energy change for this reaction.

[0068] Furthermore, in the carbonization chamber of a vertical coke oven, for example, the charge material is heated from the oven wall toward the center, allowing the chlorine-containing gas to come into contact with the charge material over a wide temperature range. This allows for a sequential reduction-chlorination reaction during the heating process, with chlorides at low temperatures and high vapor pressures gradually volatilizing. Consequently, various oxides can be reduced and chlorinated and volatilized by the end of the carbonization process (up to completion of carbonization at 900°C or higher). Furthermore, since the temperature of the chlorine-generating gas is lower than the chlorination volatilization reaction temperature, depending on the width of the coke oven from the oven wall to the center, the generated chlorine gas may flow upward through the cooler charge material, significantly reducing the efficiency of the chlorination volatilization reaction. However, the efficiency of the chlorination volatilization reaction can be improved by pre-treating some or all of the chlorine-containing charge material in advance (e.g., into briquettes or injection moldings) before charging it into a high-temperature carbonization furnace (e.g., a coke oven).

[0069] Figure 8 shows a model of unreacted nuclei assuming a spherical briquette. During the heating process after charging, a temperature gradient develops in the thickness direction (radial direction) within the briquette. Chlorine gas generated in the low-temperature region within the briquette (chlorine gas generation surface; radius R1 in Figure 8) passes through the chlorination volatilization temperature surface of impurity A (impurity A reaction surface; radius R2 in Figure 8) as it is exhausted from the briquette surface (high temperature close to the furnace temperature). This causes impurity A on this surface to be chlorinated and volatilized. The chlorine gas reaction surface and the impurity A reaction surface begin near the briquette surface immediately after charging and move inward with carbonization time (as R1 and R2 approach zero). Therefore, chlorination and volatilization proceed throughout many regions within the sphere. Impurities other than A also have corresponding volatilization temperatures, but chlorine gas always passes through this temperature region (R2, different from A), allowing it to be chlorinated and volatilized. Briquetting can therefore efficiently remove impurities with chlorination volatilization temperatures lower than the carbonization temperature. Furthermore, the excess chlorine gas discharged from the briquettes is given an opportunity to react with the unreacted charge on the flow path, and the longer the flow path, such as in a vertical coke oven, the more likely it is that the reaction efficiency will improve.

[0070] As shown in Figure 8, if R1 and R2 are far apart, the impurities below R2 cannot be volatilized by the chlorine in the briquette when R1 reaches the center of the furnace. In other words, the temperature gradient within the briquette is important. The chlorine concentration, moisture, and oil content within the briquette, as well as their latent heat of gasification (cold heat source), promote a steeper temperature gradient, improving reaction efficiency. Furthermore, because gas flows upward in a coke oven, charging briquettes with high chlorine, moisture, and oil content in the lower layer and briquettes or powder with low chlorine, moisture, and oil content in the upper layer can also delay chlorine gas generation in the lower layer and increase the temperature rise rate in the upper layer, thereby promoting the chlorination volatilization reaction in the upper layer, improving impurity removal efficiency and the effective utilization of chlorine gas.

[0071] The above explanation uses briquettes as an example, but injection-molded products such as RDF and RPF, or pellets, are also acceptable. Regarding the shape, a round shape is ideal, but cylindrical or pillow-shaped shapes are also acceptable. Regarding the coke shape, vertical coke has a higher reaction efficiency, but horizontal coke can also be effectively used if it is made into briquettes, etc.

[0072] A detailed investigation of the free energy changes in the chlorination reaction and the vapor pressure of chlorides for the major components contained in RDF revealed that heavy metals (Zn, Pb, Cu) and alkali metals (Na, K), which affect the blast furnace conditions and pig iron quality, can be volatilized and removed. Furthermore, it was found that Fe, Mn, Mg, and Ca can also be volatilized and removed, which has the benefit of reducing ash (decalcification). Conversely, it was found that while Si, Al, and Cr can be chlorinated and volatilized as metals, as oxides (SiO2, Al2O3, Cr2O3) they are stable compounds where the production of hydrogen chloride takes precedence. Therefore, these elements are suitable as refractory components for high-temperature carbonization furnaces.

[0073] Next, we will use Figure 6 to explain in detail how to determine the appropriate amount of chlorine when coal and RDF are mixed and charged into a high-temperature carbonization furnace. The horizontal axis of the figure shows the mixing ratio X of the two types of charging materials; for example, X = 0 is 100% coal, and X = 1 is 100% RDF. The vertical axis shows the proportions (wt%) of N and Cl components in the charging materials, with N being scaled by multiplying it by the conversion ratio to NH3, 1 / k. K depends on the type of fuel and must be confirmed for each fuel, but in the case of a mixture of coal and waste plastic, K = 3 as mentioned above. The N proportion (wt%) of the mixed fuel at the mixing ratio X is expressed as Y. N (X), Cl ratio (wt%) is Y Cl (X), it is expressed by the following equation, as shown by the dotted and solid lines in Figure 6. Y N (X)=(N1-N0)・X+N0 (9) Y Cl (X) = (Cl1 - Cl0) X + Cl0 (10) N 0 : N percentage in coal (wt%) N 1 : N ratio in RDF (wt%) Cl 0 : Cl ratio in coal (wt%) Cl 1 : Cl ratio in RDF (wt%)

[0074] The amount of Cl consumed to salify impurities in RDF and coal is expressed as Cl v (X), then the chlorine in the fuel mixture is Y Cl (X) becomes Y after the salification reaction. Cl (X)-Cl v (X). Y Cl (X)-Cl v When the mixing ratio is (X) < 0, the amount of chlorine is insufficient for the target substance, and Y Cl (X)-Cl v It is desirable that (X)≧0. Conversely, Y Cl (X)-Cl v If (X) ≧ 0, HCl is generated, so the condition that can be neutralized by NH3 in ammonia water [Y N (X)≧Y Cl (X)-Cl v(X)] must be satisfied.

[0075] In RDF 100% operation, Y Cl (1) - Clv(1) = Cl1 - Clv(1). Therefore, it can be seen that the RDF should have a Cl ratio that satisfies the following formula (Formula 11). N1 / k ≥ Cl1 - Clv(1) ≥ 0 ⇔ N1 / k + Clv(1) ≥ Cl1 ≥ Clv(1) (11) For example, the ash of the RDF in Figure 9 (Table 1) contains 60 wt% of SiO2 and Al2O3 (estimated by the inventors of this application from Non-Patent Document 1), and it is possible to volatilize (decalcify) the remaining 40 wt% by reduction and chlorination. A trial calculation based on the ash components reveals that Cl v (1) = 5.5 wt%. The Cl content in the current RDF is 1.2 wt%, and even at a mixing ratio of 1 (100% RDF), there is still a chlorine shortage for the chlorination reaction, so the chlorine concentration can be increased to 5.5% or more.

[0076] In the conventional dry distillation furnace, if chlorination reaction is not considered, Cl v (X) = 0 (Cl1 < 3), and X in Figure 6 v0 The mixing ratio of X is the RDF mixing limit. v0 = 0.37 (Cl1 = 1.2) is the limit point explained (X v0 · Cl1 = 0.44%). In this embodiment, by actively using chlorine to chlorinate and volatilize impurities, it is possible to increase the mixing ratio of chlorine-containing waste to 100% and further increase the chlorine concentration of the waste. Note that the chlorine concentration Cl1 in the waste and the amount of chlorine introduced from the waste Cl1·X vo However, even if it does not reach the above-mentioned level, if it is increased beyond the conventional normal standard or limit point, it is clear that the effect of the present invention can be enjoyed to a certain extent, and the chlorine concentration Cl1 (wt%_dry) in the waste charged into the high-temperature carbonization furnace and the waste charging ratio X vo (wt%_dry) is at least Cl1≧3% or Cl1·X vo ≧ 0.5%.

[0077] It is important to understand Clv(X), but it is possible to understand it before operation by analyzing Ash, and it can also be corrected during operation from the NH3 concentration in the ammonia water. N (X)=Y Cl From the characteristics of (X) - Clv(X), the amount of HCl generated can be adjusted by changing the mixing ratio, so by understanding the NH3 and NH4Cl concentrations in the ammonia water, it is possible to understand the margin for changing the mixing ratio before making any adjustments.

[0078] Now, let's reconsider the ash (SiO2, Al2O3) remaining in the char (char) produced from RDF in a high-temperature carbonization furnace. This embodiment reduces and volatilizes (demineralizes) 40% of the ash in the RDF shown in Figure 9 (Table 1), reducing the ash content from 11.5% to 6.9%. However, because the FC of the RDF is low at 14.7%, the ash-to-FC ratio is high (Ash / FC = 47%). As mentioned above, the tar yield of plant biomass is comparable to the char yield, so the ash ratio (wt%) of the total solid-liquid injected fuel can be considered to be about half the ash ratio (wt%) of the solid fuel alone. However, compared to the Ash / FC ratios of 12.5% ​​and 14% for coking coal and LV coal (Table 2 in Figure 10), further reduction of ash is desirable for blast furnace tuyere injection fuel.

[0079] Therefore, focusing on the feature of this embodiment in which "carbide (char) produced in a high-temperature carbonization furnace is finely pulverized (similar to PCI) and then injected into the blast furnace tuyere by COM transport," we have devised a method for further deashing by adding "demineralization equipment using a selective flocculation method using heavy oil, etc." between the fine pulverization equipment and the COM transport, i.e., a method for using at least a portion of the liquid fuel to deash the carbide (char), which is a solid fuel after fine pulverization.

[0080] Coal deashing methods can be broadly divided into flotation and selective flocculation, which exploit the difference in hydrophobicity between coal and ash, and heavy-liquid methods, which exploit the difference in specific gravity. To increase the deashing rate, it is important to finely pulverize the coal and separate the carbonaceous and inorganic components. However, with heavy-liquid and conventional flotation methods, the finer the coal is pulverized, the lower the deashing rate and carbonaceous recovery rate. In this respect, oil agglomeration and flocculation flotation, which use heavy oil, are advantageous and have already been developed as coal deashing technologies (Patent Document 3, Non-Patent Document 7). Another advantage of these deashing processes after pulverization is that they can remove water-soluble impurities that may remain in the charcoal as unreacted matter.

[0081] As shown in FIG. 1 , in this embodiment, the char product of the high-temperature carbonization furnace is pulverized to a fine powder for injection into the blast furnace. Therefore, the pretreatment (pulverization) required for the deashing process is already complete. Therefore, it is desirable to install a deashing unit 11 downstream of the pulverizer 7 depending on the ash content of the char (e.g., for a high-temperature carbonization furnace using RDF, the furnace battery should be dedicated to the discharge facility and beyond). As a flocculant (binder), a low-volatility oil is desirable, and heavy oil or tar generated in the coke oven 3 or high-temperature carbonization furnace 2 is desirable. When heavy oil or tar is used as a flocculant, its viscosity should be maintained at 40 to 60°C. However, as shown in FIG. 5 , the related equipment (high-temperature carbonization furnace 2, COM 12, and blast furnace 1) is preferably installed adjacent to the blast furnace. The sensible heat of the deashing unit 11 is transferred to the COM fuel, which is ultimately injected into the blast furnace as sensible heat for injection into the tuyere, resulting in no energy waste.

[0082] In Figure 1, the flow is such that all of the coke breeze is charged into the high-temperature carbonization furnace. This allows alkalis (Na, K) remaining in the coke breeze and interfering with the operation of the sinter machine or blast furnace to be removed (reduced and volatilized by chlorination) in the high-temperature carbonization furnace, and the coke breeze can be used as a carbon source to promote the reduction and chlorination reaction of equation (6).

[0083] As an example, we calculated the amount of carbon consumed (∝CO2 emissions) in the ironmaking area (blast furnaces, coke ovens, sintering machines) using the carbonaceous materials in Figure 9 (Table 1) and assuming 100% sintered ore. Coking coal is coal with adjusted caking properties and coal rank used in coke production, while LV coal and HV coal are general coal with no (or low) caking properties and are used in high-temperature carbonization furnaces.

[0084] Although high-temperature carbonization furnaces are facilities that carbonize coal and other materials at temperatures of up to 900°C or higher, calculations were made for facilities (including gas purification equipment) that carbonize at temperatures equivalent to those of conventional coke ovens for the purpose of this example. It is also assumed that all COG generated from coke ovens and high-temperature carbonization furnaces is used as a reducing agent (blast furnace reducing gas), and that blast furnace top gas or external fuel (CH4) is used as combustion fuel for carbonization heat, hot stoves, and sintering machines (ignition furnaces, denitrification equipment), which are used for heat purposes.

[0085] First, Table 3 in Figure 11 shows a comparison of the estimated carbon (C) consumption results for a case in which LV coal is used in Figure 2 (Patent Document 1), where this embodiment is not applied, and a case in which LV coal or HV coal is used in Figure 3, where this embodiment is applied to a blast furnace tuyere injection line. Note that the numbers in the table are rounded off to the nearest digit, and the totals of the numbers do not necessarily match (the same applies to other tables).

[0086] Comparing the cases of "Fig. 2 x LV coal" and "Fig. 3 x LV coal," which use the same LV coals, in "Fig. 3 x LV coal," to which this embodiment is applied, C consumption in the blast furnace improves by approximately 18 kg / tp, and although C consumption in the high-temperature carbonization furnace increases by approximately 9 kg / tp, C consumption in the ironmaking area as a whole can be reduced by approximately 9 kg / tp.

[0087] In Figure 3, even when LV coal is changed to HV coal, the increase in carbon consumption is limited to a total of 3 kg / tp, reducing the impact of the change in coal type, and improving by 5 kg / tp compared to "Figure 2 × LV coal" where this embodiment is not applied. Although not shown in the table, in the case of "Figure 2 × HV coal" where this embodiment is not applied, the coal consumption unit × oxygen consumption unit is 582 kg / tp × 368 Nm 3 / tp, which makes operation difficult, so HV coal cannot be used. However, in the "Figure 3 x HV coal" case, the basic unit is 228 kg / tp x 137 Nm3 This reduces carbon consumption (CO2 emissions) to a lower level than in the example using LV coal (Patent Document 1) to which this embodiment is not applied. In other words, it is clear that the options for carbonaceous materials can be expanded.

[0088] The bottom row of Figure 11 (Table 3) shows the carbon reduction achieved when CH4 is converted into H2 energy. Since the carbon consumption of the conventional hot air-based blast furnace process is approximately 630 kg / tp (equivalent to 2.3 t / tp of CO2), if green hydrogen can be used instead of CH4, CO2 emissions can be halved without considering CO2 reuse or underground storage.

[0089] Next, in FIG. 4, this embodiment is also applied to the sintering machine's coagulant, and the case where LV coal or HV coal is used is shown in Table 4 of FIG.

[0090] In the "Figure 4 x LV coal" case, carbon consumption worsens (increases) by 7 kg / tp compared to "Figure 3 x LV coal," and in "Figure 4 x HV coal" carbon consumption worsens by 10 kg / tp compared to "Figure 3 x HV coal," but this is mainly due to increased carbon consumption in the high-temperature carbonization furnace due to increased production of agglomerate. Also, "Figure 4 x HV coal" has carbon consumption 8 kg / tp lower than "Figure 2 x LV coal," meaning it can contribute to reducing CO2 emissions regardless of coal type.

[0091] Furthermore, converting HV coal to biomass fuels (including torrefied fuel) would eliminate carbon emissions from HV coal. If all HV coal were converted, carbon emissions would be reduced by 248 kg / tp, reducing total carbon emissions from 381 kg / tp to 133 kg / tp (less than one-quarter of the emissions from conventional blast furnace processes). Converting CH4 to green H2 would reduce carbon emissions by an additional 57 kg / tp, reducing total carbon emissions to 76 kg / tp (approximately one-eighth of the emissions from conventional blast furnace processes). Of the 76 kg / tp, 45 kg / tp is carbon in the molten iron. This carbon can be recovered as CO2 gas in the converter downstream, which can then be used as reducing gas for the blast furnace. This means total carbon emissions could be reduced to approximately 30 kg / tp (approximately one-twentieth of the emissions from conventional blast furnace processes).

[0092] As described above, this embodiment allows for the use of waste materials other than pure biomass fuel as a coal alternative fuel. Although the coal emission factor of refuse-derived fuel is not zero, it has the same CO2 reduction effect as biomass fuel in that it can reduce CO2 emissions derived from the substituted fossil fuel (coal).

[0093] Table 5 in Figure 13 shows a case where LV coal or HV coal is used in Figure 1 (where the transportation of pulverized char is changed from pneumatic transport in Figure 4 to COM transport), which is a model case of this embodiment.

[0094] The total C consumption for LV coal is unchanged from Table 4 in Figure 12, but for HV coal it is worse than in Table 4. However, when coal or heavy oil is replaced with biomass fuel, it can be seen that the improvement effect is greater than that of biomass fuel in Table 4 in both cases.

[0095] The amount of heavy oil used for COM is determined by the solid fuel to liquid fuel ratio, with a 1:1 ratio eliminating the need for heavy oil. As mentioned above, biomass fuels and waste plastics often have a higher liquid fuel yield than solid fuel yield. Therefore, increasing their blend ratio (reducing the coal ratio) eventually eliminates the need for heavy oil. At a zero coal blend ratio, the solid fuel concentration in COM is less than 50 wt%. This means that fossil fuels, such as coal and heavy oil, are no longer needed, reducing apparent CO2 emissions to 114 kg / tp (less than one-fifth of that achieved with conventional blast furnace processes). Biomass fuels and waste plastics also have a higher COG yield than hybrid coal. Therefore, increasing the coal blend ratio allows for the replacement of externally sourced CH4 with increased COG. This allows for total carbon emissions of 76 kg / tp to be achieved without the need for green H2 or carbon recycling / CO2 storage. This value is approximately one-tenth of the total carbon emissions achieved with conventional blast furnace processes. In this regard, the fact that 200 million tons of waste are incinerated in Japan per year (estimated by the inventors of the present application) is an advantage from the perspective of the availability of coal alternative fuels (urban circulative resources generated every year). By chemically recycling waste that meets the quality and economical requirements of this embodiment as a coal alternative fuel, it is possible to reduce CO2 emissions from the steel manufacturing industry and waste.

[0096] In the embodiments and examples described so far, a method has been described in which carbide (char) produced in a high-temperature carbonization furnace is utilized in a blast furnace process, in which part or all of the char is coarsely crushed in a coarse crusher to obtain coarse char, which is used as a coagulant for sintered ore, and the undersize powder resulting from the coarse crushing process or the fine char that has been subjected to the fine crushing process is injected from the lower furnace tuyeres. However, as a means for supplying carbide into a blast furnace, in addition to the method of injecting it from the lower furnace tuyeres after fine crushing, there is also a method in which part or all of the char after coarse crushing is charged from the furnace top together with coke and ore, as shown in Figure 7.

[0097] The char charged from the top is preheated to the lower furnace boundary temperature (e.g., 1300°C) as it descends to the lower furnace. This (1) improves the efficiency of char combustion heat transfer to the lower furnace, and (2) reduces the heat required to heat the ash (mainly SiO2) in the char, which is discharged as slag at approximately 1500°C, by approximately one-fifth, thereby further reducing the fuel ratio. In other words, because top charging of char has a thermal effect equivalent to reducing the ash ratio by one-fifth, even char (high ash ratio) produced from raw materials with a high ash ratio relative to FC (fixed carbon), such as RDF, can be used without deashing. In principle, the preheating effect of ash in char can also be expected to have a similar effect when used as a coagulant for sintered ore charged from the top.

[0098] The char charged from the top of the furnace contains almost no volatile matter if it has been subjected to high-temperature carbonization in advance, and even if gas is generated from the char by preheating to over 900°C, it contains almost no tar or hydrocarbons.Even if hydrocarbons are present, they are reformed with H2O or CO2, so it can be treated as normal furnace gas (CO, H2, CO2, H2O, N2) without interfering with operation.

[0099] Charging char from the top of the furnace is not only more thermally efficient than injecting it directly into the bottom of the furnace, but also has the function of preserving coke quality by self-sacrificially gasifying before the coke undergoes the gasification reaction (C + CO2 = 2CO, H2O + C = H2 + CO). The particle reaction rate (kg / s) is proportional to the specific surface area (m 2 / kg), so it is desirable for the particle size to be small enough to prevent scattering. If the average particle size of the coke in the lower part of the furnace is about 30 to 35 mm, a particle size of 10 mm or less is desirable to have a specific surface area 10 times larger (∝ combustion rate), and a particle size of 3 mm or more is desirable to prevent it from being blown away by a small amount of blow-by gas. In other words, it is desirable for the particle size of the char charged to the top to be mainly between 3 mm and 10 mm (i.e., 70% or more).

[0100] Since classification devices such as screens have classification efficiencies, char smaller than the sieve openings can also be charged to the top of the furnace. The char discharged outside the furnace along with the top gas can be collected in a primary or secondary dust collector, pulverized, and then blown into the tuyeres at the bottom of the furnace. However, since the char contains iron-based dust and auxiliary material dust in addition to carbonaceous materials, it can be effectively utilized by using it as a sintered ore raw material (agglomeration agent), as has been done in the past.

[0101] By increasing the amount of char charged to the top, the fuel burned in the lower part of the furnace will shift from being mainly tuyere-injected fuel (pulverized char and tar, etc.) to also being top-charged char. Combustion using tuyere-injected fuel tends to produce higher combustion heat on the furnace wall side than at the center, as in conventional blast furnaces. However, since top-charged char can be distributed evenly in the radial direction, combustion tends to occur evenly in the radial direction, and the heat at the center of the furnace where combustion ends can be increased. In other words, by adjusting the proportion of char charged to the top, the heat distribution in the lower part of the furnace can be adjusted.

[0102] In addition to the methods mentioned above, another method for adjusting the heat distribution in the lower part of the furnace is to mix larger particles with the fine char to extend the char combustion time. In Figure 7, a line has been installed to bypass the crusher and mix the under-screened powder (fine char) with the fine char to adjust the fine char combustion time. However, for char with a high ash content, it is desirable to finely crush it and deash it before converting it into COM. Because the amount of fine char injected is reduced by charging char from the top, it is possible to use only tar derived from coal or coal substitute fuels to cover the oil required for COM transportation (i.e., external fuels such as heavy oil are not required).

[0103] On the other hand, the disadvantages of top-charging char include an increase in the amount of slag and auxiliary materials (a source of raw material-derived CO2) compared to tuyere injection with deashing when using char with a high ash content, and a longer time for the char to reach the bottom of the furnace, resulting in reduced responsiveness to changes in conditions in the bottom of the furnace. Therefore, it is desirable to appropriately adjust the ratio of top-charging to bottom-furnace injection, taking into account the ash content in the char, the rate of liquid fuel generation such as tar, and the rate of undersize char due to coarse char crushing, as well as the radial heat distribution below the furnace, as mentioned above. The advantage of combining top-charging and bottom-furnace injection is that it allows for operational adjustments based on the raw material and furnace conditions.

[0104] From the above, it can be seen that the method of coarsely crushing part or all of the solid fuel, carbide (char) produced in a high-temperature carbonization furnace, in a coarse crusher, and using the solid fuel as a sintered ore agglomeration material or a blast furnace top charge material, or both, and finely crushing part or all of the solid fuel so that the proportion of particles having a particle size of 0.1 mm or less is 70% or more, and then injecting the finely crushed part or all of the solid fuel from the blast furnace tuyere at the bottom of the furnace, is a distinctive and effective operating method in the blast furnace ironmaking process.

[0105] Table 6 in Figure 14 compares carbon consumption between Case 1 (fine char injection into the lower furnace only; no deashing) and Case 7 (coarse char injection from the top) when using the HV coal listed in Table 2 in Figure 10. The "Figure 7 × HV coal" case illustrates a case in which the ratio of coarse char injected from the top to fine char injected from the bottom of the furnace is determined so that external fuel (heavy oil) is not required for the COM injected into the lower furnace. In the "Figure 7 × HV coal" case, the ratio is 77%:23%. However, this ratio varies depending on the FC (fixed carbon) and VM (volatile matter) ratios of the coal (or coal substitute fuel), including coking coal, the gangue content of the ore, the operating conditions of the coke oven and high-temperature carbonization furnace, and other factors.

[0106] In the "Figure 7 x HV Coal" case in Table 6 of Figure 14, total carbon consumption was lower than in any other example (case) due to the reduction in high-carbon emission factor fuels such as coal and heavy oil. Therefore, at least when using coal without deashing, as shown in Table 2 of Figure 10, it is preferable to charge char to the top of the furnace whenever possible, and it can also be used as a coagulant for sintered ore. Furthermore, the total char consumption of coarse and fine powder in this case (173 kg / tp) was the lowest compared to the other cases in Figures 1, 4, and 5, and CH4 consumption was the highest compared to the other cases. Therefore, this is the most suitable method for using biomass-based fuels (including waste-based fuels) with low carbon yields and high COG yields as an alternative fuel.

[0107] Existing steelworks often have two or more blast furnaces (multiple furnaces). In this case, as a method for reducing CO2 derived from CH4 described in Tables 3 (Fig. 11) to 6 (Fig. 14), one or more of the multiple blast furnaces can be converted to the method of the present invention, and the surplus energy (including converter gas) from the remaining conventional blast furnace can be used instead of CH4. This will lead to a CO2 reduction effect for the steelworks as a whole by increasing the production volume achieved by the method of the present invention.

[0108] For example, in the "Figure 7 x HV coal" case in Figure 4 (Table 6), the carbon consumption per ton of hot metal is 362 kg / tp, but by using surplus gas from the adjacent blast furnace, the carbon consumption derived from CH4 is reduced to 68 kg / tp (= 128 Nm 3 This will eliminate the need for CH4 / tp (4.6 GJ / tp), and carbon consumption will be 294 kg / tp (equivalent to 1.08 tCO2 / tp in CO2 emissions). This means that most of the coking coal can be changed to hybrid coal, and blast furnace CO2 emissions can be halved from the current level of approximately 2.2 tCO2 / tp to 1.08 tCO2 / tp without the use of expensive external fuels. The surplus energy from the conventional blast furnace method, including tar, is 7.4 GJ / tp (estimated by the inventors), and this balances out at 0.62 tp of conventional blast furnace production per 1 tp of "Figure 7 x HV coal" production (= 4.6 / 7.4).

[0109] Although the present invention has been described with reference to a blast furnace, its principles and effects can also be applied to other metallurgical furnaces. Some examples of this are given below.

[0110] For example, as a CO2 reduction measure in the steel industry, a new method has been developed in Europe and Japan to replace the conventional blast furnace process: producing direct-reduced iron (DRI) in a hydrogen-based direct reduction furnace, then melting and carburizing the DRI in an electric melting furnace to produce molten pig iron (hot metal). Direct reduction furnaces (metallurgical furnaces) require green hydrogen instead of conventional natural gas, and electric melting furnaces (metallurgical furnaces) require carburizing materials such as coke, posing challenges in energy efficiency and CO2 reduction. However, this invention utilizes idle coke ovens, which have been shut down due to the shutdown of existing blast furnaces, as high-temperature carbonization furnaces. By pre-treating near-carbon-neutral waste, carbon-neutral gaseous fuel (COG) can be supplied as a hydrogen-based reducing agent, and high-quality carbon-neutral solid fuel (char) can be supplied as a carbon-neutral replacement for coke. Liquid fuel can also be used as heating fuel for the gas reformer for the direct reduction furnace.

[0111] The carburizing material must penetrate the slag layer, which has a higher specific gravity than the carbon material, and penetrate into the molten iron. Therefore, high-temperature carbonization is important to minimize the VM (volatile matter) that generates gas. Furthermore, since the carburizing rate is inversely proportional to the particle size, it is also effective to crush the material into fine particles before injecting it.

[0112] As a measure to reduce CO2 emissions in the steel industry, the conventional method of melting scrap and DRI in an electric arc furnace (EAF) to produce molten steel is being promoted instead of using a blast furnace. However, because electricity costs have a significant impact on the economic viability of an EAF (metallurgical furnace), countries with high electricity rates, such as Japan, have traditionally used fossil fuels (such as carbon, natural gas, and heavy oil) as slag foaming materials and fuel for scrap melting burners to reduce electricity consumption. Furthermore, to combat dioxins in electric furnace exhaust gases, burners are required to decompose dioxins at high temperatures, and fuel consumption is actually increasing despite the reduction in electricity consumption. However, according to this invention, coke ovens that become idle due to the shutdown of existing blast furnaces can be utilized as high-temperature carbonization furnaces, allowing for the production of high-quality slag foaming materials and metallurgical fuels in CN.

[0113] It can also be used for pre-treatment of raw materials in other metallurgical furnaces such as cupolas (especially cokeless cupolas), smelting reduction furnaces, non-ferrous smelting furnaces, lime kilns, etc.

[0114] The direct reduction furnace and electric melting furnace exemplified above also exist as stand-alone metallurgical furnaces, and the present invention can be applied to each of them. Furthermore, although the use of an existing coke oven has been exemplified as a high-temperature carbonization furnace from the viewpoint of utilizing existing facilities, the present invention is not limited to this, and a high-temperature carbonization furnace of a different type from a coke oven may also be installed in a steelworks that does not have a coke oven.

[0115] The technology of the present invention also relates to reducing CO2 from waste.

Claims

1. A coal or coal substitute solid fuel that is non-coking or has coking properties that prevent it from becoming blast furnace coke is charged into a high-temperature carbonization furnace as a raw material for char, and the high-temperature carbonization treatment is performed using the high-temperature carbonization furnace under conditions that the maximum carbonization temperature is 900°C or higher. The combustible material produced by the high-temperature carbonization process is separated into solid fuel, liquid fuel, and gaseous fuel as char, A method for pre-treating raw materials, comprising injecting part or all of the solid fuel, liquid fuel, or gaseous fuel into a metallurgical furnace.

2. A portion or all of the solid fuel is subjected to coarse grinding or fine grinding, and the sieved powder generated in the coarse grinding process or the solid fuel that has undergone the fine grinding process is blown into the metallurgical furnace. The method for pre-treating raw materials according to claim 1.

3. CO and H from part or all of the aforementioned gaseous fuel 2 The main synthesis gas is produced and blown into the metallurgical furnace at a temperature of 800°C or higher. The method for pre-treating raw materials according to claim 1.

4. A portion or all of the aforementioned liquid fuel is injected into the lower part of the metallurgical furnace. The method for pre-treating raw materials according to claim 1.

5. The finely ground solid fuel and the liquid fuel are mixed in advance and blown into the lower part of the metallurgical furnace. The method for pre-treating raw materials according to claim 4.

6. A portion or all of the aforementioned solid fuel is crushed to obtain solid fuel with a particle size of 1 mm or more and 10 mm or less, which is used as a binder or furnace top charge material for sintered ore, or both the binder and the furnace top charge material. A portion or all of the solid fuel, which has been finely ground so that the proportion of particles with a particle size of 0.1 mm or less is 70% or more, is blown in from the tuyeres of the metallurgical furnace. A method for pre-treating raw materials according to any one of claims 1 to 5.

7. Using waste as a coal substitute fuel, the chlorine concentration in the waste charged into the high-temperature carbonization furnace is Cl 1 (wt%_dry) and waste charge ratio X vo (wt%_dry) is at least Cl 1 ≥3% or Cl 1 ・X vo Any of the following applies: ≥0.5% A method for pre-treating raw materials according to any one of claims 1 to 5.

8. To deash the solid fuel after it has been finely ground, use at least some of the liquid fuel. The method for pre-treating raw materials according to claim 7.

9. The method for pre-treating raw materials according to claim 7, wherein some or all of the waste to be charged into the high-temperature carbonization furnace is pre-molded before being placed inside the furnace.