Method for pretreating feed material

Abstract

A method for preprocessing raw materials includes: performing dry-distilling of coals or coal-alternative solid fuels outside the blast furnace coke production range under a condition where the maximum dry distillation temperature becomes 900°C or higher; separating combustibles produced by the dry distillation into solid fuel, liquid fuel, and gaseous fuel; and injecting all or part of the solid fuel, the liquid fuel, or the gaseous fuel into a metallurgical furnace.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for preprocessing raw materials for blast furnace processes including sintering machines and dry distillation furnaces. In particular, it relates to the preprocessing and handling of raw materials for the blast furnace process, and relates to the expanding raw material options and CO 2 reduction.BACKGROUND ART

[0002] In a blast furnace process, coke and iron ore are charged from the furnace top, and hot blast, which is high-temperature air of 1000°C or higher, and pulverized coal or the like as a reducing agent are injected from tuyeres provided in a lower furnace. Accordingly, the pulverized coal and coke are combusted to generate high-temperature reducing gas such as CO and H 2 together with a large amount of heat, which rises in the furnace and heats up and reduces the iron ore descending in the furnace.

[0003] In addition to having low ash content and low sulfur content, BF coke is required to have appropriate porosity and a strength that does not cause pulverization even at high temperatures. For producing coke satisfying such conditions, only limited kinds of bituminous coal are used and are called coke-oven feed coal (application classification name), and they are distinguished from steam coal mainly used as fuel for power generation.

[0004] In a coke oven, the coke-oven feed coal that has been crushed and mixed is charged into a carbonization chamber and indirectly heated at 1,000 to 1,300°C for 14 to 20 hours to be dry distilled, thereby producing coke. At this time, fuel gas (COG), and tar and the likes are obtained as by-products.CITATION LISTPATENT LITERATURE

[0005] Patent Literature 1: International Publication No. 2023 / 190840 Patent Literature 2: Japanese Patent Application Laid-open Publication No. 2000-104075 Patent Literature 3: Japanese Patent Application Laid-open Publication No. Sho 58-160395 NON-PATENT LITERATURE

[0006] Non-Patent Literature 1: Katsuhiko Yamamoto, Shinichi Misawa, Kazuhiko Hizuka, and Ryouhei Mimura, "Experimental study on developing uses of RDF by carbonization", Journal of the Japan Society of Waste Management Experts, The Japan Society of Waste Management Experts, 2000, Vol. 11, No. 4.

[0007] Non-Patent Literature 2: Uwe Essmann, "Biochar-pellets as substitute for fossil coal in metallurgical processes," Master's thesis, Renewable Energy ENE500, University of Agder, 2018.

[0008] Non-Patent Literature 3: The Japan Institute of Energy (ed.), "Biomass Handbook (2nd edition)," The Japan Institute of Energy, 2009.

[0009] Non-Patent Literature 4: Nippon Steel Corporation (then Shin Nippon Seitetsu Kabushiki Kaisha), "Recycling technology of municipal waste plastics by coke-oven chemical feedstock process," The 58th Okochi Memorial Production Prize, Okochi Memorial Foundation, 2011.

[0010] Non-Patent Literature 5: Tatsuya Oki, Junichi Tanaka, and Taneomi Harada, "Factors affecting grindability of coal," Shigen-to-Sozai (Resources and Materials), The Mining and Materials Processing Institute of Japan, 1996, Vol. 112, No. 1, pp. 37-42.

[0011] Non-Patent Literature 6: Takuya Furuzono, Akihiro Hoshino, Tsuyoshi Teramae, Ikuo Hosoya, and Toru Yamashita, "Fundamental study on pulverization characteristics of semi-carbonized pellets," Proceedings of the 54th Coal Science Conference of The Japan Institute of Energy, 2017.

[0012] Non-Patent Literature 7: Kazuhiko Nakaoji, Yoichi Nakamura, and Katsumi Muroi, "Deashing technology of coal by oil agglomeration and its application," Hitachi Review, Hitachi Review, 1984, Vol. 66, No. 2.SUMMARY OF THE INVENTION

[0013] In a blast furnace, which is a metallurgical furnace, pulverized coal (PC) injected from tuyeres is subject to fewer restrictions than coke-oven feed coal, but coal quality is limited. Therefore, coal or coal-alternative solid fuel (Tuyere-injection solid fuel) to be injected from the tuyeres is not injected directly from the tuyeres. But it is characterized to be separated into solid, liquid and gas in a high-temperature dry distillation furnace such as a coke oven. Then, the solid fraction (char) is injected from blast furnace tuyeres, the gaseous fraction (COG) is reformed into a high-temperature reducing gas to be blown into the blast furnace, and a combustible fraction (tar and the likes) among the liquid is injected from blast furnace tuyeres. By this, "reduction in decomposition heat of tuyere-injection solid fuel → increase in effective calorific value of the same fuel → reduction in tuyere-injection solid fuel → reduction in fuel ratio of the blast furnace and combustion-supporting gas (oxygen)" is achieved, and CO 2 emissions can be reduced.

[0014] By the above method, as coal-alternative solid fuels, renewable fuels having very high VM (volatile matter), such as bio-pellets and biochar, and waste-derived solid 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 agents). Here, heavy metals, alkalis and other impurities in wastes are chloride-volatilized in the high-temperature dry distillation furnace by chlorine in the wastes and thus removed from the char, so that there is no hindrance to blast furnace operation as a metallurgical furnace.

[0015] By using renewable fuel and refuse-derived solid fuel, fossil fuel (coal) can be reduced, and therefore costs and energy for CO 2 treatment associated with the reduced amount of fossil fuel (coal) or with the alternative fuel become unnecessary.TECHNICAL PROBLEM

[0016] In the steel industry, since fossil fuels such as coal and natural gas are used as reducing agents and combustion fuels in metallurgical furnaces -blast furnaces, large amounts of CO 2 are emitted and countermeasures for their reduction are expected. For underground storage of CO 2 , stable ground and acquiring local consensus are issues. And economic hurdles including the infrastructure are high for CO 2 reuse (C-recycling) and / or H 2 reduction because large amounts of H 2 and green power are required. The inventor of the present application has devised, as Patent Literature 1, a CO 2 reduction measure for blast furnaces that has not been available before, but even then, there is further room for reduction in the amount of CO 2 emissions when C-recycling and / or underground storage are not taken into account. Also, according to this invention, the coke rate (CR) can be reduced to 1 / 5 or less of that in the conventional method. But when coke is reduced, coke breeze, which is a by-product of coke, is also reduced similarly. Since coke breeze is used as a sintering fuel for a sintering machine, it is necessary to compensate for a shortage of coke breeze with anthracite. But there used to be a concern that the VM (volatile matter) in anthracite cannot be well utilized as heat source, but generates tar to bring about various problems.

[0017] Further, according to Patent Literature 1, as blast furnace tuyere injection fuels, it is preferable that materials have higher primary combustion heat (reaction of C + 0.5 × O 2 = CO) and have smaller thermal decomposition heat (amount of heat to decompose according to C i H j O k = i × C + 0.5 j × H 2 + 0.5 k × O 2 ) required before combustion, and it is desirable that VM be small. At PCI (pulverized coal injection) facilities in conventional blast furnace, LV coal (low-VM coal) has recently tended to be used for that reason. Also, tuyere injection of biochar is being studied worldwide as a CO 2 reduction countermeasure, because the VM of biofuel is very high. And the idea is to carbonize it (dry distillation at 400-700°C) at a collection site in order to inject into the furnace the ones whose VM are reduced- with calorific value increased - as that of anthracite to MV coal (medium-VM coal). However, when biomass is subjected to carbonization, the yield of carbonized material (char) is about 20%, and gas, tar and the likes are hardly effectively utilized except for heat required for the carbonization, which leads to a problem that energy efficiency is low.

[0018] On the other hand, greenhouse gas emissions associated with waste incineration in Japan amount to about 40 million tons, accounting for 3% of Japan's total emissions and corresponding to about 40% of emissions from the steel industry.

[0019] With respect to municipal-solid-waste incineration plants, there are an increasing number of cases in which power generation facilities are installed in order to make effective use of waste heat. However, issues of incineration residues caused by chlorine, alkalis, heavy metals and the like in wastes remain. And the power generation efficiency is as low as about 15% on a national average due to the corrosion problems of boiler walls. The energy efficiency including self-consumption of electricity in the plant is even lower. Furthermore, from the viewpoint of reducing CO 2 emissions, power generation within incinerators or with RDF / RPF / etc. does not reduce CO 2 emissions but only provides a possibility to reduce fossil fuels in thermal power plants by the amount corresponding to the increase in generated power, which is a thermal recycling. Biomass power generation or renewable fuel power generation also falls within the category of thermal recycling. And it is important to rationally realize material recycling and / or chemical recycling in order to get substantial CO 2 reduction.TECHNICAL SOLUTION

[0020] In the raw material preprocessing method according to the present invention, coals and / or coal-alternative solid fuels outside the range for coke production are subjected to dry distillation under conditions in which the maximum dry distillation temperature becomes 900°C or higher. And combustibles generated through the dry distillation are separated into solid fuel, liquid fuel and / or gaseous fuel. Then, all or part of the solid fuel, liquid fuel or gaseous fuel is blown into metallurgical furnaces including blast furnaces.EFFECT OF THE INVENTION

[0021] By the above raw material preprocessing method, coals and / or coal-alternative fuels (hereinafter collectively referred to as "Coals"), which are tuyere-injection solid fuels, can be changed to char (C + ash) having almost no volatile matter (VM) within a high-temperature dry distillation furnace in which the maximum temperature becomes 900°Cor higher. Whereby, the decomposition heat of tuyere-injection solid fuel is eliminated and the heating value becomes higher, compared with directly injecting Coals from blast furnace tuyeres. Therefore, to produce 1 t of pig iron, it can reduce a tuyere-injection solid fuel rate (kg / tp) and an oxygen rate (Nm 3< / tp) as combustion-supporting gas. Moreover, this makes it possible to use high-VM fuels such as HV coals, biomass solid fuels and / or waste-derived solid fuels as reducing agents for blast furnaces. Here, heavy metals, alkalis and other impurities in wastes are chloride-volatilized in the high-temperature dry distillation furnace by chlorine in the wastes and thus removed from the char, so that there is no hindrance to blast furnace operation.

[0022] Compared to directly injecting coals into blast furnaces, the above raw material preprocessing method increases the amount of gas (hereinafter referred to as COG; coke oven gas) generated in the coke oven and / or high-temperature dry distillation furnace (hereinafter also referred to as "High-temperature dry distillation furnaces"). COG mainly contains hydrogen but also components such as CH 4 and CO 2 . Converting it into H 2 and / or CO, heating it, and then blowing it into the blast furnace promotes gas-based ore reduction and enables the reduction of other fuels.

[0023] Compared to directly injecting coals into blast furnaces, the above raw material preprocessing method increases the amount of combustible liquid (meaning tar, crude light oil and the likes; hereinafter collectively referred to as "Tar") generated in High-temperature dry distillation furnaces. Although Tar can be used as combustion fuel for ironmaking facilities (hot stoves, coke ovens and sintering machines), it is preferable to use Tar as tuyere-injection reducing agent. Furthermore, the best way is to utilize it as oil for COM (Coal Oil Mixture) - a means to transport and inject BF-tuyere-injection solid fuel-, where Tar serves both as a transport medium and as tuyere-injection fuel.

[0024] The char produced by the above raw material preprocessing method can also be used as a sintering fuel for sintering machines, which can solve problems when anthracite is used as the sintering fuel. In addition, producing char as a sintering fuel increases the amounts of COG and Tar produced as by-products in high-temperature dry distillation furnaces. They can be used as reducing agents for blast furnaces so that the fuel rate (reducing agent rate) of the blast furnace can be reduced and Tar can be used as the oil when COM is used.

[0025] Thus, regardless of whether coals have caking property or not, by preprocessing coals in high-temperature dry distillation furnaces to pyrolyze them and to take out fuels in three phases-solid, liquid and gas- and by using these fuels appropriately according to each phase, it is possible to reduce the amount of fossil fuels used in ironmaking facilities as a whole including blast furnaces, sintering machines and coke ovens.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] [FIG. 1] FIG. 1 is an overall flow diagram according to an embodiment of the present invention, in which char is supplied to a blast furnace from tuyeres at the lower furnace. [FIG. 2] FIG. 2 is an overall flow diagram of reducing agents and sintering fuels before application of the present embodiment. [FIG. 3] FIG. 3 is a flow diagram in which the present embodiment is applied only to a blast-furnace tuyere-injection line in FIG. 2. [FIG. 4] FIG. 4 is a flow diagram in which, in addition to FIG. 3, the present embodiment is also applied to a sintering fuel for sintering machines. [FIG. 5] FIG. 5 is a diagram comparing a conventional PCI method with a carbonaceous-material preprocessing flow according to the present embodiment. [FIG. 6] FIG. 6 is a nitrogen / chlorine balance diagram according to a mixing ratio of coals and chlorine-containing fuels. [FIG. 7] FIG. 7 is an overall flow diagram according to an embodiment of the present invention, in which char is supplied to a blast furnace from both a furnace top and tuyeres at the lower furnace. [FIG. 8] FIG. 8 shows an unreacted-core model in a case where waste containing chlorine is formed into spherical briquettes. [FIG. 9] FIG. 9 is Table 1 showing components of the RDF in Non-Patent Literature 1. [FIG. 10] FIG. 10 is Table 2 showing proximate analysis values, ultimate analysis values and LCVs of coke-oven feed coals, LV coal and HV coal, respectively. [FIG. 11] FIG. 11 is Table 3 showing a comparison of estimated carbon intensity between a case using LV coal in FIG. 2 and cases using LV coal or HV coal in FIG. 3 in which the present embodiment is applied to a blast-furnace tuyere-injection line. [FIG. 12] FIG. 12 is Table 4 showing cases using LV coal or HV coal in FIG. 4 in which the present embodiment is also applied to a sintering fuel for a sintering machine. [FIG. 13] FIG. 13 is Table 5 showing cases using LV coal or HV coal in FIG. 1 which is a model case of the present embodiment. [FIG. 14] FIG. 14 is Table 6 showing a comparison of carbon intensity between the case of FIG. 1 and the case of FIG. 7 where HV coal in Table 2 (FIG. 10) is used. DESCRIPTION OF EMBODIMENTS

[0027] Several exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. It should be noted that the drawings illustrate representative facilities related to the present embodiment, but do not show detailed information including auxiliary equipment and combustion fuels.

[0028] Although each term is used in the following description and the appended claims in a sense consistent with definitions well known to those skilled in the art, we caution that certain terms have the following meanings. "The lower furnace" means the area of and below the cohesive zone, including a region in which permeability deteriorates due to softening of the ore (at temperatures of 1200-1300°C or higher, depending on the reduction degree of the ore). "Partial combustion" means combustion that is not a complete combustion. "Primary combustion" refers to the reaction of C + 0.5·O 2 = CO, as well as the partial combustion that produces CO, H 2 and H 2 S from coke and / or tuyere injection fuels. The heat generated by this is called "primary combustion heat." "Fuel rate" or "reducing agent rate" means a total weight (kg / tp) of coke and tuyere-injection fuels (also referred to as tuyere-injection reducing agents) required to produce 1 t of pig iron. These terms are in principle synonymous, but "reducing agent rate" is often used in order to distinguish from combustion fuels and which term is used depends on the context. In the present description, unless otherwise specified, the fuel rate does not include a reducing gas (CO, H 2 ) blown in from tuyeres by means of top-gas recycling or the like. "Low-temperature dry distillation," "medium-temperature dry distillation" and "high-temperature dry distillation" are expressions that classify relatively slow pyrolysis methods in accordance with pyrolysis temperature. Although detailed definitions thereof are not established even among those skilled in the art, in the present description low-temperature dry distillation is taken as a temperature range for semi-carbonization (torrefaction), medium-temperature dry distillation as a temperature range for producing typical biochar (VM = about 5-25%), and high-temperature dry distillation as a temperature range for producing coke or biocoke (residual VM of a few percent), namely 200-300°C, 400-700°C and 900-1300°C, respectively.

[0029] A pulverized coal injection (PCI) for a blast furnace is a method to inject pulverized coals into the blast furnace from tuyeres. It aims to substitute inexpensive non-coking coals for expensive and precious coke (referring to lump coke charged from the blast furnace top), and utilizes the pulverized coals (VM = 10-40%) in order to increase combustion efficiency. Therefore, even if there may be some rationale for pulverizing anthracite or coke breeze (yield loss of lump coke) for use in PCI under special circumstances, there is apparently no rationale for pulverizing lump coke (the main product of a coke oven) and injecting it from tuyeres.

[0030] The operation method disclosed below has been conceived contrary to such common technical knowledge of those skilled in the art. In general terms, it is a method in which, instead of directly injecting coals through blast furnace tuyeres, carbonized material deliberately obtained from high-temperature dry distillation, together with gaseous and liquid fuels that are produced as by-products in gas-purification equipment (auxiliary equipment for high-temperature dry distillation furnaces), is charged into the furnace.

[0031] Specifically, first, coals and / or coal-alternative solid fuels outside the production range for blast furnace coke are subjected to dry distillation at temperatures whose maximum reaches 900°C or higher, thereby separating them into a solid fuel as char (C + ash) and a crude gas consisting of the remainder. Next, the crude gas is separated by gas-purification equipment into a gaseous fuel as COG, a liquid fuel as Tar, and a remaining liquid mainly composed of water (corresponding to ammoniacal liquor in coal dry distillation and to pyroligneous acid in biomass dry distillation). That is, from the charged raw materials, solid fuel (char), liquid fuel (Tar) and gaseous fuel (COG) are taken out by the above dry distillation and fuel-separation process.

[0032] Then, as for the solid fuel, a part or all thereof is crushed by a crusher to obtain coarse-crushed char, which is used as a sintering fuel for sinter, and all or part of the solid fuel that is pulverized so that 70% or more of particles have a particle size of 0.1 mm or less is injected into the blast furnace through tuyeres at the lower furnace. As for the gaseous fuel, a part or all thereof is converted (reformed) to synthesis gas (reducing gas) mainly containing CO and H 2 and then is blown into the blast furnace at a temperature of 800°C or higher. As for the liquid fuel, all or part thereof is injected into the blast furnace through tuyeres at the lower furnace.

[0033] The present embodiment will be described in further detail below.

[0034] In blast furnaces, top-charging coke (lump coke) has its most important role in maintaining gas and liquid permeability in the lower furnace, and therefore it is required to have high-temperature strength, a sufficient particle size, and low reactivity. Accordingly, coke-oven feed coals whose caking properties and VM, etc. are adjusted in advance are subjected to dry distillation in coke ovens at 1000-1300°C, and finally only lump coke having a required particle size is charged into the blast furnace. Lump coke also has roles as a reducing agent (for direct reduction and gas-based reduction) and as a heat source (a source of thermal energy through combustion), and therefore the amount of top-charging coke has conventionally been far greater than the amount required only to ensure gas and liquid permeability in the lower furnace.

[0035] On the other hand, the PCI is a technique that allows inexpensive non-coking coals to share the roles of coke as a reducing agent and as a heat source. In order to increase the combustion efficiency, coals are pulverized so that particles of 200 mesh (74 µm) or less account for 70-80% or more, thereby increasing the specific surface area. Coal kinds from HV coal (high-VM coal) to LV coal (low-VM coal) have been studied, and the focus has shifted from HV coal, which emphasizes combustion efficiency, to LV coal having a higher heating value as the PC rate increases. In recent years, as a CO 2 reduction measure, research has been conducted worldwide on mixing biomass-derived carbonized material into PC, but such research remains on an extension of conventional PCI technology.

[0036] The present inventor has devised a method for reducing CO 2 in blast furnace processes (Patent Literature 1). According to the CO 2 reduction method for a blast furnace process described in Patent Literature 1, it is preferable that blast-furnace tuyere-injection fuels should have high primary combustion heat and small thermal decomposition heat (the amount of heat required to decompose: C i H j O k = i×C + 0.5j×H 2 + 0.5k×O 2 ). The thermal decomposition heat of coal means the thermal decomposition heat of its VM (volatile matter), and therefore LV coal is preferable as a blast-furnace tuyere-injection fuel. This is also a common issue in conventional PCI methods.

[0037] To address the challenges of using HV coal, instead of directly supplying Coals with VM ≥ 6% to the lower furnace, the present invention devises a method that those Coals are carbonized into solid fuel (char) having VM < 5% (preferably ≤ 1%) in a high-temperature dry distillation furnace where the maximum temperature reaches 900°C or higher. Then, the solid fuel (char), gaseous fuel (COG), and liquid fuel (Tar) by-produced in gas purification equipment attached to the high-temperature dry distillation furnace, are supplied to the blast furnace by means optimal for each fuel.

[0038] Here, a high-temperature dry distillation furnace is equipment having a structure that prevents ingress of outside air, can secure a maximum dry distillation temperature of 900°C or higher, and is equipped with gas-purification equipment, and from a logistics viewpoint it is preferably installed near blast furnaces. There is no restriction on its type, and equipment such as a vertical coke oven may be used, and many existing coke ovens, including CDQ (coke dry quenching) facilities, can be diverted. In producing coke and char, it is necessary to separate their dry distillation furnaces and cooling equipment, but the gas-purification equipment may be shared. The reason why the dry distillation temperature is defined as 900°C or higher is that there is a correlation between the dry distillation temperature of coal and gasification (pyrolysis), and the gasification, including H 2 , is completed at around 900°C.

[0039] FIG. 5 compares the conventional PCI method with the present embodiment.

[0040] In the conventional PCI method, as a CO 2 reduction measure utilizing biomass, attempts have been made to mix biochar-also referred to as charcoal for woody biomass-, having VM of about 6-25% with coal. Because biomass has such properties as low bulk density, high moisture content and low yield of carbonized material, it is generally carbonized at a biomass collection site in a medium-temperature dry distillation furnace 14 at 400-600°C and then transported and delivered to the user, i.e. a steelworks. In addition, since coal contains moisture, it is first dried by a dryer 13 so that its moisture content becomes 1% or less, then finely pulverized by a pulverizer 7, and thereafter injected into the blast furnace 1 as PCI through tuyeres (not shown).

[0041] In the present embodiment, Coals brought into the steelworks are first separated in a high-temperature dry distillation furnace 2 into a solid fuel as char, a liquid fuel as Tar, a gaseous fuel as COG, and a remaining liquid mainly composed of water (corresponding to ammoniacal liquor in coal dry distillation and to pyroligneous acid in biomass dry distillation), and then only the fuels excluding the remaining liquid are supplied to the blast furnace 1. As for the char, a part or all thereof is, as required, finely pulverized by a pulverizer 7 so that 70% or more of particles have a particle size of 0.1 mm or less, and is injected into the blast furnace through tuyeres at the lower furnace. As for COG, a part or all thereof is converted in a reforming and heating furnace (hot stoves) 5, using partial combustion and / or agent gases (H 2 O and CO 2 ), into reducing gas (synthesis gas) mainly containing CO and H 2 , which is blown into the blast furnace 1. As for Tar, a part or all thereof is injected into the blast furnace through tuyeres at the lower furnace. It is preferable that the solid fuel (char) be finely pulverized by the existing pulverizer for blast-furnace injection 7.

[0042] VM in coals is separated in advance and char is injected from blast furnace tuyeres, which eliminates the endothermic reactions due to pyrolysis of coal (including the heat for heating and pyrolysis of the remaining liquid removed in the high-temperature dry distillation furnace 2) and increases the heating value (kJ / kg). Accordingly, the fuel rate (kg / tp) and oxygen rate (Nm 3< / tp) for 1 t of pig iron can be reduced.

[0043] Char is finely pulverized by a pulverizer 7 to increase its specific surface area (proportional to combustion efficiency) and is injected from dedicated injection lances provided in tuyeres at the lower furnace. The pulverizability index HGI (Hardgrove Grindability Index; a higher value means easier grinding) increases with dry distillation temperature and degree of carbonization (Non-Patent Literatures 5 and 6). Therefore, even HV coal, biomass-based fuels, and the like can be more easily pulverized by carbonization, which can reduce pulverizing energy.

[0044] COG is recovered at room temperature. Accordingly, if it is injected into the blast furnace as a reducing gas without being preheated to a temperature equal to or higher than that of the injection site, it becomes a cold source and cools the burdens inside the furnace, which is undesirable. Even when injecting into the shaft section, it is desirable to heat the gas to 800°C or higher. However, the gas contains hydrocarbon gases such as CH 4 , and heating it to 800°C or higher generates soot due to cracking phenomena (CH 4 = C+2H 2 ). Therefore, it is desirable to reform the hydrocarbons into a reducing gas (synthesis gas) mainly composed of CO and H 2 in a high-temperature atmosphere using partial combustion (C n H m +0.5n·O 2 =n·CO+0.5m·H 2 ) or agent gases (H 2 O, CO 2 ) before injecting the gas into the blast furnace. By injecting the reducing gas at an appropriate temperature into an appropriate location, the gas-based reduction ratio increases and the fuel rate (reducing agent rate) can be reduced (Patent Literature 1).

[0045] As for Tar, it is utilized as a reducing agent for chemical recycling by injecting it into the furnace from tuyeres, in the same manner as the conventional heavy oil injection method. It is desirable to inject it from the tuyeres at the lower furnace using a dedicated injection lance similar to an injection lance for heavy oil.

[0046] The effects of the above embodiment will be described also in light of the outside of the "steelworks boundary" shown in FIG. 5. In a conventional PCI route, biochar is generally produced in a medium-temperature dry distillation furnace 11 installed at a biomass collection site. Since the yield and VM of biochar are inversely correlated with the dry distillation temperature, the yield of low-VM biochar suitable for PCI is as low as 20 to 30%. Furthermore, by-product gas, tar, and the likes are difficult to utilize effectively for purposes other than combustion heat for the dry distillation furnace. Consequently, the net energy yield of the dry distillation furnace (= latent heat of recovered fuels / (latent heat of feed raw materials + external heat input)) becomes low.

[0047] In the present embodiment, the high-temperature dry distillation furnace 2 is installed within the steelworks, and COG & Tar derived from VM can be utilized within the steelworks; therefore, the feed raw materials have no problem to be high-VM fuels. Accordingly, biomass collection sites can adopt fuel conversion facilities prioritizing energy yield, such as low-temperature dry distillation furnaces (torrefaction furnace) 15 operating at 200 to 300°C or solidification equipment 16 operating below 200°C.

[0048] FIG. 2 (an example where the present embodiment is not applied; Patent Literature 1) and FIG. 3 (an example where the present embodiment is applied) summarize the flows within the steelworks boundary of FIG. 5 into ironmaking process flows that include the coke oven 3 and the sintering machine 9. In both examples, gas reforming is assumed to be a partial combustion method using oxygen in a hot stove (reforming / heating furnace) 5. The flow is configured to circulate and utilize the top gas from which CO 2 has been removed by a CO 2 separator 4, depending on the amount of reducing gas required in the blast furnace 1. At the same time, the flow allows for adjusting the amount of reducing gas produced and heated in the hot stove 5 by supplying CH 4 from the external source. In addition, both examples adopt a flow in which anthracite is used to compensate for any shortage of coke breeze used as a sintering fuel for sinter produced in the sintering machine 9. Note that although a screen is indicated in the flows, it is used in the broad sense of a classification device 10; it may be a literal screen (sieve) type, or a system such as air classification or a fluidized bed (this also applies to other figures).

[0049] The amount of sintering fuel used per 1 t of pig iron is calculated as OR×SR×C str , based on ore rate: OR (kg / tp; amount of charged ore per 1 t of pig iron), sinter ratio: SR (%; ratio of sinter in charged ore), and sintering fuel rate: C str , (kg / ts; amount of sintering fuel per 1 t of sinter). On the other hand, the supply amount of coke breeze is calculated as CR × R fc / R cc , based on coke rate: CR (kg / tp; amount of coke per 1 t of pig iron), lump coke ratio: R cc (%; weight yield of lump coke relative to coke-oven feed coals), and coke breeze ratio: R fc (%; weight yield of coke breeze relative to coke-oven feed coals). Therefore, the shortage of sintering fuel (coke breeze) per 1 t of pig iron: L c (kg / tp) is given by: L c =OR×SR×C str -CR×R fc / R cc (1) and the shortage is generally covered by anthracite.

[0050] It is obvious that the shortage increases if the first term on the right-hand side of Equation (1) increases or the second term decreases (and vice versa). Since self-fluxing sinter (sinter including auxiliary raw materials for adjusting slag basicity) has high reactivity in the blast furnace, SR (proportional to the first term) is on an increasing trend in conjunction with the situation where high-quality lump ore is becoming depleted. Also, CR (proportional to the second term) is decreasing due to the trend of the PC rate increase and CO 2 reduction. These strengthen the tendency of sintering fuel (coke breeze) shortage. According to the method of Patent Literature 1, CR can be reduced to 1 / 5 or less of that in the conventional blast furnace process, so the shortage of coke breeze will become decisive.

[0051] On the other hand, the use of anthracite in sintering machines has long posed issues, and its usage has been limited. Another feature of the present embodiment is that "instead of compensating for the shortage of sintering fuel with anthracite, it is compensated with char produced by high-temperature dry distillation (carbonization) of Coals," and at the same time, "liquid fuel (Tar) and gaseous fuel (COG) by-produced in the dry distillation are recovered; regarding COG, it is reformed into reducing gas (synthesis gas) primarily composed of CO and H 2 using partial combustion or agent gases (H 2 O, CO 2 ) and then injected into the blast furnace body; and regarding Tar, it is injected into the furnace from the tuyeres at the lower furnace."

[0052] The raw materials (coals, coal-alternative fuels, etc.), equipment (high-temperature dry distillation furnace, gas purification equipment, etc.), and operation methods (dry distillation temperature, dry distillation time, etc.) for this purpose can be made common to and shared with those for the production of char for blast furnace injection. Therefore, another feature is that its facility efficiency and operation efficiency can be synergistically improved. The integrated ironmaking process flow is shown in FIG. 4.

[0053] In FIG. 4, "Anthracite" and "LV coal" in FIG. 3 are integrated into "non-coking coals / coal-alternative fuels", and the entire amount thereof is processed in the high-temperature dry distillation furnace 2. A part of the carbonized solid fuel (char) is utilized as coarse-crushed char for a sintering fuel for sinter, and the rest is injected into the blast furnace as pulverized char.

[0054] The supply destinations of the liquid fuel (Tar) and gaseous fuel (COG) by-produced in the high-temperature dry distillation furnace 2 in FIG. 4 are the same as in FIG. 3; however, their supply amounts have increased by an amount corresponding to the production of the sintering fuel for sinter used in the sintering machine 9, which is added to the high-temperature dry distillation furnace 2. In other words, conventionally, even if anthracite was used as a sintering fuel, its VM latent heat could hardly be effectively utilized; however, in the present embodiment, it can be effectively recovered and utilized as liquid fuel and gaseous fuel.

[0055] The combustion time of a sintering fuel is roughly proportional to the square of the particle size. Since this combustion time is a factor determining the combustion pattern (combustion temperature and retention time in the sintering bed) which affects sinter quality and yield, a narrower particle size range is desirable. Therefore, for example, it is desirable to control the particle size range to about 2 to 3 mm. However, it is difficult to finely classify wet materials (sieves are prone to clogging), and conventionally, even when coke breeze was used, particles smaller than 1 mm or more than 5 mm were included in no small amounts. The char discharged from the high-temperature dry distillation furnace is dry-cooled to about 150°C in a CDQ (Coke Dry Quenching) facility (not shown) for the purpose of sensible heat recovery, similar to ordinary coke, and is then coarsely crushed. Since it is completely dry, screening and air classification are easy. Furthermore, an undersize fraction of, for example, less than 2 mm does not result in yield loss because it can be supplied to the pulverizer 7 for blast furnace injection; therefore, the particle size range sent to the sintering machine 9 can be controlled within a narrow range. Although the detailed particle size range is determined by the relationship with the exhaust gas suction speed of the sintering machine, FFS (Flame Front Speed), and the like, it is desirable to use coarse particles having a particle size of 1 mm or more and 6 mm or less as the sintering fuel for sinter.

[0056] Particle size control of the sintering fuel is also effective for coke breeze. Therefore, in FIG. 4, a line for charging coke breeze of, for example, less than 3 mm or more than 5 mm into the high-temperature dry distillation furnace 2 is indicated by an asterisk (), parallel to the line supplying the mixer 8.

[0057] As for the method of injecting pulverized char into the furnace in FIGS. 3 and 4, pneumatic transport is assumed, similar to the conventional PCI method. Since pulverized char produced by high-temperature dry distillation has almost no VM, the risk of coal dust explosion is low even with air transport. However, in the case of air transport or nitrogen transport, N 2 enters the furnace. Considering consistency with CO 2 separation (N 2 separation is difficult) and the top gas recycling system (N 2 tends to concentrate), it is desirable to use a reducing gas (such as top gas after decarbonation) as the carrier gas. Since the system is a pressurized system for injecting into the pressurized blast furnace, external air is unlikely to intrude into the injection system, which enables the use of preheated carrier gas. By increasing the sensible heat of the injected char and gas, the fuel rate and oxygen rate can be reduced. As a means to increase the injection sensible heat, a method to indirectly heat the transport piping from the outside of the pneumatic system using an electric heater, steam, or the like can also be applied.

[0058] Methods other than the pneumatic transport can also be applied to the blast furnace tuyere injection of pulverized char. When injecting liquid fuel (Tar) simultaneously, it is most rational to utilize COM (Coal Oil Mixture) and its process flow is shown in FIG. 1.

[0059] The COM 12 is equipment that slurries pulverized solid fuel using oils such as heavy oil or Tar as a transport medium and transports it. In FIG. 1, pulverized char and liquid fuel such as Tar are mixed in advance and injected into the blast furnace as COM fuel. Since the practical upper limit of the slurry concentration (ratio of solids in the total transport weight) is generally about 50%, when the coke-oven feed coals are bituminous coals, auxiliary liquid fuel (reducing agent) such as heavy oil is supplemented to prevent the slurry concentration from becoming excessively high. Note that since the pulverized char can be reduced corresponding to the supplemented amount of heavy oil or the like, the overall energy efficiency and CO 2 emissions do not deteriorate.

[0060] By the way, the yield (ratio of recovered materials to the weight of feed materials such as Coals) of solid fuel and liquid fuel in the high-temperature dry distillation furnace varies depending on the feed material such as Coals and its VM. Generally, as VM increases, the yield of solid fuel decreases and the yield of liquid fuel increases. When woody biomass fuel is subjected to dry distillation at 1000°C, the yields are roughly about 20% solid, 55% liquid, and 25% gas (Non-Patent Literature 2). Subtracting the yield of about 30% for pyroligneous acid (Non-Patent Literature 3), which cannot be used as fuel, from the 55% liquid, the ratio becomes solid fuel : liquid fuel : gaseous fuel = 20% : 25% : 25%, resulting in a slurry concentration of about 44% (< 50%). When waste plastics are subjected to high-temperature dry distillation, the ratio becomes solid fuel : liquid fuel : gaseous fuel = 1 : 2 : 2 (Non-Patent Literature 4), so the slurry concentration is about 33% (< 50%). That is, depending on the selection of the type of coal-alternative fuel and the mixing ratio, auxiliary liquid fuel such as heavy oil becomes unnecessary. Even when coal-alternative fuels are not used, CO 2 -free auxiliary liquid fuels such as biomass tar or e-fuels can be used instead of heavy oil.

[0061] By applying COM, the two control systems-the pneumatic transport system and the liquid injection system-can be integrated into one, and the tuyere injection lances can also be integrated. Furthermore, the heat of vaporization of the liquid can be utilized to protect the lance from the harsh temperatures inside the furnace. Also, while the transport temperature of heavy-oil-based COM is usually less than 100°C, it is easy to indirectly heat it to near the boiling point of the liquid fuel (e.g., 200°C, as both heavy oil and Tar have a wide range of boiling points) before injection through the tuyeres. This increases the sensible heat of the solid fuel and liquid fuel, which makes it possible to reduce the fuel rate (kg / tp) and the oxygen rate (Nm 3< / tp). In addition, since vaporization of the liquid fuel is promoted by the heating, the COM combustion efficiency also improves.

[0062] While the features centering on the process of the present embodiment have been described above, options for coal-alternative fuels in the present embodiment and their features will be described next.

[0063] In the present embodiment, as coal-alternative fuels, biomass fuels (including semi-carbonized fuels) are certainly suitable, but in addition, waste-derived solid fuels (RDF, RPF, etc.) containing a certain amount of impurities can also be used. When utilizing wastes, impurities and incombustibles contained within the wastes pose challenges. And the importance of pre-sorting and preprocessing is the same as in other methods to utilize solid-waste fuels; however, the present embodiment facilitates easier utilization of wastes than other methods for the following reasons.

[0064] First, the method of incinerating wastes to generate steam power has problems: chlorides in the wastes corrode metal walls, including boiler walls, and generate large amounts of dioxins. This is the cause of the low power generation efficiency in incinerators. Even when using RDF with chlorine concentrations managed below approximately 1%, it still leads to increased countermeasure burdens and feeding rate constraints. This undermines the cost advantage (economic viability) of waste-to-energy power generation and acts as a factor hindering its widespread adoption.

[0065] Next, although similar to the present embodiment, there is a method of chemical recycling by mixing waste plastics with coke-oven feed coals and charging the mixture into a coke oven (Patent Literature 2, Non-Patent Literature 4). The advantage of this method is that, under the high-temperature reducing atmosphere of the coke oven, more than 90% of the chlorine contained in the waste plastics transfers into the gas as HCl. When cooled with ammoniacal liquor containing ammonia generated from nitrogen derived from coke-oven feed coals, it turns into ammonium chloride (NH 4 Cl) and is rendered harmless. However, despite being able to neutralize 5.3 kg / t-coal (150 mol / t-coal) of chlorine per ton of feed coals, charging only 1 to 2 wt% of waste plastics (about 0.2 to 0.4 kg / t-coal in chlorine content) causes the coke strength to begin to decrease due to reasons other than chlorine; thus, there was a drawback that the effective charging ratio of waste plastics is limited to a few wt%. Moreover, this method focuses exclusively on waste plastics as a coal-alternative fuel, excluding biomass fuels and other types of wastes than waste plastics.

[0066] In the present embodiment, the use of a high-temperature dry distillation furnace is the same as in Patent Literature 2, and the ability to render the chlorine in the feed materials harmless is the same. However, since coarse-crushed char or pulverized char is produced instead of coke, there are no feed-material constraints required for coke strength. Therefore, the waste plastic charging ratio can be increased up to the balance limit with ammonia derived from coals (5.3 kg-Cl / t for coke-oven feed coals). According to Patent Literature 2, it is possible to increase the proportion of waste plastics containing 2 wt% chlorine up to 26 wt% relative to coke-oven feed coals. Since N and Cl in the coals and N in the waste plastics are 0.045 wt%, 1.59 wt%, and 0.4 wt%, respectively, the weight ratio (N / Cl) of nitrogen (N) to chlorine (Cl) in the feed materials for the high-temperature dry distillation furnace is determined to be 3.0. Here, suppose that the waste plastics are replaced with RDF-e.g., RDF in Non-Patent Literature 1 containing the components shown in Table 1 of FIG. 9-while using the same coals. Then, although the chlorine content is relatively high (> 1 wt%) as shown in Table 1, a maximum of 37 wt% of RDF can be charged for the N / Cl ratio to become 3.0. Note that the RDF carbonized material in Table 1 (FIG. 9) is obtained by dry distilling RDF at 500°C.

[0067] The above charging constraints are intended to neutralize hydrogen chloride generated from chlorine in the feed materials using ammonia generated from nitrogen in the same feed materials. However, in the present embodiment, the charging proportion of RDF can be further increased by effectively utilizing chlorine within the furnace before neutralizing it. Before explaining this point, impurities in wastes will be described in relation to it.

[0068] RDF, which is a solid fuel derived from municipal solid waste, has a quality issue that it contains impurities such as heavy metals and alkalis in addition to chlorine. When using RDF as fuel for thermal power generation, it causes problems similar to chlorine, such as deposits and material corrosion on boiler walls, increasing treatment costs for flue gas and fly ash.

[0069] When using RDF as a blast furnace tuyere-injection fuel, there are issues of RDF properties (proximate analysis values; FC, VM, Ash, moisture content) in addition to issues of RDF quality affecting pig iron quality and blast furnace operation. For example, the RDF in FIG. 9 (Table 1) (Non-Patent Literature 1) has excessively high VM content, and its decomposition heat cools the lower furnace, making it unusable as a blast furnace tuyere-injection fuel. The RDF char in FIG. 9 (Table 1) is obtained by dry distilling RDF at 500°C (Non-Patent Literature 1); however, due to its low carbonization yield (approximately 30%), the ash content of the carbonized material is concentrated / increased to 43.3% dry, making it unsuitable as a tuyere-injection fuel.

[0070] By the way, it is well known that if chlorine is contained in the feed materials charged into a high-temperature dry distillation furnace, chlorine (Cl 2 ) and hydrogen chloride (HCl) are generated due to thermal decomposition. It is also well known that high-temperature chlorine-based gas chlorinates many oxides and metals to produce chlorides with high vapor pressure. This process, known as the chlorination roasting method (chloride volatilization method), has been utilized for heavy metal recovery and other applications.

[0071] In the present embodiment, concurrently with dry distillation, quality improvement and deashing of the carbonized material (char) are achieved by chloride-volatilizing heavy metals, alkalis, and the like in the ash-where the reduction-chlorination roasting of the feed materials is performed by actively utilizing the high-temperature reducing atmosphere in the high-temperature dry distillation furnace and the chlorine introduced from feed materials such as waste.

[0072] The chlorination reaction of an oxide of a metal element M is expressed by the following equation: MO a + b × Cl 2 = MCl 2 b + a / 2 × O 2 ΔG 0 0 < 0

[0073] Although the standard free energy change (ΔG 0< ), which is a function of temperature, must satisfy ΔG 0< < 0 for the reaction to proceed, the chlorination reaction tends to become ΔG 0< < 0. Regarding chloride volatilization, its application has been investigated for treating heavy metals in incineration ash of municipal solid waste. However, since these investigations assumed an oxidizing atmosphere, it was considered that the volatilizable heavy metals were limited. Meanwhile, since the inside of a high-temperature dry distillation furnace has an atmosphere where CO and H 2 gases are generated and carbonized material (C) is produced, the following reactions proceed concurrently. C + 1 / 2 × O 2 = CO ΔG 0 C < 0 CO + 1 / 2 × O 2 = CO 2 ΔG 0 CO < 0 H 2 + 1 / 2 × O 2 = H 2 O ΔG 0 H 2 < 0

[0074] Multiplying equations (3), (4), and (5) by a and adding them to equation (2) yields: MO a + a × C + b × Cl 2 = MCl 2 b + a × CO ΔG 0 0 + ΔG 0 C MO a + a × CO + b × Cl 2 = MCl 2 b + a × CO 2 ΔG 0 0 + ΔG 0 CO MO a + a × H 2 + b × Cl 2 = MCl 2 b + a × H 2 O ΔG 0 0 + ΔG 0 H 2 In the range of 300 to 1200°C, where -500 < ΔG 0< C , ΔG 0< CO , ΔG 0< H2 < -300 kJ / mol, the free energy change for any of equations (6), (7), and (8) becomes sufficiently lower than that of equation (2); therefore, the reduction-chlorination reaction proceeds readily in terms of free energy. Note that, since chlorine is consumed to react with hydrogen to generate hydrogen chloride (H 2 +Cl 2 = 2HCl), it is important whether the free energy change is lower than the standard free energy change of this reaction.

[0075] Further, for example, in a carbonization chamber of a vertical coke oven, the heating of charged materials proceeds from the furnace wall toward the center. This allows the chlorine-containing gas and the charged materials to contact each other over a wide temperature range. Consequently, the reduction-chlorination reaction proceeds sequentially during the heating process, and chlorides with high vapor pressure volatilize sequentially starting from low temperatures. Finally (by the completion of dry distillation at 900°C or higher), diverse oxides can be reduced and chloride-volatilized. Note that, since the temperature generating chlorine gas is lower than the chloride volatilization reaction temperature, depending on the width from the furnace wall to the center of the coke oven, the generated chlorine gas may flow upward through charged materials at low temperatures. This poses a possibility that the efficiency of the chloride volatilization reaction (reaction efficiency) drastically decreases. However, the chloride volatilization reaction efficiency can be enhanced by a raw material preprocessing method, wherein all or part of the chlorine-containing feed materials are molded in advance (into briquettes, injection-molded products, etc.) and then charged into the high-temperature dry distillation furnace (such as a coke oven).

[0076] FIG. 8 shows an unreacted-core model assuming a spherical briquette. In the heating process after charging, a temperature gradient occurs in the thickness direction (radial direction) inside the briquette. Chlorine gas generated in the low-temperature region inside the briquette (chlorine gas generation front in FIG. 8; radius R1) passes through the chloride volatilization temperature front of impurity A (impurity A reaction front in FIG. 8; radius R2)-where impurity A is removed by chloride volatilization-before being exhausted from the briquette surface (high temperature close to the furnace temperature). The chlorine gas generation front and the impurity A reaction front start near the briquette surface immediately after charging and move inward with dry distillation time (R1 and R2 approach zero), resulting in chloride volatilization progressing across many regions within the sphere. Although impurities other than A have corresponding volatilization temperatures, chlorine gas necessarily passes through those temperature fronts (R2s different from A) as well to chloride-volatilize and remove them during its passage. In other words, briquetting allows for the efficient removal of any impurity with a volatilization temperature lower than the dry distillation temperature. Furthermore, the excess chlorine gas vented from the briquette is given an opportunity to react with unreacted feed materials in the flow path. And the longer the flow path is, like in a vertical coke oven, the easier it is to improve the reaction efficiency.

[0077] As can be seen in FIG. 8, if R1 and R2 are separated, impurities existing deeper inside than R2 when R1 reaches the furnace center cannot be volatilized by the chlorine within the briquette. In other words, the temperature gradient inside the briquette is important. Not only the chlorine concentration inside the briquette but also moisture and oil content contribute to improving reaction efficiency by promoting a steeper temperature gradient through their latent heat of gasification (cold heat source). Furthermore, since the gas flow is upward in the coke oven, a method of charging briquettes with high chlorine content, moisture, and oil content into the lower layer and charging briquettes and powdery feed materials with low chlorine content, moisture, and oil content into the upper layer is also effective. This method delays chlorine gas generation in the lower layer and increases the heating rate in the upper layer, thereby promoting the chloride volatilization reaction to proceed in the upper layer, effectively improving impurity removal efficiency and chlorine gas utilization efficiency.

[0078] Although the above explanation took briquettes as an example, injection-molded products such as RDF and RPF, or pellets may be used. Regarding the shape, a spherical shape is ideal, but a cylindrical shape or a pillow shape is also acceptable. As for the coke type, although vertical coke ovens have higher reaction efficiency, horizontal coke ovens can also be effectively utilized if the feed materials are made into briquettes or the like.

[0079] As a result of a detailed investigation into the free energy changes of chlorination reactions and the vapor pressures of chlorides for the major components contained in RDF, it was found that heavy metals (Zn, Pb, Cu) and alkali metals (Na, K), which affect the blast furnace condition and / or pig iron quality, can be removed by volatilization. Furthermore, it was found that Fe, Mn, Mg, and Ca are also removable by volatilization, which offers the advantage of contributing to an ash reduction (deashing) effect. Conversely, regarding Si, Al, and Cr, while they can be chloride-volatilized as metals, it was found that as oxides (SiO 2 , Al 2 O 3 , Cr 2 O 3 ), the formation of hydrogen chloride is prioritized, resulting in stable compounds. Therefore, these are suitable as refractory components for the high-temperature dry distillation furnace.

[0080] Next, the following describes in detail, using Figure 6, the method to determine the appropriate chlorine content when blending coals and RDF for feeding into a high-temperature dry distillation furnace. The horizontal axis of the figure shows the mixing ratio X of the two types of feed materials; for example, X = 0 indicates 100% coals, and X = 1 indicates 100% RDF. The vertical axis shows the ratio (wt%) of N and Cl components in the feed materials; however, for N, it is scaled by multiplying the conversion ratio 1 / k to NH 3 . Since k depends on the fuel type, it must be confirmed for each fuel; however, for a mixture of coals and waste plastics, k = 3 as described above. Let Y N (X) denote the N content (wt%) of the blended fuel at the mixing ratio X and Y Cl (X) denote the Cl content (wt%) at the same mixing ratio. These are expressed by the following equations, which are shown as dashed and solid lines in FIG. 6. Y N X = N 1 − N 0 ⋅ X + N 0 Y Cl X = Cl 1 − Cl 0 ⋅ X + Cl 0 N 0 : N content in coal (wt%) N 1 : N content in RDF (wt%) Cl 0 : Cl content in coal (wt%) Cl 1 : Cl content in RDF (wt%)

[0081] Let Cl v (X) denote the amount of Cl consumed in chlorinating impurities in RDF and coals; then the chlorine content Y Cl (X) in the mixed fuel becomes Y Cl (X) - Cl v (X) after the chlorination reaction. For a mixing ratio where Y Cl (X) - Cl v (X) < 0, the chlorine quantity is insufficient for the chlorination targets, and it is desirable that Y Cl (X) - Cl v (X) ≥ 0. Conversely, if Y Cl (X) - Cl v (X) ≥ 0, HCl is generated, so it is necessary to satisfy the condition [Y N (X) ≥ Y Cl (X) - Cl v (X)] such that it can be neutralized by NH 3 in the ammoniacal liquor.

[0082] In an operation with 100% RDF, Y Cl (1) - Cl v (1) = Cl 1 - Cl v (1). Therefore, it is understood that the RDF should have a Cl ratio satisfying the following expression (Equation 11). N 1 / k ≥ Cl 1 − Cl v 1 ≥ 0 ⇔ N l / k + Cl v 1 ≥ Cl 1 ≥ Cl v 1 For example, the ash in the RDF of FIG. 9 (Table 1) contains 60 wt% of SiO 2 and Al 2 O 3 (inventor's inference from Non-Patent Literature 1), and the remaining 40 wt% can be volatilized (deashed) by reduction chlorination. Calculated from the ash components, Cl v (1) = 5.5wt%. The current RDF contains 1.2 wt% of Cl, which is insufficient for the chlorination reaction even at a mixing ratio of 1 (100% RDF). The chlorine concentration can be increased to 5.5% or more.

[0083] When not considering the chlorination reaction in conventional dry distillation furnaces, Cl v (X) = 0 (Cl 1 < 3), and the mixing ratio X v0 in FIG. 6 becomes the RDF mixing limit. This corresponds to the limit point described as X v0 = 0.37 (Cl 1 = 1.2) for the case in FIG. 9 (Table 1) (X v0 · Cl 1 = 0.44%). The present embodiment enables the active utilization of chlorine for chloride volatilization of impurities, thereby expanding the mixing ratio of chlorine-containing wastes up to 100% while also allowing for further increase in the wastes' chlorine concentration. Note that, even if the chlorine concentration Cl 1 in the wastes or the chlorine charge amount derived from wastes Cl 1 · X v0 does not reach the levels described above, it is obvious that the effects of the present invention can still be enjoyed to a considerable extent if they are increased beyond conventional normal standards or limits. Specifically, this applies to cases where the chlorine concentration Cl 1 (wt%_dry) in the wastes charged into the high-temperature dry distillation furnace and / or the wastes charging ratio X v0 (wt%_dry) satisfy at least either Cl 1 ≥ 3% or Cl 1 · X v0 ≥ 0.5%.

[0084] While it is important to grasp Cl v (X); however, it is possible to determine it before operation by analyzing ash, and it can also be corrected during operation based on the NH 3 concentration in the ammoniacal liquor. Also, due to the characteristic of Y N (X) = Y Cl (X) - Cl v (X), the HCl generation rate can be adjusted by changing the mixing ratio. Therefore, by grasping the concentration of NH 3 and NH 4 Cl in the ammoniacal liquor, the margin of the mixing ratio change can be understood before adjustment.

[0085] Now, let us reconsider the ash (SiO 2 , Al 2 O 3 ) remaining in the carbonized material (char) produced from RDF in the high-temperature dry distillation furnace. According to the present embodiment, in the RDF of FIG. 9 (Table 1), 40% of the ash can be reduced and / or volatilized (deashed), lowering ash content from 11.5% to 6.9%. However, since the FC of RDF is low at 14.7%, the ratio of ash to FC remains high (Ash / FC = 47%). As described above, since the Tar yield of plant-based biomass is comparable to the char yield, the ash content (wt%) in the total injection-fuel combining solid and liquid can be considered to be about half of the ash content (wt%) in the solid fuel alone. However, compared to ash / FC = 12.5% and 14% for coke-oven feed coal (C / O feed coal) and LV coal shown later [Table 2 in FIG. 10], further reduction of ash is desirable as a blast furnace tuyere-injection fuel.

[0086] Therefore, focusing on the feature of the present embodiment that "the carbonized material (char) produced in the high-temperature dry distillation furnace is pulverized (similar to PCI) and transported via COM to be injected from the blast furnace tuyeres," a method to further deash the char was devised, which is to install "deashing equipment using a selective agglomeration method using heavy oil or the like" between the pulverization equipment and the COM transport. Specifically, this devised method utilizes at least a portion of the aforementioned liquid fuel to de-ash the carbonized material (char) which is the solid fuel after pulverization.

[0087] Coal deashing methods can be broadly categorized into flotation selection methods and selective agglomeration methods, which utilize the hydrophobic difference between coal and ash, and heavy liquid separation methods, which utilize specific-gravity differences. To increase the deashing ratio, it is important to finely pulverize the coal to separate the carbonaceous matter from the inorganic matter; however, in heavy liquid separation methods and ordinary flotation methods, the more finely the coal is pulverized, the lower the deashing ratio and the carbonaceous matter recovery ratio become. In this respect, the Oil Agglomeration method using heavy oil or the like and the agglomeration-flotation method are advantageous and have already been developed as coal deashing technologies (Patent Literature 3, Non-Patent Literature 7). Another advantage is that these deashing processes after fine pulverization can remove water-soluble impurities that may remain to some extent as unreacted components in the carbonized material.

[0088] As shown in FIG. 1, in the present embodiment, since the whole amount of the product (char) from the high-temperature dry distillation furnace is finely pulverized for the blast furnace injection fuel, the preprocessing (fine pulverization) required for the deashing process is already completed. Therefore, it is desirable to additionally install deashing equipment 11 downstream of the pulverizer 7, depending on the ash content of the char (e.g., by dedicating the equipment downstream of the discharge of batteries of high-temperature dry distillation furnaces using RDF). As the agglomerating agent (binder), low-volatility oil is desirable, and it is preferable to utilize heavy oil and / or Tar generated in the coke oven 3 and / or the high-temperature dry distillation furnace 2. When using heavy oil or Tar as an agglomerating agent, it is desirable to maintain it at 40 to 60°C due to its viscosity characteristics. As shown in FIG. 5, the related equipment of the present embodiment (high-temperature dry distillation furnace 2, COM 12, blast furnace 1) is preferably installed adjacent to each other in principle. Accordingly, the sensible heat of the deashing equipment 11 is transferred to the sensible heat of the COM fuel and ultimately introduced into the furnace as the sensible heat of the blast furnace tuyere-injection fuel, thus avoiding energy waste.

[0089] According to the flow in FIG. 1, coke breeze is all charged into the high-temperature dry distillation furnace. This allows the removal (reduction chloride volatilization) of alkalis (Na, K) remaining in the coke breeze which hinder the operation of the sintering machine and blast furnace-in the high-temperature dry distillation furnace, and instead promotes the reduction chlorination reaction of equation (6) by using coke breeze as its C source.EXAMPLES

[0090] As an example, the amount of C consumed (∝ CO 2 emissions) in the ironmaking area (blast furnace, coke oven, sintering machine) was calculated, using the carbonaceous materials shown in FIG. 9 (Table 1) on a 100% sinter basis. Coke-oven feed coals are the coals adjust-blended with caking properties and coalification degree for coke production, whereas LV coals and HV coals are non-coking coals having no (or low) caking properties and are used in the high-temperature dry distillation furnace.

[0091] Note that although the high-temperature dry distillation furnace is equipment for dry distilling Coals at a maximum temperature of 900°C or higher, the calculation in the example assumed equipment (including gas purification equipment) that dry distillates at a temperature equivalent to that of a conventional coke oven. Furthermore, the premise is that the whole amount of COG generated from the coke oven and the high-temperature dry distillation furnace is used for the purpose of a reducing agent (blast furnace reducing gas), while blast furnace top gas or external fuel (CH 4 ) is used as combustion fuel for dry distillation heat, combustion fuel for the hot stove, and combustion fuel for the sintering machine (ignition furnace, DeNOx system), which are for the purpose of heat sources.

[0092] First, Table 3 in Figure 11 compares the estimations of the carbon (C) consumption between the case using LV coal in FIG. 2 (Patent Literature 1) where the present embodiment is not applied, and the cases using LV coal or HV coal in FIG. 3 where the present embodiment is applied to the blast furnace tuyere injection line. Note that the figures in the table are rounded to the nearest digit, so the sum of the figures may not necessarily match (the same applies to other tables).

[0093] Comparing the cases "FIG. 2 × LV coal" and "FIG. 3 × LV coal"-using the same LV coal, the "FIG. 3 × LV coal" case applying the present embodiment shows an improvement of approximately 18 kg / tp in the carbon intensity of the blast furnace process. Although approximately 9 kg / tp of carbon intensity is added in the high-temperature dry distillation furnace, a total reduction of approximately 9 kg / tp of carbon intensity is achieved in the total ironmaking area.

[0094] In FIG. 3, even when LV coal is replaced with HV coal, the total carbon intensity increase is limited to 3 kg / tp, reducing the impact of changing coal types, and resulting in a 5 kg / tp improvement compared to "FIG. 2 × LV coal" without applying the present embodiment. Although not shown in the table, in the case of "FIG. 2 × HV coal" where the present embodiment is not applied, the coal rate × oxygen rate becomes 582 kg / tp × 368 Nm 3< / tp, making operation difficult; therefore, HV coal cannot be used. However, in the "FIG. 3 × HV coal" case, the rates can be reduced to 228 kg / tp × 137 Nm 3< / tp-less than half that of the conventional method-achieving a lower level of carbon intensity (CO 2 intensity) than the example using LV coal (Patent Literature 1) without applying the present embodiment. This demonstrates that the applicable range of carbonaceous materials can be expanded.

[0095] The bottom row of FIG. 11(Table 3) shows the C-reduction amount when converting CH 4 to H 2 . Since the carbon intensity of the conventional hot-blast based blast furnace process is approximately 630 kg / tp (2.3 t / tp in CO 2 equivalent), if green hydrogen can be utilized instead of CH 4 , CO 2 intensity can be halved without considering CO 2 reuse or underground storage.

[0096] Next, Table 4 in FIG. 12 shows the cases using LV coal or HV coal in FIG. 4, where the present embodiment is also applied to the sintering fuel of the sintering machine.

[0097] In the "FIG. 4 × LV coal" case, the carbon intensity deteriorates (increases) by 7 kg / tp compared to "FIG. 3 × LV coal", and in "FIG. 4 × HV coal", the carbon intensity deteriorates by 10 kg / tp compared to "FIG. 3 × HV coal". The main cause is the increased carbon intensity in the high-temperature dry distillation furnace due to the increased production of sintering fuel. Still, "FIG. 4 × HV coal" has a carbon intensity 8 kg / tp lower than "FIG. 2 × LV coal", contributable to CO 2 emission reduction regardless of coal types.

[0098] Furthermore, if HV coal is converted to biomass-based fuel (including semi-carbonized fuel), carbon intensity derived from HV coal can be zero. Therefore, if all HV coal is converted, carbon intensity will be reduced by 248 kg / tp, reducing the total carbon intensity from 381 kg / tp to 133 kg / tp (less than 1 / 4 of the conventional blast furnace process). If CH 4 is converted to green H 2 , carbon intensity can be further reduced by 57 kg / tp, suppressing total carbon intensity to 76 kg / tp (about 1 / 8 of the conventional blast furnace process). Moreover, 45 kg / tp of the 76 kg / tp is the C component in the pig iron (hot metal), which can be recovered as CO gas when refining the pig iron into steel in a converter installed downstream, and can also be used as reducing gas for the blast furnace. This means total carbon intensity can be suppressed to approximately 30 kg / tp (about 1 / 20 of the conventional blast furnace process).

[0099] As described above, the present embodiment enables the utilization of wastes other than pure biomass fuels as coal-alternative fuels. Although the coal emission factors of waste-derived solid fuels are not zero, they provide substantially the same CO 2 reduction effects as biomass fuels in terms of reducing the potential CO 2 emissions from the fossil fuels (coals) they replace.

[0100] Table 5 in FIG. 13 shows the cases using LV coal or HV coal in FIG. 1-a model case of the present embodiment (where pulverized char transport is changed from the pneumatic transport in FIG. 4 to COM transport).

[0101] The total carbon intensity for LV coal remains unchanged from Table 4 in FIG. 12, but for HV coal, it increases compared to Table 4. However, when replacing coal and heavy oil with biomass fuel, the improvement effect in each case is greater than that of respective cases for biomass fuel conversion in Table 4.

[0102] The heavy oil requirement for COM is determined by the ratio of solid fuel to liquid fuel, becoming unnecessary at a ratio of 1:1. As described above, biomass-based fuels and waste plastics often provide higher liquid fuel yields than solid fuel yields, increasing their blending ratio (decreasing the coal ratio) eventually eliminates the need for heavy oil, and at a coal blending ratio of 0, the solid fuel concentration in COM becomes < 50 wt%. In other words, since fossil fuels such as coal and heavy oil are no longer required, apparent CO 2 intensity can be reduced to 114 kg / tp (less than 1 / 5 of the conventional blast furnace process). The gaseous fuel (COG) yield of biomass-based fuels and waste plastics is also higher than that of HV coal. Therefore, if the blending ratio of these coals increases, externally procured CH 4 can be substituted by the increased COG, making it possible to achieve a total carbon intensity of 76 kg / tp without using green H 2 or C-recycling / CO 2 -storage. This value is approximately 1 / 10 of the total carbon intensity in the conventional blast furnace process. In this regard, the fact that there are 200 million t / y of wastes incinerated in Japan (estimated by the present inventor) represents an advantage from the perspective of coal-alternative fuel availability (urban-type circular resources generated every year). By chemically recycling those that meet quality and economic criteria as coal-alternative fuels for the present embodiment, it is possible to lead to CO 2 reduction in the steel industry and waste management.

[0103] So far, the embodiments and examples have described a method of utilizing carbonized material (char) produced in a high-temperature dry distillation furnace for the blast furnace process, wherein coarse-crushed char produced by crushing all or part of the char with a crusher is used as a sintering fuel for sinter, and the undersize fraction generated in the crushing process or the pulverized char produced in a pulverizing process is injected from the tuyeres at the lower part of blast furnace. However, as a means for supplying carbonized material into the blast furnace, in addition to the method of injecting it from the tuyeres at the lower furnace after pulverization, there is also a method of charging all or part of the char after crushing from the furnace top together with coke and ore, as shown in FIG. 7.

[0104] The top-charged char is preheated to the lower furnace boundary temperature (e.g., 1300°C) while descending to the lower furnace. (1) This enhances the heat transfer efficiency of the char combustion heat to the lower furnace, and simultaneously, (2) it reduces the heat-required in the lower furnace to heat the ash (mainly SiO 2 ) in char up to approximately 1500°C for being discharged as slag-to about 1 / 5. Therefore, the fuel rate can be further reduced. In other words, charging char from the furnace top has a thermal effect equivalent to reducing the ash content to 1 / 5, so even the char (high ash content) produced from feed materials having a high ash content relative to FC (fixed carbon)-such as RDF-can be utilized without deashing process. Note that the preheating effect of ash in char has a theoretically similar effect when utilized as a sintering fuel for sinter charged from the furnace top.

[0105] If char charged from the furnace top is pre-processed with high-temperature dry distillation, it contains almost no volatile matter. Accordingly, even if gas is generated from the char due to preheating at 900°C or higher, it will contain almost no tar or hydrocarbons. Even if hydrocarbons are present, they will be gas-reformed by H 2 O and / or CO 2 . Therefore, the gas can be treated as normal top gas (CO, H 2 , CO 2 , H 2 O, N 2 ) without hindering operation.

[0106] Charging char from the furnace top is not only thermally superior to direct injection into the lower furnace, but also functions to preserve coke quality; since char have higher reactivity than coke, it gasify sacrificially before coke undergoes gasification reactions (C + CO 2 = 2CO, H 2 O + C = H 2 + CO). Since the reaction rate (kg / s) of a particle is proportional to its specific surface area (m 2< / kg), finer particle size is desirable unless it is blown away. Assuming the average particle size of coke in the lower furnace is approximately 30 to 35 mm, a particle size of 10 mm or less is desirable to achieve a specific surface area (proportional to combustion rate) 10 times that of the coke. Also, a particle size of 3 mm or more is desirable to prevent the char from being easily blown away by even a slight amount of blow-by gas. In short, it is desirable for the top-charged char to mainly (i.e., 70% or more) have a particle size between 3 mm and 10 mm.

[0107] Since classification devices such as screens have classification efficiency limits, some char smaller than the sieve mesh is also charged from the furnace top. Regarding char discharged out of the furnace accompanying the top gas, it can be collected by a primary dust collector or a secondary dust collector. It may be pulverized and injected from the tuyeres at the lower furnace. However, since it also contains iron-based dust and auxiliary raw material dust in addition to carbonaceous material, it can be effectively utilized as a raw material for sinter (sintering fuel), as has been done conventionally.

[0108] Increasing the amount of top-charging char will shift the fuel-combustion source in the lower furnace from primarily tuyere-injection fuel (pulverized char and Tar) toward top-charging char. Combustion by tuyere-injection fuel tends to generate higher combustion heat on the furnace wall side than at the furnace center, as in conventional blast furnaces. However, since top-charging char can be distributed equally in the radial direction, combustion is more likely to occur uniformly in the radial direction, enabling higher heat at the furnace center where combustion ends. In other words, the heat distribution in the lower furnace can be adjusted by adjusting the top-charging char rate.

[0109] In addition to the aforementioned method, another method for adjusting the heat distribution in the lower furnace is to extend the combustion time of char by mixing coarser particles into the pulverized char. FIG. 7 shows a line installed to bypass the pulverizer and mix the undersize fraction (fine char) from the screen after the crusher into the pulverized char, for the purpose of adjusting the pulverized char combustion time. However, for char with a high ash content, it is desirable to perform pulverization and deashing processes before converting it into COM. Since the amount of pulverized char injection is reduced by using top-charging char, the oil required for COM transport can be covered solely by Tar derived from coal or coal-alternative fuels (i.e., eliminating the need for external fuel such as heavy oil).

[0110] On the other hand, disadvantages of top-charging char include: - Increase in slag volume and auxiliary raw materials (raw material-derived CO 2 sources) in case of char with a high ash content compared to tuyere injection with deashing; - Slower responsiveness to changes in the lower furnace owing to its long time to reach the lower furnace. Accordingly, it is desirable to appropriately adjust the ratio between top-charging and lower-furnace injection while considering factors such as ash content in the char, yield of liquid fuel as Tar, undersize fraction of char-crushing, and the like, while also observing the radial heat distribution in the lower furnace as described above. Furthermore, the ability to adjust operations according to raw materials and furnace conditions is a strength to use top-charging and lower-furnace injection together.

[0111] From the above, it is understood that the following method is distinctive and effective as an operating method in the blast furnace process: Carbonized material (char)-solid fuel produced in a high-temperature dry distillation furnace-is utilized such that all or part of the solid fuel is crushed by a crusher and used as a sintering fuel for sinter and / or as a top-charging material for the blast furnace; also, all or part of the solid fuel is pulverized so that 70% or more of particles have a particle size of 0.1 mm or less and is injected from the blast furnace tuyeres at the lower furnace.

[0112] Table 6 in FIG. 14 shows a comparison of carbon consumptions between the "FIG. 1" case (pulverized-char injection to the lower furnace alone; without deashing) and the "FIG. 7" case (combined with coarse-char top-charging), using the HV coal shown in Table 2 of FIG. 10. Note that the "FIG. 7 x HV coal" case exemplifies a scenario where the ratio of the top-charging coarse-char to the lower-furnace-injection pulverized-char is determined so that external fuel (heavy oil) is not required as the COM for lower-furnace injection; this ratio is 77% : 23% in the "FIG. 7 x HV coal" case. However, this ratio varies depending on the ratios of FC (Fixed Carbon) and VM (Volatile Matter) of the coals (or coal-alternative fuels) including coke-oven feed coals, the gangue content of ore, the operating conditions of the coke oven and the high-temperature dry distillation furnace, etc.

[0113] In the "FIG. 7 × HV coal" case shown in Table 6 of FIG. 14, the total carbon intensity is smaller than in any other example (case) because high C-emission-factor fuels such as coal and heavy oil could be reduced. Therefore, it is understood that, at least when using coals as described in Table 2 of FIG. 10 without deashing, it is preferable to charge char from the furnace top as much as possible, and it may also be used as a sintering fuel for sinter which is similarly charged from the furnace top. In addition, the total char consumption of coarse char and pulverized char in the case (= 173 kg / tp) is the smallest compared to other cases in FIGs. 1, 4, and 5, and the CH 4 consumption is the largest compared to other cases. Thus, it can be said that this method is most suitable for using biomass-based (including waste-based) fuels with low carbon yield and high COG yield as alternative fuels.

[0114] In existing steelworks, two or more (multiple) blast furnaces are often installed. In this case, as a method for reducing CO 2 derived from CH 4 described in Table 3 (FIG. 11) to Table 6 (FIG. 14), one or more of the multiple blast furnaces can be modified to the system of the present invention, and surplus energy (including converter gas) from the remaining conventional blast furnaces can be used in place of CH 4 . Consequently, the production amount using this invention leads to a CO 2 reduction of the entire steelworks.

[0115] For example, in the "FIG. 7 × HV coal" case of FIG. 14 (Table 6), the carbon intensity per 1 t of pig iron is 362 kg / tp. However, by utilizing surplus gas from an adjacent blast furnace, the of 68 kg / tp (= 128 Nm 3< CH 4 / tp = 4.6 GJ / tp) derived from CH 4 becomes unnecessary, reducing the carbon intensity to 294 kg / tp (equivalent to 1.08 t-CO 2 / tp CO 2 intensity). That is, most of the coke-oven feed coals can be replaced with HV coal and expensive external fuels also can be eliminated, thus halving the blast furnace CO 2 intensity from the current approx. 2.2 t-CO 2 / tp to 1.08 t-CO2 / tp. Note that the surplus energy in the conventional blast furnace process is 7.4 GJ / tp (estimated by the present inventor) including Tar, which balances 0.62 tp (= 4.6 / 7.4) of a conventional blast furnace production with 1 tp of "FIG. 7 × HV coal" production.

[0116] Although the present invention has been described with reference to the blast furnace as a metallurgical furnace, it can also be applied to other metallurgical furnaces due to its principles and effects. Some examples are illustrated below.

[0117] For example, as a CO 2 reduction measure in the steel industry, a process of "producing DRI (Direct Reduced Iron) in a hydrogen-based direct reduction furnace and melting and carburizing the DRI in an electric smelting furnace to produce pig iron (hot metal)" is being developed in Europe and Japan as a substitute for the conventional blast furnace process. The direct reduction furnace (metallurgical furnace) requires green hydrogen to replace conventional natural gas, and the electric smelting furnace (metallurgical furnace) requires a carburizing agent such as coke, posing issues regarding their energy efficiency and CO 2 reduction amount limits. However, according to the present invention, by utilizing coke ovens-which will become idle facilities due to the shutdown of existing blast furnaces-as high-temperature dry distillation furnaces and preprocessing wastes close to carbon neutral (CN), it becomes possible to provide CN gaseous fuel (COG) as a hydrogen alternative for the reducing agent and CN high-quality solid fuel (char) as a coke alternative for the carburizing agent. Liquid fuel can also be used as heating fuel for a gas reformer for the direct reduction furnace, etc.

[0118] The carburizing agent needs to penetrate the slag layer, which has a higher specific gravity than the carbonaceous material, and enter the hot metal. Therefore, high-temperature dry distillation is crucial to minimize VM (volatile matter) that generates gas. Furthermore, since the carburization rate is inversely proportional to the particle size, it is also effective to inject it after pulverization.

[0119] In addition, as a CO 2 reduction measure in the steel industry, the conventional process of "producing molten steel by melting scrap or DRI in an electric arc furnace" is also being promoted instead of the blast furnace. However, since electricity costs significantly affect the economics of the electric arc furnace (metallurgical furnace), in countries with high electricity rates-including Japan, fossil fuels (carbon, natural gas, heavy oil, etc.) have actually been heavily used as slag foaming agents or fuels for scrap melting burners, aiming to reduce electricity intensity. Furthermore, as a countermeasure against dioxins in electric arc furnace exhaust gas, burners are required to decompose DXNs at high temperatures, and fuel consumption is even increased, contrary to the reduction of electricity intensity. However, according to the present invention, by utilizing coke ovens-which will become idle facilities due to the shutdown of existing blast furnaces-as high-temperature dry distillation furnaces, it becomes possible to obtain CN high-quality slag foaming agents and metallurgical fuels.

[0120] As other metallurgical furnaces, it can also be utilized to preprocess raw materials for cupolas (especially coke-less cupolas), smelting reduction furnaces, non-ferrous smelting furnaces, lime calcination furnaces, and the like.

[0121] Note that the direct reduction furnaces and electric smelting furnaces exemplified above exist as independent metallurgical furnaces, respectively, and the present invention can be utilized for each of them. Also, regarding the high-temperature dry distillation furnace, while the utilization of existing coke ovens has been exemplified from the perspective of utilizing existing facilities, the present invention is not limited thereto. There is no problem in installing a high-temperature dry distillation furnace of a type different from coke ovens at a steelworks where no coke oven exists.INDUSTRIAL APPLICABILITY

[0122] The technology according to the present invention also relates to CO 2 reduction from wastes.

Examples

examples

[0090]As an example, the amount of C consumed (∝ CO 2 emissions) in the ironmaking area (blast furnace, coke oven, sintering machine) was calculated, using the carbonaceous materials shown in FIG. 9 (Table 1) on a 100% sinter basis. Coke-oven feed coals are the coals adjust-blended with caking properties and coalification degree for coke production, whereas LV coals and HV coals are non-coking coals having no (or low) caking properties and are used in the high-temperature dry distillation furnace.

[0091]Note that although the high-temperature dry distillation furnace is equipment for dry distilling Coals at a maximum temperature of 900°C or higher, the calculation in the example assumed equipment (including gas purification equipment) that dry distillates at a temperature equivalent to that of a conventional coke oven. Furthermore, the premise is that the whole amount of COG generated from the coke oven and the high-temperature dry distillation furnace is used for the purpose of a r...

TECHNICAL FIELD

[0001] The present invention relates to a method for preprocessing raw materials for blast furnace processes including sintering machines and dry distillation furnaces. In particular, it relates to the preprocessing and handling of raw materials for the blast furnace process, and relates to the expanding raw material options and CO 2 reduction.BACKGROUND ART

[0002] In a blast furnace process, coke and iron ore are charged from the furnace top, and hot blast, which is high-temperature air of 1000°C or higher, and pulverized coal or the like as a reducing agent are injected from tuyeres provided in a lower furnace. Accordingly, the pulverized coal and coke are combusted to generate high-temperature reducing gas such as CO and H 2 together with a large amount of heat, which rises in the furnace and heats up and reduces the iron ore descending in the furnace.

[0003] In addition to having low ash content and low sulfur content, BF coke is required to have appropriate porosity and a strength that does not cause pulverization even at high temperatures. For producing coke satisfying such conditions, only limited kinds of bituminous coal are used and are called coke-oven feed coal (application classification name), and they are distinguished from steam coal mainly used as fuel for power generation.

[0004] In a coke oven, the coke-oven feed coal that has been crushed and mixed is charged into a carbonization chamber and indirectly heated at 1,000 to 1,300°C for 14 to 20 hours to be dry distilled, thereby producing coke. At this time, fuel gas (COG), and tar and the likes are obtained as by-products.CITATION LISTPATENT LITERATURE

[0005] Patent Literature 1: International Publication No. 2023 / 190840 Patent Literature 2: Japanese Patent Application Laid-open Publication No. 2000-104075 Patent Literature 3: Japanese Patent Application Laid-open Publication No. Sho 58-160395 NON-PATENT LITERATURE

[0006] Non-Patent Literature 1: Katsuhiko Yamamoto, Shinichi Misawa, Kazuhiko Hizuka, and Ryouhei Mimura, "Experimental study on developing uses of RDF by carbonization", Journal of the Japan Society of Waste Management Experts, The Japan Society of Waste Management Experts, 2000, Vol. 11, No. 4.

[0007] Non-Patent Literature 2: Uwe Essmann, "Biochar-pellets as substitute for fossil coal in metallurgical processes," Master's thesis, Renewable Energy ENE500, University of Agder, 2018.

[0008] Non-Patent Literature 3: The Japan Institute of Energy (ed.), "Biomass Handbook (2nd edition)," The Japan Institute of Energy, 2009.

[0009] Non-Patent Literature 4: Nippon Steel Corporation (then Shin Nippon Seitetsu Kabushiki Kaisha), "Recycling technology of municipal waste plastics by coke-oven chemical feedstock process," The 58th Okochi Memorial Production Prize, Okochi Memorial Foundation, 2011.

[0010] Non-Patent Literature 5: Tatsuya Oki, Junichi Tanaka, and Taneomi Harada, "Factors affecting grindability of coal," Shigen-to-Sozai (Resources and Materials), The Mining and Materials Processing Institute of Japan, 1996, Vol. 112, No. 1, pp. 37-42.

[0011] Non-Patent Literature 6: Takuya Furuzono, Akihiro Hoshino, Tsuyoshi Teramae, Ikuo Hosoya, and Toru Yamashita, "Fundamental study on pulverization characteristics of semi-carbonized pellets," Proceedings of the 54th Coal Science Conference of The Japan Institute of Energy, 2017.

[0012] Non-Patent Literature 7: Kazuhiko Nakaoji, Yoichi Nakamura, and Katsumi Muroi, "Deashing technology of coal by oil agglomeration and its application," Hitachi Review, Hitachi Review, 1984, Vol. 66, No. 2.SUMMARY OF THE INVENTION

[0013] In a blast furnace, which is a metallurgical furnace, pulverized coal (PC) injected from tuyeres is subject to fewer restrictions than coke-oven feed coal, but coal quality is limited. Therefore, coal or coal-alternative solid fuel (Tuyere-injection solid fuel) to be injected from the tuyeres is not injected directly from the tuyeres. But it is characterized to be separated into solid, liquid and gas in a high-temperature dry distillation furnace such as a coke oven. Then, the solid fraction (char) is injected from blast furnace tuyeres, the gaseous fraction (COG) is reformed into a high-temperature reducing gas to be blown into the blast furnace, and a combustible fraction (tar and the likes) among the liquid is injected from blast furnace tuyeres. By this, "reduction in decomposition heat of tuyere-injection solid fuel → increase in effective calorific value of the same fuel → reduction in tuyere-injection solid fuel → reduction in fuel ratio of the blast furnace and combustion-supporting gas (oxygen)" is achieved, and CO 2 emissions can be reduced.

[0014] By the above method, as coal-alternative solid fuels, renewable fuels having very high VM (volatile matter), such as bio-pellets and biochar, and waste-derived solid 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 agents). Here, heavy metals, alkalis and other impurities in wastes are chloride-volatilized in the high-temperature dry distillation furnace by chlorine in the wastes and thus removed from the char, so that there is no hindrance to blast furnace operation as a metallurgical furnace.

[0015] By using renewable fuel and refuse-derived solid fuel, fossil fuel (coal) can be reduced, and therefore costs and energy for CO 2 treatment associated with the reduced amount of fossil fuel (coal) or with the alternative fuel become unnecessary.TECHNICAL PROBLEM

[0016] In the steel industry, since fossil fuels such as coal and natural gas are used as reducing agents and combustion fuels in metallurgical furnaces -blast furnaces, large amounts of CO 2 are emitted and countermeasures for their reduction are expected. For underground storage of CO 2 , stable ground and acquiring local consensus are issues. And economic hurdles including the infrastructure are high for CO 2 reuse (C-recycling) and / or H 2 reduction because large amounts of H 2 and green power are required. The inventor of the present application has devised, as Patent Literature 1, a CO 2 reduction measure for blast furnaces that has not been available before, but even then, there is further room for reduction in the amount of CO 2 emissions when C-recycling and / or underground storage are not taken into account. Also, according to this invention, the coke rate (CR) can be reduced to 1 / 5 or less of that in the conventional method. But when coke is reduced, coke breeze, which is a by-product of coke, is also reduced similarly. Since coke breeze is used as a sintering fuel for a sintering machine, it is necessary to compensate for a shortage of coke breeze with anthracite. But there used to be a concern that the VM (volatile matter) in anthracite cannot be well utilized as heat source, but generates tar to bring about various problems.

[0017] Further, according to Patent Literature 1, as blast furnace tuyere injection fuels, it is preferable that materials have higher primary combustion heat (reaction of C + 0.5 × O 2 = CO) and have smaller thermal decomposition heat (amount of heat to decompose according to C i H j O k = i × C + 0.5 j × H 2 + 0.5 k × O 2 ) required before combustion, and it is desirable that VM be small. At PCI (pulverized coal injection) facilities in conventional blast furnace, LV coal (low-VM coal) has recently tended to be used for that reason. Also, tuyere injection of biochar is being studied worldwide as a CO 2 reduction countermeasure, because the VM of biofuel is very high. And the idea is to carbonize it (dry distillation at 400-700°C) at a collection site in order to inject into the furnace the ones whose VM are reduced- with calorific value increased - as that of anthracite to MV coal (medium-VM coal). However, when biomass is subjected to carbonization, the yield of carbonized material (char) is about 20%, and gas, tar and the likes are hardly effectively utilized except for heat required for the carbonization, which leads to a problem that energy efficiency is low.

[0018] On the other hand, greenhouse gas emissions associated with waste incineration in Japan amount to about 40 million tons, accounting for 3% of Japan's total emissions and corresponding to about 40% of emissions from the steel industry.

[0019] With respect to municipal-solid-waste incineration plants, there are an increasing number of cases in which power generation facilities are installed in order to make effective use of waste heat. However, issues of incineration residues caused by chlorine, alkalis, heavy metals and the like in wastes remain. And the power generation efficiency is as low as about 15% on a national average due to the corrosion problems of boiler walls. The energy efficiency including self-consumption of electricity in the plant is even lower. Furthermore, from the viewpoint of reducing CO 2 emissions, power generation within incinerators or with RDF / RPF / etc. does not reduce CO 2 emissions but only provides a possibility to reduce fossil fuels in thermal power plants by the amount corresponding to the increase in generated power, which is a thermal recycling. Biomass power generation or renewable fuel power generation also falls within the category of thermal recycling. And it is important to rationally realize material recycling and / or chemical recycling in order to get substantial CO 2 reduction.TECHNICAL SOLUTION

[0020] In the raw material preprocessing method according to the present invention, coals and / or coal-alternative solid fuels outside the range for coke production are subjected to dry distillation under conditions in which the maximum dry distillation temperature becomes 900°C or higher. And combustibles generated through the dry distillation are separated into solid fuel, liquid fuel and / or gaseous fuel. Then, all or part of the solid fuel, liquid fuel or gaseous fuel is blown into metallurgical furnaces including blast furnaces.EFFECT OF THE INVENTION

[0021] By the above raw material preprocessing method, coals and / or coal-alternative fuels (hereinafter collectively referred to as "Coals"), which are tuyere-injection solid fuels, can be changed to char (C + ash) having almost no volatile matter (VM) within a high-temperature dry distillation furnace in which the maximum temperature becomes 900°Cor higher. Whereby, the decomposition heat of tuyere-injection solid fuel is eliminated and the heating value becomes higher, compared with directly injecting Coals from blast furnace tuyeres. Therefore, to produce 1 t of pig iron, it can reduce a tuyere-injection solid fuel rate (kg / tp) and an oxygen rate (Nm 3< / tp) as combustion-supporting gas. Moreover, this makes it possible to use high-VM fuels such as HV coals, biomass solid fuels and / or waste-derived solid fuels as reducing agents for blast furnaces. Here, heavy metals, alkalis and other impurities in wastes are chloride-volatilized in the high-temperature dry distillation furnace by chlorine in the wastes and thus removed from the char, so that there is no hindrance to blast furnace operation.

[0022] Compared to directly injecting coals into blast furnaces, the above raw material preprocessing method increases the amount of gas (hereinafter referred to as COG; coke oven gas) generated in the coke oven and / or high-temperature dry distillation furnace (hereinafter also referred to as "High-temperature dry distillation furnaces"). COG mainly contains hydrogen but also components such as CH 4 and CO 2 . Converting it into H 2 and / or CO, heating it, and then blowing it into the blast furnace promotes gas-based ore reduction and enables the reduction of other fuels.

[0023] Compared to directly injecting coals into blast furnaces, the above raw material preprocessing method increases the amount of combustible liquid (meaning tar, crude light oil and the likes; hereinafter collectively referred to as "Tar") generated in High-temperature dry distillation furnaces. Although Tar can be used as combustion fuel for ironmaking facilities (hot stoves, coke ovens and sintering machines), it is preferable to use Tar as tuyere-injection reducing agent. Furthermore, the best way is to utilize it as oil for COM (Coal Oil Mixture) - a means to transport and inject BF-tuyere-injection solid fuel-, where Tar serves both as a transport medium and as tuyere-injection fuel.

[0024] The char produced by the above raw material preprocessing method can also be used as a sintering fuel for sintering machines, which can solve problems when anthracite is used as the sintering fuel. In addition, producing char as a sintering fuel increases the amounts of COG and Tar produced as by-products in high-temperature dry distillation furnaces. They can be used as reducing agents for blast furnaces so that the fuel rate (reducing agent rate) of the blast furnace can be reduced and Tar can be used as the oil when COM is used.

[0025] Thus, regardless of whether coals have caking property or not, by preprocessing coals in high-temperature dry distillation furnaces to pyrolyze them and to take out fuels in three phases-solid, liquid and gas- and by using these fuels appropriately according to each phase, it is possible to reduce the amount of fossil fuels used in ironmaking facilities as a whole including blast furnaces, sintering machines and coke ovens.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] [FIG. 1] FIG. 1 is an overall flow diagram according to an embodiment of the present invention, in which char is supplied to a blast furnace from tuyeres at the lower furnace. [FIG. 2] FIG. 2 is an overall flow diagram of reducing agents and sintering fuels before application of the present embodiment. [FIG. 3] FIG. 3 is a flow diagram in which the present embodiment is applied only to a blast-furnace tuyere-injection line in FIG. 2. [FIG. 4] FIG. 4 is a flow diagram in which, in addition to FIG. 3, the present embodiment is also applied to a sintering fuel for sintering machines. [FIG. 5] FIG. 5 is a diagram comparing a conventional PCI method with a carbonaceous-material preprocessing flow according to the present embodiment. [FIG. 6] FIG. 6 is a nitrogen / chlorine balance diagram according to a mixing ratio of coals and chlorine-containing fuels. [FIG. 7] FIG. 7 is an overall flow diagram according to an embodiment of the present invention, in which char is supplied to a blast furnace from both a furnace top and tuyeres at the lower furnace. [FIG. 8] FIG. 8 shows an unreacted-core model in a case where waste containing chlorine is formed into spherical briquettes. [FIG. 9] FIG. 9 is Table 1 showing components of the RDF in Non-Patent Literature 1. [FIG. 10] FIG. 10 is Table 2 showing proximate analysis values, ultimate analysis values and LCVs of coke-oven feed coals, LV coal and HV coal, respectively. [FIG. 11] FIG. 11 is Table 3 showing a comparison of estimated carbon intensity between a case using LV coal in FIG. 2 and cases using LV coal or HV coal in FIG. 3 in which the present embodiment is applied to a blast-furnace tuyere-injection line. [FIG. 12] FIG. 12 is Table 4 showing cases using LV coal or HV coal in FIG. 4 in which the present embodiment is also applied to a sintering fuel for a sintering machine. [FIG. 13] FIG. 13 is Table 5 showing cases using LV coal or HV coal in FIG. 1 which is a model case of the present embodiment. [FIG. 14] FIG. 14 is Table 6 showing a comparison of carbon intensity between the case of FIG. 1 and the case of FIG. 7 where HV coal in Table 2 (FIG. 10) is used. DESCRIPTION OF EMBODIMENTS

[0027] Several exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. It should be noted that the drawings illustrate representative facilities related to the present embodiment, but do not show detailed information including auxiliary equipment and combustion fuels.

[0028] Although each term is used in the following description and the appended claims in a sense consistent with definitions well known to those skilled in the art, we caution that certain terms have the following meanings. "The lower furnace" means the area of and below the cohesive zone, including a region in which permeability deteriorates due to softening of the ore (at temperatures of 1200-1300°C or higher, depending on the reduction degree of the ore). "Partial combustion" means combustion that is not a complete combustion. "Primary combustion" refers to the reaction of C + 0.5·O 2 = CO, as well as the partial combustion that produces CO, H 2 and H 2 S from coke and / or tuyere injection fuels. The heat generated by this is called "primary combustion heat." "Fuel rate" or "reducing agent rate" means a total weight (kg / tp) of coke and tuyere-injection fuels (also referred to as tuyere-injection reducing agents) required to produce 1 t of pig iron. These terms are in principle synonymous, but "reducing agent rate" is often used in order to distinguish from combustion fuels and which term is used depends on the context. In the present description, unless otherwise specified, the fuel rate does not include a reducing gas (CO, H 2 ) blown in from tuyeres by means of top-gas recycling or the like. "Low-temperature dry distillation," "medium-temperature dry distillation" and "high-temperature dry distillation" are expressions that classify relatively slow pyrolysis methods in accordance with pyrolysis temperature. Although detailed definitions thereof are not established even among those skilled in the art, in the present description low-temperature dry distillation is taken as a temperature range for semi-carbonization (torrefaction), medium-temperature dry distillation as a temperature range for producing typical biochar (VM = about 5-25%), and high-temperature dry distillation as a temperature range for producing coke or biocoke (residual VM of a few percent), namely 200-300°C, 400-700°C and 900-1300°C, respectively.

[0029] A pulverized coal injection (PCI) for a blast furnace is a method to inject pulverized coals into the blast furnace from tuyeres. It aims to substitute inexpensive non-coking coals for expensive and precious coke (referring to lump coke charged from the blast furnace top), and utilizes the pulverized coals (VM = 10-40%) in order to increase combustion efficiency. Therefore, even if there may be some rationale for pulverizing anthracite or coke breeze (yield loss of lump coke) for use in PCI under special circumstances, there is apparently no rationale for pulverizing lump coke (the main product of a coke oven) and injecting it from tuyeres.

[0030] The operation method disclosed below has been conceived contrary to such common technical knowledge of those skilled in the art. In general terms, it is a method in which, instead of directly injecting coals through blast furnace tuyeres, carbonized material deliberately obtained from high-temperature dry distillation, together with gaseous and liquid fuels that are produced as by-products in gas-purification equipment (auxiliary equipment for high-temperature dry distillation furnaces), is charged into the furnace.

[0031] Specifically, first, coals and / or coal-alternative solid fuels outside the production range for blast furnace coke are subjected to dry distillation at temperatures whose maximum reaches 900°C or higher, thereby separating them into a solid fuel as char (C + ash) and a crude gas consisting of the remainder. Next, the crude gas is separated by gas-purification equipment into a gaseous fuel as COG, a liquid fuel as Tar, and a remaining liquid mainly composed of water (corresponding to ammoniacal liquor in coal dry distillation and to pyroligneous acid in biomass dry distillation). That is, from the charged raw materials, solid fuel (char), liquid fuel (Tar) and gaseous fuel (COG) are taken out by the above dry distillation and fuel-separation process.

[0032] Then, as for the solid fuel, a part or all thereof is crushed by a crusher to obtain coarse-crushed char, which is used as a sintering fuel for sinter, and all or part of the solid fuel that is pulverized so that 70% or more of particles have a particle size of 0.1 mm or less is injected into the blast furnace through tuyeres at the lower furnace. As for the gaseous fuel, a part or all thereof is converted (reformed) to synthesis gas (reducing gas) mainly containing CO and H 2 and then is blown into the blast furnace at a temperature of 800°C or higher. As for the liquid fuel, all or part thereof is injected into the blast furnace through tuyeres at the lower furnace.

[0033] The present embodiment will be described in further detail below.

[0034] In blast furnaces, top-charging coke (lump coke) has its most important role in maintaining gas and liquid permeability in the lower furnace, and therefore it is required to have high-temperature strength, a sufficient particle size, and low reactivity. Accordingly, coke-oven feed coals whose caking properties and VM, etc. are adjusted in advance are subjected to dry distillation in coke ovens at 1000-1300°C, and finally only lump coke having a required particle size is charged into the blast furnace. Lump coke also has roles as a reducing agent (for direct reduction and gas-based reduction) and as a heat source (a source of thermal energy through combustion), and therefore the amount of top-charging coke has conventionally been far greater than the amount required only to ensure gas and liquid permeability in the lower furnace.

[0035] On the other hand, the PCI is a technique that allows inexpensive non-coking coals to share the roles of coke as a reducing agent and as a heat source. In order to increase the combustion efficiency, coals are pulverized so that particles of 200 mesh (74 µm) or less account for 70-80% or more, thereby increasing the specific surface area. Coal kinds from HV coal (high-VM coal) to LV coal (low-VM coal) have been studied, and the focus has shifted from HV coal, which emphasizes combustion efficiency, to LV coal having a higher heating value as the PC rate increases. In recent years, as a CO 2 reduction measure, research has been conducted worldwide on mixing biomass-derived carbonized material into PC, but such research remains on an extension of conventional PCI technology.

[0036] The present inventor has devised a method for reducing CO 2 in blast furnace processes (Patent Literature 1). According to the CO 2 reduction method for a blast furnace process described in Patent Literature 1, it is preferable that blast-furnace tuyere-injection fuels should have high primary combustion heat and small thermal decomposition heat (the amount of heat required to decompose: C i H j O k = i×C + 0.5j×H 2 + 0.5k×O 2 ). The thermal decomposition heat of coal means the thermal decomposition heat of its VM (volatile matter), and therefore LV coal is preferable as a blast-furnace tuyere-injection fuel. This is also a common issue in conventional PCI methods.

[0037] To address the challenges of using HV coal, instead of directly supplying Coals with VM ≥ 6% to the lower furnace, the present invention devises a method that those Coals are carbonized into solid fuel (char) having VM < 5% (preferably ≤ 1%) in a high-temperature dry distillation furnace where the maximum temperature reaches 900°C or higher. Then, the solid fuel (char), gaseous fuel (COG), and liquid fuel (Tar) by-produced in gas purification equipment attached to the high-temperature dry distillation furnace, are supplied to the blast furnace by means optimal for each fuel.

[0038] Here, a high-temperature dry distillation furnace is equipment having a structure that prevents ingress of outside air, can secure a maximum dry distillation temperature of 900°C or higher, and is equipped with gas-purification equipment, and from a logistics viewpoint it is preferably installed near blast furnaces. There is no restriction on its type, and equipment such as a vertical coke oven may be used, and many existing coke ovens, including CDQ (coke dry quenching) facilities, can be diverted. In producing coke and char, it is necessary to separate their dry distillation furnaces and cooling equipment, but the gas-purification equipment may be shared. The reason why the dry distillation temperature is defined as 900°C or higher is that there is a correlation between the dry distillation temperature of coal and gasification (pyrolysis), and the gasification, including H 2 , is completed at around 900°C.

[0039] FIG. 5 compares the conventional PCI method with the present embodiment.

[0040] In the conventional PCI method, as a CO 2 reduction measure utilizing biomass, attempts have been made to mix biochar-also referred to as charcoal for woody biomass-, having VM of about 6-25% with coal. Because biomass has such properties as low bulk density, high moisture content and low yield of carbonized material, it is generally carbonized at a biomass collection site in a medium-temperature dry distillation furnace 14 at 400-600°C and then transported and delivered to the user, i.e. a steelworks. In addition, since coal contains moisture, it is first dried by a dryer 13 so that its moisture content becomes 1% or less, then finely pulverized by a pulverizer 7, and thereafter injected into the blast furnace 1 as PCI through tuyeres (not shown).

[0041] In the present embodiment, Coals brought into the steelworks are first separated in a high-temperature dry distillation furnace 2 into a solid fuel as char, a liquid fuel as Tar, a gaseous fuel as COG, and a remaining liquid mainly composed of water (corresponding to ammoniacal liquor in coal dry distillation and to pyroligneous acid in biomass dry distillation), and then only the fuels excluding the remaining liquid are supplied to the blast furnace 1. As for the char, a part or all thereof is, as required, finely pulverized by a pulverizer 7 so that 70% or more of particles have a particle size of 0.1 mm or less, and is injected into the blast furnace through tuyeres at the lower furnace. As for COG, a part or all thereof is converted in a reforming and heating furnace (hot stoves) 5, using partial combustion and / or agent gases (H 2 O and CO 2 ), into reducing gas (synthesis gas) mainly containing CO and H 2 , which is blown into the blast furnace 1. As for Tar, a part or all thereof is injected into the blast furnace through tuyeres at the lower furnace. It is preferable that the solid fuel (char) be finely pulverized by the existing pulverizer for blast-furnace injection 7.

[0042] VM in coals is separated in advance and char is injected from blast furnace tuyeres, which eliminates the endothermic reactions due to pyrolysis of coal (including the heat for heating and pyrolysis of the remaining liquid removed in the high-temperature dry distillation furnace 2) and increases the heating value (kJ / kg). Accordingly, the fuel rate (kg / tp) and oxygen rate (Nm 3< / tp) for 1 t of pig iron can be reduced.

[0043] Char is finely pulverized by a pulverizer 7 to increase its specific surface area (proportional to combustion efficiency) and is injected from dedicated injection lances provided in tuyeres at the lower furnace. The pulverizability index HGI (Hardgrove Grindability Index; a higher value means easier grinding) increases with dry distillation temperature and degree of carbonization (Non-Patent Literatures 5 and 6). Therefore, even HV coal, biomass-based fuels, and the like can be more easily pulverized by carbonization, which can reduce pulverizing energy.

[0044] COG is recovered at room temperature. Accordingly, if it is injected into the blast furnace as a reducing gas without being preheated to a temperature equal to or higher than that of the injection site, it becomes a cold source and cools the burdens inside the furnace, which is undesirable. Even when injecting into the shaft section, it is desirable to heat the gas to 800°C or higher. However, the gas contains hydrocarbon gases such as CH 4 , and heating it to 800°C or higher generates soot due to cracking phenomena (CH 4 = C+2H 2 ). Therefore, it is desirable to reform the hydrocarbons into a reducing gas (synthesis gas) mainly composed of CO and H 2 in a high-temperature atmosphere using partial combustion (C n H m +0.5n·O 2 =n·CO+0.5m·H 2 ) or agent gases (H 2 O, CO 2 ) before injecting the gas into the blast furnace. By injecting the reducing gas at an appropriate temperature into an appropriate location, the gas-based reduction ratio increases and the fuel rate (reducing agent rate) can be reduced (Patent Literature 1).

[0045] As for Tar, it is utilized as a reducing agent for chemical recycling by injecting it into the furnace from tuyeres, in the same manner as the conventional heavy oil injection method. It is desirable to inject it from the tuyeres at the lower furnace using a dedicated injection lance similar to an injection lance for heavy oil.

[0046] The effects of the above embodiment will be described also in light of the outside of the "steelworks boundary" shown in FIG. 5. In a conventional PCI route, biochar is generally produced in a medium-temperature dry distillation furnace 11 installed at a biomass collection site. Since the yield and VM of biochar are inversely correlated with the dry distillation temperature, the yield of low-VM biochar suitable for PCI is as low as 20 to 30%. Furthermore, by-product gas, tar, and the likes are difficult to utilize effectively for purposes other than combustion heat for the dry distillation furnace. Consequently, the net energy yield of the dry distillation furnace (= latent heat of recovered fuels / (latent heat of feed raw materials + external heat input)) becomes low.

[0047] In the present embodiment, the high-temperature dry distillation furnace 2 is installed within the steelworks, and COG & Tar derived from VM can be utilized within the steelworks; therefore, the feed raw materials have no problem to be high-VM fuels. Accordingly, biomass collection sites can adopt fuel conversion facilities prioritizing energy yield, such as low-temperature dry distillation furnaces (torrefaction furnace) 15 operating at 200 to 300°C or solidification equipment 16 operating below 200°C.

[0048] FIG. 2 (an example where the present embodiment is not applied; Patent Literature 1) and FIG. 3 (an example where the present embodiment is applied) summarize the flows within the steelworks boundary of FIG. 5 into ironmaking process flows that include the coke oven 3 and the sintering machine 9. In both examples, gas reforming is assumed to be a partial combustion method using oxygen in a hot stove (reforming / heating furnace) 5. The flow is configured to circulate and utilize the top gas from which CO 2 has been removed by a CO 2 separator 4, depending on the amount of reducing gas required in the blast furnace 1. At the same time, the flow allows for adjusting the amount of reducing gas produced and heated in the hot stove 5 by supplying CH 4 from the external source. In addition, both examples adopt a flow in which anthracite is used to compensate for any shortage of coke breeze used as a sintering fuel for sinter produced in the sintering machine 9. Note that although a screen is indicated in the flows, it is used in the broad sense of a classification device 10; it may be a literal screen (sieve) type, or a system such as air classification or a fluidized bed (this also applies to other figures).

[0049] The amount of sintering fuel used per 1 t of pig iron is calculated as OR×SR×C str , based on ore rate: OR (kg / tp; amount of charged ore per 1 t of pig iron), sinter ratio: SR (%; ratio of sinter in charged ore), and sintering fuel rate: C str , (kg / ts; amount of sintering fuel per 1 t of sinter). On the other hand, the supply amount of coke breeze is calculated as CR × R fc / R cc , based on coke rate: CR (kg / tp; amount of coke per 1 t of pig iron), lump coke ratio: R cc (%; weight yield of lump coke relative to coke-oven feed coals), and coke breeze ratio: R fc (%; weight yield of coke breeze relative to coke-oven feed coals). Therefore, the shortage of sintering fuel (coke breeze) per 1 t of pig iron: L c (kg / tp) is given by: L c =OR×SR×C str -CR×R fc / R cc (1) and the shortage is generally covered by anthracite.

[0050] It is obvious that the shortage increases if the first term on the right-hand side of Equation (1) increases or the second term decreases (and vice versa). Since self-fluxing sinter (sinter including auxiliary raw materials for adjusting slag basicity) has high reactivity in the blast furnace, SR (proportional to the first term) is on an increasing trend in conjunction with the situation where high-quality lump ore is becoming depleted. Also, CR (proportional to the second term) is decreasing due to the trend of the PC rate increase and CO 2 reduction. These strengthen the tendency of sintering fuel (coke breeze) shortage. According to the method of Patent Literature 1, CR can be reduced to 1 / 5 or less of that in the conventional blast furnace process, so the shortage of coke breeze will become decisive.

[0051] On the other hand, the use of anthracite in sintering machines has long posed issues, and its usage has been limited. Another feature of the present embodiment is that "instead of compensating for the shortage of sintering fuel with anthracite, it is compensated with char produced by high-temperature dry distillation (carbonization) of Coals," and at the same time, "liquid fuel (Tar) and gaseous fuel (COG) by-produced in the dry distillation are recovered; regarding COG, it is reformed into reducing gas (synthesis gas) primarily composed of CO and H 2 using partial combustion or agent gases (H 2 O, CO 2 ) and then injected into the blast furnace body; and regarding Tar, it is injected into the furnace from the tuyeres at the lower furnace."

[0052] The raw materials (coals, coal-alternative fuels, etc.), equipment (high-temperature dry distillation furnace, gas purification equipment, etc.), and operation methods (dry distillation temperature, dry distillation time, etc.) for this purpose can be made common to and shared with those for the production of char for blast furnace injection. Therefore, another feature is that its facility efficiency and operation efficiency can be synergistically improved. The integrated ironmaking process flow is shown in FIG. 4.

[0053] In FIG. 4, "Anthracite" and "LV coal" in FIG. 3 are integrated into "non-coking coals / coal-alternative fuels", and the entire amount thereof is processed in the high-temperature dry distillation furnace 2. A part of the carbonized solid fuel (char) is utilized as coarse-crushed char for a sintering fuel for sinter, and the rest is injected into the blast furnace as pulverized char.

[0054] The supply destinations of the liquid fuel (Tar) and gaseous fuel (COG) by-produced in the high-temperature dry distillation furnace 2 in FIG. 4 are the same as in FIG. 3; however, their supply amounts have increased by an amount corresponding to the production of the sintering fuel for sinter used in the sintering machine 9, which is added to the high-temperature dry distillation furnace 2. In other words, conventionally, even if anthracite was used as a sintering fuel, its VM latent heat could hardly be effectively utilized; however, in the present embodiment, it can be effectively recovered and utilized as liquid fuel and gaseous fuel.

[0055] The combustion time of a sintering fuel is roughly proportional to the square of the particle size. Since this combustion time is a factor determining the combustion pattern (combustion temperature and retention time in the sintering bed) which affects sinter quality and yield, a narrower particle size range is desirable. Therefore, for example, it is desirable to control the particle size range to about 2 to 3 mm. However, it is difficult to finely classify wet materials (sieves are prone to clogging), and conventionally, even when coke breeze was used, particles smaller than 1 mm or more than 5 mm were included in no small amounts. The char discharged from the high-temperature dry distillation furnace is dry-cooled to about 150°C in a CDQ (Coke Dry Quenching) facility (not shown) for the purpose of sensible heat recovery, similar to ordinary coke, and is then coarsely crushed. Since it is completely dry, screening and air classification are easy. Furthermore, an undersize fraction of, for example, less than 2 mm does not result in yield loss because it can be supplied to the pulverizer 7 for blast furnace injection; therefore, the particle size range sent to the sintering machine 9 can be controlled within a narrow range. Although the detailed particle size range is determined by the relationship with the exhaust gas suction speed of the sintering machine, FFS (Flame Front Speed), and the like, it is desirable to use coarse particles having a particle size of 1 mm or more and 6 mm or less as the sintering fuel for sinter.

[0056] Particle size control of the sintering fuel is also effective for coke breeze. Therefore, in FIG. 4, a line for charging coke breeze of, for example, less than 3 mm or more than 5 mm into the high-temperature dry distillation furnace 2 is indicated by an asterisk (), parallel to the line supplying the mixer 8.

[0057] As for the method of injecting pulverized char into the furnace in FIGS. 3 and 4, pneumatic transport is assumed, similar to the conventional PCI method. Since pulverized char produced by high-temperature dry distillation has almost no VM, the risk of coal dust explosion is low even with air transport. However, in the case of air transport or nitrogen transport, N 2 enters the furnace. Considering consistency with CO 2 separation (N 2 separation is difficult) and the top gas recycling system (N 2 tends to concentrate), it is desirable to use a reducing gas (such as top gas after decarbonation) as the carrier gas. Since the system is a pressurized system for injecting into the pressurized blast furnace, external air is unlikely to intrude into the injection system, which enables the use of preheated carrier gas. By increasing the sensible heat of the injected char and gas, the fuel rate and oxygen rate can be reduced. As a means to increase the injection sensible heat, a method to indirectly heat the transport piping from the outside of the pneumatic system using an electric heater, steam, or the like can also be applied.

[0058] Methods other than the pneumatic transport can also be applied to the blast furnace tuyere injection of pulverized char. When injecting liquid fuel (Tar) simultaneously, it is most rational to utilize COM (Coal Oil Mixture) and its process flow is shown in FIG. 1.

[0059] The COM 12 is equipment that slurries pulverized solid fuel using oils such as heavy oil or Tar as a transport medium and transports it. In FIG. 1, pulverized char and liquid fuel such as Tar are mixed in advance and injected into the blast furnace as COM fuel. Since the practical upper limit of the slurry concentration (ratio of solids in the total transport weight) is generally about 50%, when the coke-oven feed coals are bituminous coals, auxiliary liquid fuel (reducing agent) such as heavy oil is supplemented to prevent the slurry concentration from becoming excessively high. Note that since the pulverized char can be reduced corresponding to the supplemented amount of heavy oil or the like, the overall energy efficiency and CO 2 emissions do not deteriorate.

[0060] By the way, the yield (ratio of recovered materials to the weight of feed materials such as Coals) of solid fuel and liquid fuel in the high-temperature dry distillation furnace varies depending on the feed material such as Coals and its VM. Generally, as VM increases, the yield of solid fuel decreases and the yield of liquid fuel increases. When woody biomass fuel is subjected to dry distillation at 1000°C, the yields are roughly about 20% solid, 55% liquid, and 25% gas (Non-Patent Literature 2). Subtracting the yield of about 30% for pyroligneous acid (Non-Patent Literature 3), which cannot be used as fuel, from the 55% liquid, the ratio becomes solid fuel : liquid fuel : gaseous fuel = 20% : 25% : 25%, resulting in a slurry concentration of about 44% (< 50%). When waste plastics are subjected to high-temperature dry distillation, the ratio becomes solid fuel : liquid fuel : gaseous fuel = 1 : 2 : 2 (Non-Patent Literature 4), so the slurry concentration is about 33% (< 50%). That is, depending on the selection of the type of coal-alternative fuel and the mixing ratio, auxiliary liquid fuel such as heavy oil becomes unnecessary. Even when coal-alternative fuels are not used, CO 2 -free auxiliary liquid fuels such as biomass tar or e-fuels can be used instead of heavy oil.

[0061] By applying COM, the two control systems-the pneumatic transport system and the liquid injection system-can be integrated into one, and the tuyere injection lances can also be integrated. Furthermore, the heat of vaporization of the liquid can be utilized to protect the lance from the harsh temperatures inside the furnace. Also, while the transport temperature of heavy-oil-based COM is usually less than 100°C, it is easy to indirectly heat it to near the boiling point of the liquid fuel (e.g., 200°C, as both heavy oil and Tar have a wide range of boiling points) before injection through the tuyeres. This increases the sensible heat of the solid fuel and liquid fuel, which makes it possible to reduce the fuel rate (kg / tp) and the oxygen rate (Nm 3< / tp). In addition, since vaporization of the liquid fuel is promoted by the heating, the COM combustion efficiency also improves.

[0062] While the features centering on the process of the present embodiment have been described above, options for coal-alternative fuels in the present embodiment and their features will be described next.

[0063] In the present embodiment, as coal-alternative fuels, biomass fuels (including semi-carbonized fuels) are certainly suitable, but in addition, waste-derived solid fuels (RDF, RPF, etc.) containing a certain amount of impurities can also be used. When utilizing wastes, impurities and incombustibles contained within the wastes pose challenges. And the importance of pre-sorting and preprocessing is the same as in other methods to utilize solid-waste fuels; however, the present embodiment facilitates easier utilization of wastes than other methods for the following reasons.

[0064] First, the method of incinerating wastes to generate steam power has problems: chlorides in the wastes corrode metal walls, including boiler walls, and generate large amounts of dioxins. This is the cause of the low power generation efficiency in incinerators. Even when using RDF with chlorine concentrations managed below approximately 1%, it still leads to increased countermeasure burdens and feeding rate constraints. This undermines the cost advantage (economic viability) of waste-to-energy power generation and acts as a factor hindering its widespread adoption.

[0065] Next, although similar to the present embodiment, there is a method of chemical recycling by mixing waste plastics with coke-oven feed coals and charging the mixture into a coke oven (Patent Literature 2, Non-Patent Literature 4). The advantage of this method is that, under the high-temperature reducing atmosphere of the coke oven, more than 90% of the chlorine contained in the waste plastics transfers into the gas as HCl. When cooled with ammoniacal liquor containing ammonia generated from nitrogen derived from coke-oven feed coals, it turns into ammonium chloride (NH 4 Cl) and is rendered harmless. However, despite being able to neutralize 5.3 kg / t-coal (150 mol / t-coal) of chlorine per ton of feed coals, charging only 1 to 2 wt% of waste plastics (about 0.2 to 0.4 kg / t-coal in chlorine content) causes the coke strength to begin to decrease due to reasons other than chlorine; thus, there was a drawback that the effective charging ratio of waste plastics is limited to a few wt%. Moreover, this method focuses exclusively on waste plastics as a coal-alternative fuel, excluding biomass fuels and other types of wastes than waste plastics.

[0066] In the present embodiment, the use of a high-temperature dry distillation furnace is the same as in Patent Literature 2, and the ability to render the chlorine in the feed materials harmless is the same. However, since coarse-crushed char or pulverized char is produced instead of coke, there are no feed-material constraints required for coke strength. Therefore, the waste plastic charging ratio can be increased up to the balance limit with ammonia derived from coals (5.3 kg-Cl / t for coke-oven feed coals). According to Patent Literature 2, it is possible to increase the proportion of waste plastics containing 2 wt% chlorine up to 26 wt% relative to coke-oven feed coals. Since N and Cl in the coals and N in the waste plastics are 0.045 wt%, 1.59 wt%, and 0.4 wt%, respectively, the weight ratio (N / Cl) of nitrogen (N) to chlorine (Cl) in the feed materials for the high-temperature dry distillation furnace is determined to be 3.0. Here, suppose that the waste plastics are replaced with RDF-e.g., RDF in Non-Patent Literature 1 containing the components shown in Table 1 of FIG. 9-while using the same coals. Then, although the chlorine content is relatively high (> 1 wt%) as shown in Table 1, a maximum of 37 wt% of RDF can be charged for the N / Cl ratio to become 3.0. Note that the RDF carbonized material in Table 1 (FIG. 9) is obtained by dry distilling RDF at 500°C.

[0067] The above charging constraints are intended to neutralize hydrogen chloride generated from chlorine in the feed materials using ammonia generated from nitrogen in the same feed materials. However, in the present embodiment, the charging proportion of RDF can be further increased by effectively utilizing chlorine within the furnace before neutralizing it. Before explaining this point, impurities in wastes will be described in relation to it.

[0068] RDF, which is a solid fuel derived from municipal solid waste, has a quality issue that it contains impurities such as heavy metals and alkalis in addition to chlorine. When using RDF as fuel for thermal power generation, it causes problems similar to chlorine, such as deposits and material corrosion on boiler walls, increasing treatment costs for flue gas and fly ash.

[0069] When using RDF as a blast furnace tuyere-injection fuel, there are issues of RDF properties (proximate analysis values; FC, VM, Ash, moisture content) in addition to issues of RDF quality affecting pig iron quality and blast furnace operation. For example, the RDF in FIG. 9 (Table 1) (Non-Patent Literature 1) has excessively high VM content, and its decomposition heat cools the lower furnace, making it unusable as a blast furnace tuyere-injection fuel. The RDF char in FIG. 9 (Table 1) is obtained by dry distilling RDF at 500°C (Non-Patent Literature 1); however, due to its low carbonization yield (approximately 30%), the ash content of the carbonized material is concentrated / increased to 43.3% dry, making it unsuitable as a tuyere-injection fuel.

[0070] By the way, it is well known that if chlorine is contained in the feed materials charged into a high-temperature dry distillation furnace, chlorine (Cl 2 ) and hydrogen chloride (HCl) are generated due to thermal decomposition. It is also well known that high-temperature chlorine-based gas chlorinates many oxides and metals to produce chlorides with high vapor pressure. This process, known as the chlorination roasting method (chloride volatilization method), has been utilized for heavy metal recovery and other applications.

[0071] In the present embodiment, concurrently with dry distillation, quality improvement and deashing of the carbonized material (char) are achieved by chloride-volatilizing heavy metals, alkalis, and the like in the ash-where the reduction-chlorination roasting of the feed materials is performed by actively utilizing the high-temperature reducing atmosphere in the high-temperature dry distillation furnace and the chlorine introduced from feed materials such as waste.

[0072] The chlorination reaction of an oxide of a metal element M is expressed by the following equation: MO a + b × Cl 2 = MCl 2 b + a / 2 × O 2 ΔG 0 0 < 0

[0073] Although the standard free energy change (ΔG 0< ), which is a function of temperature, must satisfy ΔG 0< < 0 for the reaction to proceed, the chlorination reaction tends to become ΔG 0< < 0. Regarding chloride volatilization, its application has been investigated for treating heavy metals in incineration ash of municipal solid waste. However, since these investigations assumed an oxidizing atmosphere, it was considered that the volatilizable heavy metals were limited. Meanwhile, since the inside of a high-temperature dry distillation furnace has an atmosphere where CO and H 2 gases are generated and carbonized material (C) is produced, the following reactions proceed concurrently. C + 1 / 2 × O 2 = CO ΔG 0 C < 0 CO + 1 / 2 × O 2 = CO 2 ΔG 0 CO < 0 H 2 + 1 / 2 × O 2 = H 2 O ΔG 0 H 2 < 0

[0074] Multiplying equations (3), (4), and (5) by a and adding them to equation (2) yields: MO a + a × C + b × Cl 2 = MCl 2 b + a × CO ΔG 0 0 + ΔG 0 C MO a + a × CO + b × Cl 2 = MCl 2 b + a × CO 2 ΔG 0 0 + ΔG 0 CO MO a + a × H 2 + b × Cl 2 = MCl 2 b + a × H 2 O ΔG 0 0 + ΔG 0 H 2 In the range of 300 to 1200°C, where -500 < ΔG 0< C , ΔG 0< CO , ΔG 0< H2 < -300 kJ / mol, the free energy change for any of equations (6), (7), and (8) becomes sufficiently lower than that of equation (2); therefore, the reduction-chlorination reaction proceeds readily in terms of free energy. Note that, since chlorine is consumed to react with hydrogen to generate hydrogen chloride (H 2 +Cl 2 = 2HCl), it is important whether the free energy change is lower than the standard free energy change of this reaction.

[0075] Further, for example, in a carbonization chamber of a vertical coke oven, the heating of charged materials proceeds from the furnace wall toward the center. This allows the chlorine-containing gas and the charged materials to contact each other over a wide temperature range. Consequently, the reduction-chlorination reaction proceeds sequentially during the heating process, and chlorides with high vapor pressure volatilize sequentially starting from low temperatures. Finally (by the completion of dry distillation at 900°C or higher), diverse oxides can be reduced and chloride-volatilized. Note that, since the temperature generating chlorine gas is lower than the chloride volatilization reaction temperature, depending on the width from the furnace wall to the center of the coke oven, the generated chlorine gas may flow upward through charged materials at low temperatures. This poses a possibility that the efficiency of the chloride volatilization reaction (reaction efficiency) drastically decreases. However, the chloride volatilization reaction efficiency can be enhanced by a raw material preprocessing method, wherein all or part of the chlorine-containing feed materials are molded in advance (into briquettes, injection-molded products, etc.) and then charged into the high-temperature dry distillation furnace (such as a coke oven).

[0076] FIG. 8 shows an unreacted-core model assuming a spherical briquette. In the heating process after charging, a temperature gradient occurs in the thickness direction (radial direction) inside the briquette. Chlorine gas generated in the low-temperature region inside the briquette (chlorine gas generation front in FIG. 8; radius R1) passes through the chloride volatilization temperature front of impurity A (impurity A reaction front in FIG. 8; radius R2)-where impurity A is removed by chloride volatilization-before being exhausted from the briquette surface (high temperature close to the furnace temperature). The chlorine gas generation front and the impurity A reaction front start near the briquette surface immediately after charging and move inward with dry distillation time (R1 and R2 approach zero), resulting in chloride volatilization progressing across many regions within the sphere. Although impurities other than A have corresponding volatilization temperatures, chlorine gas necessarily passes through those temperature fronts (R2s different from A) as well to chloride-volatilize and remove them during its passage. In other words, briquetting allows for the efficient removal of any impurity with a volatilization temperature lower than the dry distillation temperature. Furthermore, the excess chlorine gas vented from the briquette is given an opportunity to react with unreacted feed materials in the flow path. And the longer the flow path is, like in a vertical coke oven, the easier it is to improve the reaction efficiency.

[0077] As can be seen in FIG. 8, if R1 and R2 are separated, impurities existing deeper inside than R2 when R1 reaches the furnace center cannot be volatilized by the chlorine within the briquette. In other words, the temperature gradient inside the briquette is important. Not only the chlorine concentration inside the briquette but also moisture and oil content contribute to improving reaction efficiency by promoting a steeper temperature gradient through their latent heat of gasification (cold heat source). Furthermore, since the gas flow is upward in the coke oven, a method of charging briquettes with high chlorine content, moisture, and oil content into the lower layer and charging briquettes and powdery feed materials with low chlorine content, moisture, and oil content into the upper layer is also effective. This method delays chlorine gas generation in the lower layer and increases the heating rate in the upper layer, thereby promoting the chloride volatilization reaction to proceed in the upper layer, effectively improving impurity removal efficiency and chlorine gas utilization efficiency.

[0078] Although the above explanation took briquettes as an example, injection-molded products such as RDF and RPF, or pellets may be used. Regarding the shape, a spherical shape is ideal, but a cylindrical shape or a pillow shape is also acceptable. As for the coke type, although vertical coke ovens have higher reaction efficiency, horizontal coke ovens can also be effectively utilized if the feed materials are made into briquettes or the like.

[0079] As a result of a detailed investigation into the free energy changes of chlorination reactions and the vapor pressures of chlorides for the major components contained in RDF, it was found that heavy metals (Zn, Pb, Cu) and alkali metals (Na, K), which affect the blast furnace condition and / or pig iron quality, can be removed by volatilization. Furthermore, it was found that Fe, Mn, Mg, and Ca are also removable by volatilization, which offers the advantage of contributing to an ash reduction (deashing) effect. Conversely, regarding Si, Al, and Cr, while they can be chloride-volatilized as metals, it was found that as oxides (SiO 2 , Al 2 O 3 , Cr 2 O 3 ), the formation of hydrogen chloride is prioritized, resulting in stable compounds. Therefore, these are suitable as refractory components for the high-temperature dry distillation furnace.

[0080] Next, the following describes in detail, using Figure 6, the method to determine the appropriate chlorine content when blending coals and RDF for feeding into a high-temperature dry distillation furnace. The horizontal axis of the figure shows the mixing ratio X of the two types of feed materials; for example, X = 0 indicates 100% coals, and X = 1 indicates 100% RDF. The vertical axis shows the ratio (wt%) of N and Cl components in the feed materials; however, for N, it is scaled by multiplying the conversion ratio 1 / k to NH 3 . Since k depends on the fuel type, it must be confirmed for each fuel; however, for a mixture of coals and waste plastics, k = 3 as described above. Let Y N (X) denote the N content (wt%) of the blended fuel at the mixing ratio X and Y Cl (X) denote the Cl content (wt%) at the same mixing ratio. These are expressed by the following equations, which are shown as dashed and solid lines in FIG. 6. Y N X = N 1 − N 0 ⋅ X + N 0 Y Cl X = Cl 1 − Cl 0 ⋅ X + Cl 0 N 0 : N content in coal (wt%) N 1 : N content in RDF (wt%) Cl 0 : Cl content in coal (wt%) Cl 1 : Cl content in RDF (wt%)

[0081] Let Cl v (X) denote the amount of Cl consumed in chlorinating impurities in RDF and coals; then the chlorine content Y Cl (X) in the mixed fuel becomes Y Cl (X) - Cl v (X) after the chlorination reaction. For a mixing ratio where Y Cl (X) - Cl v (X) < 0, the chlorine quantity is insufficient for the chlorination targets, and it is desirable that Y Cl (X) - Cl v (X) ≥ 0. Conversely, if Y Cl (X) - Cl v (X) ≥ 0, HCl is generated, so it is necessary to satisfy the condition [Y N (X) ≥ Y Cl (X) - Cl v (X)] such that it can be neutralized by NH 3 in the ammoniacal liquor.

[0082] In an operation with 100% RDF, Y Cl (1) - Cl v (1) = Cl 1 - Cl v (1). Therefore, it is understood that the RDF should have a Cl ratio satisfying the following expression (Equation 11). N 1 / k ≥ Cl 1 − Cl v 1 ≥ 0 ⇔ N l / k + Cl v 1 ≥ Cl 1 ≥ Cl v 1 For example, the ash in the RDF of FIG. 9 (Table 1) contains 60 wt% of SiO 2 and Al 2 O 3 (inventor's inference from Non-Patent Literature 1), and the remaining 40 wt% can be volatilized (deashed) by reduction chlorination. Calculated from the ash components, Cl v (1) = 5.5wt%. The current RDF contains 1.2 wt% of Cl, which is insufficient for the chlorination reaction even at a mixing ratio of 1 (100% RDF). The chlorine concentration can be increased to 5.5% or more.

[0083] When not considering the chlorination reaction in conventional dry distillation furnaces, Cl v (X) = 0 (Cl 1 < 3), and the mixing ratio X v0 in FIG. 6 becomes the RDF mixing limit. This corresponds to the limit point described as X v0 = 0.37 (Cl 1 = 1.2) for the case in FIG. 9 (Table 1) (X v0 · Cl 1 = 0.44%). The present embodiment enables the active utilization of chlorine for chloride volatilization of impurities, thereby expanding the mixing ratio of chlorine-containing wastes up to 100% while also allowing for further increase in the wastes' chlorine concentration. Note that, even if the chlorine concentration Cl 1 in the wastes or the chlorine charge amount derived from wastes Cl 1 · X v0 does not reach the levels described above, it is obvious that the effects of the present invention can still be enjoyed to a considerable extent if they are increased beyond conventional normal standards or limits. Specifically, this applies to cases where the chlorine concentration Cl 1 (wt%_dry) in the wastes charged into the high-temperature dry distillation furnace and / or the wastes charging ratio X v0 (wt%_dry) satisfy at least either Cl 1 ≥ 3% or Cl 1 · X v0 ≥ 0.5%.

[0084] While it is important to grasp Cl v (X); however, it is possible to determine it before operation by analyzing ash, and it can also be corrected during operation based on the NH 3 concentration in the ammoniacal liquor. Also, due to the characteristic of Y N (X) = Y Cl (X) - Cl v (X), the HCl generation rate can be adjusted by changing the mixing ratio. Therefore, by grasping the concentration of NH 3 and NH 4 Cl in the ammoniacal liquor, the margin of the mixing ratio change can be understood before adjustment.

[0085] Now, let us reconsider the ash (SiO 2 , Al 2 O 3 ) remaining in the carbonized material (char) produced from RDF in the high-temperature dry distillation furnace. According to the present embodiment, in the RDF of FIG. 9 (Table 1), 40% of the ash can be reduced and / or volatilized (deashed), lowering ash content from 11.5% to 6.9%. However, since the FC of RDF is low at 14.7%, the ratio of ash to FC remains high (Ash / FC = 47%). As described above, since the Tar yield of plant-based biomass is comparable to the char yield, the ash content (wt%) in the total injection-fuel combining solid and liquid can be considered to be about half of the ash content (wt%) in the solid fuel alone. However, compared to ash / FC = 12.5% and 14% for coke-oven feed coal (C / O feed coal) and LV coal shown later [Table 2 in FIG. 10], further reduction of ash is desirable as a blast furnace tuyere-injection fuel.

[0086] Therefore, focusing on the feature of the present embodiment that "the carbonized material (char) produced in the high-temperature dry distillation furnace is pulverized (similar to PCI) and transported via COM to be injected from the blast furnace tuyeres," a method to further deash the char was devised, which is to install "deashing equipment using a selective agglomeration method using heavy oil or the like" between the pulverization equipment and the COM transport. Specifically, this devised method utilizes at least a portion of the aforementioned liquid fuel to de-ash the carbonized material (char) which is the solid fuel after pulverization.

[0087] Coal deashing methods can be broadly categorized into flotation selection methods and selective agglomeration methods, which utilize the hydrophobic difference between coal and ash, and heavy liquid separation methods, which utilize specific-gravity differences. To increase the deashing ratio, it is important to finely pulverize the coal to separate the carbonaceous matter from the inorganic matter; however, in heavy liquid separation methods and ordinary flotation methods, the more finely the coal is pulverized, the lower the deashing ratio and the carbonaceous matter recovery ratio become. In this respect, the Oil Agglomeration method using heavy oil or the like and the agglomeration-flotation method are advantageous and have already been developed as coal deashing technologies (Patent Literature 3, Non-Patent Literature 7). Another advantage is that these deashing processes after fine pulverization can remove water-soluble impurities that may remain to some extent as unreacted components in the carbonized material.

[0088] As shown in FIG. 1, in the present embodiment, since the whole amount of the product (char) from the high-temperature dry distillation furnace is finely pulverized for the blast furnace injection fuel, the preprocessing (fine pulverization) required for the deashing process is already completed. Therefore, it is desirable to additionally install deashing equipment 11 downstream of the pulverizer 7, depending on the ash content of the char (e.g., by dedicating the equipment downstream of the discharge of batteries of high-temperature dry distillation furnaces using RDF). As the agglomerating agent (binder), low-volatility oil is desirable, and it is preferable to utilize heavy oil and / or Tar generated in the coke oven 3 and / or the high-temperature dry distillation furnace 2. When using heavy oil or Tar as an agglomerating agent, it is desirable to maintain it at 40 to 60°C due to its viscosity characteristics. As shown in FIG. 5, the related equipment of the present embodiment (high-temperature dry distillation furnace 2, COM 12, blast furnace 1) is preferably installed adjacent to each other in principle. Accordingly, the sensible heat of the deashing equipment 11 is transferred to the sensible heat of the COM fuel and ultimately introduced into the furnace as the sensible heat of the blast furnace tuyere-injection fuel, thus avoiding energy waste.

[0089] According to the flow in FIG. 1, coke breeze is all charged into the high-temperature dry distillation furnace. This allows the removal (reduction chloride volatilization) of alkalis (Na, K) remaining in the coke breeze which hinder the operation of the sintering machine and blast furnace-in the high-temperature dry distillation furnace, and instead promotes the reduction chlorination reaction of equation (6) by using coke breeze as its C source.EXAMPLES

[0090] As an example, the amount of C consumed (∝ CO 2 emissions) in the ironmaking area (blast furnace, coke oven, sintering machine) was calculated, using the carbonaceous materials shown in FIG. 9 (Table 1) on a 100% sinter basis. Coke-oven feed coals are the coals adjust-blended with caking properties and coalification degree for coke production, whereas LV coals and HV coals are non-coking coals having no (or low) caking properties and are used in the high-temperature dry distillation furnace.

[0091] Note that although the high-temperature dry distillation furnace is equipment for dry distilling Coals at a maximum temperature of 900°C or higher, the calculation in the example assumed equipment (including gas purification equipment) that dry distillates at a temperature equivalent to that of a conventional coke oven. Furthermore, the premise is that the whole amount of COG generated from the coke oven and the high-temperature dry distillation furnace is used for the purpose of a reducing agent (blast furnace reducing gas), while blast furnace top gas or external fuel (CH 4 ) is used as combustion fuel for dry distillation heat, combustion fuel for the hot stove, and combustion fuel for the sintering machine (ignition furnace, DeNOx system), which are for the purpose of heat sources.

[0092] First, Table 3 in Figure 11 compares the estimations of the carbon (C) consumption between the case using LV coal in FIG. 2 (Patent Literature 1) where the present embodiment is not applied, and the cases using LV coal or HV coal in FIG. 3 where the present embodiment is applied to the blast furnace tuyere injection line. Note that the figures in the table are rounded to the nearest digit, so the sum of the figures may not necessarily match (the same applies to other tables).

[0093] Comparing the cases "FIG. 2 × LV coal" and "FIG. 3 × LV coal"-using the same LV coal, the "FIG. 3 × LV coal" case applying the present embodiment shows an improvement of approximately 18 kg / tp in the carbon intensity of the blast furnace process. Although approximately 9 kg / tp of carbon intensity is added in the high-temperature dry distillation furnace, a total reduction of approximately 9 kg / tp of carbon intensity is achieved in the total ironmaking area.

[0094] In FIG. 3, even when LV coal is replaced with HV coal, the total carbon intensity increase is limited to 3 kg / tp, reducing the impact of changing coal types, and resulting in a 5 kg / tp improvement compared to "FIG. 2 × LV coal" without applying the present embodiment. Although not shown in the table, in the case of "FIG. 2 × HV coal" where the present embodiment is not applied, the coal rate × oxygen rate becomes 582 kg / tp × 368 Nm 3< / tp, making operation difficult; therefore, HV coal cannot be used. However, in the "FIG. 3 × HV coal" case, the rates can be reduced to 228 kg / tp × 137 Nm 3< / tp-less than half that of the conventional method-achieving a lower level of carbon intensity (CO 2 intensity) than the example using LV coal (Patent Literature 1) without applying the present embodiment. This demonstrates that the applicable range of carbonaceous materials can be expanded.

[0095] The bottom row of FIG. 11(Table 3) shows the C-reduction amount when converting CH 4 to H 2 . Since the carbon intensity of the conventional hot-blast based blast furnace process is approximately 630 kg / tp (2.3 t / tp in CO 2 equivalent), if green hydrogen can be utilized instead of CH 4 , CO 2 intensity can be halved without considering CO 2 reuse or underground storage.

[0096] Next, Table 4 in FIG. 12 shows the cases using LV coal or HV coal in FIG. 4, where the present embodiment is also applied to the sintering fuel of the sintering machine.

[0097] In the "FIG. 4 × LV coal" case, the carbon intensity deteriorates (increases) by 7 kg / tp compared to "FIG. 3 × LV coal", and in "FIG. 4 × HV coal", the carbon intensity deteriorates by 10 kg / tp compared to "FIG. 3 × HV coal". The main cause is the increased carbon intensity in the high-temperature dry distillation furnace due to the increased production of sintering fuel. Still, "FIG. 4 × HV coal" has a carbon intensity 8 kg / tp lower than "FIG. 2 × LV coal", contributable to CO 2 emission reduction regardless of coal types.

[0098] Furthermore, if HV coal is converted to biomass-based fuel (including semi-carbonized fuel), carbon intensity derived from HV coal can be zero. Therefore, if all HV coal is converted, carbon intensity will be reduced by 248 kg / tp, reducing the total carbon intensity from 381 kg / tp to 133 kg / tp (less than 1 / 4 of the conventional blast furnace process). If CH 4 is converted to green H 2 , carbon intensity can be further reduced by 57 kg / tp, suppressing total carbon intensity to 76 kg / tp (about 1 / 8 of the conventional blast furnace process). Moreover, 45 kg / tp of the 76 kg / tp is the C component in the pig iron (hot metal), which can be recovered as CO gas when refining the pig iron into steel in a converter installed downstream, and can also be used as reducing gas for the blast furnace. This means total carbon intensity can be suppressed to approximately 30 kg / tp (about 1 / 20 of the conventional blast furnace process).

[0099] As described above, the present embodiment enables the utilization of wastes other than pure biomass fuels as coal-alternative fuels. Although the coal emission factors of waste-derived solid fuels are not zero, they provide substantially the same CO 2 reduction effects as biomass fuels in terms of reducing the potential CO 2 emissions from the fossil fuels (coals) they replace.

[0100] Table 5 in FIG. 13 shows the cases using LV coal or HV coal in FIG. 1-a model case of the present embodiment (where pulverized char transport is changed from the pneumatic transport in FIG. 4 to COM transport).

[0101] The total carbon intensity for LV coal remains unchanged from Table 4 in FIG. 12, but for HV coal, it increases compared to Table 4. However, when replacing coal and heavy oil with biomass fuel, the improvement effect in each case is greater than that of respective cases for biomass fuel conversion in Table 4.

[0102] The heavy oil requirement for COM is determined by the ratio of solid fuel to liquid fuel, becoming unnecessary at a ratio of 1:1. As described above, biomass-based fuels and waste plastics often provide higher liquid fuel yields than solid fuel yields, increasing their blending ratio (decreasing the coal ratio) eventually eliminates the need for heavy oil, and at a coal blending ratio of 0, the solid fuel concentration in COM becomes < 50 wt%. In other words, since fossil fuels such as coal and heavy oil are no longer required, apparent CO 2 intensity can be reduced to 114 kg / tp (less than 1 / 5 of the conventional blast furnace process). The gaseous fuel (COG) yield of biomass-based fuels and waste plastics is also higher than that of HV coal. Therefore, if the blending ratio of these coals increases, externally procured CH 4 can be substituted by the increased COG, making it possible to achieve a total carbon intensity of 76 kg / tp without using green H 2 or C-recycling / CO 2 -storage. This value is approximately 1 / 10 of the total carbon intensity in the conventional blast furnace process. In this regard, the fact that there are 200 million t / y of wastes incinerated in Japan (estimated by the present inventor) represents an advantage from the perspective of coal-alternative fuel availability (urban-type circular resources generated every year). By chemically recycling those that meet quality and economic criteria as coal-alternative fuels for the present embodiment, it is possible to lead to CO 2 reduction in the steel industry and waste management.

[0103] So far, the embodiments and examples have described a method of utilizing carbonized material (char) produced in a high-temperature dry distillation furnace for the blast furnace process, wherein coarse-crushed char produced by crushing all or part of the char with a crusher is used as a sintering fuel for sinter, and the undersize fraction generated in the crushing process or the pulverized char produced in a pulverizing process is injected from the tuyeres at the lower part of blast furnace. However, as a means for supplying carbonized material into the blast furnace, in addition to the method of injecting it from the tuyeres at the lower furnace after pulverization, there is also a method of charging all or part of the char after crushing from the furnace top together with coke and ore, as shown in FIG. 7.

[0104] The top-charged char is preheated to the lower furnace boundary temperature (e.g., 1300°C) while descending to the lower furnace. (1) This enhances the heat transfer efficiency of the char combustion heat to the lower furnace, and simultaneously, (2) it reduces the heat-required in the lower furnace to heat the ash (mainly SiO 2 ) in char up to approximately 1500°C for being discharged as slag-to about 1 / 5. Therefore, the fuel rate can be further reduced. In other words, charging char from the furnace top has a thermal effect equivalent to reducing the ash content to 1 / 5, so even the char (high ash content) produced from feed materials having a high ash content relative to FC (fixed carbon)-such as RDF-can be utilized without deashing process. Note that the preheating effect of ash in char has a theoretically similar effect when utilized as a sintering fuel for sinter charged from the furnace top.

[0105] If char charged from the furnace top is pre-processed with high-temperature dry distillation, it contains almost no volatile matter. Accordingly, even if gas is generated from the char due to preheating at 900°C or higher, it will contain almost no tar or hydrocarbons. Even if hydrocarbons are present, they will be gas-reformed by H 2 O and / or CO 2 . Therefore, the gas can be treated as normal top gas (CO, H 2 , CO 2 , H 2 O, N 2 ) without hindering operation.

[0106] Charging char from the furnace top is not only thermally superior to direct injection into the lower furnace, but also functions to preserve coke quality; since char have higher reactivity than coke, it gasify sacrificially before coke undergoes gasification reactions (C + CO 2 = 2CO, H 2 O + C = H 2 + CO). Since the reaction rate (kg / s) of a particle is proportional to its specific surface area (m 2< / kg), finer particle size is desirable unless it is blown away. Assuming the average particle size of coke in the lower furnace is approximately 30 to 35 mm, a particle size of 10 mm or less is desirable to achieve a specific surface area (proportional to combustion rate) 10 times that of the coke. Also, a particle size of 3 mm or more is desirable to prevent the char from being easily blown away by even a slight amount of blow-by gas. In short, it is desirable for the top-charged char to mainly (i.e., 70% or more) have a particle size between 3 mm and 10 mm.

[0107] Since classification devices such as screens have classification efficiency limits, some char smaller than the sieve mesh is also charged from the furnace top. Regarding char discharged out of the furnace accompanying the top gas, it can be collected by a primary dust collector or a secondary dust collector. It may be pulverized and injected from the tuyeres at the lower furnace. However, since it also contains iron-based dust and auxiliary raw material dust in addition to carbonaceous material, it can be effectively utilized as a raw material for sinter (sintering fuel), as has been done conventionally.

[0108] Increasing the amount of top-charging char will shift the fuel-combustion source in the lower furnace from primarily tuyere-injection fuel (pulverized char and Tar) toward top-charging char. Combustion by tuyere-injection fuel tends to generate higher combustion heat on the furnace wall side than at the furnace center, as in conventional blast furnaces. However, since top-charging char can be distributed equally in the radial direction, combustion is more likely to occur uniformly in the radial direction, enabling higher heat at the furnace center where combustion ends. In other words, the heat distribution in the lower furnace can be adjusted by adjusting the top-charging char rate.

[0109] In addition to the aforementioned method, another method for adjusting the heat distribution in the lower furnace is to extend the combustion time of char by mixing coarser particles into the pulverized char. FIG. 7 shows a line installed to bypass the pulverizer and mix the undersize fraction (fine char) from the screen after the crusher into the pulverized char, for the purpose of adjusting the pulverized char combustion time. However, for char with a high ash content, it is desirable to perform pulverization and deashing processes before converting it into COM. Since the amount of pulverized char injection is reduced by using top-charging char, the oil required for COM transport can be covered solely by Tar derived from coal or coal-alternative fuels (i.e., eliminating the need for external fuel such as heavy oil).

[0110] On the other hand, disadvantages of top-charging char include: - Increase in slag volume and auxiliary raw materials (raw material-derived CO 2 sources) in case of char with a high ash content compared to tuyere injection with deashing; - Slower responsiveness to changes in the lower furnace owing to its long time to reach the lower furnace. Accordingly, it is desirable to appropriately adjust the ratio between top-charging and lower-furnace injection while considering factors such as ash content in the char, yield of liquid fuel as Tar, undersize fraction of char-crushing, and the like, while also observing the radial heat distribution in the lower furnace as described above. Furthermore, the ability to adjust operations according to raw materials and furnace conditions is a strength to use top-charging and lower-furnace injection together.

[0111] From the above, it is understood that the following method is distinctive and effective as an operating method in the blast furnace process: Carbonized material (char)-solid fuel produced in a high-temperature dry distillation furnace-is utilized such that all or part of the solid fuel is crushed by a crusher and used as a sintering fuel for sinter and / or as a top-charging material for the blast furnace; also, all or part of the solid fuel is pulverized so that 70% or more of particles have a particle size of 0.1 mm or less and is injected from the blast furnace tuyeres at the lower furnace.

[0112] Table 6 in FIG. 14 shows a comparison of carbon consumptions between the "FIG. 1" case (pulverized-char injection to the lower furnace alone; without deashing) and the "FIG. 7" case (combined with coarse-char top-charging), using the HV coal shown in Table 2 of FIG. 10. Note that the "FIG. 7 x HV coal" case exemplifies a scenario where the ratio of the top-charging coarse-char to the lower-furnace-injection pulverized-char is determined so that external fuel (heavy oil) is not required as the COM for lower-furnace injection; this ratio is 77% : 23% in the "FIG. 7 x HV coal" case. However, this ratio varies depending on the ratios of FC (Fixed Carbon) and VM (Volatile Matter) of the coals (or coal-alternative fuels) including coke-oven feed coals, the gangue content of ore, the operating conditions of the coke oven and the high-temperature dry distillation furnace, etc.

[0113] In the "FIG. 7 × HV coal" case shown in Table 6 of FIG. 14, the total carbon intensity is smaller than in any other example (case) because high C-emission-factor fuels such as coal and heavy oil could be reduced. Therefore, it is understood that, at least when using coals as described in Table 2 of FIG. 10 without deashing, it is preferable to charge char from the furnace top as much as possible, and it may also be used as a sintering fuel for sinter which is similarly charged from the furnace top. In addition, the total char consumption of coarse char and pulverized char in the case (= 173 kg / tp) is the smallest compared to other cases in FIGs. 1, 4, and 5, and the CH 4 consumption is the largest compared to other cases. Thus, it can be said that this method is most suitable for using biomass-based (including waste-based) fuels with low carbon yield and high COG yield as alternative fuels.

[0114] In existing steelworks, two or more (multiple) blast furnaces are often installed. In this case, as a method for reducing CO 2 derived from CH 4 described in Table 3 (FIG. 11) to Table 6 (FIG. 14), one or more of the multiple blast furnaces can be modified to the system of the present invention, and surplus energy (including converter gas) from the remaining conventional blast furnaces can be used in place of CH 4 . Consequently, the production amount using this invention leads to a CO 2 reduction of the entire steelworks.

[0115] For example, in the "FIG. 7 × HV coal" case of FIG. 14 (Table 6), the carbon intensity per 1 t of pig iron is 362 kg / tp. However, by utilizing surplus gas from an adjacent blast furnace, the of 68 kg / tp (= 128 Nm 3< CH 4 / tp = 4.6 GJ / tp) derived from CH 4 becomes unnecessary, reducing the carbon intensity to 294 kg / tp (equivalent to 1.08 t-CO 2 / tp CO 2 intensity). That is, most of the coke-oven feed coals can be replaced with HV coal and expensive external fuels also can be eliminated, thus halving the blast furnace CO 2 intensity from the current approx. 2.2 t-CO 2 / tp to 1.08 t-CO2 / tp. Note that the surplus energy in the conventional blast furnace process is 7.4 GJ / tp (estimated by the present inventor) including Tar, which balances 0.62 tp (= 4.6 / 7.4) of a conventional blast furnace production with 1 tp of "FIG. 7 × HV coal" production.

[0116] Although the present invention has been described with reference to the blast furnace as a metallurgical furnace, it can also be applied to other metallurgical furnaces due to its principles and effects. Some examples are illustrated below.

[0117] For example, as a CO 2 reduction measure in the steel industry, a process of "producing DRI (Direct Reduced Iron) in a hydrogen-based direct reduction furnace and melting and carburizing the DRI in an electric smelting furnace to produce pig iron (hot metal)" is being developed in Europe and Japan as a substitute for the conventional blast furnace process. The direct reduction furnace (metallurgical furnace) requires green hydrogen to replace conventional natural gas, and the electric smelting furnace (metallurgical furnace) requires a carburizing agent such as coke, posing issues regarding their energy efficiency and CO 2 reduction amount limits. However, according to the present invention, by utilizing coke ovens-which will become idle facilities due to the shutdown of existing blast furnaces-as high-temperature dry distillation furnaces and preprocessing wastes close to carbon neutral (CN), it becomes possible to provide CN gaseous fuel (COG) as a hydrogen alternative for the reducing agent and CN high-quality solid fuel (char) as a coke alternative for the carburizing agent. Liquid fuel can also be used as heating fuel for a gas reformer for the direct reduction furnace, etc.

[0118] The carburizing agent needs to penetrate the slag layer, which has a higher specific gravity than the carbonaceous material, and enter the hot metal. Therefore, high-temperature dry distillation is crucial to minimize VM (volatile matter) that generates gas. Furthermore, since the carburization rate is inversely proportional to the particle size, it is also effective to inject it after pulverization.

[0119] In addition, as a CO 2 reduction measure in the steel industry, the conventional process of "producing molten steel by melting scrap or DRI in an electric arc furnace" is also being promoted instead of the blast furnace. However, since electricity costs significantly affect the economics of the electric arc furnace (metallurgical furnace), in countries with high electricity rates-including Japan, fossil fuels (carbon, natural gas, heavy oil, etc.) have actually been heavily used as slag foaming agents or fuels for scrap melting burners, aiming to reduce electricity intensity. Furthermore, as a countermeasure against dioxins in electric arc furnace exhaust gas, burners are required to decompose DXNs at high temperatures, and fuel consumption is even increased, contrary to the reduction of electricity intensity. However, according to the present invention, by utilizing coke ovens-which will become idle facilities due to the shutdown of existing blast furnaces-as high-temperature dry distillation furnaces, it becomes possible to obtain CN high-quality slag foaming agents and metallurgical fuels.

[0120] As other metallurgical furnaces, it can also be utilized to preprocess raw materials for cupolas (especially coke-less cupolas), smelting reduction furnaces, non-ferrous smelting furnaces, lime calcination furnaces, and the like.

[0121] Note that the direct reduction furnaces and electric smelting furnaces exemplified above exist as independent metallurgical furnaces, respectively, and the present invention can be utilized for each of them. Also, regarding the high-temperature dry distillation furnace, while the utilization of existing coke ovens has been exemplified from the perspective of utilizing existing facilities, the present invention is not limited thereto. There is no problem in installing a high-temperature dry distillation furnace of a type different from coke ovens at a steelworks where no coke oven exists.INDUSTRIAL APPLICABILITY

[0122] The technology according to the present invention also relates to CO 2 reduction from wastes.

Examples

examples

[0090]As an example, the amount of C consumed (∝ CO 2 emissions) in the ironmaking area (blast furnace, coke oven, sintering machine) was calculated, using the carbonaceous materials shown in FIG. 9 (Table 1) on a 100% sinter basis. Coke-oven feed coals are the coals adjust-blended with caking properties and coalification degree for coke production, whereas LV coals and HV coals are non-coking coals having no (or low) caking properties and are used in the high-temperature dry distillation furnace.

[0091]Note that although the high-temperature dry distillation furnace is equipment for dry distilling Coals at a maximum temperature of 900°C or higher, the calculation in the example assumed equipment (including gas purification equipment) that dry distillates at a temperature equivalent to that of a conventional coke oven. Furthermore, the premise is that the whole amount of COG generated from the coke oven and the high-temperature dry distillation furnace is used for the purpose of a r...

Claims

1. A method for preprocessing raw materials, comprising: performing dry distilling of coals outside a blast furnace coke production range or coal-alternative solid fuels under a condition where a maximum dry distillation temperature is 900°C or higher; separating combustibles generated by the dry distillation into solid fuel, liquid fuel, and gaseous fuel; and injecting all or part of the solid fuel, the liquid fuel, or the gaseous fuel into a metallurgical furnace.

2. The method for preprocessing raw materials according to claim 1, comprising: crushing or pulverizing all or part of the solid fuel; and injecting the undersize solid fuel generated in the crushing or the pulverized solid fuel into the metallurgical furnace.

3. The method for preprocessing raw materials according to claim 1 or 2, comprising: producing a synthesis gas mainly composed of CO and H2 from all or part of the gaseous fuel; and blowing the synthesis gas into the metallurgical furnace at a temperature of 800°C or higher.

4. The method for preprocessing raw materials according to claim 1 or 2, comprising: injecting all or part of the liquid fuel into the lower part of the metallurgical furnace.

5. The method for preprocessing raw materials according to claim 4, comprising: mixing the pulverized solid fuel and the liquid fuel in advance; and injecting the mixture into the metallurgical furnace of the lower part.

6. The method for preprocessing raw materials according to any one of claims 1 to 5, comprising: pulverizing all or part of the solid fuel, and using the solid fuel having a particle size of 1 mm or more and 10 mm or less as a sintering fuel for sinter and / or as a top-charging material for the metallurgical furnace; and injecting all or part of the solid fuel pulverized so that 70% or more of particles have a particle size of 0.1 mm or less into the blast furnace from tuyeres.

7. The method for preprocessing raw materials according to any one of claims 1 to 5, comprising: using wastes as coal-alternative solid fuels; wherein the chlorine concentration Cl1 (wt%_dry) in the wastes charged into a high-temperature dry distillation furnace and / or the wastes charging ratio Xv0 (wt%_dry) satisfy at least either Cl1 ≥ 3% or Cl1·Xv0 ≥ 0.5%.

8. The method for preprocessing raw materials according to claim 7, wherein at least a part of the liquid fuel is used for a deashing process of the solid fuel after pulverization.

9. The method for preprocessing raw materials according to claim 7, wherein all or part of the wastes charged into a high-temperature dry distillation furnace are molded in advance and then charged into the furnace.

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