Coke manufacturing method

Abstract

This suppresses the decrease in coke strength when using biomass as a raw material. [Solution] A coke production method for producing coke by carbonizing biomass and blended coal, wherein the molded biomass and the blended coal are mixed and charged into the carbonization chamber of a coke oven, and carbonized.

Description

Technical Field

[0001] The present invention relates to a method for producing coke by carbonizing biomass and blended coal.

Background Art

[0002] Coke is used in a blast furnace as a reducing agent, a heat source, and a support material for maintaining air permeability and liquid permeability.

[0003] Such coke used in a blast furnace (blast furnace coke) is generally industrially produced by carbonizing blended coal as a raw material in a coke oven (chamber oven type coke oven) having a carbonization chamber and a combustion chamber. Blended coal is a mixture of multiple types of coal.

[0004] In recent years, due to the increasing need to reduce CO2 emissions, studies have been underway to replace fossil fuels such as coal and oil with biomass and waste plastics. Therefore, in the steel industry as well, it is required to replace at least a part of the coal (blended coal) used as a raw material for coke with biomass or waste plastics.

[0005] For example, in Patent Document 1, a technique of using waste plastic as a part of a raw material in the production of coke has been proposed. Specifically, waste plastic previously mixed with coal is charged into the lower part of the carbonization chamber of a coke oven, and after charging coal thereon, carbonization is performed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, using waste plastics as a raw material presents a problem: it reduces the yield of coke production. This is because waste plastics turn into gas when they are dry-distilled.

[0008] On the other hand, biomass has the characteristic of being less likely to gasify compared to waste plastics. Therefore, in order to reduce CO2 emissions while suppressing a decrease in yield, it is desirable to use biomass as a raw material for coke production.

[0009] However, using biomass as a raw material for coke production presents a problem: the resulting coke has reduced strength. In other words, stable operation of a blast furnace requires ensuring proper permeability and fluid flow within the furnace, thus demanding strength from the coke. In conventional coke production, the coal used as a raw material softens and melts, bonding together to produce coke with the necessary strength. In contrast, conventional biomass does not soften and melt like coal, so using biomass as a raw material results in coke with many defects and low strength.

[0010] Therefore, in order to utilize biomass as a raw material for coke production, technologies are needed to suppress the decrease in coke strength. However, such technologies have yet to be established.

[0011] For example, Patent Document 2 proposes a technology for using biomass in coke production. Specifically, when coal is carbonized in the carbonization chamber of a coke oven, biomass is charged into the empty space in the carbonization chamber.

[0012] However, the technology proposed in Patent Document 2 aims to reduce the amount of carbon adhering to the inner wall of the coke oven during coke production, and does not take coke strength into consideration. Furthermore, the technology in Patent Document 2 does not produce coke by carbonization of biomass; it merely uses biomass to reduce the amount of carbon adhering to the inner wall. Therefore, the biomass is not initially charged into the carbonization chamber along with the coal, but rather charged after the fire has died down.

[0013] This invention was made to solve the above problems and aims to provide a coke production method that can suppress the decrease in coke strength while using biomass as a raw material. [Means for solving the problem]

[0014] The inventors have found that the above problem can be solved by mixing the biomass molded product with the aforementioned blended coal, charging it into the carbonization chamber of a coke oven, and performing carbonization.

[0015] This invention was completed based on the above findings, and its gist is as follows.

[0016] 1. A method for producing coke by carbon distillation of biomass and blended coal, A method for producing coke, comprising charging a mixture of the biomass molded product and the blended coal into the carbonization chamber of a coke oven and performing carbonization. [Effects of the Invention]

[0017] According to the present invention, high-strength coke can be produced using biomass as a raw material. According to the present invention, a portion of the blended coal used as a raw material can be replaced with biomass, which is a carbon-neutral raw material, thereby reducing CO2 emissions associated with coke production. [Modes for carrying out the invention]

[0018] Next, a method for implementing the present invention will be specifically described. Note that the following description shows examples of preferred embodiments of the present invention, and the present invention is not limited by the following description in any way.

[0019] In the present invention, biomass and blended coal are carbonized to produce coke. At this time, it is important to charge the carbonization chamber of the coke oven with the molded product of the biomass and the blended coal in a mixed state. The reason will be explained below.

[0020] As described above, biomass does not soften and melt like coal. Therefore, if biomass is directly mixed with coal, the melting and bonding of the coals are inhibited. As a result, defects occur and the strength of the coke decreases.

[0021] In contrast, in the present invention, by using a pre-molded product of biomass, it is possible to suppress the strength reduction caused by biomass. This is presumably because the interface between coal and biomass decreases and the adverse effect of biomass is reduced.

[0022] · Biomass As the biomass, any biomass can be used without particular limitation. The definition of the term "biomass" in the present invention shall conform to the definition of the FAO (Food and Agriculture Organization of the United Nations). According to the FAO definition, biomass is a general term for substances of biological origin excluding fossil fuels and the like. Biomass is classified into agricultural (rice straw, sugarcane, rice bran, grass, etc.), forestry (paper waste, sawmill waste, thinned wood, firewood forest, etc.), livestock (livestock waste), fishery (fish processing residue), waste (garbage, RDF (Refused Derived Fuel), garden trees, construction waste, sewage sludge), etc.

[0023] As the biomass, a single type of biomass may be used, or a plurality of types of biomass may be mixed and used.

[0024] Furthermore, while the biomass can be used as is, the pyrolysis products obtained by pyrolyzing at least a portion of the biomass may also be used. When pyrolysis is performed, charred biomass (also called biomass char or biochar) can be used. Alternatively, semi-charred biomass obtained by torrefaction can also be used.

[0025] The size of the biomass molded product is not particularly limited. However, from the viewpoint of reducing the interface between coal and biomass, a larger size of the molded product is desirable. Therefore, the volume of each molded product is 6 cm³. 3 It is preferable that the above conditions are met.

[0026] The proportion of biomass contained in the above-mentioned biomass molded product is not particularly limited, but from the viewpoint of enhancing the CO2 emission reduction effect, it is preferably 50% by mass or more, more preferably 65% ​​by mass or more, even more preferably 80% by mass or more, and most preferably 95% by mass or more. On the other hand, the upper limit of the above proportion is also not limited, and for example, it may be 100% by mass. In other words, the molded product may be a molded product made solely of biomass.

[0027] The molded product may also contain a binder or coal as a component other than biomass. The binder is not particularly limited and any binder can be used. The binder may be an inorganic binder, an organic binder, or both.

[0028] Examples of the inorganic binder include water, cement, gypsum, lime, clay, phosphate, water glass, and silica. Examples of the organic binder include starch, agar, natural rubber, synthetic rubber, bitumen, cellulose derivatives, and resins. Examples of bitumen include tar, asphalt, and pitch. Among these, tar is a byproduct of coke production and is present in sufficient quantities within steel mills, making it a preferred binder.

[0029] Examples of coal contained in the molded product include peat, lignite, bituminous coal, and anthracite. There is a concern that the molded product may pulverize due to impact during transportation, and that some of the pulverized molded product may be mixed into the blended coal, leading to a decrease in coke strength. Therefore, from the viewpoint of minimizing the decrease in coke strength when mixed in, it is preferable to use bituminous coal (raw coal) which is normally used in coke production.

[0030] In one embodiment of the present invention, a molded product comprising biomass and a binder can be used.

[0031] The above-mentioned molded products can be manufactured by any method. For example, they can be manufactured by methods such as granulation, compression, molding, bonding, and kneading, and it is also possible to manufacture them by combining multiple of these methods. Among these, the method of compaction molding using a double-roll molding machine is preferred from the viewpoint of mass production.

[0032] • Charging into the carbonization chamber The molded biomass and blended coal are loaded into a charging car, and the mixture of molded biomass and blended coal is then charged from the charging car into the carbonization chamber of the coke oven. The coke oven is not particularly limited, and any coke oven can be used. A typical coke oven (chamber-type coke oven) has a structure in which combustion chambers and carbonization chambers are arranged alternately, and the adjacent carbonization chamber is heated by burning fuel gas in the combustion chamber. Therefore, in this invention as well, the molded biomass and blended coal that will be used as raw materials should be charged into the carbonization chamber.

[0033] The proportion of biomass in the total raw materials charged into the carbonization chamber (mixing ratio) is not particularly limited. However, if the mixing ratio is excessively high, the coke quality may deteriorate. For this reason, the mixing ratio is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less. On the other hand, the lower limit of the mixing ratio is also not particularly limited, but from the viewpoint of increasing the effect of reducing CO2 emissions, it is preferable to make it somewhat higher. For this reason, the mixing ratio is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and even more preferably 1.5% by mass or more. [Examples]

[0034] To confirm the effects of the present invention, coke was produced by carbon distillation of biomass and blended coal using the following procedure.

[0035] First, the blended coal used had an average maximum reflectance (Ro) of vitrinite of 1.0% and a common logarithm of the maximum fluidity (MF) measured by a Gieseler plastometer of 2.50 log ddpm. The blended coal was then crushed to a particle size of 3 mm or less before use.

[0036] As the biomass used, woody biomass was crushed to a particle size of 3 mm or less. 10% by mass of water was added to the crushed biomass as a binder, and compaction was performed to obtain spherical molded products. The mass and diameter of the molded products are shown in Table 1.

[0037] The mixing ratios for the molded product were as shown in Table 1. The mixing ratios are expressed by the following formula. Mixing ratio (mass %) = Mass of molded product / (Mass of molded product + Mass of blended coal) × 100

[0038] Next, coke was produced by carbonization of the compounded molded material and blended coal. The carbonization was carried out using a carbonization boiler under conditions that simulated the carbonization chamber of a coke oven. Specifically, first, 16.5 kg of the mixture of the molded material and blended coal was subjected to a bulk density of 775 kg-dry / m³.3 The material was then packed into a carbonization vessel. In this state, carbonization was carried out in an electric furnace, maintaining the furnace wall temperature at 1050°C for 6 hours. After that, it was cooled with nitrogen to obtain coke.

[0039] However, as a comparative standard, in Comparative Example No. 1, coke was produced using only the aforementioned blended coal without using biomass. In Comparative Examples No. 6 and 7, the crushed biomass was mixed with the blended coal without being molded.

[0040] Next, to evaluate the strength of the obtained coke, the drum strength index DI of each coke was used. 150 15 The following measurements were taken. The measurements were carried out in accordance with the rotational strength test method of JIS K2151.

[0041] Next, the obtained drum intensity index DI 150 15 Therefore, the drum strength index DI of Comparative Example No. 1, which is the comparison standard. 150 15 The drum intensity difference ΔDI was calculated by subtracting [a specific value]. The results are shown in Table 1.

[0042] A negative ΔDI value indicates that the coke produced is weaker than coke produced without biomass. While the reduction in coke strength should be minimized, a ΔDI of -2.0 or higher is considered acceptable for practical purposes, as it can be compensated for by fine-tuning the coal blend and production conditions. Therefore, in this study, a ΔDI of -2.0 or higher indicates that the reduction in strength due to biomass is sufficiently suppressed.

[0043] As shown in Table 1, the method of the present invention made it possible to obtain coke with a strength level that is acceptable for practical use. In contrast, in the comparative example where biomass was used as is without being molded, the ΔDI was -2.0 or less, indicating a significant decrease in strength due to the biomass.

[0044] [Table 1]

Claims

[Claim 1] A coke production method that involves carbon distillation of biomass and blended coal to produce coke, A method for producing coke, comprising charging a mixture of the biomass molded product and the blended coal into the carbonization chamber of a coke oven and performing carbonization.

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