Method for producing carbon monoxide and carbon materials using coke oven gas

Abstract

To provide a method for producing carbon monoxide and carbon materials using coke oven gas, which enables carbon monoxide and carbon materials to be produced from carbon dioxide inexpensively and easily. In a method for producing carbon monoxide using coke oven gas, carbon dioxide is reduced with the coke oven gas to produce carbon monoxide. In a method for producing a carbon material using coke oven gas, the carbon monoxide produced using the coke oven gas is brought into contact with the coke oven gas to produce a carbon material.

Description

[Technical Field]

[0001] The present invention relates to a method for producing carbon monoxide and carbon materials using coke oven gas (COG) generated when producing coke by pyrolysis of coal in a coke oven. [Background technology]

[0002] In recent years, global warming has caused the average global temperature to rise, resulting in a variety of problems, including changes in ecosystems, abnormal weather, the spread of infectious diseases, and damage to agricultural and marine crops. The main cause of this global warming is the increase in carbon dioxide (CO2) emissions from industrial activities. For example, the coke used in blast furnaces is produced by carbonizing coal in coke ovens, and during this process, gases containing CO2 are generated and emitted from the coke ovens, so there is a need for technology to reduce these CO2-containing exhaust gases.

[0003] Technologies for reducing CO2 include, for example, a technology for storing CO2 deep underground (CCS: Carbon dioxide Capture and Storage), as described in Patent Document 1, and a technology for effectively utilizing CO2 (CCU: Carbon dioxide Capture and Utilization), as described in Patent Document 2. Technologies for effectively utilizing CO2 include technologies that directly utilize CO2, specifically technologies that capture CO2 and use it by liquefying or solidifying it, and technologies that indirectly utilize CO2, specifically technologies that use CO2 as fuel or material.

[0004] CCS has already been put into practical use and can store CO2 stably for a long period of time, but it cannot effectively utilize the CO2 itself. On the other hand, direct use of CCU has already been put to practical use, and although the process is simple, there are issues such as low profitability, and it is not expected that its practical use will expand. As for indirect use, various technological developments are being carried out and attempts are being made to put it to practical use, and future expansion is expected from the perspective of effective use of CO2 and profitability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-126787 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-233248 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a method for easily and inexpensively producing carbon monoxide and / or a carbon material from carbon dioxide. [Means for solving the problem]

[0007] The present inventors, while conducting various studies on the effective use of exhausted carbon dioxide (carbon recycling), first noticed that coke oven gas contains hydrogen and methane. They then discovered that by using this coke oven gas to reduce carbon dioxide, it is possible to achieve both a reduction in carbon dioxide and the effective use of coke oven gas, thereby solving the above-mentioned problems, and thus completed the present invention.

[0008] The gist of the present invention is as follows. [1] A method for producing carbon monoxide using coke oven gas, characterized by producing carbon monoxide by reducing carbon dioxide with coke oven gas. [2] The method for producing carbon monoxide using coke oven gas according to [1] above, wherein the carbon dioxide is exhaust gas generated from a coke oven.

[0009] [3] A method for producing a carbon material using coke oven gas, characterized in that carbon monoxide produced by the production method according to [1] or [2] above is brought into contact with coke oven gas to produce a carbon material. [4] The method for producing a carbon material using coke oven gas according to [3] above, wherein a catalyst is used when carbon monoxide is brought into contact with the coke oven gas. [5] The method for producing a carbon material using coke oven gas according to [4] above, wherein the catalyst is a nickel-based catalyst or an iron-based catalyst. [6] The method for producing a carbon material using coke oven gas according to any one of [3] to [5] above, wherein the produced carbon material is a carbon nanofiber or a carbon nanotube. [Effects of the Invention]

[0010] According to the method of the present invention using coke oven gas, it is possible to inexpensively and easily produce carbon monoxide and / or carbon materials from carbon dioxide. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is an explanatory diagram showing the flow of gas generated from a coke oven. [Figure 2] FIG. 1 is an explanatory diagram of a method for producing carbon monoxide and carbon materials using coke oven gas according to the present invention. [Figure 3] 1(a) to 1(c) are conceptual diagrams showing the process for producing a carbon material. [Figure 4] 1(a) is an explanatory diagram of the apparatus used in the carbon monoxide production test, and FIG. 1(b) is an explanatory diagram showing the temperature rise inside the SUS pipe during the test and the type of gas supplied into the SUS pipe. [Figure 5] FIG. 1(a) is an explanatory diagram of the apparatus used in the carbon material production test, and FIG. 1(b) is an explanatory diagram showing the temperature rise inside the quartz tube during the test and the type of gas supplied into the quartz tube. DETAILED DESCRIPTION OF THE INVENTION

[0012] The method of the present invention is characterized in that carbon dioxide (CO2) is reduced with coke oven gas (COG) (CO2 reduction step) to produce carbon monoxide, and the produced carbon monoxide is brought into contact with coke oven gas to produce a carbon material.

[0013] The method of the present invention is a novel technique that utilizes coke oven gas containing hydrogen gas and methane gas. For example, there is no need to separately prepare reducing gases such as hydrogen and methane, and there is also no need to newly install or expand production facilities for reducing gases such as hydrogen and methane. Therefore, the method of the present invention is a method that can inexpensively and easily produce carbon monoxide.

[0014] Here, the carbon dioxide used as a raw material may be carbon dioxide contained in exhaust gas emitted from manufacturing facilities, processing facilities, waste disposal facilities, etc., and it is preferable to use carbon dioxide contained in exhaust gas (combustion exhaust gas) generated from a coke oven, as this allows carbon monoxide to be produced efficiently within a coke manufacturing facility.

[0015] As shown in Figure 1, when coke is produced in a coke oven, that is, when coal is carbonized, coke oven gas, which is generated in the coke oven and processed in a gas refinery, is used as fuel. When coke is produced, a large amount of carbon dioxide is emitted from the combustion chamber of the coke oven, and most of this is exhaust gas from the coke oven gas supplied to the combustion chamber, so reducing the carbon dioxide contained in the exhaust gas is important in coke oven operation.

[0016] Here, the concentration of carbon dioxide contained in the exhaust gas is, for example, about 10% or less, and after recovering the exhaust gas and going through a process of concentration, etc., the concentration is preferably increased to 20% or more, more preferably to 40% or more, even more preferably to 60% or more, and particularly preferably to 80% or more. The upper limit is not particularly limited, but is about 90% in consideration of efficient concentration of carbon dioxide.

[0017] As noted above, the process of the present invention uses coke oven gas. As shown in Figures 1 and 2, coke oven gas is generated during coke production in a coke oven. This coke oven gas is obtained by processing gas generated in a coke oven in a gas refining facility, and is a clean gas containing, for example, 50 vol% or more of hydrogen gas and 15 vol% or more of methane gas, and much of it is used as fuel for coke ovens.

[0018] Coke oven gas is generated in large quantities from coke ovens, and not all of it can be used as fuel for the coke oven. From the viewpoint of effective utilization of coke oven gas, the present invention uses it to produce carbon monoxide and carbon materials. This allows for effective utilization of coke oven gas. For example, the carbon component in methane gas contained in coke oven gas can also be used as a raw material for the produced carbon material, thereby increasing the amount of carbon material produced.

[0019] The gas refining equipment used to process the gas generated from the coke ovens may include, for example, a cooling device, an electric dust collector, a desulfurization device, an ammonia removal device, and a diesel recovery device, depending on the quality of the coal processed in the coke oven (the component composition of the gas generated), and these devices recover tar, sulfuric acid, liquid ammonia, diesel, etc.

[0020] The present invention will be described in detail below. First, carbon dioxide is reduced with coke oven gas to produce carbon monoxide. At this time, since the coke oven gas contains hydrogen gas and methane gas, the following reaction occurs: That is, in the present invention, carbon monoxide can be produced using inexpensive coke oven gas as an alternative to expensive hydrogen and methane.

[0021] CO2+ H2→ CO + H2O (reverse shift reaction) CO2 + CH4 → 2CO + 2H2 CO2+ C → 2CO (Boudouid reaction)

[0022] The treatment temperature during the reduction of carbon dioxide to carbon monoxide is not particularly limited as long as it allows the reduction reaction of carbon dioxide to proceed. However, in order to promote the reduction reaction, the temperature is preferably in the range of 500 to 800°C, more preferably in the range of 500 to 750°C, and even more preferably in the range of 550 to 750°C. A catalyst may be used in producing carbon monoxide. For example, an alumina-based catalyst may be used. The shape of the catalyst is not particularly limited as long as it can increase the contact area, and examples of the catalyst include granular, honeycomb, pellet, and powder shapes.

[0023] 1 and 2, when exhaust gas (preferably a concentrated carbon dioxide-containing gas, the same applies hereinafter) generated from a coke oven is used as a raw material, the exhaust gas is brought into contact with coke oven gas purified in a gas purification facility in a chamber (to form a coke oven gas atmosphere), whereby carbon monoxide can be produced using the coke oven gas as is. The produced carbon monoxide is supplied downstream together with the coke oven gas (off-gas) that did not contribute to the reduction reaction.

[0024] Next, the produced carbon monoxide is brought into contact with coke oven gas to produce a carbon material. At this time, since the coke oven gas contains hydrogen gas, the following reaction occurs: That is, in the present invention, a carbon material can be produced using inexpensive coke oven gas as an alternative to expensive hydrogen.

[0025] CO(g) + H2(g) → C(s) + 2H2O

[0026] The treatment temperature when producing a carbon material from carbon monoxide is not particularly limited as long as the carbon material can be produced. In producing a carbon material from carbon monoxide and hydrogen gas, the temperature is preferably in the range of 500 to 800°C, more preferably in the range of 500 to 750°C, and even more preferably in the range of 550 to 750°C, from the viewpoint of improving production efficiency.

[0027] Here, when carbon dioxide is exhaust gas generated from a coke oven, as shown in Figures 1 and 2, the produced carbon monoxide is brought into contact with coke oven gas flowing through a pipe (to create a coke oven gas atmosphere), and the room temperature coke oven gas can be used directly to produce a carbon material. The produced carbon material is recovered, and the coke oven gas (off-gas) that did not contribute to the production of the carbon material is returned to the pipe.

[0028] When producing the carbon material, for example, a CCVD method (catalytic vapor deposition method) using a catalyst can be used. As shown in Figures 3(a) to (c), for example, by placing a catalyst placed on a substrate in a high-temperature atmosphere in which produced carbon monoxide and coke oven gas flow, carbon atoms in the carbon monoxide are adsorbed onto the catalyst, and these adsorbed carbon atoms diffuse onto the surface and inside of the catalyst, producing a carbon material mainly composed of carbon.

[0029] Examples of catalysts include nickel-, iron-, and cobalt-based catalysts. However, nickel- or iron-based catalysts are preferred for improving the production efficiency of carbon materials. Examples of nickel-based catalysts include nickel chloride (NiCl2, NiCl2·6H2O), nickel nitrate (Ni(NO3)2, Ni(NO3)2·6H2O), nickel acetate (Ni(CH3COO)2·4H2O), and nickel oxide (NiO). Examples of iron-based catalysts include ferric nitrate (Fe(NO3)3·9H2O), ferrous hydroxide (Fe(OH)2), ferric hydroxide (FeOOH), triiron tetroxide (Fe3O4), and ferric oxide (Fe2O3). Examples of cobalt-based catalysts include cobalt nitrate (Co(NO3)2·6H2O, Co(NO3)2), cobalt acetate (Co(CH3COO)2·4H2O, Co(CH3COO)2), cobalt carbonate (CoCO3), cobalt hydroxide (Co(OH)2, Co(OH)3), and cobalt oxide (CoO).

[0030] For example, the carbon material produced on the catalyst can be subjected to a predetermined treatment as needed to obtain, for example, carbon nanofibers, carbon nanotubes, carbon black (CB), etc., and carbon nanofibers or carbon nanotubes are particularly preferred because highly functional materials are expected to bring high profits (high added value).

[0031] Here, we will explain the production amount (production amount) of carbon material calculated from the reaction balance when producing carbon material using coke oven gas. As a prerequisite, the concentrations of hydrogen and methane in coke oven gas are assumed to be 60 vol% and 20 vol%, respectively. For example, 5 mol of coke oven gas contains 3 mol of hydrogen and 1 mol of methane.

[0032] - Reduction of carbon dioxide by coke oven gas (COG) (CO2 reduction process) CO2+ H2+ CH4→ CO + H2O ···(1) Here, 30 mol of CO2 reacts with 25 mol of COG (H2: 15 mol, CH4: 5 mol), producing 35 mol of CO and 25 mol of H2O.

[0033] Reduction of carbon monoxide by coke oven gas (COG) (carbon material manufacturing process) CO + H2+ CH4→ C + H2O ···(2) Here, 35 mol of CO produced by the above formula (1) reacts with 35 mol of COG (H2: 21 mol, CH4: 7 mol), producing 42 mol of C and 35 mol of H2O.

[0034] From the above equations (1) and (2), equation (3) is established. CO2+ COG → C + H2O ···(3) That is, when 30 mol of CO2 reacts with 60 mol of COG, 42 mol of C and 60 mol of H2O are produced.

[0035] Therefore, the following result is obtained from the above equation (3): CO2:COG = 1:2 CO2:C = 1:1.4 That is, in the method for producing a carbon material using coke oven gas of the present invention, a carbon material is produced from carbon dioxide, and by using an amount of coke oven gas that is twice the amount of carbon dioxide to be processed, the amount of carbon material produced can be increased by up to 1.4 times compared to when only carbon dioxide and hydrogen are used.

[0036] Hereinafter, examples and reference examples carried out to demonstrate the effect of the coke oven gas used in the method of the present invention will be described.

[0037] (carbon monoxide production) As shown in Figure 4(a), a granular catalyst was filled into a stainless steel tube (hereinafter referred to as SUS tube) to cover approximately one-third of the length of the electric tubular furnace and fixed in place with stainless steel wire (SUS wire). The catalyst used was an alumina-based catalyst. This SUS tube was then inserted into the electric tubular furnace.

[0038] Next, as shown in Figure 4(b), the air inside the SUS tube was replaced with nitrogen gas, and the SUS tube was heated to 300°C in a nitrogen atmosphere. Next, nitrogen and hydrogen were supplied into the SUS tube, and the SUS tube was heated at 300°C for 2 hours in this gas atmosphere. Next, reactive gases (CO2 and simulated COG) were flowed into the SUS tube, and the temperature was increased and the reaction was repeated in 100°C increments up to 700°C.

[0039] The gas concentration after the reaction at each reaction temperature (300°C, 400°C, 500°C, 600°C, 700°C) was measured by gas chromatography. Specifically, after heating to a specific temperature, the gas was sampled and measured by gas chromatography after waiting 30 minutes for stabilization. The test conditions and results are shown in Table 1.

[0040] [Table 1]

[0041] Tests a-1 to a-5 are the results (examples) of using carbon dioxide and a simulated COG with pre-adjusted composition (hydrogen: 58%, methane: 25%, carbon monoxide: 6%, nitrogen: 6%, ethane: 3%, carbon dioxide: 2%) as the reactive gas. From Table 1, it was confirmed that carbon monoxide can be generated by contacting carbon dioxide with simulated COG. In particular, it was confirmed that the amount of carbon monoxide generated can be increased as the reaction temperature increases.

[0042] (Manufacturing of carbon materials) The catalysts used were nickel-based and iron-based catalysts, which were reduced with hydrogen before use to ensure their reactivity.

[0043] The reaction gas was passed over the catalyst at high temperature to produce a carbon material on the catalyst. The procedure is as follows:

[0044] As shown in Figure 5(a), 30 mg of catalyst was weighed out and placed on a combustion boat in the center of a quartz tube, and the openings at both ends of the quartz tube were sealed with silicone plugs. After inserting this quartz tube into an electric tubular furnace, pipes were connected to the plugs sealing both ends of the quartz tube, allowing gas to be supplied to and discharged from the quartz tube.

[0045] Next, as shown in Figure 5(b), the air inside the quartz tube was replaced with nitrogen gas, and the quartz tube was heated to 500°C in a nitrogen atmosphere. Next, hydrogen gas was supplied into the quartz tube, and the quartz tube was heated to 500°C in a hydrogen atmosphere for 2 hours. Next, the hydrogen gas inside the quartz tube was replaced with nitrogen gas, and the temperature was raised to the reaction temperature in a nitrogen atmosphere. Then, the reaction gas was flowed into the quartz tube and the reaction was carried out for 1 to 3 hours. After that, the quartz tube was cooled down to approximately room temperature. Then, the quartz tube was removed from the electric tubular furnace, and the combustion boat was removed from inside the quartz tube, and the weight and shape of the catalyst that produced the carbon material were observed.

[0046] The weight was evaluated by calculating the amount of carbon produced per unit catalyst weight by subtracting the weight of the catalyst before the test from the weight of the catalyst that produced the carbon material. This carbon amount was then divided by the amount of catalyst. The test conditions and results are shown in Table 2.

[0047] [Table 2]

[0048] Tests b-1 and b-2 are results (comparative examples) in which carbon monoxide, hydrogen gas, and nitrogen gas were used as the reactive gases. Tests b-3 to b-6 are the results (reference examples) of using a simulated COG whose composition was adjusted in advance as the reaction gas (hydrogen: 58%, methane: 25%, carbon monoxide: 6%, nitrogen: 6%, ethane: 3%, carbon dioxide: 2%). Tests b-7 to b-10 are the results (examples) of using carbon monoxide and simulated COG as the reactive gas.

[0049] From Table 2, it was confirmed that when producing carbon material, using simulated COG produced a larger amount of carbon material than when carbon monoxide was brought into contact with hydrogen gas, and also that a larger amount of carbon material could be produced per unit weight of catalyst. The carbon material produced was carbon nanofiber. Furthermore, in the production of carbon materials, it was confirmed that carbon materials could be produced by contacting carbon monoxide with simulated COG, just as when carbon monoxide was contacted with hydrogen gas. The carbon materials produced were carbon nanofibers.

[0050] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the configurations described in the above embodiments and includes other embodiments and modifications that are conceivable within the scope of the claims. For example, the scope of the present invention also includes a case in which a method for producing carbon monoxide and carbon materials using coke oven gas of the present invention is configured by combining some or all of the above embodiments and modifications. [Industrial Applicability]

[0051] INDUSTRIAL APPLICABILITY The present invention is industrially useful because it enables carbon monoxide and carbon materials to be produced from carbon dioxide inexpensively and easily.

Claims

1. A method for producing a carbon material using coke oven gas, comprising reducing carbon dioxide with coke oven gas to produce carbon monoxide, and bringing the produced carbon monoxide into contact with the coke oven gas to produce a carbon material.

2. 2. The method for producing a carbon material using coke oven gas according to claim 1, wherein the carbon dioxide is exhaust gas generated from a coke oven.

3. 2. The method for producing a carbon material using coke oven gas according to claim 1, wherein a catalyst is used when carbon monoxide is brought into contact with the coke oven gas.

4. 4. The method for producing a carbon material using coke oven gas according to claim 3, wherein the catalyst is a nickel-based catalyst or an iron-based catalyst.

5. 2. The method for producing a carbon material using coke oven gas according to claim 1, wherein the produced carbon material is a carbon nanofiber or a carbon nanotube.

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