Exhaust cylinder and gas carburizing furnace

Abstract

An exhaust cylinder (1) is for discharging exhaust gas (EG) discharged from a gas carburizing furnace (2). The exhaust cylinder (1) has a carbon recovery part (10) for reacting H2 and CO contained in the exhaust gas (EG) to generate C (11) and H2O, and recovering the generated C (11). The carbon recovery part (10) can be configured so as to be at a temperature of 450°C-700°C inclusive. The carbon recovery part (10) can have a catalyst that promotes the reaction of CO + H2 → C (s) + H2O. The gas carburizing furnace (2) has the exhaust cylinder (1).

Description

Exhaust stacks and gas carburizing furnaces CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2023-173847, filed on October 5, 2023, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to an exhaust stack and a gas carburizing furnace.

[0003] Conventionally, gas carburizing quenching is performed on steel parts such as automotive gears by heating them to high temperatures (approximately 950°C) to allow carbon (C) to penetrate the surface, followed by quenching in oil to induce martensitic transformation and improve wear resistance and fatigue strength. This gas carburizing quenching is performed using a gas carburizing furnace.

[0004] Generally, gas carburizing furnaces are fed with gas that has been converted in a conversion furnace. For example, the converted gas is a mixture of hydrocarbons (e.g., propane, butane, city gas, etc.) and air that is introduced into a conversion furnace filled with a catalyst such as a nickel catalyst heated to a high temperature (about 1050°C), and an endothermic reaction occurs to produce CO, H, etc. ２ , N ２ In addition to the converted gas, a few percent of enriched gases such as propane and butane may also be added to the gas carburizing furnace to adjust the equilibrium carbon concentration (CP).

[0005] Although the prior art document, Patent Document 1, does not relate to a gas carburizing furnace, it describes a technology for recovering carbon dioxide contained in exhaust gas emitted from a fuel cell by precipitating it as carbon through temperature control using hydrogen contained in the exhaust gas.

[0006] Patent No. 4227775

[0007] In the field of gas carburizing furnaces, the exhaust gas after gas carburizing is discharged through an exhaust pipe connected to the gas carburizing furnace. At this time, the exhaust gas flowing into the exhaust pipe from the gas carburizing furnace contains CO, H due to the converted gas. ２ , N ２Among these, CO cannot be released directly into the external environment. Therefore, from the viewpoint of environmental safety, currently, exhaust gas is burned at the outlet of the exhaust stack to convert CO into CO ２ In other words, conventional gas carburizing furnaces emit a large amount of CO from the exhaust pipe due to the atmospheric gases essential for carburizing. ２ are forced to be discharged.

[0008] The present disclosure has been made in view of such problems, and ２ The present invention provides an exhaust stack for a gas carburizing furnace that can suppress emissions, and a gas carburizing furnace that uses the same.

[0009] The exhaust stack and gas carburizing furnace according to the present disclosure are as follows.

[0010] [1] An exhaust pipe for discharging exhaust gas discharged from a gas carburizing furnace, the exhaust pipe comprising: CO and H contained in the exhaust gas; ２ By reacting with C and H ２ [2] The exhaust stack according to [1], wherein the carbon recovery section is configured to have a temperature of 450°C or higher and 700°C or lower. [3] The carbon recovery section is configured to recover CO+H ２ →C(s)+H ２ [4] The exhaust stack according to [1] or [2], which has a catalyst that promotes the reaction of O. [4] The exhaust gas supplied to the exhaust stack has a CO concentration <H ２ [5] The exhaust stack according to any one of [1] to [3], wherein the carbon recovery unit has solid particles. [6] The exhaust stack according to [5], wherein the solid particles are heat transfer particles. [7] The solid particles are a mixture of CO and H ２ →C(s)+H ２ The exhaust stack according to [5] or [6], which is a catalyst particle that promotes the reaction of O. [8] A gas carburizing furnace having the exhaust stack according to any one of [1] to [7].

[0011] The exhaust stack described in [1] above has the above configuration. Therefore, according to the exhaust stack described in [1] above, in the carbon recovery section provided in the exhaust stack, CO (carbon monoxide) and H contained in the exhaust gas supplied into the exhaust stack from the gas carburizing furnace are recovered. ２ (hydrogen) to produce C (solid carbon) and H ２ Therefore, with the above exhaust stack, the amount of CO reaching the gas outlet of the exhaust stack is reduced, and the amount of CO generated by burning the exhaust gas at the gas outlet of the exhaust stack is reduced. ２ Therefore, according to the exhaust stack described in [1] above, the amount of CO generated can be reduced compared to the conventional method. ２ It is possible to obtain an exhaust stack for a gas carburizing furnace that can suppress emissions.

[0012] In the exhaust stack described in [2] above, the carbon recovery section is configured to have a temperature of 450° C. or higher and 700° C. or lower. Therefore, in the exhaust stack described in [2] above, the exothermic reaction of CO + H ２ →C(s)+H ２ The reaction of O becomes easy to occur, and CO can be efficiently fixed as C. Therefore, according to the exhaust stack described in [2] above, in addition to the effect of the exhaust stack described in [2] above, ２ This makes it easier to control emissions.

[0013] In the exhaust stack described in [3] above, the carbon recovery section ２ →C(s)+H ２ Therefore, in the exhaust stack described in [3] above, the catalyst promotes the reaction of CO + H ２ →C(s)+H ２ The reaction of O is promoted, and CO can be efficiently fixed as C. Therefore, according to the exhaust stack described in [3] above, in addition to the effects of the exhaust stack described in [1] or [2] above, ２ This makes it easier to control emissions.

[0014] In the exhaust stack described in [4] above, the exhaust gas supplied to the exhaust stack has a CO concentration <H ２Therefore, in the exhaust stack described in [4] above, CO contained in the exhaust gas is condensed into a sufficient amount of H ２ Therefore, according to the exhaust stack described in [4] above, in addition to the effect of the exhaust stack described in any one of [1] to [3] above, when the exhaust gas is combusted at the gas outlet of the exhaust stack, the amount of CO generated by the unreacted CO can be reduced. ２ The occurrence of can be suppressed.

[0015] In the exhaust stack described in [5] above, the carbon capture section has solid particles. Therefore, in addition to the effects of the exhaust stack described in any one of [1] to [4] above, the exhaust stack described in [5] above further makes it easier to capture C by attaching C to the solid particles, and makes it easier to prevent C from flowing out downstream of the carbon capture section.

[0016] In the exhaust stack described in [6] above, the solid particles in the carbon recovery section are heat transfer medium particles. Therefore, according to the exhaust stack described in [6] above, the temperature of the exhaust gas supplied from the gas carburizing furnace can be actively lowered by increasing the chance of contact with the heat transfer medium particles. Therefore, in the exhaust stack described in [6] above, the exothermic reaction of CO + H ２ →C(s)+H ２ The reaction of O becomes easy to occur, and CO can be efficiently fixed as C. Therefore, according to the exhaust stack described in [6] above, in addition to the effect of the exhaust stack described in [5] above, ２ This makes it easier to control emissions.

[0017] In the exhaust stack described in [7] above, the solid particles in the carbon recovery section are CO + H ２ →C(s)+H ２ Therefore, according to the exhaust stack described in [7] above, the contact opportunity with the catalyst particles increases, and the reaction of CO + H ２ →C(s)+H ２The reaction of O is further promoted, and CO can be fixed more efficiently as C. Therefore, according to the exhaust stack described in [7] above, in addition to the effects of the exhaust stack described in [5] or [6] above, CO ２ This makes it easier to control emissions.

[0018] The gas carburizing furnace described in [8] above has an exhaust pipe described in any one of [1] to [7] above. Therefore, the gas carburizing furnace described in [8] above has a higher CO ２ A gas carburizing furnace capable of suppressing emissions can be obtained.

[0019] Fig. 1 is an explanatory diagram showing a schematic diagram of an exhaust stack according to embodiment 1 and a gas carburizing furnace using the same. Fig. 2 is an explanatory diagram showing a schematic diagram of an exhaust stack according to embodiment 2. Fig. 3 shows the relationship between the elapsed time (min) from the start of flowing the test gas and CO, CO ２ and C.H. ４ 4 is a graph showing the relationship between the time (min) elapsed since the start of flowing the test gas and the concentration (volume %) of H ２ Fig. 5 is a photograph of the state after steel wool was filled into the glass cylinder midway and test gas simulating exhaust gas was allowed to flow in Experimental Example 1. Fig. 6 is a graph showing the relationship between the elapsed time (min) from the start of flowing the test gas at each set temperature and the CO concentration (volume %) obtained in Experimental Example 2. Fig. 7 is a graph showing the relationship between the set temperature (°C) and the CO, CO ２ and C.H. ４ 8 is a graph showing the relationship between the set temperature (°C) and the concentration (volume %) of H at the end of the test, obtained in Experimental Example 2. ２ 9 is a graph showing the relationship between the concentration (volume %) of CO, CO ２ and C.H. ４ 10 is a graph showing the relationship between the internal temperature (°C) and the concentration (volume %) of H obtained in Experimental Example 2. ２Fig. 11 is a graph showing the relationship between the set temperature (°C) and the internal temperature rise (°C) obtained in Experimental Example 2. Fig. 12 is a graph showing the relationship between the elapsed time (min) from the start of the test gas flow and the CO, CO concentration (volume %) obtained in Experimental Example 2 when the set temperature was 450°C. ２ and C.H. ４ 13 is a graph showing the relationship between the concentration (volume %) of H and the time (min) elapsed since the start of the flow of the test gas when the set temperature was 450° C., obtained in Experimental Example 2. ２ Fig. 14 is a graph showing the relationship between the time (min) elapsed since the start of the test gas flow and the furnace set temperature, internal temperature (°C) and CO concentration (volume %) when the set temperature was 450°C, obtained in Experimental Example 2. Fig. 15 is a graph showing the relationship between the time (min) elapsed since the start of the test gas flow and the CO, CO concentration (volume %) when the set temperature was 500°C, obtained in Experimental Example 2. ２ and C.H. ４ 16 is a graph showing the relationship between the concentration (volume %) of H and the time (min) elapsed since the test gas started to flow when the set temperature was 500° C., obtained in Experimental Example 2. ２ Fig. 17 is a graph showing the relationship between the time (min) elapsed since the start of flowing the test gas and the temperature (°C) and CO concentration (volume %) when the set temperature was 500°C, obtained in Experimental Example 2. Fig. 18 is a graph showing the relationship between the time (min) elapsed since the start of flowing the test gas and the CO, CO concentration (volume %) when the set temperature was 550°C, obtained in Experimental Example 2. ２ and C.H. ４ 19 is a graph showing the relationship between the concentration (volume %) of H and the time (min) elapsed since the test gas started to flow when the set temperature was 550° C., obtained in Experimental Example 2. ２Fig. 20 is a graph showing the relationship between the time (min) elapsed since the start of flowing the test gas and the temperature (°C) and CO concentration (volume %) when the set temperature was 550°C, obtained in Experimental Example 2. Fig. 21 is a graph showing the relationship between the time (min) elapsed since the start of flowing the test gas and the CO, CO concentration (volume %) when the set temperature was 600°C, obtained in Experimental Example 2. ２ and C.H. ４ 22 is a graph showing the relationship between the concentration (volume %) of H and the time (min) elapsed since the test gas started to flow when the set temperature was 600° C., obtained in Experimental Example 2. ２ 23 is a graph showing the relationship between the elapsed time (min) from the start of flowing the test gas and the temperature (°C) and CO concentration (vol %) when the set temperature was 600°C, obtained in Experimental Example 2.

[0020] (Embodiment 1) An exhaust stack and a gas carburizing furnace according to embodiment 1 will be described below with reference to Fig. 1. Note that the exhaust stack and the gas carburizing furnace according to this embodiment are not limited to the following examples.

[0021] As shown in FIG. 1 , the gas carburizing furnace 2 of this embodiment has an exhaust stack 1 of this embodiment, which will be described later. The gas carburizing furnace 2 is a furnace that can be used not only for gas carburizing but also for gas carbonitriding. The gas carburizing furnace 2 is configured so that a modified gas MG is supplied into the furnace from a converter furnace (not shown). The converter furnace is configured so that a mixed gas of air and a hydrocarbon, such as propane, butane, or city gas, can be introduced, and the furnace is filled with a catalyst, such as a nickel catalyst. The converter furnace causes an endothermic reaction using a catalyst heated to a high temperature (for example, about 1050° C.), and converts the mixed gas into CO, H ２ , N ２ In this embodiment, the converted gas MG can be converted into a converted gas MG containing N ２ However, the modified gas MG contains N ２ It may not contain.

[0022] In this embodiment, the gas carburizing furnace 2 contains CO, H２ , N ２ In addition to the modified gas MG, the gas carburizing furnace 2 can also feed a few percent of enriched gas RG, such as propane or butane, to adjust the equilibrium carbon concentration (CP). The gas carburizing furnace 2 can carburize steel parts W, such as automotive gears, by maintaining the furnace at a predetermined temperature for an appropriate period of time in a gas atmosphere with the adjusted equilibrium carbon concentration (CP). The exhaust gas EG generated in the furnace has a temperature of, for example, about 900°C, and contains CO, H due to the composition of the modified gas MG. ２ , N ２ Contains:

[0023] 1, the exhaust tube 1 of this embodiment is for discharging the exhaust gas EG discharged from the gas carburizing furnace 2. In other words, the exhaust tube 1 can also be said to be an exhaust gas flow path member for discharging the exhaust gas EG.

[0024] The exhaust tube 1 is cylindrical, and a gas inlet at one end is configured to be connectable to an exhaust port 20 for exhaust gas EG in the gas carburizing furnace 2. The exhaust gas EG that flows inside the exhaust tube 1 is discharged to the outside from a gas outlet at the other end.

[0025] The exhaust stack 1 has a carbon recovery section 10. In this embodiment, the exhaust stack 1 has the carbon recovery section 10 at a location along the exhaust stack 1 from the gas inlet to the gas outlet. The carbon recovery section 10 recovers CO and H contained in the exhaust gas EG. ２ and react to produce C (solid carbon, soot) and H ２ In other words, the exhaust stack 1 is configured to convert CO+H into CO and recover the generated C11 in the carbon recovery section 10. ２ →C(s)+H ２ By causing a reaction of O, CO in the exhaust gas EG can be fixed as C.

[0026] According to the exhaust stack 1 of this embodiment, the amount of CO reaching the gas outlet of the exhaust stack 1 is reduced, and the amount of CO generated by burning the exhaust gas EG by the burner B or the like at the gas outlet of the exhaust stack 1 is reduced. ２ Therefore, according to the exhaust stack 1 of this embodiment, the amount of CO generated can be reduced compared to the conventional method. ２The exhaust stack 1 for a gas carburizing furnace can be obtained, which can suppress CO emissions. ２ It is possible to obtain a gas carburizing furnace 2 capable of suppressing CO emissions. Furthermore, with the exhaust stack 1 of this embodiment, it is possible to remove the existing exhaust stack of a conventional gas carburizing furnace and install the exhaust stack 1 of this embodiment. Therefore, it is possible to reduce CO emissions by simply replacing the exhaust stack 1 without changing the main body of the existing gas carburizing furnace. ２ The exhaust gas EG discharged from the gas outlet of the exhaust stack 1 may contain CO as long as the amount of CO is reduced compared to conventional methods. Of course, the exhaust gas EG discharged from the gas outlet of the exhaust stack 1 may have CO completely removed. In addition, the exhaust gas EG discharged from the gas outlet of the exhaust stack 1 may contain H ２ , N ２ , H ２ It may contain components such as O.

[0027] In the exhaust stack 1 of this embodiment, at least CO + H ２ →C(s)+H ２ If the reaction of O can occur, other reactions can occur, such as 2CO → C(s) + CO ２ , CO ２ +H ２ →CO+H ２ O, CO ２ +2H ２ → C(s) + 2H ２ O, reactions caused by the enriched gas RG used in combination with the modified gas MG, etc. ４ H １０ If it contains ４ H １０ →C(s) + C ３ H ８ +H ２ Similarly, the reaction of C ３ H ８ If it contains ３ H ８ →C(s) + C ２ H ６ +H ２ Reaction of C ２ H ６If it contains ２ H ６ →C(s) + CH ４ +H ２ The reaction of CH ４ If it contains CH ４ → C(s) + 2H ２ , C.H. ４ +CO ２ → 2CO + 2H ２ , C.H. ４ +H ２ O → CO + 3H ２ Reactions such as:

[0028] In the exhaust stack 1 of this embodiment, the carbon recovery unit 10 recovers CO and H contained in the exhaust gas EG. ２ C and H by reaction with ２ It is sufficient that the composition is capable of promoting the generation of O.

[0029] For example, the exhaust stack 1 is configured to generate CO + H in the carbon recovery section 10. ２ →C(s)+H ２ The temperature of the carbon recovery section 10 can be adjusted so that the reaction of CO + H O occurs easily. Specifically, the exhaust stack 1 actively lowers the temperature of the exhaust gas EG discharged from the gas carburizing furnace 2 between the gas inlet of the exhaust stack 1 and the carbon recovery section 10, and the temperature of the exhaust gas EG is used to ２ →C(s)+H ２ In this configuration, the temperature of the exhaust gas EG can be adjusted by, for example, adjusting the amount of heat insulating material disposed around the outer periphery of the exhaust stack 1. In addition, in order to adjust the temperature of the exhaust gas EG, heating by a heating means such as a heater may be added. Alternatively, without heating by a heating means, the heat of the exhaust gas EG may be used to react with CO+H ２ →C(s)+H ２ When the temperature is adjusted to a range that allows the reaction of O to occur, no extra energy is required, and the energy efficiency of the gas carburizing furnace 2 can be improved.

[0030] More specifically, the carbon recovery unit 10 is preferably configured to have a temperature of 450° C. or higher and 700° C. or lower. In this case, the exothermic reaction of CO+H２ →C(s)+H ２ This makes it easier for the reaction of O to occur, and CO can be efficiently fixed to C, so CO ２ This makes it easier to suppress emissions. The temperature of the carbon recovery section 10 is preferably 450°C or higher in order to promote the above reaction, more preferably 500°C or higher, and even more preferably 550°C or higher. The temperature of the carbon recovery section 10 is preferably 700°C or lower in order to further promote the reaction and increase carbon recovery efficiency, more preferably 680°C or lower, and even more preferably 650°C or lower. The temperature of the carbon recovery section 10 is the internal temperature of the exhaust stack 1 in the region where the carbon recovery section 10 is provided.

[0031] For example, the exhaust stack 1 has a carbon recovery unit 10 that recovers CO + H ２ →C(s)+H ２ In this configuration, the carbon recovery unit 10 may be configured to have a catalyst that promotes the reaction of CO + H ２ →C(s)+H ２ The reaction of O is promoted, and CO can be efficiently fixed as C, and further CO ２ This makes it easier to control emissions.

[0032] Suitable catalysts include iron-based catalysts, cobalt-based catalysts, and molybdenum-based catalysts. Here, iron-based catalysts refer to catalysts composed of a material containing 50% or more by weight of iron itself, or a material in which such a material is supported on a ceramic or other carrier. Cobalt-based catalysts refer to catalysts composed of a material containing 50% or more by weight of cobalt itself, or a material in which such a material is supported on a ceramic or other carrier. Molybdenum-based catalysts refer to catalysts composed of a material containing 50% or more by weight of molybdenum itself, or a material in which such a material is supported on a ceramic or other carrier. These catalysts can be used alone or in combination. From the perspective of ensuring gas permeability, the catalyst is preferably in a fibrous or particulate form. Specific examples of catalysts include steel wool, iron particles, Co particles, Mo particles, or at least one of these metal particles supported on a ceramic or other carrier. These catalysts can be used alone or in combination. Of these, steel wool is preferred from the perspective of catalytic activity, gas permeability, and the like.

[0033] In addition, when the carbon recovery unit 10 is configured so that the temperature is in the above-mentioned temperature range and the carbon recovery unit 10 has the above-mentioned catalyst, the synergistic effect of the temperature optimization and the catalyst can be achieved, resulting in a reduction in CO + H ２ →C(s)+H ２ The reaction of O is further promoted, CO can be fixed as C more efficiently, and CO ２ This makes it easier to control emissions.

[0034] In the exhaust stack 1 of this embodiment, the exhaust gas EG supplied to the exhaust stack 1 has a CO concentration <H ２ In this case, it is preferable that the CO contained in the exhaust gas EG is condensed by a sufficient amount of H ２ Since the amount of unreacted CO can be reduced, when the exhaust gas EG is combusted at the gas outlet of the exhaust stack 1, the amount of unreacted CO can be reduced. ２ It is possible to suppress the occurrence of CO concentration <H ２ The exhaust gas that satisfies the concentration relationship is CO ２ , O２ , H ２ This can be adjusted by controlling the composition of the gas, such as O, introduced into the reforming furnace.

[0035] The exhaust gas EG supplied to the exhaust stack 1 specifically contains, for example, 18% by volume or more and less than 50% by volume of CO, ２ 28% by volume or more and 70% by volume or less, N ２ It may contain 0% by volume or more and 50% by volume or less.

[0036] In the exhaust stack 1 of this embodiment, the carbon capture section 10 can be configured to have solid particles (not shown). With this configuration, C can be easily captured by adhering to the solid particles, and it is easier to prevent C from flowing out downstream of the carbon capture section.

[0037] In the exhaust stack 1 of this embodiment, the carbon capture unit 10 can be configured to have, for example, a fluidized bed (not shown) for suspending solid particles in the exhaust gas EG. The fluidized bed is also sometimes referred to as a fluidized bed. Specifically, the fluidized bed can suspend solid particles in the exhaust gas EG by, for example, ejecting the exhaust gas EG in the direction opposite to the vertical direction in the carbon capture unit 10, i.e., upward. When the carbon capture unit 10 has a fluidized bed (not shown), C can be easily captured in the fluidized bed by, for example, capturing C in the solid particles, and the outflow of C downstream of the carbon capture unit 10 can be more easily suppressed.

[0038] Specifically, the solid particles can be composed of heat transfer medium particles, catalyst particles, etc. The heat transfer medium particles are particulate heat transfer mediums that can transfer heat between the exhaust gas EG and the heat transfer medium. The catalyst ... ２ →C(s)+H ２ When the solid particles are heat transfer medium particles, the temperature of the exhaust gas EG supplied from the gas carburizing furnace 2 can be actively lowered by increasing the contact opportunity with the heat transfer medium particles, and the exothermic reaction of CO + H ２ →C(s)+H ２This facilitates the reaction of CO with O, making it possible to efficiently fix CO as C. Furthermore, if the solid particles are catalyst particles, the increased chance of contact with the catalyst particles increases the reaction rate of CO + H ２ →C(s)+H ２ The reaction of O is further promoted, and CO can be fixed as C more efficiently.

[0039] In addition to the fluidized bed configuration, the exhaust stack 1 of this embodiment can also be configured such that, for example, a fixed catalyst bed is provided in the carbon recovery section 10, and C produced in the fixed catalyst bed is separated and recovered using a vibrating screen, a dust collector mechanism, etc. Recovery of C from the carbon recovery section 10 may be carried out by either a continuous method or a batch method.

[0040] (Embodiment 2) An exhaust stack and a gas carburizing furnace according to embodiment 2 will be described with reference to Fig. 2. Note that, among the reference symbols used in embodiment 2 and subsequent embodiments, the same reference symbols as those used in the previous embodiments represent the same components as those in the previous embodiments, unless otherwise specified.

[0041] 2, the exhaust stack 1 of this embodiment has a carbon recovery unit 10, similar to the exhaust stack 1 of the first embodiment. The carbon recovery unit 10 recovers CO and H contained in the exhaust gas EG supplied from the gas inlet of the exhaust stack 1. ２ and react to produce C (solid carbon) and H ２ In this embodiment, the carbon capture unit 10 has a catalyst layer 101 fixed to a midpoint of the exhaust stack 1. The catalyst layer 101 may contain, for example, a catalyst having a fibrous or particulate shape as described above. The catalyst in the catalyst layer 101 may be fixed to a predetermined position within the exhaust stack 1 by a retaining member (not shown) such as a pressing member. The exhaust stack 1 of this embodiment is configured so that the exhaust gas EG supplied from the side of the exhaust stack 1 flows from below to above the exhaust stack 1. The carbon capture unit 10 is disposed in a midpoint of the flow path through which the exhaust gas EG flows from below to above within the exhaust stack 1.

[0042] In this embodiment, the exhaust stack 1 has a discharge mechanism 102 for recovering C from the catalyst layer 101 that has recovered C in the carbon recovery unit 10 and discharging the C to the outside of the exhaust stack 1. According to this configuration, the discharge mechanism 102 can recover C11 recovered in the carbon recovery unit 10 by discharging it to the outside with a relatively simple configuration.

[0043] Specifically, as illustrated in Figure 2, the discharge mechanism 102 can be configured to have a storage section 102a that is provided below the carbon recovery section 10 and temporarily stores C11 that has fallen from the carbon recovery section 10, a discharge section 102c that is provided below the storage section 102a and sends C11 that flows in from the storage section 102a downward, a receiving section 102e that is provided below the discharge section 102c and receives C11 that has been discharged from the discharge section 102c, an upper shutter section 102b that separates the storage section 102a and the discharge section 102c in an openable / closable manner, and a lower shutter section 102d that separates the discharge section 102c and the receiving section 102e in an openable / closable manner.

[0044] According to this configuration, C11 that has fallen out of the carbon capture unit 10 and fallen freely is stored in the storage unit 102a. When the upper shutter unit 102b is changed from a closed state to an open state, C11 flows from the storage unit 102a into the discharge unit 102c. C11 that has flowed into the discharge unit 102c is transported to the lower shutter unit 102d. In this embodiment, the discharge unit 102c has a rotating blade 102f therein, and as the rotating blade 102f rotates, C11 is transported from near the upper shutter unit 102b to the lower shutter unit 102d. When the lower shutter unit 102d is changed from a closed state to an open state, C11 falls downward from the discharge unit 102c and is received by the receiving unit 102e. According to this configuration, by utilizing the dropping of C11 from the carbon capture section 10 and falling down the exhaust stack 1, C (solid carbon) 11 generated in the carbon capture section 10 can be separated from the carbon capture section 10 and discharged to the outside for recovery with a simple configuration. ２ O (not shown) may be included.

[0045] In the above, the upper shutter portion 102b and the lower shutter portion 102d may be configured to be opened and closed manually or automatically. Furthermore, as illustrated in FIG. 2, the exhaust stack 1 may be provided with a heating element 103 for adjusting the temperature of the carbon capture unit 10 on the outer periphery of the exhaust stack 1 where the carbon capture unit 10 is located. Furthermore, from the viewpoint of recovery efficiency, it is preferable that the generated C11 be configured to be continuously separated and recovered. Other configurations and effects are the same as those of the exhaust stack 1 of the first embodiment.

[0046] The gas carburizing furnace 2 of this embodiment has the exhaust stack 1 of this embodiment. Other configurations and effects are the same as those of the gas carburizing furnace 2 of the first embodiment.

[0047] (Experimental Example 1) A straight glass cylinder with a diameter of 70 mm was prepared to simulate an exhaust pipe for discharging exhaust gas from a gas carburizing furnace. Next, a region filled with steel wool as a catalyst to a height of 50 mm was formed in the middle of the glass cylinder. Next, this glass cylinder was installed so that the cylindrical axis direction of the glass cylinder was vertical. Next, a test gas simulating a metamorphic gas was flowed from the bottom opening of the glass cylinder to the top opening of the glass cylinder. In this experimental example, CO, H ２ , and N ２ The main components of the gas were CO, H, and ２ , and N ２ The total volume percentage of the test gas is 50% or more by volume. ２ : 32% by volume, N ２ : 41 vol%, CH ４ The mixed gas contained 2% by volume of CI 2.25. The mixed gas was supplied at 2 L / min. In this experimental example, the internal temperature of the glass cylinder was controlled to 600°C by heating with a heater installed on the outer periphery of the glass cylinder. Next, the proportions of the components in the test gas discharged from the upper opening of the glass cylinder were measured after a predetermined time had elapsed since the test gas began to flow.

[0048] FIG. 3 shows the relationship between the elapsed time (min) from the start of flowing the test gas and the CO, CO２ and C.H. ４ The relationship between the concentration (volume %) of H and the time (min) elapsed since the test gas started to flow is shown in FIG. ２ The relationship between the concentration (volume %) and the dew point (°C) is shown. Figure 5 shows the state after steel wool was filled into the glass cylinder midway and a test gas simulating exhaust gas was flowed through it. The internal temperature of the glass cylinder was controlled to be 600°C when the test gas was flowed through it. In Figure 5, the symbol Y indicates the flow direction of the test gas, symbol 10a indicates the steel wool, and symbol 11a indicates the soot (carbon) attached to the steel wool.

[0049] As shown in Figure 3, the CO content decreased as the time elapsed since the start of the test gas flow increased. Specifically, the CO content decreased from 25% by volume to 17% by volume. Also, as shown in Figure 4, the H ２ As with CO, the dew point decreased as the time elapsed since the test gas began to flow increased. Furthermore, as shown in Figure 4, the dew point (the moisture content) increased as the time elapsed since the test gas began to flow increased. Furthermore, as shown in Figure 5, soot was generated on the steel wool.

[0050] According to the above results, the CO and H contained in the test gas supplied into the glass cylinder ２ and react to produce C (solid carbon) and H ２ O, that is, CO + H ２ →C(s)+H ２ By causing a reaction of O with O, it can be said that CO in the exhaust gas can be fixed to C at the midpoint of the tube. In addition, since the amount of CO reaching the gas outlet of the glass tube is reduced, the CO generated by burning the exhaust gas at the gas outlet of the glass tube can be reduced. ２ Therefore, according to the results of this experiment, the amount of CO generated can be reduced compared to the conventional method. ２ It was confirmed that it is possible to obtain an exhaust stack for a gas carburizing furnace and a gas carburizing furnace that can suppress emissions.

[0051] In addition, the above-mentioned CO + H ２ →C(s)+H ２Standard Gibbs energy change ΔrG in the reaction of O ０ / J is −24,920.60 at 500°C, −10,609.50 at 600°C, 3,724.60 at 700°C, and 18,066.90 at 800°C.

[0052] In this experimental example, steel wool was used as a catalyst. However, other than steel wool, CO + H ２ →C(s)+H ２ It is possible to use other catalysts that can promote the reaction of CO + H in the carbon recovery section without using a catalyst. ２ →C(s)+H ２ The gas temperature may be adjusted so that the exothermic reaction of O actively occurs. Furthermore, C can be recovered in the carbon recovery section by adhering it to a catalyst disposed in the carbon recovery section, to a collector disposed in the carbon recovery section for capturing C, or to the inner wall surface of the exhaust stack (carbon recovery section). The collector may be a catalyst or a heat transfer medium.

[0053] (Experimental Example 2) The experimental results of Example 1 revealed that steel wool functions as a catalyst, soot is generated on the steel wool, and the reaction is accelerated as the soot is generated. This is thought to be due to the catalytic effect of the soot itself. Therefore, in this example, the temperature was set to 450°C, 500°C, 550°C, and 600°C, and the gas components after the reaction were held for a long time until they reached equilibrium, and the changes in each gas were investigated. The results of this investigation are described below. The test gas used in this experimental example was the same as that used in Experimental Example 1.

[0054] Figure 6 shows the relationship between the elapsed time (min) from the start of the test gas flow at each set temperature and the CO concentration (volume %). Note that the set temperature refers to the set temperature of the heater installed on the outer periphery of the glass cylinder and is different from the actual internal temperature inside the glass cylinder. As shown in Figure 6, the time until the CO reaction reached equilibrium was shortest when the set temperature was 550°C, followed by 600°C and 500°C.

[0055] It can be seen that when the set temperature was 550°C, equilibrium was not reached even after 6 hours. The portion shown in A of Figure 6 is due to the replacement of the cylinder due to a lack of gas. When the set temperature was 550°C, clogging of the steel wool due to soot adhesion occurred during the test, as shown in B of Figure 6, and the steel wool shifted in position. From this, it was confirmed that when generating C in the carbon capture section for a relatively long period of time, it is effective to hold the catalyst with a holding member to prevent catalyst displacement, or, when using a fibrous catalyst, to optimize the mesh size to prevent clogging due to the generated soot.

[0056] Figure 7 shows the relationship between the set temperature (°C) and CO ２ and C.H. ４ The relationship between the set temperature (°C) and the concentration (volume %) of H at the end of the test is shown in Figure 8. ２ The relationship between the concentration (volume %) and the internal temperature is shown in Figure 9. ２ and C.H. ４ The relationship between the internal temperature (°C) and the concentration (volume %) of H ２ 11 shows the relationship between the set temperature (°C) and the internal temperature rise (°C).

[0057] 7 and 9, it was confirmed that the temperature range in which CO decomposition was greatest after equilibrium was 500 to 550°C in set temperature, that is, 550 to 580°C in internal temperature. ２ It was confirmed that the temperature range in which the decomposition of CO + H is greatest is a set temperature of 550 to 600°C, that is, an internal temperature of 580 to 630°C. Also, according to Figure 11, it can be seen that the internal temperature rise is greatest when the set temperature is 500°C or 550°C. This is because the decomposition of CO + H ２ →C(s)+H ２ This is thought to be due to the frequent occurrence of an exothermic reaction of O.

[0058] From the above results, CO + H ２ →C(s)+H ２It is understood that in order to further promote the reaction of O, it is particularly effective to set the temperature of the carbon recovery section in the exhaust stack to 550°C or higher and 650°C or lower.

[0059] 12 to 23 show detailed data of the test results at the respective set temperatures of 450°C, 500°C, 550°C, and 600°C. As mentioned above, the portion indicated by A in Figs. 15 to 17 is due to the replacement of the cylinder due to a gas shortage. During this period, N was used instead of the test gas. ２ 18 to 20 show the time when clogging of the steel wool due to the adhesion of soot occurred and the steel wool became misaligned.

[0060] The present disclosure is not limited to the above-described embodiments and experimental examples, and various modifications are possible without departing from the spirit and scope of the present disclosure. Furthermore, the configurations shown in the above-described embodiments and experimental examples can be combined in any manner.

Claims

1. An exhaust pipe for discharging exhaust gas discharged from a gas carburizing furnace, the exhaust pipe containing CO and H ２ React with C and H ２ The exhaust stack has a carbon recovery section for recovering the produced C and O.

2. The exhaust stack according to claim 1, wherein the carbon recovery section is configured to have a temperature of 450°C or higher and 700°C or lower.

3. The carbon recovery section is CO + H ２ →C(s)+H ２ The exhaust stack of claim 1 or 2, comprising a catalyst for promoting the reaction of O.

4. The exhaust gas supplied to the exhaust stack has a CO concentration <H ２ The exhaust stack according to claim 1 or 2, which satisfies a concentration relationship.

5. An exhaust stack as claimed in claim 1 or 2, wherein the carbon capture section comprises solid particles.

6. The exhaust stack according to claim 5, wherein the solid particles are heat transfer medium particles.

7. The above solid particles are CO + H ２ →C(s)+H ２ The exhaust stack of claim 5, wherein the catalyst particles are catalyst particles that promote the reaction of O.

8. A gas carburizing furnace having an exhaust stack according to claim 1 or 2.

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