Heating system and heating method

Abstract

To provide a heating system that can suppress thermal runway from occurring, without additionally installing a facility such as piping.SOLUTION: A heating system 100, which heats a waste lithium ion battery A, comprises: a heat-treatment furnace 10 in which powder B constituted of at least any of calcium carbonate, limestone and dolomite is stored together with the waste lithium ion battery A; and heating means 12 that heats the heat-treatment furnace 10 so that an internal temperature in the heat-treatment furnace 10 is 400°C or higher and 650°C or lower.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heating system and method for heating an object to be heated, such as a discarded lithium ion battery. [Background technology]

[0002] Lithium-ion batteries are composed of a positive electrode material made of aluminum foil coated with lithium, cobalt, nickel, etc., a negative electrode material made of copper foil coated with graphite, electrolyte, separator, etc. Therefore, lithium batteries contain valuable materials such as lithium, cobalt, nickel, and copper. Therefore, recycling discarded lithium batteries and recovering these valuable materials is extremely beneficial for resource-poor Japan.

[0003] Waste lithium-ion batteries are difficult to process because they may ignite, cause electric shock, generate hydrogen fluoride, etc. during recycling. Therefore, waste lithium-ion batteries are rendered harmless by heating and roasting, and then separated and recovered by heating, crushing or pulverizing, sieving, sorting, etc.

[0004] However, since the electrolyte contained in waste lithium-ion batteries is an organic solvent equivalent to kerosene, if the amount of waste to be processed increases, a sudden rise in temperature could cause thermal runaway, which could damage the heating system equipment.

[0005] Therefore, for example, Patent Document 1 discloses a technology for adjusting the heating temperature by injecting at least one type of gas from among nitrogen gas, carbon dioxide, and water vapor into a thermal incinerator and venting the inside of the thermal incinerator when the heating temperature exceeds a predetermined temperature of 450°C or higher and 525°C or lower. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-159477 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the technology described in Patent Document 1 requires the installation of new equipment such as piping for feeding gas into the incinerator. In addition, when nitrogen gas or carbon dioxide is fed into the incinerator, the oxygen concentration around the incinerator decreases, which may cause oxygen deficiency.

[0008] An object of the present invention is to provide a heating system and a heating method that are capable of suppressing the occurrence of thermal runaway without the need to install new equipment such as piping. [Means for solving the problem]

[0009] The heating system of the present invention comprises: Waste lithium-ion batteries The heating system heats an object to be heated, and is characterized by comprising: a heat treatment device that accommodates at least one of calcium carbonate, limestone, and dolomite together with the object to be heated; and a heating means that heats the heat treatment device so that the internal temperature of the heat treatment device is 400°C or higher and 650°C or lower.

[0010] According to the heating system of the present invention, when the internal temperature of the heat treatment device rises suddenly to 700°C to 900°C due to some factor, at least one of calcium carbonate, limestone, and dolomite undergoes a decarbonation reaction. The endothermic heat and carbon dioxide gas generated by this reaction suppress combustion in the heat treatment device, and the internal temperature of the heat treatment device can be reduced. This suppresses the occurrence of thermal runaway, making it possible to protect the heating system.

[0011] This decarboxylation reaction automatically progresses when the internal temperature of the heat treatment device reaches 700° C. to 900° C. Therefore, unlike the technology described in Patent Document 1, there is no need to install new equipment such as piping for introducing gas into the heat treatment device when the temperature reaches a predetermined level or higher.

[0012] In the heating system of the present invention, the object to be heated is accommodated inside, and an insertion part that passes through the inside and the outside is formed. The heating system has a heat-resistant temperature of at least 700°C or more, Heat Treatment Equipment and a heat-resistant container that contains at least one of calcium carbonate, limestone, and dolomite and has a heat-resistant temperature of at least 700°C or higher, and a through-hole that passes through the inside and the outside of the container. Heat Treatment Equipment It is preferable that the processing vessel includes a processing vessel housed therein.

[0013] In this case, the material to be heated is contained separately in a heat-resistant container, and at least one of the calcium carbonate, limestone, and dolomite is contained separately in a treatment container, making it possible to optimize the arrangement and configuration of each container.

[0014] In the heating system of the present invention, at least one of the calcium carbonate, limestone, and dolomite is accommodated inside together with the object to be heated, and a through-hole is formed between the inside and the outside. The heating system has a heat-resistant temperature of at least 700°C or more, Heat Treatment Equipment It is also preferable to have a heat-resistant container housed inside the container.

[0015] In this case, since the object to be heated and at least one of calcium carbonate, limestone, and dolomite are contained in the same heat-resistant container, it is possible to reduce the number of containers contained in the heat treatment device.

[0016] Furthermore, in the heating system of the present invention, When the calcium carbonate or limestone is contained inside, the volume of the internal space of the heat treatment device is 1 m 3 Each container contains 1kg or more.

[0017] This Since the volume of the carbon dioxide gas generated by the decarbonation reaction of calcium carbonate or limestone is equal to or larger than the volume of the internal space of the heat treatment device, the carbon dioxide gas can fill the entire internal space of the heat treatment device, and the occurrence of thermal runaway is more reliably suppressed. When the dolomite is placed inside, the volume of the internal space of the heat treatment device is 1 m 3 Each container contains 1.9 kg or more. .

[0018] Heating method of the present invention teeth At least one of calcium carbonate, limestone, and dolomite is mixed with the waste lithium-ion battery to be heated. Heat Treatment Equipment The object is heated by heating the inside of the container to 400°C or more and 650°C or less while the object is contained therein. In the heating method, when the calcium carbonate or limestone is contained inside, the volume of the internal space of the heat treatment device is 1 m 3 When the dolomite is contained in the inside, the volume of the internal space of the heat treatment device is 1 m 3 Each container contains 1.9 kg or more. It is characterized by:

[0019] According to the heating method of the present invention, when the temperature of the space in which the object to be heated is heated suddenly rises to 700°C to 900°C due to some factor, at least one of calcium carbonate, limestone, and dolomite undergoes a decarbonation reaction. The endothermic heat and carbon dioxide gas generated by this reaction suppress combustion in the heat treatment device, and the temperature can be reduced. This suppresses the occurrence of thermal runaway, making it possible to protect the system that heats the object to be heated.

[0020] This decarbonation reaction automatically progresses when the internal temperature of the space reaches 700° C. to 900° C. Therefore, unlike the technology described in Patent Document 1, there is no need to install new equipment such as piping for introducing gas into the space when the temperature reaches a predetermined level or higher. [Brief description of the drawings]

[0021] [Figure 1] 1 is a schematic cross-sectional view showing a heating system according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a schematic cross-sectional view showing a heating system according to a second embodiment of the present invention. [Diagram 3] 1 is a graph showing changes in the internal temperature of the electric furnace in Test Examples 1 to 3 at high temperatures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, a heating system 100 according to a first embodiment of the present invention will be described with reference to Fig. 1. The heating system 100 is a device for heating an object to be heated. Note that Figs. 1 and 2 are diagrams for explaining the embodiment of the present invention in a schematic manner, and the dimensions are exaggerated.

[0023] Here, a case will be described in which the heating system 100 is a system for rendering the spent lithium ion batteries A, which are the object to be heated in the present invention, harmless by heating and roasting the spent lithium ion batteries A.

[0024] The heating system 100 is a processing device for processing waste lithium-ion batteries A, similar to, for example, the device described in the above Patent Document 1. Although not shown in detail, the heating system 100 includes a heat treatment furnace 10 and one or more heat-resistant containers 20 housed inside the heat treatment furnace 10 with the waste lithium-ion batteries A housed therein. Although not shown in the figure, the heating system 100 may include a container transport device for loading and unloading the heat-resistant containers 20 into and from the heat treatment furnace 10.

[0025] The heat treatment furnace 10 is, for example, a substantially cylindrical vertical furnace with furnace walls 11 made of steel plates covered with a fireproof material, and is heated by heating means 12 such as a gas burner. The heat treatment furnace 10 corresponds to the heat treatment device of the present invention. The internal temperature of the heat treatment furnace 10 is detected by a temperature sensor 13. Although not shown, the heat treatment furnace 10 is also provided with a door that is used when inserting and removing the heat-resistant container 20 and the storage container 30 into and from the internal space.

[0026] The hearth 14 of the heat treatment furnace 10 may be made of a steel plate covered with a refractory material, similar to the furnace wall 11, and may be configured to be rotatable in the horizontal direction by a hearth rotation device (not shown).

[0027] The heat treatment furnace 10 accommodates a plurality of heat-resistant containers 20, which are placed on the hearth 14 with a space between adjacent heat-resistant containers 20.

[0028] The shape of each heat-resistant container 20 is, for example, a box shape such as a rectangular parallelepiped, cubic, cylindrical, spherical, or elliptical sphere, and is not particularly limited. Here, the heat-resistant container 20 has a cylindrical shape as a whole, and one or more used lithium-ion batteries A are housed inside. The used lithium-ion batteries A may be housed in the heat-resistant container 20 in a stacked or overlapping manner.

[0029] The heat-resistant container 20 comprises a cylindrical main body 21 with an open top, a top lid 22 that is removably attached to the top of the main body 21, and an exhaust port 23 formed near the top of the top lid 22 or the main body 21.

[0030] The heat-resistant container 20 is configured to be capable of housing waste lithium-ion batteries A therein, and is made of stainless steel such as SUS304 taking into consideration processability, cost, etc. Any material may be used as long as it has a heat-resistant temperature of at least 700°C.

[0031] Further, in this embodiment, the heating system 100 includes a container 30 that contains at least one of calcium carbonate (CaCO3), limestone, and dolomite therein.

[0032] The storage container 30 stores therein powder B made of at least one of calcium carbonate, limestone made of calcium carbonate, and dolomite (hereinafter referred to as calcium carbonate powder, etc.). When calcium carbonate is heated to 700°C to 900°C, a decarbonation reaction proceeds while absorbing heat, as shown in the following reaction formula (1), and carbon dioxide gas is generated. CaCO3→CaO+CO2-178.23kJ / mol ··· (1)

[0033] When dolomite is heated to approximately 600°C, the calcium carbonate component undergoes an endothermic decarbonation reaction, as shown in reaction formula (1), producing carbon dioxide gas.

[0034] The shape of the storage container 30 is not particularly limited, and may be, for example, a box shape such as a rectangular parallelepiped, a cube, a cylinder, a sphere, an elliptical sphere, etc. The storage container 30 here has a cylindrical shape as a whole, and may be one consisting of only a main body with an open top, or may further include a top lid that is detachably attached to the top of the main body.

[0035] Moreover, the storage vessel 30 preferably has a heat resistance of at least 700° C. Taking into consideration workability, cost, and the like, the storage vessel 30 is preferably made of stainless steel, such as SUS304.

[0036] The container 30 has one or more, preferably many, through holes 31 formed therein, each having a diameter smaller than the particle size of the calcium carbonate or other powder B. The particle size of the calcium carbonate or other powder B is, for example, 3 mm to 10 mm.

[0037] In order to prevent calcium carbonate, etc. powder B from spilling out from the through-holes 31 when the storage container 30 containing calcium carbonate, etc. powder B is transported or installed in the heat treatment furnace 10, the diameter of the through-holes 31 is preferably smaller than the particle size of the calcium carbonate, etc. powder B. However, when the diameter is reduced by the reaction shown in reaction formula (1), the calcium carbonate, etc. powder B may spill out from the through-holes 31.

[0038] In addition, in order to eliminate the trouble of cleaning the calcium carbonate or other powder B that has spilled onto the hearth 14 of the heat treatment furnace 10, it is preferable that the through holes 31 are formed on the side and top surface, for example, other than the bottom surface of the storage container 30.

[0039] The amount of calcium carbonate or other powder B contained in the container 30 is set so that the carbon dioxide gas generated by the above reaction formula (1) fills the entire inside of the heat treatment furnace 10. In this case, when the calcium carbonate or other powder B is calcium carbonate or limestone, the amount of calcium carbonate or other powder B is set to 1 / m 2 of the internal space of the heat treatment furnace 10. 3 In addition, when the calcium carbonate powder B is dolomite, the amount of the calcium carbonate powder B is preferably 1 kg (about 10 mol) or more per 1 m of the internal space of the heat treatment furnace 10.3 It is preferable that the amount of the fluorine-containing compound is 1.9 kg (about 10 mol) or more per unit area.

[0040] The storage container 30 is preferably installed in the upper part inside the heat treatment furnace 10. This is because the carbon dioxide gas generated by the above reaction formula (1) is heavier than air, and since the intake port of the exhaust duct 41 described below is located in the lower part of the heat treatment furnace 10, the carbon dioxide gas tends to spread throughout the entire inside of the heat treatment furnace 10.

[0041] The storage container 30 may be installed such that its upper surface is in contact with the lower surface of the inner wall of the upper part of the heat treatment furnace 10, or may be installed with, for example, a gap therebetween. Furthermore, the method of installing the storage container 30 in the heat treatment furnace 10 is not limited. For example, the storage container 30 may be installed by installing a suspender on the inner wall of the upper part of the heat treatment furnace 10 and suspending the storage container 30 from the suspender. Furthermore, the storage container 30 may be installed by installing a shelf on the inner wall of the upper part of the heat treatment furnace 10 and placing the storage container 30 on the shelf.

[0042] The heating system 100 further includes an exhaust mechanism 40 for exhausting gas within the heat treatment furnace 10 to the outside. Here, the exhaust mechanism 40 is provided at the top of the heat treatment furnace 10 and includes an exhaust duct 41 that connects the inside and outside of the heat treatment furnace 10, and an exhaust fan 42 for exhausting gas within the heat treatment furnace 10 to the outside via the exhaust duct 41. The suction port of the exhaust duct 41 is preferably located below the bottom surface of the storage container 30, and more preferably located slightly above the exhaust port 23 of the heat-resistant container 20.

[0043] A heating system 200 according to a second embodiment of the present invention will be described below with reference to Fig. 2. This heating system 200 is similar to the above-mentioned heating system 100, so only differences from the heating system 100 will be described.

[0044] The heating system 200 includes a heat-resistant container 120 instead of the heat-resistant container 20 described above, and does not include the storage container 30 described above.

[0045] The heat treatment furnace 10 of the heating system 200 accommodates a plurality of heat-resistant containers 120 placed on the hearth 14 with a gap between adjacent heat-resistant containers 120 .

[0046] The shape of each heat-resistant container 120 is, for example, a box shape such as a rectangular parallelepiped, a cube, a cylinder, a sphere, or an oval sphere, and is not particularly limited. Here, the heat-resistant container 120 is generally cylindrical. The heat-resistant container 120 is made of stainless steel such as SUS304, and any material can be used as long as it has a heat-resistant temperature of at least 700°C.

[0047] Each heat-resistant container 120 comprises a cylindrical main body 121 with an open top, a top lid 122 that is removably attached to the top of the main body 121, and an exhaust port 123 formed near the top of the top lid 122 or the main body 121.

[0048] Furthermore, each heat-resistant container 120 is provided with a partition plate 124 in the middle in the height direction, which divides the internal space into upper and lower spaces. Powder B such as calcium carbonate is contained in the space below the partition plate 124, and one or more discarded lithium-ion batteries A are contained in the space above the partition plate 124.

[0049] The partition plate 124 has one or more through holes 125 formed therein, which penetrate vertically and have a diameter smaller than the particle size of the calcium carbonate or other powder B. The particle size of the calcium carbonate or other powder B is, for example, 3 mm to 10 mm.

[0050] Hereinafter, a heating method according to an embodiment of the present invention using the above-described heating system 100 or heating system 200 will be described.

[0051] First, as a preliminary process, the exhaust fan 42 is operated to perform a pre-purge in which residual gas in the heat treatment furnace 10 is discharged to the outside. After that, the inside of the heat treatment furnace 10 is heated by the heating means 12. The internal temperature of the heat treatment furnace 10 is increased while being monitored by the temperature sensor 13. Then, the operation of the heating means 12 and the like is controlled so that the internal temperature is kept constant at a predetermined heating temperature of 400°C or more and 650°C or less, for example, 650°C.

[0052] Next, in the heating system 100, the heat-resistant container 20 containing the waste lithium-ion batteries A and the storage container 30 containing the calcium carbonate or other powder B are placed at predetermined positions in the heat treatment furnace 10 through the door. The storage container 30 containing the calcium carbonate or other powder B may be placed in advance before the start of heating. In the heating system 200, the heat-resistant container 120 containing the waste lithium-ion batteries A and the calcium carbonate or other powder B is placed at a predetermined position in the heat treatment furnace 10 through the door.

[0053] Then, the operation of the heating means 12 and the like is continuously controlled so that the internal temperature of the heat treatment furnace 10 is kept constant at the predetermined heating temperature, for example, 650° C. This heats the waste lithium-ion batteries A. Note that the exhaust of gas present in the internal space of the heat treatment furnace 10 by operating the exhaust fan 42 may be performed as needed, periodically, or constantly.

[0054] This heating creates a reducing atmosphere inside the heat-resistant container 20, 120, and plastics such as the housings of the waste lithium-ion batteries A contained in the heat-resistant container 20, 120 are carbonized into a carbonized mixture by dry distillation, and are separated from materials containing useful metals such as lithium, cobalt, nickel, manganese, etc. The electrolyte in the waste lithium-ion batteries A is volatilized and discharged from the exhaust port 23 of the heat-resistant container 20 into the heat treatment furnace 10 together with gas generated by the thermal decomposition of combustible materials such as plastics, and is then discharged to the outside by the exhaust mechanism 40.

[0055] If the internal temperature of the heat treatment furnace 10 suddenly rises to 700°C to 900°C due to some factor, the powder B such as calcium carbonate undergoes a decarbonation reaction as shown in the above reaction formula (1). The endothermic heat and carbon dioxide gas generated by this reaction suppress combustion in the heat treatment furnace 10, and the internal temperature of the heat treatment furnace 10 can be reduced. This suppresses the occurrence of thermal runaway, making it possible to protect the heating systems 100 and 200.

[0056] The above reaction automatically proceeds when the internal temperature reaches 700° C. to 900° C. if the storage container 30 or the heat-resistant container 120 containing the calcium carbonate or other powder B is placed in the heat treatment furnace 10. Therefore, unlike the technique described in Patent Document 1, there is no need to provide new equipment such as piping for introducing gas into the heat treatment furnace 10 when the temperature reaches a predetermined level or higher.

[0057] The present invention is not limited to the above-mentioned embodiment. For example, in the above-mentioned embodiment, the case where the object to be heated is a waste lithium ion battery is described, but the object to be heated is not limited to this, and is not limited as long as it is heated at 400°C or more and 650°C or less. In addition, the heat treatment device of the present invention is not particularly limited, and a batch type furnace such as a fluidized bed furnace, a tunnel furnace, or a muffle furnace can be suitably used.

[0058] (Test Example) In a simulation of the above-mentioned heating system 200, a thermal runaway state was simulated, and a test was carried out to confirm whether or not there is an effect in preventing thermal runaway by storing powder B such as calcium carbonate in the heat-resistant container 120. This will be described below.

[0059] In this test, a resin sheet was used as the combustible material for generating thermal runaway instead of the waste lithium-ion battery A. This resin sheet was made of fluororesin, and was a rectangular sheet with a side length of 30 mm to 40 mm and a thickness of 0.5 mm to 2 mm, and 40 g of each was used in each test example.

[0060] Here, an electric furnace F0-510 manufactured by Yamato Scientific Co., Ltd. equipped with an exhaust hood was used instead of the heat treatment furnace 10. This electric furnace had inner dimensions of 300 mm in width, 250 mm in depth, and 140 mm in height, and an inner volume of 10.5 L.

[0061] A cylindrical stainless steel tube with a lid and a crucible were used to simulate the heat-resistant container 120. The stainless steel tube had an inner dimension of 70 mm in diameter and 135 mm in height, and an inner volume of 0.52 L. A 3 mm through hole was formed in the upper part of the stainless steel tube. The crucible had an inner dimension of 50 mm in diameter and 35 mm in height, and an inner volume of 0.05 L.

[0062] The test was carried out as follows. First, a thermocouple was installed on the top of the electric furnace. Then, the temperature of the electric furnace was increased until the internal temperature of the electric furnace, as indicated by the thermocouple, reached 900°C.

[0063] The stainless steel tube or crucible containing the resin sheet and calcium carbonate was placed inside an electric furnace with the internal temperature set to 900°C, and the door of the electric furnace was closed. The test conditions are summarized in Table 1. When the decarbonation reaction of 24 g of calcium carbonate was completed, 21 L of carbon dioxide gas was generated, which is twice the internal volume of the electric furnace.

[0064] The heater of the electric furnace was stopped 30 seconds after the door of the electric furnace was closed. Temperature measurement was continued until the internal temperature of the electric furnace became 400° C. or lower. The electric furnace was not forcibly ventilated.

[0065] [Table 1]

[0066] As can be seen from Fig. 3, which shows the transition of the internal temperature of the electric furnace at high temperatures in Test Examples 1 to 3, it is understood that the maximum internal temperature of the electric furnace is suppressed in Test Examples 2 and 3, in which calcium carbonate is contained in the stainless steel tube or crucible, compared to Test Example 1, in which calcium carbonate is not contained. This confirms that the inclusion of calcium carbonate is effective in suppressing thermal runaway. The elapsed time in Fig. 3 is the time elapsed from the time the door of the electric furnace was closed.

[0067] In addition, in Test Example 2 in which calcium carbonate was accommodated in a stainless steel tube, the degree of suppression of the maximum temperature inside the electric furnace was smaller than that in Test Example 3 in which calcium carbonate was accommodated in a crucible. This is presumably because the calcium carbonate in the stainless steel tube had a high concentration, and the decarbonation reaction of calcium carbonate did not proceed well. [Explanation of symbols]

[0068] 10...heat treatment furnace (heat treatment apparatus), 11...furnace wall, 12...heating means, 13...temperature sensor, 14...furnace bed, 20,120...heat-resistant container, 21,121...main body, 22,122...top cover, 23,123...exhaust port, 30...container, 31...through hole, 40...exhaust mechanism, 41...exhaust duct, 42...exhaust fan, 100,200...heating system, 124...partition plate, 125...through hole, A...waste lithium ion battery (object to be heated), B...powder such as calcium carbonate (powder consisting of at least one of calcium carbonate, limestone, and dolomite).

Claims

1. A heating system for heating a heated object which is a waste lithium-ion battery, A heat treatment device that accommodates at least one of calcium carbonate, limestone, and dolomite together with the object to be heated; a heating means for heating the heat treatment device so that an internal temperature of the heat treatment device is 400° C. or more and 650° C. or less; A heating system characterized in that, when the calcium carbonate or limestone is contained inside, an amount of 1 kg or more is contained per m3 of the volume of the internal space of the heat treatment device, and, when the dolomite is contained inside, an amount of 1.9 kg or more is contained per m3 of the volume of the internal space of the heat treatment device.

2. A heat-resistant container that contains the object to be heated and has a heat-resistant temperature of at least 700° C. or more and has an insertion part that passes through the inside and the outside, and is contained inside the heat treatment device; The heating system according to claim 1, further comprising a treatment container that contains at least one of the calcium carbonate, limestone, and dolomite inside, has a heat-resistant temperature of at least 700°C or more, and has an insertion part that passes through the inside and the outside, and is contained inside the heat treatment device.

3. The heating system according to claim 1, further comprising a heat-resistant container that contains at least one of the calcium carbonate, limestone, and dolomite together with the object to be heated, has a heat-resistant temperature of at least 700°C or more, and has an insertion part that passes through the inside and the outside, and is contained inside the heat treatment device.

4. A heating method for heating an object to be heated, which is a waste lithium-ion battery, by heating the inside of a heat treatment device to 400° C. or more and 650° C. or less in a state where at least one of calcium carbonate, limestone, and dolomite is accommodated inside the heat treatment device together with the object to be heated, the method comprising: A heating method characterized in that, when the calcium carbonate or limestone is contained inside, an amount of 1 kg or more per m3 of the volume of the internal space of the heat treatment device is contained, and, when the dolomite is contained inside, an amount of 1.9 kg or more per m3 of the volume of the internal space of the heat treatment device is contained.

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