Carbon capture method

Abstract

To provide a method for capturing carbon contained in an Al base scrap.SOLUTION: The present invention pertains to a carbon capture method comprising a heat treatment step of thermally decomposing an organic substance in an Al base scrap, and a collection step of bringing the Al base scrap containing a pyrolysis residue obtained by the heat treatment step into contact with a molten salt and taking at least a part of the carbon-containing substance contained in the pyrolysis residue into the molten salt. The method may further comprise a recovery step of obtaining an extract containing carbon from the molten salt or a solidified salt of the molten salt after the collection step. The Al base scrap is, for example, waste aluminum foil having a resin laminate layer. The carbon-containing substance may be, for example, graphite. A regeneration step of obtaining a recycled Al base material from the Al base scrap by heating the molten salt above the melting point of Al may also be performed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for capturing carbon from Al-based scrap. [Background technology]

[0002] There is a need to reduce carbon dioxide emissions, which are considered a cause of climate change. In addition, recycling of various resources is becoming important in order to reduce environmental impact and build a recycling-oriented society.

[0003] For example, the smelting of aluminum (Al) involves huge energy consumption and the generation of carbon dioxide (CO2). For this reason, the regeneration of Al from Al-based scrap (waste material) has been promoted. Many proposals for such recycling have been made, and for example, there are related descriptions in the following patent documents. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 60-230942 [Patent Document 2] Patent Publication 2012-21200 [Patent Document 3] Patent Publication No. 2014-94328 [Patent Document 4] Patent Publication No. 2007-54815 [Patent Document 5] Patent Publication 2017-20062 [Patent Document 6] Patent Publication No. 2016-121383 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, aluminum foil is recovered by dry distillation of aluminum laminate. However, it is difficult to separate the carbide from the aluminum foil by simple dry distillation alone.

[0006] In Patent Document 2, aluminum foil laminated packaging material and aluminum vapor deposition packaging material are treated at different dry distillation temperatures to recover metallic aluminum. However, there is no mention of by-products other than metallic aluminum.

[0007] In Patent Document 3, a packaging material in which an aluminum layer and a resin layer are laminated is heated in superheated steam to recover aluminum. However, the decomposition products (CO / CO2, etc.) of the resin layer are released into the atmosphere. Patent Document 4 simply proposes a recycling device that separates solid matter and oil smoke using superheated steam.

[0008] In Patent Document 5, roasted aluminum material obtained from used beverage cans (UBC) is put into a molten salt layer and the dissolved metal is recovered. In the case of roasting in an atmosphere where sufficient oxygen is supplied, ink and the like attached to the UBC are decomposed and CO2 and the like are exhausted (emitted to the atmosphere). In addition, such roasting increases the oxidation loss of Al. Incidentally, Patent Document 5 uses molten salt to which 10% by mass or more of cryolite (Na3AlF6) has been added in order to sufficiently dissolve the aluminum material in which oxidation has progressed.

[0009] Patent Document 6 merely proposes capturing lithium with a molten salt when recovering an aluminum-copper alloy from a lithium-ion secondary battery.

[0010] The present invention has been made in view of the above circumstances, and has an object to provide a carbon capture method and the like that has not been proposed heretofore. [Means for solving the problem]

[0011] As a result of intensive research into solving this problem, the inventor came up with the idea of ​​adding heat-treated Al-based scrap containing organic matter to molten salt to capture carbon-containing matter, and developed this idea to complete the present invention, which will be described later.

[0012] Carbon Capture Method (1) The present invention is a carbon capture method comprising: a heat treatment step of thermally decomposing organic matter in Al-based scrap; and a collection step of contacting a pyrolysis residue obtained by the heat treatment step with a molten salt to capture at least a portion of the carbon-containing material contained in the pyrolysis residue into the molten salt.

[0013] (2) According to the present invention, carbon-containing substances contained in the pyrolysis residue of organic matter attached to the Al-based scrap can be captured in the molten salt, which reduces the release of CO2 into the atmosphere due to the organic matter in the Al-based scrap.

[0014] Carbon-containing materials, etc. In the present invention, it is sufficient to capture at least a portion of the constituent element (C) of the organic matter in the Al-based scrap, and it is not essential to capture, collect, recover, etc., of the carbon-containing material produced in the process.

[0015] Of course, the present invention may be understood as such a carbon-containing material itself, or a manufacturing method or recovery method thereof, etc. For example, the present invention may include a recovery step of obtaining an extract containing carbon from the molten salt or the solidified salt of the molten salt after the collection step.

[0016] It should be noted that there is no difference (i.e., the presence or absence of alteration) between the components or structures of the carbon-containing material (including organic matter) before and after the heat treatment, extraction, or recovery. For example, organic matter containing H or O is usually pyrolyzed to become a different carbon-containing material. Also, at least a portion of the carbon-containing material contained in the pyrolysis residue (e.g., dry distillation product) can usually be extracted or recovered as it is. Examples of such carbon-containing materials include carbon compounds (carbides) and graphite.

[0017] 《Recycled Al base material, etc.》 Furthermore, the present invention may be understood as a recycled Al base material obtained from Al-based scrap or a manufacturing method thereof, etc. For example, the present invention may include a regeneration step of obtaining a recycled Al base material from Al-based scrap.

[0018] The recycled Al base material is made of, for example, pure Al or an Al alloy from which at least a portion of organic matter and carbon-containing matter has been removed. The recycled Al base material may be in a liquid phase (molten metal) or a solid phase (cast ingot (base metal), component, etc.). The molten salt suppresses oxidation and nitridation of the recycled Al base material, enabling efficient recovery of high-quality Al.

[0019] "others" Unless otherwise specified, "x to y" in this specification includes a lower limit of x and an upper limit of y. Any numerical value included in the various numerical values ​​or numerical ranges described in this specification may be used as a new lower limit or upper limit to create a new range such as "a to b." [Brief description of the drawings]

[0020] [Figure 1] 1 is a photograph showing an example of Al-based scrap after heat treatment. [Diagram 2] The photograph shows the solidified product (coagulated salt) of the molten salt that has incorporated the thermal decomposition residue from the Al-based scrap. [Diagram 3] This is a photograph showing the carbon-containing material recovered from the coagulation. [Figure 4] This is the X-ray diffraction pattern and composition table of the carbon content. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The above-mentioned components of the present invention may be supplemented with one or more components selected from the present specification. The contents described in the present specification may be either method-related components or components related to an object (e.g., an Al substrate, a carbide, etc.).

[0022] <Aluminum-based scrap> The raw material, Al-based scrap, is made of an Al base material containing organic matter.

[0023] The organic matter may be any matter containing C, regardless of its shape, number of molecules, molecular structure, etc. Examples of the organic matter include resins, papers, oils, etc. Specific examples include paints, inks, films, lubricating oils, processing oils, etc.

[0024] The Al substrate may be any substrate containing Al, and may have any component composition, form, etc. The Al substrate may be, for example, pure Al, an Al alloy, or a mixture thereof. The Al substrate may be in the form of a film, foil, fin, thin plate, granule, block, or the like.

[0025] The Al-based scrap may be an Al-based scrap with organic matter attached, coated, or pasted on the surface of the Al-based material, or may be an Al-based scrap with organic matter contained in the Al-based material or sandwiched or sandwiched between the Al-based materials. Specific examples include resin-laminated Al-based foil, resin-coated Al substrate (fin), printed or painted Al-based parts (packaging, container, housing, etc.).

[0026] The Al-based scrap is cut, broken, crushed, shredded, etc. into a desired shape (e.g., granules, foil pieces, fin pieces), etc. The Al-based scrap may be pretreated (degreased, etc.) before being subjected to the treatment of the present invention (heat treatment, contact with molten salt, recovery, etc.).

[0027] Molten Salt The molten salt is prepared, for example, by dissolving a stable metal halide (particularly, chloride and / or bromide). The metal element constituting the halide is, for example, one or more of Ca, Na, Li, Sr, K, Mg, Cs, Ba, etc. The halide of Na and / or K (particularly, chloride) is inexpensive and stable, and is suitable for the molten salt.

[0028] The molten salt may be a mixed salt containing a mixture of multiple metal halides (e.g., NaCl and KCl). The melting temperature, density, etc. may be adjusted by blending the molten salt (adjusting the components). The molten salt may have a lower density (specific gravity) than the Al base material (mainly Al), and the recycled Al base material may be allowed to settle and be recovered. The molten salt may be a single layer or multiple layers.

[0029] The molten salt should be able to separate and collect the carbon-containing material contained in the pyrolysis residue of the organic matter obtained after the heat treatment of the Al-based scrap from the Al base material. When the molten salt is heated to a temperature equal to or higher than the melting point of the Al base material (especially Al), the carbon-containing material becomes easy to separate from the Al base material. The Al base material also becomes easy to recover by being dissolved, coagulated, integrated, etc.

[0030] The amount of the molten salt may be adjusted depending on the amount of Al-based scrap to be processed after the heat treatment. The molten salt needs to be able to come into contact with the Al-based scrap after the heat treatment and capture the carbon-containing material, but it is also preferable that the molten salt has a depth (layer thickness) that allows the Al-based scrap to be immersed therein.

[0031] Processing method (1) Heat treatment process The heat treatment process is carried out by heating the Al base scrap (also simply called "scrap") in an atmosphere in which the organic matter in the scrap will not burn (for example, a low-oxygen atmosphere or a superheated steam atmosphere). As long as the organic matter can be heated without burning, any heating method (means) can be used, and the treatment atmosphere does not have to be a vacuum atmosphere or an inert gas atmosphere. Specific examples of the heat treatment process include carbonization, which is carried out by directly or indirectly heating the scrap in a furnace that is blocked from the inflow of oxygen and air, and a process in which the scrap is exposed to superheated steam and heated.

[0032] The organic matter subjected to the heat treatment (such as dry distillation) is usually thermally decomposed into non-volatile and volatile substances. The non-volatile substances remaining on the Al substrate become the pyrolysis residue referred to in the present invention, and the carbon-containing material is obtained from the pyrolysis residue. The volatile substances (such as water vapor) after the heat treatment are appropriately separated, removed, or discharged (exhausted).

[0033] The heating temperature (temperature inside the furnace) is, for example, a temperature at which the Al base material does not melt and the organic matter decomposes without burning. Although it depends on the type of organic matter, it is adjusted, for example, in the range of 350 to 650°C or 400 to 600°C. The carbonization atmosphere may be, for example, such that the oxygen concentration inside the furnace is about 0.1 to 10%, or 1 to 5%.

[0034] (2) Collection process When the heat-treated Al-based scrap is brought into contact with the molten salt, at least a portion of the carbon-containing material contained therein is separated from the Al base material and taken up in the molten salt. The form (addition, injection, etc.) of the supply of the heat-treated Al-based scrap to the molten salt (reservoir) does not matter, and the Al-based scrap may be supplied to the molten salt continuously or intermittently.

[0035] If the heat-treated Al-based scrap is granulated and used, the reaction with the molten salt is promoted, which may make it more efficient to extract carbon-containing materials and recover the Al substrate.

[0036] When the temperature of the molten salt is maintained above the melting point of the Al base material, the Al base material from which the carbon-containing material has been released dissolves in the molten salt and usually moves downward (for example, sinks to the bottom of the vessel) due to the difference in specific gravity with the molten salt. In this way, it is possible to obtain an Al-based molten metal (recycled Al base material) covered with molten salt from the scrap (recycle process). The Al-based molten metal may be supplied to another process as it is, or may be made into an ingot (base metal).

[0037] (3) Recovery process The carbon-containing material contained in the pyrolysis residue separated (liberated) from the Al-based scrap after the heat treatment may be left in the molten salt or may be further recovered. The recovered carbon-containing material may be utilized as it is, or may be regenerated by processing (heating, chemical reaction, etc.). The carbon-containing material may be recovered, for example, by filtering the molten salt as it is, or by filtering the residue obtained by washing the cooled solidified product of the molten salt (solidified salt, solid salt) with water, etc. EXAMPLES

[0038] The present invention will be described in more detail with reference to a specific example of recovering a carbon-containing material from Al-based scrap containing organic matter.

[0039] <Aluminum-based scrap> A scrap of laminate foil was prepared, in which both surfaces of an aluminum foil (Al base material) were covered with a resin layer (organic material). Measurements using an optical microscope revealed that the thickness of the aluminum foil was approximately 20 μm, and the thickness of each of the resin laminate layers was approximately 15 μm. The laminate foil was cut into strips (area of ​​one strip: approximately 1 to 15 cm2). 2 ) was used as the raw material (Aluminum-based scrap).

[0040] <Pyrolysis residue> The raw material was placed in a SUS304 stainless steel container and heated at 500°C for 15 minutes while blocking the inflow of air (heat treatment process). Gases (including water vapor) generated during heating were evacuated. The heat-treated product (dry distillation product) thus obtained is shown in Figure 1. As is clear from Figure 1, black substances (thermal decomposition residues) were attached to the surface of the aluminum foil.

[0041] Molten Salt Pool 1000 g of mixed chloride (KCl-44% by mass NaCl) was heated and dissolved in a graphite crucible to prepare a molten salt (800°C).

[0042] "process" (1) 780g of the dry distillate was added to the molten salt reservoir over a period of about 1 hour (feeding process), and then allowed to stand for about 5 minutes (collection process). As a result, the molten salt turned black and cloudy. Most of the molten metal settled to the bottom of the molten salt, and some of it was dispersed in the molten salt in the form of fine particles.

[0043] The molten salt was poured into a mold and allowed to cool and solidify in the air, resulting in the black solidified salt shown in Figure 2.

[0044] (2) Pure water was added to the coagulated salt to dissolve the chlorides, and the resulting aqueous solution was filtered (recovery step). The resulting residue (extract) is shown in Figure 3.

[0045] "analysis" (1) The residue was analyzed using an X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation). The resulting diffraction pattern is shown in Figure 4.

[0046] The residue was analyzed using an X-ray fluorescence analyzer (ZSX Primus II, manufactured by Rigaku Corporation). The obtained composition is also shown in Figure 4 (Table 1).

[0047] (2) As is clear from Figure 4, the residue mainly contained graphite (carbon-containing material), metallic aluminum, and aluminum oxide (Al2O3).

[0048] (3) Below the molten salt after the above-mentioned treatment (on the bottom side of the graphite crucible) was a molten metal (regenerated Al base material). This molten metal was cooled and solidified (regeneration process). The attached chlorides were washed away with water to obtain a metal lump (Al base metal) weighing approximately 715 g. The mass ratio (recovery rate) of this mass to the entire dry distillate was approximately 92%.

[0049] From the above, it was confirmed that the present invention can capture carbon contained in Al-based scrap.

Claims

1. a heat treatment step for pyrolyzing organic matter in the Al-based scrap; a collection step of contacting the pyrolysis residue obtained by the heat treatment step with a molten salt to incorporate at least a portion of the carbon-containing material contained in the pyrolysis residue into the molten salt; A carbon capture method comprising:

2. The carbon capture method according to claim 1 , further comprising a recovery step of obtaining an extract containing carbon from the molten salt or a solidified salt of the molten salt after the collection step.

3. 3. The carbon capture method of claim 2, wherein the extract comprises at least graphite.

4. The carbon capture method of claim 1 , wherein the organic matter comprises a resin.

5. 2. The carbon capture method of claim 1, wherein the molten salt is prepared by dissolving a chloride.

6. The carbon capture method according to claim 1 , wherein the molten salt in the collecting step is heated to a melting point of Al or higher.

7. The carbon capture method of claim 1 , wherein the heat treatment step is performed by dry distillation.

8. The carbon capture method according to claim 1 or 6, further comprising a regeneration step of obtaining a recycled Al substrate from the Al-based scrap.

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