Method for thermal decomposition treatment of water-containing organic waste

Abstract

To provide a new technical means capable of treating water-containing organic waste.SOLUTION: (1) A method for thermally decomposing water-containing organic waste, comprising the step of heating the water-containing organic waste in the presence of an alkali metal compound.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This patent application claims priority to Japanese Patent Application No. 2024-127749, filed on August 2, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to a method for pyrolytically treating aqueous organic waste. [Background technology]

[0003] It is known that the treatment of wet organic waste requires a high amount of energy up to the final disposal stage. For example, food waste, which accounts for approximately 40% by mass of wet organic waste, is mostly disposed of by incineration (generally at high temperatures of 800°C or higher), which requires a high level of energy. Incineration of wet organic waste (e.g., food waste) poses problems, such as the large amount of energy required. For this reason, alternative methods for treating wet organic waste are being investigated.

[0004] For example, Patent Document 1 proposes a method for treating water-containing organic waste by methane fermentation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-220087 Summary of the Invention

[0006] The method proposed in Patent Document 1 is based on methane fermentation and therefore requires special equipment, which limits its application.

[0007] Therefore, one object of the present disclosure is to provide a new technical means capable of treating aqueous organic waste.

[0008] The present inventors have found that water-containing organic waste can be decomposed by heating it in the presence of an alkali metal compound. The present disclosure is based on this finding.

[0009] According to one embodiment of the present disclosure, (1) A step of heat treating the aqueous organic waste in the presence of an alkali metal compound A method for pyrolysis treatment of aqueous organic waste, comprising: is provided.

[0010] According to the present disclosure, it is possible to provide a new technical means capable of treating aqueous organic waste. [Brief explanation of the drawings]

[0011] [Figure 1] 1 shows the appearance of the sample used in the examples. [Figure 2] The residual ratios of residues obtained in Examples 1 to 5 and Reference Example 1 are shown. [Figure 3] The amounts of phosphorus in the filtrates obtained in Examples 1 to 5 and Reference Example 1 are shown below. [Figure 4] The amounts of hydrogen, methane, carbon monoxide and carbon dioxide recovered in Examples 1 to 5 and Reference Example 1 are shown. [Figure 5] The amounts of hydrogen and methane recovered in Example 6 are shown. [Figure 6] The appearance, residual rate, etc. of the residue obtained in Example 2 are shown below. [Figure 7] The appearance, residual rate, etc. of the residue obtained in Example 3 are shown below. [Figure 8] The appearance, residual rate, etc. of the residue obtained in Example 4 are shown below. [Figure 9] The appearance, residual rate, etc. of the residue obtained in Example 5 are shown below. [Figure 10] The appearance, residual rate, etc. of the residue obtained in Example 6 are shown below. [Figure 11] The appearance, residual rate, etc. of the residue obtained in Example 7 are shown below. Specific Description of the Invention

[0012] According to one embodiment of the present disclosure, (1) A step of heat treating the aqueous organic waste in the presence of an alkali metal compound A method for pyrolysis treatment of aqueous organic waste, comprising: is provided.

[0013] According to one embodiment of the present disclosure, the use of an alkali metal compound is advantageous in that it may be possible to decompose and treat aqueous organic waste at a lower temperature than conventional incineration. Furthermore, according to one embodiment of the present disclosure, the use of an alkali metal compound is advantageous in that it may be possible to decompose, gasify, or otherwise process a portion or substantially all of the aqueous organic waste. Furthermore, according to a preferred embodiment of the present disclosure, it is particularly advantageous in that it may also be possible to suppress the generation of carbon monoxide and / or carbon dioxide that may be generated during the decomposition process of aqueous organic waste. The method of the present disclosure will be described in detail below.

[0014] [Process (1)] According to one embodiment of the present disclosure, in a method for pyrolysis treatment of aqueous organic waste, (1) a step of heat-treating aqueous organic waste in the presence of an alkali metal compound (also referred to as "step (1)" in the present disclosure) is carried out.

[0015] Step (1) may be any step that allows for heat treatment of the aqueous organic waste in the presence of an alkali metal compound. For example, an alkali metal compound may be added to the aqueous organic waste and then heated, or a preheated alkali metal compound may be brought into contact with the aqueous organic waste.

[0016] The heating method in step (1) is not particularly limited as long as it can achieve the object of the present disclosure. Examples of the heating method include convection heating using gas, etc.; radiation heating using infrared rays, far infrared rays, microwaves, etc.; conduction heating such as by contact with a hot plate; and any combination of two or more of these.

[0017] The temperature of the heat treatment in step (1) is not particularly limited as long as it is a temperature at which the water-containing organic waste can be thermally decomposed, and can be adjusted appropriately depending on the heat treatment time, the amount and composition of the water-containing organic waste, etc., as described below. From the viewpoint of efficiently thermally decomposing the water-containing organic waste, the temperature is preferably above 200°C, more preferably 300°C or higher, and even more preferably above 300°C. From the viewpoint of energy conservation, the temperature is preferably 800°C or lower, more preferably 600°C or lower, and even more preferably 500°C or lower. According to a preferred embodiment of the present disclosure, the temperature of the heat treatment in step (1) is above 200°C and 600°C or lower, preferably 250°C to 600°C, more preferably 300°C to 500°C, and even more preferably 300°C to 400°C.

[0018] The heat treatment time in step (1) is not particularly limited as long as it is a time that allows the hydrous organic waste to be thermally decomposed, and can be adjusted appropriately depending on the temperature, the amount and composition of the hydrous organic waste, etc. The time is preferably 1 minute or more, more preferably 3 minutes or more, and even more preferably 5 minutes or more. The upper limit of the time is not particularly limited, but is, for example, 24 hours or less, preferably 10 hours or less, and more preferably 5 hours or less. According to one embodiment of the present disclosure, the contact time may be 0.1 to 24 hours, preferably 0.5 to 12 hours, and more preferably 1 to 6 hours.

[0019] Step (1) may be carried out under an atmosphere of any gas. According to one embodiment of the present disclosure, step (1) may be carried out under an air atmosphere or a non-oxidizing gas atmosphere. A non-oxidizing gas atmosphere is an atmosphere that does not contain oxygen gas or an atmosphere that is substantially free of oxygen gas. An atmosphere that is substantially free of oxygen gas does not include an atmosphere to which oxygen gas is intentionally added when heating the above-mentioned water-containing organic waste, but includes an atmosphere to which oxygen gas is inevitably mixed. Examples of non-oxidizing gases include inert gases such as nitrogen gas and argon gas.

[0020] Step (1) may be carried out under normal pressure, reduced pressure, or increased pressure. According to one embodiment of the present disclosure, step (1) is carried out under normal pressure.

[0021] Since step (1) can be carried out under atmospheric conditions, it is easy to enlarge the reactor that contains the melt, which is advantageous in that it may be possible to treat a large amount of wet organic waste.

[0022] In step (1), stirring or the like may be carried out as necessary.

[0023] <Water-containing organic waste> The term "aqueous organic waste" in the present disclosure is not particularly limited as long as it is organic waste containing water. The aqueous organic waste may be, for example, solid, semi-solid, slurry, solution, or suspension. The aqueous organic waste may be of household origin (e.g., household garbage) or industrial origin (e.g., industrial waste). Examples of aqueous organic waste include, but are not limited to, food waste (e.g., meats such as chicken, beef, and pork; vegetables; fruits; dried products thereof; mixtures thereof; etc.); organic sludge such as sewage sludge; animal waste (e.g., feces and urine) or carcasses (e.g., pets such as dogs and cats; livestock animals such as cows and pigs; and aquatic animals such as fish, shrimp, turtles, and soft-shelled turtles); and plant waste (e.g., wood); which may be used alone or in any combination of two or more. According to one embodiment of the present disclosure, the aqueous organic waste includes food waste.

[0024] Examples of organic matter contained in aqueous organic waste include, but are not limited to, carbohydrates, proteins, lipids, and dietary fiber (e.g., cellulose), which may be present alone or in any combination of two or more. In this disclosure, carbohydrates refer to carbohydrates excluding dietary fiber. Therefore, carbohydrates in this disclosure do not include dietary fiber. The amount of organic matter contained in aqueous organic waste may be, for example, 1 to 99.9% by mass, preferably 5 to 99.5% by mass, more preferably 10 to 98% by mass, and even more preferably 10 to 90% by mass, based on the total mass of the aqueous organic waste. In this disclosure, the amount of organic matter refers to the amount obtained by subtracting the water content and ash content from the total mass of the aqueous organic waste.

[0025] The amount of water contained in the aqueous organic waste may be, for example, 0.1 to 99% by mass, preferably 0.5 to 95% by mass, more preferably 2 to 90% by mass, and even more preferably 10 to 90% by mass, based on the total mass of the aqueous organic waste. According to the present disclosure, it is believed that aqueous organic waste with any water content can be treated. According to one embodiment of the present disclosure, even aqueous organic waste with a high water content (for example, 10% by mass or more, preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 80% by mass or more, based on the total mass of the aqueous organic waste) can be advantageously treated with less energy than conventional incineration (generally at high temperatures of 800°C or higher).

[0026] The aqueous organic waste may contain ash in addition to moisture and organic matter. Examples of ash include, but are not limited to, zinc, potassium, calcium, chromium, selenium, iron, copper, sodium, magnesium, manganese, molybdenum, cobalt, chlorine, iodine, phosphorus, sulfur, and silicon. When the aqueous organic waste contains ash, the amount of ash contained in the aqueous organic waste may be, for example, 0.001 to 30 mass%, preferably 0.01 to 20 mass%, more preferably 0.05 to 15 mass%, and even more preferably 0.1 to 10 mass%, based on the total mass of the aqueous organic waste. According to one embodiment of the present disclosure, the aqueous organic waste contains at least one element selected from the group consisting of potassium, calcium, and phosphorus. According to one embodiment of the present disclosure, the aqueous organic waste contains at least one element selected from the group consisting of calcium and phosphorus. When the aqueous organic waste contains at least one element selected from the group consisting of calcium and phosphorus, it is advantageous in that useful calcium and phosphorus sources can be recovered by the method of the present disclosure. According to a preferred embodiment of the present disclosure, the aqueous organic waste contains calcium and phosphorus.

[0027] According to a preferred embodiment of the present disclosure, the aqueous organic waste contains, based on the total mass of the aqueous organic waste, 14 to 40% by mass (preferably 14 to 25%) of organic matter, 59 to 85% by mass (preferably 74 to 85%) of water, and 0.1 to 5% by mass (preferably 0.1 to 4%) of ash. According to a preferred embodiment of the present disclosure, the aqueous organic waste contains, based on the total mass of the aqueous organic waste, 7 to 20% by mass (preferably 7 to 12.5%) of carbohydrates, 3 to 10% by mass (preferably 3 to 6.5%) of protein, 1 to 4% by mass (preferably 1 to 2.5%) of lipids, 1 to 4% by mass (preferably 1 to 2.5%) of dietary fiber, 59 to 85% by mass (preferably 74 to 85%) of water, and 0.1 to 5% by mass (preferably 0.1 to 4%) of ash. According to a preferred embodiment of the present disclosure, the aqueous organic waste is food waste with the above composition.

[0028] <Alkali metal compounds> The "alkali metal compound" in the present disclosure is not particularly limited as long as it is a compound of an alkali metal. Examples of the alkali metal compound include, but are not limited to, compounds of alkali metals such as lithium, sodium, potassium, rubidium, and cesium (e.g., hydroxides, alcoholates, phenolates, inorganic acid salts (e.g., phosphates, carbonates, sulfates, and nitrates), and organic acid salts of alkali metals), which may be used alone or in any combination of two or more.

[0029] Among these, alkali metal hydroxides are preferred from the viewpoint of enabling the decomposition of aqueous organic waste to proceed well at low temperatures (for example, 600°C or less, preferably 500°C or less, more preferably 400°C or less), and those containing at least one selected from the group consisting of sodium hydroxide and potassium hydroxide are more preferred, with potassium hydroxide being particularly preferred.

[0030] According to one embodiment of the present disclosure, the amount of potassium hydroxide contained in the alkali metal compound is 45 mass % or more, preferably 72.5 mass % or more, and more preferably 85 mass % or more, based on the total mass of the alkali metal compound. By setting the amount of potassium hydroxide in the alkali metal compound within this range, it is advantageous in that the aqueous organic waste can be decomposed and treated at a lower temperature.

[0031] When the alkali metal compound contains potassium hydroxide and sodium hydroxide, the ratio of potassium hydroxide to sodium hydroxide contained in the alkali metal compound, in terms of mass ratio, is, for example, 3:1 to 1:3.5, preferably 3:1 to 1:3, more preferably 3:1 to 1:1.5, and more preferably 3:1 to 1:1. Furthermore, in the alkali metal compound, the amount of sodium hydroxide per part by mass of potassium hydroxide is, for example, 0.3 parts by mass or more and 3.5 parts by mass or less, preferably 0.3 parts by mass or more and less than 3.5 parts by mass, more preferably 0.3 parts by mass or more and 1.2 parts by mass or less, and even more preferably 0.3 parts by mass or more and 1 part by mass or less. Furthermore, in one embodiment of the present disclosure, the ratio of potassium hydroxide to sodium hydroxide in the alkali metal compound, in terms of molar ratio, is, for example, 3:1 to 1:5, preferably 2.5:1 to 1:4, more preferably 2.2:1 to 1:2, and even more preferably 2:1 to 1:1.

[0032] From the viewpoint of ensuring good decomposition of the aqueous organic waste, the amount of the alkali metal compound used is, for example, 1 part by mass or more, preferably 10 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, still more preferably 200 parts by mass or more, even more preferably 300 parts by mass or more, still more preferably 500 parts by mass or more, still more preferably 800 parts by mass or more, still more preferably 1000 parts by mass or more, still more preferably 1200 parts by mass or more, and still more preferably 1500 parts by mass or more, relative to 100 parts by mass of the aqueous organic waste. There is no particular upper limit to the amount of the alkali metal compound used, but from the viewpoint of cost, the amount of the alkali metal compound used is, for example, 10,000 parts by mass or less, preferably 5,000 parts by mass or less, more preferably 4,000 parts by mass or less, and still more preferably 3,000 parts by mass or less, relative to 100 parts by mass of the aqueous organic waste. When a plurality of water-containing organic wastes are charged into the reactor a plurality of times, the amount of water-containing organic waste charged each time may be adjusted so that the amount of alkali metal compound used each time is the above-mentioned amount.

[0033] According to one embodiment of the present disclosure, the step (1) is a step of heat-treating the water-containing organic waste in the presence of a melt containing an alkali metal compound. Performing the step (1) in the presence of a melt containing an alkali metal compound is advantageous from the viewpoint of enabling large-scale and simple treatment of the water-containing organic waste. According to a preferred embodiment of the present disclosure, the step (1) is a step of immersing the water-containing organic waste in a melt containing an alkali metal compound. In the step (1), immersing the water-containing organic waste in a melt containing an alkali metal compound is particularly advantageous from the viewpoint of enabling larger-scale and simple treatment of the water-containing organic waste.

[0034] The melt containing an alkali metal compound is not particularly limited as long as it contains an alkali metal compound. The amount of the alkali metal compound in the melt is not particularly limited as long as the object of the present disclosure can be achieved. The amount of the alkali metal compound in the melt is, for example, about 80 to 100 mass%, preferably about 85 to 100 mass%, more preferably about 88 to about 99 mass%, and even more preferably about 90 to about 98 mass%, relative to the total mass of the melt. When the amount is less than 100 mass%, at least a portion of the remainder may be an impurity contained in the active pharmaceutical ingredient of the alkali metal compound (e.g., potassium hydroxide).

[0035] From the viewpoint of ensuring good decomposition of the aqueous organic waste, the amount of the melt containing the alkali metal compound is, for example, 1 part by mass or more, preferably 10 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, still more preferably 200 parts by mass or more, even more preferably 300 parts by mass or more, still more preferably 500 parts by mass or more, still more preferably 800 parts by mass or more, still more preferably 1000 parts by mass or more, still more preferably 1200 parts by mass or more, and still more preferably 1500 parts by mass or more, relative to 100 parts by mass of the aqueous organic waste. There is no particular upper limit to the amount of the alkali metal compound used, but from the viewpoint of cost, the amount of the alkali metal compound used is, for example, 10,000 parts by mass or less, preferably 5,000 parts by mass or less, more preferably 4,000 parts by mass or less, and still more preferably 3,000 parts by mass or less, relative to 100 parts by mass of the aqueous organic waste.

[0036] The viscosity of the melt is not particularly limited as long as the object of the present disclosure can be achieved. The viscosity of the melt may be, for example, 50 mPa·s or less, preferably 20 mPa·s or less, and more preferably 10 mPa·s or less. The viscosity of the melt may be adjusted to the above range by adjusting the type and amount of the alkali metal compound.

[0037] The amount of the melt containing the alkali metal compound in the reactor into which the aqueous organic waste is introduced is not particularly limited as long as the decomposition of the aqueous organic waste proceeds. From the viewpoint of ensuring good decomposition of the aqueous organic waste, the amount of the melt containing the alkali metal compound in the reactor into which the aqueous organic waste is introduced is, for example, 1 part by mass or more, preferably 10 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, even more preferably 200 parts by mass or more, even more preferably 300 parts by mass or more, even more preferably 500 parts by mass or more, even more preferably 800 parts by mass or more, even more preferably 1000 parts by mass or more, even more preferably 1200 parts by mass or more, and even more preferably 1500 parts by mass or more, relative to 100 parts by mass of the aqueous organic waste introduced. The amount of the melt containing the alkali metal compound in the reactor is not particularly limited, but is, for example, 10,000 parts by mass or less, preferably 5,000 parts by mass or less, relative to 100 parts by mass of the aqueous organic waste introduced. In the case of a continuous system, the rate at which the melt is fed into the reactor and the rate at which the melt is discharged from the reactor are not particularly limited.

[0038] To further lower the temperature of a melt containing an alkali metal compound, for example, a method of lowering the freezing point (melting point) of the alkali metal compound by using a combination of multiple alkali metal compounds can be used. Alternatively, to further lower the temperature of a melt containing an alkali metal compound, for example, the alkali metal compound may be allowed to coexist with other substances (for example, impurities contained in the alkali metal compound).

[0039] When potassium hydroxide is approximately 100% pure, its melting point is approximately 360°C. However, in the presence of other substances (e.g., alkali metal compounds other than potassium hydroxide, impurities, etc.), the melting point can drop to 300°C or lower (preferably 280°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower). Note that the term "impurity" used in this context refers to an unintentional substance that may be contained in a potassium hydroxide drug substance (e.g., a reagent). Therefore, substances that may be intentionally allowed to coexist with potassium hydroxide (e.g., sodium hydroxide, as described below) are not considered "impurities." When potassium hydroxide contains impurities, the purity of the potassium hydroxide is less than 100% (i.e., the remainder is impurities). In one embodiment of the present disclosure, potassium hydroxide is preferably less than 100% pure (i.e., contains impurities), more preferably 85% or more but less than 100%, and even more preferably 85% or more but less than 99% pure. Potassium hydroxide with a purity of less than 100% is available from, for example, Fujifilm Wako Pure Chemical Industries, Ltd., Sigma-Aldrich, etc.

[0040] Examples of the impurities include, but are not limited to, potassium salts other than potassium hydroxide (e.g., chlorides such as potassium carbonate and potassium chloride, phosphates such as potassium phosphate, and silicates such as potassium silicate), metals such as sodium, magnesium, calcium, zinc, aluminum, iron, copper, nickel, chromium, manganese, and rubidium, and salts of these metals (e.g., hydroxides, chlorides, carbonates, phosphates, etc.).

[0041] The melting point of potassium hydroxide can also be lowered in the presence of sodium hydroxide. For example, potassium hydroxide with a purity of about 100% has a melting point of about 360°C when used alone, as described above. However, in the presence of sodium hydroxide with a purity of about 100%, the melting point can be lowered to about 300°C or lower (preferably about 280°C or lower, more preferably about 250°C or lower, and even more preferably about 200°C or lower). The melting point when potassium hydroxide and sodium hydroxide coexist can vary depending on their ratio (e.g., mass ratio, molar ratio, etc.). For such melting points, reference may be made to known literature, information, etc. For example, referring to https: / / www.metallab.net / chemsoc / alloys.php?id=19, when the molar ratio of potassium hydroxide to sodium hydroxide is about 4:1 to about 1:19 (i.e., the mass ratio of potassium hydroxide to sodium hydroxide is about 1:14 to about 7:1), a melt can be formed even at about 300°C or below (preferably, about 300°C or below and about 170°C or above). Alternatively, a person skilled in the art can experimentally measure the melting point at a desired ratio, for example, by referring to a known melting point measurement method (e.g., visual observation, thermal analysis, etc.). When sodium hydroxide and sodium hydroxide coexist, the melting point can be further lowered by the additional presence of the above-mentioned impurities.

[0042] [Process (2)] According to one embodiment of the present disclosure, the method may include (2) a step of recovering the gasified gas (also referred to as "step (2)" in the present disclosure). Without being bound by theory, heat treatment of the water-containing organic waste in the presence of an alkali metal compound may cause the water-containing organic waste to be decomposed and / or gasified, thereby generating gas. Therefore, including step (2) in the method is advantageous in that useful gases (e.g., fuel gases such as hydrogen and methane) generated by the method can be recovered.

[0043] The method for recovering the gas is not particularly limited, but examples thereof include recovery using any solvent, recovery using known devices and equipment (for example, gas packs), etc.

[0044] The step (2) may be carried out simultaneously with the step (1) or any other step, or may be carried out before or after each of these steps.

[0045] [Process (3)] According to one embodiment of the present disclosure, a step (also referred to as "step (3)" in the present disclosure) may be carried out in which the heat-treated product obtained in step (1) (i.e., the residue obtained by heat-treating the aqueous organic waste in the presence of an alkali metal compound) is mixed with a solvent. The heat-treated product typically contains at least an alkali metal compound and a component derived from the aqueous organic waste. Carrying out step (3) in the method of the present disclosure is advantageous in that it enables separation into substances soluble in the solvent (typically, the alkali metal compound and soluble components derived from the aqueous organic waste captured by the alkali metal compound) and substances insoluble in the solvent (typically, the residue derived from the aqueous organic waste).

[0046] The solvent used in step (3) is preferably a solvent capable of dissolving an alkali metal compound. Examples of the solvent include water; alcohols such as methanol and ethanol; inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid; organic acids such as phthalic acid and malic acid; and mixed solvents of any two or more of these, and a solvent containing water is preferred.

[0047] The amount of the solvent used in step (3) may be, for example, 1 to 10,000 parts by mass, preferably 10 to 3,000 parts by mass, and more preferably 100 to 1,000 parts by mass, based on 100 parts by mass of the alkali metal compound. The amount of the solvent used in step (3) may be, for example, 1 to 10,000 parts by mass, preferably 10 to 3,000 parts by mass, and more preferably 100 to 1,000 parts by mass, based on 100 parts by mass of the melt containing the alkali metal compound.

[0048] [Process (4)] According to a preferred embodiment of the present disclosure, a step (also referred to as "step (4)" in the present disclosure) may be carried out in which the solvent mixture obtained in step (3) (i.e., a mixture of the heat-treated product and the solvent) is separated into a filtrate and a residue. The filtrate and / or residue may contain useful components derived from the aqueous organic waste (e.g., a calcium source, a phosphorus source). Therefore, carrying out step (4) in the present disclosure is advantageous in that it may enable the recovery of useful components derived from the aqueous organic waste from the filtrate and / or residue.

[0049] The separation method in step (4) is not particularly limited as long as it can separate the filtrate from the residue, and examples thereof include filtration, centrifugation, etc. From the viewpoint of easily separating a large amount of filtrate from the residue, the separation is preferably performed by filtration.

[0050] The obtained filtrate and / or residue may contain ash derived from the aqueous organic waste, and therefore, the desired ash (e.g., a phosphorus source, a calcium source) may be separated or isolated by, for example, a known method. Furthermore, the obtained filtrate and / or residue may contain ash derived from the aqueous organic waste, and therefore may be used as a fertilizer or a raw material for a fertilizer.

[0051] In addition to the above steps, the method of the present disclosure may also include other steps (e.g., washing, cooling) as needed. Such other steps may be performed at any position before, simultaneously with, or after the above steps.

[0052] [Fertilizer manufacturing method] The heat-treated product (preferably the filtrate and / or residue separated from the solvent mixture of the heat-treated product and the solvent) that can be obtained after carrying out the pyrolysis treatment of the aqueous organic waste of the present disclosure may contain components useful as fertilizers, such as a phosphorus source and a calcium source. Further investigations by the present inventors have revealed that when the aqueous organic waste contains phosphorus and calcium, the filtrate may contain phosphorus and, in some cases, calcium, and the residue may contain calcium and, in some cases, phosphorus. Therefore, the filtrate or its solidified product (e.g., obtained by evaporating the water in the filtrate) and / or the residue can be used, for example, as fertilizer.

[0053] Therefore, according to another embodiment of the present disclosure, (1) A step of heat treating the aqueous organic waste in the presence of an alkali metal compound A method for producing a fertilizer, comprising: is provided.

[0054] The definitions of each term, preferred embodiments, etc. are as described above in this specification.

[0055] According to another embodiment of the present disclosure, there is provided a fertilizer produced by the method of the present disclosure.

[0056] [Pyrolysis treatment system / fertilizer production system] According to another embodiment of the present disclosure, A pyrolysis treatment unit that heat-treats aqueous organic waste in the presence of alkali metal compounds A system for pyrolysis treatment of aqueous organic waste, comprising: is provided.

[0057] According to another embodiment of the present disclosure, A pyrolysis treatment unit that heat-treats aqueous organic waste in the presence of alkali metal compounds A system for producing fertilizer, comprising: is provided.

[0058] <Pyrolysis Processing Unit> The pyrolysis treatment unit is not particularly limited as long as it is capable of storing, for example, aqueous organic waste and an alkali metal compound (or a melt containing an alkali metal compound) and is made of a material that can withstand heat treatment. By heating the pyrolysis treatment unit, the aqueous organic waste can be pyrolyzed in the presence of the alkali metal compound (or a melt containing an alkali metal compound).

[0059] <Heating part> According to an embodiment of the present disclosure, the system may include a heating unit capable of heating the pyrolysis treatment unit. The heating method of the heating unit is not particularly limited, and the heating unit may be configured to be capable of implementing the heating method of the present disclosure.

[0060] <Other> The above system may include, in addition to the pyrolysis treatment section and the heating section, sections having other functions as required.

[0061] The above components may be present in one device or in two or more separate devices.

[0062] The definitions of each term, preferred embodiments, etc. are as described above in this specification.

[0063] [Pyrolysis treatment equipment / fertilizer manufacturing equipment] According to another embodiment of the present disclosure, there is provided an apparatus for pyrolysis treatment of aqueous organic waste, comprising the pyrolysis treatment system of the present disclosure.

[0064] According to another embodiment of the present disclosure, there is provided a fertilizer production apparatus including the system for producing fertilizer of the present disclosure.

[0065] The definitions of each term, preferred embodiments, etc. are as described above in this specification.

[0066] [Melted composition or solidified product thereof] According to another embodiment of the present disclosure, there is provided a melt composition or a solidified product thereof, the melt composition comprising a melt containing an alkali metal compound and a component derived from aqueous organic waste dissolved in the melt. The melt composition may be obtained, for example, by immersing the aqueous organic waste in a melt containing an alkali metal compound. The melt composition may be cooled to form a solidified product.

[0067] In the melt composition, the amount of the melt containing the alkali metal compound is, for example, 1 part by mass or more, preferably 10 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, even more preferably 200 parts by mass or more, even more preferably 300 parts by mass or more, even more preferably 500 parts by mass or more, even more preferably 800 parts by mass or more, even more preferably 1000 parts by mass or more, even more preferably 1200 parts by mass or more, and even more preferably 1500 parts by mass or more, relative to 100 parts by mass of the aqueous organic waste. There is no particular upper limit on the amount of the alkali metal compound used, but from the standpoint of cost, the amount of the alkali metal compound used is, for example, 10,000 parts by mass or less, preferably 5,000 parts by mass or less, more preferably 4,000 parts by mass or less, and even more preferably 3,000 parts by mass or less, relative to 100 parts by mass of the aqueous organic waste.

[0068] In the melt composition, the amount of the alkali metal compound is, for example, about 80 to 100% by mass, preferably about 85 to 100% by mass, more preferably about 88 to 99% by mass, and even more preferably about 90 to 98% by mass, relative to the total mass of the melt containing the alkali metal compound. When the amount is less than 100% by mass, at least a portion of the remainder may be an impurity contained in the active pharmaceutical ingredient of the alkali metal compound (e.g., potassium hydroxide).

[0069] For example, a solvent (e.g., a solvent containing water) may be added to the molten composition or a solidified product thereof, followed by heating, neutralization, etc., to decompose and / or gasify the components derived from the aqueous organic waste and remove them. This results in a molten composition with few impurities (e.g., aqueous organic waste, components derived from the aqueous organic waste). The molten composition may be cooled to form a solidified product. The obtained molten composition or a solidified product thereof can be used as the alkali metal compound in the method of the present disclosure.

[0070] The definitions of each term, preferred embodiments, etc. are as described above in this specification.

[0071] [Gas recovery composition] According to another embodiment of the present disclosure, there is provided a composition for gas recovery, comprising the melt composition or a solidified product thereof. The composition for gas recovery may be in a molten state or a solid state. For example, the melt composition may be cooled to form a solidified composition for gas recovery.

[0072] By adding a solvent (e.g., a solvent containing water) to the composition for gas recovery and heating it at an appropriate temperature, the components derived from the water-containing organic waste contained in the composition for gas recovery may be decomposed and / or gasified, thereby recovering, for example, a fuel gas. The fuel gas in the present disclosure is not particularly limited as long as it is a gas that can be used as a fuel, and examples thereof include hydrogen, methane, etc.

[0073] The heating temperature of the composition for gas recovery during gas recovery is preferably 50°C or higher, more preferably 70°C or higher, even more preferably 90°C or higher, and particularly preferably 100°C or higher.

[0074] The heating time of the composition for gas recovery during gas recovery is appropriately set depending on the heating temperature. The heating time is preferably 10 minutes or more, more preferably 20 minutes or more, and even more preferably 30 minutes or more. The upper limit of the heating time is not particularly limited, but is preferably 10 hours or less, more preferably 5 hours or less, and even more preferably 2 hours or less.

[0075] After recovering the gas from the composition for gas recovery, the remaining solvent can be removed by heating or the like to recover the alkali metal compound. The recovered alkali metal compound can be used as the alkali metal compound in the method of the present disclosure.

[0076] According to a preferred embodiment of the present disclosure, the composition for gas recovery is a composition for fuel gas recovery.

[0077] The definitions of each term, preferred embodiments, etc. are as described above in this specification.

[0078] The present disclosure encompasses the following. [1] (1) A step of heat treating aqueous organic waste in the presence of an alkali metal compound A method for pyrolytically treating aqueous organic waste, comprising: [2] The method according to [1], wherein the aqueous organic waste comprises food waste. [3] The method according to [1] or [2], wherein the step (1) is carried out in the presence of a melt containing an alkali metal compound. [4] The method according to [3], wherein the step (1) includes a step of immersing the aqueous organic waste in a molten liquid containing an alkali metal compound. [5] The method according to any one of [1] to [4], wherein the temperature of the heat treatment in the step (1) is 200°C or higher. [6] The method according to any one of [1] to [5], wherein the temperature of the heat treatment in the step (1) is 600° C. or lower. [7] The method according to any one of [1] to [6], wherein the alkali metal compound comprises a hydroxide of an alkali metal. [8] The method according to any one of [1] to [7], wherein the alkali metal compound comprises potassium hydroxide or sodium hydroxide. [9] The method according to any one of [1] to [8], wherein the alkali metal compound comprises potassium hydroxide.

[10] (2) Recovering the gasified gas. The method according to any one of [1] to [9], further comprising:

[11] (3) A step of mixing the heat-treated product obtained in the above step (1) with a solvent. The method according to any one of [1] to

[10] , further comprising:

[12] (4) A step of separating the solvent mixture obtained in the above step (3) into a filtrate and a residue. The method according to

[11] , further comprising:

[13] A pyrolysis treatment unit that heat-treats aqueous organic waste in the presence of alkali metal compounds A system for pyrolysis treatment of aqueous organic waste, comprising:

[14] An apparatus for treating aqueous organic waste by pyrolysis, comprising the system according to

[13] .

[15] (1) A process for heat-treating aqueous organic waste in the presence of an alkali metal compound. A method for producing a fertilizer, comprising:

[16] A fertilizer produced by the method described in

[15] . [Example]

[0079] The method of the present disclosure will be described in more detail below using examples. However, the following examples are not intended to limit the method of the present disclosure in any way. Unless otherwise specified, percentages and ratios described herein are by mass. Furthermore, unless otherwise specified, units and measurement methods described herein are in accordance with the provisions of the Japanese Industrial Standards (JIS).

[0080] [sample] Sample 1 Commercially available moist dog food (manufactured by Smack Corporation) was used as a sample to simulate aqueous organic waste (food waste) (Figure 1). The composition of the sample was comparable to that of typical food waste (Table 1). The ash content of the sample, obtained by heating it at 800°C for 1 hour, was analyzed by X-ray fluorescence analysis (Epsilon 1, manufactured by Malvern Panalytical). The results are shown in Table 2. Furthermore, the composition of the organic matter, ash, and moisture content of the sample, as well as the results of elemental analysis (CE-440F, manufactured by Exeter Analytical), are shown in Tables 3 and 4. [Table 1] [Table 2] [Table 3] [Table 4]

[0081] Samples 2 to 7 Chicken (sample 2), dried fruit (sample 3), corn cobs (sample 4), and household food waste (sample 5) were used as samples to mimic moist organic waste (food waste) (Fig. 1). Wood (sample 6) and cherry tree branches (sample 7) were used as samples to mimic moist organic waste (plant waste) (Fig. 1).

[0082] [Production of salts containing alkali metal compounds] Potassium hydroxide (KOH, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 85% or higher) and sodium hydroxide (NaOH, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 97% or higher) were mixed in a mass ratio of 3:1, 1:1, or 1:3 (i.e., about 0.3 parts by mass, about 1 part by mass, or about 3 parts by mass of sodium hydroxide per 1 part by mass of potassium hydroxide), heated at 400°C for 1 hour, and then allowed to cool, to obtain a mixed salt. Similarly, potassium hydroxide alone or sodium hydroxide alone was heated at 400°C for 1 hour and then allowed to cool, to produce a salt mixture. Assuming that the purities of the potassium hydroxide and sodium hydroxide used are 85% and 97%, respectively, the converted mass ratios for 3:1, 1:1, and 1:3 are approximately 2.6:1, approximately 1:1.2, and approximately 1:3.4, respectively (i.e., approximately 0.4 parts by mass, approximately 1.2 parts by mass, and approximately 3.4 parts by mass of sodium hydroxide per 1 part by mass of potassium hydroxide). Furthermore, the amount of potassium hydroxide contained in the mixed salt is 72.2 mass%, 45.6 mass%, and 23.2 mass%, based on the total mass of the mixed salt, when the mass ratios are 3:1, 1:1, and 1:3, respectively (calculated based on the converted masses assuming that the purities of the potassium hydroxide and sodium hydroxide used are 85% and 97%, respectively). The mass ratio of potassium hydroxide to sodium hydroxide described below indicates the ratio before conversion.

[0083] [Example 1-1: Food waste decomposition treatment 1] The above sample 1 (3 g) wrapped in a stainless steel mesh (100 mesh) was placed in a reactor containing 60 g of the potassium hydroxide prepared above (potassium hydroxide heated at 400°C for 1 hour and then allowed to cool), and a stainless steel weight (Φ19 mm, 28 g) was placed on top of it. Nitrogen gas was flowed into the reactor at 100 mL / min for 30 minutes to replace the atmosphere inside the reactor with nitrogen. The temperature was then raised from 200°C to 600°C under a nitrogen gas atmosphere (20 mL / min) (heating time: 30 minutes) and heated for 1 hour. After heating, the reactor was allowed to cool naturally under a nitrogen atmosphere (20 mL / min) for 40 minutes. Distilled water was then added to the reactor to dissolve the molten salt, and the mixture was filtered to separate the residue and filtrate. The residue was washed with water again and then dried. The mass of the sample before heating and the mass of the resulting residue were measured, and the residual rate (%) was calculated using the following formula. The results are shown in Figure 2. Furthermore, the chemical composition of the resulting residue was analyzed using an X-ray fluorescence spectrometer (Epsilon 1, manufactured by Malvern Panalytical). The results are shown in Table 5.

number

[0084] [Example 1-2: Food waste decomposition treatment 2] The same method as in Example 1-1 was carried out, except that sodium hydroxide:potassium hydroxide in a mass ratio of 1:3 was used instead of potassium hydroxide (i.e., a mass ratio of 0:1). The results are shown in Figures 1 to 4 and Table 5.

[0085] [Example 1-3: Food waste decomposition treatment 3] The same method as in Example 1-1 was carried out, except that sodium hydroxide:potassium hydroxide in a mass ratio of 1:1 was used instead of potassium hydroxide (i.e., a mass ratio of 0:1). The results are shown in Figures 1 to 4 and Table 5.

[0086] [Example 1-4: Food waste decomposition treatment 4] The same method as in Example 1-1 was carried out, except that sodium hydroxide:potassium hydroxide in a mass ratio of 3:1 was used instead of potassium hydroxide (i.e., a mass ratio of 0:1). The results are shown in Figures 1 to 4 and Table 5.

[0087] [Example 1-5: Food waste decomposition treatment 5] The same method as in Example 1-1 was carried out, except that sodium hydroxide (i.e., mass ratio 1:0) was used instead of potassium hydroxide (i.e., mass ratio 0:1). The results are shown in Figures 1 to 4 and Table 5.

[0088] [Example 1-6: Food waste decomposition treatment 6] The same method as in Example 1-2 was carried out, except that the heating temperature was 300° C. or 400° C. and the heating time was 1 to 2 hours. The results are shown in FIG.

[0089] [Reference example: Decomposition treatment of food waste7] The same method as in Example 1-1 was carried out, except that potassium hydroxide was not used (that is, heating was carried out in the absence of an alkali metal compound). The results are shown in Figures 1 to 4 and Table 5.

[0090] [Table 5]

[0091] [Example 2: Decomposition of food waste8] The above sample 2 (approximately 22 g) wrapped in a stainless steel mesh (100 mesh) was placed in a reactor containing 100 g of the potassium hydroxide prepared above (potassium hydroxide heated at 400°C for 1 hour and then allowed to cool). A stainless steel weight (Φ19 mm, 28 g) was then placed on top of the sample. Nitrogen gas was flowed into the reactor at 100 mL / min for 30 minutes to replace the atmosphere inside the reactor with nitrogen. The temperature was then increased from 200°C to 400°C under a nitrogen gas atmosphere (20 mL / min) (heating time: 30 minutes) and heated for 1 hour. After heating, the reactor was allowed to cool naturally under a nitrogen atmosphere (20 mL / min) for 40 minutes. Distilled water was then added to the reactor to dissolve the molten salt, and the mixture was filtered to separate the residue and filtrate. The residue was washed with water again and then dried. The mass of the sample before heating and the mass of the resulting residue were measured, and the residual rate (%) was calculated using the same method as in Example 1-1. The results are shown in Figure 6. Furthermore, the chemical composition of the resulting residue was analyzed using an X-ray fluorescence spectrometer (Epsilon 1, manufactured by Malvern Panalytical). The results are shown in Table 6.

[0092] [Example 3: Decomposition of food waste9] The same method as in Example 2 was carried out, except that Sample 3 (approximately 30 g) was used instead of Sample 2. The results are shown in FIG.

[0093] [Example 4: Food waste decomposition treatment 10] The same method as in Example 2 was carried out, except that Sample 4 was used instead of Sample 2 and the amount of potassium hydroxide was changed to 150 g. The results are shown in Figure 8.

[0094] [Example 5: Decomposition of food waste11] The same method as in Example 2 was carried out, except that Sample 5 (approximately 230 g) packaged in a plastic bag was used instead of Sample 2, and the amount of potassium hydroxide was changed to 600 g. The results are shown in Figure 9.

[0095] [Example 6: Decomposition treatment of plant waste 1] The same method as in Example 2 was carried out, except that Sample 6 (approximately 20 g) was used instead of Sample 2 and the amount of potassium hydroxide was changed to 200 g. The results are shown in Figure 10 and Table 6.

[0096] [Example 7: Decomposition treatment of plant waste 2] The same method as in Example 2 was carried out, except that Sample 7 was used instead of Sample 2 and the amount of potassium hydroxide was changed to 150 g. The results are shown in Figure 11 and Table 6.

[0097] [Table 6]

[0098] The results of Examples 1-1 to 1-5 show that heating the sample (mimic of food waste) in the presence of an alkali metal compound reduced the weight of the residue (FIG. 2). On the other hand, when heated in the absence of an alkali metal compound (Reference Example 1), 20% or more of the residue remained even at 600°C (FIG. 2). Therefore, the method of the present disclosure is advantageous in that it can decompose and treat aqueous organic waste (preferably food waste) at lower temperatures. Furthermore, based on the results of Examples 1-1 to 1-5, it is believed that by heating a sample (mimic of food waste) in the presence of an alkali metal compound (preferably containing potassium hydroxide) (preferably at 200°C or higher, more preferably above 200°C, and even more preferably at 300°C or higher), phosphorus contained in the sample can be captured by a molten salt or its melt (Figure 3). When heated in the absence of an alkali metal compound (Reference Example 1), almost no phosphorus was recovered at any temperature (Figure 3). This is believed to be consistent with the results of the chemical composition of the resulting residue (Table 5). Since the phosphorus captured in the molten salt or its melt can be isolated by any method, the method of the present disclosure is considered to be advantageous in that it can recover highly useful phosphorus contained in aqueous organic waste (preferably food waste). Furthermore, the phosphorus captured in the molten salt or its melt can be solidified together with the molten salt or its melt (e.g., by allowing the melt containing the captured phosphorus to cool and solidify), and used as fertilizer. Therefore, the method of the present disclosure is advantageous in that it can recycle highly useful phosphorus contained in aqueous organic waste (preferably food waste) as fertilizer. Conventional methods require high-temperature conditions or concentrated sulfuric acid, etc., to recover phosphorus. On the other hand, one embodiment of the present disclosure is advantageous in that it can recover phosphorus even at temperatures of 600°C or lower (preferably, above 200°C and below 600°C, more preferably 250 to 600°C, more preferably 300 to 500°C, and even more preferably 300 to 400°C) by using an alkali metal compound. Furthermore, the resulting residue contains a large amount of calcium oxide (Table 5), so it can be used as fertilizer. Therefore, the method of the present disclosure is advantageous in that it enables the highly useful calcium contained in aqueous organic waste (preferably food waste) to be recycled as fertilizer.

[0099] The results of Examples 1-1 to 1-6 suggest that heating a sample (a food waste simulant) in the presence of an alkali metal compound (preferably containing potassium hydroxide) can recover useful gases (e.g., fuel gases such as hydrogen and methane) and / or suppress the generation of carbon monoxide, carbon dioxide, and other gases that are difficult to suppress using conventional methods. On the other hand, when heating was performed in the absence of an alkali metal compound (Reference Example 1), not only was the recovery of useful gases (e.g., fuel gases such as hydrogen and methane) low, but the generation of carbon monoxide, carbon dioxide, and other gases was high. Therefore, the method of the present disclosure is advantageous in that it can recover useful gases generated by the decomposition of aqueous organic waste (preferably food waste) and / or suppress the generation of carbon monoxide, carbon dioxide, and other gases generated by the decomposition of aqueous organic waste (preferably food waste). Note that no generation of hydrogen chloride gas was observed in Examples 1-1 to 1-6 and Reference Example 1.

[0100] From the results of Examples 2 to 7, it is believed that the method of the present disclosure can treat wet organic waste of various types and moisture contents. Without being bound by theory, considering the XRD patterns, it is believed that the residue obtained by the method of the present disclosure has little or no crystalline structure (FIGS. 6 and 7).

[0101] Further investigations by the present inventors have revealed that heat treatment in the presence of an alkali metal compound can treat not only the aqueous organic waste but also the packaging (e.g., paper bags, plastic bags, etc.) that contains the aqueous organic waste at the same time. For example, it is known that the treatment efficiency of the methane fermentation-based treatment method described in Patent Document 1 and the like is significantly reduced when packaging is present. On the other hand, the present disclosure has the advantage that the treatment efficiency is not significantly reduced even when packaging is present. This is thought to be particularly advantageous when the aqueous organic waste is packaged in packaging (e.g., food waste from households or food waste from food factories) (Example 5).

Claims

1. (1) A step of heat treating aqueous organic waste in the presence of an alkali metal compound A method for pyrolytically treating aqueous organic waste, comprising:

2. The method of claim 1 , wherein the aqueous organic waste comprises food waste.

3. The method of claim 1 , wherein step (1) is carried out in the presence of a melt containing an alkali metal compound.

4. The method according to claim 3, wherein the step (1) includes a step of immersing the aqueous organic waste in a molten liquid containing an alkali metal compound.

5. The method according to claim 1, wherein the temperature of the heat treatment in step (1) is 200°C or higher.

6. The method according to claim 1, wherein the temperature of the heat treatment in step (1) is 600°C or less.

7. The method of claim 1 , wherein the alkali metal compound comprises an alkali metal hydroxide.

8. The method of claim 1 , wherein the alkali metal compound comprises potassium hydroxide or sodium hydroxide.

9. The method of claim 1 , wherein the alkali metal compound comprises potassium hydroxide.

10. (2) A process for recovering the gasified gas The method of claim 1 further comprising:

11. (3) A step of mixing the heat-treated product obtained in the step (1) with a solvent. The method of claim 1 further comprising:

12. (4) A step of separating the solvent mixture obtained in the step (3) into a filtrate and a residue. The method of claim 11 further comprising:

13. A pyrolysis treatment unit that heat-treats aqueous organic waste in the presence of alkali metal compounds A system for pyrolysis treatment of aqueous organic waste, comprising:

14. An apparatus for pyrolysis treatment of aqueous organic waste, comprising the system of claim 13.

15. (1) A step of heat treating aqueous organic waste in the presence of an alkali metal compound A method for producing a fertilizer, comprising:

16. 16. A fertilizer produced by the method of claim 15.

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