Air pollutant removal material and its manufacturing method, air pollutant removal method, and fertilizer manufacturing method

Abstract

To provide a novel carbide removal material and a manufacturing method thereof capable of removing an air pollutant, and a removal method of the air pollutant.SOLUTION: A removal material includes a porous carbide containing a phosphorus-containing compound and a binder. The total phosphoric acid concentration of the removal material may be 0.1 mass% or more and 30 mass% or less. Further, the content of carbon in the removal material may be 10 mass % or more and 80 mass % or less, and the content of iron element may be 5 mass % or more and 35 mass % or less. A method for manufacturing the removal material includes carbonizing biomass to prepare a porous carbide, mixing the porous carbide with a binder and iron powder and / or iron oxide powder to prepare an iron-containing carbide, and bringing the iron-containing carbide into contact with water containing at least phosphoric acid.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] One embodiment of the present invention relates to a removal material for removing air pollutants and a method for producing the same. Alternatively, one embodiment of the present invention relates to a method for removing air pollutants using the removal material. Alternatively, one embodiment of the present invention relates to a fertilizer containing the removal material and a method for producing the same. [Background technology]

[0002] Typical examples of substances that cause air pollution include nitrogen oxides such as nitric oxide (NO), nitrogen dioxide (NO2), and dinitrogen monoxide (N2O), and sulfur oxides such as sulfur disulfide (SO2). Activated carbon fibers carrying a metal catalyst such as platinum are known as removal materials that can remove nitrogen oxides from the atmosphere. For example, Patent Document 1 discloses activated carbon fibers carrying a metal catalyst, which decomposes nitrogen oxides into water and nitrogen in the presence of a reducing agent such as ammonia, methane, ethylene, or ethane. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-253800 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one embodiment of the present invention is to provide a novel carbide-based removal material capable of removing air pollutants such as nitrogen oxides and sulfur oxides, a method for producing the same, and a method for removing air pollutants. Alternatively, an object of one embodiment of the present invention is to provide a removal material that can improve air quality, store carbon dioxide, and function as a fertilizer. [Means for solving the problem]

[0005] One embodiment of the present invention is a material for removing air pollutants, which comprises a porous carbide containing a phosphorus-containing compound and a binder.

[0006] One embodiment of the present invention is a method for producing a material for removing air pollutants, which includes carbonizing biomass to prepare a porous carbide, mixing the porous carbide with a binder and iron powder and / or iron oxide powder to prepare an iron-containing carbide, and contacting the iron-containing carbide with water containing a phosphorus-containing compound.

[0007] One embodiment of the present invention is a method for removing air pollutants, which comprises contacting a gas containing the air pollutants with a removing material, the removing material comprising a porous carbide containing a phosphorus-containing compound and a binder.

[0008] One embodiment of the present invention is a method for producing a fertilizer. The method includes contacting a gas containing air pollutants with a removing material and mixing the removing material with a fertilizer aid. The removing material includes a porous carbide containing a phosphorus-containing compound and a binder. [Effects of the Invention]

[0009] The removal material according to an embodiment of the present invention contains a porous carbide produced from carbon dioxide and has the function of removing air pollutants such as nitrogen oxides and sulfur oxides. Therefore, the embodiment of the present invention enables the improvement of air quality and the storage of carbon dioxide. Furthermore, because the porous carbide contains a phosphorus-containing compound, it can be used as a raw material for fertilizer for plant growth. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a flowchart showing a method for producing a removal material according to an embodiment of the present invention. [Figure 2] 1 is a flowchart showing a method for producing a fertilizer using a removal material according to an embodiment of the present invention. [Figure 3]1 is a conceptual diagram illustrating water quality improvement, air quality improvement, and carbon dioxide storage using a removal material according to one embodiment of the present invention. [Figure 4] 1 is a plot evaluating the carbon dioxide removal capacity of the removal material of Example 1 and the samples of Comparative Examples 1 to 3. [Figure 5] 1 is a plot evaluating the nitrogen oxide removal capacity of the removal material of Example 1 and the samples of Comparative Examples 1 to 3. [Figure 6] 1 is a cumulative plot of nitrogen in nitrogen oxides removed using the removal material of Example 1 and the sample of Comparative Example 3. [Figure 7] 1 is a graph showing the nitrogen content of the removal material of Example 1 and the sample of Comparative Example 3 before and after a nitrogen oxide removal test. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings, etc. However, the present invention can be embodied in various forms without departing from the spirit of the present invention, and should not be construed as being limited to the description of the embodiments exemplified below.

[0012] In this specification, the term "phosphoric acid" does not only refer to phosphoric acid in the narrow sense, i.e., a compound represented by the chemical formula H3PO4, but also refers to various phosphates, monohydrogen phosphates, and dihydrogen phosphates in addition to phosphoric acid (H3PO4). Thus, for example, unless otherwise specified, iron phosphate refers not only to iron phosphate but also to iron monohydrogen phosphate and iron dihydrogen phosphate, and the iron ions contained therein may be divalent or trivalent.

[0013] Hereinafter, a removal material according to one embodiment of the present invention and a method for producing the same, a method for removing air pollutants and a method for producing fertilizer using the removal material, and storage of carbon dioxide using the removal material will be described.

[0014] 1. Composition of removal material The remover includes a porous carbide containing a phosphorus-containing compound (hereinafter also referred to as phosphorus-containing porous carbide) and a binder. A typical example of the phosphorus-containing compound is iron phosphate, but inorganic phosphorus such as iron metaphosphate or iron pyrophosphate may also be used, or organic phosphorus such as phosphate ester may be used. The remover may further include iron (zero-valent iron) and / or an iron compound such as iron oxide or iron hydroxide, and may further include a compound of a metal selected from alkali metals and alkaline earth metals. Each component constituting the remover will be described below.

[0015] 1-1. Phosphorus-containing porous carbide The phosphorus-containing porous charcoal is a charcoal to which a phosphorus-containing compound is fixed. The charcoal can be obtained by carbonizing organic matter, such as biomass, as described below, and the phosphorus-containing compound is fixed to the pores on the surface or inside the charcoal. The amount of the phosphorus-containing compound contained in the phosphorus-containing porous charcoal can be determined arbitrarily. For example, the amount of the phosphorus-containing compound in the phosphorus-containing porous charcoal may be adjusted so that the total phosphorus concentration in the removal material is 0.1% by mass or more and 30% by mass or less, preferably 0.5% by mass or more and 25% by mass or less, or 1% by mass or more and 20% by mass or less. The term "total phosphorus" refers to the total of water-soluble phosphorus and water-insoluble phosphorus.

[0016] The total phosphate concentration can be measured using ammonium vanadomolybdate spectrophotometry. For example, a predetermined amount of removal agent is decomposed using nitric acid or perchloric acid, followed by the addition of ammonium vanadate(V), hexaammonium heptamolybdate, and nitric acid. The total phosphate is quantified by measuring the absorbance of the resulting phosphovanadomolybdate (e.g., at 420 nm) using a UV-visible spectrophotometer.

[0017] 1-2. Binder The binder is used in the manufacturing process of the remover, which will be described later, and contributes to shaping and maintaining the shape of the remover. There are no restrictions on the type of binder, and organic and / or inorganic binders can be used. Examples of organic binders include one or more selected from the group consisting of molasses, blackstrap molasses, starch, dextrin, cornstarch, rice bran, polyvinyl alcohol, vinyl acetate-ethylene copolymers or their saponified forms, pulp waste liquor, lignin sulfonate, carboxymethyl cellulose, hydroxypropyl methyl cellulose, sodium alginate, phenolic resin, and tar pitch. Molasses, among others, is inexpensive, contains few harmful components, and has a high solid content, making it easy to shape the remover. Examples of inorganic binders include cement, ground granulated blast furnace slag, fly ash, gypsum (calcium sulfate), calcined gypsum obtained by heating and dehydrating gypsum, and sodium silicate.

[0018] 1-3.Iron and iron compounds The iron contained in the phosphorus-containing porous carbide is zero-valent iron, which is added as iron powder during the manufacturing process of the removal material.

[0019] Examples of iron compounds include iron oxide, iron hydroxide, iron phosphate, and iron pyrophosphate. The iron ions in these compounds may be divalent, trivalent, or a mixture of divalent and trivalent. Iron compounds may be produced by partial oxidation of the iron powder described above or by immobilization of a phosphorus-containing compound described below, or may exist as iron oxide powder. The iron oxide powder may contain iron hydroxide.

[0020] 1-4. Compounds of alkali metals and alkaline earth metals Examples of compounds of metals selected from alkali metals and alkaline earth metals include halides, oxides, hydroxides, sulfates, and nitrates of sodium, potassium, lithium, cesium, magnesium, and calcium. These compounds may be added during the production of the remover, but when biomass is used as the raw material for the phosphorus-containing porous carbide, they may also be compounds of alkali metals or alkaline earth metals contained in the biomass.

[0021] 1-5.Composition ratio The composition ratios of the above-mentioned components can be adjusted as appropriate. For example, the content of the phosphorus-containing porous carbide in the remover may be adjusted to within a range of 50% by mass to 95% by mass, 50% by mass to 85% by mass, or 50% by mass to 80% by mass. The content of the binder may be adjusted to within a range of 5% by mass to 50% by mass, 15% by mass to 50% by mass, or 20% by mass to 50% by mass.

[0022] Alternatively, the composition ratios of the above-mentioned configuration may be appropriately adjusted so that the carbon content in the remover is in the range of 10% by mass to 80% by mass, the iron content (i.e., the content of iron elements including zero-valent iron and iron ions) is in the range of 5% by mass to 35% by mass, the sum of the contents of metals selected from alkali metals and alkaline earth metals is in the range of 1% by mass to 30% by mass, and the total phosphoric acid concentration is in the range of 0.1% by mass to 30% by mass, 0.5% by mass to 25% by mass, or 1% by mass to 20% by mass. Note that the carbon content in the remover is the content of carbon mainly derived from the phosphorus-containing porous carbide and the binder.

[0023] The carbon content in the removal material can be determined, for example, using the combustion and infrared absorption method, in accordance with JIS H1617, JIS Z2615, and ASTM E1941. Specifically, the removal material is burned in a combustion furnace under an oxygen stream to generate carbon dioxide. The generated carbon dioxide is introduced into an infrared analyzer using oxygen gas, and the carbon dioxide concentration is determined by measuring its absorption with a detector. The carbon dioxide content in the removal material can be calculated from this carbon dioxide concentration.

[0024] The sum of the alkali metal and alkaline earth metal content can be measured by applying inductively coupled plasma optical emission spectroscopy (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS) to the removal material. ICP-OES uses argon plasma as the light source. By introducing an atomized solution sample into the plasma, the unique spectra of alkali metals and alkaline earth metals are analyzed. The alkali metals and alkaline earth metals can be quantified based on the measured wavelength and emission intensity. ICP-MS uses argon plasma as the ion source to ionize the elements contained in the sample, and the ions are separated and detected based on their mass-to-charge ratio. The elements can be identified from the mass-to-charge ratio of the detected ions, and the alkali metals and alkaline earth metals can be quantified by counting the detected ions. The iron content can also be measured by applying ICP-OES or ICP-MS to the removal material. 2. Manufacturing method of removal material 2-1. Preparation of porous carbide An example of a manufacturing method for a removal material is shown in the flowchart of Figure 1. First, a porous carbide is prepared. The porous carbide can be obtained by using an organic material such as biomass as a raw material and heating the organic material under an inert gas atmosphere such as nitrogen gas or argon gas, an oxygen-free atmosphere, a low-oxygen atmosphere, a reducing atmosphere, or a reduced-pressure atmosphere. When carbonization is performed under a reduced-pressure atmosphere, 10 2 Pa or more 10 5 Low vacuum state below 10 Pa -1 Pa or more 10 2 Medium vacuum state below 10 Pa -5 Pa or more 10 -1 High vacuum state of less than 10 Pa or -5 The carbonization can be carried out in an ultra-high vacuum of 100 Pa or less. When carbonization is carried out in a low-oxygen atmosphere, the oxygen concentration can be set to 0.01% to 3%, or 0.1% to 2%. The heating temperature for carbonization can be 400°C to 1200°C, 500°C to 1100°C, 600°C to 1000°C, or 600°C to 900°C. The heating time can be 10 minutes to 10 days, or 10 minutes to 5 hours.

[0025] Carbonization is carried out using an internal combustion or externally heated carbonization furnace. Examples of carbonization furnaces include batch-type sealed charcoal kilns, continuous rotary kilns, rocking carbonization furnaces, and screw furnaces. Carbonization of biomass generates carbonization gases, and a porous carbide is produced, with pores of various shapes and sizes formed by a complex mixture of pores due to the structure of the biomass and pores formed by the desorption of the carbonization gases. As described below, iron powder and / or iron oxide powder are mixed with the porous carbonization material to manufacture the removal material. Some of the mixed iron powder or iron oxide powder is captured in the pores of the porous carbide, capturing iron and iron compounds on the surface and inside of the porous carbide, which is thought to contribute to the removal of nitrogen oxides and sulfur oxides. The carbonization gases primarily contain flammable or reducing gases, such as hydrogen, carbon monoxide, and alkanes, such as methane, propane, and butane. Since the dry distillation gas is extracted at a high temperature (700 to 1300°C), its thermal energy and flammability can be used as an energy source for generating electricity or supplying hot water.

[0026] 2-2. Preparation of iron-containing carbides Next, the porous carbide is mixed with iron powder and / or iron oxide powder and a binder to prepare an iron-containing carbide. At this time, the iron-containing carbide may be prepared so that the porous carbide content is 20% by mass to 80% by mass, 40% by mass to 80% by mass, or 60% by mass to 80% by mass, the iron powder content is 5% by mass to 35% by mass, 5% by mass to 25% by mass, or 5% by mass to 20% by mass, and the binder content is 5% by mass to 50% by mass, 15% by mass to 50% by mass, or 20% by mass to 50% by mass.

[0027] There are no restrictions on the shape of the iron powder or iron oxide powder; for example, iron powder and / or iron oxide powder with an average circularity of 50 to 100, 70 to 95, or 80 to 90 may be used. Here, average circularity is one of the parameters that describe the shape of each particle contained in the powder. It is calculated by analyzing an image obtained by observing the powder under a microscope, determining the circularity of multiple iron particles, and averaging the results. The circularity can be calculated, for example, by dividing the perimeter of a circle with an area equal to the area of ​​the projection of each particle in the microscope image by the perimeter of the projection. Alternatively, the circularity can be calculated by dividing the area of ​​the projection by the area of ​​a circle inscribed in the projection.

[0028] The average particle size of the iron powder or iron oxide powder is relatively large, 20 μm or more and 500 μm or less, or 50 μm or more and 200 μm or less. Furthermore, iron powder having a particle size distribution in which, of all iron particles contained in the iron powder, 1) the proportion of iron particles having a particle size in the range of 1 μm to less than 150 μm is 3% to 70% by mass, 2) the proportion of iron particles having a particle size in the range of 1 μm to less than 75 μm is 0% to 25% by mass, 3) the proportion of iron particles having a particle size in the range of 1 μm to less than 45 μm is 0% to 15% by mass, 4) the proportion of iron particles having a particle size in the range of 150 μm to less than 2000 μm is 30% to 99% by mass, and 5) the proportion of iron particles having a particle size in the range of 600 μm to less than 2000 μm is 0% to 15% by mass, and at the same time, the sum of the proportion of iron particles in at least one of 1) to 3) and the proportion of iron particles in 4) or 5) is 100% by mass. Using iron powder satisfying these parameters can suppress the ignition potential of iron-containing carbides and the removal agent, allowing for the safe production of a highly safe removal agent. Here, the average particle size of iron powder or iron oxide powder refers to the average value of particle sizes determined for multiple iron particles by analyzing an image obtained by observing the iron powder or iron oxide powder under a microscope. The particle size of each iron particle or iron oxide powder can be, for example, the diameter of a circle inscribed in the projection plane of each particle in the microscope image or the length of one side of a square. The particle size, particle size distribution, and circularity of the iron oxide powder may be the same as those of the iron powder.

[0029] The iron powder may contain trace amounts of other elements, such as carbon, oxygen, sulfur, phosphorus, manganese, silicon, vanadium, copper, and titanium. Therefore, the purity of the iron powder may be 90.0% to 99.9% or 95.0% to 99.0%. Note that some of the iron powder may be oxidized, i.e., contained in the removal material as iron compounds such as iron oxide and hydroxide.

[0030] Before mixing the porous carbide with the iron powder and / or iron oxide powder, the particle size may be adjusted by crushing or classifying the porous carbide in advance. Since the particle size of the porous carbide is often larger than that of the iron powder or iron oxide powder, crushing the porous carbide to have a particle size approximately the same as that of the iron powder or iron oxide powder allows them to be mixed more uniformly.

[0031] After mixing the porous carbide, binder, and iron powder and / or iron oxide powder, the mixture is kneaded (mixed). A single-screw mixer, twin-screw mixer, mixing roll, kneader, Banbury mixer, or the like may be used as the mixer. For example, the porous carbide and iron powder and / or iron oxide powder are introduced into the mixer and mixed, and then the binder is introduced into the mixer and mixed. The binder may be added all at once, intermittently, or continuously. By adding the binder after mixing the porous carbide and iron powder and / or iron oxide powder and mixing, aggregation of the porous carbide and the iron powder or iron oxide powder can be prevented and foaming can be suppressed. The mixing temperature can be set as desired, for example, between 0°C and 50°C, or between 10°C and 40°C. The kneading time can also be set appropriately taking into consideration the mixing ratio and amount of raw materials, the type of binder, the capacity of the kneader, etc., and can be set within the range of, for example, from 1 second to 1 hour, from 1 minute to 30 minutes, or from 1 minute to 15 minutes.

[0032] Water is added as needed during mixing and kneading. Adding water prevents dust generation and allows the porous carbide to be mixed more uniformly with the iron powder and / or iron oxide powder. Furthermore, an alkali metal and / or alkaline earth metal compound may be added during mixing and kneading. Through the above steps, an iron-containing carbide is obtained, which is a mixture of porous carbide, binder, and iron powder and / or iron oxide powder.

[0033] As mentioned above, iron powder may contain trace amounts of iron compounds. Furthermore, some of the iron powder may be oxidized during the mixing and kneading process. In this case, even if iron oxide powder is not used, the final removed material will contain iron oxide as an iron compound.

[0034] As an optional step, the iron-containing carbide may be granulated and molded into a certain shape. The molding of the iron-containing carbide can be carried out using a granulator. Examples of the granulator include a compression granulator, an extrusion granulator, a roll granulator, a blade granulator, a melt granulator, and a spray granulator.

[0035] When using an extrusion granulator, a paste-like iron-containing carbide formed into a predetermined shape is extruded from a die attached to the granulator. The extruded iron-containing carbide is cut to a predetermined length and formed into pellets with the extrusion direction being the height direction. The length of the iron-containing carbide (the height of the pellet shape) can be adjusted by adjusting the extrusion speed and cutting speed of the iron-containing carbide in the extrusion granulator (or the rotation speed of the cutter in the case of a rotary cutting method). In addition, the diameter of the iron-containing carbide (the diameter if the cross-sectional shape is circular) can be adjusted by adjusting the opening diameter of the die. Therefore, by using an extrusion granulator, it is possible to obtain iron-containing carbide having a pellet shape with a controlled size (for example, an approximately cylindrical shape).

[0036] The size of the pellet shape can be set arbitrarily, for example, the length of each pellet can be 1 mm to 20 mm, 3 mm to 15 mm, or 6 mm to 12 mm. If the cross section is circular, the diameter of the pellet can be 1 mm to 20 mm, 2 mm to 10 mm, or 3 mm to 8 mm.

[0037] The cross-sectional shape (cross-section perpendicular to the longitudinal direction) of the formed iron-containing carbide is not limited to a circle. The cross-sectional shape of the iron-containing carbide may be, for example, an ellipse or a polygon. That is, the formed iron-containing carbide may be not only cylindrical but also an elliptical or polygonal prism pellet shape. The cross-sectional shape of the iron-containing carbide can be changed by changing the opening shape of the die. The high viscosity of the binder maintains the shape of the formed iron-containing carbide. This granulation process may be performed after the drying process described below.

[0038] Furthermore, as an optional step, the iron-containing carbide may be subjected to a drying (curing) step. The drying temperature and time are also appropriately selected depending on the amount of iron-containing carbide and the amount of water contained therein. For example, the drying temperature may be selected from the range of 30°C or higher but lower than 400°C, 50°C or higher but lower than 300°C, or 100°C or higher but lower than 300°C. The humidity during drying may be 20% or higher but lower than 95%, or 50% or higher but lower than 90%. The drying time may also be appropriately selected from the range of 1 minute or higher but lower than 1 week, 1 hour or higher but lower than 3 days, or 3 hours or higher but lower than 1 day. The atmosphere during drying may be, for example, air, nitrogen, a rare gas such as argon, or a mixture of these.

[0039] 2-3. Fixation of phosphorus-containing compounds Subsequently, the phosphorus-containing compound is immobilized on the porous carbide contained in the iron-containing carbide. That is, the iron or iron compound mixed with the porous carbide is brought into contact with the phosphorus-containing compound, and the phosphorus-containing compound is adsorbed and immobilized on the porous carbide.

[0040] Specifically, the removal material is produced by contacting iron-containing carbide with water containing phosphorus-containing compounds, including at least phosphoric acid (hereinafter, "treated water"). The contact with the treated water can be carried out at room temperature. The contact time is determined appropriately depending on the concentration of the phosphorus-containing compounds in the treated water, the amount of iron-containing carbide, and other factors, and can be selected, for example, from one day to six months or from one day to three months. The treated water can be prepared by dissolving phosphates, such as sodium phosphate or potassium phosphate, in water. However, water from bodies of water, such as rivers, lakes, and oceans, where phosphorus-containing compounds exist, or separated sludge from sewage treatment plants can also be used as the treated water. For example, a container filled with iron-containing carbide can be placed in a river, lake, or ocean, and the iron-containing carbide can be contacted with the water from the body of water. This allows the phosphorus-containing compounds in the river, lake, or ocean to react with the iron, iron oxide, and / or iron hydroxide contained in the iron-containing carbide, resulting in the adsorption or immobilization of iron(III) phosphate, which has low solubility in water, onto the porous carbide, and the phosphorus-containing compounds in the water can be removed. This method not only enables the production of a removal material at low cost, but also enables the purification and improvement of water quality in various water bodies at the same time. The total phosphorus concentration in the removal material can be controlled by the surface area of ​​the porous carbide, the amount of iron powder or iron oxide powder used, the concentration of phosphorus-containing compounds in the treated water, the contact time and temperature with the treated water, etc.

[0041] After the treatment with the treatment water is completed, the removal material is dried. The drying temperature may be from room temperature to 100°C or less, and the drying time may be appropriately selected from the range of, for example, from one hour to one month.

[0042] In the production of the remover according to one embodiment of the present invention, no high-temperature treatment step is required; for example, heating at a temperature (e.g., 400°C or higher) required to carbonize the binder is not required. Furthermore, drying and curing of the remover can be carried out at a temperature of 100°C or less. This eliminates the need for energy for high-temperature treatment steps, making it possible to provide the remover at lower cost.

[0043] As described above, the method for producing a remover according to one embodiment of the present invention allows the use of iron powder with a relatively large particle size. Therefore, even when the remover is produced using iron powder, the ignition potential of the precursor iron-containing carbide and the remover is significantly reduced, allowing the remover to be produced and handled as a highly safe, non-hazardous substance. Furthermore, as shown in the examples, the remover exhibits the function of removing nitrogen oxides and sulfur oxides without the need for a separate reducing agent. Therefore, the remover according to one embodiment of the present invention can be said to be a remover that combines high nitrogen oxide and sulfur oxide removal capabilities with safety.

[0044] 3. Methods for removing air pollutants To remove air pollutants using a removal material according to one embodiment of the present invention, a gas containing nitrogen oxides and / or sulfur oxides (hereinafter, the gas to be treated) is brought into contact with the removal material. For example, the removal material may be packed into a column or cartridge made of resin, glass, metal, or the like, and the gas to be treated may be introduced into one end and the treated gas may be collected from the other end. Alternatively, the gas to be treated may be sprayed onto the removal material while moving the removal material using a conveyor such as a screw conveyor. As shown in the examples, this removal material is capable of removing nitrogen oxides even at room temperature. Therefore, there is no need to heat the removal material or the gas to be treated.

[0045] The gas to be treated may contain carbon dioxide. For example, the gas to be treated may be exhaust gas emitted from a reciprocating engine, or may be gas emitted from facilities that emit large amounts of carbon dioxide, such as chemical plants, waste incineration facilities, thermal power plants, and various other factories. The gas to be treated may be gas that has been previously de-dusted, or may be gas that has been brought into contact with a removing material and then de-dusted.

[0046] As shown in the examples, this removal material removes a certain amount of carbon dioxide from the gas to be treated, but can also remove air pollutants almost selectively. Therefore, the gas (recovered gas) obtained by treating the gas to be treated with the removal material contains carbon dioxide at a concentration similar to that of the gas to be treated. For this reason, this recovered gas can also be supplied for plant growth or microalgae cultivation.

[0047] 4. Fertilizers and their manufacturing methods Because phosphorus-containing compounds function as nutrients that promote the growth of various plants, removal materials containing phosphorus-containing porous carbides can also function as fertilizers. Therefore, the removal material after removing air pollutants can also be used as a phosphorus-containing fertilizer. Furthermore, when carbon dioxide is present in nitrogen oxide-containing gases, alkali metal and alkaline earth salts are carbonated. In particular, when cement or ground blast furnace slag is used as a binder, these contain large amounts of calcium hydroxide and calcium oxide. Therefore, spreading iron-containing carbides on soil without carbonation increases the soil pH. However, when the removal material comes into contact with carbon dioxide, the calcium hydroxide and calcium oxide are converted to calcium carbonate or calcium bicarbonate. Therefore, using the removal material as a fertilizer does not increase the soil pH.

[0048] A fertilizer according to one embodiment of the present invention reflects the manufacturing process of the remover described above and includes a phosphorus-containing porous carbide and a binder. The fertilizer further includes one or more fertilizer components selected from the group consisting of nitrogen, potassium, calcium, magnesium, manganese, silica, and boron. Specific examples of the fertilizer include oil cake, flavored chicken droppings, fish meal, bone meal, rice bran, bat guano, compost, wood ash, lime, and chemical fertilizer.

[0049] FIG. 2 shows a flowchart of an example of a method for producing a fertilizer according to an embodiment of the present invention. The fertilizer is obtained by mixing the removal material, from which air pollutants have been removed, with a fertilizer aid. The removal material may be crushed before mixing with the fertilizer aid. The obtained fertilizer may be crushed as needed to increase the surface area. Crushing may be performed using a crusher such as a vibration mill, jet mill, ball mill, roller mill, rod mill, hammer mill, impact mill, rotary mill, pin mill, pin-disk mill, or planetary mill. Crushing increases the surface area, thereby facilitating the release of phosphorus-containing compounds fixed on the removal material.

[0050] Furthermore, the crushed fertilizer may be classified to adjust the particle size to suit the intended use. There are no restrictions on the structure or type of classifier, and either a dry classifier or a wet classifier may be used. Examples of classifiers include air classifiers, gravity field classifiers, inertial field classifiers, and centrifugal field classifiers.

[0051] The fertilizer may then be mixed with materials containing the above-mentioned fertilizer components using a mixer such as a free-fall mixer, a forced mixer, a Y-branch mixer, an agitator mixer, or a paddle mixer.

[0052] The resulting fertilizer is spread on the soil to help plants grow. There are no restrictions on the method of spreading the fertilizer into the soil; for example, a gravity-drop spreader such as a ground sower or a diffusion-type spreader that uses compressed air can be used. There are also no restrictions on the application method; either a stripe-type spreader or an all-over-area spreader can be used. It is preferable to spread the fertilizer within 30 cm of the soil surface. Spreading the fertilizer promotes plant growth. In other words, carbon dioxide from the atmosphere is fixed through plant photosynthesis, creating resources that can be used as food and materials.

[0053] 5. Carbon dioxide storage As described above, the porous carbide used as the raw material for the removal material can be obtained by carbonizing biomass. That is, porous carbide is produced by effectively utilizing plant-derived biomass produced by the fixation of carbon dioxide through photosynthesis. Furthermore, iron-containing carbide prepared from this porous carbide is treated with treated water containing at least phosphoric acid to remove phosphorus-containing compounds, such as phosphoric acid, contained in the treated water. Therefore, the production of the removal material also contributes to improving water quality. Furthermore, by using the resulting removal material to remove air pollutants, a portion of the carbon dioxide contained in the gas can be fixed in the removal material. In addition, applying the removal material with immobilized phosphorus-containing compounds to soil as fertilizer promotes plant growth, while simultaneously storing the carbon dioxide fixed by the plants as carbide underground.

[0054] More specifically, as shown in FIG. 3, according to an embodiment of the present invention, biomass is carbonized to produce porous carbide (1), and iron-containing carbide is then produced from the porous carbide (2). This iron-containing carbide can be used to improve water quality (3) and also contribute to the removal of air pollutants (4). The removal material is then spread on soil as fertilizer (5) and used to grow plants. Plants fix atmospheric carbon dioxide through photosynthesis, providing food and structural materials (6) and by-producing biomass. The cycle established by this series of processes (1) to (6) improves water and air quality and also stores atmospheric carbon dioxide underground. Therefore, the use of a removal material according to one embodiment of the present invention can also contribute to the reduction of greenhouse gases. [Example]

[0055] The following describes the preparation of a remover according to one embodiment of the present invention and the results of evaluating the remover.

[0056] 1. Preparation of removal material Irregularly shaped charcoal (waste charcoal from woody biomass gasification power generation) was used as the raw porous carbide material. This charcoal was mixed with iron powder and iron oxide powder, including 45% by mass of iron particles with a particle size ranging from 300 μm to 2000 μm, 45% by mass of iron particles with a particle size ranging from 75 μm to 300 μm, and 10% by mass of iron particles with a particle size ranging from 1 μm to 75 μm, ground granulated blast furnace slag as a binder, and water, and kneaded for 30 minutes at room temperature to obtain a powder mixture. The resulting powder mixture was then placed in a granulator and formed into pellets with a diameter of 4 mm and a height of 10 mm. The formed powder mixture was then dried (cured) at 20°C for 24 hours to obtain an iron-containing carbide.

[0057] A digested sludge dewatered separated liquid containing 100 mg / L of phosphoric acid was passed through a column packed with 3,000 g of the obtained iron-containing carbide at a flow rate of 23 L / day for 12 days. The sewage sludge dewatered separated liquid used here was a filtrate obtained by centrifuging sludge at a sewage treatment plant in Kanagawa Prefecture. This treatment was carried out at room temperature. The iron-containing carbide was then dried at room temperature for 24 hours to obtain a removal material (Example 1).

[0058] The total phosphorus concentration and carbon composition of the removal material in Example 1, measured using ammonium vanadomolybdate absorptiometry and combustion / infrared absorption spectroscopy, were 2.3% by mass and 38.5% by mass, respectively. Table 1 summarizes the concentrations of various metal ions measured using ICP-MS.

[0059] [Table 1]

[0060] 2. Evaluation of carbon dioxide and nitrogen oxide removal capacity The removal material of Example 1 was packed into a glass column with an inner diameter of 30 mm and a height of 450 mm. The height of the removal material within the column was 210 mm. A gas to be treated, containing nitrogen oxides (including nitric oxide and nitrogen dioxide), carbon dioxide, and nitrogen, was introduced into one end of the column at a flow rate of 50 mL / min at room temperature. The concentrations of nitrogen oxides and carbon dioxide in the gas to be treated were 185 ppm and 15%, respectively. The concentrations of carbon dioxide and nitrogen oxides in the gas discharged from the other end (recovered gas) were measured using a carbon dioxide concentration meter (Vaisala, handheld CO2 meter GM70), a dry-type on-board measuring instrument (Gastec Corporation, nitrogen oxide detector tube, model GV-100S), and a detector tube (Gastec Corporation, nitrogen oxide detector tube, model 10), respectively. The removal capacities for carbon dioxide and nitrogen oxide were evaluated based on the differences in carbon dioxide and nitrogen oxide concentrations between the gas to be treated and the recovered gas. As Comparative Examples 1 to 3, similar experiments were conducted using porous carbide, which was an intermediate of the removal material in Example 1 before being mixed with iron powder, commercially available zeolite (natural hard zeolite 3-8 mm, manufactured by Hokkaido Zeolite Co., Ltd.), and activated carbon (Granular Shirasagi, model number WH2x, manufactured by Osaka Gas Chemicals Co., Ltd.).

[0061] The changes over time in the concentrations of carbon dioxide and nitrogen oxides in the recovered gas are shown in Figures 4 and 5, respectively. Regarding the carbon dioxide removal capacity, as shown in Figure 4, in Example 1, the carbon dioxide concentration in the recovered gas became constant within one day, reaching the same level as the carbon dioxide concentration in the gas to be treated, as in the activated carbon in Comparative Example 3. On the other hand, in Comparative Examples 1 and 2, it took about three days for the carbon dioxide concentration in the recovered gas to reach the same level as the carbon dioxide concentration in the gas to be treated.

[0062] On the other hand, with regard to the nitrogen oxide removal capacity, in the case of the removal material of Example 1, the nitrogen oxide concentration in the recovered gas discharged immediately after the introduction of the gas to be treated was extremely low, indicating that the nitrogen oxides were removed almost quantitatively (Figure 5). Although the nitrogen oxide removal capacity gradually decreased thereafter, it became constant approximately one day after the start of the introduction of the gas to be treated, confirming that approximately 50% of the nitrogen oxides in the gas to be treated could be steadily removed for five days or more. In other words, it was found that the removal material according to one embodiment of the present invention can efficiently remove nitrogen oxides selectively and for a long period of time, even at room temperature. Furthermore, as described above, in Example 1, the carbon dioxide removal capacity disappears in a short period of time, and therefore, it is possible to ensure a long period during which the recovered gas containing carbon dioxide can be used for plant growth and other purposes while removing air pollutants.

[0063] On the other hand, when zeolite, a type of porous material, was used as the removal material (Comparative Example 2), the nitrogen oxide concentration in the recovered gas was almost the same as that in the treated gas (185 ppm), indicating that zeolite has no ability to remove nitrogen oxides. The results of Comparative Example 1 are interesting. Comparative Example 1 was an experiment using porous carbide not mixed with iron powder or iron oxide powder. Although the nitrogen oxide concentration in the recovered gas immediately after introduction of the treated gas was low, after several hours it was almost the same as that in the treated gas. This indicates that although the removal material of Comparative Example 1 has the ability to remove nitrogen oxides, it quickly loses this ability. Therefore, it can be seen that iron and / or iron compounds play an important role in the removal of nitrogen oxides in a removal material according to one embodiment of the present invention.

[0064] On the other hand, the plot for activated carbon (Comparative Example 3), which is a type of porous carbonized material, is very similar to the plot for Example 1. From this, it can be said that activated carbon also has the ability to remove nitrogen oxides. However, as will be described later, a removal material according to one embodiment of the present invention removes nitrogen oxides through a mechanism different from that of activated carbon.

[0065] 3. Examination of nitrogen oxide removal mechanism Figure 6 shows the cumulative mass of nitrogen in nitrogen oxides removed from the treated gas (cumulative nitrogen removal rate) relative to the mass of the removal material of Example 1 and the sample of Comparative Example 3. As can be seen from Figure 6, in both Example 1 and Comparative Example 3, the nitrogen oxide removal capacity can be maintained for approximately 80 days (including a 25-day interruption period). From the results of Figure 6, it can be seen that the removal material of Example 1 removed approximately 0.19% by mass of nitrogen from the treated gas relative to the mass of the removal material at the end of the test. Similarly, it can be seen that the activated carbon of Comparative Example 3 removed approximately 0.25% by mass of nitrogen from the treated gas relative to the mass of the activated carbon at the end of the test.

[0066] Here, the nitrogen content in the removal material and activated carbon obtained from elemental analysis of the removal material of Example 1 and the activated carbon of Comparative Example 3 before and after the test is shown in Figure 7. As described above, the removal material of Example 1 removed approximately 0.19 mass% of nitrogen relative to the removal material from the start to the end of the test (Figure 6), but the increase in nitrogen content was small, remaining at 0.06 mass%. In other words, it can be seen that most of the removed nitrogen was not present in the removal material. In light of this result, it is suggested that the mechanism of nitrogen oxide removal by the removal material of Example 1 cannot be explained solely by nitrogen oxide adsorption, but rather that decomposition of nitrogen oxides also contributes.

[0067] On the other hand, in Comparative Example 3, the increase in nitrogen content reached approximately 0.15%, which was approximately 60% of the cumulative nitrogen removal rate (0.25%). This suggests that the decomposition mechanism also contributes to the removal of nitrogen oxides by the activated carbon in Comparative Example 3, but the degree of this contribution is relatively small, and it can be said that the contribution of adsorption is greater than in Example 1. Therefore, it is thought that nitrogen oxides are adsorbed on the activated carbon after treatment, and that re-release of nitrogen oxides due to desorption may occur.

[0068] As described above, it has been found that a removal material according to one embodiment of the present invention has excellent selective nitrogen oxide removal capabilities even at room temperature. Furthermore, nitrogen oxide removal proceeds even at room temperature without the need for heating or the addition of a reducing agent. Therefore, by applying one embodiment of the present invention, it is possible to provide a removal material that not only improves water quality but also has a high effect on improving air quality. Furthermore, because this removal material contains a phosphorus-containing compound, it can also be used as a fertilizer.

[0069] The above-described embodiments of the present invention can be combined as appropriate as long as they are not mutually inconsistent. A product in which a person skilled in the art appropriately adds or deletes components or modifies the design based on each embodiment is also included within the scope of the present invention as long as it includes the gist of the present invention.

[0070] Even if there are other effects and advantages different from those brought about by the above-described embodiments, those that are clear from the description in this specification or that can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention.

Claims

1. a porous carbide comprising a phosphorus-containing compound, and including a binder, An air pollutant removal material having an iron element content of 5% by mass or more and 35% by mass or less.

2. The remover according to claim 1 , wherein the total phosphoric acid concentration is 0.1% by mass or more and 30% by mass or less.

3. The remover according to claim 1 , wherein the carbon content is 10% by mass or more and 80% by mass or less.

4. A method for producing an air pollutant removal material, comprising: Carbonizing biomass to prepare a porous carbonized material; mixing the porous carbide with a binder and iron powder and / or iron oxide powder to prepare an iron-containing carbide; and contacting the iron-containing carbide with water containing at least phosphoric acid; The porous carbide, the binder, and the iron powder and / or the iron oxide powder are mixed so that the iron element content in the remover is 5 mass % or more and 35 mass % or less.

5. The method according to claim 4 , wherein the water containing phosphoric acid is brought into contact with the iron-containing carbide so that a total phosphoric acid concentration in the remover is 0.1 mass % or more and 30 mass % or less.

6. 5. The manufacturing method according to claim 4, wherein the porous carbide, the binder, and the iron powder and / or the iron oxide powder are mixed so that a carbon content in the removal material is 10 mass % or more and 80 mass % or less.

7. 5. The manufacturing method according to claim 4, wherein the porous carbide, the binder, and the iron powder and / or the iron oxide powder are mixed so that the content of the porous carbide is 20% by mass or more and 80% by mass or less, and the content of the binder is 10% by mass or more and 50% by mass or less.

8. The method includes contacting a gas containing air pollutants with a removal material, The removal material is a porous carbide comprising a phosphorus-containing compound, and including a binder, The method for removing air pollutants, wherein the removal material has an iron element content of 5% by mass or more and 35% by mass or less.

9. The removal method according to claim 8, further comprising preparing the removal material by treating the iron-containing carbide including the porous carbide, iron powder, and the binder with water containing phosphoric acid.

10. A removal method as described in claim 8, wherein the carbon content of the removal material is 10 mass% or more and 80 mass% or less.

11. contacting a gas containing air pollutants with a removal material; mixing the removal material with a fertilizer aid; The removal material is a porous carbide comprising a phosphorus-containing compound, and including a binder, The method for producing a fertilizer, wherein the removal material has an iron element content of 5% by mass or more and 35% by mass or less.

12. A manufacturing method as described in claim 11, wherein the carbon content of the removal material is 10 mass% or more and 80 mass% or less.

Images