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

Abstract

To provide a novel carbide-based removal material and a manufacturing method thereof capable of removing an air pollutant such as nitrogen oxides and sulfur oxides, and a removal method of the air pollutant.SOLUTION: A removal material includes porous carbide, binders, and iron and / or iron oxide powders. The iron powder and / or the iron oxide powder may each have an average particle size of 20 μm or more and 500 μm or less. The content of porous carbide may be 20 mass% or more and 80 mass% or less, the content of binder may be 10 mass% or more and 50 mass% or less, and the content of iron powder and / or iron oxide powder may be 5 mass% or more and 35 mass% or less.SELECTED DRAWING: Figure 1

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. [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 modify soil. [Means for solving the problem]

[0005] One embodiment of the present invention is a material for removing air pollutants, which comprises porous carbide, a binder, and iron powder and / or iron oxide powder.

[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 charcoal, and mixing the porous charcoal with a binder and iron powder and / or iron oxide powder.

[0007] One embodiment of the present invention is a method for removing air pollutants. The method includes contacting a gas containing the air pollutants with a removing material. The removing material includes a porous carbide, a binder, and iron powder and / or iron oxide powder. [Effects of the Invention]

[0008] The removal material according to the embodiment of the present invention contains porous charcoal produced from carbon dioxide and has the function of removing air pollutants such as nitrogen oxides, sulfur oxides, etc. Therefore, the embodiment of the present invention makes it possible to improve air quality and store carbon dioxide, and also contributes to soil improvement for plant growth. [Brief explanation of the drawings]

[0009] [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 conceptual diagram illustrating air quality improvement, carbon dioxide sequestration, and soil remediation using a removal material according to one embodiment of the present invention. [Figure 3] 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 4] 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 5] 1 is a cumulative plot of nitrogen in nitrogen oxides removed using the removal material of Example 2 and the sample of Comparative Example 4. [Figure 6]10 is a graph showing the nitrogen content of the removal material of Example 2 and the sample of Comparative Example 4 before and after a nitrogen oxide removal test. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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.

[0011] Hereinafter, a removal material according to one embodiment of the present invention, a method for producing the same, a method for removing air pollutants using the removal material, and storage of carbon dioxide will be described.

[0012] 1. Composition of removal material The remover has a porous carbide as a basic skeleton, and further contains iron (zero-valent iron) and / or an iron compound, and a binder. Furthermore, the remover may contain a compound of a metal selected from alkali metals and alkaline earth metals. Each component constituting the remover will be described below.

[0013] 1-1.Porous carbide Porous charcoal is produced by heating and carbonizing organic matter under conditions of low oxygen concentration. An example of organic matter is biomass. Biomass refers to a type of organic matter, namely, substances derived from living organisms and their metabolites. Examples of biomass include wood-derived materials. Specific examples include planks and columns of wood, thinnings, pruning waste, construction waste, powdered sawdust, and wooden molded products such as particle boats. There are no restrictions on the type of wood, and it can be cedar, cypress, or bamboo. Other examples of biomass include agricultural waste such as rice husks, bagasse, corn cobs, and leaves, as well as agricultural by-products such as straw, wheat straw, and hay. Other examples include plants that are used to produce fibers, such as hemp, flax, cotton, sisal, abaca, and palm fiber. Seaweed and other algae are also suitable. Other examples include food waste and silage obtained from animal waste.

[0014] The size and shape of the porous carbide are not particularly limited, but the average particle size of the porous carbide is preferably 1 μm to 50 mm or 1 μm to 1 mm. By having the average particle size within this range, the porous carbide, iron powder, and iron oxide powder can be uniformly mixed in the mixing and kneading steps described below.

[0015] Due to the pores formed inside, porous carbonized materials have a relatively large specific surface area, although it is smaller than fibrous activated carbon. Specifically, the specific surface area of ​​porous carbonized materials is 100 m 2 / g or more 900m 2 / g or less, 100m 2 / g or more 800m 2 / g or less, or 150m 2 / g or more 400m 2 The specific surface area is measured by mercury intrusion porosimetry or a gas adsorption method such as the BJH method or HK method.

[0016] 1-2.Iron and iron compounds The iron contained in the remover is elemental zero-valent iron, and is added to the porous carbide as iron powder. There are no restrictions on the shape of the iron powder; for example, iron 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 represent the shape of each iron particle contained in the iron powder. Images obtained by observing the iron powder under a microscope are analyzed to determine the circularity of multiple iron particles, and the average value is calculated. For example, the circularity can be calculated by dividing the perimeter of a circle with an area equal to the area of ​​the projection surface of each iron particle in the microscope image by the perimeter of the projection surface of the iron particle. Alternatively, the circularity can be calculated by dividing the area of ​​the projection surface by the area of ​​a circle inscribed in the projection surface.

[0017] The iron powder has a relatively large average particle size, ranging from 20 μm to 500 μm or from 50 μm to 200 μm. Furthermore, the iron powder may have a particle size distribution in which, of all the 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% by mass 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% by mass 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% by mass 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% by mass 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% by mass to 15% by mass, and simultaneously, 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. The use of iron powder that satisfies the above parameters can suppress ignition. Here, the average particle size of the iron powder is the average value obtained by analyzing an image obtained by observing the iron powder under a microscope and determining the particle sizes of multiple iron particles. The particle size of each iron particle can be, for example, the diameter of a circle inscribed in the projection plane of each iron particle in the microscope image or the length of one side of a square.

[0018] 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%.

[0019] Note that a portion of the iron powder may be contained in the removal material in an oxidized state, i.e., as an iron compound. Examples of iron compounds include iron oxide and iron hydroxide. The iron contained in the iron compound may be in a divalent, trivalent, or mixed valence state (a mixture of divalent and trivalent).

[0020] The iron compound contained in the remover may be iron oxide or iron hydroxide produced by partial oxidation of iron powder, or may be added to the porous carbide as iron oxide powder. Iron oxide powder may be divalent, trivalent, or mixed-valence iron oxide powder. The iron oxide powder may contain divalent, trivalent, or mixed-valence iron hydroxide. The particle size, particle size distribution, and circularity of the iron oxide powder may be the same as those of the iron powder.

[0021] 1-3. Binder The binder is used to efficiently disperse the porous carbide, iron powder, and iron oxide powder and to integrate iron and iron compounds with the porous carbide during the manufacturing process of the remover (described later). 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 mold 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.

[0022] 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 porous carbide, they may also be compounds of alkali metals or alkaline earth metals contained in the biomass.

[0023] 1-5.Composition ratio The composition ratios of the above-described components can be adjusted as appropriate. For example, the porous carbide content in the remover may be adjusted within a range of 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 and / or iron oxide powder content may be adjusted within a range of 5% by mass to 35% by mass, 5% by mass to 25% by mass, or 5% by mass to 20% by mass. The binder content may be adjusted 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. The sum of the alkali metal and alkaline earth metal compound contents may be adjusted within a range of 1% by mass to 30% by mass, 1% by mass to 15% by mass, or 1% by mass to 10% by mass.

[0024] Alternatively, the carbon content of the removal material may be adjusted within a 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) of the removal material may be adjusted within a range of 5% by mass to 35% by mass. Furthermore, the sum of the alkali metal and alkaline earth metal contents may be adjusted within a range of 1% by mass to 30% by mass.

[0025] To measure the porous carbide content in a removal material, the carbon content of the raw porous carbide is first measured. For example, a combustion and infrared absorption method based on JIS H1617, JIS Z2615, and ASTM E1941 can be used. Specifically, the raw porous carbide is burned in a combustion furnace under an oxygen stream to produce carbon dioxide. The resulting carbon dioxide is then introduced into an infrared analyzer using oxygen gas, and its absorption is measured with a detector to determine the carbon dioxide concentration. From this carbon dioxide concentration, the mass of carbon in the raw porous carbide is quantified as the mass of the porous carbide. The porous carbide content can then be determined from the mass of the raw porous carbide and other raw materials mixed with it, such as the binder, iron powder, iron oxide powder, and water. The iron powder, iron oxide powder, and binder contents can also be calculated from the masses of the iron powder, iron oxide powder, binder, porous carbide, water, etc. used in the removal material manufacturing process.

[0026] 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 then separates and detects the ions 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.

[0027] On the other hand, the carbon content of the removed material can be determined by applying the above-mentioned combustion and infrared absorption method to the removed material. Note that the carbon content of the removed material is the content of carbon mainly derived from the porous carbide and binder. The iron content can also be measured by applying ICP-OES or ICP-MS to the removed material.

[0028] 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 below 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.

[0029] 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 carbide to produce 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.

[0030] 2-2. Mixing iron powder and / or iron oxide powder with binder Next, the porous carbide is mixed with iron powder and / or iron oxide powder, and a binder to produce a remover. The porous carbide may be crushed or classified in advance to adjust its particle size. Since the particle size of the porous carbide is often larger than the particle size of the iron powder or iron oxide powder, the porous carbide may be crushed to have a particle size approximately the same as that of the iron powder and / or iron oxide powder. The amounts of the porous carbide, binder, iron powder, and iron oxide powder are appropriately adjusted so as to obtain a composition ratio within the above-mentioned range.

[0031] Because the binder has a relatively high viscosity, the porous carbide, iron powder and / or iron oxide powder, and binder are mixed and then kneaded (mixed). Mixing machines such as a single-screw mixer, a twin-screw mixer, a mixing roll, a kneader, or a Banbury mixer may be used. For example, the porous carbide and iron powder are mixed in a mixer, and then the binder is mixed in the mixer. The binder may be added all at once, intermittently, or continuously. Adding the binder after mixing the porous carbide and iron powder and / or iron oxide powder and mixing the binder prevents aggregation of the porous carbide and iron powder and / or iron oxide powder, and suppresses foaming. The mixing temperature can be set at any temperature, 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 may be added as needed during mixing and kneading. Adding water prevents dust generation and allows the porous carbide and iron powder and / or iron oxide powder to be mixed more uniformly. Furthermore, an alkali metal and / or alkaline earth metal compound may be added during mixing and kneading.

[0033] Through the above operations, a paste-like mixture containing porous carbide, binder, and iron powder and / or iron oxide powder can be obtained as a remover. As mentioned above, the iron powder may be partially oxidized and contain iron compounds. In addition, in this process, some of the iron powder may be oxidized, resulting in the remover containing iron compounds even if iron oxide powder is not used. As mentioned above, examples of iron compounds include iron hydroxide and iron oxide.

[0034] 2-3. Granulation As an optional step, the removal material may be granulated and formed into a certain shape. The shaping of the removal material can be carried out using a granulator. Examples of granulators include a compression granulator, an extrusion granulator, a roll granulator, a blade granulator, a melt granulator, and a spray granulator.

[0035] When an extrusion-type granulator is used, a paste-like removal material formed into a predetermined shape is extruded from a die attached to the granulator. The extruded removal material is cut to a predetermined length and formed into pellets with the extrusion direction being the height direction. The length of the removal material (the height of the pellet shape) can be adjusted by adjusting the extrusion speed and cutting speed of the removal material in the extrusion-type granulator (the rotation speed of the cutter in the case of a rotary cutting method). In addition, the diameter of the removal material (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-type granulator, a removal material having a pellet shape with a controlled size (for example, an approximately cylindrical shape) can be obtained.

[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, 1 mm to 10 mm, or 3 mm to 8 mm.

[0037] The cross-sectional shape of the removed material after molding (cross-section perpendicular to the longitudinal direction) is not limited to a circle. The cross-sectional shape of the removed material may be, for example, an ellipse or a polygon. That is, the removed material after molding may be in the shape of a pellet, not only a cylinder but also an elliptical cylinder or a polygonal cylinder. The cross-sectional shape of the removed material can be changed by changing the opening shape of the die. This granulation process may be performed after the drying process described below.

[0038] 2-4. Drying (curing) Furthermore, as an optional step, the removal material may be subjected to a drying (curing) step. The drying temperature and time are also appropriately selected depending on the amount of removal material and the amount of water contained. 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] In the production of the remover according to one embodiment of the present invention, firing at a high temperature is not required. That is, heating at a temperature (e.g., 400°C or higher) required to carbonize the binder is not required. In other words, the maximum temperature in the production process of the remover may be less than 400°C. This eliminates the need for the time and energy required for firing, making it possible to provide the remover at a lower cost.

[0040] As described above, the manufacturing method of 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 contains iron powder, its ignition potential is significantly reduced, allowing the remover to be handled as a highly safe, non-hazardous material. Furthermore, as shown in the examples, the remover exhibits the function of removing nitrogen oxides and sulfur oxides without the need for the addition of 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.

[0041] 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 air pollutants even at room temperature. Therefore, there is no need to heat the removal material or the gas to be treated.

[0042] 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 de-dusted after contact with a removing material.

[0043] 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.

[0044] Furthermore, because the treated removal material contains porous carbonized material, spreading it on soil can retain the nutrients and water necessary for plant growth and provide space for microorganisms to grow. Therefore, after treating gases containing air pollutants, the removal material can also be used as a soil conditioner without causing any adverse effects caused by air pollutants.

[0045] 4. Carbon dioxide storage As mentioned above, the porous charcoal used as the raw material for the removal material can be obtained by carbonizing biomass. That is, porous charcoal is produced by effectively utilizing plant-derived biomass produced by the fixation of carbon dioxide through photosynthesis. Furthermore, by using a removal material obtained from this porous charcoal to remove air pollutants, a portion of the carbon dioxide contained in the gas can be fixed in the removal material. In addition, by spraying the removal material on soil, it contributes to soil improvement, and at the same time, the carbon dioxide fixed by the plants can be stored underground as a charcoal.

[0046] More specifically, as shown in FIG. 2, according to an embodiment of the present invention, biomass is carbonized to produce porous charcoal (1), and then a removal material is produced from the porous charcoal (2). This removal material contributes to improving air quality by removing air pollutants contained in the atmosphere and exhaust gases (3). It is then spread on soil as a soil conditioner and used to grow plants. Plants fix carbon dioxide from the atmosphere through photosynthesis, providing food and structural materials (4) and by-producing biomass. The cycle established by this series of processes (1) to (4) improves air quality and stores carbon dioxide from the atmosphere underground. Therefore, using a removal material according to one embodiment of the present invention can also contribute to reducing greenhouse gas emissions. [Example]

[0047] The following describes the production of a remover according to one embodiment of the present invention and the results of evaluating the remover.

[0048] 1. Manufacturing of removal material Irregularly shaped charcoal (waste charcoal from woody biomass gasification power generation) was used as the raw material porous carbide. To this charcoal, iron powder and iron oxide powder, each containing 45% by mass of iron particles with a particle size in the range of 300 μm to 2000 μm, 45% by mass of iron particles with a particle size in the range of 75 μm to 300 μm, and 10% by mass of iron particles with a particle size in the range of 1 μm to 75 μm, blast furnace slag ground powder as a binder, and water were added and kneaded at room temperature for 30 minutes to obtain a powder mixture. The obtained powder mixture was 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 the remover of Example 1.

[0049] The properties of the obtained removal material are summarized in Table 1. Regarding the elemental composition of the removal material, the carbon composition was determined using combustion and infrared absorption spectroscopy, and the composition of other metal elements was determined using ICP-MS. The amount of water was measured using the loss on drying method.

[0050] [Table 1]

[0051] 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, model GV-100S), and a detector tube (Gastec Corporation, nitrogen oxide detector tube, model 10). The carbon dioxide and nitrogen oxide removal capacities 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 the porous carbonized material used as the raw material for the removal material in Example 1, commercially available activated carbon (Granular Shirasagi, model number WH2x, manufactured by Osaka Gas Chemicals Co., Ltd.), and zeolite (natural hard zeolite 3-8 mm, manufactured by Hokkaido Zeolite Co., Ltd.).

[0052] The changes over time in the concentrations of carbon dioxide and nitrogen oxides in the recovered gas are shown in Figures 3 and 4, respectively. Regarding the carbon dioxide removal capacity, as shown in Figure 3, 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 2. On the other hand, in Comparative Examples 1 and 3, 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.

[0053] On the other hand, with regard to the nitrogen oxide removal capacity, in 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 4). Although the nitrogen oxide removal capacity gradually decreased thereafter, it stabilized about one day after the start of the introduction of the gas to be treated, confirming that approximately 60% 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 disappeared in a short period of time, ensuring that the recovered gas containing carbon dioxide can be used for plant growth and other purposes for a long period of time while removing air pollutants.

[0054] On the other hand, when zeolite, a type of porous material, was used as the removal material (Comparative Example 3), the concentration of nitrogen monoxide 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 concentration of nitrogen oxides 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 sample 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 removing nitrogen oxides in a removal material according to one embodiment of the present invention.

[0055] On the other hand, the plot for activated carbon (Comparative Example 2), 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.

[0056] 3. Examination of nitrogen oxide removal mechanism A removal material according to an embodiment of the present invention was manufactured in the same manner as in Example 1. However, in this case, the formed powder mixture was not dried. Using this removal material, an experiment similar to that conducted for Example 1 to evaluate the nitrogen oxide removal capacity was conducted (Example 2). For comparison, a similar experiment was conducted using activated carbon (Granular Shirasagi, model WH2x, manufactured by Osaka Gas Chemicals Co., Ltd.) (Comparative Example 4). The results are shown in Figure 5. Figure 5 shows the cumulative value of the mass of nitrogen in nitrogen oxides removed from the gas to be treated (cumulative nitrogen removal rate) relative to the mass of the removal material or activated carbon.

[0057] As can be seen from Figure 5, in both Example 2 and Comparative Example 4, the nitrogen oxide removal capacity can be maintained for approximately 80 days (including a 25-day interruption period). This result also suggests that Example 2 has a higher nitrogen oxide removal capacity than Comparative Example 4. From the results in Figure 5, it can be seen that the removal material of Example 2 removed approximately 0.3% by mass of nitrogen, relative to the mass of the removal material, from the treated gas at the end of the test. Similarly, it can be seen that the activated carbon of Comparative Example 4 removed approximately 0.25% by mass of nitrogen, relative to the mass of the activated carbon, from the treated gas at the end of the test.

[0058] Here, Figure 6 shows the nitrogen content in the removal material and activated carbon obtained from elemental analysis of the removal material of Example 2 and the activated carbon of Comparative Example 4 before and after the test. As mentioned above, the removal material of Example 2 removed approximately 0.3 mass% of nitrogen relative to the removal material from the start to the end of the test (Figure 5), but the increase in nitrogen content was small, remaining at 0.02 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 2 cannot be explained by nitrogen oxide adsorption, and that decomposition of nitrogen oxides contributes.

[0059] On the other hand, although the cumulative nitrogen removal rate (0.25%) in Comparative Example 4 was smaller than that in Example 2, the increase in nitrogen content was large, reaching approximately 0.15%. This suggests that the decomposition mechanism also contributes to the removal of nitrogen oxides by the activated carbon in Comparative Example 4, but the degree of this contribution is relatively small, and the contribution of adsorption is greater than in Example 2. 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.

[0060] 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.

[0061] 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. Porous carbide, Binder, and Contains iron powder, The content of the porous carbide is 20% by mass or more and 80% by mass or less, The content of the binder is 10% by mass or more and 50% by mass or less, The content of the iron powder is 5% by mass or more and 35% by mass or less, the iron powder comprises a plurality of iron particles; The iron powder has a particle size distribution in which 1) the proportion of the iron particles having a particle size in the range of 1 μm or more and less than 150 μm is 3% by mass or more and 70% by mass or less, 2) the proportion of the iron particles having a particle size in the range of 1 μm or more and less than 75 μm is 0% by mass or more and 25% by mass or less, 3) the proportion of the iron particles having a particle size in the range of 1 μm or more and less than 45 μm is 0% by mass or more and 15% by mass or less, 4) the proportion of the iron particles having a particle size in the range of 150 μm or more and less than 2000 μm is 30% by mass or more and 99% by mass or less, and 5) the proportion of the iron particles having a particle size in the range of 600 μm or more and less than 2000 μm is 0% by mass or more and 15% by mass or less, and simultaneously, the sum of the proportion of the iron particles in at least any one of 1) to 3) and the proportion of the iron particles in 4) or 5) is 100% by mass.

2. The remover according to claim 1 , wherein the iron powder has an average particle size of 20 μm or more and 500 μm or less.

3. The carbon content is 10% by mass or more and 80% by mass or less, The remover according to claim 1 , wherein the iron element content is 5% by mass or more and 35% by mass or less.

4. Carbonizing biomass to prepare a porous carbonized material; mixing the porous carbide with a binder and iron powder; the porous carbide, the binder, and the iron powder are mixed so that the content of the porous carbide is 20% by mass or more and 80% by mass or less, the content of the binder is 10% by mass or more and 50% by mass or less, and the content of the iron powder is 5% by mass or more and 35% by mass or less; the iron powder comprises a plurality of iron particles; 2) the proportion of the iron particles having a particle size of 1 μm or more and less than 75 μm is 0% by mass or more and 25% by mass or less; 3) the proportion of the iron particles having a particle size of 1 μm or more and less than 45 μm is 0% by mass or more and 15% by mass or less; 4) the proportion of the iron particles having a particle size of 150 μm or more and less than 2000 μm is 30% by mass or more and 99% by mass or less; and 5) the proportion of the iron particles having a particle size of 600 μm or more and less than 2000 μm is 0% by mass or more and 15% by mass or less; and simultaneously, the sum of the proportion of the iron particles of at least any one of 1) to 3) and the proportion of the iron particles of 4) or 5) is 100% by mass.

5. The method according to claim 4, wherein the iron powder has an average particle size of 20 μm or more and 500 μm or less.

6. 5. The manufacturing method according to claim 4, wherein the porous carbide, the binder, and the iron powder are mixed so that the carbon content is 10% by mass or more and 80% by mass or less, and the iron content is 5% by mass or more and 35% by mass or less.

7. The method includes contacting a gas containing air pollutants with a removal material, The removal material is Porous carbide, Binder, and Contains iron powder, The content of the porous carbide is 20% by mass or more and 80% by mass or less, The content of the binder is 10% by mass or more and 50% by mass or less, The content of the iron powder is 5% by mass or more and 35% by mass or less, the iron powder comprises a plurality of iron particles; 2) the proportion of the iron particles having a particle size of 1 μm or more and less than 75 μm is 0% by mass or more and 25% by mass or less; 3) the proportion of the iron particles having a particle size of 1 μm or more and less than 45 μm is 0% by mass or more and 15% by mass or less; 4) the proportion of the iron particles having a particle size of 150 μm or more and less than 2000 μm is 30% by mass or more and 99% by mass or less; and 5) the proportion of the iron particles having a particle size of 600 μm or more and less than 2000 μm is 0% by mass or more and 15% by mass or less; and simultaneously, the sum of the proportion of the iron particles of at least any one of 1) to 3) and the proportion of the iron particles of 4) or 5) is 100% by mass.

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