Method for discharging solidified pellets and silo system

Abstract

To provide a method for discharging consolidated pellets, which can efficiently remove and discharge consolidated pellets produced in a silo, and a silo system, which can efficiently discharge consolidated pellets produced in a silo. [Solution] A method for discharging consolidated pellets 50, which are wood-based pellets that remain after being extinguished after ignition, from a silo 1 having consolidated pellets 50 inside, in which the consolidated pellets 50 are discharged from a discharge outlet 2D formed at the bottom of a housing 2 that forms the silo 1, and a softening medium that acts on the hydrogen bonds of the consolidated pellets 50 to soften the solidification is supplied from the outside to the inside of the housing 2 through a supply port 2E formed in the housing 2.

Description

[Technical Field]

[0001] The present invention relates to a method for discharging consolidated pellets produced in a silo, and a silo system capable of efficiently discharging consolidated pellets produced in a silo. [Background technology]

[0002] At businesses that require large amounts of wood pellets, such as biomass power plants, the wood pellets used in operations are stored in silos. However, due to the powdering of the wood pellets and pressure caused by their own weight, the wood pellets can adhere or accumulate on the inner walls of the silo, resulting in deposits. For this reason, Patent Document 1 discloses a deposit removal device that can mechanize the work of removing deposits such as grains that have adhered to or accumulated inside a silo.The method involves injecting grains, which are sprayed as granules, together with compressed gas, causing them to collide with the deposits on the inner wall of the silo, and removing the deposits such as grains that have adhered to or accumulated on the inner wall of the silo due to the impact of the sprayed granules colliding. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-253493 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, since wood pellets are mostly made of wood, they can catch fire inside the silo, and to extinguish the fire, water may be sprayed from the top of the silo or nitrogen gas may be injected from the bottom. In this way, the wood pellets that remain after the fire has been extinguished have been denatured by the effects of pressure, heat, moisture, etc., and compared to the wood pellets before ignition, they may become stronger solidified pellets (pellet masses) due to the strengthened bonding force caused by the compaction of the components that make up the wood pellets themselves and the strengthened bonding force caused by the adhesive components of the wood pellets. Furthermore, because such consolidated pellets are very hard and tough, it can be difficult to remove them from inside the silo using physical cutting equipment such as the deposit removal device described in Patent Document 1, silo cleaners used in silo cleaning, boring machines, and chippers.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a method for discharging consolidated pellets that can efficiently remove and discharge consolidated pellets produced in a silo, and a silo system that can efficiently discharge consolidated pellets produced in a silo. [Means for solving the problem]

[0006] To achieve the above-mentioned object, the method for dispensing consolidated pellets of the present invention is a method for dispensing consolidated pellets, which are wood-based pellets that remain after being extinguished after ignition, from a discharge outlet formed at the bottom of a housing that forms a silo having consolidated pellets inside.The method is characterized in that a softening medium is supplied from the outside to the inside of the housing through a supply port formed in the housing, which acts on the hydrogen bonds of the consolidated pellets to soften the solidification.

[0007] The characteristic configuration of the silo system of the present invention for achieving the above-mentioned object is that it comprises a silo having consolidated pellets, which are wood-based pellets that remain after being extinguished after ignition, inside a housing, and a supply mechanism that supplies a softening medium from the outside to the inside of the housing through a supply port formed in the housing, which acts on the hydrogen bonds of the consolidated pellets to soften the solidification.

[0008] As mentioned above, the wood pellets remaining after ignition and extinguishing are denatured by the effects of pressure, heat, moisture, etc., and may become stronger agglomerated pellets (pellet clumps) than the wood pellets before ignition due to the strengthened bonding forces caused by the compaction of the components that make up the wood pellets themselves and the strengthened bonding forces caused by the adhesive components of the wood pellets. Such agglomerated pellets are thought to be formed after combustion of wood pellets, whose main component is cellulose, and cooling under conditions of pressure due to the swelling of the cellulose and the weight of the wood pellets in the presence of moisture. During this process, it is thought that adjacent cellulose molecules form new hydrogen bonds with each other, resulting in stronger agglomerated pellets.

[0009] According to the above-mentioned characteristic configuration, a softening medium that acts on the hydrogen bonds of the consolidated pellets to soften them is supplied from the outside to the inside of the silo housing through a supply port formed in the housing. The softening medium acts on the hydrogen bonds formed between the cellulose in the consolidated pellets, thereby reducing the bonding strength of the consolidated pellets. This makes it possible to break the softened consolidated pellets into smaller pieces using some kind of physical action, such as cutting equipment, or to induce the consolidated pellets to collapse under their own weight, allowing the consolidated pellets to be efficiently discharged from a discharge port formed in the bottom of the housing.

[0010] Furthermore, in silos where wood pellets are stored, even if the fire is extinguished after the wood pellets have ignited, there is a risk of the pellets igniting again, so people cannot enter the silo to dispense the solidified pellets. However, according to the above-described characteristic configuration, the softening medium that softens the consolidated pellets is supplied from the outside to the inside of the housing through a supply port formed in the housing, thereby softening the consolidated pellets, so that the consolidated pellets can be dispensed without anyone having to enter the silo.

[0011] A further characteristic feature of the method for discharging consolidated pellets according to the present invention for achieving the above object is that the softening medium is an organic solvent having an SP value of 10.0 or more and 23.0 or less.

[0012] A further characteristic feature of the silo system according to the present invention for achieving the above object is that the softening medium is an organic solvent having an SP value of 10.0 or more and 23.0 or less.

[0013] According to the above-mentioned characteristic configuration, the organic solvent with an SP value of 10.0 to 23.0 is used as the softening medium, which allows the organic solvent to penetrate relatively easily into cellulose with an SP value of 15.6, and the organic solvent can easily penetrate into the hydrogen bonds formed between adjacent cellulose particles, making it easier for the organic solvent to exert its hydrogen bond-breaking effect, thereby efficiently reducing the bonding strength of the consolidated pellets.

[0014] A further characteristic feature of the method for discharging consolidated pellets according to the present invention for achieving the above object is that the softening medium is an aqueous solution in which an alkali metal hydroxide is dissolved.

[0015] A further characteristic feature of the silo system according to the present invention for achieving the above object is that the softening medium is an aqueous solution in which an alkali metal hydroxide is dissolved.

[0016] According to the above-mentioned characteristic configuration, since the softening medium is an aqueous solution containing an alkali metal hydroxide, the alkali ions dissolved in the aqueous solution act on the hydroxyl groups of the cellulose contained in the consolidated pellets, breaking the hydrogen bonds between adjacent cellulose, thereby efficiently reducing the bonding strength of the consolidated pellets. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic cross-sectional view of a silo system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view of a silo system according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] A method for discharging consolidated pellets and a silo system according to an embodiment of the present invention will be described with reference to the drawings.

[0019] <Embodiment> As shown in Figure 1, the silo system S of this embodiment comprises a silo 1 formed of a cylindrical housing 2 with a space 2a formed inside, a supply mechanism 10 that supplies a softening medium from the outside to the inside of the housing 2 through a supply port 2E formed in the housing 2, which acts on the hydrogen bonds of the consolidated pellets 50 to soften the solidification, and a control unit (not shown) that controls the various devices provided in the silo system S.

[0020] The silo 1 is formed by a cylindrical housing 2 having a space 2a formed therein. In this embodiment, the housing 2 has a cylindrical side wall 2A that is open at the top and bottom, a ceiling 2B that closes the upper opening of the side wall 2A, and a hopper 2C that is integrated with the side wall 2A at the bottom of the space 2a formed inside the housing 2 (side wall 2A). The bottom of the side wall 2A is fixed to the ground. The silo 1 is formed to a size of, for example, approximately 25 m in diameter, approximately 45 m in height, and approximately 10,000 tons in capacity.

[0021] Hopper 2C is formed in a conical shape in side cross section, with the diameter decreasing downward, and has a discharge outlet 2D formed in the center in plan view, with a lid (not shown) that can open and close discharge outlet 2D. As a result, space 2a formed inside housing 2 (side wall 2A), i.e., space 2a formed by side wall 2A, hopper 2C, and ceiling 2B, functions as a storage section in which wood pellets are stored.

[0022] In this embodiment, a nitrogen supply mechanism 20 capable of supplying nitrogen (gas) from the outside of side wall 2A to the interior where wood pellets are present is disposed on side wall 2A of housing 2. By supplying nitrogen to the wood pellets present inside side wall 2A, it is possible to prevent the wood pellets from accumulating heat due to self-oxidation and fermentation, and to suppress the generation and combustion of carbon monoxide in the event of ignition, thereby preventing the spread of fire.

[0023] The nitrogen supply mechanism 20 includes a nitrogen supply source 21, a nitrogen pipe 22 that connects the nitrogen supply source 21 with the interior of the side wall 2A, and a pump 23 that sends nitrogen from the nitrogen supply source 21 to the interior of the housing 2 through the nitrogen pipe 22, and the nitrogen pipe 22 is arranged to connect with the interior of the side wall 2A through a nitrogen pipe through-hole 2F formed in the side wall 2A. The pump 23 is arranged on the nitrogen pipe 22 upstream of the nitrogen supply source 21 (on the opposite side to the side wall 2A). A long first pipe member 24 (lance pipe) for spraying nitrogen is connected to the tip side of the nitrogen pipe 22 in a state of passing through the through-hole 2F, and the spray direction of the first pipe member 24 can be set in an appropriate direction. For example, the spray direction of the first pipe member 24 may be set in a horizontal direction, or in an appropriate direction inclined with respect to the inner surface of the side wall portion 2A.

[0024] It is also preferable to provide a plurality of through-holes 2F for the nitrogen pipes. In this case, a plurality of nitrogen pipes 22 and first pipe members 24 are also provided, and it is preferable to arrange the first pipe members 24 at the ends of the respective nitrogen pipes 22 so that they are located at dispersed positions within the housing 2.

[0025] A feeding mechanism (not shown) for feeding wood pellets into the housing 2 is disposed on the ceiling portion 2B, and a feeding opening (not shown) through which the wood pellets can be fed from the feeding mechanism is formed. Additionally, a fire extinguishing system (not shown) is disposed on the ceiling 2B to extinguish a fire when the wood pellets ignite. Specifically, the fire extinguishing system is configured to sprinkle or spray water (supplied via a pump or the like) onto the wood pellets stored inside the housing 2 from a pipe (not shown) formed on the ceiling 2B and communicating with the inside of the housing 2.

[0026] The wood pellets according to this embodiment are produced by compressing and drying crushed wood, and are formed into pellets (granules) that are cylindrical, for example, with a diameter of about 6 to 8 mm and a length of about 5 to 40 mm.

[0027] The composition of wood pellets before ignition and combustion includes, for example, 40 to 50 mass % cellulose, 20 to 35 mass % lignin, 20 to 25 mass % hemicellulose, and a few mass % of trace components.

[0028] Cellulose is a polymer of β-glucose, which contains many hydroxyl groups within the molecule and is held together in a sheet by hydrogen bonding. Here, hydrogen bonding refers to the electrostatic force generated by weakly electropositive hydrogen atoms on electronegative atoms, which bind to surrounding electronegative atoms. Lignin is a biopolymer (crosslinkable polymer) with a three-dimensional network structure, and plays a role as an adhesive component in the molding of wood pellets. Hemicellulose is an insoluble, amorphous polysaccharide contained in plant cells, and acts as an adhesive component that binds cellulose and lignin.

[0029] When such wood pellets are ignited in a silo, the remaining wood pellets after the fire is extinguished are denatured by the effects of pressure, heat, moisture, etc., and may become stronger consolidated pellets 50 (pellet mass) compared to the wood pellets before ignition due to the strengthened bonding force caused by the compaction of the components that make up the wood pellets themselves and the strengthened bonding force caused by the adhesive components of the wood pellets. Such consolidated pellets 50 are thought to be formed after the combustion of wood pellets, whose main component is cellulose, by cooling in the presence of moisture under pressure caused by the swelling of the cellulose and pressure due to the weight of the wood pellets. During the formation, it is thought that adjacent cellulose molecules form new hydrogen bonds between each other, resulting in stronger consolidated pellets 50.

[0030] The solidified pellets 50 thus produced are very strong pellet lumps, and are difficult to remove using physical excavation equipment such as silo cleaners, boring machines, and chippers used in silo cleaning. The space 2a formed inside the housing 2 (side wall portion 2A) also functions as a storage portion in which consolidated pellets 50, which are wood pellets that remain after being extinguished after ignition, are stored (present).

[0031] As described above, the supply mechanism 10 supplies a softening medium from the outside to the inside of the housing 2 through the supply port 2E formed in the housing 2, which acts on the hydrogen bonds of the consolidated pellets 50 to soften the consolidation. Specifically, the supply mechanism 10 includes a softening medium source 11, a softening medium pipe 12 that connects the softening medium source 11 to the inside of the housing 2 via a supply port 2E in the housing 2 (side wall portion 2A), and a pump 13 that sends the softening medium from the softening medium source 11 to the inside of the housing 2 (side wall portion 2A) via the softening medium pipe 12. The pump 13 is disposed on the softening medium pipe 12 upstream of the softening medium source 11 (on the opposite side to the side wall portion 2A).

[0032] In this embodiment, the supply mechanism 10 also uses the nitrogen piping 22 of the nitrogen supply mechanism 20. Specifically, one end of the softening medium piping 12 is connected to the nitrogen piping 22 between the first pipe member 24 and the nitrogen supply source 21, and by operating the pump 13 while nitrogen is being supplied from the nitrogen supply source 21 to the first pipe member 24, the softening medium from the softening medium source 11 can be supplied between the first pipe member 24 and the nitrogen supply source 21. This allows the softening medium to be supplied into the housing 2 by utilizing the nitrogen insertion pressure from the nitrogen supply mechanism 20. In this case, the nitrogen piping 22 also functions as the softening medium piping 12, and the through-hole 2F functions as the supply port 2E.

[0033] The softening medium (which acts on the hydrogen bonds of the consolidated pellets 50 to soften the consolidated pellets) supplied by the supply mechanism 10 to the space 2a inside the housing 2 is an aqueous solution in which an alkali metal hydroxide is dissolved or an organic solvent with an SP value of 10.0 to 23.0. The SP value is an abbreviation for Solubility Parameter, and is also called the solubility parameter. As will be described in detail later, the softening medium acts on the hydrogen bonds formed between the cellulose in the consolidated pellets 50, thereby reducing the bonding strength of the consolidated pellets 50. This makes it possible to break down the softened consolidated pellets 50 into smaller pieces using some kind of physical action, such as by cutting with equipment, or to induce the consolidated pellets 50 to collapse under the influence of their own weight, thereby enabling the consolidated pellets 50 to be efficiently discharged from the discharge port 2D formed in the bottom of the housing 2.

[0034] The hydroxide in the aqueous solution (alkaline aqueous solution) in which an alkali metal hydroxide is dissolved and used as the softening medium is preferably either sodium hydroxide or potassium hydroxide, and more preferably sodium hydroxide. When the softening medium is an aqueous solution containing an alkali metal hydroxide, the alkali ions dissolved in the aqueous solution act on the hydroxyl groups of the cellulose, lignin, and hemicellulose contained in the consolidated pellets 50, thereby breaking the hydrogen bonds. This allows the binding strength of the consolidated pellets to be reduced efficiently. Here, the hydroxide content in the alkaline aqueous solution is preferably 3% by mass or more, more preferably 4% by mass or more, and although there is no particular upper limit, it is preferably 6% by mass or less, more preferably less than 5% by mass. If the upper limit is less than 5% by mass, there is no need to designate the substance as a deleterious substance, making handling easier.

[0035] In addition, the organic solvent used as the softening medium has an SP value of 10.0 or more and 23.0 or less, and specific examples of such organic solvents include dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), and dimethylacetamide (DMAc). The SP value of DMSO is 14.5, the AN value is 19.3, and the DN value is 29.8; the SP value of NMP is 11.3, the AN value is 13.3, and the DN value is 27.3; the SP value of DMAc is 10.8, the AN value is 13.6, and the DN value is 27.8. The SP value of water is 23.4, the AN value is 54.8, and the DN value is 18.0. The AN value is the Acceptor Number, and the DN value is the Donor Number.

[0036] The smaller the difference between the SP value of cellulose and that of the softening medium, the greater the degree of swelling of the cellulose caused by the softening medium. The SP value of cellulose is 15.6, while the SP values ​​of DMSO (14.5), NMP (11.3), and DMAc (10.8) differ by 5.0 or less. Therefore, all organic solvents penetrate and swell the cellulose relatively easily, acting on the hydrogen bonds formed between adjacent cellulose molecules and easily breaking them. The higher the AN and DN values ​​of an organic solvent, the more likely it is that solvent clusters or multilayers will be formed, and the higher the adsorption rate to the target solid surface. Therefore, organic solvents with relatively high AN and DN values ​​(especially DMSO) are more likely to exhibit the effect of breaking hydrogen bonds. As a result, the bonding strength of the consolidated pellets 50 can be reduced efficiently.

[0037] An immersion test was conducted by immersing 50 solidified pellets (which cannot be broken by hand or with a drill, and can only be cut with a saw) in a solvent. In the immersion test, a mass of approximately 10 g of solidified pellets 50 was immersed (submerged) in approximately 50 g of solvent stored in a beaker, and while vibrating with a shaker (As One Corporation Microplate Mixer MPX-96A), the change over time (vibration was continued for approximately 3 hours after the start, and then the mixture was left to stand overnight) was observed to confirm the state of disintegration. As examples of the softening medium according to this embodiment, 4 mass% aqueous sodium hydroxide solution (1 mol / L aqueous sodium hydroxide solution), DMSO (100% DMSO solvent), NMP (100% NMP solvent), and DMAc (100% DMAc solvent) were used as solvents, and as comparative examples, 40 mass% aqueous formic acid solution, 3 mass% aqueous sodium bicarbonate solution, 10 mass% aqueous sodium bicarbonate solution, 27 mass% aqueous ZnCl2 solution, 15 mass% aqueous CaCl2 solution, glycerin (100% glycerin solvent), 50 mass% aqueous glycerin solution, and saturated aqueous citric acid solution were used.

[0038] When the softening medium according to the example was used, the solidified pellets 50 disintegrated in about 1.5 hours with a 4% by mass aqueous solution of sodium hydroxide, in about 10 minutes with DMSO (100% DMSO solvent), in about 35 minutes with NMP (100% NMP solvent), and in about 25 minutes with DMAc (100% DMAc solvent). On the other hand, when the solvents according to the comparative examples were used, the mass of consolidated pellets 50 remained hard even after being left standing overnight and did not crumble when poked. Therefore, as described above, by using the softening medium of the embodiment, the bonding force of the consolidated pellets 50 is reduced, making it possible to efficiently discharge the consolidated pellets 50 from the discharge outlet 2D formed at the bottom of the housing 2.

[0039] The method for discharging consolidated pellets 50 according to the embodiment is a method for discharging consolidated pellets 50 in a silo 1 having consolidated pellets 50 therein, which are wood-based pellets that remain after being extinguished after ignition, and in which the consolidated pellets 50 are discharged from a discharge outlet 2D formed at the bottom of a housing 2 that forms the silo 1, and a softening medium that acts on the hydrogen bonds of the consolidated pellets 50 to soften the solidification is supplied from the outside to the inside of the housing 2 via a supply port 2E formed in the housing 2. The method for discharging the consolidated pellets 50 can efficiently remove and discharge the consolidated pellets 50 produced in the silo 1 using the above-mentioned silo system S. On the other hand, the method for discharging the consolidated pellets 50 can efficiently remove and discharge the consolidated pellets 50 produced in the silo 1 even in a silo system S that is not configured to always include the supply mechanism 10 like the above-mentioned silo system S, but is configured to apply the supply mechanism 10 to the silo 1 and use it only when necessary.

[0040] [Another embodiment] (1) In the above embodiment, an example has been described in which one hopper 2C is provided in the lower part of the silo 1, but the number of hoppers 2C may be two or more.

[0041] (2) In the above embodiment, an example is described in which a supply mechanism 10 is used as a configuration for supplying the softening medium into the housing 2, but a configuration may also be provided in which a second supply mechanism 30 is provided in addition to the supply mechanism 10 or separately from the supply mechanism 10. 2, in a configuration including a second supply mechanism 30 in addition to the supply mechanism 10, the second supply mechanism 30 includes a second softening medium source 31, a second softening medium pipe 32 that connects the second softening medium source 31 to the inside of the housing 2 via a supply port 2E of the housing 2 (hopper 2C), and a second pump 33 that sends the softening medium from the second softening medium source 31 through the second softening medium pipe 32 to the inside of the housing 2. The second pump 33 is disposed on the second softening medium pipe 32 upstream of the second softening medium source 31 (on the opposite side to the hopper 2C). A long second pipe member 34 for spraying the softening medium is connected to the tip end of the second softening medium pipe 32 and passes through the through-hole 2F, and the spray direction of the second pipe member 34 can be set in any direction. For example, the spray direction of the second pipe member 34 may be set vertically, or may be set in a direction perpendicular to the inner surface of the hopper 2C, or may be set in any direction inclined relative to the inner surface. The second supply mechanism 30 may be configured to share the nitrogen piping 22 of the nitrogen supply mechanism 20, similar to the above-described supply mechanism 10. In this case, the softening medium can be supplied into the housing 2 by utilizing the nitrogen injection pressure from the nitrogen supply mechanism 20.

[0042] (3) In the above embodiment, the supply mechanism 10 and the second supply mechanism 30 supplied the softening medium through the supply port 2E formed in the side wall 2A or the hopper 2C of the housing 2 of the silo 1. However, the supply mechanism 10 and the second supply mechanism 30 may supply the softening medium into the housing 2 in other ways. For example, the supply port 2E may be formed in the ceiling 2B of the housing 2, and the softening medium (organic solvent, aqueous solution) may be supplied (by injection, spray, etc.) from above the space 2a inside the housing 2 through the supply port 2E.

[0043] (4) In the above embodiment, the supply mechanism 10 and the second supply mechanism 30 are described as being used in combination with all or part of the nitrogen supply mechanism 20. However, the supply mechanism 10 may be configured differently from the nitrogen supply mechanism 20, rather than being used in combination with all or part of the nitrogen supply mechanism 20.

[0044] (5) The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are merely examples, and the embodiments of the present invention are not limited thereto. They can be modified as appropriate within the scope of the purpose of the present invention. [Explanation of symbols]

[0045] 1. Silo 2. Case 2a space 2A Side wall part 2B Ceiling section 2C Hopper 2D outlet 2E Supply port 2F penetration opening 10 Supply mechanism 11 Softening media source 12 Softening medium piping 13 Pump 20 Nitrogen supply mechanism 21 Nitrogen Sources 22 Nitrogen piping 23 Pump 24 First pipe member 30 Second supply mechanism 31 Second softening medium source 32 2nd softening medium piping 33 Second Pump 34 Second pipe member 50 agglomerated pellets S Silo System

Claims

1. A method for discharging consolidated pellets, which are wood-based pellets that remain after ignition and are extinguished, from a discharge port formed in a lower part of a housing that forms a silo, the method comprising: A method for dispensing consolidated pellets, comprising supplying a softening medium from the outside of the housing to the inside through a supply port formed in the housing, the softening medium acting on the hydrogen bonds of the consolidated pellets to soften them.

2. 2. The method for discharging consolidated pellets according to claim 1, wherein the softening medium is an organic solvent having an SP value of 10.0 or more and 23.0 or less.

3. 2. The method for discharging consolidated pellets according to claim 1, wherein the softening medium is an aqueous solution in which an alkali metal hydroxide is dissolved.

4. a silo having, inside a housing, consolidated pellets that are wood-based pellets that remain after being extinguished after ignition; A silo system comprising: a supply mechanism that supplies a softening medium from the outside of the housing to the inside of the housing through a supply port formed in the housing, the softening medium acting on the hydrogen bonds of the consolidated pellets to soften the solidification.

5. The silo system according to claim 4, wherein the softening medium is an organic solvent having an SP value of 10.0 or more and 23.0 or less.

6. 5. The silo system according to claim 4, wherein the softening medium is an aqueous solution in which an alkali metal hydroxide is dissolved.

Images