Method of operating a gasifier and gasifier

Abstract

Provided are an operation method of a gasification furnace capable of stably operating the gasification furnace for a long period of time, a gasification furnace, a two-stage gasification device, a gasification method of an organic raw material, and a two-stage gasification method of an organic waste. The operation method of the gasification furnace includes: directly or indirectly feeding a compound containing an alkali metal to a gasification furnace in which an organic raw material is fed to generate a gas and a slag, and reducing the viscosity of the slag.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an operation method of a gasification furnace, the gasification furnace, a two-stage gasification device, a gasification method of an organic raw material, and a two-stage gasification method of an organic waste, which are applicable to gasification treatment of organic waste such as waste plastics. BACKGROUND

[0002] In a conventional gasification furnace used for gasification treatment of organic waste such as waste plastics, municipal waste, sewage sludge, waste FRP, biomass waste, automobile waste, waste oil, and the like, a non-combustible substance separation chamber is provided below a combustion chamber of the gasification furnace in order to separate a gas containing hydrogen, carbon monoxide gas, and the like from a slag containing ash. In order to suppress de novo synthesis of dioxin in the gasification furnace, a throat section having a smaller cross-sectional area than that of the combustion chamber is provided between the combustion chamber and the non-combustible substance separation chamber so as to make the residence time of the cooled gas shorter, that is, the linear velocity of the gas larger.

[0003] The slag generated in the combustion chamber is mostly flowed down along the side wall of the cylindrical combustion chamber in a molten state (hereinafter, the slag in the molten state is referred to as "molten slag"), and the remaining part is passed through the throat section to the non-combustible substance separation chamber in a state of being entrained in the gas. The molten slag is coarsely granulated by being rapidly cooled by the cooling water of the non-combustible substance separation chamber, and is discharged from the slag discharge port of the bottom of the gasification furnace as coarse-grained slag.

[0004] If the organic raw material supplied to the gasification furnace is changed in composition, supply amount, or the like, the temperature in the combustion chamber is sometimes changed, or the melting point or viscosity of the generated slag is changed. In this case, a large amount of molten slag is once flowed into the throat section from the opening portion of the bottom of the combustion chamber, and the throat section or the cylindrical downcomer connected to the throat section in a manner of extending downward from the throat section is temporarily clogged, or the throat section or the cylindrical downcomer is made in a narrow state. When the temperature in the combustion chamber is sharply increased, the slag fixed to the side wall of the combustion chamber becomes molten slag and is flowed down from the side wall, and a large amount of molten slag is once flowed into the throat section, so that clogging of the throat section or the cylindrical downcomer can be caused.

[0005] On the side wall of the connection portion of the throat section and the non-combustible substance separation chamber, fine slag droplets (slag mist) entrained in the gas are sometimes adhered, and a large slag block is formed. If the slag block falls into the non-combustible substance separation chamber, the slag discharge port of the non-combustible substance separation chamber is sometimes clogged.

[0006] If the throat, the cylindrical downcomer, or the slag discharge port is temporarily clogged, or the throat or the cylindrical downcomer becomes narrow, the internal pressure of the gasification furnace becomes high, and therefore, from the viewpoint of safety, it is sometimes necessary to stop the operation of the gasification furnace or to reduce the supply amount of the organic raw material. In the case where the slag discharge port is clogged by a slag block, it is necessary to stop the operation of the gasification furnace and clean the inside of the non-combustible substance separation chamber, and therefore, the operation efficiency is reduced.

[0007] Patent Document 1 describes an operation method of a waste gasification melting reforming furnace, which is a method of gasifying and melting waste in a gasification melting reforming furnace and performing gas reforming of generated gas in a reforming furnace at a temperature of 1000 to 1300°C, characterized in that, in the case where the basicity (CaO / SiO2) of ash is 1.0 or more, a powder agent rich in SiO2 is added to the waste in front of the gasification melting furnace or to the generated gas of the gasification melting furnace in front of the reforming furnace as a melting accelerator.

[0008] Prior Art Documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2009-226237 SUMMARY

[0010] Problems to be Solved by the Invention

[0011] Patent Document 1 focuses on the ratio of calcium to silicon (basicity of ash) and cannot be applied to organic waste and the like having a low calcium content, and the applicable composition of waste is limited.

[0012] By lowering the operation temperature (combustion temperature) of the gasification furnace, it is sometimes possible to increase useful components contained in the generated gas, such as hydrogen and carbon monoxide gas. However, if the operation temperature of the gasification furnace is lowered, the fluidity of the molten slag decreases, and the clogging or narrowing of the throat or the cylindrical downcomer is more likely to occur. The molten slag whose fluidity has decreased becomes larger droplets and is rapidly cooled by the cooling water of the non-combustible substance separation chamber, thereby becoming coarse-grained slag of a large diameter. The coarse-grained slag of a large diameter causes the slag discharge port to be easily clogged.

[0013] The present application provides a gasification furnace operation method capable of stably operating a gasification furnace for a long period of time, a gasification furnace, a two-stage gasification device, a gasification method of an organic raw material, and a two-stage gasification method of an organic waste.

[0014] Means for Solving the Problems

[0015] The present inventors conducted intensive studies, and as a result, found that by directly or indirectly feeding a compound containing an alkali metal into the gasification furnace, it is possible to lower the viscosity of the slag, inhibit or prevent the clogging or narrowing of the throat or the cylindrical downcomer or the clogging of the bottom of the gasification furnace, and thus completed the present application.

[0016] The present disclosure includes the following technical solutions.

[0017] [1] A method for operating a gasifier, comprising: in a gasifier in which an organic raw material is charged to generate a gas and a slag, directly or indirectly charging a compound containing an alkali metal to the gasifier to reduce the viscosity of the slag.

[0018] [2] The method according to [1], wherein the compound containing an alkali metal is sodium silicate.

[0019] [3] The method according to [2], wherein the sodium silicate is charged in the form of an aqueous solution.

[0020] [4] The method according to [2] or [3], wherein the molar ratio of silicon dioxide to sodium oxide (moles of silicon dioxide / moles of sodium oxide) in the sodium silicate is 0.4 or more and 4.5 or less.

[0021] [5] The method according to any one of [1] to [4], comprising: directly or indirectly charging a compound containing silicon to the gasifier.

[0022] [6] The method according to [5], wherein the compound containing silicon is a flow medium.

[0023] [7] The method according to [2] to [6], wherein the molar ratio of silicon dioxide to sodium oxide (moles of silicon dioxide / moles of sodium oxide) in the slag reduced in viscosity is 1.0 or more and 15.0 or less.

[0024] [8] The method according to any one of [1] to [7], wherein the slag reduced in viscosity contains 1.5 mass% to 20.0 mass% of an alkali metal, in terms of oxide.

[0025] [9] The method according to any one of [2] to [8], comprising:

[0026] analyzing the contents of sodium and silicon in the slag;

[0027] charging the compound containing an alkali metal when the molar ratio of silicon dioxide to sodium oxide (moles of silicon dioxide / moles of sodium oxide) in the slag is 2.5 or less.

[0028]

[10] The method according to any one of [1] to [9], comprising: mixing the compound containing an alkali metal with the organic raw material and charging the gasifier.

[0029]

[11] A gasifier is a gasifier that generates gas and slag from organic raw materials, comprising: a combustion chamber for gasifying or burning the organic raw materials; a non-combustible substance separation chamber for cooling and recovering the generated slag; and an inlet for an alkali metal compound disposed in the combustion chamber.

[0030]

[12] According to the gasifier described in

[11] , the inlet has a double tube with an outer tube and an inner tube, the alkali metal compound being supplied to the inner tube and the inert gas being supplied to the outer tube.

[0031]

[13] According to the gasifier described in

[11] or

[12] , the inlet is disposed on the side of the combustion chamber.

[0032]

[14] The gasifier described in any of

[11] to

[13] is a rotary melting furnace.

[0033]

[15] A two-stage gasification device is a two-stage gasification device for organic waste, comprising: a low-temperature gasifier for gasifying organic waste in a primary stage to generate organic raw materials; and a high-temperature gasifier for gasifying the organic raw materials generated in the low-temperature gasifier in a secondary stage to generate gas and slag, wherein the high-temperature gasifier is a gasifier described in any one of

[11] to

[14] .

[0034]

[16] According to the two-stage gasification device described in

[15] , the low-temperature gasifier is a fluidized bed gasifier.

[0035]

[17] A method is a two-stage gasification method for organic waste, comprising: gasifying organic waste in a low-temperature gasifier to generate organic raw materials; feeding the organic raw materials into a high-temperature gasifier; and gasifying the organic raw materials in the high-temperature gasifier to generate gas and slag. The method further comprises: directly or indirectly feeding alkali metal compounds into the high-temperature gasifier to reduce the viscosity of the slag.

[0036]

[18] According to the method described in

[17] , the high-temperature gasifier is any one of the gasifiers described in

[11] to

[14] .

[0037]

[19] According to the method described in

[17] or

[18] , the low-temperature gasifier is a fluidized bed gasifier.

[0038] The effects of the invention

[0039] According to the invention disclosed herein, by directly or indirectly introducing alkali metal compounds into the gasifier to reduce the viscosity of the slag, the blockage or narrowing of the throat or cylindrical downcomer or the bottom of the gasifier is suppressed or prevented, thereby enabling the gasifier to operate stably for a long period of time. Attached Figure Description

[0040] Figure 1 FIG. 1 is a schematic cross-sectional view of a gasifier according to an embodiment.

[0041] Figure 2 FIG. 2 is a structural view of a two-stage gasification apparatus for organic waste with a gasifier according to an embodiment. DETAILED DESCRIPTION

[0042] Hereinafter, embodiments of the present application will be described, but the present application is not limited to these embodiments, and various applications can be made within the scope of the gist and the practice thereof.

[0043] One embodiment relates to a method for operating a gasifier, including: directly or indirectly feeding a compound containing an alkali metal to a gasifier in which an organic raw material is fed to generate a gas and a slag, to reduce the viscosity of the slag.

[0044] The gasifier is not particularly limited as long as it is an apparatus for generating a gas and a slag from an organic raw material. As the gasifier, for example, a bottom ash melting furnace (electric, burner, auxiliary material melting, etc.) that melts the residue such as bottom ash after incineration of waste in an incinerator, and a gasification melting furnace (direct melting furnace that simultaneously performs gasification and melting of waste, fluidized bed type gasification melting furnace that performs melting after gasification of waste, kiln type gasification melting furnace, pusher type gasification melting furnace, etc.) can be cited. As the classification according to the heat source of the gasifier, for example, an electric melting furnace (alternating current arc melting furnace, alternating current resistance melting furnace, direct current resistance melting furnace, plasma melting furnace, induction melting furnace, etc.), a fuel combustion melting furnace (rotary surface melting furnace, reflection surface melting furnace, radiation surface melting furnace, rotary flow melting furnace, rotary kiln melting furnace, coke head type bottom ash melting furnace, etc.), and a direct combustion melting furnace (coke head type garbage melting furnace, thermal decomposition · rotary flow melting furnace, internal melting furnace, etc.) can be cited. The gasifier can also be a high-temperature gasification furnace of a gasification device (gasification modification device, etc.) that generates a valuable gas (hydrogen gas, carbon monoxide gas, etc.) from organic waste.

[0045] In one embodiment, the gasifier has a combustion chamber that gasifies or combusts the organic raw material, a non-combustible substance separation chamber that cools and recovers the generated slag, and a guide inlet of the compound containing an alkali metal provided to the combustion chamber. The gasifier is preferably a rotary melting furnace.

[0046] In one embodiment, the gasifier is a high-temperature gasifier in a two-stage gasification device that gasifies organic waste such as waste plastics, municipal waste, sewage sludge, waste FRP, biomass waste, automobile waste, waste oil, and the like as waste. In the high-temperature gasifier, synthesis gas (also referred to as fuel gas) such as hydrogen gas and carbon monoxide gas, and slag containing oxides of aluminum, silicon, calcium, iron, and the like as ash are generated from the organic raw material. The organic raw material can be fed into the high-temperature gasifier together with a substance other than the organic raw material such as hydrogen gas, carbon monoxide gas, tar, combustible carbonaceous particles (coke), and particles containing non-combustible substances (ash) in addition to the organic waste or hydrocarbon gas. The organic raw material can be in the form of combustible gas entraining the combustible carbonaceous particles and the particles containing non-combustible substances.

[0047] Hereinafter, as an example of the gasifier, the high-temperature gasifier of the two-stage gasification device for organic waste will be described in detail.

[0048] The two-stage gasification device has a low-temperature gasifier that generates an organic raw material by primary gasification of organic waste, and a high-temperature gasifier that generates gas and slag by secondary gasification of the organic raw material generated by the low-temperature gasifier.

[0049] Figure 1 A schematic cross-sectional view of the gasifier (high-temperature gasifier) of one embodiment is shown. The gasifier is a rotary melting furnace having a combustion chamber 1 generally having a cylindrical shape, a throat portion 11, and a non-combustible substance separation chamber 12. In the combustion chamber 1, an organic raw material inlet 3 and a gasification agent inlet 4 for supplying a gasification agent (typically a mixed gas of oxygen and water vapor) for combustion of the organic raw material are provided on a side wall 2, and a top gasification agent inlet 5 for supplying oxygen or water vapor that can sometimes be insufficient in the upper portion of the combustion chamber 1 is provided at the top of the combustion chamber 1. In the combustion chamber 1, a gasification agent supply passage 6 for supplying the gasification agent to the top gasification agent inlet 5 is provided. The gasification agent supply passage 6 is connected to a gasification agent supply source 7. The gasification agent supply source 7 is connected to a gasification agent supply pump 8. The gasification agent supply pump 8 is connected to a gasification agent tank 9. The gasification agent tank 9 is connected to a gasification agent supply pipe 10. The gasification agent supply pipe 10 is connected to the gasification agent supply passage 6. Figure 1 In the figure, two gasification agent inlets 4 are shown, but the number of gasification agent inlets 4 is not particularly limited.

[0050] The organic raw material inlet 3 and the gasification agent inlet 4 are provided on the side wall 2 so that the organic raw material supplied to the combustion chamber 1 descends while rotating around an axis extending in the vertical direction of the combustion chamber 1. The organic raw material supplied to the combustion chamber 1 forms an outer peripheral side rotational flow containing a large amount of combustible components in a particulate form and an inner peripheral side rotational flow containing a large amount of combustible components in a gaseous form. By supplying the gasification agent such as oxygen from the gasification agent inlet 4 of the side wall 2 to the outer peripheral side rotational flow containing a large amount of combustible components in a particulate form, gasification of the combustible components in a particulate form is promoted.

[0051] In the figure, two gasification agent inlets 4 are shown, but the number of gasification agent inlets 4 is not particularly limited. Figure 1In the present embodiment, the periphery of the side wall 2 of the combustion chamber 1 is covered with a steel sheet 6, and further, the outer side thereof is covered with a cooling jacket 7 through which a cooling medium is passed inside. The side wall 2 is formed of a refractory material (typically, castable refractory material), but sometimes the surface thereof is abraded due to the erosion action of molten slag or the like. In this case, the temperature of the side wall 2 is cooled by the cooling medium to around the melting point of the molten slag, and the molten slag is solidified, whereby the erosion (self-coating of the slag) of the side wall 2 can be suppressed. The cooling medium is not particularly limited, but typically, boiler water is used, and inside the cooling jacket 7, a part of the boiler water exists in the form of water vapor.

[0052] The bottom 8 of the combustion chamber 1 is also formed of a refractory material (typically, castable refractory material) like the side wall 2, and a throat 11 is provided at the boundary between the combustion chamber 1 of the gasifier and the non-combustible substance separation chamber 12. The throat 11 is formed of a refractory material (typically, castable refractory material) having a thickness of 10 to 80 mass% of Cr203-Al203. Figure 1 In the present embodiment, the opening portion 9 of the combustion chamber 1 is provided at the axial position of the combustion chamber 1, but the opening portion 9 can also be provided so as to be deviated from the axial position of the combustion chamber 1 (in such a manner that the center of the opening portion is located in the periphery of the axial position of the combustion chamber 1).

[0053] The upper portion of the side wall 2 of the gasifier, in which the thickness of the refractory material is easily reduced, is preferably lined with a 10 to 80 mass% Cr203-Al203-based castable. The lower portion of the side wall 2 of the gasifier and the bottom 8 of the combustion chamber 1 can be lined with a 10 to 30 mass% Cr203-Al203-based castable.

[0054] In the non-combustible substance separation chamber 12, the lower front end of a cylindrical downcomer 14 connected to the throat 11 in such a manner as to extend downward from the throat 11 extends in such a manner as to be submerged in the cooling water of a water tank portion 16. The gas and molten slag that pass through the throat 11 are blown into the cooling water of the water tank portion 16. A cylindrical upcomer 15 having an inner diameter larger than the outer diameter of the cylindrical downcomer 14 is provided concentrically around the cylindrical downcomer 14. The gas blown into the cooling water of the water tank portion 16 is recovered from a gas take-out port 17 provided in the side surface of the non-combustible substance separation chamber 12, through the space between the cylindrical downcomer 14 and the cylindrical upcomer 15.

[0055] The cooling water of the water tank portion 16 is supplied from a cooling water introduction pipe 13. The cooling water supplied from the cooling water introduction pipe 13 flows down from the inner wall surface of the cylindrical downcomer 14 and is accumulated in the water tank portion 16. The cooling water accumulated in the water tank portion 16 is discharged to the outside from a cooling water take-out port 19 provided in the side surface of the water tank portion 16. The molten slag blown into the cooling water of the water tank portion 16 is quenched by the cooling water of the water tank portion 16 and becomes slag particles (coarse slag particles), which are taken out from a slag discharge port 18 provided in the bottom of the water tank portion 16. The temperature of the cooling water is preferably 150 to 160°C. Thus, the high-temperature gas and molten slag are quenched to 200°C or lower.

[0056] In Figure 1 which the cylindrical downcomer 14 is tapered in the lower portion, the lower front end is shown as having a zigzag shape, but the shape of the cylindrical downcomer 14 is not particularly limited. The inner wall surface of the cylindrical downcomer 14 is preferably shaped so that the cooling water flows down while rotating. Thus, the high-temperature gas is effectively brought into contact with the cooling water on the inner side surface of the cylindrical downcomer 14, and the gas can be effectively cooled.

[0057] Figure 1 The non-combustible substance separation chamber 12 shown is exemplary, and the gas can also be cooled without using cooling water. For example, the heat of the gas can be recovered by a radiant boiler and used for power generation or the like.

[0058] The temperature in the combustion chamber 1 of the gasification furnace is preferably 1200°C or higher and 1600°C or lower, more preferably 1250°C or higher and 1550°C or lower, and further preferably 1350°C or higher and 1450°C or lower.

[0059] The pressure in the furnace of the gasification furnace is preferably 0.5 MPaG (gauge pressure) or higher and 9.0 MPaG or lower, and more preferably 0.8 MPaG or higher and 2.0 MPaG or lower. If the pressure in the furnace of the gasification furnace is 9.0 MPaG or lower, a proper combustion temperature can be ensured, and from the viewpoints of pressure resistance and heat resistance, the gasification treatment can be performed economically without excessively increasing equipment costs. If the pressure in the furnace of the gasification furnace is 0.5 MPaG or higher, the equipment can be downsized as compared with the case where the gasification treatment is performed at normal pressure.

[0060] The alkali metal-containing compound can be directly fed into the gasification furnace or indirectly fed into the gasification furnace by being mixed with the organic raw material fed into the gasification furnace. From the viewpoint that the alkali metal-containing compound can be effectively brought to the gasification furnace and energy related to the transport of the alkali metal-containing compound and the like can be effectively utilized, it is preferable that the alkali metal-containing compound be directly fed into the gasification furnace.

[0061] In Figure 1 which the alkali metal-containing compound feed port 10 is provided on the side surface of the combustion chamber 1 of the gasification furnace. The alkali metal-containing compound feed port 10 can be provided instead of or in addition to the top gasification agent feed port 5 on the upper portion of the combustion chamber 1 of the gasification furnace. The alkali metal-containing compound feed port 10 can also be plural. The alkali metal-containing compound can be directly fed into the gasification furnace from the alkali metal-containing compound feed port 10. By feeding the alkali metal-containing compound from the alkali metal-containing compound feed port provided on the side surface or the upper portion of the combustion chamber 1, the alkali metal-containing compound can be effectively mixed into the organic raw material or the molten slag in a high-temperature state.

[0062] The alkali metal-containing compound introduction port 10 can be provided with a double pipe having an outer pipe and an inner pipe. By supplying the alkali metal-containing compound to the inner pipe of the double pipe and supplying an inert gas to the outer pipe of the double pipe, the alkali metal-containing compound can be dispersed or, when the alkali metal-containing compound is in the form of an aqueous solution, atomized, so as to be more uniformly introduced into the gasifier.

[0063] The alkali metal-containing compound introduction port 10 can also be provided as a double pipe, the inner pipe of which is supplied with the alkali metal-containing compound and the outer pipe of which is supplied with the gasification agent or steam. Thus, the alkali metal-containing compound introduction port 10 and the gasification agent introduction port 4 or the overhead gasification agent introduction port 5 can be provided at the same position of the gasifier.

[0064] In the case where the alkali metal-containing compound is mixed with the organic raw material introduced into the gasifier, the alkali metal-containing compound introduction port can be provided, for example, on the upstream side of the organic raw material introduction port 3, from which the alkali metal-containing compound is added to the organic raw material for mixing.

[0065] As the alkali metal-containing compound, for example, an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, an alkali metal carbonate such as sodium carbonate, potassium carbonate, an alkali metal bicarbonate such as sodium bicarbonate, potassium bicarbonate, and an alkali metal silicate such as sodium silicate, potassium silicate can be given. From the viewpoint of cost, the alkali metal-containing compound is preferably a sodium-containing compound, from the viewpoint of stability during storage, sodium hydroxide and sodium silicate are more preferable, and from the viewpoint of less influence on the refractory material forming the side wall 2 of the combustion chamber 1, sodium silicate is more preferable.

[0066] The alkali metal-containing compound is preferably introduced in the form of an aqueous solution because it is easy to directly introduce into the gasifier or can be more uniformly mixed with the organic raw material. For example, sodium hydroxide can be prepared as an aqueous solution of 5 to 50 mass%. Sodium silicate can be introduced in the form of an aqueous solution, i.e., in the form of water glass.

[0067] With respect to the molar ratio of silicon dioxide to sodium oxide (the number of moles of silicon dioxide / the number of moles of sodium oxide) in the sodium silicate, when the sodium oxide is taken as 1, the silicon dioxide is preferably 0.4 or more and 4.5 or less, more preferably 1.2 or more and 3.5 or less, and further preferably 2.3 or more and 3.3 or less. If the molar ratio of silicon dioxide to sodium oxide in the sodium silicate is within the above range, the fluidity of the slag can be effectively improved. The mass of silicon dioxide and sodium oxide is measured according to the method prescribed in JIS K 1408:1966.

[0068] The mass of silicon dioxide in the sodium silicate is preferably 19.0 mass% or more and 40.0 mass% or less, more preferably 21.0 mass% or more and 35.0 mass% or less, and further preferably 23.0 mass% or more and 30.0 mass% or less.

[0069] The mass of sodium oxide in the sodium silicate is preferably 5.0 mass% or more and 30 mass% or less, more preferably 7.0 mass% or more and 25.0 mass% or less, further preferably 9.0 mass% or more and 15.0 mass% or less.

[0070] The specific gravity of the sodium silicate at 15°C is preferably 30 or more, more preferably 35 or more, further preferably 38 or more. The specific gravity of the sodium silicate is measured according to the Baume scale prescribed in JIS Z 8804:2012.

[0071] The amount of use of the alkali metal-containing compound is preferably 0.5 parts by mass or more and 20.0 parts by mass or less, more preferably 1.0 parts by mass or more and 15.0 parts by mass or less, further preferably 3.0 parts by mass or more and 12.0 parts by mass or less, based on 100 parts by mass of the molten slag before the alkali metal-containing compound is charged.

[0072] It is preferable to charge the alkali metal-containing compound in such a manner that the temperature of the throat is higher than the melting point of the slag. By doing so, solidification of the slag in the throat can be prevented, and maintenance work such as scraping of the solidified slag is not required or is reduced.

[0073] The amount of charge of the alkali metal-containing compound can also be controlled based on the pressure difference of the throat and the discharge amount of the coarse slag.

[0074] In addition, the silicon-containing compound (but other than the silicon-containing compound corresponding to the above-described alkali metal-containing compound, such as sodium silicate and the like) can be directly charged into the gasifier, or can be indirectly charged into the gasifier by being mixed with the organic raw material charged into the gasifier. As the silicon-containing compound, for example, silica sand, silicates other than alkali metal silicates, and siloxane compounds can be given. The silicon-containing compound can be a fluid medium. As described later, the two-stage gasification device of one embodiment has a low-temperature gasifier as a preceding step of the gasifier (high-temperature gasifier). In the case where the low-temperature gasifier is a fluidized bed gasifier, a fluid medium such as silica sand, olivine sand, alumina, or the like is sometimes used. The fluid medium used in the preceding step can also be charged into the gasifier by being moved from the preceding step together with the organic raw material.

[0075] The molar ratio of silicon dioxide to sodium oxide (the number of moles of silicon dioxide / the number of moles of sodium oxide) in the low-viscosity slag is preferably 1.0 or more and 15.0 or less, more preferably 2.0 or more and 10.0 or less, further preferably 2.5 or more and 8.0 or less.

[0076] In one embodiment, the slag is analyzed for sodium and silicon content, and the alkali metal-containing compound is added when the molar ratio of silica to sodium oxide in the slag (moles of silica / moles of sodium oxide) is 2.5 or less. Thus, the molar ratio of silica to sodium oxide in the low-viscosity slag can be maintained in the above-mentioned preferred range, thereby stably operating the gasifier for a long period of time. The slag can be extracted from the bottom of the gasifier. The composition of the slag can also be estimated from the composition of a representative sample of the organic waste or organic raw material and the actual operation results of the gasifier.

[0077] The low-viscosity slag preferably contains 1.5 mass% or more and 20.0 mass% or less of alkali metal, more preferably 3.0 mass% or more and 15.0 mass% or less, and further preferably 5.0 mass% or more and 10.0 mass% or less, in terms of oxides.

[0078] The iron content of the low-viscosity slag is preferably less than 6.0 mass%, more preferably less than 5.5 mass%, and further preferably less than 5.0 mass%, in terms of oxide (Fe2O3). By setting the iron content of the low-viscosity slag in the above-mentioned range, the coarse-grained slag can be effectively utilized as a resource, and even if it is treated as an industrial waste, the specific gravity of the coarse-grained slag can be made to be within a range suitable for treatment.

[0079] In one embodiment, the main components of the slag are alumina (Al2O3) and silica (SiO2). By adding alkali metal and, if necessary, silicon to the slag containing alumina and silica as the main components to change the composition ratio of the slag, the softening point, melting point, and fluid point of the slag can be more effectively lowered. Thus, the clogging or narrowing of the throat portion or the clogging of the bottom of the gasifier can be inhibited or prevented.

[0080] In one embodiment, the change in the fluid point due to the change in the composition of the molten slag exhibits a behavior similar to that of a three-component system of alumina / silica / sodium oxide. In this embodiment, the composition and the amount of the alkali metal-containing compound required for the low-viscosity of the slag can be determined using a triangular graph showing the relationship between the composition ratio of the three-component system of alumina / silica / sodium oxide and the fluid point.

[0081] In one embodiment, the composition and the components of the molten slag before the addition of the alkali metal-containing compound are as follows.

[0082] Al2O3: 10 mass% to 50 mass%

[0083] SiO2: 20 mass% to 60 mass%

[0084] Na2O: 0.1 mass% to 20 mass%

[0085] CaO: 1 to 20 mass %

[0086] TiO2: 1 to 15 mass %

[0087] Fe2O3: 1 to 10 mass %

[0088] balance (MgO, etc.)

[0089] In one embodiment, the alkali metal-containing compound is introduced at a point at which the Na2O concentration of the slag is less than 10 mass %, preferably less than 5.0 mass %, more preferably less than 3.0 mass %, further preferably less than 1.5 mass %, in the gasification process. The extraction of the slag can be performed from the bottom of the gasifier.

[0090] In one embodiment, the two-stage gasification method of organic waste includes generating an organic raw material by primary gasification of the organic waste in a low-temperature gasifier, and generating a gas and a slag by secondary gasification of the organic raw material in a high-temperature gasifier, and further includes directly or indirectly introducing an alkali metal-containing compound into the high-temperature gasifier to reduce the viscosity of the slag.

[0091] Figure 2 A structural diagram of a two-stage gasification apparatus of organic waste equipped with a gasifier according to one embodiment is shown. The two-stage gasification apparatus is equipped with a low-temperature gasifier 23 and a high-temperature gasifier 27. The high-temperature gasifier 27 is a gasifier that is the object of the present disclosure, as already explained. The type of the low-temperature gasifier is not particularly limited, and is preferably a stoker furnace or a fluidized bed gasifier, more preferably a fluidized bed gasifier, further preferably a pressurized type fluidized bed gasifier. In the present embodiment, the low-temperature gasifier 23 is shown as a fluidized bed gasifier having a fluidized layer 24. Figure 2 In the present embodiment, the low-temperature gasifier 23 is shown as a fluidized bed gasifier having a fluidized layer 24.

[0092] The organic waste is not particularly limited, and is preferably at least one selected from the group consisting of waste plastics, municipal waste, sewage sludge, biomass waste, waste fiber reinforced plastic (FRP), automobile waste, industrial waste, iron and steel slag, and solidified fuel. From the viewpoint of transportation efficiency, the organic waste is more preferably refuse derived fuel (hereinafter also referred to as "RDF") in which municipal waste is used as a solidified fuel, or refuse paper & plastic fuel (hereinafter also referred to as "RPF") in which waste plastics are used as a solidified fuel, and is further preferably RPF from the viewpoints of less deviation in composition, high calorific value, and low moisture content. The organic waste can also be combined.

[0093] As the auxiliary fuel of the organic waste, coal, petroleum-based fuel, and the like can also be used.

[0094] The organic waste can be roughly broken into a size of about 5 mm to 30 mm and compressed into pellets as needed, and supplied to the low-temperature gasifier 23. The liquid organic waste can be directly supplied to the low-temperature gasifier 23.

[0095] Inside the low-temperature gasifier 23, a fluidized layer 24 is formed by fluidized medium (e.g., sand such as silica sand, olivine sand, alumina, iron powder, limestone, dolomite, etc.) fluidized by fluidizing gas b supplied from the lower portion of the furnace. As the fluidizing gas b, oxygen, air, or water vapor or a mixture thereof is generally used. The oxygen or air supplied as the fluidizing gas b also functions as a gasification agent for the organic waste. The organic waste a supplied to the low-temperature gasifier 23 is rapidly partially combusted (incomplete combustion) by the oxygen or air supplied to the furnace, for example, to generate a part of the organic raw material (hydrocarbon gas, etc.) and hydrogen, carbon monoxide gas, tar, combustible carbonaceous particles, etc., in the fluidized bed 24 maintained at a temperature of 450 to 850°C (e.g., 600°C). The heat generated by the partial combustion is used as heat for maintaining the temperature in the low-temperature gasifier.

[0096] The amount of air or oxygen supplied to the low-temperature gasifier 23 is preferably 5% or more and 30% or less of the theoretical oxygen amount required for complete combustion of the organic waste, and more preferably 10% or more and 20% or less.

[0097] The temperature in the furnace of the low-temperature gasifier 23 is preferably 450°C or higher and 850°C or lower, and more preferably 600°C or higher and 800°C or lower. If the temperature in the furnace of the low-temperature gasifier 23 is 850°C or lower, the metals contained in the organic waste having a melting point higher than the temperature of the fluidized layer can be discharged from the bottom of the low-temperature gasifier as valuable metals in a non-oxidized state together with the fluidized medium. If the temperature in the furnace of the low-temperature gasifier 23 is 450°C or higher, the generation of tar and coke can be suppressed, and on the other hand, the gasification can be efficiently performed.

[0098] The pressure in the furnace of the low-temperature gasifier 23 is preferably 0.5 MPaG (gauge pressure) or higher and 9.0 MPaG or lower, and more preferably 1.0 MPaG or higher and 2.0 MPaG or lower. If the pressure in the furnace of the low-temperature gasifier 23 is 9.0 MPaG or lower, the gasification treatment can be economically performed without excessively increasing the equipment cost from the viewpoint of pressure resistance and heat resistance. If the pressure in the furnace of the low-temperature gasifier 23 is 0.5 MPaG or higher, the equipment can be downsized compared to the case where the gasification treatment is performed at normal pressure.

[0099] From the bottom of the low-temperature gasifier 23, the flow medium together with the non-combustibles is discharged via the lock hopper 25, and the coarse non-combustibles d are removed by the screen 26. The flow medium c from which the non-combustibles have been removed is returned to the inside of the low-temperature gasifier 23. The metals (e.g., iron, copper, aluminum, etc.) contained in the separated coarse non-combustibles d are almost in the unoxidized state because the fluidized bed 24 is at a relatively low temperature and in an oxygen-deficient state.

[0100] The combustible carbonaceous (solid carbon) generated by the partial combustion of the organic waste is finely pulverized by the stirring movement of the fluidized bed 24, becomes particles (coke) and is carried along with the organic material. A part of the non-combustible substance (ash) is also finely pulverized by the stirring movement of the fluidized bed 24, becomes particles and is carried along with the organic material.

[0101] The organic material e in a suspended state along with the particles containing the non-combustible substance and the combustible carbonaceous particles is supplied from the organic material inlet 3 of the high-temperature gasifier 27 to the combustion chamber 1 while rotating and descending. The organic material and the combustible carbonaceous particles are combusted by the gasification agent (mixed gas of oxygen and water vapor) f supplied from the gasification agent inlets 4 and 5. The temperature in the combustion chamber 1 is maintained at 1300 to 1500°C by the heat of combustion of the organic material and the combustible carbonaceous particles. By the combustion of the combustible carbonaceous particles, carbon monoxide gas and carbon dioxide gas are generated. By the aqueous gasification reaction of the water vapor contained in the gasification agent and the combustible carbonaceous particles, carbon monoxide gas and hydrogen gas are also generated.

[0102] The particles containing the non-combustible substance accompanying the organic material e become molten slag in the combustion chamber 1. The synthesis gas (hydrogen gas, carbon monoxide gas and carbon dioxide gas) and the molten slag are quenched in the non-combustible substance separation chamber 12, the synthesis gas is taken out from the gas take-out port 17, and the slag particles (coarse slag) are taken out from the slag discharge port 18.

[0103] In the case where the organic material e is accompanied by a large amount of solid matter (combustible carbonaceous particles or non-combustible substance), it is preferable to separate the gas and the solid matter in advance using a cyclone or the like before being supplied to the high-temperature gasifier 27, to introduce the gas from the organic material inlet 3 to the combustion chamber 1 of the high-temperature gasifier 27, and to introduce the solid matter together with the gasification agent f from the top gasification agent inlet 5 to the combustion chamber 1 of the high-temperature gasifier 27. By introducing the solid matter separated by the cyclone together with the gasification agent f into the combustion chamber 1 of the high-temperature gasifier 27, the combustible carbonaceous particles in the solid matter are preferentially brought into contact with the gasification agent, so that the amount of uncombusted carbon can be reduced.

[0104] The synthesis gas h taken out from the gas taking outlet 17 of the high-temperature gasification furnace 27 is washed by the scrubber 31 to remove a trace amount of residual slag (slag mist) that accompanies the synthesis gas h. The carbon monoxide gas and hydrogen gas contained in the synthesis gas h' washed by the scrubber 31 can be used as various chemical industry raw materials. The hydrogen gas obtained by the gasification treatment of the organic waste using the two-stage gasification device can also be used as a hydrogen source for ammonia synthesis. The slag recovered by the scrubber 31 is concentrated by sedimentation in the storage tank 32, and is discharged to the outside as fine-particle slag g f Since the fine-particle slag g f contains a large amount of combustible carbonaceous particles, it is preferably supplied again to the high-temperature gasification furnace.

[0105] On the other hand, the slag particles g taken out from the slag discharge outlet 18 of the high-temperature gasification furnace 27 are appropriately discharged to the storage tank 29 through the lock hopper 28. The coarse-particle slag recovered here is separated from water by the screen 30. The coarse-particle slag g c can be used as a material for cement and civil engineering construction.

[0106] The alkali metal-containing compound m can be directly fed to the high-temperature gasification furnace 27 from the alkali metal-containing compound introduction port 10 provided in the high-temperature gasification furnace 27. The alkali metal-containing compound m can also be introduced in the middle of the pipeline connecting the low-temperature gasification furnace 23 and the high-temperature gasification furnace 27 to be fed to the organic raw material.

[0107] The carbon monoxide gas and hydrogen gas contained in the synthesis gas taken out from the gas taking outlet 17 of the high-temperature gasification furnace can be utilized as various chemical industry raw materials. For example, the synthesis gas can be used as a starting material, hydrogen gas can be obtained by a CO shift reaction, and ammonia gas can be produced.

[0108] Example

[0109] In the following examples, a specific embodiment of the present disclosure is illustrated, but the present invention is not limited thereto. All the parts and percentages are by mass unless otherwise specified.

[0110] <Reagents Used>

[0111] The following reagents were used as the alkali metal-containing compound.

[0112] Sodium silicate (manufactured by Toyo Silica Chemical Co., Ltd., Si02: 23.7-26%, Na20: 10.3-11.3%)

[0113] Sodium hydroxide (manufactured by Sunjin Chemical Co., Ltd., special grade)

[0114] <Softening Point, Melting Point, and Flow Point of Slag>

[0115] As for the softening point, melting point, and fluid point of the slag, a sample obtained by pulverizing the slag into a powder using a pulverizer was subjected to ashing treatment at 800°C for 5 hours, and then, using a Leitz high-temperature heating microscope, the measurement was performed under a mixed gas atmosphere of hydrogen:carbon dioxide = 1:1 in volume ratio.

[0116] <Cr elution amount>

[0117] The Cr elution amount when the refractory castable was immersed in the impregnation liquid containing sodium silicate or sodium hydroxide was measured in the following order.

[0118] (1) Acid decomposition

[0119] 0.1 g of the impregnation liquid after impregnation of the refractory castable, 6 mL of phosphoric acid (manufactured by Sunjin Chemical Co., Ltd., special grade), 4 mL of hydrochloric acid (manufactured by Sunjin Chemical Co., Ltd., special grade), 2.5 mL of hydrofluoric acid (manufactured by Sunjin Chemical Co., Ltd., special grade 46% to 48%), and 2 mL of nitric acid (manufactured by Kanto Chemical Co., Inc., electronic industry nitric acid 1.42 EL) were put into a microwave decomposition vessel (manufactured by Actin Technology Co., Ltd., MWS3+).

[0120] (2) Microwave heating decomposition

[0121] As for the microwave heating decomposition of the solution added to the microwave decomposition vessel, the following series of operations of (i) to (iv) were repeated twice to obtain an acid decomposition liquid.

[0122] (i) Raising to 190°C in 5 minutes, maintaining at 190°C for 5 minutes

[0123] (ii) Raising to 210°C in 2 minutes, maintaining at 210°C for 5 minutes

[0124] (iii) Raising to 230°C in 2 minutes, maintaining at 230°C for 25 minutes

[0125] (iv) Reducing to 100°C in 1 minute

[0126] (3) ICP-AES analysis

[0127] The acid decomposition liquid obtained by the microwave heating decomposition was all transferred to a 250 mL volumetric flask, and made up to 250 mL with ultrapure water (manufactured by Merck Co., Ltd., Direct-Q UV), 10 mL was collected from the solution after making up, and further made up to 100 mL as an analysis sample. According to JIS K 0116:2014, the analysis sample was measured using ICP-AES (manufactured by Shimadzu Corporation, ICPS-8100), and the Cr elution amount was quantified.

[0128] 1. Reduction in softening point, melting point and fluid point of slag by addition of alkali metal-containing compound

[0129] The softening point, melting point and fluid point were measured using the slag collected from the bottom of the high-temperature gasifier of the two-stage gasification apparatus shown in Figure 2 Table 1 (slag from actual machine 1 to 3, without addition of alkali metal-containing compound), and the slag obtained by adding the alkali metal-containing compound described in Table 1 to the actual machine 1 or 3. The composition of the slag and the measurement results are shown in Table 1.

[0130]

[0131] In Examples 1 to 5, the softening point, melting point and fluid point were all lower than in Reference Examples 1 to 3.

[0132] 2. Refractory material quality test

[0133] The Cr concentration in the impregnation liquid was measured after impregnating the refractory castable (10 cm x 10 cm x 10 cm) fired at 110°C for 3 hours and at 1000°C for 3 hours in 300 g of the impregnation liquid. The results are shown in Table 2.

[0134] Table 2

[0135]

[0136] In the case of using sodium silicate as the impregnation liquid, no elution of the Cr component of the refractory castable was confirmed, but in the case of using an aqueous sodium hydroxide solution, elution of the Cr component was confirmed.

[0137] 3. Refractory material actual machine test

[0138] For the two-stage gasification apparatus shown in Figure 2 Table 1, the treatment amount of organic waste was set to 5 t / h, the gas temperature at the outlet of the combustion chamber of the high-temperature gasifier was set to 1450°C, the pressure in the furnace was set to 0.9 MPaG, and the two-stage gasification apparatus was operated, and sodium silicate was directly fed to the high-temperature gasifier from the side pipe (alkali metal-containing compound inlet) of the high-temperature gasifier at a supply amount of 100 L / h, and the two-stage gasification apparatus was operated for 6 months. After stopping, the high-temperature gasifier was opened, and no effect on the refractory material was observed.

[0139] For the two-stage gasification apparatus shown in Figure 2The two-stage gasification apparatus was operated with the treatment amount of organic waste set to 5 t / h, the gas temperature at the outlet of the combustion chamber of the high-temperature gasifier set to 1450°C, the pressure in the furnace set to 0.9 MPaG, and sodium hydroxide aqueous solution was directly fed to the high-temperature gasifier from the side pipe (alkali metal compound inlet) at a supply amount of 150 L / h, and the two-stage gasification apparatus was operated for 0.5 months. After the stoppage, the high-temperature gasifier was opened, and the thickness of the refractory material was reduced.

[0140] BRIEF DESCRIPTION OF DRAWINGS

[0141] 1 combustion chamber

[0142] 2 side wall

[0143] 3 organic material inlet

[0144] 4 gasification agent inlet

[0145] 5 top gasification agent inlet

[0146] 6 steel sheet

[0147] 7 cooling jacket

[0148] 8 bottom

[0149] 9 opening

[0150] 10 alkali metal compound inlet

[0151] 11 throat

[0152] 12 non-combustible substance separation chamber

[0153] 13 cooling water inlet pipe

[0154] 14 cylindrical downcomer

[0155] 15 cylindrical upcomer

[0156] 16 water tank portion

[0157] 17 gas outlet

[0158] 18 slag outlet

[0159] 19 cooling water outlet

[0160] 23 low-temperature gasifier

[0161] 24 fluidized bed

[0162] 25 lock hopper

[0163] 26 screen

[0164] 27 high-temperature gasifier

[0165] 28 lock hopper

[0166] 29 storage tank

[0167] 30 screen

[0168] 31 washer

[0169] 32 storage tank

Claims

1. A method for operating a gasifier, comprising: in a gasifier in which an organic feedstock is charged to produce a gas and a slag, directly or indirectly charging a compound containing an alkali metal to the gasifier to reduce the viscosity of the slag, the method for operating the gasifier further comprising: analyzing the contents of sodium and silicon in the slag; when the molar ratio of silica to sodium oxide, i.e., the number of moles of silica / the number of moles of sodium oxide, in the slag is 2.5 or less, charging the compound containing an alkali metal, the compound containing an alkali metal is sodium silicate, the molar ratio of silica to sodium oxide, i.e., the number of moles of silica / the number of moles of sodium oxide, in the slag that has been reduced in viscosity is 1.0 or more and 15.0 or less.

2. The method according to claim 1, the sodium silicate is charged in the form of an aqueous solution.

3. The method according to claim 1 or 2, the molar ratio of silica to sodium oxide, i.e., the number of moles of silica / the number of moles of sodium oxide, in the sodium silicate is 0.4 or more and 4.5 or less.

4. The method according to claim 1 or 2, comprising: directly or indirectly charging a compound containing silicon to the gasifier.

5. The method according to claim 4, the compound containing silicon is a fluid medium.

6. The method according to claim 1 or 2, the slag that has been reduced in viscosity contains 1.5 mass% to 20.0 mass% of an alkali metal, in terms of oxides.

7. The method according to claim 1 or 2, comprising: mixing the compound containing an alkali metal with the organic feedstock and charging the gasifier.

8. A two-stage gasification method for organic waste, comprising: primary gasifying an organic waste in a low-temperature gasifier to produce an organic feedstock; charging the organic feedstock to a high-temperature gasifier; and secondary gasifying the organic feedstock in the high-temperature gasifier to produce a gas and a slag, the two-stage gasification method for organic waste includes directly or indirectly charging a compound containing an alkali metal to the high-temperature gasifier to reduce the viscosity of the slag, the two-stage gasification method for organic waste further comprising: analyzing the contents of sodium and silicon in the slag; when the molar ratio of silica to sodium oxide, i.e., the number of moles of silica / the number of moles of sodium oxide, in the slag is 2.5 or less, charging the compound containing an alkali metal, the compound containing an alkali metal is sodium silicate, the molar ratio of silica to sodium oxide, i.e., the number of moles of silica / the number of moles of sodium oxide, in the slag that has been reduced in viscosity is 1.0 or more and 15.0 or less.

9. The two-stage gasification method for organic waste according to claim 8, the low-temperature gasifier is a fluidized-bed gasifier.

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