JP2017044350A - Process of manufacture of fly ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for increasing an amount of production of fly ash that is effectively utilized for applications for admixture or cement raw material for concrete and further foundation improvement and the like that will have an anxiety of lack in future.SOLUTION: This invention relates to a process of manufacture of fly ash in which raw materials of inorganic oxide (at least one kind selected from sand, volcanic ash, mineral, synthetic silica) are supplied to a furnace for a combustion boiler used for a coal steam power generation and the like where fuel is ignited.SELECTED DRAWING: None

Description

  The present invention relates to a novel method for producing fly ash generated in a combustion boiler. More specifically, in a combustion boiler that generates steam by burning fuel such as coal, it is characterized in that fly ash production is improved by supplying inorganic oxide-based raw materials together with fuel such as coal. This is a novel fly ash manufacturing method.

  In a coal-fired power plant, fuel such as coal is burned in a furnace of a combustion boiler, and the energy is converted into electricity. In addition to coal, some fuels such as biomass, tire chips, paper sludge, solid waste fuel, and heavy oil are also used in combination (for example, Patent Documents 1 to 3).

  As combustion boilers, pulverized coal-fired boilers using pulverized coal as fuel, circulating fluidized bed boilers that do not require pulverization of coal, and the like are known. The coal ash particles generated in the above combustion process float in the high-temperature combustion gas, and as the temperature drops at the boiler outlet, they become fine particles and are collected by the electric dust collector, or the bag filter This ash is called fly ash. Although it depends on the production area of the coal used, the constituents of fly ash are fine oxide particles mainly composed of silica and alumina. These particles are generally spherical, and their particle size ranges from sub-μm to 100 μm. Conventionally, it has been often used as landfill for waste disposal, but recently it has become difficult to secure a disposal site, so it is effectively used for various purposes. For example, it is effectively used in concrete admixtures, cement raw materials, and ground improvement agents. Various improvements have also been attempted in order to improve fly ash performance and expand applications. For example, a method for expanding the average particle size of fly ash (Patent Document 4), a method for reducing unburned carbon (Patent Document 5), a method for modifying fly ash added with a calcium source, and a fly ash cement (Patent Documents 6 to 6) 8).

JP 2012-093006 A JP 2006-007158 A JP 2014-202448 A JP 2009-074770 A Japanese Patent Laid-Open No. 06-126252 Japanese Patent Application Laid-Open No. 07-109153 JP 2008-094637 A JP 09-255380 A

  Conventionally, coal ash has been disposed of in landfills. However, in recent years, from the viewpoint of environmental conservation, it has come to be effectively used in the above-described applications. In particular, the utilization rate in applications such as concrete admixtures, cement raw materials, and ground improvement agents is increasing, and there is a concern that fly ash will be insufficient in the future.

  In view of the current situation as described above, the present inventors have intensively studied a method for increasing the production amount of fly ash which has become industrially useful. Although a combustion boiler is for generating the steam utilized for electric power generation, generally the temperature of the furnace of a boiler reaches 1400-1500 degreeC. The present invention is intended to effectively increase the amount of fly ash by effectively utilizing such a high-temperature furnace atmosphere. In other words, the present inventors have completed the present invention by conceiving that an increase in fly ash can be achieved by supplying an inorganic oxide raw material when fuel such as coal is fed into a furnace of a combustion boiler.

  That is, this invention provides the fly ash manufacturing method characterized by supplying an inorganic oxide type raw material to a furnace when fuel is burned in a furnace of a combustion boiler.

  In the invention of the above production method, the inorganic oxide-based material is preferably at least one solid inorganic oxide-based material selected from sand, volcanic ash, mineral, and synthetic silica, or a liquid organic silicon compound, and combustion It is also preferred that the boiler is a coal-fired power generation combustion boiler.

  Conventionally, fly ash has been positioned as a by-product or waste of a coal-fired power plant, but in the present invention, fly ash is considered a target product. That is, as described above, fly ash is a spherical particle having a particle size distribution in a wide range from sub-μm to 100 μm, and is an inorganic powder useful as various additives and raw materials. In order to produce such fly ash for the purpose, a high-temperature furnace such as a furnace of a thermal power plant is necessary. However, in the present invention, since an existing combustion boiler furnace can be used, energy efficiency and production efficiency are improved. It can be said that this is an extremely effective manufacturing method. In addition, since it is not necessary to install a new production facility, it is possible to suppress the generation of carbon dioxide, which is a useful method in terms of environmental conservation.

It is a flowchart which shows typically the aspect which implements this invention using a pulverized coal burning boiler power generator. It is a flowchart which shows typically the aspect which implements this invention using a circulating fluidized bed boiler electric power generating apparatus.

  The combustion boiler used in the present invention is a conventionally known device, and can be used without any limitation. For example, the combustion boiler includes a combustion boiler for coal-fired power generation, and specifically includes a known pulverized coal-fired boiler, a fluidized bed boiler, and the like.

  A typical pulverized coal-fired boiler among the pulverized coal-fired boilers is a furnace having a supply port for supplying fuel powder finely pulverized by a mill using coal as a main fuel; supplying high-temperature combustion gas from the furnace to heat And a convection heat transfer section that generates steam by exchange. The combustion exhaust gas discharged from the pulverized coal fired boiler power generator is released to the atmosphere via the dust collector and various abatement devices, but fly ash is recovered by the dust collector.

  As will be described later, various auxiliary fuels are used as fuel in addition to the main fuel, and the auxiliary fuel is supplied and burned from the supply port to the furnace together with the main fuel. Further, the furnace may be supplied to the furnace from a supply port different from the main fuel supply port.

  In addition, a typical fluidized bed boiler power generator among fluidized bed boilers is a furnace having a supply port for supplying coal as a main fuel and a fluidized bed at the bottom; a high-temperature combustion gas is supplied from the furnace and steam is exchanged by heat exchange. And a convection heat transfer section that generates Preferably, a circulating fluidized bed boiler power generator comprising a cyclone for collecting particles discharged accompanying combustion gas from a furnace and a solid particle circulation path for returning particles separated by the cyclone to the furnace Is preferred. Further, it is preferable that the solid particle circulation path is provided with an auxiliary fuel input port for supplying an after-mentioned auxiliary fuel, for example, a tire piece or an unground or partially pulverized biomass system and burning it in a furnace. The combustion exhaust gas discharged from the fluidized bed boiler power generation device is released to the atmosphere via a dust collector and various abatement devices, and fly ash is recovered by the dust collector.

  An electric dust collector, a bag filter, or the like is used as a dust collector for the combustion boiler.

  The auxiliary fuel is supplied to the furnace from the supply port and burned together with the main fuel. Further, it is supplied and burned to the furnace from the auxiliary fuel input port provided in the solid particle circulation path via the solid particle circulation path. Furthermore, it may be directly supplied to the furnace from a supply port different from the main fuel supply port.

  As fuel for the combustion boiler, main fuel coal and secondary fuel other than coal are used.

  The main fuel coal varies greatly depending on its production area (coal seam), but is not particularly limited. As the coal, high-grade coal such as anthracite and bituminous coal, and low-grade coal such as sub-bituminous coal, lignite and peat can be used. In the case of a pulverized coal-fired boiler, the coal is usually pulverized by a mill to form a pulverized coal having a particle size of about 75 μm and supplied to the furnace by pneumatic transportation. Moreover, in the case of a fluidized bed boiler, it is made into a lump having a particle size of 10 mm or less by a crusher or the like and supplied to a furnace.

  As auxiliary fuel other than coal, auxiliary fuels such as biomass, tire chips, paper sludge, solid waste fuel, and heavy oil can be used in combination. These auxiliary fuels are supplied to the furnace from the supply port together with coal as the main fuel, or are supplied to the furnace from a supply port different from the supply port of the main fuel.

  The inorganic oxide raw material is not particularly limited as long as it becomes an inorganic oxide by combustion, decomposition, melting and the like and recovered as fly ash in a high-temperature furnace. Moreover, the property is not particularly limited, and various inorganic oxide materials such as solids and liquids can be suitably used.

  When the inorganic oxide material is solid, it may not be sufficiently melted and spheroidized or evaporated in a furnace, and therefore it is preferably a powder. As the powder, for example, sand such as river sand, sea sand, land sand, mountain sand, volcanic ash, finely pulverized minerals, synthetic silica such as fumed silica and precipitated silica can be preferably used. In order to melt and spheroidize in the temperature range of the furnace, a raw material having a low melting point is preferably used, and a raw material mainly composed of silica is preferably used. In addition, if a powder with a large particle size is used, it may be impossible to melt and spheroidize in a furnace, so it is preferable to use a finely pulverized inorganic oxide-based material as much as possible, and the average particle size is 100 μm or less, preferably It is preferably 30 μm or less, more preferably 10 μm or less. Since the smaller the particle diameter is, the easier it is to form a melt spheroid, the lower limit of the particle diameter is not particularly limited. The average particle diameter is preferably larger than 0.1 μm for ease of handling, but even particles smaller than 0.1 μm are generally aggregated and can be used without any particular problems in the present invention. For example, fumed silica is an agglomeration of fine silica with a primary particle size of the order of 10 to 50 nm, so there is no need to finely pulverize, the powder has high fluidity, and the supply to the furnace can be achieved by pneumatic transportation. Easy to do.

  In addition to the powder as described above, liquid raw materials can also be used as the inorganic oxide raw material. It is preferable that it becomes silica or composite oxide particles of silica and other oxides after combustion. Specifically, liquid organosilicon compounds such as alkoxysilanes such as methyl silicate oligomers and silicone oils are suitable. Can be adopted. By including the organic group, the organic group is combusted when introduced into the furnace, which is also preferable in terms of not reducing the fuel efficiency of the furnace.

  In the present invention, when the fuel is burned in the furnace of the combustion boiler, the fly ash is manufactured by supplying the inorganic oxide material to the furnace.

  The inorganic oxide raw material may be supplied separately to the furnace by providing an inorganic oxide raw material supply port separately from the main fuel supply port. When the inorganic oxide raw material is solid, You may supply to a furnace with a main fuel from a supply port. When the main fuel is supplied from the main fuel supply port to the furnace together with the main fuel, it is preferably mixed and supplied with the main fuel.

  When an inorganic oxide raw material supply port is provided separately from the main fuel supply port and supplied separately to the furnace, the inorganic oxide raw material is used as a fuel in order to make the inorganic oxide raw material fly ash efficiently. It is preferable to supply from the height equal to or higher than the supply port, and more preferable to supply into the flame from the upper part of the furnace. The inorganic oxide material is preferably pneumatically transported because the inorganic oxide material is supplied dispersedly in the furnace.

  When the inorganic oxide raw material is liquid, it is preferably sprayed by spraying or the like and supplied directly to the furnace. In this case, since the liquid inorganic oxide-based material is supplied in the form of mist or gasification, in order to burn the inorganic oxide-based material, the inorganic oxide-based material is located near the combustion portion of the main fuel. In order to sufficiently burn, it is more preferable to supply the main fuel to the lower stage where the main fuel is supplied to the furnace. When the viscosity of the liquid is too high and spraying is difficult, a liquid diluted with a flammable organic solvent may be used.

  FIG. 1 shows an embodiment of the present invention using a typical pulverized coal fired boiler power generator.

  The solid inorganic oxide-based raw material is pulverized so as to have an average particle diameter of 100 μm or less as necessary, and then supplied to the furnace. In FIG. 1, the inorganic oxide material is supplied separately from the main fuel, but as described above, it may be mixed with the main fuel and supplied to the furnace from the main fuel supply port.

  The liquid inorganic oxide-based raw material is directly supplied to the furnace as it is or after being diluted with a combustible organic solvent and sprayed.

  FIG. 2 shows an embodiment of the present invention using a typical circulating fluidized bed boiler power generator.

  In the case of a circulating fluidized bed boiler power generator equipped with a solid particle circulation path, the method for supplying a solid inorganic oxide material to a furnace is to supply the inorganic oxide material separately or together with the main fuel as described above. In addition, a solid inorganic oxide-based raw material may be introduced into the solid particle circulation path and supplied to the furnace as in the case of tire chips and biomass-based fuels supplied as auxiliary fuel.

  Also in the circulating fluidized bed boiler power generator, the liquid inorganic oxide raw material is directly supplied to the furnace by spraying as it is or after diluting with a combustible organic solvent or the like.

  There is no problem with the supply amount of the inorganic oxide raw material as long as the target furnace temperature can be maintained. In the case of a solid inorganic oxide-based raw material, it can be supplied up to about 30% by weight with respect to coal as a main fuel, but is preferably 20% or less, more preferably 10% or less. This is because if the supply amount of the solid inorganic oxide-based raw material exceeds the above range, the temperature of the furnace is lowered and there is a concern that the amount of generated steam is below the required amount. Therefore, it is important to adjust the supply amount while controlling the temperature.

  In addition, when using a liquid organosilicon compound such as alkoxysilane or silicone oil as the inorganic oxide raw material, it is generally not necessary to worry about a decrease in furnace temperature because the organosilicon compound is flammable. If the amount of fly ash generated is too large, there is a concern that the discharge-side piping may be clogged and the load on the fly ash recovery device will increase. Therefore, it can be supplied up to about 100% by weight with respect to coal as the main fuel, but is preferably 50% or less, more preferably 30% or less.

  By introducing the inorganic oxide material into the furnace, the amount of fly ash generated is increased. As shown in FIGS. 1 and 2, the gas discharged from the furnace passes through the electric dust collector and the bag filter, so the fly ash recovery rate is almost 100%. Therefore, as a matter of course, the amount of fly ash generated increases by the solid content equivalent of the supplied inorganic oxide material.

  Since the yield of fly ash is generally around 10% by mass of coal supplied to the furnace, when the solid inorganic oxide material is used at 30% by weight with respect to the main fuel, the fly ash is produced by the method of the present invention. The yield of ash can be increased up to 4 times.

  In the case of a liquid inorganic oxide-based raw material, although depending on the composition of the raw material used, for example, when a methyl silicate oligomer (average tetramer) is used, the silica content is about 50% by mass. When the system raw material is used in a weight ratio of 100% with respect to the main fuel, the yield of fly ash can be increased to about 6 times by the method of the present invention.

  Usually, the composition of fly ash depends on the ash composition in the fuel such as coal used for the fuel. Table 1 shows typical chemical compositions of fly ash (Source: Japan Fly Ash Association website). Therefore, the final composition of fly ash obtained by the present invention reflects the ash composition in the fuel and the chemical composition of the supplied inorganic oxide raw material.

  When a solid inorganic oxide raw material containing a large amount of silica component is used, the fly ash obtained by the production method of the present invention can be rich in silica component. On the other hand, in the case of a solid inorganic oxide raw material containing a component having a high melting point and a low vapor pressure (for example, alumina, zirconia, etc.), there is a concern that it may not completely melt in the furnace, and the primary particles are spherical. Fly ash may not be obtained.

  That is, the method for producing fly ash according to the present invention is also a method for changing the composition of fly ash such that the composition of fly ash is, for example, a composition containing a large amount of silica components.

  Moreover, since the particles are formed in the gas phase in this system, substantially spherical particles can be obtained.

Claims (5)

  A fly ash manufacturing method comprising supplying an inorganic oxide material to a furnace when fuel is burned in a furnace of a combustion boiler.   2. The fly ash production method according to claim 1, wherein the inorganic oxide-based material is at least one solid inorganic oxide-based material selected from sand, volcanic ash, mineral, and synthetic silica.   3. The fly ash production method according to claim 2, wherein the solid inorganic oxide-based material contains silica.   2. The fly ash manufacturing method according to claim 1, wherein the inorganic oxide material is a liquid organosilicon compound.   2. The fly ash manufacturing method according to claim 1, wherein the combustion boiler is a coal-fired power generation combustion boiler.

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