JP6940836B1 - Concrete admixtures, concrete admixture manufacturing methods and concrete products - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concrete admixture which has a small environmental load and exhibits excellent initial strength in mixed concrete. SOLUTION: At least, a biomass combustion ash containing biomass burned using a fluid medium-using boiler is contained, and the biomass combustion ash is a concrete admixture containing silicon dioxide. Further, the silicon dioxide was configured to contain at least soluble silica. Further, the biomass combustion ash is produced from a thermal power generation facility that burns biomass in a boiler using a fluid medium, and the boiler using a fluid medium is provided with a fluid layer using silica sand as a fluid medium and has a temperature higher than 1100 ° C. It is burned at a low temperature, and the silicon dioxide is derived from the silica sand as the fluid medium that is burned together with the biomass in the boiler using the fluid medium. [Selection diagram] Fig. 1

Description

The present invention relates to a concrete admixture used by mixing with concrete, a method for producing a concrete admixture, and a concrete product.

Conventionally, concrete has been widely used at construction sites and the like. Concrete is a substance that is initially liquid but gradually hardens to become solid, and since it is used in building structures, civil engineering structures, roadbeds, etc., strength performance is important. It is known that the index of concrete strength includes the initial strength that develops in a short time from the start of curing and the long-term strength that develops after a long period of time.

In addition, concrete admixtures may be added during the concrete manufacturing process. As such a concrete admixture, a concrete admixture using unburned carbon-containing coal ash generated in a coal-fired thermal power plant has been proposed (see Patent Document 1).

However, a concrete admixture using coal ash generated in a coal-fired thermal power plant as in Patent Document 1 has a problem that it has a large environmental load because the fuel for power generation is coal, and the environmental load in the production process is large. Small concrete admixtures have been desired.

On the other hand, biomass power generation using plant-derived fuel is known as a power generation method having a small environmental load. However, the use of combustion ash produced from thermal power plants as a concrete admixture was based on the Japanese Industrial Standards (currently Japanese Industrial Standards) for combustion ash produced from coal-cooked thermal power plants. Therefore, the combustion ash generated by biomass power generation has not been used as a concrete admixture.

JP-A-2018-172259

In view of the above problems, it is an object of the present invention to provide a concrete admixture, a method for producing a concrete admixture, and a concrete product, which have a small environmental load and exhibit excellent initial strength in mixed concrete.

The present invention is characterized in that at least a biomass combustion ash containing biomass burned using a fluid medium-using boiler is contained, and the biomass combustion ash is a concrete admixture containing silicon dioxide.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a concrete admixture, a method for producing a concrete admixture, and a concrete product, which have a small environmental load and exhibit excellent initial strength in mixed concrete.

Schematic diagram of a boiler using a circulating flow medium. A flow chart for producing a concrete admixture from biomass fuel. The measurement result figure which shows the measurement result of the palm shell combustion ash.

The applicant is diligently researching the effective use of combustion ash produced from thermal power plants. For example, we have also developed a heat reformer that heats and reforms coal ash to produce high-quality fly ash, and has obtained a patent right.
Here, conventionally, in thermal power generation, fossil fuels such as coal and petroleum have generally been used from the viewpoint of energy efficiency. However, fossil fuels generate a large amount of carbon dioxide when burned, and as global warming progresses, other fuels with a low environmental load have been considered. Among them, biomass power generation using plants as fuel has an environmental load based on the idea that carbon dioxide absorbed during the growth process of plants is more than carbon dioxide generated when burned when using fuel (carbon neutral). Is becoming more widespread as low thermal power generation.

However, since biomass power generation uses plants as fuel, a certain amount of combustion ash is generated. The generated combustion ash is treated as industrial waste and is generally landfilled, but there is a problem that it is necessary to secure a vast landfill.
The applicant has diligently studied the effective use of combustion ash generated by such biomass power generation. Then, he invented a concrete admixture using biomass combustion ash produced by thermal power generation using biomass fuel.
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

The concrete admixture of the present invention uses biomass combustion ash as a raw material. Biomass combustion ash is produced by at least burning biomass fuel at a high temperature and ashing it, that is, containing the burned biomass and producing it as a by-product of thermal power generation (biomass-fired power generation) mainly using plants (biomass) as fuel. Will be done.

Various types of boilers can be used for thermal power generation using biomass as fuel, but the pre-thermal power generation facility that produces the biomass combustion ash used in the present invention uses a fluidized bed as a fluidized bed and uses silica sand as a fluidized bed. It is preferable to use a boiler having a layer (or fluidized bed), and it is more preferable that the boiler has a mechanism for forcibly circulating silica sand as a fluidized bed, among which the circulating fluidized bed (floor). It is preferable to use a boiler (boiler using a circulating fluidized medium).

FIG. 1 is a schematic configuration diagram showing a configuration of a circulating fluidized bed boiler 10 as a boiler using a fluidized medium used for biomass-fired power generation. As the boiler using a fluidized medium, a fluidized bed boiler or a fluidized bed boiler can be used.
The circulating flow layer boiler 10 includes a fuel supply port 11 for supplying fuel, a bed material 12, a furnace 13 for burning fuel and the bed material 12, an air inflow path 14 for inflowing air into the furnace 13, and a furnace. A cyclone that collects and separates the furnace outlet 15 provided on the upper side surface of the furnace 13 and the ash contained in the combustion gas generated by the combustion in the furnace 13 and a part of the bed material 12 that has flowed with the ash. A 16 and an exhaust passage 17 for exhausting combustion gas together with fine powder, and an ash return pipe 18 communicating with the bottom of the cyclone 16 and the lower side surface of the furnace 13 are provided.

In this embodiment, the fuel input from the fuel supply port 11 is biomass containing oil. As such biomass, for example, palm husk (PKS), sorghum, or wood chips, or a plurality of these can be used. In particular, the palm husk is a coconut seed husk called palm palm, which is a residue generated in the process of producing palm oil, and therefore contains a small amount of palm oil (oil) remaining without being extracted. Therefore, it has high combustion efficiency and is suitable as an agricultural biomass fuel for biomass power generation. Further, a plurality of biomass may be mixed to form a biomass fuel.

The bed material 12 flows up and down in the furnace 13 together with the biomass fuel by the air blown from the lower part of the furnace 13, and is heated together with the flowing biomass fuel. Further, the bed material 12 keeps the temperature in the furnace 13 constant so that the biomass fuel is uniformly burned by flowing in the furnace 13 in a heated state. That is, as the bed material 12, various particulate matter having high fluidity in the air and high heat retention performance can be used. As such a bed material 12, a thermal catalyst containing silica can be used, and it is preferable to use silica sand. By using silica sand as the bed material 12, the step of adjusting the content of silicon dioxide described later can be omitted. Further, in addition to silica sand, limestone for flue gas desulfurization may be used.

The inside of the furnace 13 is heated to a high temperature by the provided heating device. The temperature inside the furnace 13 at this time can be 600 to 1100 ° C, preferably 700 to 1000 ° C. As a result, a sufficient amount of heat can be secured, the amount of ash generated can be secured, and biomass combustion ash can be generated in an environment in which ash sintering is unlikely to occur. In particular, by not sintering the biomass combustion ash (or reducing the sintering), it is possible to maintain a state in which a chemical reaction is likely to occur, and it is possible to easily cause a pozzolan reaction, which will be described later.

The air inflow path 14 is provided in the lower part of the furnace 13. Air is blown into the furnace 13 through the air inflow path 14. The bed material 12 and the biomass fuel flow up and down in the furnace 13 by the blown air, and the temperature in the furnace 13 is maintained as evenly as possible.

The furnace outlet 15 is provided on the upper side surface of the furnace 13. It is preferable that the height at which the reactor outlet 15 is provided is higher than the height at which the biomass fuel and the bed material 12 are flowing. The palm coconut shell and the bed material 12 are burned in the furnace 13 to become biomass combustion ash having a smaller particle size and a lighter weight than the fuel, and are transported to the cyclone 16 communicating from the furnace outlet 15 together with the combustion gas generated by the combustion.

The cyclone 16 precipitates relatively coarse-grained biomass-burning ash from the biomass-burning ash transported from the furnace 13 through the furnace outlet 15, and separates the coarse-grained biomass-burning ash from the fine-grained biomass-burning ash. The coarse-grained biomass combustion ash is supplied to the bottom of the furnace 13 again through the ash return pipe 18 communicating with the bottom of the cyclone 16. On the other hand, the fine biomass combustion ash is introduced into the exhaust passage 17 together with the combustion gas.

The combustion gas and biomass combustion ash introduced into the exhaust passage 17 are separated from the combustion gas and biomass combustion ash by using a bag filter or an electrostatic precipitator via a convection heat transfer section (not shown). The separated combustion gas is desulfurized to remove the sulfur oxides contained therein, and is released into the atmosphere as flue gas. As a method of desulfurization treatment, a method using lime is generally used. When the bed material 12 contains limestone, the desulfurization treatment is completed at the combustion stage, so that the desulfurization treatment of the combustion gas does not have to be performed.

The separated biomass combustion ash is collected as industrial waste and is generally landfilled at a designated landfill site.

FIG. 2 is a flowchart of a flow for producing a concrete admixture from biomass fuel.

As a fuel for thermal power generation, biomass is put into a circulating fluidized bed boiler 10 provided in a thermal power generation facility, and this biomass fuel is burned together with particles of a bed material 12 mainly composed of silica sand (step S1).

The circulating fluidized bed boiler 10 produces biomass combustion ash. Workers recover the produced biomass combustion ash from the thermal power generation facility (step S2). At this time, it is preferable to recover all the produced biomass combustion ash. The volume average particle size (MV) of the biomass combustion ash can be 250 μm or less, preferably 100 μm or less, and more preferably 40 μm or less. Further, it is preferable to adjust the size to 35 μm or less by using a classifier, and more preferably to 1 to 30 μm. The average particle size (MN) of the biomass combustion ash is preferably 20 μm or less, more preferably 15 μm or less using a classifier, and even more preferably 1 to 10 μm. Further, the area average particle size (MA) of the biomass combustion ash is preferably 40 μm or less, more preferably adjusted to 30 μm or less using a classifier, and further preferably 1 to 20 μm. The median diameter (50% cumulative particle size, D50) of the biomass combustion ash is preferably 40 μm or less, more preferably 30 μm or less using a classifier, and 1 to 20 μm. More preferred. Further, for each average particle size of the biomass combustion ash, in addition to satisfying the volume average particle size (MV) of 250 μm or less, the number average particle size (MN) is 20 μm or less, and the area average particle size (MA) is 40 μm or less. , And one or more of the conditions that the median diameter (50% cumulative particle size, D50) is 40 μm or less are preferably satisfied, and most preferably all of them are satisfied. These volume average particle size (MV), number average particle size (MN), area average particle size (MA), and median diameter (50% cumulative particle size, D50) are, for example, "particle size" manufactured by Microtrac. It can be measured with an appropriate particle size distribution measuring device such as "Distribution measuring device MT3300EXII". The median diameter (50% cumulative particle size, D50) referred to here means the particle size at the timing when the frequency of the volume becomes 50%. The term "particle size" is used in the same meaning as "particle size".
The biomass combustion ash thus obtained has a silicon dioxide content derived from the particles of silica sand used as the bed material 12 of 30% or more, more preferably 45% or more, and 50% or more. It can also be. The ignition loss of the obtained biomass combustion ash is 10% or less, preferably 5% or less. The specific surface area of the obtained biomass combustion ash is 2,500 to 5,000 cm2 / g. Further, the silicon dioxide contained in the obtained biomass combustion ash contains unsintered silicon dioxide contained in the biomass combustion ash with insufficient sintering due to insufficient heat applied during combustion. ..
More specifically, when palm coconut shells are used as the biomass fuel and silica sand is used for the bed material 12, the silicon dioxide content derived from the particles of the silica sand is 53.4%, and the loss on ignition is 4. 6. Biomass combustion ash with a specific surface area of 3,360 cm2 / g can be obtained.

Further, if necessary, the worker adds and mixes various additives that can be generally used as a concrete admixture to the biomass combustion ash (step S3). As such an additive, for example, fly ash (coal combustion ash) or the like can be used. If it is not necessary, the step of step S3 may be omitted.

In this way, a biomass combustion ash mixed powder containing biomass combustion ash as a main component is obtained by mixing an appropriate material with the burned biomass and biomass combustion ash containing silicon dioxide, and this can be used as a concrete admixture. can.
The produced concrete admixture is mixed with concrete in a form of replacing a part of the raw material of concrete. Of the concrete raw materials, which raw material to replace with can be appropriately selected, but it is preferable to replace with cement or fine aggregate (crushed sand, etc.), and from the viewpoint of particle size, replace with a part of fine aggregate. It is preferable to do so. For example, in concrete made from water, cement, fine aggregate (crushed sand, etc.), and coarse aggregate (crushed stone, gravel, etc.), cement and / or part of the fine aggregate (crushed sand, etc.) is part of the concrete admixture. It is preferable to replace with. Further, various concrete products such as ready-mixed concrete and recycled aggregate can be made from concrete mixed with the produced concrete admixture as a raw material.

With the above configuration, it is possible to provide a concrete admixture that has a small environmental load and exhibits excellent initial strength in mixed concrete.
The concrete admixture of the present invention uses biomass combustion ash, which is burned biomass, as a raw material. Biomass becomes a fuel for biomass power generation, which has a small environmental load among thermal power generation, and the biomass combustion ash used as a raw material for the concrete admixture of the present invention can use by-products generated in the power generation process of biomass power generation using biomass as fuel. With this configuration, waste reduction can be realized and an environment-friendly concrete admixture can be provided.

Further, the biomass combustion ash used as a raw material for the concrete admixture contains 30% by weight or more, preferably 45% by weight or more of silicon dioxide. With this configuration, excellent initial strength and long-term strength can be imparted to the mixed concrete. This is because calcium hydroxide contained in cement mixed with water reacts with unsintered unsintered silicon dioxide contained in concrete admixture (pozzolan reaction) to obtain initial strength and long-term strength. This is because it is possible.

Further, since silicon dioxide contained in the biomass fuel ash is soluble silica, it is possible to promote the pozzolan reaction in concrete and gradually harden the concrete.

Further, the biomass combustion ash used as a raw material of the concrete admixture may be adjusted by a classifier so that the particle size is 1 to 10 μm. By reducing the particle size, the specific surface area can be increased, the reactivity of the concrete admixture can be improved, and the hardening rate of the concrete to be mixed can be improved.

Further, the concrete admixture of the present invention uses biomass combustion ash produced by burning by a boiler having a fluidized bed using the fuel as biomass and the bed material 12 as silica sand as a raw material. With this configuration, the raw material biomass combustion ash contains soluble silica derived from silica sand and can be suitably used as a raw material for a concrete admixture. In addition, part or all of the silicon dioxide for component adjustment can be reduced, and the manufacturing process can be simplified and the cost can be reduced. Further, since the silica sand used as a bed material has a fine particle size due to wear due to flow during combustion, the reactivity of the obtained biomass combustion ash is enhanced, and a concrete admixture more suitable as a concrete additive can be obtained.

Further, the circulating fluidized bed boiler 10 of the present invention burns fuel biomass at 600 to 1100 ° C. With this configuration, the biomass combustion ash is not sintered, and a more reactive concrete admixture can be obtained. That is, the combustion ash produced from a facility such as a coal-fired thermal power plant that is fired at a high temperature has its surface hardened by sintering and its reactivity deteriorates, but it is burned at a low temperature as in the present invention. Since sintering of biomass combustion ash is suppressed, silicon dioxide in biomass combustion ash reacts with calcium hydroxide in cement earlier, and concrete exhibits high early strength.

The volume average particle size (MV) of the biomass combustion ash is 250 μm or less, preferably 100 μm or less, and more preferably 40 μm or less. With this configuration, the reactivity of the pozzolan reaction can be improved. That is, it can be more preferably used as a concrete admixture.

The average particle size (MN) of the biomass combustion ash is preferably 20 μm or less, more preferably 15 μm or less, and further preferably 1 to 10 μm. With this configuration, the reactivity of the pozzolan reaction can be improved. That is, it can be more preferably used as a concrete admixture.

The area average particle size (MA) of the biomass combustion ash is preferably 40 μm or less, more preferably 30 μm or less, and further preferably 1 to 20 μm. With this configuration, the reactivity of the pozzolan reaction can be improved. That is, it can be more preferably used as a concrete admixture.

The cumulative average diameter (median diameter, D50) of the biomass combustion ash is preferably 40 μm or less, more preferably 30 μm or less, and further preferably 1 to 20 μm. With this configuration, the reactivity of the pozzolan reaction can be improved. That is, it can be more preferably used as a concrete admixture.
<Example>

The produced palm husk combustion ash (biomass combustion ash) was obtained in a circulating fluidized bed boiler in which the temperature inside the furnace was adjusted to 600 to 1000 ° C. using palm husks which are biomass as fuel and silica sand as bed material.

The volume average particle size (MV), number average particle size (MN), area average particle size (MA), and median diameter (50% cumulative particle size, D50) were measured for the obtained palm shell combustion ash. A "particle size distribution measuring device MT3300EXII" manufactured by Microtrac Co., Ltd. was used for measuring each particle size distribution. As the measurement conditions at this time, an optical table of MT3300 (LOW-WET) is used, the particle shape is assumed to be non-spherical, the solvent is water, the upper limit of measurement is 2000 μm, the lower limit of measurement is 0.021 μm, and the measurement time is set. The time was set to 10 seconds, the distribution display was set to volume, and the calculation mode was set to "MT3300II". Moreover, the average value of three measurements was taken as the measurement result.

FIG. 3 is a measurement result diagram showing the measurement results of the acquired palm husk combustion ash.
Measurement Results FIG. 100 shows a cumulative% particle size distribution graph 101 showing the vertical axis as frequency (%) and the horizontal axis as particle size (μm), volume average particle size (μm) (MV), and number average particle size. Measurement of (μm) (MN), area average particle size (μm) (MA), specific surface area (m2 / ml) (CS), and standard deviation (μm) (SD) indicating the distribution width of the particle size distribution. The summary data table 102, which is a value, the peak particle size 103 indicating whether the peaks in the particle size distribution graph 101 are single or plural, the channel data 104 in the frequency distribution graph, and the particle size at each cumulative% at 10% intervals are shown. A cumulative% diameter table 105 and a measurement condition table 106 showing the measurement conditions are included.

As shown in FIG. 3, each particle size of the acquired palm shell combustion ash has a volume average particle size (MV) of 25.354 μm, a number average particle size (MN) of 4.6633 μm, and an area average particle size (MA). Was 13.436 μm, and the median diameter (50% cumulative particle size, D50) was 19.121 μm.

The obtained palm husk combustion ash was mixed in water, cement, crushed sand, and concrete made from crushed stone so as to replace a part of cement or crushed sand.
Specifically, as concrete materials before replacement (ordinary concrete materials), concrete materials of water 165 kg / m3, cement 450 kg / m3, crushed sand 780 kg / m3, crushed stone 1050 kg / m3, and admixture 2.250 kg / m3 are prepared. bottom. The admixture used for the concrete material before replacement is other than biomass combustion ash.
Then, 5% by weight of cement was replaced with Example 1, 10% by weight of cement was replaced with Example 2, and 5% by weight of crushed sand was replaced with palm husk combustion ash as Example 3, respectively. In addition, as a comparative example, concrete (ordinary concrete) in which none of the raw materials was replaced with palm husk combustion ash was produced.

Each of the produced Examples and Comparative Examples was cured for 24 hours, and the compressive strength was measured based on the concrete compressive strength test method specified in JIS A 1108.

Table 1 shows the results of compressive strength measurement after 24-hour curing in each Example and Comparative Example. As shown in Table 1, each of the examples in which a part of the raw material was replaced with palm husk combustion ash resulted in excellent compressive strength as compared with ordinary concrete. Specifically, by substituting a part of the raw material with palm husk combustion ash, the compressive strength was improved by 3% to 15%.
In addition, the long-term strength after 91 days was equal to or higher than that of ordinary concrete to which palm husk combustion ash was not added. In particular, when the crushed sand was replaced with palm husk combustion ash, favorable results were obtained in which the long-term strength was higher than that of ordinary concrete.

The present invention is not limited to the configuration of the above-described embodiment, and many embodiments can be obtained.
For example, in the biomass combustion ash in this example, the fine combustion ash contained in the flue gas of the power plant was recovered by a bag filter or an electrostatic collector, but it was classified with respect to the coarse-grained combustion ash settled by the cyclone. May be carried out to recover relatively fine combustion ash among the coarse-grained combustion ash.

Further, in the present embodiment, each manufacturing process of the concrete admixture has been described as being performed by an operator, but a part or all of each process may be performed by a machine.

Further, a part of the cement of the concrete material of 180 kg of water, 350 kg of cement, 850 kg of crushed sand and 1050 kg of crushed stone may be replaced with biomass combustion ash. In this case, for example, 10% of the cement can be replaced with an admixture to obtain 315 kg of cement and 35 kg of biomass combustion ash (or an admixture using biomass combustion ash). Even with such a configuration, the same effect as in the above-described embodiment can be obtained.

The present invention can be used in the industry of manufacturing and selling concrete admixtures used by mixing with concrete.

10 ... Circulating fluidized bed boiler 11 ... Fuel supply port 12 ... Bed material 13 ... Furnace 14 ... Air inflow path 15 ... Furnace outlet 16 ... Cyclone 17 ... Exhaust path 18 ... Ash return pipe

Claims (7)

A boiler provided with a fluidized bed using at least silica sand as a fluidized bed is used to burn the fluidized medium together with a biomass fuel composed of one or more palm husks, sorghum, and wood chips at 600 to 1100 ° C.
Biomass combustion ash containing silicon dioxide derived from the silica sand obtained by the combustion is obtained.
A method for producing a concrete admixture, which comprises the biomass combustion ash as a main component, contains the silicon dioxide, and obtains a concrete admixture having a volume average particle diameter of 250 μm or less. The method for producing a concrete admixture according to claim 1, wherein the concrete admixture contains unsintered silicon dioxide that has not been sintered as the silicon dioxide, and is mixed with the concrete material to cause a pozzolan reaction. The method for producing a concrete admixture according to claim 2, wherein the concrete admixture can be replaced with a part of cement in concrete. The main components are biomass fuel composed of one or more palm husks, sorghum, and wood chips, and biomass combustion ash obtained by burning a fluid medium containing at least silica sand.
A concrete admixture containing silicon dioxide and having a volume average particle size of 250 μm or less. The concrete admixture according to claim 4, which contains unsintered silicon dioxide as the silicon dioxide and is mixed with the concrete material to cause a pozzolan reaction. Manufactured by the manufacturing method according to claim 1, 2 or 3.
A concrete admixture containing the biomass combustion ash as a main component and containing 30% by weight or more of the silicon dioxide. A concrete product containing the concrete admixture according to claim 4, 5, or 6.

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