JPH11147747A - Concrete composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize coal and ash resulting from the operation of a coal-fired thermal power station, especially of a pressurized fluidized bed combustion electricity generation system. SOLUTION: This composition contains PFBC ash defined as below: the PFBC ash is acquired by collecting ash flying in the direction of the upper part of a boiler 2 along with combustion gas in operating a pressurized fluidized bed combustion electricity generation system which has steps comprising (A) feeding a mixture of coal and limestone into a pressurized boiler 2, (B) fluidizing the mixture and (C) burning it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a concrete composition, and more particularly to a concrete composition which makes effective use of ash from a thermal power plant which has been conventionally discarded because of no use. Things.

[0002]

2. Description of the Related Art In recent years, awareness of global environmental protection has increased.
There has been a growing movement to recycle substances that have been previously discarded without finding their use.

[0003] Coal ash discharged from a coal-fired power plant is one of such wastes. However, conventionally, for example, fly ash is used as an admixture material of a concrete composition in the form of several percent as fly ash.
It is used in a mixed state or used directly for landfill in landfills, and it is hard to say that it has been effectively reused.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to effectively utilize a large amount of coal ash produced as a result of operating a coal-fired power plant, particularly a pressurized fluidized bed combustion power generation system.

[0005]

SUMMARY OF THE INVENTION The present inventors have surprisingly found that coal ash discharged from a coal-fired power plant employing a pressurized fluidized bed combustion power generation system surprisingly produces cement, fine aggregate and coarse aggregate. The surprising fact that it can be a substitute material has been found, and the present invention has been completed. That is, the present invention provides a concrete composition containing PFBC ash as defined below. PFBC ash: When a pressurized fluidized bed combustion power generation system including a step of introducing a mixture of coal and limestone into a pressurized boiler, fluidizing the mixture, and burning the mixture is operated together with combustion gas. The ash scattered toward the top of the boiler is collected, and the resulting ash is defined as PFBC ash.

The present invention also provides the above concrete composition, wherein the PFBC ash is, in particular, the following ash. When a mixture of coal and limestone is introduced into a pressurized boiler, and the pressurized fluidized bed combustion power generation system having a step of fluidizing and burning the mixture is operated, the boiler is cooled together with combustion gas. Ash collected from the ash scattered toward the upper part so as to have an average particle size of 10 to 40 μm.

Further, the present invention provides a concrete composition comprising:
It provides the above concrete composition comprising FBC ash, cement, fine aggregate and coarse aggregate.

Further, the present invention provides a concrete composition comprising:
It is an object of the present invention to provide a concrete composition as described above, comprising PFBC ash, cement and fine aggregate.

Further, the present invention provides the above concrete composition further containing various admixtures (agents).

[0010] The present invention also provides the above concrete composition in which PFBC ash is blended in an amount of 60% by weight or less based on the concrete composition.

Further, the present invention provides the above concrete composition, wherein the PFBC ash has a Blaine specific surface area of 1000 cm ² / g or more.

Further, the present invention provides the above concrete composition, wherein the mixture of coal and limestone has a combustion temperature of 700 to 950 ° C.

Further, according to the present invention, the pressure in the boiler is 4-18.
kg / m ² .

Further, the present invention provides the above concrete composition, wherein the oxygen concentration in the boiler exhaust gas is 1.5 to 8.0%.

Further, the present invention relates to a compound represented by B
It is intended to provide the above concrete composition further containing M ash. BM ash: When a mixture of coal and limestone is introduced into a pressurized boiler, and the mixture is fluidized and fired, a pressurized fluidized bed combustion power generation system having a step of operating is used.
Ash that does not scatter with the combustion gas toward the top of the boiler and can be collected from the bottom of the boiler is defined as BM ash.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to PFBC ash (PFBC: Pressurized Fluidized Bed Combustion) discharged from a coal-fired power plant employing a pressurized fluidized bed combustion power generation system.
Abbreviation). The pressurized fluidized bed combustion power generation system is a power generation system including a step of introducing a mixture of coal and limestone into a pressurized boiler, forming the mixture into a fluidized bed, and burning the mixture. The heat generated by the combustion was recovered as steam by the heat transfer tube in the fluidized bed and the steam turbine generator was driven, while the exhaust gas from the boiler still having sufficiently high pressure and temperature was removed by the dust collecting device. After that, the gas turbine generator is driven. This method has been implemented or tested in Japan and other countries, and is already known.

The pressurized fluidized bed combustion power generation system will be further described with reference to FIG. FIG. 1 is a diagram for explaining a pressurized fluidized bed combustion power generation system. In the pressurized fluidized bed combustion power generation system, a fluidized bed boiler 2 and a dust collecting device (cyclone) 3 are provided in a pressure vessel 1. The inside of the pressure vessel 1 is in a pressurized state by the introduction of pressurized air. First, coal and limestone are introduced into the fluidized-bed boiler 2. The inside of the fluidized-bed boiler 2 is also pressurized, so that the oxygen density is increased. The combustion gases generated by the combustion of coal and limestone are:
The PFBC ash is raised in the fluidized bed boiler 2 and passes through the dust collecting device 3, where the PFBC ash is collected and discharged from the discharge port 4. Further, the combustion gas that has passed through the dust collecting device 3 advances to the outside of the pressure vessel 1 and passes through the high-performance dust removing device 5, where the PF
The BC ash is collected and discharged from the discharge port 6. The combustion gas from which the PFBC ash has been removed drives a gas turbine, is denitrated, and is discharged into the atmosphere. In the present invention, the PFBC ash thus obtained is used.

FIG. 2 is a diagram for explaining another embodiment of the pressurized fluidized bed combustion power generation system. The configuration and conditions of the pressure vessel 1 and the fluidized-bed boiler 2 are the same as those in the embodiment of FIG. In FIG. 2, the combustion gas generated by the combustion of coal and limestone rises in the fluidized-bed boiler 2 and passes through the dust collecting device 3, where the primary cyclone ash is collected. This primary cyclone ash can be used as PFBC ash as described above, and its average particle size is 10 to 40 μm (for example,
50% or more passing through a 5 μm filter). Subsequently, the combustion gas passing through the dust collecting device 3 is further separated into another dust collecting device 3.
0 where the secondary cyclone ash is collected (average particle size is 2-3 μm). Next, the combustion gas proceeds to the outside of the pressure vessel 1, drives the gas turbine, and is denitrified and then discharged into the atmosphere. In the embodiment of FIG. 2, the high-performance dust removing device 5 does not exist. In the present invention, the secondary cyclone ash can also be used as the PFBC ash. However, since the amount of trapping is small, the replacement of the concrete composition of the present invention with cement and fine aggregate is taken into consideration. Use is preferred.

FIG. 3 is a view for explaining still another mode of the pressurized fluidized bed combustion power generation system. The configuration and conditions of the pressure vessel 1 and the fluidized-bed boiler 2 are the same as those in the embodiment of FIG. In FIG. 3, the combustion gas generated by the combustion of coal and limestone rises in the fluidized-bed boiler 2 and the ash circulation device 3
1 (circulation cyclone). The ash collected in the circulation cyclone is returned to the fluidized bed boiler 2 again.
The ash that has passed through the circulation type cyclone together with the combustion gas passes through a high-performance dust removing device 5 where PFBC ash is collected and discharged from a discharge port 6. The combustion gas from which the PFBC ash has been removed drives a gas turbine, is denitrated, and is discharged into the atmosphere. PFBC obtained according to the embodiment of FIG.
The average particle size of the ash is, for example, 10 to 30 μm.

From the bottom of the fluidized-bed boiler 2, non-scattered ash (hereinafter referred to as BM ash) is discharged. PFB
The difference between C ash and BM ash is that the former is scattered with the combustion gas and rises to the outside of the fluidized bed boiler,
The latter is capable of being taken out from the bottom of the fluidized-bed boiler without being scattered with the combustion gas. It is considered that the reason why the BM ash can be taken out from the bottom of the fluidized bed boiler is that the BM ash is particles having a size of about 300 μm or more and has an average particle size of about 1 mm.

In the pressurized fluidized bed combustion power generation system, since the fluidized bed boiler 2 is pressurized as described above and the coal and limestone are fluidized, the pulverized coal is blown into the furnace together with the air and the atmospheric pressure is applied. It is characterized in that the combustion temperature can be reduced as compared with the conventional pulverized coal-fired power generation system in which combustion is performed below. Therefore, the properties of the discharged PFBC ash are also significantly different from the conventional ones, and the PFBC ash itself has hydraulic properties and can be a substitute material for cement and fine aggregate particularly when introduced into a concrete composition. It has a notable effect.

[0022] In order to obtain a suitable PFBC ash in the present invention, 4~18kg / m ² the pressure in the fluidized bed boiler 2, and it is preferably set to 5~15kg / m ^2. The combustion temperature in the fluidized-bed boiler 2 is 700 to 950C, preferably 830 to 880C. Further, the oxygen concentration of the combustion gas generated by the combustion of coal and limestone is 1.5 to 8.0.
%, Preferably 2.5 to 7.0%.

In the combustion of coal and limestone, the combustion ratio of both is not particularly limited in the present invention,
For example, the weight ratio is 50: 1 to 50: 7. The particle size of coal and limestone is, for example, 6 mm or less, preferably 5 mm or less.

The maximum size of the PFBC ash is 3
00 μm, preferably 250 μm, more preferably PF
The size range of the BC ash is preferably from 10 to 250 μm. The PFBC ash can be collected by a conventionally known cyclone or ceramic tube filter.

The PFBC ash obtained in this way is amorphous, and the ash has a very large specific surface area. For example, the Blaine specific surface area is 1000 cm ² / g or more (preferable Blaine specific surface area is 2000 to 10000 cm ² / g).

[0026] PFBC ash can be introduced into concrete compositions as an alternative to cement and fine aggregate. The concrete composition according to the present invention includes not only concrete generally including cement, fine aggregate and coarse aggregate, but also various products such as mortar, ready mixed concrete and concrete. PFB
The blending amount of C ash should be appropriately determined according to the use of the concrete product and the like, but is generally 60% by weight or less, preferably 30% by weight or less based on the concrete composition. PFBC ash can replace approximately 50% by weight of the cement in the concrete composition. Except for compounding PFBC ash, the concrete composition of the present invention can employ the same compounding ratio as a conventional concrete composition. Various cements can be used depending on the application, and examples thereof include ordinary cement, early-strength cement, and moderately-heated cement. In addition, other raw materials of the concrete composition, for example, fine aggregate, coarse aggregate, admixture material and the like can be appropriately selected and used. Further, the water-cement ratio is not particularly limited and can be appropriately selected.

In the concrete composition of the present invention, various admixtures (agents) can be used as required.

The above-mentioned BM ash can also be used in the concrete composition of the present invention. BM ash is available as part or all of fine aggregate. Since BM ash has also been conventionally discarded, its use in concrete compositions is environmentally advantageous. The mixing ratio of BM ash is
It is 0 to 80% by weight, preferably 1 to 60% by weight, based on the concrete composition. When BM ash is used, it is preferable to add water to the BM ash in advance to cause a hydration reaction.

[0029]

Although it has not been clarified at this time why PFBC ash can substitute for cement, the present inventors consider as follows. Further, PFBC ash has the following characteristics unlike cement. Since the PFBC ash is under pressure, most of the remaining CaO has been recarbonated in the form of CaCO ₃ during the firing process. For this reason, curing when contacting with water is performed slowly, resulting in little heat generation and excellent handling properties. PFBC ash has Ca component, Si component and Al component combined. Conventional Si and Al components such as fly ash have a poor affinity because they bind in solid phase to Ca components in cement, but PFBC ash is in a state where the Ca component, Si component and Al component are already calcined and bonded. For this reason, it is equivalent to alite, belite, aluminate phase, ferrite phase and gypsum, which are the main components of cement. Therefore, it has excellent affinity with cement and can be a substitute for cement. The PFBC ash is amorphous, and the specific surface area of the ash is greatly increased. Conventional pulverized coal-fired power generation, in which pulverized coal is blown into the furnace together with air and burned under atmospheric pressure,
Since the coal is burned at a high temperature of 1400 to 1500 ° C., the shape of the ash particles becomes spherical, but the particle shape of the PFBC ash of the present invention is irregular and has a very large specific surface area. The increase in specific surface area contributes to the development of concrete strength. The reason why the particle shape of the PFBC ash becomes irregular is considered to be that coal and limestone are fluidized and burned at a relatively low temperature in a state where the oxygen density is increased.

[0030]

The present invention will be further described below with reference to examples. The PFBC ash used in the examples of the present invention was obtained by the apparatus schematically shown in FIG. Specific conditions are shown below. Boiler used: Power Development Co., Ltd. Wakamatsu General Works Pressurized fluidized bed combustion power generation type boiler Electric output: 71,000 kW Boiler pressure: 6-10 kg / m ² Boiler combustion temperature: 830-860 ° C Coal and limestone Combustion ratio (weight ratio): 25: 1 Particle size of coal and limestone: coal 6 mm or less, limestone 5 mm
Below Combustion gas oxygen concentration: 2.5 to 6.7%

PFBC ash is a cyclone (dust collection device)
And collected with a ceramic tube filter (a high-performance dust removing device). The average size of the obtained PFBC ash was 20 to 30 μm. Also obtained P
Observation of the FBC ash with an electron microscope confirmed that its shape was irregular.

Further, various raw materials used for producing the concrete composition in the examples are shown below. Cement: ordinary Portland cement Coarse aggregate: crushed stone (1305, 2005) from Fukuoka Prefecture, surface dry specific gravity 2.70, maximum dimension 13 mm, No. 13 and 14 have a maximum size of 20 mm Fine aggregate: river sand from Fukuoka Prefecture, specific gravity of surface dryness 2.58 BM ash: average size 1 mm Admixture: high performance water reducing agent

(Examples 1 to 7) Concrete compositions were produced at the mixing ratios shown in Table 1 below, and the compressive strength was measured in accordance with JIS A1108. As curing conditions, steam curing (2 hours beforehand → 20 ° C / hour temperature rise → 65 ° C maximum temperature 2)
(Time keeping → natural cooling). In the table, W indicates the weight of water, C indicates the weight of cement, and P indicates the weight of PFBC ash. Table 2 shows the results.

[0034]

[Table 1]

[0035]

[Table 2]

(Examples 8 to 10) Concrete compositions were prepared at the compounding ratios shown in Table 3 below, and the compressive strength was measured in the same manner as in Examples 1 to 7. Table 4 shows the results.

[0037]

[Table 3]

[0038]

[Table 4]

(Examples 11 to 18) Concrete compositions were prepared at the mixing ratios shown in Table 5 below, and the compressive strength was measured in the same manner as in Examples 1 to 7. Table 6 shows the results. In addition, No.
12 to 17 were standard curing.

[0040]

[Table 5]

[0041]

[Table 6]

The results in the above table show that the concrete composition of the present invention has a practically sufficient compressive strength. Further, even if the BM ash is replaced with all or a part of the fine aggregate and the coarse aggregate (Nos. 8 to 10), there is no great difference in the strength of the obtained concrete, which indicates that it is practically sufficient. Furthermore, the concrete composition of the present invention has practically sufficient compressive strength even in the case of mortar (Nos. 11 and 12), and even if the amount of fine aggregate or coarse aggregate is reduced, the strength is not affected. You can see that it has no effect.

[0043]

According to the present invention, the PFB generated as a result of operating a coal-fired power plant, particularly a pressurized fluidized bed combustion power generation system
It has been found that C ash can be used as a substitute for cement in concrete compositions, and PFBC ash, which has been mostly discarded in the past, can be effectively used. The concrete composition obtained by the present invention includes various concretes such as concrete slabs, stair blocks, boundary blocks, interlocking blocks, L-shaped retaining walls, concrete masonry blocks, dish blocks, precast concrete, wave-dissipating blocks, and fish reef blocks. Can be used for products.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a pressurized fluidized bed combustion power generation system.

FIG. 2 is a diagram for explaining another mode of the pressurized fluidized bed combustion power generation system.

FIG. 3 is a diagram for explaining another embodiment of the pressurized fluidized bed combustion power generation system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure vessel 2 Fluidized bed boiler 3,30 Dust collecting device 4,6 Discharge port 5 High-performance dust removing device 31 Ash circulating device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Yoshida 1st Yanagizaki-cho, Wakamatsu-ku, Kitakyushu-city, Fukuoka Prefecture Inside the Wakamatsu General Works, Inc. 11th 3rd 107

Claims (11)

[Claims] 1. A concrete composition comprising PFBC ash as defined below. PFBC ash: When a pressurized fluidized bed combustion power generation system including a step of introducing a mixture of coal and limestone into a pressurized boiler, fluidizing the mixture, and burning the mixture is operated together with combustion gas. The ash scattered toward the top of the boiler is collected, and the resulting ash is defined as PFBC ash. 2. The concrete composition according to claim 1, wherein the PFBC ash is the following ash. Introducing a mixture of coal and limestone into the pressurized boiler,
When the pressurized fluidized bed combustion power generation system having the steps of fluidizing and burning the mixture is operated, ash scattered toward the top of the boiler together with combustion gas has an average particle size of 10 to 40 μm. Ashes collected. 3. The concrete composition according to claim 1, wherein the concrete composition comprises PFBC ash, cement, fine aggregate and coarse aggregate. 4. The concrete composition according to claim 1, wherein the concrete composition comprises PFBC ash, cement and fine aggregate. 5. The method according to claim 3, further comprising various admixtures (agents).
Or the concrete composition according to 4. 6. The concrete composition according to claim 1, wherein the PFBC ash is blended in an amount of 60% by weight or less based on the concrete composition. 7. The PFBC ash has a Blaine specific surface area of 100.
Concrete composition according to claim 1 is 0 cm ² / g or more. 8. The combustion temperature of a mixture of coal and limestone,
The concrete composition according to claim 1, wherein the temperature is 700 to 950 ° C. 4. 9. The concrete composition according to claim 7, wherein the pressure in the boiler is 4 to 18 kg / m ² . 10. The oxygen concentration in boiler exhaust gas is 1.5 to
The concrete composition according to claim 1, which is 8.0%. 11. The concrete composition according to claim 1, further comprising a BM ash as defined below. BM ash: When a mixture of coal and limestone is introduced into a pressurized boiler, and the mixture is fluidized and fired, a pressurized fluidized bed combustion power generation system having a step of operating is used.
Ash that does not scatter with the combustion gas toward the top of the boiler and can be collected from the bottom of the boiler is defined as BM ash.