JPH09290234A - Method of reforming coal ash and method of using reformed cool ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To burn and remove carbon contained in coal ash and at the same time to melt the carbon ash to make its granular shape a spherical shape by melt-spraying the coal ash, to improve its fluidity when it is used as a concrete admixture substituting for sand to efficiently use all coal ash generated and also to save resources. SOLUTION: A thermal spraying device constituted of a thermal spraying burner, a lance, a utility control panel and a powder feeder and a furnace body for providing a space for performing thermal spraying are used. The thermal spraying device is installed in an opening of the furnace body so that flames formed by the thermal spraying burner 1 may be blown into the furnace body. Coal ash 2 is sprayed from the thermal spraying burner 1 together with carrier gas so that they may be passed through a thermal spraying flame 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reforming coal ash generated during coal combustion in a power plant and a method for using the reformed coal ash.

[0002]

2. Description of the Related Art Currently, about 60% of all coal ash is reused as a raw material for cement and the like, and the remaining about 40% is treated as industrial waste by landfill. However, disposal of coal ash, which will be generated in large quantities, will cause problems in the landfill and the environment.

Coal ash contains unburned carbon,
If a large amount of coal ash is used as an admixture material for concrete, the water reducing agent and air entraining agent added to the cement are adsorbed by the carbon contained in the coal ash, and the function of each additive is impaired. Use is limited depending on the amount. The removal of carbon contained in coal ash has been proposed in JP-A-4-300663.
That is, when the coal ash discharged from the incinerator is crushed by the crushing device, the coal ash in a state in which unburned carbon is wrapped with silica is separated into silica and unburned carbon. Further, the coal ash in a state where the silica content and the unburned carbon are separated is sorted into a silica content and unburned carbon by a sorting device to remove the unburned carbon.

Further, Japanese Patent Laid-Open No. 4-70529 discloses that
After the coal ash is mixed with the exhaust gas containing dust at the outlet of the coal ash reforming furnace and preheated, it is separated from the exhaust gas and supplied to the coal ash reforming furnace, and oxygen-enriched air is supplied to the coal ash reforming furnace. Furthermore, this oxygen-enriched air is preheated by exchanging heat with the reformed ash in the reformed ash cooler outside the reforming furnace, and then heated by exchanging heat with the combustion gas in the in-reactor inside the reforming furnace. Methods have been proposed.

[0005]

However, in the above method, there are problems that the process is complicated, the equipment scale is large, the condition equipment is complicated depending on the quality of the coal ash, and the treatment efficiency is low. An object of the present invention is to modify coal ash so that it can be used as an admixture for concrete so as to reduce the amount of carbon, and to effectively utilize the total amount of coal ash generated.

[0006]

SUMMARY OF THE INVENTION The present invention has been provided to solve the above problems, and the gist of the invention is as follows.
It is as follows. (1) In a thermal spraying apparatus composed of a thermal spraying burner, a lance, a utility control panel, and a powder feeder, the thermal spraying burner is installed in the furnace body opening so that the flame formed in the thermal spraying burner is blown into the furnace body. Coal ash is injected from a burner together with a carrier gas so as to pass through the thermal spray flame to burn off some or all of the carbon contained in the coal ash, and at the same time melt the coal ash to make it spherical.

(2) The coal ash modified by the method of (1) is used as a substitute for concrete sand. In the coal ash reforming method of the present invention, when coal ash is injected into a high-temperature spray flame together with a carrier gas, the coal ash becomes high in temperature when passing through the flame due to radiant heat from the spray flame. At that time, the carbon contained in the coal ash reaches the ignition temperature, the oxygen in the carrier gas burns the carbon, and the carbon contained in the coal ash is removed. At the same time, the coal ash itself also melts, and the particle shape of the coal ash is spherical. By installing a thermal spray burner at the opening of the furnace body and blowing the thermal spray flame into the furnace, the temperature inside the furnace becomes high due to the thermal spray flame, forming a thermal spray flame in the atmosphere and modifying the above coal ash. Compared with the case of quality, the thermal efficiency is remarkably improved and the throughput of coal ash is increased. Since the carbon contained in the coal ash can be removed, and the coal ash itself can be made spherical, it is possible to use the modified coal ash as a substitute for concrete sand, and the particle shape of the coal ash can be made spherical. Therefore, when mixed with cement, gravel, etc., the fluidity is improved and the filling property is also improved.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. An embodiment of the method for reforming coal ash according to the present invention is shown in FIG. In FIG. 1, a lance 2 is connected to and supports the thermal spray burner 1 and is mounted on a lance driving machine 3, and the lance 2 is moved forward and backward by the lance driving machine 3 to move forward and backward to form a thermal spray flame formed on the thermal spray burner 1. It is installed in the opening of the furnace body 6a so that 10 is blown into the furnace body 6a. The utility to be reformed is supplied from the primary side utility pipe 9a to the utility control panel 4, and after being adjusted to a predetermined pressure and flow rate in the utility control panel 4, the utility gas is passed through the fuel gas pipe 9b, the cooling water pipe 9c, and the lance 2. , To the thermal spray burner 1. The fuel gas is injected from the thermal spray burner 1 and burned to form a thermal spray flame 10.
The cooling water is drained through the lance 2 and the cooling water pipe 9d with the thermal spray burner 1 as a turning point. Further, in the utility control panel 4, the carrier gas adjusted to a predetermined pressure and flow rate is supplied to the powder feeder composed of the powder hopper 5b and the cutting machine 5c through the carrier gas pipe 9e, and the cutting machine 5c is used. The pre-reformation coal ash 11 cut out in a fixed amount is jetted together with the carrier gas from the thermal spray burner 1 into the thermal spray flame 10 through the powder pipe 9f and the lance 2.

The unmodified coal ash 11 is supplied to the powder hopper 5b by supplying the unmodified coal ash 11 to the replenishment powder hopper 5a installed above the powder hopper 5b through the on-off valve 5d. In addition, by opening the on-off valve 5d, the pre-reforming coal ash 11 is dropped from the replenishing powder hopper 5a and dropped into the powder hopper 5b. When the remaining amount of the pre-reforming coal ash in the replenishing powder hopper 5a is reduced to a predetermined amount by charging the refilling powder hopper 5b, the pre-reforming coal ash 11 is fed into the replenishing powder hopper 5a and the powder hopper Prepare for supply to 5b.

A dust collector 6b is installed in the furnace body 6a through a conduit from the top 6a of the furnace body 6a in order to forcibly exhaust the fuel exhaust gas in the furnace body 6a and separate and recover the reformed coal ash 12 in the fuel exhaust gas. ing. The pre-reformation coal ash 11 injected into the thermal spray flame 10 passes through the thermal spray flame 10, is reformed by burning carbon and melting the pre-reformation coal ash 11, and is deposited on the bottom of the furnace body 6a by gravity. . The reformed coal ash 12 accumulated in a predetermined amount is provided with an opening / closing lid 7a installed at the bottom of the furnace body 6a.
Is opened, the coal ash 12 after reforming is recovered from the furnace body 6a by dropping and depositing it in a recovery box 8a installed below the opening / closing lid 7a. On the other hand, after passing through the spray flame 10, it enters the dust collector 6b together with the combustion exhaust gas, and is reformed with the filter (not shown) installed in the dust collector 6b.
Are separated, and when a predetermined amount is deposited below the dust collector 6b, the opening / closing lid 7b installed below the dust collector 6b is opened to drop and deposit in the collection box 8b.
Are collected from the dust collector 6b.

In the recovery method shown in FIG. 1, coal ash generated from a coal-fired power plant is used as fuel gas for propane,
By using oxygen as a supporting gas and premixing propane and oxygen in the thermal spray burner and injecting it together with oxygen in the carrier gas into the thermal spray flame formed in the thermal spray burner, the carbon in the coal ash passes through the thermal spray flame. It is burned (carbon + oxygen) and removed. The flame temperature at this time is 2200 ℃
Was in the range of ˜2300 ° C. At the same time, the coal ash itself melts and vitrifies (amorphous), and the grain shape is spherical (Table 1).

[0012]

[Table 1]

When the thermal spray burner is reformed in the atmosphere outside the furnace in the same manner as described above, the amount of heat dissipated from the thermal spray flame to the atmosphere increases and the amount of heat transfer to the coal ash decreases. The amount is reduced by about 30-40%. In addition, since the coal ash itself vitrifies, the carbon contained in the coal ash can be included in the glass even if it remains after combustion removal, so there is no effect of residual carbon on cement additives such as water reducing agents and air entraining agents. .

The fuel gas is not limited to propane, but may be acetylene, coke oven gas, hydrogen or the like that forms a high temperature flame that can melt coal ash when passing through a flame. Kerosene may be used as the solid fuel, for example, pulverized coal, metallic aluminum or metallic silicon. The oxygen concentration is not limited as long as the supporting gas is mixed with the fuel gas to obtain a high temperature flame. The flame temperature also differs depending on the difference in these fuels.

Further, the carrier gas is not limited to oxygen, but may be any oxygen concentration that can burn carbon contained in coal ash. Similarly, if a gas having an oxygen concentration capable of burning carbon can be injected into the thermal spray flame and the carbon contained in the coal ash can be burned, a method other than the carrier gas injection may be used.

According to JIS R 5201, there is no problem in using the coal ash modified by the method of the present invention as a substitute for concrete sand. Portland cement, standard sand, unmodified and modified coal. A cement strength test was performed and evaluated using ash. The results are shown in Table 2.

[0017]

[Table 2]

The examples in Table 2 are obtained by replacing the modified coal ash obtained by the present invention with standard sand. Comparative Example 1 is JI
It is the mixing ratio of cement and standard sand specified in S R 5201, and can be said to be at the level of the existing technology. In Comparative Example 2, the unmodified coal ash was replaced with standard sand. The compressive strength is a value of 28 days of age. Each of the examples showed a strength equal to or higher than the current technical level of Comparative Example 1. Further, the strength was improved by modifying the coal ash even in the same mixing ratio as in Example 2 and Comparative Example 2. The alternative rate of the modified coal ash of the present invention for sand is preferably 70% or less. If it exceeds 70%, the ratio of the specific surface area of the modified coal ash to the total specific surface area of the material constituting the unhardened concrete increases, the added water is adsorbed by the modified coal ash, and the water necessary for the cement is sufficient. Since it cannot be obtained, it may be necessary to increase the amount of added water.

[0019]

According to the present invention, it is possible to ensure the quality of replacing coal ash with concrete sand, so that the entire amount can be effectively utilized and resource saving can be achieved. Further, since the fluidity of the modified coal ash is good, improvement in workability can be expected in the mixing, kneading and construction with cement or gravel. Furthermore, since the combustion exhaust gas contains water and carbon dioxide gas, if the combustion exhaust gas is brought into contact with steelmaking slag containing free lime to stabilize the free lime in the form of calcium hydroxide or calcium carbonate, the combustion exhaust gas Will be effectively used. Further, the reforming method in the present invention is not limited to coal ash, but can be used for reforming other industrial wastes such as aluminum residual ash and sludge.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an example of a coal ash reforming method and apparatus according to a first embodiment of the present invention.

[Explanation of symbols]

 1 Spraying burner 2 Lance 3 Lance driver 4 Utility control panel 5a Powder hopper for replenishment 5b Powder hopper 5c Cutting machine 5d Open / close valve 6a Furnace body 6b Dust collector 7a, 7b Open / close lid 8a, 8b Recovery box 9a Primary side utility piping 9b Fuel gas piping 9c, 9d Cooling water piping 9e Carrier gas piping 9f Powder piping 10 Thermal spray flame 11 Coal ash before reforming 12 Coal ash after reforming

Claims (2)

[Claims] 1. A flame formed on a thermal spray burner using a thermal spray apparatus comprising a thermal spray burner, a lance, a utility control panel and a powder feeder and a furnace body providing a space for performing thermal spray processing. A method for reforming coal ash, characterized in that a thermal spraying device is installed in the furnace body opening so as to be blown into the furnace body, and coal ash is injected together with carrier gas from the thermal spray burner so as to pass through the thermal spray flame. . 2. A method of using modified coal ash, characterized in that the coal ash modified by the method for modifying coal ash according to claim 1 is used as a substitute for concrete sand.