JP2000213709A - Manufacture of low unburned carbon ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an unburned carbon component in a residual powder which is generated by a heat treatment of coal, waste or the like, and provide a low unburned carbon ash of a high added value, by burning the residual powder of which the average particulate diameter is a specified value or lower, at a specified temperature in a fluidized bed furnace which is filled with a particle having a specified particulate diameter. SOLUTION: A residual powder which is generated in the combustion, gasification, liquefaction or thermally decomposed object, of coal and industrial waste or the like, is an objective. Especially, a fly ash from a combustion boiler of dust coal is preferable. As a residual powder, one of which the average particulate diameter is 20 μm or lower is used. The powder is burned in a fluidized bed furnace while being fluidized, and the unburned carbon component is reduced. In this case, as a fluidized bed furnace for use, one in which a particle having a particulate diameter being 10-100 times of the average particulate diameter of the residual powder is filled. A combustion temperature in the fluidized bed furnace is selected in a range of 700-1,000 deg.C. When the temperature is less than 700 deg.C, the unburned carbon component is not sufficiently reduced, and at 1,000 deg.C or higher, troubles such as the molten residual powder works against fluidization are generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing low-burning unburned carbon ash, and more particularly, to a method for removing residual powder such as fly ash generated during heat treatment of organic resources such as coal, petroleum and waste. The present invention relates to a method for efficiently producing high-quality low-unburnt carbon ash by reducing unburned carbon content by performing combustion treatment in a bed furnace.

[0002]

2. Description of the Related Art As one of industrial wastes, coal ash discharged from coal combustion, so-called fly ash, is known. In Japan, this coal ash was produced in 1996
Approximately 7.2 million tons are released in the fiscal year, and
About 0% are disposed of. Considering the environmental aspects such as the large amount of waste itself or the generation of carbon dioxide due to the energy consumption during transportation of the waste, the reduction of future ash disposal sites, the rising ash disposal costs, etc. Development of technology for effective utilization of coal ash is urgently needed. Current,
High-quality fly ash is traded as a substitute for cement for a fee. JIS-compliant fly ash with such high added value has a particle size distribution, unburned carbon content in ash, specific surface area, etc. Because of the difficulty in quality control, only about 7% of the 500,000 tons are actually used. For this reason, in Japan, the JIS standard for fly ash is currently being revised, and the existing quality standards have been expanded from one rank to four ranks to promote recycling. If high-value-added fly ash is generated and recycling is promoted as a substitute for cement for a fee, only the reduction of the amount of waste itself and the improvement of the environment by reducing the carbon dioxide generated during waste transportation and cement production will be improved. Rather, it is expected that operability will be improved through effective use of ash disposal sites at coal utilization sites and drastic reduction of ash disposal costs.

Conventionally, there are few practical techniques for improving the quality of fly ash. For example, using a cyclone classifier or the like, the difference in particle density and particle size is utilized aerodynamically to obtain unburned carbon content and particle size distribution. Adjustments are only made in part. However, in this method, since a large amount of fine ash is entrained in the cyclone, a large proportion of the fine particles entrained in the particle group remains on the coarse particle side, and the classification is insufficient. In addition, it is sufficient that the unburned carbon component is separated from the mineral substance. In this case, there is a problem that the separation of the unburned carbon content is insufficient. Fly ash generally contains several percent or more of unburned carbon, but ash conforming to JIS is required to have as little unburned carbon as possible.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a method for producing residual powder generated by heat treatment (combustion, gasification, liquefaction, thermal decomposition, etc.) of organic resources such as coal, petroleum, and waste under such circumstances. It is an object of the present invention to provide a method for efficiently producing high-quality, low-value, low-carbon ash with high added value by reducing the unburned carbon content therein.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have found that a residue powder having an average particle size of a certain value or less is reduced to an average particle size of the residue powder. Of 10
It has been found that the object can be achieved by burning at a specific temperature while flowing in a fluidized bed furnace filled with particles having a particle size 100 times larger. The present invention
It has been completed based on such knowledge. That is,
The present invention provides a fluidized-bed furnace in which a residual powder having an average particle diameter of 20 μm or less generated by heat treatment of an organic resource is filled with particles having a particle diameter of 10 to 100 times the average particle diameter of the residual powder. And burning the mixture at a temperature in the range of 700 to 1000 ° C. while flowing the same.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing low unburned carbon ash of the present invention, there is no particular limitation on residue powder generated during heat treatment of an organic resource used as a raw material, for example, coal, petroleum, general waste, Residual powder generated during combustion, gasification, liquefaction, or thermal decomposition of waste such as industrial waste can be mentioned. Among them, fly ash collected by a dust collector from a pulverized coal combustion boiler is particularly preferable. In the present invention, the residual powder has an average particle size of 2
Those having a size of 0 μm or less are used. For fly ash,
Normally, spherical particles having a particle size of about 1 to 6 μm and a particle size of several tens μm
To a certain degree, and the proportion of the irregular particles increases as the unburned carbon content increases. The unburned carbon content in the residual powder of the raw material depends on the origin of the residual powder, but generally a residual powder containing about 5 to 40% by weight of unburned carbon is used. .

In the method of the present invention, the residual powder having an average particle diameter of 20 μm or less is subjected to a combustion treatment while flowing in a fluidized bed furnace to reduce the unburned carbon content. In this case, a fluidized-bed furnace filled with particles (fluidized particles) having a particle diameter 10 to 100 times the average particle diameter of the residual powder to be used is used. If the particle size of the fluidized particles is out of the above range, fluidization does not sufficiently occur, and the object of the present invention cannot be achieved. The material of the fluidized particles to be charged into the fluidized bed furnace is not particularly limited, but particles such as alumina, silica, silica-alumina, titania, and zirconia are preferably used. Air is usually used as the fluidizing gas, and the flow rate is a rate sufficient to enable fluidization and a rate sufficient to allow the residence time of the residual particles to reach the desired unburned carbon content. There is no particular limitation.

[0008] In the present invention, the combustion temperature in the fluidized bed furnace is selected in the range of 700 to 1000 ° C. If the temperature is lower than 700 ° C., the unburned carbon content is not sufficiently reduced, and the object of the present invention cannot be achieved. If the temperature is higher than 1000 ° C., inconveniences such as melting of the residual powder and not flowing are caused. Considering the effect of reducing unburned carbon and the fluidity, the combustion temperature is preferably in the range of 800 to 900C. A part of the residue powder burned in this way jumps out of the fluidized bed along with the fluidizing gas.Therefore, by collecting it using a cyclone or a filter, the unburned carbon content is reduced. In addition, low unburned carbon ash (combustion treated ash) having a relatively uniform particle size can be obtained. The content of unburned carbon in the burnt ash obtained in this manner is usually less than 5% by weight, and has a sufficient quality required for use in the cement / concrete field.

[0009]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The content of unburned carbon in fly ash and burned ash (low unburned carbon ash) as raw materials was measured by burning at 815 ° C. using a thermobalance. Example 1 As a fluidized bed furnace, a quartz reactor having an inner diameter of 2.5 cm and a height of 30 cm charged with 32 ml of 32-62 mesh alumina particles as fluidized particles was used, and fly ash jumped out of the reactor. Was collected by cyclone and filter. As a fly ash, a Shanxi coal ash with an average particle diameter of 10.0 μm and an unburned carbon content of 17.6% by weight, collected from an experimental pulverized coal combustion furnace, is used, and the height of the fluidized bed is 8 cm. Thus, the reactor was charged, and the fluidizing gas (air) flow rate was 7.2 cm / sec, and the temperature was 82
A combustion test was performed at 0 ° C. Recovery rate of combustion ash,
The unburned carbon content and the average particle size of the recovered combustion ash were determined, and the results are shown in Table 1. The recovery rate is a value expressed as a percentage by dividing the weight of all the combustion ash recovered from the outlet of the reactor by the weight of fly ash of the supplied raw material.

Examples 2 to 4 In Example 1, except that the height of the stationary bed of the fluidized bed and / or the flow rate of the fluidizing gas were changed as shown in Table 1,
The same operation as in Example 1 was performed. The results are shown in Table 1.

[0011]

[Table 1]

Examples 1 and 2 are comparisons in the case where the stationary height of the fluidized bed is changed. The higher the bed height, the higher the removal rate of unburned carbon in the combustion ash. The unburned carbon content in the recovered combustion ash is extremely low at 3.3% by weight. One of the reasons why the unburned carbon removal rate was improved when the bed height was high is thought to be due to the increased residence time of fly ash in the fluidized bed. Examples 2 to 4 are comparisons in the case of changing the gas flow rate. As the gas flow rate increases, the recovery rate of the combustion ash increases, but the unburned carbon content in the recovered ash also increases. This is because the residence time of the fly ash in the fluidized bed is reduced by increasing the gas flow rate. In order to effectively utilize fly ash in the field of cement and concrete, it is required that the unburned carbon content in the ash be 5% by weight or less.
Although the recovery rate was somewhat low, it became clear that the unburned carbon content in the combustion ash could be realized to 5% by weight or less.

Examples 5 and 6 In Example 1, Drayton coal combustion having an average particle diameter of 6.1 μm and an unburned carbon content of 9.5% by weight recovered from an experimental pulverized coal combustion furnace was used as a raw material fly ash. Using ash,
The same operation as in Example 1 was performed except that the stationary height of the fluidized bed and the fluidized gas flow velocity were changed as shown in Table 2.
Table 2 shows the results.

[0014]

[Table 2]

In Example 5 and Example 6, the combustion conditions were the same, and although the fly ash recovery rate and the unburned carbon content were slightly different from the results of the two experiments, the reproducibility was almost the same. It can be judged as good. In the case of Drayton's combustion ash, the uncarbon content in the recovered ash is at most about 1% by weight, compared with the case of the Shanxi coal combustion ash in Examples 1 to 4.
It can be seen that unburned carbon can be efficiently removed.

[0016]

According to the present invention, unburned carbon is reduced by burning residues such as fly ash generated during heat treatment of organic resources such as coal, petroleum and waste in a fluidized bed furnace. As a result, high-quality, low-burning unburned carbon ash can be efficiently produced. The low unburned carbon ash obtained in this way is suitably used, for example, as a cement substitute.

Claims (3)

[Claims] 1. A fluidized bed in which a residue powder having an average particle diameter of 20 μm or less generated by heat treatment of an organic resource is filled with particles having a particle diameter of 10 to 100 times the average particle diameter of the residue powder. 700-1000 while flowing in a furnace
A method for producing low unburned carbon ash, characterized by burning at a temperature in the range of ° C. 2. The residue powder having an average particle size of 20 μm or less generated by heat treatment of an organic resource is a residue powder generated during combustion, gasification, liquefaction, or thermal decomposition of coal, petroleum, or waste. The method for producing low unburned carbon ash according to the above. 3. The method for producing low unburned carbon ash according to claim 2, wherein the residual powder having an average particle size of 20 μm or less generated by heat treatment of the organic resources is fly ash.