JP3174449B2 - Method of melting coal ash - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates are those which relate to melt process how coal ash discharged from a boiler or the like of thermal power plants.

[0002]

2. Description of the Related Art As one of the methods for treating coal ash as described above, a melting treatment using an electric melting furnace is conventionally known. A common example of the electric melting furnace is a submerged arc furnace in which a molybdenum electrode is inserted to the inside of the liquid surface and the coal ash is melted by energizing an arc between the electrodes.

[0003] However, coal ash usually contains 3 to 6% by weight of unburned carbon together with iron oxide. It is reduced in minutes and becomes molten iron in the furnace. Then, there is a problem that the molten iron erodes the molybdenum electrode and the molybdenum orifice. Further, for this purpose, there is a problem that it is necessary to discharge the molten iron from the molten iron outlet to the outside of the furnace.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention is to solve the conventional problems described above, provides a melting treatment how coal ash generation of molten iron causing erosion in an electric melting furnace can be prevented It was done to do so.

[0005]

Means for Solving the Problems A method for melting coal ash according to the present invention, which has been made to solve the above-mentioned problems, comprises an unburned coal.
Coal ash containing elemental and iron oxide components is converted to molybdenum electrodes.
Method for melting with a submerged arc furnace equipped with
Atmosphere with air ratio of 1.5 or more by rotary kiln
Heat treatment to 700-900 ° C under
Coal ash whose content is less than 1% by weight is used as a molten raw material
While suppressing the reduction reaction of the contained iron oxide,
And then melting.

[0006]

According to the method of the present invention, coal ash is rotary-killed.
700 to 9 in an atmosphere with an air ratio of 1.5 or more
By calcining at 00 ° C. , the unburned carbon content is reduced to less than 1% by weight, and the reduction reaction of the contained iron oxide is suppressed.
In an electric melting furnace. As a result, the content of the unburned carbon content becomes extremely low, so that the phenomenon that iron oxide is reduced by the unburned carbon content and becomes molten iron in the furnace is prevented, and the erosion of the furnace by the molten iron can be eliminated. At the same time, dangerous work of discharging molten iron out of the furnace can be eliminated.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the illustrated embodiments. FIG. 1 shows a hopper for receiving coal ash, 2 a vibrating feeder provided at its outlet, and 3 an electric melting furnace for melting coal ash. The electric melting furnace 3 is provided with a plurality of molybdenum electrodes 4 as described above, and is configured to melt coal ash by energizing an arc between these electrodes 4 and 4. An orifice 5 made of molybdenum is provided at the center of the bottom, and a control needle 6 is provided.
Thus, the outflow of the melt can be controlled. 7
Is a distributor for uniformly distributing coal ash to the liquid surface of the electric melting furnace 3.

[0008] A rotary kiln 8 is provided between the hopper 1 and the electric melting furnace 3. As shown in FIG. 2, the rotary kiln 8 includes a plurality of blades 10 extending in an axial direction inside a rotating retort 9. The coal ash supplied from the hopper 1 is heated to 700 to 900 ° C. while passing through the inside of the rotary kiln 8,
After an average residence time of 3 minutes or more, it is discharged from the lower end. During that time, the coal ash is stirred by the blade 10 and sufficiently contacts the atmosphere in the furnace, and is also crushed by the impact of the lump scraped up by the blade 10 when falling.

As shown in FIG. 1, a large number of burners 11 are provided in the furnace body of the rotary kiln 8. Air is supplied into the furnace by a blower 12, whereby the atmosphere in the furnace is maintained at an air ratio of 1.5 or more. Therefore, the coal ash is sufficiently calcined while passing through the rotary kiln 8 and the unburned carbon content is reduced to less than 1% by weight and then discharged from the lower end to the distributor 7. Reference numeral 13 denotes a heat exchanger for recovering heat from the high-temperature gas discharged from the rotary kiln 8.

In the embodiment, coal ash containing 4.5% by weight of unburned carbon was continuously supplied to the rotary kiln 8 at a flow rate of 220 kg / hr. Retort 9 of rotary kiln 8 is high
Equipped with a 50 mm blade 10, the internal temperature is 850 ° C, the air flow rate in the furnace is 180 Nm ³ / hr, and the air ratio at this time is 2.
It was 0. The size of the retort 9 is 700mm in diameter,
The length is 4000mm. As a result of calcination with an average residence time of 10 minutes, the unburned carbon content in the coal ash discharged from the lower end was reduced from the initial 4.5% by weight to 0.6% by weight. The content of iron oxide in coal ash is 1.7% by weight.

The coal ash fired in this manner was supplied to the above-mentioned electric melting furnace 3 and melted for 24 hours. No molten iron was generated, and no damage to the molybdenum electrode 4 or the orifice 5 was observed. In contrast, the content of iron oxide was 1.7
When coal ash containing 4.5% by weight and unburned carbon content is directly melted in the electric melting furnace 3, if melted for 24 hours, molybdenum is eroded violently by molten iron. The orifice function has been completely lost.

[0012]

As described above, according to the method of the present invention, the unburned carbon content in the coal ash is reduced to less than 1% by weight by firing the coal ash under the above-mentioned predetermined conditions. Thus, the phenomenon in which iron oxide is reduced by unburned carbon and becomes molten iron in the furnace is prevented, and erosion of the furnace by molten iron can be eliminated. In addition, it is possible to eliminate dangerous work of discharging molten iron outside the furnace. Accordingly, the present invention is a melt process how a coal ash which solves the conventional problems, when contributing to the development of industries is very large.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view of a rotary kiln.

[Explanation of symbols]

 3 Electric melting furnace, 8 rotary kiln, 10 blades

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasufumi Watanabe 2-4-1, Nishi-Atsujigaoka, Chofu-shi, Tokyo Tokyo Electric Power Company R & D Laboratory (72) Inventor Tadashi Takeda 3-78 Fukakawacho, Nakamura-ku, Nagoya-shi, Aichi Prefecture Address Lions Mansion 404 Fukagawacho (72) Inventor Tetsuya Yanase 1-106 Shingumachi, Handa-shi, Aichi Japan NGK Shingu Shrine House 202, (56) References JP-A-57-24687 (JP, A) JP-A-57-24687 49-91908 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B09B 3/00 F23J 1/00

Claims (1)

(57) [Claims] 1. Coal ash containing unburned carbon and iron oxide
In a submerged arc furnace equipped with molybdenum electrodes.
This is a method of melting and processing air with a rotary kiln.
Heat to a temperature of 700 to 900 ° C in an atmosphere with a ratio of 1.5 or more
A stone that has been treated to reduce the unburned carbon content to less than 1% by weight.
By using coal ash as the raw material, the iron oxide content
A method for melting coal ash, comprising performing melting treatment while suppressing a reduction reaction .