JPS6218505B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing artificial fine aggregate.

The use of coal is expected to further expand due to uncertain oil supplies and soaring prices, and as a result, the amount of coal ash generated is expected to increase rapidly. Therefore, in order to deal with this problem, it is particularly desirable to establish a technology that effectively utilizes coal ash, which is generated in large quantities from coal-fired power plants, without using as much energy or auxiliary materials as possible. In recent years, various studies have been conducted on the production of artificial lightweight aggregates using coal ash as a raw material.
Most of these studies are aimed at coarse aggregates, and there are currently no reports on methods for producing fine aggregates using moving grate equipment. By the way, when producing fine aggregate using a grate-type firing device, the main problems are the amount of unburned coal in the coal ash and the air permeability in the layer during firing, and the conventional firing method requires various firing conditions. Even when the pellets are changed, the ventilation within the layer is inhibited, resulting in the pellets being fused together, resulting in a disadvantage that normal pellets cannot be obtained.

Therefore, an object of the present invention is to provide a method for producing artificial fine aggregate that can eliminate the above-mentioned drawbacks.

That is, the present invention provides a method for producing artificial fine aggregate by granulating coal ash into raw pellets with a diameter of 0.5 to 5 mm, and firing the raw pellets using a grate-type firing device. Among the fired pellets that have already been fired, those having approximately the same particle size as the above-mentioned raw pellets are added and mixed, and the mixed pellet is fed onto a grate-type pallet and burned. This is a method for producing artificial aggregate characterized by the following.

According to this method, fired pellets that have already been fired and are approximately the same size as the raw pellets are added and mixed into the raw pellets before firing, thereby preventing the raw pellets from fusing together during firing. It can be prevented.

Hereinafter, one embodiment of the present invention will be described based on the drawings. First, the general configuration will be explained.

1 is a coal ash tank for storing coal ash; 2 is a humidifier for pre-humidifying the coal ash quantitatively sent out from the coal ash tank 1 to make it easier to granulate; 3 is a humidifier for storing the pre-moistened coal ash.
A dish-type or kiln-type granulator is used to granulate raw pellets with a diameter of 0.5 to 5 mm, 4 is a grate-type firing device for firing the raw pellets, and granulator 3 is a granulator that granulates raw pellets and fired pellets in the middle of the process. It is connected by a pellet feed line 6 with a mixer 5. The firing device 4 includes an endless grate-type pallet 7 that moves from a supply section a to a discharge section b;
A drying furnace 8 for drying the raw pellets placed on the pallet 7, an ignition furnace 9 for igniting the unburned coal in the surface layer of the pellets dried by the drying furnace 8, and a movement route for the pallet 7. It is composed of a plurality of wind boxes 10 provided below, and exhaust fans 11 and 12 for sucking and passing the atmosphere into the pellet through these wind boxes 10, and sucking exhaust gas from the high temperature part wind box 10A. is sent to the drying oven 8 by an exhaust fan 12, and the suction exhaust gas from other wind boxes 10 is discharged into the atmosphere by the exhaust fan 11 via a dust collector 13. Reference numeral 14 denotes a sieving machine that removes coarse defects with a particle size of 5 mm or more from the fired pellets fired by the firing device 4, and 15 denotes a product fine aggregate from which the rejects have been removed by the sieving machine 14. A first distribution chute for taking out a portion, 16 is the first distribution chute 1
This is a transfer line for sending the fired pellets taken out by 5 to the firing device 4 as pallet bedding. Further, a second distribution chute 17 is provided in the middle of the transfer line 16, and a portion of the fired pellets is supplied to a mixer 5 provided in the middle of the raw pellet supply line 6.
In this mixer 5, fired pellets having approximately the same particle size as the raw pellets are added to the raw pellets having a diameter of 0.5 to 5 mm and mixed uniformly.

Next, the manufacturing method will be explained. Coal ash tank 1
The coal ash produced is pre-humidified by a humidifier 2 and then granulated by a granulator 3 into green pellets with a diameter of 0.5 to 5 mm. The raw pellets are then sent to the firing device 4 via the raw pellet supply line 6, but in the mixer 5 in the middle of the raw pellet supply line 6, a predetermined amount of fired pellets that have already been fired and have the same particle size as the raw pellets are mixed. It is added and mixed into the raw pellets (for example, in a proportion of 10 to 50% by weight). In this way, the mixed pellets made by mixing raw pellets and fired pellets are
After being supplied onto the pallet 7 and dried in the drying oven 8, the surface layer is ignited in the ignition furnace 9, and after being ignited, it is fired in order from the upper layer to the lower layer by absorption of the atmosphere. be done. The fired pellets are discharged from the discharge section b to the sieve 14 to remove defective particles. Then, a part of the fired pellets from which the defects have been removed is taken out from the first distribution chute 15 and sent to the mixer 5 and the firing device 4 via the transfer line 16, and the remaining fired pellets are It is stored as a product (artificial fine aggregate). In this way, fired pellets with the same particle size as the raw pellets are added and mixed into the raw pellets in advance, and then the mixed pellets themselves are fired in a grate type firing device, so there is almost no fusion between the pellets. . The reason why the pellets do not fuse together is because almost no unburned coal remains in the already solidified fired pellets, and the calorific value of the fired pellets is lower than that of raw pellets, so the amount of heat in the entire pellet layer is It is thought that because of the relaxation, adjacent pellets do not fuse together.
According to the above method, since the pellets do not fuse together, the unburned coal in the pellets can be completely combusted.

Here, an experimental example using the above manufacturing method will be explained. In addition, in this experiment, coal ash containing 6.33% unburned coal was used, and
A batch-type firing pot with an inner diameter of 350 mm and a height of 500 mm was used. First, coal ash is granulated into raw pellets with a diameter of 0.5 to 3 mm using a dish-type granulator with an inner diameter of 800 mm, and calcined pellets of the same particle size are added to the raw pellets at a ratio of 50% (wt%). The above mixed pellets were then placed in a firing pot lined with bedding pellets (same as the above fired pellets) with a thickness of 50 mm, and then heated with hot gas at about 200°C for 4 minutes in the firing pot. The mixed pellets are dried by passing from the top to the bottom, and then hot gas at about 900℃ is passed through for 30 seconds to ignite the unburned coal in the mixed pellets on the surface of the layer, after which the temperature at the bottom of the mixed pellet layer is 100℃. Firing and cooling were performed by suctioning out the atmosphere until the temperature was . Comparing the appearance of the fired pellets obtained in the above experiment and those obtained by the conventional method, it is found that the pellets in the conventional method have a state of fusion between the pellets on the surface and inside ( In the attached reference photos (a) (planar view) and (b) (cross-sectional view)), no fusion of pellets is observed on the surface or inside of the pellets according to the above experimental example (see attached reference photos).
(See (c) (planar view)). In addition, the unburned coal content is 0.5%.
It is almost completely burned. In addition, when producing fine aggregate by the method described above, the blending ratio of raw pellets and fired pellets, the amount charged into the firing pot, the ignition temperature, the ignition time, etc. are determined depending on the content of unburned coal in the coal ash. For example, as the amount of unburned coal increases, it is necessary to increase the blending ratio (addition ratio) of fired pellets, and it is necessary to reduce the amount of mixed pellets charged into the firing pot. In addition,
It has been found that if the amount of unburned coal is in the range of approximately 2 to 8%, the ignition temperature may be 1000°C or less and the ignition time may be approximately 30 seconds. As described above, according to the present invention, calcined pellets that have already been fired and have approximately the same particle size as the raw pellets are added and mixed into the raw pellets after granulation, and the mixed pellets are mixed. Since the pellets are fed onto a grate-type pallet and fired, the unburned coal in the pellets can be completely combusted with almost no fusion between the pellets.

[Brief explanation of the drawing]

The drawings show the manufacturing process of one embodiment of the present invention. 3... Granulator, 4... Grate type baking device, 5...
... mixer, 6 ... pellet supply line, 7 ... pallet, 15 ... first distribution chute, 16 ... transfer line, 17 ... second distribution chute.

Claims (1)

[Claims] 1. In a method of producing artificial fine aggregate by granulating coal ash into raw pellets with a diameter of 0.5 to 5 mm and firing the raw pellets using a grate-type firing device, the raw pellets after granulation already include An artificial fine aggregate characterized in that fired pellets having approximately the same particle size as the above-mentioned raw pellets are added and mixed, and the mixed product is fed onto a grate-type pallet and fired. manufacturing method.