JPS6252152A - Facilities for manufacturing aggregate for concrete - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement in an apparatus for producing aggregate for concrete using finely powdered coal ash generated from the ash of a coal-fired power plant, etc. It is.

[Conventional technology]

Conventionally, there are the following methods for producing aggregate for concrete from finely powdered coal ash.

(1) Rotary kiln method The granulated material is supplied to one end of the rotary kiln, the rotary kiln is rotated, and the granulated material is heated and fired with flame or gas while being transferred to the other end.

(2) Moving grate method Granules containing unburned matter are loaded on a grate, and the granules are moved by moving the grate. During this time, gas is flowed perpendicularly to the direction of movement of the granules to bring the gas and the granules into contact (cross flow contact). The granulated material is preheated by passing relatively low temperature hot gas on the upstream side. The upper surface of the granulated material layer is brought into contact with the carbonized carbon, causing the upper surface of the granulated material to become red-hot, thereby igniting the combustible matter contained therein. By simply passing air through the downstream side, the air is heated by heat exchange with the red-hot granules, and the lower layer of the combustible material is ignited one after another, allowing the lower layer to be fired. This portable grate can handle everything from drying preheating to firing cooling.

(3) Shaft kiln method This method has been used for a long time to burn cement raw material granules, but it is hardly used now. While air is blown in and pulled out from above, the granules are in countercurrent contact with the surrounding air, and the granules are preheated and fired from the top to the bottom, and the air is preheated from the bottom.
It heats combustible combustion granules, and has excellent thermal efficiency and can be applied to the manufacture of aggregate for concrete using coal ash, but it has not been put into practical use industrially. [Problems to be Solved] (1) Rotary kiln system Heat transfer performance is also poor, and the retention rate in the equipment is low, making the equipment large and construction costs high.

In addition, unburned materials contained in coal ash cannot be heated to a high temperature until sintering, which requires extra fuel.

(2) Moving grate method Although it has excellent heat transfer properties, in terms of thermal efficiency, it is necessary to continuously assist combustion and ignite. The unburnt material of the final aggregate product is J.
IS stipulates it to be 1% or less, but with this method, if the unburned content in coal ash is as high as 5% or more, it is difficult to reduce it to below the specified value. In addition, it requires a large amount of heat-resistant alloy members and has many moving parts, resulting in high construction costs.

(3) Shaft kiln method It is superior in terms of heat transfer and heat efficiency, has a high retention rate in the equipment, and is superior to (1) and (2) above in all respects. Although auxiliary combustion is not required, it is difficult to reduce the unburned content of the final aggregate product to 1% or less as specified by JIS. When the granules are filled to a high level, the granules may be broken or worn out before firing, and the fine powder generated at this time may clog the gaps between the granules either entirely or locally.

[Means for solving problems]

As a result of extensive research in order to achieve the above object, the present invention has been developed as a concrete using coal ash, which is made by sintering granules made by granulating finely powdered coal ash containing unburned matter with a suitable binder in a shaft kiln. In the aggregate surface preparation device for coal ash granules, a moving grate for adjusting unburned content is provided on the upstream side in the flow direction of the coal ash granules, a shaft kiln for firing is provided at a desired interval on the downstream side, and a moving grate for adjusting the unburned content is provided on the downstream side. An oxygen gas supply port is installed at the bottom of the grate, and a gas discharge port is installed at the top of the firing shaft kiln, so that the granules fall directly from the moving grate for unburned content adjustment into the firing shaft kiln. That is.

[Effect]

The device of the present invention extracts a part of the exhaust gas discharged from the firing shaft kiln, mixes it with other gases such as cold air and circulating gas, and supplies the gas to the unburned content adjustment moving grate at a temperature of 0.
2. By adjusting the concentration, it is possible to adjust the temperature, unburned content, and surface vitrification rate of the granulated material sent to the shaft kiln for firing.

〔Example〕

An example of the device of the present invention will be explained with reference to the drawings.The device of the present invention includes a moving grate 1 for unburned content adjustment, and a shaft kiln 2 for firing.
, a gas discharge port 3 from the firing shaft kiln, a gas supply port 4 to the moving grate 1 for adjusting unburned matter, a lower air chamber 5, an upper granulated material supply port 6, a moving grate for adjusting unburned matter. It consists of a gas exhaust lower.

The granules made of pulverized coal ash (containing unburned carbon), binder, and water produced in the previous step (described later) are supplied from the granules supply port 6 to the moving grate 1 and moved there. After being preheated and the unburned content adjusted, it is loaded into the shaft kiln 2 for firing. A scraping member 2 is provided at the bottom of the firing shaft kiln 2, and the loaded granules are discharged downward and sent to a subsequent process (described later) through an air chamber 5 and a granule discharge port 8. .

On the other hand, the air is sent to the lower part of the firing shaft kiln 2 by the blower fan 9 through the air chamber 5, and brought into countercurrent contact with the descending granules. Further, most of the exhaust gas from the firing shaft kiln 2 is discharged from the gas discharge port 3 and divided into two directions, one of which is supplied from the regas supply port 4 to the moving grate l for unburned content adjustment. At this time, cold air is mixed to adjust the gas amount, temperature, and o2 degree. In other words, if the temperature and unburned content are too high, the maximum temperature in the firing shaft kiln 1 will exceed the appropriate value, causing granules to fuse together and clogging the furnace, and if the unburned content is too high, the product will deteriorate. This causes problems such as the unburned content in the fuel exceeding 1 part. Also, if it is too low, it will be undercooked! This results in a product with low quality such as low temperature and water absorption rate.

If unburned particles with a high surface vitrification rate are sent to the firing shaft kiln 2, combustion will not proceed much and unburned particles will tend to remain.

It is also possible to adjust the unburned content in the shaft kiln, but in this case, the height of the granules packed will be high and the quality will be impaired due to collapse and abrasion, and the fine powder generated by the abrasion will cause the shaft kiln to may become blocked.

In the present invention, unburned content is adjusted in the moving grate 1, and the granules are moved quietly while being preheated for drying. This prevents collapse and abrasion and also reduces the generation of fine powder. can prevent local clogging.

When operating the apparatus of the present invention, since the combustibles in the granules are adjusted by the moving grade l, the firing shaft kiln 2
In this case, it is only necessary to carry out firing and cooling, and the flow of the granules and gas can be easily made uniform, thereby reducing variations in quality and stabilizing the operation. In addition, the air sent to the moving grate 1 for unburned content adjustment is discharged from the exhaust gas outlet 3, adjusted to the optimum temperature for drying and preheating the granules and adjusting the unburned content, and then supplied through the gas supply port 4. The temperature fluctuation of the granules on the moving grate 1 is small, the moving grate for unburned content adjustment is easy to operate, and the quality of the product (unburned content of 1% or less) is stabilized.

To explain the preparation of the granulated material to be fed to the moving grate for unburned content adjustment, coal ash and binder are fed to the pug mill 14 through quantitative feeders 11 and 13 from the coal storage bin lθ and the binder storage bin 12, respectively. Supplied. Konoya Gumilno 4
is rotated by a drive motor (M) and water (W) is also supplied, where the coal ash, binder, and water are homogeneously stirred and mixed to obtain a wet material. This wet material is supplied to the briquette machine 15, granulated into almond shapes, etc., and sent to the granulated material supply port 6.

Also, the aggregate discharged from the granule discharge port 8 is passed through the screen 20.
The fine powder (MI) from the sieve is discarded or sent back to the coal ash storage bin 10. Further, the gas discharged from the gas discharge lower of the movable grating 1 for unburned content adjustment and the gas discharged from the gas discharge port 3 of the shaft kiln 2 for firing are transferred to the cyclones 17, !, by an induction fan 19. The dust is guided into the air dust collector 18 and removed.

Incidentally, the fine powder (M, ?) discharged from the lower part of the cyclone 17 and the electrostatic precipitator 18 is returned to the coal ash storage bin 11.

Further, although fuel is not required for steady operation of the apparatus of the present invention, a PA furnace 15 is used to increase the temperature of the granules on the moving grate 1 for unburned content adjustment at startup and to ignite the unburned content.
It supplies fuel and air to the gas supply port 4, generates hot air, and supplies it to the gas supply port 4.

〔effect〕

As detailed above, the apparatus of the present invention has the following effects.

(1) It is economical because no fuel is required except for startup.

(2) It is possible to freely control the unburned content in the product, and in particular it can be kept below the JIS standard of 1%.

(3) Product costs are low because equipment costs are low and fuel costs are not required.

(4) Since the amount of fine powder generated in the firing shaft kiln is small, the kiln is not clogged with fine powder.

[Brief explanation of the drawing]

The drawing is a schematic explanatory view showing one example of the concrete aggregate production apparatus of the present invention. l...Moving grate for unburned content adjustment, 2...Shaft kiln for firing, 3...Gas discharge port, 4...Gas supply port, 5...Air chamber, 6...Pelletization material supply port, 7
... Gas outlet, 8... Granule outlet, 9... Blowing fan, 10... Coal ash storage bin, 1... Quantitative feeder, 12... Binder storage bin , 13... quantitative feeder, 14... pug mill, 15... briquette machine, 16... hot air oven, 17... cyclone, 18
...Electric dust collector, 20...Screen, 21...
Scraping member.

Claims (1)

[Claims] In an apparatus for producing aggregate for concrete using coal ash, in which the granules made by granulating fine coal ash containing unburned matter with an appropriate binder are fired in a shaft kiln, the upstream side in the flow direction of the coal ash granules A moving grate for adjusting unburned content is provided downstream of a shaft kiln for firing at desired intervals, and an oxygen gas supply port is provided at the bottom of the moving grate for adjusting unburned content, and a gas discharge port is provided at the top of the shaft kiln for firing. Install them respectively,
A concrete aggregate production apparatus characterized in that granules fall directly from a moving grate for unburned content adjustment into a shaft kiln for firing.