JPS5925746B2 - Continuous granulation and sintering method for fly attachment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously granulating and sintering fly ash. This relates to a method for adjusting the particle size of raw pellets by feeding it back to a granulator.

Exhaust gas generated from various boilers, heating furnaces, incinerators, etc. contains a large amount of fine dust (fly ash), but as energy sources change (accompanied by a switch to coal-fired combustion), It is thought that the amount of fly ash generated will increase dramatically.

As a technique for effectively utilizing such fly ash, for example, the basic process of granulation and sintering as shown in FIG. 1 is known.

In other words, this process involves adding combustible carbon material (fine powder of coal or coke) as necessary to fly ash, which originally contains some unburned carbon, and then adding water as a binder and kneading it. After granulating this to obtain green pellets, they are charged onto a moving grate, transported, and sintered on the moving trajectory to become an artificial lightweight aggregate. The details are as follows.

In Figure 1, a rotary inclined dish type granulator (disk type pelletizer) 15 is used as the granulator, and the raw material powder is continuously fed into this while adding water and granulated as it is. be.

The granulated raw pellets 1 are normally charged into the hopper 16 either directly or after being stored in a suitable storage container.

Then, the product aggregate 2 is first charged onto the movable grate B rotating in the direction of the arrow to form a bedding, and then the green pellets 1 are charged onto it. Adjusted to height.

The thus formed moving sintered layer is sequentially transferred from left to right in the drawing, passes through a drying and preheating furnace 4, an ignition furnace 5, and a sintering/retention furnace 6 to undergo sintering, and is then transferred to a cooling zone 7. At this point, it is sufficiently cooled and becomes the product aggregate.

A plurality of wind boxes 8 are arranged under the upper grate 3 that supports the moving sintered layer in the movement locus direction, and the lower side of the box 8 and the narrow spool portion are shown in the sectional view taken along the line nn. As shown in FIG. 2, the return side (lower side) is displaced so as to avoid the grate, and opens into the exhaust duct 9.

The duct 9 is evacuated by a blower 10, and the suction airflow forms a suction airflow that passes from top to bottom within the moving sintered layer.

It is desirable to introduce high-temperature air into each furnace 4°5.6, and preheated air is introduced along the arrows, respectively.
It is also possible to extinguish a part of the suctioned exhaust gas, especially the high-temperature exhaust gas sucked from the high-temperature section at the lower part of the sintering/retention furnace, through all or part of the preheated air.

Reference numeral 11 denotes a dust chute, and a line may be installed in which pieces of green pellets etc. that have fallen into the exhaust duct 9 are collected by a conveyor 12 and re-granulated by a granulator 15.

Is the product obtained by such continuous granulation and sintering useful as an artificial lightweight aggregate? Various standards have been established for artificial lightweight aggregate, and one of these standards is particle size distribution. There is.

For example, for coarse aggregate with a diameter of 5 to 20 mm, the weight percentage of the material passing through each sieve is ioo% for a 25 mm sieve (nominal size, the same applies hereinafter), 100 to 90% for a 20 mm sieve, and 100 to 90% for a 20 mm sieve.
65-20% with a 0-hole sieve, 10-0% with a 5mm sieve
It is stipulated that

It is not always easy to obtain such a particle size distribution in continuously granulated and sintered crystals, and if strict quality control is not carried out, a large amount of aggregate that does not meet the above specifications will be produced. Sometimes.

From this point of view, there has been a demand for the development of a system that can appropriately control and modify the particle size of aggregate, and as a result of various studies, the present invention has been completed.

That is, the key point of the particle size control correction according to the present invention is that the particle size of the raw pellets charged onto the moving grate is detected by measuring the suction pressure in the wind box provided at the bottom of the moving grate. The disadvantage is that the detected value is compared with a predetermined standard value to determine the difference, and a command signal based on the result is input to the control system of the granulator to adjust the particle size of the raw pellets. exists in

That is, the particle size distribution of the product aggregate is of course substantially regulated by the particle size distribution at the raw pellet stage.

Therefore, in order to obtain an appropriate particle size distribution, it is necessary to correct and manage the particle size of raw pellets.

However, in the above method of continuously producing green pellets and charging them onto a moving grate, it is extremely difficult to directly monitor and adjust the particle size distribution at the granulator stage.

Therefore, it is necessary to measure the particle size distribution at an appropriate stage after the granulation process, but since the particle size distribution is statistical data in the first place, it is necessary to measure it by understanding a certain population.

Based on such L rollers, we thought that it would be easier to measure the particle size distribution by targeting the product aggregate after sintering.

However, it seems that defective products were discovered after sintering was completed.
Even if this is fed back to the granulator as soon as possible to control the particle size, it will not work for a while because a large amount of defective pellets are already charged on the moving grate. The continued production of defective products has to be ignored, which is extremely inconvenient.

Based on this, the present inventors believed that it was necessary to understand the particle size distribution at an early stage, and by measuring the suction pressure in the wind box installed at the bottom of the moving grate, The basic idea was reached to detect the particle size of the pellets at the charging position on the grid, and to compare this detected value with a set standard value to issue commands to the granulator.

This method will be described in more detail below.

In the present invention, as a specific means for detecting the particle size distribution, a suction pressure measurement method is employed in a wind box provided below the green pellet charging layer, that is, below the movable grate at the green pellet charging position.

In other words, as described above, sintering is performed by creating a suction airflow that penetrates the moving sintered layer from top to bottom, but the suction airflow depends on the degree of clogging (density) of the raw pellets that make up the sintered layer. The ease of formation changes.

This "ease of formation" can be detected, for example, as the suction pressure at one point 13 in the wind box 8 in FIG. 2, and if the charging height is kept constant as described above,
The higher the filling (higher density), the higher the suction pressure.

Since the green pellets are charged at a higher density as their particle size becomes smaller, the particle size of the green pellets can be detected almost accurately by suction pressure.

The particle size of the charged pellets detected by the suction pressure measurement method in this manner is compared with a standard value set or measured in advance for a standard particle size distribution, and the difference from the standard value is calculated.

If this difference is outside the allowable range, it means that the particle size distribution of the raw pellets is not appropriate, so a correction command is issued to the control unit of the granulator, and the granulation conditions are adjusted. .

There are no particular restrictions on the granulator used in the present invention, and a rolling granulator, an extrusion granulator, etc. may be used arbitrarily, or the former is suitable for fly ash granulation. I will explain it to you.

Rotating cylindrical granulators and rotating inclined dish granulators are known as transfer granulators, but when the former granulator is used, it affects the particle size of the raw pellets produced. Factors include the rotational speed of the rotating cylinder, the amount of raw ore supplied, and the amount of water added.

In addition to the above-mentioned three factors, factors that influence the particle size of the raw pellets when using the latter rotary tilting dish type granulator include the tilt angle of the rotary tilter.

Since these factors are all external factors, they can be controlled, and each can be considered as a particle size distribution control factor.

Therefore, in the present invention, a command issued based on the above calculation is introduced into the control system of the granulator, and adjustment is made so as to return to an appropriate particle size distribution by appropriately manipulating one or more control factors.

Since the present invention is configured as described above, fluctuations in particle size distribution in raw pellet granulation can be detected as quickly as possible,
Moreover, the granulator can be quickly controlled based on the detection.

As a result, the particle size distribution of the sintered artificial lightweight aggregate can always be maintained in an optimal state, and it has also become possible to prevent sintering abnormalities that may be caused by abnormal particle size.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the sintering process, and FIG. 2 is a sectional view taken along the line ■-■. 1... Raw pellets, 3... Moving grate, 8... Wind box, 15...
Granulation machine.

Claims (1)

[Claims] 1. A combustible carbon material and a binder are added and kneaded to fly ash generated from a coal-fired boiler, etc., and the raw pellets obtained by continuously granulating this in a granulator are sintered. Zeta hit, moving grate that continuously charges onto the moving grate of a sintering furnace to form a moving sintered layer of a constant height, and sinters continuously while sucking the gas from below the sintered layer above. The particle size of the pellet is detected by measuring the suction pressure in the wind box installed at the bottom of the pellet, and this detected value is compared with a predetermined standard term to calculate the difference. A method for continuous granulation and sintering of fly ash, characterized in that the particle size of green pellets is adjusted by introducing a command signal based on the control system of the granulator into the control system of the granulator. 2. In claim 1, a rotating cylindrical granulator is used as the granulator, and one or more control factors selected from the rotational speed of the rotating cylinder, the amount of raw material supplied, and the amount of water added are controlled. Continuous granulation and sintering method. 3. In claim 1, a rotary tilting plate type granulator is used as the granulator, and one or more of the rotational speed of the rotary tilter, the tilt angle, the amount of raw material supplied, and the amount of water added is used as the granulator. Continuous granulation and sintering method to control control factors.