JPS6157963B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a fluidized bed type incinerator that detects the temperature in the combustion zone, transmits this to a material charging device to adjust the amount of material to be incinerated, and controls the temperature in the combustion zone. The aim is to maintain a constant temperature within the combustion chamber and maintain stable combustion conditions.

A fluidized bed incinerator is a rigid incinerator that is suitable for incinerating materials that are approximately uniform in size.
Air is blown up from the bottom of the furnace to suspend the materials to be incinerated inside the furnace, forming a fluidized bed, thereby increasing the effect of contact between the materials to be incinerated and the air.

Before explaining the present invention, an outline of a fluidized bed incinerator will be explained.

In Fig. 1, reference numeral 1 denotes the incinerator body, whose base gradually tapers downward into a so-called inverted truncated conical shape, and a ventilation plate 2 is placed over its bottom to form a combustion chamber. do. 3 is an exhaust port, and 4 is an air supply duct, which is connected to a blower 5 (not shown) to supply combustion air into the furnace. Note that a preheating furnace is installed between the air duct 4 and the blower 5 so that hot air is sent when the furnace is started. Reference numeral 6 is a charging duct for charging the materials to be incinerated into the furnace. This input duct 6 is equipped with an appropriate feeding device capable of continuously feeding the materials to be incinerated into the furnace, and the figure shows an example using a screw conveyor. A drive device (not shown) is connected to this screw conveyor to operate it. Also, 8a,
Reference numerals 8b and 8c are furnace thermometers, which are installed at appropriate points within the combustion zone. It goes without saying that this incinerator is equipped with a residue outlet, a viewing window, an ignition port, a combustion gas outlet for sampling, and the like. As mentioned above, this type of incinerator burns the material to be incinerated (hereinafter referred to as retained incineration material) placed in the furnace in a suspended state, so there is no chance of the material coming into contact with the air. Moreover, the newly inputted materials to be incinerated and the accumulated materials to be incinerated are sufficiently mixed, and the energy exchange for sustaining combustion is also good, resulting in a fast incineration speed. However, the reaction is fast, which causes large turbulence in combustion, resulting in clinker generation and fire breakouts. Furthermore, the ash produced by combustion is automatically separated and discharged from the exhaust port 3, etc.
Although it is suitable for continuous incineration, it is necessary to maintain the amount of accumulated incineration within a certain range, and it is necessary to keep the amount of accumulated incineration within a certain range or to temporarily increase it. If you do so, there is a drawback that it will catch fire.

Therefore, when operating this type of incinerator, care must be taken not to disturb the energy exchange needed to sustain combustion, and the amount of accumulated incineration material must be constantly detected.
It is essential to feed back this information to the drive device, control the amount of material to be incinerated, and maintain a constant combustion state. Attempts have been made in the past, but none of the methods have been able to produce a satisfactory effect. For example, a thermometer is inserted into one point in the furnace to measure the temperature at this point and send it to the control device, and when the temperature rises above a preset temperature range, it is determined that the amount of material to be incinerated is excessive. There is a method of reducing the input amount and increasing the input amount when the measured temperature falls, assuming that the amount of incineration material is too small.

However, in cases like this incinerator, the temperature at the measurement location changes due to changes in the properties of the incinerated material, so the temperature change at this point, the amount of energy exchanged to sustain combustion, and the amount of accumulated incinerated material are Changes do not necessarily correspond. Therefore, the amount of material to be incinerated cannot be properly controlled, and clinker often forms in the combustion zone or fire breaks out. (In particular, clinker can cause adhesion to the furnace wall and stop fluidization,
The main reasons for this are as follows. That is, as shown in Table 1, the temperature distribution within the furnace has a maximum point within the combustion zone, and becomes slightly lower toward the top. The position of this maximum point varies depending on the properties of the material to be incinerated and the amount of accumulated incineration material. For example, when the amount of accumulated incineration material increases or the moisture content of the material to be incinerated increases, the position of this maximum point changes upward. Move to.

Table 1 shows operating status (proper combustion status)
The amount of incinerated material in the furnace and the temperature distribution curve inside the furnace are shown. The curve in the table shows the temperature distribution curve when the amount of material to be incinerated is large, and the curve and the curve show the temperature distribution curve when the amount is even smaller.

As shown in the table, the maximum temperature inside the furnace rises and falls as the amount of retained incineration material increases or decreases. Furthermore, as mentioned above, when the amount of accumulated incineration material is within the range that allows normal combustion to continue, the temperature in the combustion zone will remain almost constant in the upper part even if the amount of accumulated incineration material fluctuates. , the middle and lower parts rise and fall significantly as the amount changes.

For this reason, t ₁ , which is the upper part of the combustion zone,
When a thermometer is installed at the point, it is not possible to detect an increase or decrease in the accumulated incineration material depending on the temperature.

Furthermore, when the thermometer is installed at the position _t2 , the measured temperature decreases as the amount of retained incineration material increases, and conversely, the measured temperature increases as the amount decreases. From this, when there is a large amount of retained incineration material, the amount of incinerated material input must be increased, resulting in an excessive amount of retained incineration material, and when there is little retained incineration material, the amount of incinerated material input will be reduced. As a result, the amount of accumulated incineration material becomes too small to continue stable combustion, and clinker suddenly forms or the fire breaks out.

Table 2 shows the change in the temperature distribution curve in the furnace immediately after the input of the material to be incinerated when the input amount of the material to be incinerated is suddenly increased.
Since the temperature of the newly inputted material to be incinerated is low, the temperature in the incineration zone is temporarily suppressed and changes from the curve to ''. This tendency is more pronounced as the moisture content of the material to be incinerated is higher.

In this case as well, even though the amount of accumulated incinerator in the furnace increases, the measured temperature decreases, so the amount of input has to be further increased, which causes the temperature inside the furnace to further decrease and eventually causes the fire to break out. It will become.

The present invention solves the above-mentioned conventional drawbacks and makes it possible to reliably control the amount of material to be incinerated.The main point of this invention is to measure the temperature at several points in the combustion zone. By doing so, it is possible to eliminate changes in the amount of incineration material accumulated in the furnace and the apparent reversal phenomenon of the temperature in the furnace in response to the change.

In other words, as illustrated in Table 1, when the incinerator is operating under proper conditions, the maximum temperature points a, b, and c in the combustion zone change as the amount of accumulated incineration material increases or decreases. However, the temperature is unique depending on the type and shape of the material to be incinerated, the amount of air blown, etc., and exhibits a substantially constant value.

For this reason, the present invention measures the temperature at two or more points within the range where the maximum point of temperature can change when operating under proper conditions, and Therefore, the amount of waste to be incinerated accumulated in the furnace is sensed, and this is fed back to the drive device to control the amount of waste to be incinerated.

The present invention will be specifically described below based on examples.

Example 1 The temperature at three points ta, tb, and tc within the range where the temperature maximum point within the combustion zone can change when the incinerator is operating under proper conditions was measured, and on the other hand, the temperature at these points was measured. An appropriate temperature is set, the difference between the highest temperature of each measured temperature and the set temperature at that point is detected, and this is fed back to the drive device.

Table 3 shows the displacement trajectory of the maximum temperature, and Table 4 shows the incinerator control block diagram.

The temperature detectors in the table are high temperature thermometers 8a, 8b, 8c.
It measures the temperature at points ta, tb, and tc of the incinerator. The maximum value detection circuit converts the temperatures measured by the respective thermometers ta, tb, and tc into voltages and selectively extracts only the one with the highest voltage. The input system is an incineration material input device consisting of the already mentioned feeding device such as the screw conveyor and a drive device for driving this, and the controller is configured to input information on the maximum temperature sent through the maximum value detection circuit. The system compares the set temperature with a preset temperature, detects the difference, and transmits this to the drive device, which controls the rotation speed of the drive device and adjusts the amount of material to be incinerated into the incinerator. It is something. It is assumed that the charging device is controlled so that the charging amount does not change for a period of ten to several tens of seconds immediately after the charging amount changes. This is to avoid reacting to a temporary drop in the temperature of the combustion zone immediately after the input amount is increased, as described in Table 2.

Next, the operating state of the incinerator will be explained.

Suppose that the incinerator is operating under proper conditions and that the maximum temperature is at point ta. In this state, if the input speed of the material to be incinerated is lower than the incineration rate, the amount of the material to be incinerated in the furnace will gradually decrease. Correspondingly, the maximum point descends along the set value curve S shown in Table 3 and shifts from ta to tc. Since the maximum value detection circuit instructs the controller about the temperature of the point that always shows the highest temperature among the measurement points ta, tb, and tc, the maximum point is in this way set value curve S (approximately constant temperature). The controller is instructed that the inside of the furnace continues to operate in a proper state while moving along the line (indicating that there is a certain condition), so the charging system continues to operate in a steady state.

In this state, when the amount of incinerated matter remaining in the furnace further decreases, the maximum temperature falls below the temperature indicated by the set value curve S. This is then transmitted to the controller, and further transmitted to the input system to increase the input amount of the material to be incinerated. Similarly, when the maximum temperature rises above the temperature shown by the set value curve S, the amount of input is reduced, and in this way the temperature inside the furnace is adjusted to the maximum temperature at points ta, tb, and tc. In this case, as mentioned above, even if the temperature inside the furnace temporarily decreases for several tens of seconds immediately after the input amount changes, In response to this, it goes without saying that the structure is designed so as not to increase the amount of input.

Next, we will show an example in which the amount of material to be incinerated is more strictly controlled.

Example 2 The incinerator control block diagram is shown in Table 5. The maximum value selection circuit in the table detects the point indicating the maximum temperature among the three measurement points and transmits this to the controller.The blower system consists of a blower and a blower air heater. It is something that Next, the operating state will be explained. The incinerator is assumed to be operating properly when this point is the maximum temperature and the set temperature is based on point tb.

The amount of accumulated incineration material in the furnace gradually decreases until it reaches the maximum point.
When transitioning from tb to tc, the input amount of incinerated materials is increased, and when transitioning from tb to ta, it is decreased. In this way, combustion is controlled by keeping the amount of accumulated incineration material in the furnace constant, but when the temperature inside the furnace is outside the upper limit sh and lower limit sl of the set temperature range, the blower system is controlled. It is better to control this. In other words, the maximum temperature is between tb and ta, and the furnace temperature is above the upper limit of the set temperature sh.
When the furnace temperature exceeds the lower limit SL, it is best to notify the ventilation system to that effect and reduce the amount of air blown to suppress combustion.Also, when the temperature inside the furnace falls below the lower limit SL, it is recommended to notify the ventilation system and reduce the amount of air blown. It is better to heat the air. The reason why the temperature inside the furnace decreases despite the large amount of retained incineration material is that materials with low exothermic temperatures and materials with high moisture content are mixed into the material to be incinerated.
Conversely, when the maximum temperature is between tb and tc and exceeds the upper limit sh, it is better to increase the air flow rate. This rise in temperature occurs when materials with a particularly high exothermic temperature are mixed into the material to be incinerated. It is desirable to lower the temperature of the flame and, at the same time, reduce the chances of the particles of the incinerated material and ash particles joining together.

As detailed above, the present invention provides that the temperature within the combustion zone has a maximum point, and that the maximum point rises and falls as the upper surface of the combustion zone rises and falls, or in other words, as the amount of material to be incinerated increases and decreases. However, taking advantage of the fact that the temperature shows a nearly constant value in a steady state, we insert thermometers at several points in the combustion zone and measure the temperature at those points. The amount of material to be incinerated and the amount of air blown are adjusted according to changes in the maximum temperature of the furnace, thereby controlling the temperature inside the furnace.The mechanism is simple and the temperature can be controlled reliably. It has the advantage of being able to

[Brief explanation of the drawing]

The figure is a vertical sectional view schematically showing an example of a fluidized bed incinerator to which the present invention is applied. 1; Incinerator main body, 2; Ventilation panel, 3; Exhaust port,
4; Air supply duct, 6; Input duct, 8; Thermometer.

Claims (1)

[Claims] 1. In the combustion zone when the incinerator is operating properly, measure the temperature at several points above and below within the range where the maximum temperature inside the incinerator can vary, and compare the highest temperature of these with the preset temperature. In a fluidized bed incinerator, the temperature inside the furnace is automatically controlled by detecting the difference between the set temperature and the set temperature, and adjusting the amount of material to be incinerated according to the difference. Temperature control method.