JPH0360010B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-stage incinerator apparatus for incinerating materials to be combusted such as organic sludge discharged in the process of sewage treatment.

[Conventional technology]

Multistage incinerators are used in sewage treatment plants to cool organic sludge discharged during the sewage treatment process. A multi-stage incinerator has multiple stages (5
The sludge is dried by forming shelves of ~12 tiers) and dropping the sludge placed on the top tier to the lower tier.
It is treated by incineration and cooling. The heating of the incinerator is usually done by a burner. Furthermore, the sludge is dropped by a stirring arm attached to a rotating shaft located in the center, and the ash produced by combustion is discharged from the bottom stage.

By the way, in a multistage incinerator, it is required to perform temperature control well so that unburned materials do not remain. Conventionally, temperature control for multi-stage incinerators involves fixing the stage two stages above the stage heated by the burner as the combustion stage, and controlling the amount of fuel supplied to the burner so that the temperature of this combustion stage reaches the set value. . For example, Tokko Akira
As described in Japanese Patent No. 60-26931, the presence or absence of unburned substances is checked based on the temperature difference between the lowermost stage and the upper stage, and the temperature setting value of the combustion stage is adjusted. If there is a temperature difference, it is determined that there is unburned material and the temperature setting value is increased.

[Problem that the invention seeks to solve]

In this way, conventionally, the combustion stage is fixed and the fuel supplied to the burner is controlled so that the fuel stage temperature becomes the set value. However, the combustion stage varies depending on the properties of the sludge (moisture content, organic matter concentration, etc.). When the combustion stage moves to a higher stage than the set combustion stage, the temperature of the actual combustion stage is lower than the temperature set value (optimum combustion temperature) to control the set combustion stage whose temperature has decreased and combustion is about to end to the temperature set value. It would be much more expensive and waste fuel. Even when the actual combustion stage moves below the set combustion stage, the actual combustion stage becomes much higher than the optimum combustion temperature. As mentioned above,
If the temperature is controlled by fixing the combustion stages, the temperature will be higher than necessary and fuel will be wasted, which is not economically advisable.

The present invention has been made in response to the above-mentioned problems, and its purpose is to provide a multi-stage incinerator device that can reduce the amount of fuel used and efficiently perform incineration processing.

[Means for solving problems]

The present invention detects the temperature of each of a plurality of stages defined as combustion stages, and determines the temperature difference between each stage in the vertical direction. The lower stage of the two stages with the largest temperature difference is determined to be the combustion stage, and the amount of fuel supplied to the burner is controlled so that the temperature of this combustion stage becomes the optimum combustion temperature.

[Effect]

The actual combustion stage of the multistage incinerator is detected and the temperature of the actual combustion stage is controlled to the optimum combustion temperature. Therefore,
The amount of fuel used can be reduced and sludge incineration can be performed efficiently without raising the temperature of the actual combustion stage more than necessary.

〔Example〕

FIG. 1 shows an embodiment of the present invention. Figure 1 shows a multistage incinerator with 10 stages.

In FIG. 1, a multistage incinerator 1 has a plurality of shelves 5 in the vertical direction, and a rotating shaft 9 is disposed in the center thereof. The rotating shaft 9 is driven by an electric motor 10. The 1st to 3rd stages from the top in the multistage incinerator 1 are called drying zones, the 4th to 7th stages are called combustion zones, and the 7th to 10th stages are called cooling zones. At the top of the multistage incinerator 1, there is provided an input port 2 into which materials to be burned are input. The sludge is carried in by a belt conveyor (not shown) or the like, and is thrown in from the inlet 2. Further, a gas outlet 4 for discharging exhaust gas is also provided at the top of the incinerator 1. Furthermore, an ash discharge port 3 is provided at the bottom of the incinerator 1. The inside of the incinerator 1 is heated by hot air generated by a burner 12. Burner 12 is installed in the seventh stage. Air is also supplied to the inside of the incinerator 1 by a forced air blower 21. Fuel is supplied to the burner 12 from a fuel storage tank (not shown) via a fuel pump 12, a fuel control valve 13, and a flow meter 14. In addition, the burner 12 is equipped with a forced air blower 1.
Air is also supplied from 5. Although it is desirable to adjust the amount of air supplied to the burner 12, in this embodiment, it is assumed that a constant amount is supplied. The fuel control valve 13 is controlled by a controller 17 to an opening degree such that the temperature of the combustion stage reaches a set value (optimum combustion temperature). A stirring arm 6 is attached to a rotating shaft 9 located at the center of the incinerator 1 at each stage. Temperatures of the 3rd stage which is the drying zone and the 4th to 6th stages which are the combustion stage are determined by temperature detectors 7A to 7, respectively.
Detected at D. The combustion stage determination circuit 18 inputs the temperatures T3 to T6 detected by the temperature detectors 7A to 7D,
The combustion stage is detected as described later, and the detected temperature value of the stage determined to be the combustion stage is provided to the controller 17. Further, the combustion stage determination circuit 18 determines whether or not the incinerator 1 is preparing for combustion (currently being heated), and opens and closes the contacts 8A and 8B. The heating temperature setter 19 applies a temperature setting value in the furnace to be heated via the contact 5A.

Next, the operation will be explained.

The materials to be combusted that are inputted from the input port 2 of the multi-stage incinerator 1 are moved from the circumference to the center on the shelves 5 of each stage by the stirring arm 6 attached to the rotating shaft 9, and alternately from the center to the circumference. The gap 1a between the rotating shaft 9 and the shelf 5
and a hole 1b provided on the outer periphery of the shelf 5 (not shown)
Fall down to the bottom. The objects to be burned are dried and burned as they fall one after another. The combustible material becomes inorganic ash by combustion, and is discharged from the cooled discharge port 3 as it moves to the lower stage. In addition, gas generated by processing of the burnt material is discharged from the exhaust port 4. Normally, exhaust gas is washed with water, acid (sulfuric acid)
After being cleaned by washing, washing with alkali (caustic soda), etc., it is released into the atmosphere.

Now, the combustion stage determination circuit 18 is connected to the temperature detector 7A~
The temperature detection values T3 to T6 detected by 7D are input and the operation is performed as follows. The operation will be explained with reference to the flow diagram shown in FIG.

First, in step S1, it is determined whether the incinerator 1 is preparing for combustion (heating). The determination in step S1 is made based on a signal provided from a separately provided startup control circuit (not shown). If heating is in progress, the process moves to step S2, the contact 8A is closed, and the heating temperature setting value is applied to the control valve 17 from the heating temperature setter 19. Note that the heating temperature setting value is gradually increased in order to reduce the thermal stress of the multistage furnace 1. If heating is in progress, the fifth stage temperature detection value T5 is given to the controller 17 as shown in step S3.
The controller 17 controls the opening degree of the fuel control valve 13 so that the fifth stage temperature T5 becomes the heating temperature set value.

When the preparation for combustion is completed and it is determined in step S4 that it is the initial stage of starting combustion, the temperature fluctuation becomes large because the time since the material to be combusted is introduced is short. In this case, the optimal combustion temperature (for example, 700° C.) is set as the temperature setting value of the controller 17 in step S5. At this time, the temperature T5 of the fifth stage is set using the controller 17.
is given as the temperature detection value.

Next, during the normal operation period, contact 8B is closed and the optimum combustion temperature is applied to controller 17. Then, the process moves to step S6. In step S6, temperature differences ΔT4, ΔT5,
Find ΔT6 using the formula below.

ΔT4=T4−T3 ……(1) ΔT5=T5−T4 ……(2) ΔT6=T6−T5 ……(3) Next, in step S7, the temperature difference ΔT4,
It is determined that the temperature difference ΔT4 is the largest among ΔT5 and ΔT6. When the temperature difference ΔT4 is the maximum, the fourth stage is determined to be the combustion stage, and in step S8, the temperature T4 is set as the combustion stage temperature and is added to the controller 17 as a temperature detection value. The controller 17 increases the opening degree of the fuel control valve 13 to increase the amount of fuel supplied if the combustion stage temperature T4 is lower than the set value, and conversely increases the opening of the fuel control valve 13 if the combustion stage temperature T4 is higher than the set value. reduce the amount of fuel supplied.

Next, when it is determined in step S9 that the temperature difference ΔT6 is the maximum, the temperature T6 is determined to be the combustion stage temperature in step S10. The temperature T6 is added to the controller 17 as a temperature detection value. If both the temperature differences ΔT4 and ΔT6 do not reach the maximum value, the temperature difference ΔT5 is increased in step S11.
is determined to be the maximum value. In this case, the temperature difference ΔT4,
The fifth stage is also set as the combustion stage even in cases other than those normally considered, such as when ΔT5 and ΔT6 are both the same value. Controller 17 uses temperature T5 as the combustion stage temperature.
Enter. This is to prevent unburned materials from being discharged by setting the fifth stage as a combustion stage.

Next, in step S12, the optimum combustion temperature (700° C.) is given to the controller 17 as the temperature setting value, both when the temperature difference ΔT4 is the maximum, and when ΔT6 is the maximum, and in all other cases.

The detection of the combustion stages described above takes into consideration the rapid changes in combustion stages within the multistage incinerator 1, and
The time is measured by a timer (not shown) in S13, and the time starts from 10 minutes.
The above combustion stage detection is performed every 30 minutes. (Step S14) Figure 3 shows the detected values T3~ of temperature detectors 7A~7D.
An example of T6 is shown.

In the example in Figure 3, T3=400℃, T4=500℃, T5=
Calculate the temperature gradient of each stage using 650℃ and T6 = 700℃.

ΔT4=T4−T3=500−400=100(℃) ΔT5=T5−T4=650−540=110(℃) ΔT6=T6−T5=700−650=50(℃) Next, ΔT4, ΔT5, ΔT6 Find the maximum temperature difference. In this case, ΔT5 is the maximum, the fifth stage is determined to be the combustion stage, and the measured value T5 (650° C.) of the fifth stage temperature detector 7C is added to the controller 17.

The combustion stage is detected based on the temperature difference in this way, and the reason is as follows.

In the dry zone of combustion, heat is absorbed by vaporization of moisture in the material to be burned, and the temperature decreases as it goes to the upper stage. At one stage above the combustion stage, the material to be burned is dried, moisture in the material to be burned is vaporized, and heat is absorbed by absorbing the heat of vaporization. On the other hand, in the combustion stage, heat generation occurs due to combustion of the materials to be combusted, and therefore, the temperature difference between the combustion stage and the stage one step above the combustion stage is the largest.

During the heating period of the multistage incinerator 1 and the combustion start period of the multistage incinerator, the temperature detection value of the fifth stage, which is considered to be the normal combustion stage, is outputted to the controller 17 as the temperature detection value T5. Since there is a risk of unburned matter remaining in the ash, the combustion zone is widened by setting the fifth stage of the burner 11 above the sixth stage, which is most effective, as the combustion stage. The controller 17 controls the fuel control valve 13 based on the temperature detection value input from the combustion stage determination circuit 18.
By controlling the temperature of the multistage incinerator 1, the temperature of the multistage incinerator 1 is controlled. The temperature setting value of the controller 17 is set to the optimum combustion temperature (700° C.), making it possible to control the optimum temperature even when the combustion stage changes.

Temperature control is performed as described above.
Strict combustion control can be performed in multi-stage incinerators where the atmosphere inside the furnace fluctuates depending on the properties of combustible materials, input amount, and combustion conditions. Since there is no need to set the temperature of the controller 17 to a high value to ensure a high safety factor in order to deal with fluctuations in the properties of combustible materials as in the past, it is possible to supply excess fuel and incinerate it. It is no longer necessary to do so, and this is extremely preferable in terms of energy and resource conservation. . The energy saving effect is
Although it varies depending on the properties of the combustible material and the amount input, actual measurements showed that fuel savings were approximately 10 to 15%.

〔Effect of the invention〕

As explained above, according to the present invention, the temperature setting value of the temperature setting controller that controls the temperature of the combustion stage can be optimized by detecting the combustion stage of a multistage incinerator and controlling the temperature of the combustion stage. Effective heating control can be carried out by setting the combustion temperature. Therefore, since the heating burner can be operated efficiently, there is an effect that the amount of fuel used can be effectively incinerated.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is an operation flow diagram of a combustion stage determination circuit, and FIG. 3 is a temperature distribution characteristic diagram of a multistage incinerator. 1...Multi-stage incinerator, 2...Combustibles input port, 3...
...Ash discharge port, 4...Exhaust gas discharge port, 7A to 7D
... Temperature detector, 11 ... Burner, 13 ... Fuel control valve, 17 ... Controller, 18 ... Combustion stage determination circuit.

Claims (1)

[Claims] 1. A multi-stage incinerator that has multiple shelves in the vertical direction, and in which sludge introduced into the top stage is sequentially dropped to the lower stage for incineration, a burner that heats the multi-stage incinerator, and a fuel that is supplied to the burner. a fuel supply means for
a fuel control means for controlling the amount of fuel supplied from the fuel supply means to the burner; a temperature detection means for detecting the temperature of each of a plurality of stages defined as combustion stages of the multistage incinerator; and detection by the temperature detection means. Find the temperature difference for each stage in the vertical direction of the multiple stages,
combustion stage determining means for determining the lower stage of the two stages having the largest temperature difference as the combustion stage, and the fuel control means inputs a temperature detection value of the stage determined to be the combustion stage by the combustion stage determining means. A multi-stage incinerator apparatus, characterized in that the amount of fuel supplied to the burner is controlled so that the combustion stage reaches a set combustion temperature.