JPH0360011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multistage 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 incinerate 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. Heating of incinerators is usually done by burners. 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 of a multistage incinerator involves fixing a stage above the stage heated by a burner as a combustion stage, and controlling the amount of fuel supplied to the burner so that the temperature of this combustion stage becomes a 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]

Incidentally, the combustion stage varies depending on the properties of the sludge (moisture content, organic matter concentration, etc.). When the combustion stage moves above the set combustion stage, the temperature of the actual combustion stage is much higher than the temperature set value (optimum combustion temperature) in order to control the set combustion stage whose temperature has decreased and combustion is about to end to the temperature set value. This increases the fuel consumption and wastes 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 described above, when the actual combustion stage shifts to a stage other than the set combustion stage, the temperature of the actual combustion stage is made higher than necessary, which wastes fuel, 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 provides an exhaust valve in one or several stages above the set combustion stage, detects the actual combustion stage, and operates the exhaust valve when the actual combustion stage is above the set combustion stage.

[Effect]

When the actual combustion stage moves to a higher stage than the set combustion stage, the exhaust valve is opened to release heat and the actual combustion stage moves to the lower stage, so that the set combustion stage always becomes the actual combustion stage. Since the temperature of the set combustion stage is controlled to the optimum combustion temperature, 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. In this embodiment, the sixth stage will be described as a set combustion stage. The top of the multistage incinerator 1 is provided with an inlet 2 into which sludge (combustible material) is introduced. 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. Incinerator 1
Exhaust holes 22a, 22b are provided on the side walls of the 5th and 6th tiers.
are bored, and exhaust valves (electrically operated valves) 23A, 23B are connected to these exhaust holes 22a, 22b via piping. The outlet sides of the exhaust valves 23A and 23B are connected to piping connected to the gas exhaust port 4. Although the piping is usually provided with an induced fan, illustration thereof is omitted. Exhaust valve 23A, 23B
is controlled to be turned on or off by a valve drive circuit 24, which will be described later. The inside of the incinerator 1 is heated by hot air generated by a burner 12. The burner 12 is installed in the seventh stage. A forced air blower 2 is installed inside the incinerator 1.
Air is also supplied by 1. 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.
Additionally, air is also supplied to the burner 12 from a forced air blower 15 . 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 the controller 17 to an opening degree such that the temperature of the set combustion stage becomes the 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. The temperatures of the third drying zone and the fourth to sixth combustion zones are detected by temperature detectors 7A to 7D, respectively. The combustion stage determination circuit 18 uses the temperature T3 detected by the temperature detectors 7A to 7D.
~T6 is input, and the actual combustion stage is detected as described later, and the temperature detection value T6 of the set combustion stage (sixth stage) is provided to the controller 17. Further, the combustion stage determination circuit 18 not only provides information on which stage the detected actual combustion stage is to the valve drive circuit 24, but also determines whether or not the incinerator 1 is preparing for combustion (heating). Opens and closes. The combustion stage determination circuit 18 applies the fifth stage temperature detection value T5 to the controller 17 during combustion preparation (during heating). The heating temperature setter 19 applies the furnace temperature set value for heating via the contact 8A.

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
Then, it falls to the gap 1b between the shelf 5 and the outer peripheral side wall or to the lower stage. The objects to be burned are dried and burned as they fall one after another. The combustible material becomes inorganic ash by combustion, and as it moves to the lower stage, it is cooled and discharged from the discharge port 3. In addition, gas generated by processing of the burnt material is discharged from the exhaust port 4. Typically, exhaust gas is washed with water, acid (sulfuric acid), alkali (caustic soda), etc., and then 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 judgment in step S1 is made by a separately provided startup control circuit (not shown).
Judgment is made based on the signal given from If heating is in progress, proceed to step S2 and close contact 8A.
A heating temperature set value is applied from the heating temperature setter 19 to the controller 17. In addition, the heating temperature setting value is multistage furnace 1.
Increase gradually to reduce thermal stress. 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 as well, the temperature T5 of the fifth stage is given to the controller 17 as a 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,
Calculate ΔT6 from 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 whether 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 actual combustion stage, and in step S8, the temperature T4 is added as the actual combustion stage temperature to the controller 17 as a detected temperature value. If the combustion stage temperature T4 is smaller than the set value, the controller 17 increases the opening degree of the fuel control valve 13 to increase the amount of fuel supplied;
4 is larger than the set value, the opening degree of the fuel control valve 13 is reduced to reduce the amount of fuel supplied. Normally, the combustion stage temperature T4 becomes higher than the set value, so the amount of fuel supplied is reduced. When the process moves from step S8 to step S9, a command to open the exhaust valve 23A is given to the valve drive circuit 24 in step S9. The valve drive circuit 24 fully opens the exhaust valve 23A. When the exhaust valve 23A is fully opened, the heat of the fourth combustion stage is radiated to the atmosphere. 4
When the heat in the stages is dissipated, drying in the drying zones of the first to third stages is hindered, so the combustion stage gradually decreases and moves to the fifth stage. When the combustion stage shifts to the fifth stage, it is determined in step S10 that the temperature difference ΔT5 is the maximum. In step S11, the temperature T5 is determined to be the combustion stage temperature, and the temperature T6 is added to the controller 17 as a detected temperature value. The controller 17 controls the fuel control valve 13 so that the fifth stage temperature T5 becomes the set value. step
In S12, a command to close the exhaust valve 23A and a command to open the exhaust valve 23B is given to the valve drive circuit 24. The valve drive circuit 24 fully closes the exhaust valve 23A and at the same time fully opens the exhaust valve 23B. When the exhaust valve 23B is fully opened, the heat of the fifth stage is dissipated to the atmosphere, so
The drying of the first to fourth drying stages is hindered. Therefore, the combustion stage gradually decreases, and the sixth stage becomes the actual combustion stage. If both the temperature differences ΔT4 and ΔT5 do not reach their maximum values, the sixth stage, which is the set combustion stage, is determined to be the actual combustion stage, and the temperature T6 is inputted to the controller 17 as the actual combustion stage temperature in step S13. The controller 17 controls the fuel control valve 13 so that the temperature T6 of the sixth stage, which is the set combustion stage, becomes the set value. In step S14, a command to close the exhaust valves 23A and 23B is given to the valve drive circuit 24. The valve drive circuit 24 fully closes the exhaust valves 23A and 23B. Although the exhaust valve 23A is already fully closed, perform a reconfirmation operation. Normally, the exhaust valves 23A and 23B are both fully closed, and the combustion process is performed with the set combustion stage, which is the 6th stage, being the actual combustion stage. The reason why the sixth stage of the multistage incinerator 1 is the set combustion stage is that the burner 11 is installed in the seventh stage, and the distance between the burner 11 and the actual combustion stage is shortened to fully demonstrate the heating effect of the burner. This is also to prevent unburned materials from being discharged. At step S15, 4~
When any of the sixth stages is the actual combustion stage, the optimum combustion temperature (700°C) is given to the controller 17 as the temperature setting value. The above determination of the actual combustion stage is performed by taking into consideration that the combustion stage changes slowly in the multistage incinerator 1, and is timed by a timer (not shown) in step S16.
The actual combustion stage is detected every 10 to 15 minutes (step S17).

Now, in the embodiment shown in FIG. 1, the actual combustion stage is detected based on the temperature difference. This will be explained in detail.

Fig. 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℃, T
Calculate the temperature gradient of each stage using T5=650°C and T6=700°C.

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 and 5
The stage is determined to be the combustion stage, and the fifth stage temperature sensor 7C
The measured value T5 (650°C) 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 drying zone of the incinerator, heat is absorbed by the vaporization of moisture in the materials to be burned, and the temperature decreases as the temperature goes higher. 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.

Note that during the heating period of the multistage incinerator 1 and the combustion start period of the multistage incinerator 1, 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 the most effective, as the combustion stage. The controller 17 controls the temperature of the multistage incinerator 1 by controlling the fuel control valve 13 based on the temperature detection value input from the combustion stage determination circuit 18. 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.
The most effective set combustion stage of the burner is set to be the actual combustion stage. For this reason, there is no need to set the temperature of the controller 17 to a high value with a high safety factor in order to deal with changes in the properties of combustible materials, as in the past, and it is not necessary to supply excessive fuel. There is no need for incineration, which saves energy.
This is extremely preferable in terms of resource conservation. The energy saving effect varies depending on the properties of the combustible material and the amount input, but actual measurements showed that fuel savings were approximately 10 to 15%.

〔Effect of the invention〕

As explained above, according to the present invention, the actual combustion stage of the multistage incinerator is detected so that the set combustion stage becomes the actual combustion stage. Therefore, since the heating burner can be operated efficiently, there is an effect that the amount of fuel used can be effectively incinerated.

In the above-described embodiment, the actual combustion stage is detected based on the temperature difference, but the same method can be performed even if the stage with the highest temperature is determined to be the actual combustion stage. In addition, even when a combustion stage other than the set combustion stage becomes the actual combustion stage, the actual combustion stage is set to the optimal combustion temperature, but if the transition from the actual combustion stage occurs quickly, the set combustion stage is always set to the optimal combustion temperature. Of course, the combustion temperature may be controlled. Furthermore, the exhaust valve may be controlled in opening degree instead of on/off control.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The figure is an operation flow diagram of the combustion stage determination circuit, and FIG. 3 is a temperature distribution characteristic diagram of the 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, 23A, 23B ... Exhaust valve, 24 ... Valve drive circuit.

Claims (1)

[Scope of Claims] 1. A multi-stage incinerator that has a plurality of shelves in the vertical direction, and in which materials to be combusted placed on the top stage are sequentially dropped to the lower stage for incineration, and a burner that heats the multi-stage incinerator. a fuel supply means for supplying fuel to the burner; and a fuel for controlling the amount of fuel supplied to the burner so that a set combustion stage determined as a combustion stage among the plurality of stages of the multistage incinerator has a set combustion temperature. a control means, a temperature detection means for detecting the temperature of each of a plurality of stages defined as a combustion zone of the multistage incinerator, an exhaust means provided at a stage above a set combustion stage of the multistage incinerator, and the temperature detection means. A multi-stage incinerator device comprising: a combustion stage determining means for determining an actual combustion stage based on the temperature of each stage detected; and an exhaust control means for operating the exhaust means when the actual combustion stage is higher than the set combustion stage. . 2. In claim 1, the combustion stage determining means determines the temperature difference for each stage in the vertical direction of the plurality of stages detected by the temperature detecting means, and selects the lower stage of the two stages having the largest temperature difference. A multistage incinerator device characterized in that the stage is determined to be an actual combustion stage.