JP2001074222A - Method and apparatus for controlling temperature in fluidized bed incinerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To separately control temperature of a freeboard independent of the temperature of a sand layer. SOLUTION: An incinerator for incinerating sewage sludge comprises combustion regions, i.e., a sand layer portion and a freeboard portion 3 which are formed in a furnace body 1. Specifically, a sand layer upper burner 31 which is arranged at an upper portion of the sand layer portion is operated to control the temperature of the freeboard, and a sand layer lower burner 32 which is arranged at a lower portion of the sand layer portion is operated to control the temperature of the sand layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling the temperature inside a fluidized bed incinerator for incinerating sewage sludge.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional fluidized bed incinerator. In FIG. 4, the fluidized bed incinerator is
A sand layer portion 2 and a free board portion 3 are formed inside the furnace body 1 as a combustion area, and a heat-resistant and abrasion-resistant special brick and casters are lined on the inner surface of the furnace body 1, and the amount of heat radiation is minimized outside the furnace body 1. Insulation to suppress is arranged.

The sand layer 2 has a plurality of distribution pipes 4a arranged at a lower portion thereof. Each of the distribution pipes 4a is connected to a blower 5 via a flow air header pipe 4, and distributes the flow air supplied by the blower 5. The fluidized sand 6 spouted from the pipe 4a to the sand layer portion 2 and retained in the lower region is maintained in a fluidized state. The sand layer section 2 is provided with a cake charging machine 7 at an upper portion, and the sludge dewatered cake is charged into the upper region by the cake charging machine 7. The cake feeding machine 7 includes a screw type or a spreader type.

The furnace body 1 is equipped with a starting burner 8 provided above the sand layer 2 and a sand upper burner 9a and a sand lower burner 9b provided in the flowing sand of the sand layer 2 as a combustion device. A tapered discharge unit 10 is provided at the lower end of the furnace body 1, and a sand conveyor 11 for carrying out the fluidized sand 6 is provided below the discharge unit 10. Above the sand layer 2 is provided a sand inlet 12 into which the fluidized sand 6 is injected.

In this configuration, the flowing air supplied by the blower 5 is heated to 550-650 ° C. by the combustion exhaust gas.
And is blown into each dispersion pipe 4a from the flowing air header pipe 4. The fluidizing air is uniformly jetted from each of the dispersion pipes 4a to the sand layer portion 2, and the fluidized sand 6 is vigorously stirred and mixed to be heated to 700 to 750 ° C. In this state, the sludge dewatered cake is supplied from the cake input machine 7 to the upper part of the sand layer 2. The dewatered cake in the sand layer portion 2 is pulverized by the fluidized sand 6, and since the high-temperature fluidized sand 6 has a large heat capacity, it is instantaneously dried, gasified, and burned.

The temperature of the sand layer 2 is controlled by the upper burner 9 of the sand layer.
a. Control is performed by adjusting the amount of oil supplied into the fluidized sand from the sand layer lower burner 9b. The combustion gas generated in the sand layer part 2 rises in the furnace and is completely burned in the free board part 3, and is discharged from the upper part of the furnace to an exhaust gas treatment system together with ash.
The exhaust gas treatment system includes an air preheater, a cyclone, a dry electric precipitator, a flue gas treatment tower, and the like.

The fluidized sand 6 is discharged from the discharge unit 10 to the outside of the furnace body 1, and after separating foreign matter, is poured into the sand layer unit 2 through the sand inlet 12 and circulated.

[0008]

In the above construction, when the temperature of the freeboard section falls below a predetermined temperature during the combustion of sludge, harmful substances are generated. Need to be kept high enough. However, since the sand layer upper burner 9a and the sand layer lower burner 9b are controlled by the sand layer temperature in the sand layer portion 2, it is difficult to control the freeboard temperature in the freeboard portion 3 depending on the operation. On the other hand, the starting burner 8 raises the temperature inside the furnace at the start of operation of the furnace, and has a large amount of minimum oil and a large amount of heat generated during use. Excessive temperature rise will result.

The present invention has been made to solve the above-mentioned problems, and has a method for controlling the temperature in a furnace of a fluidized bed incinerator capable of controlling the freeboard temperature independently of the sand layer temperature during the combustion of sludge. It is intended to provide the device.

[0010]

According to a first aspect of the present invention, there is provided a fluidized bed incinerator temperature control method according to the first aspect of the present invention, in which sewage sludge is incinerated, and a sand layer is formed in the furnace. In the fluidized bed incinerator that formed the combustion area of the freeboard section, the freeboard temperature was controlled by operating the sand layer upper burner arranged above the sand layer section, and the sand layer lower burner arranged below the sand layer section was operated. It controls the sand layer temperature.

[0011] With the above structure, the fuel oil ejected from the upper burner of the sand layer to the sand layer volatilizes the fluidized sand in the sand layer as a combustion medium, burns on the surface layer of the sand layer, and raises the freeboard temperature. The fuel oil ejected from the lower burner of the sand layer to the sand layer volatilizes the flowing sand in the sand layer as a combustion medium and burns in the sand layer to raise the temperature of the sand layer.
Therefore, the freeboard temperature and the sand layer temperature can be independently controlled by individually operating the sand layer upper burner and the sand layer lower burner.

Therefore, by operating the sand layer upper burner to increase the freeboard temperature and appropriately controlling the freeboard temperature, generation of harmful substances can be suppressed. The temperature of the sand layer fluctuates depending on the water content of the sludge to be charged.If the water content is high, the temperature of the sand layer will decrease, and if the water content is low, the temperature of the sand layer will increase. Thus, the sand layer temperature is controlled, and the change in the sand layer temperature is suppressed to perform stable combustion.

According to a second aspect of the present invention, there is provided a method for controlling the temperature in a furnace of a fluidized bed incinerator according to the present invention. When the temperature returns to the predetermined temperature,
The upper layer burner is operated with the freeboard temperature as the control target. With the above-described configuration, the sand layer temperature can be quickly returned to the predetermined temperature at the start of sludge introduction or when the properties (water content and organic matter amount) of the inputted sludge change rapidly and the sand layer temperature drops rapidly. Can be.

According to a third aspect of the present invention, there is provided a fluidized bed incinerator for a fluidized bed incinerator according to the present invention, wherein a sewage sludge is to be incinerated and a combustion zone of a sand layer and a free board is formed in the furnace. In the sand layer, a sand layer upper burner and a sand layer lower burner are provided in upper and lower two stages, a sand layer temperature sensor and a free board temperature sensor are provided in each of the sand layer part and the free board part. A control device for independently controlling the upper burners of the sand layer is provided.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The fluidized bed incinerator 30 shown in FIG.
Since the basic structure is the same as that shown in FIG. 4 previously, members performing the same function are denoted by the same reference numerals, and the description thereof will be omitted. The main part according to the present invention will be described.

In FIG. 1, a sand layer portion 2 is provided with a sand layer upper burner 31 and a sand layer lower burner 32 in two vertical stages.
Both burners have a structure in which fuel oil is jetted into sand by a small amount of compressed air for jetting. 500 for both burners
It is located at a distance of about 600 mm,
Numeral 2 is located at a distance of about 200 to 300 mm from the dispersion pipe 4. Each burner has its own fuel oil supply system 3
The output is controlled by adjusting the opening of the electric valves 31b and 32b provided in 1a and 32a. The operating devices 31c and 32c of the electric valves 31b and 32b are connected to the control device 3
3 via a signal line.

The control device 33 includes a sand layer upper burner control circuit 34 and a sand layer lower burner control circuit 35. The sand layer upper burner control circuit 34 controls the sand layer upper burner 31 by using the outputs of the sand layer temperature sensor 36 provided in the sand layer section 2 and the freeboard temperature sensor 37 provided in the freeboard section 3 as indices. Control circuit 3
5 controls the sand layer lower burner 32 using the output of the sand layer temperature sensor 36 as an index.

FIG. 2 is a flow chart in the sand layer upper burner control circuit 34. T1 and T2 are arbitrary temperatures, but in this embodiment, T1 = 690.
° C and T2 = 720 ° C. As shown in FIG. 2, the sand layer upper burner control circuit 34 compares the output value Ts of the sand layer temperature sensor 36 with the set value T1 and determines that the output value Ts is smaller than the set value T1. The upper sand layer burner 31 is controlled using the output value Ts as an index. When the output value Ts is larger than the set value T1, the upper sand layer burner 31 is controlled using the output value _TF of the freeboard temperature sensor 37 as an index. Control of the sand layer upper burner 31 operates the opening of the electric valve 31b via the operating device 31c,
This is performed by controlling the amount of fuel oil. Then, when the output value Ts of the sand layer temperature sensor 36 becomes larger than the set value T2, the sand layer upper burner 31 is controlled using the output value _TF of the freeboard temperature sensor 37 as an index.

As shown in FIG. 3, the sand layer lower burner control circuit 35 controls the sand layer lower burner 32 by using the output value Ts of the sand layer temperature sensor 36 as an index, and the electric valve 32b is controlled via an operating device 32c. By controlling the opening degree, the amount of fuel oil is controlled. Hereinafter, the operation of the above configuration will be described. The fuel oil ejected from the sand layer upper burner 31 to the sand layer portion 2 volatilizes the flowing sand 6 of the sand layer portion 2 as a combustion medium, burns on the surface layer of the sand layer portion 2, and mainly raises the freeboard temperature. Sand layer lower burner 32
The fuel oil ejected to the sand layer portion 2 volatilizes the flowing sand 6 in the sand layer portion 2 as a combustion medium and burns in the sand layer to raise the sand layer temperature.

For this reason, the control device 33 operates the sand layer upper burner 31 and the sand layer lower burner 32 individually in the sand layer upper burner control circuit 34 and the sand layer lower burner control circuit 35, thereby controlling the freeboard temperature and the sand layer temperature, respectively. Proprietary control and appropriate control of freeboard temperature suppress generation of harmful substances, and appropriate control of sand layer temperature suppresses changes in the sand layer temperature that fluctuates depending on the water content of the sludge to be charged. And perform stable combustion.

At the start of sludge feeding or when the properties (water content and organic matter content) of the sludge change suddenly and the sand layer temperature drops sharply, the controller 33 controls the upper sand layer burner 31 and the lower sand layer burner. Normal operation of operating both the sand layer upper temperature burner 31 with the freeboard temperature as the control object, operating both the sand layer temperature as the control target and returning the sand layer temperature to the predetermined temperature early, and when the sand layer temperature returns to the predetermined temperature. Return to.

[0022]

[Table 1] Table 1 shows actual furnace data showing the difference in the concentration of hydrogen cyanide in the exhaust gas from the furnace at the start of sludge introduction when the sand layer upper burner is controlled by the sand layer temperature and by the freeboard temperature.

[0023]

As described above, according to the present invention, the upper burner of the sand layer which burns in the surface layer of the sand layer and raises the freeboard temperature, and the lower burner of the sand layer which burns in the sand layer and raises the temperature of the sand layer. By individually controlling the freeboard temperature and the sand layer temperature, it is possible to independently control the freeboard temperature and the sand layer temperature.By appropriately controlling the freeboard temperature, it is possible to suppress the generation of harmful substances and operate the sand layer lower burner. By controlling the temperature of the sand layer, the change in temperature of the sand layer caused by the water content of the sludge can be suppressed and stable combustion can be performed.

Both the upper sand layer burner and the lower sand layer burner are operated with the sand layer temperature as a control object, and when the sand layer temperature returns to a predetermined temperature, the sludge input is operated by operating the free layer temperature as a control object and the sand layer upper burner. Even at the start, or when the properties (water content and organic matter amount) of the input sludge suddenly change and the sand layer temperature sharply decreases, the sand layer temperature can be quickly returned to the predetermined temperature.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an in-furnace temperature control device of a fluidized bed incinerator according to an embodiment of the present invention.

FIG. 2 is a flowchart of a sand layer upper burner control circuit in the embodiment.

FIG. 3 is a flowchart of a sand layer lower burner control circuit in the embodiment.

FIG. 4 is a schematic view showing a conventional fluidized bed incinerator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace body 2 Sand layer part 3 Free board part 6 Fluid sand 31 Sand layer upper burner 32 Sand layer lower burner 31a, 32a Fuel oil supply system 31b, 32b Electric valve 31c, 32c Actuator 33 Control device 34 Sand layer upper burner control circuit 35 Sand layer Lower burner control circuit 36 Sand layer temperature sensor 37 Free board temperature sensor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Kuroda 2-47, Shikitsu-Higashi 1-chome, Namiwa-ku, Osaka-shi, Osaka (72) Inventor Takahiro Horii Higashi-ichi Shikitsu, Naniwa-ku, Osaka-shi, Osaka No.2-47 F-term in Kubota Corporation (reference) 3K061 AA11 AB01 AC02 BA02 BA06 CA01 DB18 3K062 AA11 AB01 AC02 BA02 CA01 DA01

Claims (3)

[Claims] In a fluidized bed incinerator in which sewage sludge is incinerated and a combustion zone of a sand layer and a freeboard section is formed in the furnace, a freeboard temperature is controlled by operating a sand layer upper burner disposed above the sand layer. And controlling a sand layer temperature by operating a sand layer lower burner disposed below the sand layer portion. 2. When the sand layer temperature drops sharply, both the upper sand layer burner and the lower sand layer burner are operated with the sand layer temperature as a control target. When the sand layer temperature returns to a predetermined temperature, the freeboard temperature is controlled as the control target. The method of claim 1, wherein the upper burner is operated. 3. A fluidized bed incinerator in which sewage sludge is to be incinerated and a combustion zone of a sand layer portion and a free board portion is formed in the furnace body, wherein a sand layer upper burner and a sand layer lower burner are provided in a sand layer portion in two vertical stages, A sand layer temperature sensor and a free board temperature sensor are provided for each of the sand layer part and the free board part, and a control device is provided to control the sand layer lower burner and the sand layer upper burner independently using the outputs of both temperature sensors as indices. Temperature control device in a fluidized bed incinerator.