JPS6243093B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fluidized bed incineration method for incinerating garbage such as municipal waste and industrial waste using a fluidized bed incinerator. In recent years, fluidized bed incinerators have been increasingly used as incinerators for municipal waste, industrial waste, and other garbage, but in conventional incinerators, it is difficult to maintain the fluid medium such as sand in an appropriate fluid state. However, this method has the drawback of causing unnecessary loss of power. In order to eliminate this drawback, the inventors conducted repeated research and conducted many experiments, and based on the knowledge obtained at that time, the present invention was made. When incineration is carried out using a fluidized bed incinerator, the air sent from the hearth for fluidization (primary air) is also used to supply oxygen for combustion, but the amount of air for combustion is insufficient. To compensate for this, secondary air exclusively for combustion is supplied to the freeboard section. The present invention limits the amount of primary air to the minimum amount necessary to maintain the fluidized medium in a proper fluid state, and uses the minimum amount of secondary air to compensate for the lack of combustion air required to complete combustion. The object of the present invention is to provide a fluidized bed incineration method for waste, which supplements this and thereby prevents wasteful loss of power for supplying air. As a research to achieve this purpose, first of all,
In order to find a way to minimize the amount of primary air,
The inventors focused on the fact that the amount of fluidized media that forms the fluidized bed (that is, since the area of the hearth is constant, the height is necessarily static) should be appropriately selected in relation to the calorific value of the waste. We conducted an experiment to find the optimal holding amount (static height) for garbage with a certain calorific value. According to the experimental results, if the calorific value of the waste is 700kcal/Kg or more based on the raw waste, there is no need for auxiliary combustion and natural combustion is possible. However, as a condition for maintaining the natural state, it was found that when the calorific value of the waste is low, it is necessary to maintain the static height of the fluid medium higher than when the calorific value is high. FIG. 1 shows an example of experimental results, and is a graph that provides a guideline for the appropriate static height of the fluidizing medium with respect to the lower calorific value of raw waste base. The amount of primary air depends on conditions such as the particle size and particle size distribution of the fluidized medium such as sand, the opening of the sieve installed to remove non-flammable residue from the hearth, and the gas flow rate in the furnace. , is a nearly constant value in each case. As mentioned above, the appropriate height of the static layer is determined based on the change in the calorific value of the waste, and the rotational speed of the blower is adjusted to correspond to the height of the static layer to keep the amount of primary air constant. In other words, the air volume, wind pressure, and rotational speed of the blower have the relationship shown in Figure 2. For example, as the waste calorific value decreases, the static height decreases, and the pressure drop in the fluidized bed increases by H ₁
If the blower speed decreases from n ₁ to _{n 2}
If the air flow rate Q is reduced to , the air volume Q can be kept constant at a predetermined value _Q1 . At this time, since the number of rotations is reduced from n ₁ to n ₂ , the power decreases in proportion to the cube of the rotation speed, so it is possible to significantly reduce the power. In this way, the amount of primary air can be secured with the least amount of power in response to changes in the calorific value of the waste. Next, in order to minimize the amount of secondary air, the oxygen concentration of the combustion exhaust gas at the incinerator outlet is detected, and the amount of secondary air for combustion is controlled so that the oxygen concentration remains at a predetermined value. Moreover, the furnace internal pressure can be kept constant by detecting the furnace internal pressure and controlling the induction fan inlet damper. The present invention provides a fluidized bed incineration method for waste using a fluidized bed incinerator, in which the height of the static bed of the fluidized medium is adjusted according to the calorific value of the object to be incinerated, and the height of the static bed of the fluidized medium is adjusted according to the height of the static bed. The rotational speed of the combustion blower is controlled to maintain the flow rate of primary air at a predetermined value, the oxygen concentration in the combustion exhaust gas is detected, and the flow rate of secondary combustion air is adjusted so that the oxygen concentration becomes the predetermined value. This is a fluidized bed incineration method for waste, which is characterized by controlling the Embodiments of the present invention will be described using the drawings. In FIG. 3, reference numeral 1 denotes an incinerator, which blows out primary air for fluidization from a dispersion plate 3 on a lower wind box 2 to fluidize a fluidized medium such as sand to form a fluidized bed 4. 5 is a blower that supplies primary air for fluidization, and the primary air is supplied to an air preheater 6.
After being preheated by the exhaust gas passing through the exhaust gas pipe 7, it is supplied to the wind box 2 via the air supply pipe 8. 9 is a blower for secondary air for combustion; air pipe 10
It is supplied to the freeboard 11 through the. Garbage to be incinerated is fed into the fluidized bed 4 by a garbage feeder 12. Reference numeral 13 denotes a discharge pipe for discharging non-combustible residue together with the fluidized medium. 14 is a separation mechanism that separates and discharges non-combustible residue, and the fluidized medium passes through a regeneration mechanism 15 to a storage tank 16.
The waste is then sent to the incinerator 1 again via the lifting mechanism 17. By appropriately changing the amount of fluidized medium discharged from the discharge pipe 13 by the lifting mechanism 17, the amount of fluidized medium held in the incinerator 1 can be increased or decreased. Since the area of the hearth is constant, adjusting the holding amount thus amounts to adjusting the height of the static bed of the fluidized medium. 18 is an air volume indicating controller for detecting the discharge air volume of the blower 5 and maintaining a predetermined air volume setting value;
The number of revolutions of the driving electric motor 19 of the blower 5 is controlled. Reference numeral 20 denotes an air volume setting device, which adjusts the predetermined air volume Q 1 as shown in Fig. 2 based on the height of the fluidized medium stationary bed determined according to the lower calorific value of the raw dust base as shown in Fig. ₁ above. Air volume indicator controller 1 so that the rotation speed n ₂ is selected to be
This is to perform cascade control of the air volume setting value in step 8. Reference numeral 21 denotes an oxygen concentration indicating controller, which operates the rotation speed of the electric motor 22 that drives the blower 9 so that the oxygen concentration in the exhaust gas is maintained at a predetermined set value. During operation, the lower calorific value of the raw dust base of the waste to be incinerated is predicted using the measurement range or conventional data, and based on this, the optimal static bed height of the fluidized medium is determined, and the flow rate in the furnace is determined. The amount of media held is adjusted to match the static height to the optimal height, and the blower 5 is adjusted to correspond to the change in static pressure commensurate with the ventilation resistance at this time.
The rotation speed is controlled so that the amount of primary air becomes a predetermined minimum value. On the other hand, for the secondary air blower 9, the oxygen concentration in the exhaust gas is detected by the oxygen concentration indicator controller 21 and the electric motor 22 is operated so that the oxygen concentration in the exhaust gas reaches a predetermined set value. Make it. An example of the combustion process is shown in Figure 4. a indicates the temporal change in fluidized bed temperature, and sections A, B, C, D...
It can be divided into The specifications of each section are as shown in the table below.

[Table] That is, in section A, waste with a calorific value of 950 kcal/Kg was incinerated with a fluidized medium bed height of 950 mm, and a natural state could be maintained at 650°C. In section B, the quality of waste is changed to increase the calorific value.
1500kcal/Kg of garbage was incinerated. Amount of incineration, layer height,
The primary air amount is the same as in section A. Furthermore, since the amount of heat generated increases and combustion air becomes insufficient, the oxygen concentration in the exhaust gas falls below the set value, and the blower 9 is started to supply secondary air so that the oxygen concentration becomes constant. The medium temperature gradually rose to 700°C. Since the medium temperature can be maintained in its natural state by keeping it at 650℃, the static height of the fluidized medium can be adjusted according to Figure 1.
The distance was lowered to 700 mm, and the other conditions were the same as Section B.
As a result, in section C, the medium temperature gradually decreases to 650
It became almost constant at ℃ and was able to maintain its natural state. Furthermore, in section D, the quality of the waste was changed to 950kcal/
When Kg of waste was supplied, the medium temperature gradually decreased and the natural state could not be maintained, making it necessary to burn the auxiliary fuel oil. According to the present invention, it is possible to provide a fluidized bed incineration method for waste, which can obtain the minimum air volume of both primary air and secondary air according to the conditions of the waste quality, and saves power. This has the following effects.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the calorific value of waste and the static layer height of the fluidized medium, Figure 2 is a graph showing the relationship between the static pressure and air volume required to form a fluidized bed, and Figure 3 is a graph showing the relationship between the static pressure and air volume required for fluidized bed formation. FIG. 4, which is a flowchart of the embodiment, is a graph showing changes in fluidized bed temperature and exhaust gas O ₂ concentration changes in the process of the embodiment of the present invention. 1... Incinerator, 2... Wind box, 3...
... Dispersion plate, 4 ... Fluidized bed, 5 ... Air blower, 6 ...
Air preheater, 7... Exhaust gas pipe, 8... Air supply pipe, 9
... Air blower, 10 ... Air pipe, 11 ... Free board, 12 ... Garbage feeder, 13 ... Discharge pipe, 1
4... Separation mechanism, 15... Regeneration mechanism, 16... Storage tank, 17... Lifting mechanism, 18... Air volume indicator controller, 19... Electric motor, 20... Air volume setting device, 21
...Oxygen concentration indicator controller, 22...Electric motor.

Claims (1)

[Claims] 1. In a fluidized bed incineration method for waste using a fluidized bed incinerator, the height of the static bed of the fluidized medium is adjusted according to the calorific value of the material to be incinerated, and the height of the fluidized bed is adjusted according to the height of the static bed. control the rotational speed of the engine to maintain the flow rate of the primary air at a predetermined value, detect the oxygen concentration in the combustion exhaust gas, and control the flow rate of the secondary combustion air so that the oxygen concentration becomes the predetermined value. A fluidized bed incineration method for waste, which is characterized by: