JP4243809B2 - Fluidized bed waste incinerator - Google Patents

Description

  The present invention relates to a fluidized bed waste incineration facility for incineration of waste such as municipal waste.

Many waste incineration facilities that incinerate wastes such as municipal wastes are burned in an incinerator having a fluidized bed at the bottom (see, for example, Patent Document 1). In this fluidized bed waste incineration facility, as shown in an example in FIG. 3, a fluidized bed 52 composed of a fluidized medium layer is usually formed at the bottom of the incinerator 51, and fluidized air and secondary combustion for fluidizing the fluidized medium. Air is blown into the incinerator 51 to burn the waste thrown into the incinerator 51. The flowing air is blown from the primary blower 53 and the secondary combustion air is blown from the secondary blower 54 to the incinerator 51 via the blow passages 55 and 56, respectively.
JP 2005-274025 A

  Further, the upper part of the incinerator 51 of the facility shown in FIG. 3 is a gas cooling chamber 57 for cooling the exhaust gas generated by the combustion of the waste to a predetermined temperature, and the exhaust gas is discharged from the gas cooling chamber 57 to the outside of the facility. A primary air preheater 59 for preheating the flowing air before being blown into the incinerator 51 by heat exchange with the exhaust gas is provided in the middle of the discharge pipe 58 to be discharged. In the flowing air blowing passage 55, a valve 60 that adjusts the amount of blown air into the incinerator 51 upstream of the primary air preheater 59 and a valve 61 that adjusts the passage amount of the primary air preheater 59. The incinerator 51 is provided with a water spray device 62 for adjusting the temperature of the fluidized bed 52 and an auxiliary burner 63.

  By the way, in the fluidized bed type waste incineration equipment as described above, generally, dredged sand having a large heat capacity is used as a fluidized medium for forming the fluidized bed of the incinerator, and it is put into the incinerator with dredged sand at a high temperature (about 600 to 700 ° C.). The waste generated is instantly dried, gasified and burned, and the heat keeps dredged sand at a high temperature. However, the temperature of this dredged sand, that is, the temperature of the fluidized bed, is greatly affected by the properties of the waste, and rises when there is a large amount of waste, such as paper and plastic, that generates a large amount of heat. When a large amount of waste with a small calorific value, such as a thing, is thrown in, it falls rapidly. Thus, if the fluidized bed temperature fluctuates greatly depending on the properties of the waste, the combustion state of the incinerator becomes unstable and troubles are likely to occur.

  Therefore, when the fluidized bed temperature rises greatly, the temperature of the fluidized air blown into the incinerator is lowered (measure 1), the input amount of waste with a large calorific value is reduced (measure 2), and the amount of fluidized air blown is reduced. Countermeasures such as (Countermeasure 3) and spraying water onto the fluidized bed (Countermeasure 4) are implemented. On the other hand, when the temperature of the fluidized bed is drastically reduced, the temperature of the fluidized air is increased (Countermeasure 1 '), and the amount of waste containing a lot of water is reduced to reduce heat loss due to latent heat of water in the sand layer (Countermeasure 2). ') Measures such as auxiliary combustion with auxiliary burner (Countermeasure 5) are taken.

  However, the conventional measures described above have the following problems. First, adjustment of the temperature of the flowing air (measures 1, 1 ′) is generally performed by adjusting the amount of flowing air that passes through the primary air preheater. However, if the amount of air passing through the preheater is changed, preheating is performed. The amount of heat recovered from the exhaust gas by the heater may fluctuate, and the pipe wall forming the exhaust gas passage of the preheater may be altered or corroded due to a temperature rise when the amount of passing air is reduced. Therefore, in practice, the amount of air passing through the preheater cannot be significantly reduced from the normal operation state, and the temperature of the fluid air blown into the incinerator cannot be sufficiently lowered. In addition, the exhaust gas temperature at the preheater inlet is set to be relatively low so as to suppress the rise in the preheater temperature when the passing air amount is reduced, and the temperature of the flowing air is effectively increased even if the passing air amount is increased. It was difficult to do.

  Next, the method of reducing the amount of waste input (measures 2, 2 ') leads to a decrease in the processing efficiency of the entire incineration facility. Also, if the amount of waste input is reduced when the temperature of the fluidized bed decreases, the total heat input to the incinerator will decrease, making it difficult to maintain the furnace temperature above the control standard lower limit value. Supporting combustion (Countermeasure 5) is required, leading to an increase in processing costs.

  The method (Countermeasure 3) of reducing the flow rate of flowing air when the fluidized bed temperature rises can effectively suppress the fluidized bed temperature rise by suppressing the combustion rate in the sand layer and promoting partial gasification combustion. However, if the amount of fluidized air blown is greatly reduced from the normal operation state, the fluidized bed cannot secure a good fluidized state, and non-combustible materials will accumulate in the fluidized bed. And when this poor flow state continues for a long period of time, accumulation of incombustible materials may cause incineration to stop.

  Further, in the method of spraying water onto the fluidized bed (Countermeasure 4), water is sprayed directly onto the cinnabar, which is a fluid medium, so that the cinnabar is collapsed and pulverized by heat shock and is easily taken out from the incinerator together with the exhaust gas. Furthermore, the cinnabar sand adheres to each other by bonding with Ca compounds or salt inorganic compounds, and there is also a problem that flow defects are likely to occur.

  An object of the present invention is to enable an efficient and stable operation by maintaining the fluidized bed at an appropriate temperature regardless of the properties of the waste put into the incinerator in the fluidized bed waste incineration facility. That is.

  In order to solve the above-mentioned problems, the present invention forms a fluidized bed composed of a fluidized medium layer at the bottom of an incinerator, and blows fluidized air and secondary combustion air into which the fluidized medium flows to the incinerator. In a fluidized bed type waste incineration facility for combusting the waste introduced into the incinerator, a primary air preheater for preheating by heat exchange with exhaust gas discharged from the incinerator before blowing the fluid air into the incinerator, A secondary air preheater is provided for preheating by heat exchange with the fluid air preheated by the primary air preheater before blowing the secondary combustion air into the incinerator, and the secondary combustion air passing through the secondary air preheater is provided. By adjusting the amount, the temperature at the time of blowing the fluidized air into the incinerator was adjusted.

  That is, a secondary air preheater that preheats the secondary combustion air by heat exchange with the flowing air preheated by the primary air preheater is provided, and the flowing air is determined by the amount of the secondary combustion air that passes through the secondary air preheater. By adjusting the temperature when the incinerator is blown, the total amount of fluid air is passed through the primary air preheater so that the amount of heat recovered by the primary air preheater can be kept constant at all times. As a result, the exhaust gas temperature at the inlet of the primary air preheater can be set higher than in the past according to the amount of recovered heat, and the primary temperature of the flowing air can be reduced without causing deterioration or corrosion due to excessive temperature rise in the tube wall of the primary air preheater. The temperature after passing through the air preheater can be increased. As a result, the temperature adjustable range at the time of inflow of the fluidized air into the incinerator is widened, and the fluidized bed is easily maintained at an appropriate temperature.

  In the above configuration, a part of the fluid air preheated by the primary air preheater is blown into the incinerator as secondary combustion air, thereby adjusting the amount of fluid air blown into the incinerator, If the lower limit value is set for each waste property, the fluidized bed can be kept in a good fluidized state at all times, and accumulation of incombustible substances in the fluidized bed can be prevented.

  Moreover, when providing the water spray apparatus which sprays water to a fluidized bed in the said incinerator, the temperature at the time of incinerator blowing of the said fluid air becomes the minimum of the adjustable range, and the quantity of the fluid air blown into the said incinerator Is a lower limit value for each waste property, and the water spray device is preferably operated only when the temperature of the fluidized bed is equal to or higher than a predetermined temperature. Thereby, the combustion state of the incinerator can be stabilized in an emergency in which the increase of the fluidized bed temperature cannot be suppressed by adjusting the fluidized air without causing a problem due to water spray on the fluidized bed during normal operation.

  As described above, the fluidized bed waste incineration facility of the present invention is provided with a secondary air preheater that preheats secondary combustion air by heat exchange with the fluid air preheated by the primary air preheater. Compared with, the temperature after passing the primary air preheater of the fluidized air can be increased, so the temperature adjustable range when the fluidized air is blown into the incinerator is wide, and the properties of the waste to be put into the incinerator Even if fluctuates, it is easy to maintain the fluidized bed at an appropriate temperature. In addition, this makes it possible to eliminate the need for conventional measures such as limiting the amount of waste input, thereby improving the processing efficiency of the entire incineration facility and improving the stability of the combustion state.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. The basic configuration of the fluidized bed waste incineration facility is the same as that of the conventional facility shown in FIG. That is, a fluidized bed 2 composed of a fluidized medium layer is formed at the bottom of the incinerator 1, and fluidized air and secondary combustion air for fluidizing the fluidized medium are blown into the incinerator 1, and charged into the incinerator 1 through the inlet 1 a. Burning waste. The fluidized air is blown from the primary blower 3 and the secondary combustion air is blown from the secondary blower 4 to the incinerator 1 via the air passages 5 and 6, respectively, and the sand is used as the fluidized medium of the fluidized bed 2. Yes.

  The upper part of the incinerator 1 is a gas cooling chamber 7 that cools the exhaust gas generated by the combustion of waste to a predetermined temperature, and in the middle of the discharge pipe 8 that exhausts the exhaust gas from the gas cooling chamber 7 to the outside of the facility, A primary air preheater 9 for preheating the fluid air before being blown into the incinerator 1 by heat exchange with the exhaust gas is provided, the water spray device 10 for adjusting the temperature of the fluidized bed 2 and the auxiliary burner 11 in the incinerator 1. Is also the same as the conventional equipment.

  On the other hand, the difference between this waste incineration facility and the conventional facility is as follows. First, in the fluid air blowing passage 5, the secondary combustion air before being blown into the incinerator 1 is exchanged with the fluid air preheated by the primary air preheater 9 on the downstream side of the primary air preheater 9. A secondary air preheater 12 for preheating is provided. A valve 13 for adjusting the amount of secondary combustion air that passes through the secondary air preheater 12 is attached to the air passage 6 for the secondary combustion air. The temperature at the time of blowing the air incinerator 1 can be adjusted.

Further, a branch passage 5 a that branches downstream from the primary air preheater 9 and reaches the center of the incinerator 1 is provided in the airflow passage 5 for the flowing air. Part of this is blown into the incinerator 1 as secondary combustion air through this branch 5a. The amount of fluid air blown into the incinerator 1 can be adjusted by changing the opening of the valve 14 attached to the branch 5a. In this incinerator 1, the flow rate of fluidized air is set to 0.15 m / sec or more for waste with a large calorific value, and the fluidized bed superficial velocity is 0 for waste with a small calorific value. By adjusting so that it may become more than .25 m / sec, the fluidized bed 2 can be maintained in a good fluidized state, and accumulation of noncombustible substances in the fluidized bed 2 can be prevented. In the case of waste with a large calorific value, it is desirable to secure the fluidized bed superficial velocity and set the hearth load factor to 500 to 550 kg / (m ² · h).

  The water spray device 10 of the incinerator 1 operates only when the temperature of the fluidized bed 2 rises beyond a predetermined upper limit value even if the temperature of the fluidized air and the amount of blowing are adjusted to the maximum. It has become. That is, the temperature at the time of blowing the incinerator 1 of the fluidized air becomes the lower limit of the adjustable range, the amount blown into the incinerator 1 becomes the lower limit value according to the waste property, and the temperature of the fluidized bed 2 is the predetermined temperature (720 ° C. When the temperature reaches about the above, water is sprayed onto the fluidized bed 2 to suppress an increase in temperature of the fluidized bed 2 and to stabilize the combustion state of the incinerator 1. Therefore, at the time of normal operation, there is no problem that the sand is pulverized by the water spray on the fluidized bed 2 and taken out of the incinerator 1 or the sand is stuck to each other to cause poor flow.

  This waste incineration equipment has the above-described configuration, and the temperature at the time of blowing the flowing air into the incinerator 1 is adjusted by the amount of the secondary combustion air that passes through the secondary air preheater 12, so that the flowing air Thus, the amount of heat recovered by the primary air preheater 9 can be kept constant at all times. For this reason, the exhaust gas temperature at the inlet of the primary air preheater 9 is set higher (about 500 ° C.) than the conventional equipment, and the temperature after passing the primary air preheater 9 of the flowing air is increased (set to about 350 ° C.). Can do. Therefore, the temperature controllable range at the time of blowing the incinerator 1 with flowing air is wide (about 50 to 310 ° C.), and even if the properties of the waste put into the incinerator 1 fluctuate, the waste input amount is not reduced. The fluidized bed 2 can be maintained at an appropriate temperature (about 600 to 700 ° C.), and the stability of the combustion state can be improved. In addition, since the secondary combustion air can be preheated to about 150 ° C., this also promotes stable combustion in the furnace. Furthermore, since there are almost no cases in which auxiliary combustion by the auxiliary burner 11 is necessary due to the waste input amount limitation, the processing cost is also lower than before.

  In addition, the present invention is not limited to the incineration facility provided with the gas cooling chamber in the upper portion of the incinerator as shown in FIG. 1, but as shown in FIG. 2, the incineration facility of the type in which the gas cooling chamber is separated from the incinerator, Of course it can be applied.

Schematic of the waste incineration facility of the embodiment Schematic of the example which changed arrangement of the gas cooling room of Drawing 1 Schematic of an example of conventional waste incineration equipment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Incinerator 2 Fluidized bed 3, 4 Blower 5 Blower path 5a Branch 6 Blower path 7 Gas cooling chamber 8 Discharge pipe 9 Primary air preheater 10 Water spray apparatus 11 Auxiliary burner 12 Secondary air preheater 13, 14 Valve

Claims (3)

  Fluidized bed type waste that forms a fluidized bed consisting of a fluidized medium layer at the bottom of the incinerator, blows fluidized air that moves the fluidized medium and secondary combustion air into the incinerator, and burns the waste that has been put into the incinerator In a waste incineration facility, a primary air preheater preheated by heat exchange with exhaust gas discharged from the incinerator before blowing the fluidized air into the incinerator, and the primary air before blowing the secondary combustion air into the incinerator An incinerator for the fluidized air is provided by providing a secondary air preheater for preheating by heat exchange with the fluidized air preheated by the preheater, and adjusting the amount of the secondary combustion air that passes through the secondary air preheater. Fluidized bed waste incineration facility characterized by adjusting the temperature at the time of blowing.   A part of the fluid air preheated by the primary air preheater is blown into the incinerator as secondary combustion air, so that the amount of fluid air blown into the incinerator is adjusted, and the lower limit value is set as waste. The fluidized bed waste incinerator according to claim 1, which is set according to properties.   The incinerator is provided with a water spraying device for spraying water onto a fluidized bed, the temperature when the fluidized air is blown into the incinerator becomes the lower limit of the adjustable range, and the amount of fluidized air blown into the incinerator is a waste property The fluidized-bed waste incinerator according to claim 2, wherein the water spray device is operated when another lower limit value is reached and the temperature of the fluidized bed exceeds a predetermined temperature. .

Images