JPH094810A - Water supply method for waste heat boiler of fluidized bed waste incinerator - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a method for supplying water to a waste heat boiler, which can suppress the fluctuation in the amount of steam generated due to the fluctuation of the combustion amount. A signal of a furnace pressure measured by a pressure measuring device 30, a steam generation amount measured by a steam flow meter 25, and a water level signal of a boiler drum 21 measured by a level meter 24 is sent to a calculation control mechanism 40. . In the arithmetic control mechanism 40, arithmetic processing based on these signals is performed. The signal of the water supply amount determined by this arithmetic processing is sent to the water supply flow rate controller 26, and the water supply amount is adjusted. When supplying water as described above, if the furnace pressure is within the predetermined range, flow rate control is performed based on the steam generation amount and the water level measurement value in the boiler drum, and if the furnace pressure is outside the predetermined range. The flow rate is controlled according to the furnace pressure. [Effect] The quality of the generated steam is improved, and the generated steam can be effectively used for various purposes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of supplying water to a waste heat boiler of a fluidized bed waste incinerator.

[0002]

2. Description of the Related Art Even in a fluidized bed type waste incinerator for incinerating municipal solid waste or industrial waste, a waste heat boiler is usually provided as a means for effectively utilizing waste heat. FIG. 3 is an explanatory diagram relating to a conventional water supply method in a waste heat boiler installed in a fluidized bed waste incinerator. Reference numeral 1 denotes a fluidized bed incinerator body, and inside the furnace body 1, a dispersion plate 2 having a large number of air ejection ports is provided in a lower portion thereof,
A fluid medium such as silica sand is filled on the dispersion plate 2. 4 is a wind box for distributing the air jetted from the dispersion plate 2, 6 is primary combustion air piping, 7 is secondary combustion air piping,
Reference numeral 3 is an outlet for the fluid medium and the incombustible material. Then, in the inside of the furnace body 1 during operation, the fluidized medium is blown up by the air blown from the primary combustion air pipe 6, and the high temperature fluidized bed 60 is formed.

In the fluidized bed incinerator configured as described above, the waste material 70 is charged into the furnace body 1 from the waste material feeder 8 through the chute 9. The waste 70 charged into the furnace body 1 falls on the high temperature fluidized bed 60, mixes with the fluidized medium, and is immediately ignited and burned. Therefore, the waste 70
Burns in a very short time. The fluidized medium is extracted from the discharge port 3 together with the incombustibles contained in the waste, and after the incombustibles are removed, the fluidized medium is circulated into the furnace main body 1 via a route not shown.

On the other hand, in the combustion exhaust gas generated in the fluidized bed 70, the uncombusted gas components contained therein are burned by the blowing of air from the secondary combustion air pipe 7 and discharged from the exhaust gas discharge port 5. . This exhaust gas is the waste heat boiler 2
At 0, the heat is recovered, then, after treatments such as removal of harmful gases and dust removal are carried out, it is released into the atmosphere.

In the waste heat boiler 20, a water supply pipe 22
Water is supplied from the steam generator to the boiler drum 21, and steam generated by heat exchange between the water and the exhaust gas is taken out from the steam pipe 23.

In this case, the water supply to the boiler drum 21 is
It is performed as follows. A signal of the steam generation amount measured by the steam flow meter 25 is sent to the arithmetic and control unit 50, and the boiler drum 21 measured by the level meter 24.
The water level signal is sent to the arithmetic and control unit 50. In the arithmetic and control unit 70, the water supply amount corresponding to the measured steam generation amount is calculated, and the calculated value is corrected based on the water level measurement value of the boiler drum 21, and the signal of the corrected water supply amount is obtained. It is sent to the water supply flow rate controller 26. In the water supply flow rate controller 26, the amount of water supply is adjusted based on the signal from the arithmetic and control unit 50.

As described above, according to the conventional technique, the water supply to the boiler drum 21 is controlled based on the steam generation amount corrected by the water level value of the boiler drum, so that the water level of the boiler drum 21 does not change. Done.

[0008]

By the way, in the waste heat boiler of the fluidized bed type waste incinerator, the fluctuation of the steam generation amount is large and the utilization of the extracted steam is limited to a specific use. There is. This fluctuation of the steam generation amount directly occurs with the change of the combustion amount in the furnace, and in the waste heat boiler of the waste incinerator, the fluctuation does not occur to some extent. Although this is an unavoidable phenomenon, when water is supplied to the boiler drum 21 by the above-mentioned conventional method, the fluctuation of the steam generation amount becomes significantly larger than the fluctuation of the combustion amount, and the fluctuation due to this changes the steam in many directions. It is a cause that can not be used for.
Such large fluctuations in the steam generation amount occur as follows.

When the waste is incinerated, the waste is a mixture of various properties, so that it is difficult to uniformly supply the waste into the furnace, and the supply amount varies. Moreover, as described above, the input waste is promptly dried or thermally decomposed to start combustion. Therefore, the fluctuation of the waste supply amount immediately appears as the fluctuation of the combustion amount.

However, the water supply to the boiler drum according to the prior art is performed by a method of controlling the water supply amount based on the steam generation amount and the measured value of the water level of the boiler drum so that the water level of the boiler drum does not change. The fluctuation of the steam generation amount at this time occurs in a state of being amplified more than the fluctuation of the combustion amount.

For example, when the amount of combustion increases, the amount of water evaporated in the boiler system increases and the amount of gas bodies (bubbles) existing in the water increases. As a result, the volume of water existing in the system increases, and the water level in the boiler drum rises. This reduces the amount of water supplied to the boiler drum. Since the water supplied to the boiler drum is at a low temperature, when the amount of water supply decreases, the amount of cooling in the system decreases, and the amount of water evaporation increases accordingly. Therefore, the amount of bubbles in the system is further increased. The increase in the amount of bubbles further reduces the amount of water supply. Then, the amount of evaporation further increases.

When the combustion amount is reduced, the evaporation amount of water is reduced and the amount of bubbles in the water in the system is reduced. The volume of water present in the system is reduced and the water level in the boiler drum is reduced. Therefore, the amount of water supplied to the boiler drum increases. After that, the opposite phenomenon occurs when the combustion amount increases, the water supply amount further increases, and the evaporation amount further decreases.

The above-mentioned phenomenon is repeated every time the combustion amount changes. As described above, in the conventional technique, the amount of water supplied does not correspond to the amount of heat that heats the inside of the system, so the amount of evaporation of water fluctuates significantly.

FIG. 11 is a diagram showing the change over time in the amount of steam generated when the conventional water supply method is carried out. This figure is an example showing changes in the amount of steam generated when industrial waste is incinerated in a fluidized bed incinerator with a processing capacity of 60 t / d, and shows that the changes in the amount of steam generated are extremely large.

The present invention has been made in order to solve the above-mentioned problems, and even if the combustion amount fluctuates, the fluctuation of the steam generation amount due to the fluctuation can be suppressed to a small level. It is an object to provide a method for supplying water to a waste heat boiler of a furnace.

[0016]

The invention according to claim 1 is
A method of continuously measuring the pressure in the furnace, the amount of steam generated, and the water level in the boiler drum, and controlling the water supply amount based on these measured values to supply water to the boiler drum,
When the pressure in the furnace is within the specified range, water is supplied by controlling the flow rate based on the steam generation amount and the measured water level in the boiler drum, and when the pressure in the furnace is outside the specified range, This is a method of supplying water by controlling the flow rate according to the internal pressure.

The invention according to claim 2 is such that the furnace pressure,
It is a method of continuously measuring the steam generation amount and the water level in the boiler drum, and controlling the water supply amount based on these measured values to supply water to the boiler drum. In some cases, the flow rate is controlled based on the steam generation amount and the measured water level in the boiler drum to supply water, and when the reactor pressure is out of the specified range, the flow rate control is performed according to the reactor pressure. When the water level in the boiler drum exceeds the upper warning value or falls below the lower warning value, water will be supplied regardless of the measured furnace pressure and steam generation value. This is a method of supplying water by controlling the flow rate based on the measured value of the water level in the drum.

[0018]

As described above, in the operation of the waste heat boiler installed in the fluidized bed waste incinerator, it is unavoidable that the steam generation amount fluctuates due to the fluctuation of the combustion amount. When supplying water to the boiler by controlling the flow rate so that the water level of the boiler drum does not change, the steam generation amount will change more drastically. This big fluctuation
In the water supply according to the conventional technique, the amount of water commensurate with the amount of heat for heating the boiler system is not necessarily supplied, and when the combustion amount fluctuates, the amount of water supply to the heating amount is changed accordingly. It is caused by excess and deficiency. In particular, when the combustion amount fluctuates significantly, the excess or deficiency of the water supply amount with respect to the above heating amount becomes remarkable,
This is the cause of further increasing fluctuations in the amount of steam generated.

Therefore, in the present invention, an amount of water commensurate with the amount of heating in the system at that time is supplied to suppress fluctuations in the amount of steam generated.
The heating amount is a change amount that is almost uniquely determined by the combustion amount. Therefore, if control is performed to increase or decrease the water supply amount according to the change in the combustion amount, the amount of water corresponding to the heating amount is supplied. To be done.

The change in the amount of combustion in the furnace can be grasped by continuously measuring the pressure in the furnace. In the fluidized bed incinerator, the injected waste quickly starts burning, so that when a large amount of waste is injected, the combustion exhaust gas accumulated in the furnace rapidly increases. Therefore, if the pressure inside the furnace is continuously measured, the change in the combustion amount can be grasped from the pressure.

However, in the fluidized bed type waste incinerator, the amount of waste supplied varies, and accordingly, the amount of combustion fluctuates little by little. Therefore, if the amount of water supplied is controlled solely based on the change in the amount of combustion, the amount of water supplied will rapidly increase and decrease, and the amount of water that will follow the change in the amount of combustion will be increased (amount that is commensurate with the amount of heat in the system). Water) will not be supplied.

Therefore, when controlling the water supply amount, the change in the furnace pressure, which is grasped as the change in the combustion amount, is relatively small, and the change is in a state of being allowed to some extent.
Different control methods are applied to cases in which there is a large fluctuation in the furnace pressure and a situation in which fluctuations in the steam generation amount become even larger if control is not performed according to this fluctuation.

That is, when the measured value of the furnace pressure falls within a predetermined control range (hereinafter referred to as a predetermined range),
Water is supplied according to the amount of steam generated and the measured value of the water level in the boiler drum, to prevent a sudden increase or decrease in the amount of water supply. If the measured value of the furnace pressure is out of the specified range, water is supplied in an amount according to the measured value of the furnace pressure, regardless of the steam generation amount and the water level value in the boiler drum. Be seen.

As described above, when the measured value of the pressure in the furnace fluctuates and goes out of the predetermined range, if water is supplied in an amount according to the measured value, the cause of the remarkable fluctuation of the steam generation amount may be caused. Since it is removed, fluctuations in the steam generation amount are suppressed.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of an embodiment according to the present invention. In FIG. 1, the same parts as those in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted. In this embodiment,
The pressure in the furnace is continuously measured by the pressure measuring device 30, and a signal of the pressure in the furnace is sent to the arithmetic and control unit 40. In addition to the in-furnace pressure, the amount of steam generated measured by the steam flow meter 25 and the water level signal of the boiler drum 21 measured by the level meter 24 are used as the arithmetic control mechanism 40.
Sent to In the arithmetic control mechanism 40, arithmetic processing based on these signals is performed, and the signal of the water supply amount determined by this arithmetic processing is sent to the water supply flow rate controller 26. In the water supply flow rate controller 26, the amount of water supply is adjusted based on the signal from the arithmetic and control unit 40.

Next, the control of the water supply amount described above will be described with reference to FIGS. 2 and 4. FIG. 2 is an explanatory diagram related to the mechanism of water supply amount control in FIG. 1. Further, FIG. 4 is a diagram showing the tendency of the pressure in the furnace to change with time, and U in the diagram indicates the upper limit control value.

First, the arithmetic and control unit 40 checks whether or not there is an abnormality in the water level in the boiler drum, and if the water level reaches the upper limit warning value or the lower limit warning value, it is checked. Outputs a signal of the water supply amount based on the water level of the boiler drum, and this signal is sent to the water supply flow rate controller 26. In this case,
The amount of water supply is controlled so that the water level of the boiler drum is within the upper and lower warning levels.

When the furnace pressure is within the predetermined range below the upper limit control value U, the measured steam generation amount is corrected based on the measured water level of the boiler drum, and the corrected steam generation amount is corrected. The amount of water supply is calculated based on. Then, the signal of the water supply amount is sent to the water supply flow rate controller 26. In this case, the water supply amount is controlled so that the water level of the boiler drum becomes constant.

When the pressure in the furnace exceeds the upper limit control value U and is out of the predetermined range, the amount of water supply is calculated based only on the value of the pressure in the furnace, and the signal of this amount of water supply is the flow rate of water supply. It is sent to the controller 26.

The upper limit control value U is set in a range in which the fluctuation of the steam generation amount is as small as possible, and the value is appropriately determined based on the operation data.

In addition, when the value of the in-furnace pressure is within the predetermined range, control is not performed based on the value of the in-reactor pressure grasped as the combustion amount, but the measured value falling within the predetermined range. Since most of the values are in a small fluctuation process, the fluctuation of the steam generation amount due to the change of the furnace pressure in this predetermined range does not become so large, and is within an allowable level.

Further, in FIG. 4, the lower limit control value is not provided when setting the predetermined range of the furnace pressure, but the reason is as follows.

First, when the frequency of waste supply amount (combustion amount) fluctuating and falling outside the control range is divided into cases of excessive supply and cases of excessive supply, the frequency of excessive supply is extremely high. The fluctuation at that time is also large. In addition, the frequency of undersupply is relatively low, and the fluctuation at that time is small. For this reason, if only the upper limit control value is provided, a large change in the combustion amount can be grasped, and therefore, even if the lower limit control value is not set, the change in the steam generation amount does not become so large.

Next, the waste introduced into the furnace immediately starts burning, but the amount of combustion is large immediately after the introduction of the waste and decreases with the lapse of time. Then, the generated combustion exhaust gas is extracted by the suction fan, and by adjusting the suction amount of this combustion exhaust gas, it is operated so that the pressure inside the furnace falls below a certain level,
When a large amount of waste is input and the peak of the pressure inside the furnace appears, after that, due to the time delay in adjusting the gas suction amount,
The phenomenon that the pressure value drops sharply occurs. Therefore, the fluctuation of the measured value on the low pressure side does not necessarily reflect the actual pressure state.

Next, a description will be given of the results when water is supplied by the method described with reference to FIGS. 1 and 2 in the waste heat boiler installed in the 60 t / d fluidized bed incinerator for incinerating industrial waste. The change over time in the amount of steam generated at this time is shown in FIG.
It was as shown in. The fluctuation range of this steam generation amount is shown in FIG.
It is reduced to about 1/4 of the fluctuation width in the case of the conventional technique shown in FIG. Therefore, the steam obtained from this waste heat boiler can be used as a power source for equipment such as a turbine and a blower for power generation.

[0036]

In the present invention, the water supply to the boiler drum is performed by the flow rate control divided into the case where the measured value of the furnace pressure is within the predetermined range and the case where the measured value is outside the predetermined range. Since water is supplied in an amount commensurate with the amount of heat in the boiler system at that point in time, fluctuations in the amount of steam generated are extremely small. As a result, the quality of the steam is improved, and the generated steam can be effectively used for various purposes.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment according to the present invention.

FIG. 2 is an explanatory diagram related to a mechanism of water supply amount control in FIG.

FIG. 3 is an explanatory diagram relating to a conventional water supply method in a waste heat boiler installed in a fluidized bed waste incinerator.

FIG. 4 is a diagram showing a tendency of temporal changes in furnace pressure.

FIG. 5 is a diagram showing changes with time in the amount of steam generated when the present invention is carried out.

FIG. 6 is a diagram showing a change over time in the amount of steam generated in the case of a conventional technique.

[Explanation of symbols] 1 fluidized bed incinerator main body 5 gas outlet 6 primary air piping 7 secondary air piping 8 waste feeder 9 waste input chute 20 waste heat boiler 21 boiler drum 22 water supply piping 23 steam piping 24 level meter 25 steam flow meter 26 feed water flow controller 30 pressure measuring device 40 arithmetic control mechanism 60 fluidized bed 70 waste

Claims (2)

[Claims] 1. A method for supplying water to a boiler drum by continuously measuring the pressure in the furnace, the amount of steam generated, and the water level in the boiler drum, and controlling the amount of water supply based on these measured values. If the pressure in the furnace is within the specified range,
Water is supplied by controlling the flow rate based on the amount of steam generated and the measured water level in the boiler drum, and when the pressure in the furnace is outside the specified range, the flow rate is controlled according to the pressure in the furnace to supply water. Water supply method for waste heat boiler of floor-type waste incinerator. 2. A method for supplying water to a boiler drum by continuously measuring the furnace pressure, the steam generation amount, and the water level in the boiler drum, and controlling the water supply amount based on these measured values. If the pressure in the furnace is within the specified range,
Water is supplied by controlling the flow rate based on the amount of steam generated and the measured water level in the boiler drum, and when the pressure in the furnace is out of the specified range, the flow rate is controlled according to the pressure in the furnace to supply water. , If the water level in the boiler drum exceeds the upper warning value or falls below the lower warning value, the water level in the boiler drum is irrespective of the measured reactor pressure and steam generation value. A method of supplying water to the waste heat boiler of a fluidized bed waste incinerator that supplies water by controlling the flow rate based on measured values.