JP2020098081A - Combustion control method - Google Patents

Abstract

To provide a novel combustion control method according to the present invention, capable of maintaining a stable combustion state in a vertical waste incinerator.SOLUTION: The combustion control method for use in a vertical waste incinerator 1 carrying out incineration processing of waste W by charging the waste W into a furnace 11 to incinerate the waste W while feeding combustion air from the lower part of a sedimentary layer W1 formed of the waste W having been charged thereinto and successively discharging incineration ash from the bottom of the furnace, comprises a process of changing the oxygen concentration in combustion air while maintaining the supply amount of combustion air within a specified range to control the incineration state of the waste W.SELECTED DRAWING: Figure 1

Description

The present invention relates to a combustion control method for a vertical refuse incinerator.

The “vertical refuse incinerator” puts waste into the furnace, burns the waste while supplying combustion air from the bottom of the sediment layer formed by the thrown waste, and burns the incinerated ash from the bottom of the furnace. It is an incinerator that employs an incineration system that incinerates waste by sequentially discharging it.

In the conventional vertical refuse incinerator, the amount of combustion air (primary combustion air) is set to about 0.8 to 1.3 times the theoretical air amount, so that the accumulated layer of the waste is sequentially arranged from the top. Combustible gas (gaseous flammability) generated by burning the waste accumulated in the lower part of the furnace by controlling the combustion state so as to form a “conditioning layer”, “combustion layer”, and “ash layer” It is common to have a mechanism to reburn the material) in the upper part of the furnace.

Recently, the amount of combustion air supplied is 0.2 to 0.8 times the theoretical amount of air, and the waste is dried and dried at a high temperature in a substantially oxygen-free state between the combustion layer and the ash layer. A method of supplying combustion air that forms a "carbonized layer" in which thermal decomposition is promoted has also been proposed (see, for example, Patent Document 1 below).

Japanese Patent No. 4593688

In the combustion air supply method described in Patent Document 1, the supply amount of the combustion air is changed from 0.2 to the theoretical air amount by changing the supply amount of the combustion air according to the thickness of the deposited layer. Maintain 0.8 times. However, when the amount of combustion air supplied is changed, the flow of combustion air from the lower part to the upper part of the deposited layer becomes uneven, or local blow-through occurs, resulting in an unstable combustion state. was there.

The present invention was developed in view of the above technical problems, and an object of the present invention is to provide a novel combustion control method capable of continuing a stable combustion state of a vertical refuse incinerator.

A combustion control method of the present invention for solving the above technical problem is to inject waste into a furnace and burn the waste while supplying combustion air from a lower portion of a deposition layer formed by the injected waste. A combustion control method in a vertical refuse incinerator that incinerates waste by sequentially discharging the incineration ash from the bottom of the furnace, and after maintaining the supply amount of combustion air within a certain range, The combustion state of the waste is controlled by changing the oxygen concentration of the air (hereinafter referred to as the "control method of the present invention").

In the control method of the present invention, it is a preferred embodiment that the oxygen concentration of the combustion air is changed according to the flow rate or the temperature of the exhaust gas generated by the combustion of the waste.

In the control method of the present invention, it is a preferable aspect that the oxygen concentration of the combustion air is changed according to the amount of boiler water evaporation of the waste heat boiler attached to the vertical refuse incinerator.

In the control method of the present invention, it is a preferable aspect that the oxygen concentration of the combustion air is changed by recirculating the exhaust gas and mixing it with the combustion air.

According to the present invention, a stable combustion state of a vertical refuse incinerator can be continued.

FIG. 1 is a schematic diagram schematically showing an embodiment of an incineration plant equipped with a vertical refuse incinerator for carrying out the control method of the present invention. FIG. 2 is a block diagram showing an example of a control device for executing the control method of the present invention. FIG. 3 is a flowchart showing a control procedure of the control device. FIG. 4 is a block diagram showing another example of the control device for executing the control method of the present invention. FIG. 5 is a flowchart showing a control procedure of the control device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments.

<Vertical refuse incinerator 1>
The control method of the present invention is a combustion control method in the vertical refuse incinerator 1 as shown in FIG. In the vertical refuse incinerator 1, the waste W is charged into the furnace 11, and the waste W is burned while supplying combustion air from the lower part of the deposition layer W1 formed by the injected waste W. The incinerator employs a combustion method in which waste W is incinerated by sequentially discharging incineration ash from the bottom of 11.

-Combustion air supply line (AL)-
In this embodiment, the combustion air (primary combustion air) is supplied through the combustion air supply line (AL) shown by the solid line in the figure. One end of the combustion air supply line (AL) is connected to an air pushing fan (FA), and the other end is a pipe arranged to reach a lower portion of the furnace 11 of the vertical refuse incinerator 1. A combustion air valve (VA) that determines the supply amount of combustion air is provided in the middle of the pipeline. Further, a first flow meter (A1) for measuring a flow rate (primary flow rate) of the combustion air generated by driving the air pushing fan (FA) is provided upstream of the combustion air supply line (AL). It is provided and downstream of the combustion air supply line (AL) for measuring the flow rate (secondary flow rate) of the combustion air immediately before being introduced into the vertical refuse incinerator 1. A dual flow meter (A2) is provided.

-Exhaust gas line (GL)-
In the present embodiment, the combustible gas generated by the combustion of the waste W is first burned in the main combustion chamber 111, and then the gas that has passed through the rectifying device 13 is completely burned in the reburning chamber 112. The exhaust gas generated by the combustion process passes through the furnace outlet 12 and is transported along the exhaust gas line (GL) indicated by the dashed line in the figure. In this embodiment, the exhaust gas that has passed through the furnace outlet 12 is sequentially passed through the waste heat boiler 2, the economizer 3, and the bag filter 4, and is discharged to the atmosphere through the chimney C. Here, the waste heat boiler 2 plays a role of recovering heat energy of exhaust gas and generating steam. Further, the economizer 3 plays a role of preheating the boiler feed water by utilizing the residual heat of the exhaust gas. Further, the bag filter 4 plays a role of removing dust and the like contained in the exhaust gas. The flow of the exhaust gas is formed by a gas attraction fan (FG) provided between the bag filter 4 and the chimney C. In the present embodiment, a gas thermometer 14 for measuring the temperature of the exhaust gas passing through the furnace outlet 12 is provided in the furnace outlet 12, and the flow rate of the exhaust gas passing through the furnace outlet 12 is measured. A gas flow meter 15 for doing so is provided in the exhaust gas line (GL).

-Steam line (SL)-
As described above, the vertical refuse incinerator 1 according to the present embodiment is provided with the waste heat boiler 2, and the steam generated with the evaporation of the boiler water is passed through the steam line (SL) shown by the dotted line in the figure. Will be transported. In the present embodiment, the steam line (SL) is provided with a steam flow meter 21 for measuring the evaporation amount of boiler water.

-Exhaust gas recirculation line (RL)-
An exhaust gas recirculation line (RL) shown by a two-dot chain line in the drawing plays a role of recirculating a part of the exhaust gas passing through the exhaust gas line (GL) and joining it with the combustion air supply line (AL). In the present embodiment, one end of the exhaust gas recirculation line (RL) is connected between the gas induction fan (FG) and the chimney C in the exhaust gas line (GL), and the other end thereof is the combustion air supply line (AL). ) Is a pipe connected between the first flow meter (A1) and the second flow meter (A2). An exhaust gas recirculation fan (FR) is provided in the exhaust gas recirculation line (RG), and is transported through the exhaust gas recirculation line (RG) by driving the exhaust gas recirculation fan (FR). An exhaust gas stream is formed. A recirculation valve (VR) that determines the recirculation amount of exhaust gas is provided upstream of the exhaust gas recirculation fan (FR).

<Control method of the present invention>
Hereinafter, the execution of the control method of the present invention will be described using the vertical refuse incinerator 1 having the above configuration.
In the vertical refuse incinerator 1 having the above-mentioned configuration, the oxygen concentration of the combustion air can be changed by recirculating the exhaust gas and mixing it with the combustion air. Further, the supply amount of the combustion air can be measured by the first flow meter (A1) and the second flow meter (A2) provided in the combustion air supply line (AL). By adjusting the openings of the combustion air valve (VA) and the recirculation valve (VR) according to the supply amount of air, the supply amount of combustion air can be maintained within a certain range.

Therefore, according to the vertical refuse incinerator 1, the combustion state of the waste W is controlled by changing the oxygen concentration of the combustion air while maintaining the supply amount of the combustion air within a certain range. The inventive control method can be implemented.

The control method of the present invention may be performed manually, but the temperature of the exhaust gas measured by the gas thermometer 14, the flow rate of the exhaust gas measured by the gas flow meter 15, or the boiler. It is preferable to carry out the automatic control in which the combustion conditions are automatically determined according to the factors generated by the combustion such as the evaporation amount of water. This automatic control is, for example, as shown in FIG. 2, measured by a storage unit 51 that stores a planned temperature of the exhaust gas and a planned flow rate of the exhaust gas (hereinafter, referred to as a “planned value”) and the gas thermometer 14. The calculating means 52 for comparing the exhaust gas temperature and the exhaust gas flow rate measured by the gas flow meter 15 (hereinafter referred to as “actual measurement value”) with a predetermined value to derive the optimum oxygen concentration of the combustion air. And a control means 53 for instructing the opening degree of the combustion air valve (VA) and the recirculation valve (VR) according to the derived oxygen concentration.

As shown in the flowchart of FIG. 3, the control device 5 uses the gas thermometer 14 (or the gas flow meter 15) after a lapse of a certain time (S2) from the start of operation of the vertical refuse incinerator 1 (S1). The temperature (or flow rate) of the exhaust gas is measured (S3). For convenience of explanation, the air pushing fan (FA), the gas attraction fan (FG), and the exhaust gas recirculation fan (FR) are selected according to the start of operation (S1) of the vertical refuse incinerator 1. The drive shall start.

The calculation unit 52 compares the planned value stored in the storage unit 51 with the actually measured value, and derives the optimum oxygen concentration of the combustion air (S4). More specifically, if the temperature (flow rate) of the exhaust gas is lower than a predetermined value, a high oxygen concentration is determined, and if it is high, a low oxygen concentration is determined.

The control means 53 commands the opening degree of the combustion air valve (VA) and the recirculation valve (VR) based on the determined oxygen concentration (S5). More specifically, if the determined oxygen concentration is higher than the current oxygen concentration in the combustion air, the opening degree of the combustion air valve (VA) is increased, and the recirculation valve (VR) is opened accordingly. Turn down. On the contrary, if the determined oxygen concentration is lower than the current oxygen concentration of the combustion air, the opening degree of the combustion air valve (VA) is lowered and the opening degree of the recirculation valve (VR) is increased accordingly. .. As a result, the amount of combustion air supplied is maintained within a certain range.

After that, when a certain period of time has passed (S2), the control procedure of measuring the exhaust gas temperature (flow rate) (S3) and subsequent steps is repeated.

As described above, according to the control method of the present invention, in which the combustion state of waste is controlled by changing the oxygen concentration of the combustion air while maintaining the supply amount of the combustion air within a certain range, With respect to the flow of the combustion air from the lower part to the upper part, there is no deviation due to the change in the supply amount of the combustion air, and local blow-through does not occur, so that the combustion state is stably maintained.

Further, since all of the combustion air can be replaced with the recirculated exhaust gas, when the operating condition of the incinerator is abnormal, the exhaust gas with an oxygen concentration of 10% or less should be used to quickly extinguish the inside of the furnace. You can also

Note that, in the present embodiment, the oxygen concentration of the combustion air is changed by recirculating the exhaust gas and mixing with the combustion air, but the oxygen concentration changing means is not limited to that by recirculating the exhaust gas. .. For example, the oxygen concentration of the combustion air may be changed by mixing nitrogen, carbon dioxide or external exhaust gas with the air. The oxygen concentration of the combustion air is preferably changed within the range of 15 to 21%.

Further, in the present embodiment, the oxygen concentration of the combustion air is determined according to the temperature or flow rate of the exhaust gas generated by the combustion of the waste W, but the factor for determining the oxygen concentration is the exhaust gas temperature. Or it is not limited to the flow rate.

For example, the block diagram shown in FIG. 4 is a control device 5 that determines the oxygen concentration of combustion air according to the amount of boiler water evaporation of the waste heat boiler 2. The control device 5 compares the estimated evaporation amount of the boiler water measured by the steam flow meter 21 with the storage means 51 that stores the estimated evaporation amount of the boiler water, and determines the optimum oxygen concentration of the combustion air. And a control means 53 for instructing the opening degree of the combustion air valve (VA) and the recirculation valve (VR) according to the derived oxygen concentration.

In the control device 5, the storage means 51 further stores a planned supply amount of combustion air, and the computing means 52 uses the first flow meter (A1) and the second flow meter (A2). The measured supply amount of combustion air is compared with the planned supply amount, and the control means 53 changes the opening degree of the combustion air valve (VA) and the recirculation valve (VR) according to the difference. It is designed to give orders.

As shown in the flowchart of FIG. 5, the control device 5 measures the evaporation amount of the boiler water with the steam flow meter 21 after a certain time has elapsed (S2) from the start of operation of the vertical refuse incinerator 1 (S1). Yes (S9).

The calculation unit 52 compares the planned evaporation amount stored in the storage unit 51 with the measured evaporation amount, and derives the optimum oxygen concentration of the combustion air (S4). More specifically, if the evaporation amount of boiler water is lower than expected, a high oxygen concentration is determined, and if it is high, a low oxygen concentration is determined.

The control means 53 commands the opening degree of the combustion air valve (VA) and the recirculation valve (VR) based on the determined oxygen concentration (S5).

Further, the control device 5 measures the supply amount of the combustion air by the first flow meter (A1) and the second flow meter (A2) (S6), and the arithmetic unit 52 supplies the measured combustion air supply. The quantity is compared with the planned supply quantity (S7).

When the measured supply amount of combustion air is not within the range of the planned supply amount, the control means 53 commands the change of the opening degree of the combustion air valve (VA) and the recirculation valve (VR). (S8). More specifically, when the measured supply amount of combustion air exceeds a predetermined value, one or both of the combustion air valve (VA) and the recirculation valve (VR) are opened. If the measured supply amount of combustion air is less than the predetermined value, either one of the combustion air valve (VA) or the recirculation valve (VR) or both of them are opened.

After that, when a certain period of time has passed (S2), the measurement procedure of the boiler water evaporation amount (S9) and the following control procedure are repeated.

As described above, based on the determined oxygen concentration, after instructing the opening degree of the combustion air valve (VA) and the recirculation valve (VR) (S5), according to the measured supply amount of combustion air. Then, according to the control method of the present invention, an instruction to change the opening degree of the combustion air valve (VA) and the recirculation valve (VR) is made (S8). The combustion state can be further stabilized.

By the way, in the present embodiment, for convenience of explanation, the single measurement items of "exhaust gas temperature", "exhaust gas flow rate", and "evaporation amount of boiler water" are used as factors for re-determining combustion conditions. The oxygen concentration of the combustion air may be determined in combination.

The present invention can be implemented in various other modes without departing from the spirit or the main features thereof. Therefore, the above embodiments are merely examples in all respects, and should not be limitedly interpreted. The scope of the present invention is defined by the claims and is not bound by the text of the specification. Further, all modifications and changes belonging to the equivalent range of the claims are within the scope of the present invention.

INDUSTRIAL APPLICATION This invention is used suitably as a control means which stabilizes the combustion state of a vertical refuse incinerator.

1 Vertical Waste Incinerator 11 Furnace 12 Furnace Outlet 13 Rectifier 14 Gas Thermometer 15 Gas Flow Meter 2 Waste Heat Boiler 21 Steam Flow Meter 3 Economizer 4 Bag Filter 5 Controller 51 Storage Means 52 Calculation Means 53 Control Means AL For Combustion Air supply line GL Exhaust gas line SL Steam line RL Exhaust gas recirculation line W Waste W1 Deposit layer

Claims (4)

The waste is incinerated by injecting the waste into the furnace, burning it while supplying combustion air from the bottom of the sediment layer formed by the injected waste, and sequentially discharging the incineration ash from the bottom of the furnace. A combustion control method in a vertical refuse incinerator to be treated, comprising:
After maintaining the supply of combustion air within a certain range,
A combustion control method comprising controlling the combustion state of waste by changing the oxygen concentration of combustion air. The combustion control method according to claim 1, wherein
A combustion control method for changing the oxygen concentration of combustion air according to the flow rate or temperature of exhaust gas generated by combustion of waste. The combustion control method according to claim 1,
A combustion control method for changing the oxygen concentration of combustion air according to the amount of boiler water evaporation of a waste heat boiler attached to the vertical refuse incinerator. The combustion control method according to any one of claims 1 to 3,
A combustion control method for changing the oxygen concentration of combustion air by recirculating exhaust gas and mixing it with combustion air.

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