JPH0335580B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a control device and a control method for detecting the flame temperature of a pulverized coal burner to bring it into an optimal combustion state.

<Prior art and its problems> No matter what the rate of fuel supply, the flame temperature of a burner that receives air and pulverized coal is theoretically highest when it is in the relationship of theoretical chemical equivalence. This is the result. Excess air or excess fuel in the combustion zone will cause the flame temperature to be lower than the maximum flame temperature. In order to use fuel most efficiently, it is necessary to bring the flame as close to theoretical chemical equivalence conditions as possible. In addition, when the flame is rich (hereinafter referred to as "rich" when excess fuel is supplied), unburned fuel will corrode the furnace walls, and when the flame is lean, (The case of excess air is hereinafter referred to as "light"), which causes the problem of generation of toxic gases such as nitrogen oxides and sulfur oxides, depending on the oxidation conditions.

The temperature of the flame can be monitored using a light sensitive device such as a photodiode. Moreover, this makes it possible to display deviation from the optimum combustion state. However, this is due to excess fuel (point A in Figure 3) or excess air (point 3 in Figure 3).
It is not intended to indicate whether the

With gas burners and heavy oil burners, it is easy to determine whether there is too much fuel or too little fuel because the flow rate can be determined with a flow meter and can be confirmed by the meter. However, with pulverized coal, it takes 5 to 7 minutes to increase the amount of fuel after supplying coal to the mill, and it also changes depending on the amount of primary air and the quality of the coal, making it difficult to ascertain the exact amount supplied to each burner. It is not possible to determine whether the fuel is rich or light from the measured flame temperature.

An example of an invention that controls the combustion of a burner by sensing the radiant heat of the flame with a photoelectronic sensing device is disclosed in Japanese Patent Application Laid-Open No. 1986-
There is an invention in Publication No. 26. This is related to gas burners, and by activating the valves in the gas or air supply pipes, vibrations of the fluid flow occur at a frequency of about 1 Hz, and the electric signal of the flickering waveform of the flame is integrated, and the burner is in the optimal combustion state. The electric control device that stores the burner integral value for the optimal combustion state determines whether it is positive or negative by comparing it with the integral value when flame vibration is applied, and then controls the flow of gas or air to the burner. This is to control the supply amount. Furthermore, a signal with a 90° phase lag is added to the vibration waveform of the target burner using a comparator, and its output is set to zero to determine in advance whether there is excess fuel or insufficient fuel. (The same bulletin No. 3
(Page upper right column, lines 9 to 12) This Japanese Patent Application Laid-open No. 51-26 is a control means that is possible because it targets a gas fluid with a single homogeneous composition that does not contain solid fine particles such as pulverized coal. This is what is disclosed. This means cannot be applied to a pulverized coal burner, nor does it suggest the present invention.

<Object of the invention> The present invention detects flame temperature to easily and automatically determine whether a burner burning pulverized coal is running out of fuel or air. The purpose of the present invention is to provide a method and device for controlling the system.

<Summary of Means> In short, the present invention provides a burner control device that controls combustion of a burner supplied with a mixed fluid of pulverized coal and air based on its flame temperature, and a flame temperature detection device that detects the flame temperature and outputs a temperature signal. , a device for supplying agitated pressurized air to a conduit supplying the mixed fluid to the burner, and when the mixed fluid is disturbed, the flame temperature value reaches a flame temperature value under the optimum condition for combustion due to the disturbance; a comparison device that compares the time required for pulverized coal to a reference time set in the device and determines whether the concentration of pulverized coal in the mixed fluid is high or low based on whether the difference is positive or negative; and a comparison device that reduces the difference. This is a pulverized coal burner control device characterized by comprising a device for controlling the supply amount of pulverized coal or air.

The present invention also provides a method for controlling a burner supplied with a mixed fluid of pulverized coal and air, in which the detected flame temperature signal value of the burner is compared with a reference flame temperature value under optimal combustion conditions in a comparison device; Also, the time required for the burner flame temperature to reach the reference temperature after being disturbed by pressurized air as a disturbance means provided in the pipe line that supplies the mixed fluid to the burner is plus or minus the reference time stored in the device. The pulverized coal burner control method is also characterized in that it is determined whether the pulverized coal concentration is high or low, and the supply amount of pulverized coal or air is controlled by the command signal of the comparison device so as to reduce the difference. .

<Embodiment> An embodiment of the invention will now be described with reference to the accompanying drawings, which are shown somewhat diagrammatically. FIG. 1 shows a pulverized coal combustion device and its control device, and FIG. 2 is a perspective view of a vortex amplifier installed in a duct that supplies pulverized coal to a burner.

The burner 1 is one of a plurality of burners (not shown) of substantially the same type attached to a furnace in which fuel is burned, and is attached to a furnace wall 2. A mixture of primary air and pulverized coal is supplied to the burner 1 via a pipe 3. Secondary air is supplied from duct 4,
The flow rate of the secondary air is controlled by a trimming device (adjusting device such as a damper) 5.

A passage device 6 is provided through the furnace wall 2 to define a light path so that a photodiode device (flame temperature sensing device) 6a can "audit" the flame of the burner 1. The passage device 6 has a photodiode device 6a depending on the flame temperature of the other burner.
This is a device that has the effect of preventing the effects of The photodiode device 6a is designed to output a signal based on the color (brightness) of the flame. The signal emitted by the photodiode device 6a is passed through a tuned amplifier 7 to a detector circuit 8 and then to a comparator 9.

The pipe 3 includes an eddy current amplifier 10, which can change the pulverized coal content ratio in the mixed fluid of pulverized coal and air flowing inside the pipe 3. The eddy current amplifier 10 includes a drum 11 coaxial with the pipe 3, so that in implementation the drum 11 forms a localized enlargement of the pipe 3.
The duct 12 is located in the direction of the outer wall of the drum 11 and opens into the drum 11. Therefore, the gust of pressurized air supplied from this duct 12 (hereinafter this agitated pressurized air will be simply referred to as blast air) instantaneously reduces the fuel flow rate to the burner, and first lowers the current flow rate value at that time. However, the delayed fuel flow into the reactor then increases, instantaneously increasing the current flow value.

The duct 12 leads to the eddy current amplifier 10 from an air source 15 controlled by a pulse generator 16 . The pulse generator 16 emits pulses at the correct frequency, for example every 1/2 second or every 1 or 2 seconds, which pulses are simultaneously sent to the air source 15 as well as to the comparison device 9. The air source 15 is pulsed to actuate a solenoid valve (not shown) connected to the outlet of the air source 15 to direct blast air as agitated pressure air to the vortex amplifier 10. This air source 1
5. Solenoid valve and duct 12 form a device for supplying agitation pressure air.

<Operation> Next, the operation when blasting (the blast air itself or the supply operation will be simply referred to as blasting hereinafter) will be described. When blasting, unless the fuel is extremely light or rich, it first becomes light or becomes increasingly pale, and then becomes rich, as shown in curve A or B in Figure 4, and in each case, the optimum point is somewhere in the middle of the process. Pass through combustion conditions. The signal from the photodiode device 6a detects changes in the flame temperature and outputs a signal accordingly, so that when the optimum combustion condition is passed, a signal corresponding to the maximum temperature is generated. The present invention grasps this characteristic and determines the difference between the time required to reach the maximum temperature value shown in FIG. 4 and the reference time, and determines whether it is dark or light based on the plus or minus of the time.

Furthermore, before describing the implementation and operation of the present invention, the operation of the mixed fluid and pulverized coal in the eddy current amplifier 10 will be considered. In FIG. 2, the diameter of the eddy current amplifier 10 provided in the pipe 3 through which the mixed fluid flows is larger than the diameter of the pipe 3, and the flow velocity of the mixed fluid is reduced accordingly at this point.
A blast of pressurized air is blown from the duct 12 in a tangential direction to the outer diameter of the eddy current amplifier 10 at high speed to form a swirling flow, so that the pulverized coal is subjected to centrifugal force and is separated and collected inside the amplifier, where the mixed fluid flows to the burner. The pulverized coal content concentration of the pulverized coal content decreases, and in addition, air equivalent to the blast air is added to the flow, further reducing the pulverized coal content concentration.

As shown in Figure 4, when the pulverized coal concentration is high, the concentration decreases from the time of blasting at the time of flame temperature measurement and approaches the optimum combustion concentration, and the flame temperature rises until the optimum combustion temperature is reached. (Ts). If this is plotted as a graph of flame temperature and elapsed time, it will become one rising curve A, and the time it takes to reach the optimum combustion temperature t ₁
will be relatively short.

On the other hand, if the pulverized coal concentration is light and lower than the optimum combustion temperature (Tm in Figure 4), when blast air is supplied, the pulverized coal will be separated by centrifugal force and its concentration will become lighter. Its concentration decreases and the flame temperature also decreases. When the blast air is stopped, the separated pulverized coal returns to the mixed fluid and increases the concentration of fuel flowing to the burner, and the flame eventually reaches the optimum combustion temperature (Ts). Considering this in terms of a graph of flame temperature and elapsed time, once the flame temperature decreases, it becomes curve B, which is a concave curve connected to an ascending curve. It can be seen that the time is t ₂ and the pulverized coal concentration is low. Therefore, by setting a standard time t ₀ between the above-mentioned required time for dark and the required time for light, and storing this in the comparator 9, even if the difference between the specified time and the required time is positive, Bao,
If it is negative, it can be judged as light. Based on this judgment, it is sufficient to increase or decrease fuel, decrease or increase air, and bring the difference closer to zero.

The command to the comparison device 9 between the signal to start blowing the blast air and the subsequent signal that the flame has passed the optimum combustion temperature is transmitted even if there is a delay in sending the command to the comparator 9.
The flame conditions can be reproduced and displayed by the next pulse transmission.

The comparison device 9 is connected to the trimming device 5 such as a damper, and automatically adjusts the supply of the amount of secondary air in a direction that matches the basic conditions as the optimum combustion conditions.

When blast air is supplied to the eddy current amplifier 10 at a regular frequency, the accompanying change in flame temperature occurs twice as often as the blast air supply frequency (frequency) because there is a maximum and minimum indicated temperature. . Therefore, the tuned amplifier 7 is adjusted to receive signal changes derived from the blast air to the eddy current amplifier 10, and not to receive signals from other sources. Furthermore, even if two or more burners are installed close to each other, the frequency of blast air supplied to the eddy current amplifier associated with each burner is set to be different from each other in order to prevent misidentification. This ensures that the tuned amplifier of either burner is not responsive to frequency signals from other closely located burners.

When using the device described above, it may be envisaged to regularly interrupt the flow of fuel to the burner and even to operate it intermittently.

By using the vortex amplifier described above, the fuel flow to the burner can be subjected to sudden changes. This changing means may be other means than the above.

For example, as shown in the figure (Figure 2), instead of providing a part that becomes an enlarged passage, the air that acts as resistance and interferes with the pipe is installed on the outer peripheral wall of a type of pipe whose diameter does not change, so that it blows out in the tangential direction of its cross-sectional circle. It is also possible to introduce agitation air (blast air) into a constriction part that makes the tube diameter smaller than the pipe diameter, and to flow the blast in the direction tangential to the outer circumference of the cross section. In addition, regardless of the diameter of the pipe introducing the air blast, the direction of the blast air is determined so that a vortex that disturbs the flow of fuel is formed by rebounding from the opposite wall of the blast air inlet of the pipe. ,
The blast may be such that it traverses the pipe.

Furthermore, a strike plate (collision plate) may be provided in the vicinity of the burner and at the bend portion where the flow direction is changed, and the blast air may be caused to flow from this strike plate in the downstream direction of the flow and along the axis of the pipe. In any case, the direction in which the blast air is supplied may be either the circumferential tangential direction of the pipe or the direction transverse to the circumferential line of the pipe.

Generally, disturbances in the flow of fuel through the pipe 3 should be generated near the outlet of the pipe, but in relation to other functional elements associated with the fuel supply passage, disturbances such as the blast air outlet may be generated upstream from the vicinity of the pipe exit. The means may be located.

The effect of the eddy current amplifier described above is first to make the flame appropriately light or dense. It is also possible to use an alternative to this amplifier which first makes the flame too thick and then makes it too light.

<Effects of the Invention> When the device according to the present invention is installed and operated in conjunction with a furnace equipped with a plurality of burners each connected to a pipe branched from a common supply source, significant effects can be obtained. be.

This is because the fuel distribution in lines branching from a single source cannot generally be balanced, and the implementation of the invention corrects this disadvantage and allows for optimal combustion control of individual burners. It is. As a result, the fuel distribution to each burner is made appropriate, and the combustion efficiency of the burners and, by extension, of the boiler can be significantly improved.

As can be understood from the above explanation, the purpose of this invention is to find the peak (highest point) of the flame temperature, not to find the absolute value of the flame temperature. will not decrease.

[Brief explanation of drawings]

FIG. 1 is a system diagram schematically showing an apparatus according to the present invention, FIG. 2 is a perspective view of an eddy current amplifier, and FIG.
The figure is a diagram of air-fuel ratio and flame temperature, and FIG. 4 is a diagram illustrating the relationship between reference time for determining the concentration of fuel. 1...burner, 2...furnace wall, 3...pipe, 4
... Duct, 5 ... Trimming device, 6 ... Passage device, 6a ... Photodiode device (flame temperature detection device), 7 ... Tuned amplifier, 8 ... Detection circuit,
9... Comparison device, 10... Eddy current amplifier, 11...
...Drum, 12...Duct, 15...Air source, 1
6...Pulse generator.

Claims (1)

[Scope of Claims] 1. A burner control device that controls combustion of a burner supplied with a mixed fluid of pulverized coal and air at its flame temperature, comprising: a flame temperature detection device that detects flame temperature and outputs a temperature signal; a device for supplying agitated pressurized air to a pipe that supplies mixed fluid to A comparison device that compares the time with a reference time set in the device and determines whether the concentration of pulverized coal in the mixed fluid is high or low based on whether the difference is positive or negative, and a comparison device that reduces the difference. A pulverized coal burner control device comprising: a device for controlling the supply amount of pulverized coal or air; 2. The pulverized coal burner control device according to claim 1, further comprising a pulse generator that generates a signal that automatically disturbs the flow of fuel supplied to the burner at regular intervals. 3. Claim 1, characterized in that it has a pipe through which pulverized coal accompanying air flows to the burner, and a device for discharging and agitating the blast air so as to cross the flow direction of the fuel flowing inside the pipe.
The pulverized coal burner control device according to item 1 or 2. 4. The blast air is supplied in a tangential direction to the cross-sectional circumference of the pipe, and the diameter of the part of the pipe that receives the blast air is made larger than the pipe diameters of the upstream and downstream parts of the fuel flow at that part. A pulverized coal burner control device according to claim 3. 5. The pulverized coal burner according to any one of claims 1 to 4, characterized in that a pipe is provided for connecting the burner and a secondary air source, and an air flow rate control device is provided to this pipe. Control device. 6. Claim 1, wherein the flame temperature detector is a photodiode device.
The pulverized coal burner control device according to any one of items 5 to 6. 7 The temperature of the flame when the burner is in the optimum combustion state is used as a reference temperature signal, which is stored, and compared with the temperature signal value measured by the photodiode to control the fuel supply amount or air supply amount to the burner. Claims 1 to 6 are characterized in that a device for issuing a command signal for controlling the means is provided.
The pulverized coal burner control device according to any one of paragraphs. 8 In a method for controlling a burner that receives a mixed fluid of pulverized coal and air, the detected flame temperature signal value of the burner is compared with a reference flame temperature value under optimal combustion conditions in a comparison device, and the mixture is supplied to the burner. The pulverized coal concentration depends on whether the time from when the burner flame temperature reaches the reference temperature after being disturbed by the pressure air as a disturbance means installed in the pipe that supplies the fluid is plus or minus from the reference time stored in the device. A method for controlling a pulverized coal burner, characterized in that the amount of pulverized coal or air supplied is controlled by a command signal from the comparator so as to reduce the difference. 9. The pulverized coal burner control method according to claim 8, characterized in that the flow of fuel to the burner is disturbed at predetermined time intervals. 10. The pulverized coal burner control method according to claim 9, characterized in that the disturbance intervals of the fuel flow to the burners are made different from each other in consideration of the operation of adjacent burners. 11. The pulverized coal burner control method according to claims 8 to 10, characterized in that the set flame temperature signal is input to the comparison device as a temperature signal of a flame in an optimal combustion state.