JP2001065862A - Coal runout detector of pulverized coal supplying system and method for detecting it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an unexpected overall stop or decrease in an operating efficiency in a boiler of a pulverized coal supply destination by setting a main steam pressure of a boiler to a first index, setting a plurality of pieces of measurement information at a periphery of a mill, and detecting a coal runout state from their states. SOLUTION: The coal runout detector 11 judges whether it is a coal runout state or not based on five pieces of measurement information (indexes) acquirable during operating of a boiler 9 and the pulverized coal supplying system. The first index is a main steam pressure P of steam supplied from the boiler 9. If the steam pressure P is lowered to a set value or less, it is considered that the condition for coal runout detection is satisfied with respect to the first index. The second index is an outlet gas temperature T of a mill 7. The third index is a pressure difference ΔP1 in a furnace of the boiler 9 in the mill 7. Finally, the fifth index is a differential pressure ΔP2 between above and below a mill table 75.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a missing coal detecting apparatus for detecting an abnormally low coal quantity state, that is, a so-called missing carbon state, in a pulverized coal supplying apparatus for pulverizing coal and supplying it to a boiler, and a detecting method therefor. About.

[0002]

2. Description of the Related Art In general, pulverized coal is widely used as a fuel for a combustion burner used in a power generation boiler or the like. In this case, usually, a pulverized coal supply device that pulverizes coal into pulverized coal and pneumatically feeds it to combustion equipment is used. FIG. 4 is a diagram showing a flow of a general pulverized coal supply device for supplying pulverized coal to a power generation boiler.

As shown in FIG. 4, coal stored in a coal yard 1 is stored in a hopper 3 by a belt conveyor 2 or the like. The coal in the hopper 3 is sent out from the chute 4 to the coal feeder 5 according to the supply speed of the coal feeder 5 installed below the hopper 3. The coal feeder 5 is configured by a so-called belt feeder or the like, and has a function of cutting out a certain amount of coal according to the number of rotations. The coal cut from the coal feeder 5 falls in the coal feed pipe 6 and enters the mill 7.
The coal is pulverized by a mill 7 into pulverized coal, and is pneumatically fed to the boiler 9 through the pulverized coal supply pipe 8 by hot air.

[0004] The equipment receiving pulverized coal from such a pulverized coal supply device is often an important equipment such as a power boiler that cannot be easily stopped due to a trouble. Therefore, in such a case, a plurality of (3 to 4) pulverized coal feeders are usually installed in parallel to avoid danger. That is, a plurality of lines from the belt conveyor 2 to the pulverized coal supply pipe 8 in FIG. 4 are arranged.

On the other hand, even within a single pulverized coal feeder, it is necessary to take measures for preventing troubles and detecting them at an early stage. One of the measures is to detect missing coal.
A state in which large stones and the like mixed in the coal are clogged by one of the flows in the above-described pulverized coal supply device and the coal is not normally supplied is referred to as a lack of carbon state. The stones that cause the lack of coal are temporarily removed before being supplied from the coal yard 1. However, the remaining stones that have not been completely removed are removed by the lower part of the hopper 3, the chute 4, or the coal feeder 5 or the like. May be clogged.

In this state, the supply amount of the pulverized coal naturally drops or stops, which has a serious effect on the equipment at the supply destination, and furthermore, if this state is left unchecked, the entire equipment stops. Stop). Therefore, particularly when the pulverized coal supply device is used for equipment of high importance such as a power generation boiler, it is essential for the operation of the equipment to detect the state of lack of coal at an early stage and eliminate the state.

Conventionally, the detection of the lack of carbon has been performed mainly based on one of the following three indices. One of them is a judgment based on the sound of the shoot 4 shown in FIG. This means that the sound in the chute 4 is measured using an acoustic sensor (AE in FIG. 4), and when the loudness is smaller than a preset threshold value, it is determined that a lack of carbon state has occurred. It is. This utilizes a phenomenon in which the sound generated by reducing the amount of coal moving in the chute 4 also decreases.

The second index is based on a paddle switch (PS in FIG. 4) provided near the exit of the coal feeder 5, and FIG. 5A illustrates the principle of the paddle switch. FIG. As shown in part a of the figure, when a proper amount of coal is supplied, the coal moves on the coal feeder 5 while maintaining a constant height, and the paddle switch (PS in FIG. 5)
Is pushed up to the position (2) shown in the figure. However, when the lack of coal state occurs, the amount of supplied coal decreases, the height of section a decreases, and the paddle switch approaches the position (1) shown in the figure. Therefore, when the angle of the paddle switch becomes smaller than the set threshold value, it is determined that the state of lack of carbon is present.

The third index is the differential pressure between the coal feeder 5 and the mill 7 (ΔP _{3 in} FIG. 4). In a state where coal is normally supplied, a pressure difference occurs between the coal feeder 5 and the mill 7 in accordance with the flow of coal flowing from the coal feeder 5 to the mill 7 via the coal feed pipe 6. When the amount of coal flowing is reduced and the amount of flowing coal decreases, the differential pressure also decreases accordingly. Therefore, this differential pressure (ΔP _{3 in} FIG. 4) is measured. to decide.

Conventionally, the state of lack of carbon has been detected based on the above three measurement information.

[0011]

However, in some cases, the above-described conventional lack of carbon detection method cannot detect the state of lack of carbon at an early stage. FIG. 5B is a diagram showing an example of a case in which the detection based on the paddle switch (PS in the figure) of the coal feeder 5 does not determine that there is a lack of coal even though it is actually in a lack of carbon. is there. This example is a case where the stone shown in part b of the figure has been caught, and in such a case, although the supply of coal has been interrupted due to the stone, it is in a state of lack of coal Since the paddle switch is in the normal position, the missing carbon state is not detected.

On the other hand, the acoustic sensor of the chute 4 (A in FIG. 4)
E) and the method based on the pressure difference between the coal feeder 5 and the mill 7 (ΔP _{3 in} FIG. 4), it is difficult to reliably detect the lack of carbon with one threshold value used as the criterion. Was. The measurement value used as a judgment index, even if it is not an abnormal state, slightly fluctuates depending on the operating condition of the equipment, so if the threshold is strict, the number of false alarms will increase, while if the threshold is too loose, The lack of carbon cannot be detected early. As the number of false alarms increases, the load on the equipment is reduced or a manual inspection is performed each time, resulting in impeding efficient operation of the equipment.

It is also possible to monitor and monitor a place where frequent clogging of stones or the like causing lack of coal occurs, but this is not a feasible solution due to problems of certainty and manpower.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pulverized coal feeder that detects a lack of carbon state early and surely, and reduces accidental stoppage and a decrease in operating efficiency of a boiler to which pulverized coal is supplied. It is an object of the present invention to provide a missing carbon detecting device and a detecting method thereof.

[0015]

According to one aspect of the present invention, a main steam pressure of a boiler is used as a first index, and a plurality of pieces of measurement information around a mill are used as a second information. As an index, it is to detect a missing carbon state from those states. Therefore, according to the present invention, it is possible to early and surely detect a lack of carbon state, and it is also possible to reduce a decrease in operating efficiency due to a false alarm.

In order to achieve the above object, another aspect of the present invention is to provide a pulverized coal supply device for pulverizing coal with a mill and supplying the generated pulverized coal to a boiler to detect a missing carbon state. In the charcoal detection device, when the main steam pressure of the boiler is larger than a preset value, it is determined that the state is not a missing carbon state, and when the main steam pressure is smaller than the preset value, It is characterized in that it is determined whether or not there is a missing carbon based on measurement information obtained from the mill and the periphery of the mill. Therefore, according to the present invention, it is possible to detect the missing carbon state early and reliably.

Further, in the above-mentioned invention, a preferable aspect is that the measurement information includes: an outlet gas temperature of the mill;
A load of a motor for rotating a table provided in the mill, a differential pressure between the inside of the mill and a furnace inside the boiler, and a portion above and below the table inside the mill. And when at least one of the measurement information is in a state corresponding to the lack of carbon, it is determined that the lack of carbon is present.

Further, in the above invention, another aspect is as follows.
When the plurality of pulverized coal supply devices provided for the boiler are controlled under the same conditions, the measurement information in the state corresponding to the missing coal state is equivalent in the plurality of pulverized coal supply devices. If it is in the state, it is characterized in that it is not determined that it is in the missing carbon state. Therefore, false alarms can be reduced and driving efficiency can be improved.

Further objects and features of the present invention will become apparent from the embodiments of the present invention described below.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. However, such embodiments do not limit the technical scope of the present invention.
In the drawings, the same or similar components are denoted by the same reference numerals or reference symbols.

FIG. 1 is a diagram for explaining an embodiment of a missing carbon detection device to which the present invention is applied. The embodiment described here is a missing carbon detection device in a power generation boiler as shown in FIG. 1, and attempts to detect missing carbon by comprehensively judging a plurality of pieces of measurement information directly affected by missing carbon. Is what you do. The flow of the main apparatus shown in FIG. 1 is the same as that shown in FIG. 4 described in the related art, and the description of the process until the coal becomes pulverized coal and is supplied to the boiler 9 will be omitted here. .

The missing carbon detecting device 11 of the present embodiment comprises a boiler 9
And determining whether there is a missing carbon state based on five pieces of measurement information (indexes) that can be acquired during operation of the pulverized coal supply device. Each of these indexes will be described below.

The first index is the main steam pressure of steam supplied from the boiler 9 (P in FIG. 1). When the lack of carbon occurs and the combustion of the boiler 9 decreases, the steam pressure supplied from the boiler 9 decreases as a result. Therefore, an abnormal decrease in the main steam pressure (P in FIG. 1) does not necessarily indicate that a lack of carbon has occurred, but suggests a possibility of a lack of carbon, and conversely, the main steam pressure (see FIG. 1). If P) of 1) is normal, it is almost certain that no missing carbon has occurred. The main steam pressure (P in FIG. 1) is also an important value indicating whether or not the final result of the entire facility shown in FIG. 1 is in a predetermined state. ) Is the first condition in detecting missing carbon. If the main steam pressure (P in FIG. 1) falls below the set value, it is considered that the condition for detecting missing carbon has been satisfied for this index.

The second index is the outlet gas temperature of the mill 7 (T in FIG. 1). As described above, the pulverized coal pulverized by the mill 7 is sent to the boiler 9 via the pulverized coal supply pipe 8. As shown in FIG.
1 is sent to the mill 7 via an air heater 72, a hot air control valve 73, and a cool air control valve 74. Air heater 72
Is a heat exchanger for heating the atmosphere, and a hot air control valve 7
3 and the cold air control valve 74 are electric valves that adjust the amount of air and the atmosphere heated by the air heater 72 in order to supply hot air at a predetermined temperature to the mill 7.

The hot air blown to the mill 7 in this way is mixed with coal having a lower temperature than the hot air in the mill 7, so that the outlet gas temperature of the mill 7 in the pulverized coal supply pipe 8 (T in FIG. 1) Is lower than the warm air blown to the mill 7 in a normal state. However, when a missing carbon condition occurs,
Since the amount of coal supplied to the mill 7 decreases, the temperature of the hot air does not decrease as much as in a normal state, and thus the outlet gas temperature (T in FIG. 1) of the mill 7 increases. Therefore, the increase in the temperature of the gas at the outlet of the mill (T in FIG. 1) is used as one index for detecting missing carbon.

However, such a temperature rise does not last for a long time, and a temperature drop occurs. This is because an automatic control device for keeping the temperature of the mill outlet gas temperature (T in FIG. 1) constant is usually provided. This automatic control is performed when the temperature at the mill outlet gas (T in Fig. 1) is too high.
The opening degree of the hot air control valve 73 is reduced, and the cold air control valve 7 is opened.
4 is to increase the degree of opening to lower the temperature of the warm air sent into the mill 7 itself. In such a case,
Although the gas temperature at the mill outlet (T in FIG. 1) is the same as the normal case, the opening / closing degree of the hot air control valve 73 and the cold air control valve 74 (A ₁ and A _{2 in} FIG. 1) is different from the normal case. Therefore, it can be determined that the data is abnormal.

Accordingly, the temperature of the gas at the outlet of the mill (FIG. 1)
The condition for detecting missing carbon with respect to T) is that the temperature at the mill outlet gas (T in FIG. 1) itself becomes larger than a set value, or the opening / closing degree of the hot air control valve 73 and the cold air control valve 74 (FIG. 1).
Considered to A ₁ and A ₂₎ is satisfied by exceeding the predetermined range.

Next, a third index is a load of a mill motor 76 for rotating a mill table 75 provided in the mill 7. If the amount of coal supplied to the mill 7 is reduced due to the lack of coal, the load for grinding in the mill table 75 is reduced. Therefore, the load of the mill motor 76 can also be considered as one of direct indexes for detecting missing carbon. Since the mill motor 76 moves the mill table 75 at a constant rotation speed, a decrease in the load for rotation means that the current decreases under a constant voltage. Therefore, specifically, it is considered that the condition is satisfied when the current (I in FIG. 1) of the mill motor 76 is measured and the value falls below the set value.

The fourth index is a pressure difference (ΔP ₁ in FIG. ₁ ) between the inside of the mill 7 and the inside of the furnace of the boiler 9. As described above, the pulverized coal generated by the mill 7 is pneumatically fed to the boiler 9 through the pulverized coal supply pipe 8, and at that time, the pulverized coal supply pipe 8
Since a pressure loss occurs in the furnace, there is a corresponding pressure difference between the furnace of the mill 7 and the furnace of the boiler 9. When the amount of pulverized coal to be pneumatically reduced is reduced due to the lack of coal, the pressure loss is reduced, and the pressure difference between the inside of the mill 7 and the furnace of the boiler 9 (FIG. 1)
ΔP ₁ ) also decreases. Accordingly, the mill / furnace differential pressure (ΔP _{1 in} FIG. 1) is also used as one index, and it is considered that the condition is satisfied when the differential pressure falls below the set value.

Finally, the fifth index is a mill table 7
5 is the pressure difference above and below (ΔP _{2 in} FIG. 1). As described above, the warm air is sent from the fan 71 to the mill 7, and the warm air enters from below the mill table 75 and blows up the pulverized coal pulverized on the mill table 75, and the upper part of the mill 7 is blown up. Flows to In the process, mill table 75
Due to the pressure loss due to the coal and pulverized coal present above, a pressure difference occurs between the upper part and the lower part of the mill table 75. This mill table differential pressure (ΔP _{2 in} FIG. 1) also decreases when the amount of coal supplied due to lack of coal decreases.
Therefore, the mill table differential pressure (ΔP _{2 in} FIG. 1) is also used as one index, and it is considered that the condition is satisfied with respect to this index when the differential pressure falls below the set value.

Next, the determination of a missing carbon state in the missing carbon detecting device 11 will be described. FIG. 2 is a diagram showing a determination procedure in the missing carbon detection device 11 based on the five indices described above. First, it is determined whether or not a condition is satisfied with respect to the main steam pressure (P in FIG. 1). Here, if the condition is not satisfied, that is, if the main steam pressure (P in FIG. 1) maintains a predetermined value, it is determined that there is no missing carbon, and the determination ends. On the other hand, if the condition is satisfied, that is, if the main steam pressure (P in FIG. 1) is lower than a predetermined value, the process proceeds to the next step of evaluating other indices (step S1 in FIG. 2).

In the next step, the 4
Measurement information, mill outlet gas temperature (T in Fig. 1), mill motor current (I in Fig. 1), mill / furnace differential pressure (ΔP _{1 in} Fig. ₁ )
And the mill table differential pressure (ΔP _{2 in} FIG. 1). It is checked whether or not each of the conditions is satisfied with the above-described contents. If all four conditions are not satisfied, it is determined that there is no missing carbon, and the determination is terminated. On the other hand, if any one of the four conditions is satisfied, it is determined that a missing carbon condition has occurred, an instruction such as issuing an alarm is issued, and the determination is terminated (step S2 in FIG. 2).

As described above, in the present missing carbon detecting device 11, the main steam pressure (P in FIG. 1) is used as the first index, and when this indicates an abnormality, any one of the remaining four indices can be used. If there is an abnormality, it is determined that the charcoal is missing. Here, if at least one of the four indices around the mill meets the condition (indicating an abnormality), it is determined that there is a missing carbon. May be determined. Further, the apparatus may use three or less indices without using all of the four indices around the mill.

Next, detection of missing carbon in consideration of the state of another pulverized coal feeder installed for the same boiler will be described. The fulfillment of the conditions for the lack of carbon with respect to the above-described respective indexes is not necessarily caused by the lack of carbon and may occur when the operation load of the boiler is intentionally reduced. In that case, a warning that a missing carbon state has occurred by mistake, that is, a so-called false alarm is issued, which is not preferable in terms of the operating efficiency of the boiler.

On the other hand, as described in the prior art,
In a boiler for power generation or the like, a plurality of pulverized coal feeders are generally installed for one boiler. In this case, during the normal operation, the plurality of pulverized coal supply devices are operated with an equal load, and therefore, in a normal state, the measured values of each unit in each of the pulverized coal supply devices indicate similar values. This is the same when the operation load of the boiler is intentionally reduced. Therefore, when the measured value of each index for detecting missing carbon indicates an abnormal value (a value that satisfies the condition), the measured value is compared with the measured value of another pulverized coal supply device,
By checking whether the values are similar or not, it can be determined to some extent whether the values are due to a conscious driving operation or a trouble.

Therefore, with respect to the four indices other than the main steam pressure (P in FIG. 1) in the above-described method for detecting lack of coal, the determination as to whether or not the condition is satisfied is made based on measured values obtained by other pulverized coal supply devices. May be performed after comparing with.
FIG. 3 is a diagram illustrating an example of such a determination method. This example shows a procedure for determining whether the condition is satisfied (step S2 in FIG. 2) by taking the mill table differential pressure (ΔP _{2 in} FIG. 1) as an example. Here, ΔP ₂ (1) is the mill table differential pressure in the pulverized coal supply device to be determined, and ΔP ₂ (1)
Let ₂ (2) and ΔP ₂ (3) be the mill table differential pressures in the other two pulverized coal feeders that supply pulverized coal to the same boiler.

Firstly, similarly to the case of not using the measurement information of other pulverized coal supply apparatus described above, comparing the ΔP ₂ (1) and the set value [Delta] P _min, is larger than the set value [Delta] P _min, the difference of normal It is determined that there is pressure and the condition is not satisfied (step S in FIG. 3).
1). On the other hand, if it is smaller than the set value ΔP _min , ΔP
₂ (1) is the mill table differential pressure ΔP ₂ (2) of the other pulverized coal feeder.
And ΔP ₂ (3). If the difference between the two is smaller than a predetermined value δ, the condition is not satisfied. If either of the differences is larger than δ, the condition is satisfied (FIG. 3). Step S2).

As shown in this example, even when the measured value indicates a value that satisfies the condition for detecting missing carbon, there is no significant difference as compared with the values in other pulverized coal supply devices. , By judging that the conditions do not hold,
It is possible to reduce false alarms when the boiler and the plurality of pulverized coal feeders are intentionally operated while reducing the load.

As described above, in the present missing carbon detecting device,
Since the main steam pressure and multiple measurement information around the mill are directly affected by the reduction in the amount of supplied coal and pulverized coal due to lack of coal, the lack of coal can be detected early and reliably. it can. In addition, it is possible to further reduce false alarms by comparing the measurement information with the measurement information of the other plurality of pulverized coal supply devices. Therefore, by using the present lack-of-carbon detection device, it is possible to prevent a total stoppage due to lack of carbon without deteriorating the operation efficiency of the boiler.

Although the present embodiment has been described with reference to an example of a power generation boiler, the present missing carbon detection device may be used in a boiler for other uses.

The scope of protection of the present invention is not limited to the above embodiments, but extends to the inventions described in the claims and their equivalents.

[0042]

As described above with reference to the accompanying drawings, the present invention has the following effects.

First, the state of lack of carbon can be detected at an early stage by determining the state of lack of carbon based on the main steam pressure of the boiler and a plurality of pieces of measurement information around the mill and the mill.
By using the main steam pressure of the boiler as the first index, it is possible to reduce false alarms and improve the reliability of missing-carbon detection.

Second, by using the mill outlet gas temperature, the mill motor current, the mill / furnace differential pressure, the mill / furnace differential pressure, and the mill table differential pressure as the plurality of pieces of measurement information of the mill and the periphery of the mill, it is possible to quickly and reliably remove the information. It becomes possible to detect charcoal.

Third, when a plurality of pulverized coal feeders are installed for one boiler, a plurality of pieces of measurement information obtained from the plurality of pulverized coal feeders are compared, and then the state of lack of coal is determined. By making the determination, false alarms can be reduced and driving efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of a missing carbon detection device to which the present invention is applied.

FIG. 2 is a diagram showing an example of a procedure for determining missing carbon in a missing carbon detecting device to which the present invention is applied.

FIG. 3 is a diagram illustrating an example of determination by comparing with measurement information in another pulverized coal supply device.

FIG. 4 is a diagram showing a flow of a general pulverized coal supply device for supplying pulverized coal to a power generation boiler.

FIG. 5 is a diagram for explaining a missing carbon detection by a conventional paddle switch.

[Explanation of symbols]

 Reference Signs List 1 coal yard 2 belt conveyor 3 hopper 4 chute 5 coal feeder 6 coal feed pipe 7 mill 8 pulverized coal feed pipe 9 boiler 10 steam turbine 11 missing carbon detector 71 fan 72 air heater 73 hot air control valve 74 cold air control valve 75 mill Table 76 Mill motor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Okamura 4-6-22 Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries, Ltd. Hiroshima Works (72) Inventor Masaki Kondo 4-chome, Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima No. 6-22 Mitsubishi Heavy Industries, Ltd. Hiroshima Works

Claims (4)

[Claims] A pulverized coal feeder for pulverizing coal by a mill and supplying the generated pulverized coal to a boiler detects a state of lack of coal in a pulverized coal supply apparatus, wherein a main steam pressure of the boiler is set in advance. If the main steam pressure is smaller than the preset value when it is larger than the value, it is determined based on measurement information obtained from the mill and the periphery of the mill. A missing carbon detection device for a pulverized coal supply device, which determines whether or not the vehicle is in a missing carbon condition. 2. The mill information according to claim 1, wherein the measurement information includes an outlet gas temperature of the mill, a load of a motor for rotating a table provided in the mill, and a furnace inside the mill and the boiler. The pressure difference between the inside of the mill and the pressure difference between the portion above and below the table inside the mill, and any one or more of the measurement information corresponds to the missing carbon state. A missing carbon detection device for a pulverized coal supply device, wherein a missing carbon detection device is determined to be in a missing carbon state when a state is reached. 3. The method according to claim 2, wherein the measurement information in a state corresponding to the missing carbon state is obtained when a plurality of pulverized coal supply devices provided for the boiler are controlled under the same conditions. A missing carbon detection device for a pulverized coal supply device, wherein if the plurality of pulverized coal supply devices are in the same state, the plurality of pulverized coal supply devices are not determined to be in a missing carbon state. 4. A method for detecting lack of coal in a pulverized coal feeder for pulverizing coal with a mill and supplying the generated pulverized coal to a boiler, wherein the main steam pressure of the boiler is set in advance. When the main steam pressure is smaller than the preset value, when the main steam pressure is smaller than the preset value, measurement information acquired from the mill and the periphery of the mill. A missing carbon detection method, which comprises the step of determining whether or not there is a lack of carbon based on the number of missing carbon.