JPH0641678B2 - Combustion control device for recovery boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial field of application) The present invention is a recovery boiler that burns black liquor generated in a pulp manufacturing process to generate steam and recovers a raw material for chemicals for chip digestion. The present invention relates to a combustion control device, and more particularly to a combustion control device having improved control means for early detection and recovery of an abnormal combustion state of a recovery boiler.

(Prior Art) In a pulp manufacturing plant, black liquor discharged as a waste liquid from a chip cooking process is guided to a black liquor heater, where it is heated by steam and then injected into a furnace of a recovery boiler by a black liquor injection gun. Then, the jetted black liquor floats and dries to form a char bed at the bottom of the furnace, so that combustion air is sent to burn the char bed. The combustion exhaust gas generated at this time is finally discharged from the chimney through the heat transfer parts such as the water wall of the combustion chamber, the super heater (superheater) in the upper part of the furnace, the main bank in the exhaust gas passage line, the economizer, etc. When water is sent through the economizer, the main bank, the super heater, and the water cooling wall of the combustion chamber through the line, the water is heat-exchanged in the heat transfer section and taken out as main steam. Further, the reduction reaction is carried out by a high temperature atmosphere over the char bed, collected as smelt like mirabilite in black liquor _(Na 2 SO ₄₎ is sodium sulfide _(Na 2 S), and the conjunction and sodium carbonate _(Na 2 CO ₃₎ It is configured to be.

Incidentally, in the recovery boiler, dust may drop onto the char bed due to soot blow to the superheater or the like, and a partial landslide or the like may occur in the char bed to locally cause defective combustion. Further, there is a possibility that the calorific value may be reduced due to a change in properties such as a change in black liquor concentration, an increase in circulating Glauber's salt, and a change in the spray state such as a black liquor injection gun and a black liquor heater. Such abnormalities adversely affect the combustion state in the furnace and result in a poor combustion state that is attached to a so-called black port, and not only a sufficient main steam flow rate, main steam temperature and chemical recovery rate cannot be obtained, but also blackout in the worst case. It is called a misfire. In particular, when performing low excess air combustion in which the combustion air is squeezed aiming at high efficiency operation of the recovery boiler, black ports and blackouts are likely to occur due to insufficient air penetration. Therefore, it is very important to detect the black port and the deterioration of the combustion state due to the black port at an early stage and to promptly perform the recovery process in order to achieve stable operation and high efficiency operation of the boiler.

(Problems to be Solved by the Invention) However, conventionally, a decrease in the combustion state has been detected by the operator circulating the recovery boiler and monitoring process data indicating the combustion state. Therefore, the reliability is poor, and the operator overlooks the abnormality, which delays the recovery process, which may make it difficult to perform stable operation and highly efficient operation of the recovery boiler.

Therefore, the present invention can detect the combustion state deterioration of the recovery boiler early and with high reliability, can perform recovery processing promptly, and can always maintain a good combustion state. An object of the present invention is to provide a combustion control device for a recovery boiler, which can easily realize stable operation and high efficiency operation.

[Structure of the Invention] (Means for Solving Problems) According to the present invention, the combustion state determination means determines a decrease in the combustion state due to combustion failure based on the amount of change in process data representing the combustion state in the furnace. When a decrease in the combustion state in the furnace is detected, the combustion state adjusting means increases the supply amount of the combustion air introduced into the furnace and the temperature of the black liquor to perform the combustion state recovery process and the combustion state. After the recovery, the air supply amount and the black liquor temperature before the increase are restored.

(Operation) By taking such a measure, the deterioration of the combustion state due to poor combustion is detected based on the amount of change in the process data indicating the combustion state in the furnace. Since the combustion state is recovered by increasing the air supply amount and the temperature of the black liquor, the drying of the jetted black liquor droplets is promoted, and the combustion state in the furnace can be quickly recovered and also recovered. By returning the air supply amount and the temperature of the black liquor to the original values after the processing, it is possible to shift to normal combustion control and execute appropriate control.

(Embodiment) An embodiment of the device of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a recovery boiler in a pulp manufacturing plant including a combustion control device of the present invention.

In the figure, 1 is a combustion chamber, in which the black liquor A discharged from the chip digesting process passes through a black liquor tank 2 and is heated by a black liquor heater 3 by steam flowing in a steam line 4. After that, the black liquor injection gun 5 is injected and introduced into the furnace, and the injected black liquor floats and dries in the furnace and drops to form a char bed 6. Combustion of the char bed 6 is promoted by the combustion air B1 and B2 supplied from the upper and lower air supply lines 7a and 7b. At this time, the reduction reaction is performed in the high temperature atmosphere on the char bed 6 and the Glauber's salt (Na ₂ SO ₄ ) and the like become sodium sulfide (Na ₂ S), and together with sodium carbonate (Na ₂ CO ₃ ) and the like, from the spoutro 8 at the bottom of the combustion chamber, Smelt C, which is the raw material of the chemical agent used in the chip digestion process. Will be collected as. Further, the combustion exhaust gas D generated by the combustion of the char bed 6 is discharged from the chimney 10 through the exhaust gas passage line 9.

On the other hand, in order to effectively use the heat quantity of the combustion exhaust gas D, a water cooling wall is provided around the combustion chamber 1, a super heater 11 is provided in the upper portion, and a main body bank 12 and an economizer 13 are provided in the middle of the exhaust gas passage line 9. The
The water E supplied from the water supply line 14 is heat-exchanged by passing through the heat transfer parts such as the economizer 13, the main bank 12, the super heater 9, the combustion chamber water cooling wall, etc., and is taken out as the main steam F from the main steam line 15. It has become one.

Reference numeral 16 denotes a combustion control device, which takes in a plurality of process data P1, P2 ... Representing the combustion state in the combustion chamber 1, and locally burns the charbed 6 based on the amount of change of these process data P1, P2. The function of determining the deterioration of the combustion state due to a defect or the like, the amount of combustion air supplied into the furnace from the air supply lines 7a and 7b and the black liquor injected from the injection gun 5 into the furnace by the determination of the combustion state decrease It has a function of changing at least one of the set outputs SV1, SV2, and SV3 with respect to the temperature and increasing it. That is, as the process data representing the combustion state in the furnace, the evaporation amount data P1 detected by the evaporation amount detector 17 provided in the main steam line 15 and the furnace temperature provided in the furnace wall of the combustion chamber 1 and the like. In-furnace temperature data P2 detected by a total of 18
Black liquor concentration data P3 detected by the black liquor concentration detector 20 provided in the black liquor line 19, and exhaust gas SO detected by the exhaust gas detector 21 provided in the exhaust gas passage line 9.
₂ , O ₂ , NO _x , CO ₂ , CO concentration data P4 ...
Take in. On the other hand, the set outputs SV1 and SV2 are given to the upper air amount controller 22 and the lower air amount controller 23, respectively, for the respective upper and lower air amounts PV1 and PV2 detected by the air amount detectors 24 and 25. Optimal adjustment calculation is performed by the operation amount, the manipulated variables MV1 and MV2 are output to the air amount adjusting dampers 26 and 27, and the valve opening is adjusted so that the upper and lower air amounts become the set values SV1 and SV2. It Further, the set output SV3 is given to the black liquor temperature controller 28, the optimum adjustment calculation is performed on the black liquor temperature measured value PV3 detected by the black liquor temperature detector 29, and the manipulated variable MV3 is adjusted to the vapor amount. The black liquor heater 3 is output to the valve 30.
The valve opening degree is adjusted so that the temperature of the black liquor heated by becomes the set value SV3.

FIG. 2 is a block diagram showing a specific configuration of the combustion control device 16. The process data processing unit 31 performs preprocessing such as acquisition filtering on each of the process data P1, P2 ... In a predetermined cycle, and then files the result in the process data storage unit 32. The permissible value data setting unit 33 uses the process data P1 and P1.
The change amount of 2, ..., That is, the upper limit level, the lower limit level, the instantaneous change rate, and the allowable value data D of the long-term change rate are respectively set, and the set allowable value data D are stored in the allowable value data storage unit 34. It is supposed to be done.

The combustion failure determination unit 35 uses the process data P1, P2 ...
Is divided into a plurality of groups, and for each group, the change amount of the process data and the allowable value data D corresponding to these change amounts are compared to determine abnormality of each process data. When it is determined that all the relevant process data are abnormal, it is determined that the combustion failure has occurred, and the combustion failure signal S is sent to the display unit 36 and the recovery processing unit 37. Specifically, the third
It has the functional configuration shown in the figure. That is, each process data P1 is read from the process data storage unit 32, the change amount detecting unit 41 detects the change amount (upper limit value, lower limit value, instantaneous change rate, long-term change rate) for each data, and the comparing unit 42. Then, the permissible value data corresponding to each variation is sequentially read from the permissible value data storage unit 34 and compared. Then, when at least one variation amount of each process data P1, P2 ... Exceeds the allowable value, the abnormal signal Q is output. Here, each process data P1,
P2 ... Are grouped into one or more groups G1, G2 ... And in each group G1, G2 ... When the abnormal signal Q is output from all of the plurality of comparing means 42, that is, the logical product of the outputs of the comparing means 42. When is satisfied, the abnormality determination means 43 outputs the abnormality determination signal R. Then, the abnormality determination signal R from any one of the groups G1, G2 ,.
Is output, that is, when the logical sum of the outputs of the abnormality determination means 43 is established, the combustion failure signal output means 44 outputs the combustion failure signal S.

In FIG. 2, the display unit 36 is composed of a CRT display or the like, and displays a message indicating that the combustion failure has occurred in the combustion chamber 1 in response to the input of the combustion failure signal S. The recovery processing unit 37 drives the recovery function by using the combustion failure signal S as a trigger, and specifically, sets the upper-stage combustion air supply amount, the lower-stage combustion air supply amount, and the black liquor temperature. At least one of the values SV1, SV2, SV3 is increased stepwise as shown in FIG. That is, if the combustion failure signal S is turned on at the time point t1, the set value SV is first increased by "+ L" after a lapse of a certain time, and then, if the combustion failure signal S is turned on, the set value SV is again set. Is increased by “+ L”. Hereinafter, similarly, the set value SV is increased stepwise while the combustion failure signal S is on or until the set upper limit value is reached. On the other hand, if the combustion failure signal S is turned off at the time point t2, the set value SV is lowered stepwise at a constant interval and at a constant level “M” (L = M is also possible) after a certain period of time, and the combustion failure signal S The set value SV is restored to the state before the input of S.

The respective components such as the data processing unit 31, the combustion failure determination unit 35, the recovery processing unit 37, etc. operate under the control of the main control unit 30.

In this embodiment having such a configuration, the black liquor heated to a predetermined temperature by the black liquor injection gun 5 is injected into the combustion chamber 1, and the jetted black liquor is suspended and dried. Char bed 6 is formed on the bottom of the furnace.
Combustion is promoted by a predetermined amount of combustion air B1, B2 from the upper / lower air supply lines 7a, 7b, and the combustion exhaust gas D is cooled by the water cooling wall, the super heater 11, the main bank 1
2. It is discharged from the chimney 10 through the economizer 13. In this state, the main steam line 15 from the steam amount detector 17 is used as process data representing the combustion state in the furnace.
Evaporation data P1 of the main steam F flowing through the furnace, thermometer 18 in the furnace
Data P2 inside the combustion chamber 1 from the black liquor concentration detector 2
Concentration data P of black liquor flowing from 0 on the black liquor line 19
3 and SO ₂ and O of the exhaust gas from the exhaust gas detector 21
_{2, NO} x, _{CO 2,} each density data of CO P4 ... are given to the combustion control device 16.

In the combustion control device 16, the process data processing unit 3
At step 1, the process data P1, P2, ... Are taken in, pre-processed such as filtering, and then stored in the process data storage unit 32. On the other hand, the allowable value data setting unit 33
As a result, the allowable value data D for the upper limit level, the lower limit level, the instantaneous change rate, and the long-term change rate are preset as the amount of change in the process data P1, P2, ... It is stored in the unit 34. In the combustion failure determination unit 35, the amount of change (upper limit level, lower limit level instantaneous change rate, long-term change rate) is detected for each of the process data P1, P2, ... And compared with the corresponding allowable value data D. When at least one change amount exceeds the permissible value data for each process data P1, P2, ..., An abnormal signal Q is output.
Here, for example, the process data P as the group G1
When the abnormal signal Q is output from all of the 1, P2 and P3 systems, the process data P4 (S
O ₂ ), P 4 (O ₂ ), P 4 (NO _x ) system outputs an abnormal signal Q, or process data P 4 (CO ₂ ), P 4 (CO) is abnormal from all systems as a group G 3. When the signal Q is output, the abnormality determination signal R is output. As a result, at least 1
If the abnormality determination signal R is output from two groups,
When it is determined that the combustion failure has occurred, the combustion failure signal S is output, the fact that the combustion failure has occurred is displayed on the display unit 36, and the recovery processing unit 37 executes a predetermined recovery process.

In the recovery processing unit 37, when the combustion failure signal S is input, the set values SV1 and SV2 of the upper / lower stage combustion air supply amount and the set value SV of the black liquor temperature after a certain period of time elapses.
At least one of 3 is increased stepwise by level L. For example, each set value SV of upper / lower combustion air supply amount
1 and SV2 are increased, each air amount controller 22, 23
The optimum adjustment calculation is performed in the air amount adjustment damper 26,
The valve opening of No. 27 gradually expands, and the amount of combustion air supplied into the recovery boiler 1 increases. As a result, the air permeates the char bed 6, and the combustion failure can be recovered. On the other hand, when the set value SV3 of the black liquor temperature is increased, the black liquor temperature adjusting type 28 performs the optimum adjustment calculation, and the valve opening of the steam amount adjusting valve 30 is gradually widened so that the steam to the black liquor heater 3 is increased. The amount increases, and the temperature of the black liquor injected into the combustion chamber 1 rises. As a result, the floating and drying of the black liquor in the combustion chamber 1 is promoted, and the combustion failure can be recovered.

Then, if the combustion failure in the combustion chamber 1 is recovered and the combustion failure signal S from the combustion failure determination unit 35 is turned off, the increased set value is decreased stepwise by the level M after a certain period of time. . When the level returns to the set value level before the combustion failure signal is input, the normal combustion control is performed.

As described above, according to the present embodiment, the evaporation data, the temperature in the furnace, the black liquor concentration, the exhaust gas SO ₂ , O ₂ , NO _x , CO ₂ , and CO are constantly represented as the process data representing the combustion state in the furnace. The concentration is captured, and the upper limit level, lower limit level, instantaneous rate of change, and long-term rate of change as the amount of change in the process data are compared with the permissible value data to determine whether the process data is abnormal. The combustion failure in 1 is judged, and the combustion air supply amount and the black liquor temperature are increased to recover the combustion state. As a result, it is possible to detect defective combustion such as black ports at an early stage, and since recovery processing is automatically performed when defective combustion occurs, there is little risk of blackout, and the combustion state is quickly restored. The probability of doing it increases. Further, since the combustion failure is determined by comprehensively determining a plurality of process data, highly reliable determination results can be expected. Further, since the set value is increased and decreased stepwise during the recovery process, the disturbance to the plant can be suppressed to a small level. Therefore, stable operation and highly efficient operation of the combustion chamber 1 can be easily realized, and there is no fear of adversely affecting the turbine connected to the recovery boiler and each process.

The present invention is not limited to the above embodiment.
For example, in the above embodiment, as process data representing the combustion state in the furnace, evaporation amount data, furnace temperature data, black liquor concentration data, exhaust gas SO ₂ , O ₂ , NO _x , CO ₂ ,
Although each concentration data of CO is shown and the change amount of these process data is shown as the upper limit level, the lower limit level, the instantaneous change rate, and the long-term change rate, the present invention is not limited to these, other data and other changes. It goes without saying that the amount may be used. It is also possible to determine the deterioration of the combustion state by taking in at least one of these process data and comparing at least one change amount with an allowable value. In addition, in the above embodiment, the combustion failure determination unit 35
Although the abnormality determination means 43 outputs the abnormality determination signal R when the abnormality signals Q are output from all the comparison means 42 in the corresponding group, the at least one comparison means 42 outputs the abnormality signal Q. In this case, the abnormality determination signal R may be output. On the other hand, the combustion failure signal output means 44 may output the combustion failure signal S only when the abnormality determination signal R is sent from all the groups.

Further, in the above-described embodiment, the case where the allowable value data for the amount of change in the process data is set in one step is shown. However, by setting this in two steps, the deterioration of the combustion state is caused by, for example, a mild combustion failure and a severe combustion failure. In the case of mild combustion failure, the recovery process as in this embodiment is performed, and in the case of severe combustion failure, at least one of the combustion air supply amount and the black liquor temperature is increased only once. Therefore, a process for holding the current state is performed, and in the case of a more severe combustion failure, it may not be recovered by automatic control. Therefore, the recovery may be entrusted to the operator. Further, it is possible to divide the deterioration of the combustion state into a plurality of stages according to the degree of combustion failure.

Further, a manual switch is provided in the recovery processing unit 37, and the operator monitors the display of the display unit 36, and the recovery process, that is, the increase of the combustion air supply amount or the black liquor temperature is manually performed according to the combustion lowering state. Good. Of course, various modifications can be made without departing from the scope of the present invention.

[Effects of the Invention] As described in detail above, according to the present invention, the combustion state determination means determines the deterioration of the combustion state due to the combustion failure based on the amount of change in the process data representing the combustion state in the furnace, When a decrease in the combustion state in the furnace is detected, the combustion state adjusting means adjusts the combustion state by increasing the supply amount of the combustion air introduced into the furnace and the temperature of the black liquor. Even if a partial landslide on the bed occurs and local combustion failure occurs, it can be detected early and reliably, and recovery processing can be performed promptly.
Since the normal combustion control is performed, it is possible to provide the combustion control device of the recovery boiler which can always maintain a good combustion state and can easily realize stable operation and high-efficiency operation of the recovery boiler.

[Brief description of drawings]

1 to 4 are views showing an embodiment of the present invention. FIG. 1 is a system diagram showing a schematic configuration of a recovery boiler in a pulp manufacturing blunt, and FIG. 2 is a specific configuration of a combustion control device. FIG. 3 is a block diagram showing a specific configuration of the combustion failure determination unit, and FIG. 4 is a diagram for explaining the operation of the recovery processing unit. 1 ... Combustion chamber, 3 ... Black liquor heater, 4 ... Black liquor heating steam line, 5 ... Black liquor injection gun, 6 ... Char bed, 7
a, 7b ... Combustion air supply line, 9 ... Exhaust gas passage line, 15 ... Main steam line, 16 ... Combustion control device,
17 ... Evaporation amount detector, 18 ... Furnace thermometer, 19 ...
Black liquor line, 20 ...... Black liquor concentration detector, 21 ...... Exhaust gas detector, 22, 23 ...... Air quantity controller, 28 ...... Black liquor temperature controller, 35 ...... Combustion failure determination unit, 37 ...... Recovery processing unit.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Yohei Shiogoshi, 1-1 1-1, Jujo-cho, Yatsushiro-shi, Kumamoto Pref., Inside the Yatsushiro Mill, Tojo Paper Co., Ltd. (72) Michitaka Okura 4-1-1, Shimaya, Konohana-ku, Osaka, Osaka No. 35 Kawasaki Heavy Industries, Ltd. Osaka Plant (72) Inventor Toshiyuki Ibed 1-1 Kawasaki-cho, Akashi-shi, Hyogo Prefecture Kawasaki Heavy Industries Ltd., Akashi Plant (72) Inventor Shiro Nakabayashi No. 1 Kawasaki-cho, Akashi-shi, Hyogo Prefecture No. 1 Kawasaki Heavy Industries Ltd., Akashi Plant (72) Inventor Kazuyuki Iizuka 1-1-1, Shibaura, Minato-ku, Tokyo Toshiba Head Office Co., Ltd. (72) Inventor Ryuichi Kuwata No. 1 Toshiba-cho, Fuchu, Tokyo Inside the Toshiba Fuchu Factory (72) Inventor Ao Kumaki 1 Toshiba Town, Fuchu City, Tokyo Inside the Fuchu Factory, Toshiba Corporation (72) Inventor Atsushi Muramatsu Tokyo Medium City Toshiba-cho, address 1 Toshiba Fuchu in the factory (56) references Tokuoyake Akira 54-17841 (JP, B2)

Claims (4)

[Claims] 1. A recovery boiler that burns black liquor to generate steam and recovers a chemical raw material for chip digestion, based on the amount of change in a plurality of process data indicating the combustion condition in the furnace And a combustion state determining means for determining a decrease in the combustion state in the furnace when the combustion state determining means detects a decrease in the combustion state in the furnace, while introducing a recovery state from the output of the combustion state determining means into the furnace. Combustion state recovery processing means for performing combustion state recovery processing by increasing the supply amount of air and the temperature of black liquor; and when the combustion state recovery processing means recovers the combustion state in the furnace, the increased combustion A recovery control unit for a recovery boiler, comprising: a recovery processing unit that recovers the supply amount of supply air and the temperature of black liquor to a state before the increase. 2. The combustion state determination means sets a permissible value for the variation of the plurality of process data, and determines a decrease in the combustion state when the variation of the process data exceeds the permissible value. A combustion control device for a recovery boiler according to claim (1). 3. The combustion state recovery processing means increases the combustion air supply amount and the black liquor temperature stepwise at predetermined intervals.
A combustion control device for a recovery boiler according to the item. 4. The combustion state recovery processing means determines the combustion state from being divided into a plurality of stages by the combustion state determination means, and increases the combustion air supply amount and the black liquor temperature according to the determination result. The combustion control device for the recovery boiler according to claim (1), characterized in that.