JPS6229822A - Control device for flow rate of combustion air in recovery boiler - Google Patents

Abstract

PURPOSE:To provide a stable control of combustion in a chip digestion process by a method wherein a variation of Glauber's salt volume fed is detected and when the volume of Glauber's salt is increased, a setting value of volume of lower part combustion air is increased. CONSTITUTION:Detected values at SO2 densitometer 21 and CO2 densitometer, 22 in a discharging gas line L1, detected values at a density meter 29 and a pyrometer 30 of a boiler 1 in an injected black liquid line L2 and a detected value at a flow meter 31 on a main steam line L3 are routed through filters 32 to 36, differentiaters 37 to 41, and calculaters 42 to 46 so as to calculate a rate of variation and then input to the setting value variation calculator 47 as air increasing command signals S21-S25. This calculator 47 calculates a lower combustion air flow setting value S3 in addition to the lower combustion air flow command signal S43 inputted and then output it to the lower combustion air volume controller 54. It compares the value 33 with the lower combustion air flow volume S34 outputted from the flowmeter 55 so as to control a volume of combustion air. With such an arrangement as described above, it is possible to provide a stable combustion control even if a volume of Glauber's salt is increased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for recovering a pulp cooking agent by burning black liquor discharged as waste liquid from a pulp cooking process for producing paper, and generating steam. The present invention relates to a combustion air flow rate control device for a recovery boiler, and more particularly to a combustion air flow rate control device for a recovery boiler with improved means for stabilizing combustion in the recovery boiler.

[Conventional technology]

Conventional combustion air flow control for this type of recovery boiler is as follows:
Generally, an operator operates a manual setting device to control the combustion air flow to an appropriate level depending on the load. However, in recent years, with the aim of reducing the burden on the operator and increasing efficiency, appropriate combustion air flow m has been developed according to the black liquor flow rate.
How to set the set value by calculation and CoIl in exhaust gas
A method is used in which the combustion air flow rate is adjusted by detecting the CO concentration so that the CO concentration remains constant. Furthermore, in addition to the above-mentioned methods, a method is also used in which the optimal combustion air flow distribution is set by conducting a trial search for the combustion air flow distribution.

[Problem that the invention seeks to solve]

However, each of the above methods cannot be applied to the bottom of the furnace in cases such as when the number of mirabilite mixed into the injection black liquor supplied to the recovery boiler increases or when soot blows at the top of the furnace of the recovery boiler and soot falls. The amount of Glauber's salt that is reduced increases, and much of the heat of the reduction reaction is taken away, resulting in a decrease in the temperature inside the furnace, a decrease in the amount of steam generated, a rise in SO2 in the combustion exhaust gas, and even COa.
This results in a decrease in combustion conditions in the recovery boiler.

In addition, especially when performing 00m degree feedback control, the combustion air is operated in a direction to restrict it, so there is a problem in that it warps and causes poor combustion.

The present invention has been made with attention to the above-mentioned points, and an object of the present invention is to provide a combustion air flow m control device for a recovery boiler that can properly and stably control combustion of the recovery boiler even when the amount of mirabilite increases. With the goal.

[Means for solving problems]

Therefore, in order to achieve the above-mentioned object, the present invention detects the amount of mirabilite input into the recovery boiler, and when the amount of mirabilite increases, increases the flow rate of lower combustion air supplied to the vicinity of the bottom of the furnace. This is designed to ensure stable combustion of the boiler.

[Effect]

Therefore, by using the above means, the present invention
If the lower combustion air flow m near the furnace bottom is increased when the amount of mirabilite increases, the combustion of combustible substances in the char bed formed at the furnace bottom will be promoted, and the amount of heat generated at the furnace bottom will decrease. Since this can be supplemented, deterioration of combustion in the recovery boiler can be reliably prevented.

〔Example〕

Hereinafter, before explaining the specific embodiments, the basic principle for realizing the present invention will be described. Glauber's salt E in the injected black liquor is the mirabilite that adheres to the boiler tip of the recovery boiler! ! When the refluxed Glauber's Salt is mixed into the mixing tank after soot-blowing, the amount increases excessively, and this appears as an increase in the density of the injected black liquor.

When this injected black liquor is injected into the furnace or soot blow is performed at the top of the furnace and Glauber's salt falls, the amount of reduction reaction increases at the bottom of the furnace and the amount of heat absorbed increases, which causes the inside of the furnace to As the temperature drops, combustion inside the furnace worsens.

As the reducing atmosphere area inside the furnace becomes smaller, the capture of sulfur oxides (SOxj) by the Na2O fume that was generated in large quantities in the reducing atmosphere at the bottom of the furnace becomes poor, the SOW level rises, and the amount of generated steam decreases. .

Also, as combustion worsens, the amount of carbon burned decreases,
CO2 vagueness decreases. Furthermore, by increasing the outflow of bottom combustion air that blows into the bottom of the furnace when combustion is deteriorating,
The combustion of char (carbon) in the char bed at the bottom of the furnace is promoted, and the amount of heat generated by the combustion of char increases.
This appears as an increase in the temperature inside the furnace, a decrease in 5O2a degrees, an increase in the CO2 concentration, an increase in the amount of steam generated, etc.

Therefore, in response to the above phenomenon, if the increase in the amount of mirabilite introduced into the furnace is detected, and if the increase in the amount of mirabilite is large and causes deterioration of combustion, the lower combustion air flow rate can be increased. , it is possible to obtain a calorific value of combustion of char that compensates for the endothermic loss of heat generated at the bottom of the furnace, making it possible to prevent deterioration of combustion. In this case, the combustion of char at the bottom of the furnace only temporarily reduces the amount of char burned, so the increase in the amount of mirabilite, which usually causes deterioration of combustion, is temporary. , it is possible to prevent most of the deterioration of combustion.

The present invention has been realized based on the above principles, and one embodiment thereof will be described below with reference to FIG. 1. In the figure, 1 is a recovery boiler, and this boiler 1 includes an evaporator 3 for heat-exchanging feed water 2, a drum 4, and a main steam line L3 for superheating the steam 5 heat-exchanged by the drum 4. A superheater 7, etc., which passes through the main steam 6 and sends it out of the system as main steam 6, is provided. 8 is the inside of the furnace, 9 is the exhaust gas, and Ll is the exhaust gas line. Further, although not shown in the figure, the injection black liquor 11 discharged from the pulp cooking process is introduced into the recovery boiler 1 via an injection black liquor line L2, and is injected into the furnace interior 8 by an injection gun 12. ing. 13 is a charbed in which the jetted black liquor 11 is suspended and dried, and 14 is a reduction reaction in the high temperature atmosphere above the charbed 13, and the mirabilite (N82 CO4) etc. in the black liquor become sodium sulfide (Na2S). This is smelt as a drug recovered from Subautoro 15 along with sodium carbonate (N82CO:l) and the like.

The exhaust gas line L1 includes an 802 concentration meter 21,
A CO2i degree meter 22 and a CO concentration meter 23 are installed,
In addition, in the injection black liquor line L2 that supplies the recovery boiler 1, the black liquor discharged from the pulp cooking process (not shown) is concentrated in a concentrator, and the black liquor is recovered by soot blowing of the recovery boiler 1 to a turbidity point 'a24. A mixing tank 27 for mixing the refluxed Glauber's salt 25 and the supplementary Glauber's salt 26, etc., and a heating section 28 for outputting the mixed black liquor outputted from the mixing tank 27 as jetted black liquor at an appropriate temperature are provided. The density of this jetted black liquor is detected by a density meter 29. 30 is a pyrometer such as a radiation thermometer installed on the furnace wall to detect the temperature inside the furnace 8. moreover,
A flow meter 31 for detecting the main steam flow rate is installed in the main steam line L3. These SO2 concentration meters 21, C
Each output terminal of the O2'a degree meter 22, density meter 29, pyrometer 30, and flow meter 31 has an output of 81 to S.
5 smoothing filters 32 to 36, each filter 32 to
Differentiator circuit 3 for calculating the rate of change 811 to 815 of the output of 36
Computing units 42 to 4 that output lower combustion air increase command signals 821 to S25 as a function of each rate of change via 7 to 41;
6 is connected, and the output of each of the calculation units 42 to 46 is connected to a set value change calculation unit 47 that changes the set value of the lower combustion air flow.
It is configured to be introduced in

On the other hand, the recovery boiler 1 is provided with a lower combustion air line L41 and an upper combustion air line L42, the lower combustion air 831 is controlled by the lower operation part 51, and the upper combustion air S32 is controlled by the upper combustion air line L42. Air flow miI! It is adjusted by the first knot part 52 and the lower combustion air flow rate adjusting part 53.

The set value change calculation unit 47 receives the set value increase command signal@
822 to 825, the lower combustion air flow setting value 833 is changed using these as a function, and is supplied to the lower combustion air flow rate adjustment section 54. This lower combustion air flow rate adjustment section 5
4 receives the lower combustion air flow ff1s34 of the flow meter 55 installed on the output side of the operation unit 51, and receives this air flow ff1s.
34 is adjusted to be equal to the lower combustion air flow rate setting Ia833, and this adjusted output 335 is introduced into the operation section 51 to control the lower combustion air flow ff1s4 to the recovery boiler 1.
It has the function to change 6.

56 is CO31 degree adjustment 1, and setting section 5761 to 0
0m degree setting 11536 is given, and the COs degree 341 detected by the CO concentration meter 2S of the exhaust gas line L1 and the flow rate 11 from the flow meter 58 installed on the upper 2 side of the injection black liquor line.
842 is given.

(7) COII scale W scale IJ 56 Ha COm m
S41 tfi Performs adjusting operation so as to be equal to CO concentration set value 336, and outputs lower combustion air flow rate command signal S43, upper combustion total air flow rate command 844, upper combustion air flow rate command 345, etc. be. Therefore, the upper combustion air flow u Fj! The 4M section 53 is adjusted so that the upper combustion air 847 meets the command 845.

Next, the operation of the apparatus configured as above will be explained. The black liquor discharged as waste liquid from the pulp cooking process for producing paper is converted into MTRA liquid 24 in a concentrator, and then mixed with refluxed Glauber's salt 25 and supplementary Glauber's salt 26 recovered by soot blowing of the recovery boiler 1 in a mixing tank 27. The jetted black liquor 11 heated by steam in the heating section 28 is put into the furnace 8 by the jet gun 12, whereupon it is suspended and dried and settles on the bottom of the furnace to form the charbet 13. At this time, some of the fertile components in the injected black liquor evaporate as volatile components into the furnace 8 at the top of the char bed during floating drying, and the lower combustion air 8 supplied to the bottom of the furnace
46, the surface of the char bed undergoes reductive combustion, and the incompletely combusted gas along with the volatile components is transferred to -F section combustion air S4.
7.848, a high temperature atmosphere is created at the same time as complete combustion occurs in one part of the char bed. Due to this high temperature atmosphere,
Dry deposits of black liquor, i.e. on the char bed, are i! The original reaction is carried out, and the reduction reaction of mirabilite in the black liquor results in 1-lium sulfide, which is recovered from Subau I-015 as smelt 14 along with mR sodium and the like.

On the other hand, after the combustion gas exchanges heat with the working fluid in the heat transfer tubes of the superheater 7 and the evaporator 3, it is discharged to the outside of the system as exhaust gas 9. At this time, the working fluid is supplied to the drum 4 as water supply 2, and the steam 5 evaporated by the evaporator 3 is superheated by the superheater 7 and taken out of the system as main steam 6.

At this time, the SO2 concentration meter 21 in the square gas line L1
and the SO2 concentration S in the exhaust gas by the C02a degree meter 22.
1 and CO28 degrees, and the injection black liquor line L2
A density meter 29 is installed at the top of the main steam line to measure the density S3 of the injected black liquor 11, and a pyrometer 30 measures the furnace temperature S4 of the recovery boiler 1. 185 and these measurement outputs 8
1 to S5 are supplied to corresponding filters 32 to 36, respectively. These filters 32-36 have respective outputs 81-S.
5 is smoothed and supplied to differentiating circuits 37-41. This differentiation circuit 37 calculates the 80211i1 degree change rate S11 and supplies it to the calculation unit 42, where the lower combustion air flow rate increase command signal 521 (second
Figure a) is obtained by labor. The differentiation circuit 38 is the filter 3
When receiving CO2 concentration $2 from 3, CO211 degree change rate S
12 is obtained and supplied to the calculation section 43. This calculation unit 43 calculates the lower combustion airflow increase command signal 522 (FIG. 2b) as a function of the CO28 degree change rate 812. Similarly, in the differentiating circuits 39 to 41 and the calculation units 44 to 716, the rate of change 813 to S15 of the filter outputs 83 to S5 is
is calculated, and the lower combustion air flow rate increase command signal @S23~525 (Fig. 2 c-e) is calculated as a function of these rate of change.
tmL, signals S21, S22, etc., are supplied to the set value changing unit 47.

On the other hand, for combustion air Ft FA tillIll ノ coar! 1 adjustment section 5G is installed, and this has a Co! i degree setting 1 shift 836 is supplied,
In addition, from the CO temperature meter 23 and flow meter 58 installed in the exhaust gas line L1 and the injection black liquor line L2, respectively,
The degree of COa in the Y gas 841 and the flow rate 342 of the injected black liquor 11 are supplied. This COD scale 56 calculates a reference air flow rate according to the black liquor flow rate 842 from the flow meter 58 to obtain a lower combustion air flow rate command signal 843 and supplies it to the set value change calculation unit 47; Using the difference between the Co concentration set value S36 detected by the CO concentration meter 23 and the CO concentration S41 detected by the CO concentration meter 23, the reference air flow rate command for the upper combustion air flow rate (feedback color v4 section is used to issue the upper combustion air flow open command) A signal S44 is obtained and supplied to the adjustment section 52, and a value obtained by multiplying the upper combustion air flow opening command signal S44 by a certain ratio is supplied to the adjustment section 53 as an upper combustion air flow rate command signal 34.5. .

Here, the adjustment unit 52 adjusts the upper combustion total air 832 as the actual air flow rate to the upper combustion total air retirement command signal 844.
The upper combustion air 848 is adjusted to be equal to 1
9. This is sent to the recovery boiler 1. Upon receiving the upper combustion air flow rate command signal S45 from the adjustment unit 53 (or CO concentration adjustment unit 56), the upper combustion air flow rate 848 of the previous stage adjustment unit 52 is adjusted to be equal to the command signal 845, and this Upper combustion air 847, which is the regulated output, is sent to the recovery boiler 1.

On the other hand, the set value change calculation unit 47 receives the lower combustion air flow rate command signal 843 from the Coa adjustment scale 56 as well as the lower combustion air increase command signals 821 to S25 from each calculation unit 42 to 46. For example, the command signal 843,
A calculation is performed to increase and change the lower combustion air flow rate set value 830 using the calculation formula based on the following formula using S21 to S25 as a function.

S33~S430M in (821, S22, S2
3, S24, S25) That is, when the set value change calculation unit 47 receives an air increase command signal from any of the calculation units 42 to 46, it adds the air increase command signal to the flow rate command signal 843 and adjusts the air increase command signal for lower combustion. The air flow rate setting 1is33 is increased and supplied to the lower combustion air flow rate adjustment section 54. In addition, when the setting (direct change calculation unit 47 adds more than a numerical value to the lower combustion air flow rate command signal 843), a signal 849 for holding the feedback adjustment of the COW adjustment 56 is sent to the CO energy adjustment unit. The lower combustion air flow rate adjusting section 54 adjusts the lower combustion air flow rate 834 detected by the flow meter 55 to be equal to the flow ffi setting value 833, and adjusts the output of the lower combustion air 835 into the operating section 51. Here, the operating section 51 controls the operation so that the lower combustion air 831 as the actual air flow direction becomes equal to the adjustment output 335 of the adjusting section 54, and the obtained lower combustion air S46 is supplied to the recovery boiler 1.

Therefore, according to the configuration of the embodiment as described above, the 802 concentration meter 21 and the C
An O2 concentration meter 22, a density meter 29 in the injection black liquor line L2, a pyrometer 30 in the recovery boiler itself, and a flow meter 31 in the main steam line L3 are installed, and the rate of change of these detection outputs is calculated to generate an air increase command signal 821. ~825 are obtained, and these are supplied to the set value change calculation unit 47 to be added to the lower combustion air flow rate command signal 843 and used as the lower combustion air flow m set value 833, so that the amount of Glauber's sulfate injected into the furnace is When the increase in the amount of mirabilite is large and causes combustion deterioration, the lower combustion air flow rate setting value is increased to compensate for the endothermic loss of heat generated at the bottom of the furnace. of heat generation, and can prevent deterioration of combustion. In particular, if a means for detecting an increase in the density of the injected black liquor is used, it is possible to directly detect an increase in the amount of mirabilite mixed in the injected black liquor, thereby preventing deterioration of combustion, and Figure 3 clearly shows this point. This is what I did. The figure (a) shows the density measurement value 83 detected by the density meter 29. The same figure (b>1 is the density change rate S13 obtained by the differentiation of the differentiating circuit 39, the same figure (C) is the calculation unit 44
Lower combustion air increase command signal 823 calculated by
It is.

Therefore, when the set position change calculation unit 47 receives the lower combustion air increase command signal 823 as described above and receives the lower combustion air flow rate command signal S43 shown in 3(d), the setting position change calculation unit 47
The signal 843 shown in FIG. 8(e) is increased by the signal S23 and outputted as the lower combustion air flow rate set value S33. Therefore, the lower combustion air flow ffi adjustment section 54
When receiving the set value 833, the lower combustion air flow fis
IIL so that 34 is equal to the setting 1iaS33,
The adjustment output 833 obtained here is given to the operating section 51 to operate and control the lower combustion air. Therefore, if the lower combustion air flow m set value 333 is increased as the injected black liquor density increases as described above, 80211 degrees S1 will be held low as shown in <g) in the same figure, and the fluctuation of the main steam flow fiS5 will be suppressed. or less. On the other hand, the lower combustion air flow rate set value of the conventional device remains constant even if the amount of mirabilite increases, as shown in (f) of the same figure, and as a result, as shown in (h) of the same figure, S0
2′ fji degree S1 fluctuates widely, and the main steam flow IS5
There was a problem in which the amount decreased significantly.

In addition, in the above actual flow example, as an increase detection means of awn 5f4m,
502y7J degree in exhaust gas, CO21m degree in exhaust gas,
We have described examples using all of the changes in the density of the injected black liquor, the temperature inside the furnace, the amount of steam generated, etc., but one of these
One or more detection signals may be used to increase the lower combustion air flow rate setting (l?!S30.Also, 5O2iJif1 degree, CO2 may be converted into 02 concentration and used. .

In addition, the main steam flow rate change rate 815 is used as a means for detecting changes in the amount of generated steam, but in order to exclude the influence on changes in the black liquor flow rate, the main steam flow rate/' rate of change in the black liquor flow rate, that is, the steam gain The rate of change may also be used. For example, first-order lag filters may be used as the filters 32 to 36 in order to extract effective change components from the measurement signal. Further, the differentiating circuits 37 to 41 generally have a transfer function T2
It is sufficient to use one equivalent to the incomplete differential given by S/1+TIS. In addition, the present invention is not limited to the above-mentioned actual flow example, and can be implemented with various modifications.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to prevent deterioration in combustion caused by an increase in the amount of refluxed mirabilite mixed into the injected black liquor due to soot blowing, and a fall of mirabilite to the bottom of the furnace due to soot blowing at the top of the furnace. Therefore, the combustion can be stabilized, the main steam can be stabilized, and S02 can be reduced. Additionally, if an increase in the density of the injected black liquor is detected, an increase in the amount of mirabilite mixed in the injected black liquor can be directly detected, and other increases in SO2 can be detected indirectly, but in any case, the amount of mirabilite can be detected directly. If the lower combustion air flow rate set value is increased by detecting an increase in the temperature, it is possible to accelerate the combustion of combustible materials in the char bed formed at the bottom of the furnace, and compensate for the decrease in photogenic thermal risk at the bottom of the furnace. This makes it possible to prevent poor combustion caused by falling of Glauber's salt to the bottom of the furnace due to soot blowing at the top of the furnace.

[Brief explanation of the drawing]

1 to 3 are shown to explain one embodiment of the device of the present invention, FIG. 1 is a system diagram showing a specific example of the device of the present invention, and FIG. 2 is a diagram of each mirabilite a. FIG. 3 is an explanatory diagram of a function for obtaining a lower combustion air increase command signal for detecting an increase, and is a diagram for comparing the effects of the device of the present invention and the conventional device. Ll...exhaust gas line, L2...injection black liquor line,
L3...Main steam line, 1...Recovery boiler, 2...
・Water supply, 6...Main steam, 11...Black liquor injection, 21.
...5o2a degree meter, 22...CO2m degree, 23...
・COW power meter 9... Density meter, 30... Pyrometer, 31... Flow meter, 37-41... Differential circuit,
42-46...Calculation unit, 47...Set value change calculation unit, 51...Operation unit, 52.53...i! Section 1, 5
4...lower combustion air flow layer adjustment section, 55...i f
Fi! if, 56...COI degree y4 node, 58...
·Flowmeter. Applicant's agent Patent attorney Takehiko Suzue (a)
(b) (C) Figure 2 (d) (e) 1. Indication of the incident Patent application 1986-168992 @ 2o Komyo name Recovery boiler combustion air flow suspension device 3, famous incident for correction Relationship: Patent applicant Jujo Paper Co., Ltd. (and 2 others) 4. Agent No. 17 Mori Building, 1-26-5 Toranomon, Minato-ku, Tokyo.
7. 7. Contents of the amendment (1) "2. Scope of claims" in the specification will be corrected as shown in the attached sheet. (2) The text "The present invention produces paper......Recovers chemicals" on the 10th line of the 2nd page to the 12th line of the same page in the light m layer is replaced with ``The present invention produces pulp. "The black liquor discharged as waste liquid from the chip cooking process is burned to recover raw material for chip cooking chemicals." (3) From the 17th line of page 3 of M1 to the 18th line of the same page, the phrase ``deteriorates. Also, especially'' should be replaced with ``deteriorates.Especially when soot blowing is performed and Glauber's salt falls, the bottom of the furnace The combustion becomes unstable, leading to deterioration of the combustion condition. (4) Detect the amount of mirabilite fed into the 1st recovery boiler on the 8th line of page 4 of Meihu Momme, and detect the change in the amount of mirabilite fed into the furnace of the 1st recovery boiler and correct it. . (5) "Reflux" on page 5, line 4 of the specification is corrected to "recovery J." (6) Akira tlAMIM5Ti, line 15 (7) l'
5OIIUJ,! : Correct the statement as "1 chip." (8) "Volume" on page 7, line 8 of the specification is corrected to "deposition". (9) rcO+J on page 7, line 10 of the specification is r.
Correct it as sO+J. (10) The phrase "as a drug" on page 7, line 13 of the specification is corrected to "as a drug raw material." (11) From line 6 of page 8 of the specification to line 7 of the same page, “
Pyrometer such as radiation thermometer" means 1 radiation thermometer"
I am corrected. (12) The word "pyrometer" on page 8, line 10 of Akira 11fl is corrected to read "thermometer of Akira 11fl." (13) Meill page 10, line 11 to box 12 on the same page
The line ``The black liquor discharged as waste liquid from the pulp cooking process to produce paper was concentrated in a concentrator'' is changed to ``
The black liquor discharged as waste from the chip cooking process was converted into concentrated liquid 24 in a concentrator.'' (14) In the specification, page 11, line 6 to line 8 of the same page, the phrase ``drying of black liquor...reduction reaction'' has been replaced with ``the reduction reaction of mirabilite in black liquor.'' correct. (15) “Pyrometer” in Mei 4I, page 12, line 2
Correct the text to read "radiation thermometer." (16) The words "pyrometer" in the second and third lines of page 16 of the specification are corrected to read "radiation thermometer."<17) In the 9th line of page 20 of the specification, the phrase "may be used. Also," should be replaced with "may be used." In addition, if several detection signals are used, each signal may be Although filters, differentiating circuits, etc. are provided correspondingly, each detection signal may be processed by using filters with a plurality of characteristics or by sharing some of them using a multiplexer or the like. (18) Specification page 19, line 15 to cylinder 17 of the same page
In the line, "It can be compensated, the upper part of the furnace... can be prevented." should be corrected to "It can be compensated." (19) On page 20, line 9 of the specification, "Pyrometer J" is corrected to read "rrll radiation thermometer." 2. Claims (1) A combustion air flow rate control device for a recovery boiler that burns black liquor discharged as waste liquid from a pulp cooking process to recover pulp cooking chemicals and generates steam, A amount detection means for detecting the amount of mirabilite introduced into the furnace of the recovery boiler, and a lower combustion air flow rate to be introduced into the vicinity of the bottom of the recovery boiler to a predetermined setting value. a lower air flow rate adjusting means; and a set value increasing change means for increasing the set value of the lower combustion air flow rate in accordance with an increase in the amount of mirabilite mixed in when the amount of mirabilite detected by the mirabilite amount detection means increases. A combustion air outflow control device for a recovery boiler, characterized by comprising:

Claims (2)

[Claims] (1) In a combustion air flow rate control device for a recovery boiler that burns black liquor discharged as waste liquid from the pulp cooking process to recover pulp cooking chemicals and generates steam, it is introduced into the furnace of the recovery boiler. a lower air flow rate adjusting means for adjusting a lower combustion air flow rate to be injected into the vicinity of the bottom of the recovery boiler to a predetermined set value; Combustion of a recovery boiler characterized by comprising set value increasing and changing means for increasing the set value of the lower combustion air flow rate in accordance with the increase in the amount of mirabilite mixed in when the amount of mirabilite detected by the means increases. Air flow control device for use. (2) The mirabilite amount detection means includes a density meter that detects changes in the density of the injected black liquor injected into the recovery boiler, and an S that detects changes in the SO_2 concentration contained in the combustion exhaust gas of the recovery boiler.
an O_2 concentration meter, a CO_2 concentration meter that detects a change in the CO_2 concentration contained in the exhaust gas, an in-furnace thermometer that detects the furnace temperature of the recovery boiler, and a steam amount detection means that detects the main steam flow rate of the main steam line. The combustion air flow rate control device for a recovery boiler according to claim (1), which detects any one or a combination of a plurality of types.