JPS6229821A - Device for reducing concentration of so2 of recovery boiler - Google Patents

Abstract

PURPOSE:To improve a control performance by a method wherein a temperature of injected black liquor is controlled by a concentration of SO2 in combustion gas in a concentration reducing device for a recovery boiler in a pulp manufacturing process. CONSTITUTION:When a concentration S1 of SO2 output from a SO2 concentration detector 17 is input to an incomplete differentiator 18, a positive incomplete differentiating signal is output S2 to a limiter 19 when a concentration of SO2 is increasing and in turn a negative incomplete differentiating signal is output S2 to the limiter 19 when a concentration of SO2 is decreasing. The limiter 19 invalidates a negative signal and when the positive signal less than the upper limit value is found, it generates an output proportional to an input level and in turn when it exceeds an upper limit value, it generates a specified output irrespective of an input level and the signal is input to an adder 20 as a black liquid temperature correction signal S3. The adder 20 adds the signal S3 to an injected black liquor temperature setting value signal S4, outputs a black liquid target temperature T1 to a black liquid temperature controller 22 so as to control the black liquid temperature. In this way, a control performance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus used for operational management of a recovery boiler in a paper production process, and particularly relates to an apparatus for controlling the operation of a recovery boiler in a paper production process. This invention relates to improvements in means for reducing the degree of damage.

[Conventional technology]

Generally, in the paper production process, a recovery boiler is used that burns black liquor produced as waste liquid from the pulp cooking process to generate steam used for power generation, etc., and recovers pulp cooking chemicals. In this recovery boiler, when predistributed black liquor is injected into the furnace by the black liquor injection mechanism, this black liquor floats and dries to form a char bed at the bottom of the furnace, and a reduction reaction occurs on this char bed. By burning, steam is generated and the drug is recovered.

By the way, the black liquor injected into the recovery boiler contains sulfides. Therefore, when it is combusted, there is a risk that SO2 will be included in the exhaust gas. This SO2 is a pollutant,
It must be suppressed to below the regulation value and discharged outside. Therefore, conventionally, the SO2 concentration has been controlled by adjusting the amount of combustion air introduced into the recovery boiler to change the combustion state.

[Problem that the invention seeks to solve]

However, in the recovery boiler, in order to increase the recovery efficiency of sodium components, the sodium sulfate (Na2SO4) contained in the combustion exhaust gas is recovered, and after mixing this sodium sulfate with the black liquor, it is reinjected into the boiler. Although it is designed to be injected and combusted, the rate at which the Glauber's salt is recovered, ie, mixed into the black liquor, is subject to fluctuations depending on various factors. This variation in the amount of mirabilite mixed in immediately affects the SO211 degree in the combustion exhaust gas. Therefore, it has not been possible to sufficiently control SO211 degrees by adjusting the amount of combustion air as described above.

Therefore, the present invention enables highly accurate control of SO2IIy1@ contained in the combustion exhaust gas discharged from the recovery boiler, and
It is an object of the present invention to provide a 302 concentration reduction device for a recovery boiler that can quickly suppress the temperature increase by 29 degrees.

[Means for solving problems]

In order to solve the above problems and achieve the objectives, the present invention has the following features:
The temperature of the black liquor injected into the recovery boiler is detected, and the detected black liquor temperature is adjusted to a predetermined injection black liquor temperature setting value, and the 5o2I! The temperature setting value of the injected black liquor is controlled according to the detected SO211 degree.

[Effect]

By taking such measures, the present invention provides 502
The black liquor temperature changes according to the variation of m degrees, and the variation of 502a degrees is suppressed.

[Example] In explaining the present invention in detail below, first, the principle of the present invention will be explained. The following principle has been clarified through investigation of various characteristics of recovery boilers. That is, when the temperature of the injected black liquor serving as fuel is increased, the SO2 concentration in the combustion exhaust gas decreases transiently. Furthermore, in the long term, there is an injection black liquor temperature at which the SO2 concentration in the combustion exhaust gas is at a minimum.

The present invention has been made based on the above principle, and examples of the present invention will be described below.

FIG. 1 is a system diagram showing the configuration of a first embodiment of the present invention. In the figure, reference numeral 10 denotes a recovery boiler, into which black liquor 11 is injected by an injection gun 12. This injected black liquor 11 is transferred to a recovery boiler 10.
It floats and dries inside the furnace, settles on the bottom of the furnace, and forms a char bed 13.
form.

A reduction reaction takes place in the high-temperature atmosphere above the char bed 13, and the mirabilite in the injected black liquor 11 is recovered as sodium sulfide (Na2s) and reused as a pulp cooking agent.

Further, the combustion gas of the black liquor combusted by the high temperature atmosphere of the char bed 13 rises as shown by arrow A in the figure, and is cooled by exchanging heat with various heat exchangers 14 in the boiler 10. 1o is discharged outside. After the dust in the combustion gas is collected by an electric precipitator 15, it is released into the atmosphere from a chimney 16 as combustion exhaust gas.

On the other hand, in FIG. 1, 17 is an SO2'a degree detector, which detects 5O2a degrees in the combustion exhaust gas and
2 Electrical signal according to concentration 5O21! It is output to the incomplete differentiator 18 as a degree signal S1. This incomplete differentiator 18 incompletely differentiates the S○2i1 degree signal S1 and sends an incomplete differential signal S2 to the limiter 19. In other words, when the SO2411 degree increases, it sends a positive incomplete differential signal. However, when 502arti falls, it emits a negative incomplete differential signal. The limiter 19 cuts the incomplete differential signal S2 when it is a negative signal, and when it is a positive signal and is below the upper limit value, it transmits an output proportional to the input level, and when the signal exceeds the upper limit value, it outputs an output proportional to the input level. In this case, a constant output is transmitted regardless of the input level and supplied to one input terminal of the adder 20 as the black liquor temperature correction signal S3, and the other input terminal of the adder 20 is , a black liquor temperature setting signal S4 is supplied in accordance with the black liquor temperature setting value set by the injection black liquor temperature setting device 21. Then, in the adder 2o, the black liquor temperature setting value is compensated by adding the black liquor temperature compensation signal S3 to the black liquor temperature setting signal s4, and outputted to the black liquor temperature controller 22 as the black liquor target temperature T1. It has become a thing.

Further, the jet black liquor supply line 23 that supplies the jet black liquor 11 to the jet gun 12 is provided with a black liquor temperature detector 24 for detecting the temperature of the jet black liquor 11. The injected black liquor temperature T2 detected at is outputted to the black liquor temperature controller 22. In this black liquor temperature controller 22, the injection black liquor temperature T2 is set to the black liquor target temperature T.
1, the heating type of the black liquor heater 26 that heats the black liquor 25 discharged from the pulp cooking process is feedback-controlled.

In the water system constructed in this way, 5C)z! 1 degree is constantly detected by the SO211 degree detector 17, and when this SO2'a degree falls, the incomplete differential signal unit 18 outputs a negative incomplete differential signal S2. However, since this negative incomplete differential signal $2 is cut by the limiter 19, the black liquor temperature compensation signal s3 is not transmitted, and the jet fJJ black liquor temperature D2 does not change.

On the other hand, when the SO28 degree in the combustion exhaust gas increases, the incomplete differentiator 18 outputs a positive incomplete differential signal S2. Then, in response to this incomplete differential signal S2, the limiter 19 outputs a black liquor temperature compensation signal s3 that increases the jetted black liquor temperature T2, and is added to the jetted black liquor temperature setting signal s4 by the adder 2o. A liquid target temperature T1 is calculated. Then, the heating amount of the black liquor heater 26 is feedback-controlled by the black liquor temperature controller 22 so that the injected black liquor temperature T2 becomes the black liquor target temperature T1. The jetted black liquor temperature T2 is kept at a temperature slightly lower than the boiling point of black 125, and since the jetted black liquor temperature T2 must not exceed the boiling point, the limiter 19 sets an upper limit to the black liquor temperature setting signal. is provided to prevent excessive compensation.

By the way, between the injection black liquor temperature T2 and the SO2 concentration in the combustion exhaust gas, as shown in FIG. 2, there is a tendency for the SO2 concentration to decrease transiently as the injection black liquor temperature T2 is increased.

Therefore, according to this embodiment, 5
When O2i11 degrees rises, IIJ! The black liquor target temperature T1 is calculated by performing compensation such as the injection black liquor temperature injection killing liquid temperature setting value, and the black liquor heater 26 is turned on so that the black liquor injection temperature T2 matches the black liquor target temperature T1. As a result, the temperature of the injected black liquor 11 is increased.
As is clear from Figure 2, S in the combustion exhaust gas is
O2!1 degree rise is suppressed.

In this way, even if the temperature in the combustion exhaust gas rises by 502 m degrees due to disturbances such as an increase in mirabilite mixed into the black liquor 25, this rise can be quickly suppressed, so that the pollutant SO2 can be constantly kept at the regulated value. This makes it possible to perform stable boiler operation.

On the other hand, it has been found that there is a jet black liquor temperature at which 5O2 II degrees is the minimum in the long term between the jet black liquor temperature and the SO2 concentration. Therefore, it is possible to search for extreme values using a well-known algorithm such as the climbing method to find and maintain the optimum injection black liquor temperature, thereby keeping the SO211 degrees at a minimum.

FIG. 3 is a system diagram showing the configuration of a second embodiment of the present invention using this extreme value search method. This embodiment differs from the first embodiment in that an incomplete differential signal generator 18 and a limiter 19
The point is that an extreme value searcher 30 is provided instead of , and the other parts are the same, so the same reference numerals are given and detailed explanation will be omitted.

The extreme value searcher 30 operates as follows, for example: First, it takes in the injection black liquor temperature T2 detected by the black liquor temperature detector 24, and sets this black liquor temperature T2 to a predetermined temperature of 6. A black liquor temperature compensation signal S3 is outputted to the adder 20 to increase the black liquor temperature T by
2 rises by 6 predetermined temperatures, which causes a fluctuation of 502 m degrees. At this time, if the SO2 concentration decreases,
Once again, the @i temperature compensation signal S3 is outputted to increase the injected black liquor temperature T2, and conversely, when the SO2 concentration increases, the black liquor temperature compensation signal S3 is outputted to lower the injected black liquor temperature T2. Then, the fluctuation in SO2 concentration is examined again.

From then on, this operation is repeated to find the injection black liquor temperature T2 at which 5O21i degrees is the minimum, and this value is held.

In this way, according to this embodiment, the injected black liquor temperature T2 at which SO211 degrees is the minimum is found by the hill-climbing method and this value is maintained, so that the 5O211 J degrees contained in the combustion exhaust gas is always at the minimum. It is controlled to be the value. Therefore, since the SO2 concentration can be suppressed to a level considerably lower than the regulation value, more stable boiler operation can be performed. In addition, the optimal black liquor injection temperature changes when disturbances occur or plant conditions change, but in such cases, by searching for extreme values again and finding the optimal temperature according to the situation, it is possible to always maintain the same temperature. Stable S02'a degree control becomes possible.

It should be noted that the present invention is not limited to the above embodiments. For example, in the second embodiment, the extreme value searcher 30 uses the hill climbing method to obtain SO21! Although we have shown the case where the injection black liquor temperature 1]iT2 with the minimum margin is found, data of multiple sets of injection black liquor 1 degree T2 and the corresponding 502 m 1 degree is obtained, and from these data, the injection black liquor temperature T2 is found. 50 against
Calculate the function of 21 degrees by the method of least squares 'a, and set the variable (a (injected black liquor 1) that minimizes the function value (SO28 degrees)
degree) may be calculated and output. Further, in the second embodiment, the case where the injection black liquor 'Ia degree 2 is detected and the extreme value search is performed is shown, but the injection black liquor temperature setting value set by the injection black liquor temperature setting device 21 is It is also possible to calculate the injection black liquor temperature T2 at which SO211 degrees is the minimum using this set value as a standard. It goes without saying that various other modifications can be made without departing from the gist of the present invention.

(Effects of the Invention) As described in detail above, the present invention detects the temperature of the black liquor injected into the recovery boiler, and the detected black liquor temperature becomes a predetermined injection black liquor temperature setting value. In addition to adjusting the
5O2i in the combustion exhaust gas of the recovery boiler! 1 degree Celsius, and the temperature setting value of the injected black liquor is controlled according to the detected SO2 concentration.

Therefore, according to the present invention, the black liquor temperature changes in accordance with fluctuations in the 302 concentration, and fluctuations in S○2'a degrees are suppressed υ1. It is possible to provide an SO2 18 degree reduction device for a recovery boiler that can control the SO2 concentration with high precision and quickly suppress the SO2 temperature when it rises.

[Brief explanation of drawings]

1 and 2 are diagrams showing one embodiment of the present invention, in which FIG. 1 is a system diagram showing the configuration, and FIG. 2 is a relationship between the injected black liquor temperature and SO2 concentration in a transient state. A diagram showing
FIG. 3 is a system diagram showing the configuration of a second embodiment of the present invention. 10...Recovery boiler, 11...IIJl black liquor, 1
7... SO2I 11 degree detector, 18... Incomplete differential calculator, 19... Limiter, 20... Adder, 21
... Injection black liquor temperature setting device, 22... Black liquor temperature controller, 24... Black liquor temperature detector, 25... Black liquor heater,
3o... profit value searcher. Applicant's agent Patent attorney Takehiko Suzuta Figure 1 Black bottle 7! T2 Procedural amendment 1. Display of the case Japanese Patent Application No. 60-169003 2, Name of the invention SO2 concentration reduction device for recovery boiler 3, Relationship with the old case for amendment Patent applicant Jujo Paper Co., Ltd. (and 2 others) 4. Agent Tokyo 17 Mori Building 5, 1-26-5 Toranomon, Minato-ku,
Voluntary Amendment 7, Contents of Amendment (1) The scope of claims is corrected as shown in the attached sheet. 2) "Paper production process" on page 2, line 11 of the specification is corrected to "pulp production process." 3) “Generally,
〜recovery'' [Generally, in the pulp production process,
The black liquor produced as waste liquid from the chip cooking process is burned to generate steam used for power generation, etc., and the chemical raw material for chip cooking is recovered]. (4) In the same book, page 3, lines 2 to 5, "This charbed is burning. Steam is generated by the combustion of this charbed, and drug raw materials are recovered by the reduction reaction at that time. It has become a thing,” he corrected. 5) Delete "Setting value" on page 4, line 15. (6> Delete “setting value” on page 4, line 18 of the same book. (7) Delete “2nd value” after “transitionally” on page 5, line 8 of
Insert the phrase "as shown in the figure. (8) On page 5, line 9 of Domon, next to “in the long term” there is “4th
Insert the phrase "as shown in the figure. (9) In the same book, page 7, lines 19 and 20, "output." is corrected to "input." (10) "Pulp cooking process" in the second line of page 8 of the same book is corrected to "chip cooking process." (11) In the second line of page 9 of Domon, the phrase "the heating button gives feedback" is corrected to "the heating l is operated and gives feedback." (12) Insert the words ``as shown in Figure 4'' next to ``in the long term'' in lines 6 and 7 of page 10 of the same book. (13) Next to ``For example'' on page 12, line 7 of the same book, ``In the above embodiment, the injection black liquor temperature is set to a predetermined injection black liquor temperature setting value in Section 11, and the injection black liquor temperature setting value is SO
2. This was explained using an example of controlling according to the concentration.
It goes without saying that the black liquor temperature may be directly controlled in accordance with SO21 degrees. Also, insert the phrase ". (14) Delete "1 setting value" on page 13, line 7 of the same book. (15) Delete "Setting l1lI J" on page 13, line 10 of the same book. (16) Next to "System diagram" on page 14, line 4 of the same book, ", Figure 4 shows the injection black liquor temperature and 5021! Insert the phrase "Diagram showing the relationship in a long-term state with 1 degree". (17) Figure 2 of the drawing is corrected as shown in the attached sheet. (18) Add Figure 4 of the drawing. 2. Claims (1) In a recovery boiler that burns black liquor discharged from the Kuyu I cooking process to generate steam and recovers chemical raw materials for chip cooking, black liquor injected into the recovery boiler. A black liquor temperature detection means for detecting the temperature of the liquid, an SO2 concentration detection means for detecting 5O21 degrees in the combustion exhaust gas of the recovery boiler, and an SO2 concentration detection means for detecting the SO2 concentration detection means.
1. An apparatus for reducing SO211 degrees in a recovery boiler, comprising: an injection black liquor temperature control means for controlling the injection black liquor temperature according to a temperature of 2 ml degrees. (2) The injected black liquor temperature control means is configured to change the injected black liquor temperature so as to suppress the increase when the temperature increases by 5021II degrees. 502 of the recovery boiler described in (1)
S degree reduction device. (3) The SO2 concentration reduction device for a recovery boiler according to claim (1), wherein the injection black liquor temperature control means has a length of 502 m.

Claims (3)

[Claims] (1) In a recovery boiler that burns the black liquor discharged from the pulp cooking process to generate steam and recover pulp cooking chemicals, the black liquor temperature is detected to detect the temperature of the black liquor injected into the recovery boiler. a detection means, an injection black liquor temperature adjustment means for adjusting the black liquor temperature detected by the black liquor temperature detection means to a predetermined injection black liquor temperature setting value, and an SO_2 concentration in the combustion exhaust gas of the recovery boiler. and an injected black liquor temperature set value control means that controls the injected black liquor temperature set value according to the SO_2 concentration detected by the SO_2 concentration detecting means. SO_2 concentration reduction device for recovery boiler. (2) A patent characterized in that the jetted black liquor temperature set value control means is configured to change the jetted black liquor temperature set value so as to suppress the increase when the SO_2 concentration increases. An SO_2 concentration reduction device for a recovery boiler according to claim (1). (3) The jetted black liquor temperature set value control means is configured to change the jetted black liquor temperature set value by an extreme value search method so that the SO_2 concentration is minimized. The SO_2 concentration reduction device for a recovery boiler according to the scope item (1).