JPH081294B2 - Boiler soot blow control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a recovery boiler used in a pulp manufacturing plant, a coal-fired boiler used in various other industries, a waste heat boiler, and the like. The present invention relates to a soot blow control device suitable for use in a boiler that generates a large amount of dust.

(Prior Art) Generally, in a pulp manufacturing plant, after introducing black liquor discharged as waste liquid from a chip cooking process to a heating unit and heating it with steam, the black liquor is injected into a furnace of a boiler using an injection gun, A char bed is formed by floating and drying the jetted black liquor and landing it on the bottom of the furnace. Here, combustion air is being sent into the furnace, the upper part of the char bed is combusted, and the combustion exhaust gas generated at this time is generated by the combustion chamber water cooling wall,
It is finally discharged from the chimney through the superheater (superheater) in the upper part of the furnace, the main bank in the exhaust gas line, the heat transfer part such as the economizer. On the other hand, the water supplied from the water supply line passes through the economizer, the main body bank, the super heater and the water cooling wall of the combustion chamber, and heat exchange with the combustion exhaust gas is performed by these elements to be taken out as main steam. Further, the reduction reaction at high temperature atmosphere over the char bed is performed, etc. mirabilite in black liquor (Na ₂ SO ₄₎ next to sodium sulfide (Na ₂ S), sodium carbonate ((Na
₂ CO ₃ ) and the like are recovered as smelt, which is a raw material of the chemical used in the chip cooking step, from the spoutro at the bottom of the boiler furnace.

By the way, in the above-mentioned boiler, dust generated by the combustion of the char bed adheres to the heat transfer portion, which causes the heat exchange rate to decrease with time. Therefore, in order to remove dust adhering to the surface of the heat transfer part, a normal boiler is divided into heat transfer parts and a plurality of soot blow lances are attached to the boiler wall part, etc., and the soot blow operation signal is sent from the control device. To remove dust by operating the soot blow lance as a group for each heat transfer section in a predetermined operation sequence and at a predetermined time interval.

However, in this case, since the soot blow lance blowing order and the blowing time interval are constant, the amount of dust adhered may gradually increase with the passage of time depending on the setting of the time and order. In this case, it becomes difficult to sufficiently remove the dust, and the heat exchange efficiency of each heat transfer unit is extremely reduced. In particular, if the heat exchange efficiency in the superheater part is reduced, it becomes difficult to secure the main steam temperature, which is one of the important indexes in the boiler, and the turbine connected to the boiler and each process are seriously adversely affected.
In order to prevent such a problem, it is conceivable to set the operation interval of the soot blow lance to be short and increase the frequency of soot blow. However, if the frequency of sootblowing is increased, an unnecessary sootblowing operation is sometimes performed, resulting in an increase in the amount of steam used for sootblowing, which causes a problem of energy saving.

(Problems to be Solved by the Invention) As described above, in the conventional boiler soot blow control device, the dust removal effect is low, the heat exchange efficiency is lowered due to the dust adhesion, and the main steam temperature is lowered, and the turbine And the adverse effects on each process were unavoidable. Also, the solution could not respond to changes in operating conditions because of insufficient energy saving measures.

Therefore, the present invention can enhance the effect of removing dust adhering to the superheated portion without increasing the amount of steam used for sootblowing, can secure the main steam temperature, and can improve the turbine or turbine connected to the boiler. An object of the present invention is to provide a soot blow control device for a boiler that does not have a bad influence on other processes.

[Structure of the Invention] (Means for Solving Problems) The present invention relates to a soot blower of a boiler that operates a plurality of soot blow lances provided toward an overheated portion of a boiler to remove dust adhering to the overheated portion. In the control device, main steam flow rate detecting means for detecting the main steam flow rate of the boiler, main steam temperature detecting means for detecting the temperature of the main steam generated from the boiler, and an output signal from the main steam flow rate detecting means. When it determines that the amount of main steam used has increased, it outputs a control command for the soot blow lance, and thereafter there is no change in the amount of main steam used, and the temperature detection signal from the main steam temperature detection means has a preset lower limit temperature. Soot blow control command means for outputting a control command for the soot blow lance when the set level is reached, and control from the soot blow control command means It is obtained by a soot-blowing operation control means for controlling the soot-blowing operation by the soot blowing lance in accordance with the decree.

(Operation) With a soot-blowing control device for a boiler that employs such means, when the usage amount of the main steam flow rate from the boiler increases, the soot-blowing operation is controlled, dust is removed from the heating part of the boiler, and the superheating part is used. By increasing the heat exchange rate of the main steam, the rapid decrease of the main steam temperature that decreases with the increase of the water supply amount is prevented. When the dust adheres and the main steam temperature reaches the preset lower limit temperature setting level, the soot blow operation is controlled again, and the dust is removed from the overheated part of the boiler to increase the heat exchange rate in the overheated part. It will be possible.

(Example) Hereinafter, one example in which the apparatus of the present invention is applied to a recovery boiler used in a pulp manufacturing plant will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a recovery boiler in a pulp manufacturing plant including a soot blow control device of the present invention. In the figure, reference numeral 1 denotes a combustion chamber of a recovery boiler, in which the black liquor A discharged as waste liquid from the chip digesting process passes through a black liquor tank 2 and a heating unit (not shown), and an injection gun 3 The jet black liquor floats and dries in the furnace, falls, and the char bed 4
To form. The combustion of the char bed 4 is promoted by the combustion air B supplied from the upper and lower air supply ports 5a and 5b, and at this time, the reduction reaction is performed in the high temperature atmosphere on the char bed 4, and the sodium sulfate in the black liquor (Na ₂ SO ₄ ) becomes sodium sulfide (Na ₂ S), and sodium carbonate ((Na ₂ SO ₄ )
₂ CO ₃ ), etc., and from the spoutro 6 at the bottom of the combustion chamber, smelt C, which is the raw material of the chemical used in the chip cooking process.
Will be collected as Further, the combustion exhaust gas D generated by the combustion of the char bed 4 is discharged from the chimney 8 through the exhaust gas passage line 7.

On the other hand, in order to effectively use the heat quantity of the exhaust gas D,
Around the combustion chamber 1 is a water cooling wall, a super heater 9 is provided in the upper part, a main body bank 10 and an economizer 11 are provided in the middle of the exhaust gas passage line 7, and water E supplied from a water supply line 12 is the economizer 11 described above. , Body bank 10,
The heat is exchanged by passing through the heat transfer portion such as the super heater 9 and the water cooling wall of the combustion chamber, and is taken out as the main steam F. A part of the water supply E is introduced into the temperature reducer 16 through the water injection line 15 and is controlled so that the main steam temperature becomes constant. Furthermore, in order to remove adhered dust that hinders heat exchange in the superheater 9, main body bank 10, economizer 11, etc., a plurality of steam blow soot blow lances are installed toward the boiler heater wall surface toward the superheater 9, main body bank 10 and economizer 11. Etc.

It should be noted that FIG. 1 shows only soot blow lances a to f for the super heater 9. These soot blow lances a to f are controlled by a soot blow operation control section for super heater (hereinafter abbreviated as blow operation) 18 in response to a control command from a soot blow control instruction section for a super heater (hereinafter abbreviated as blow control instruction section) 17. The soot blow operation is controlled.

Here, the blow control command unit 17 is the main steam line 21.
Flow rate detection signal S1 from the main steam flow rate detector 20 installed in
A control command is output based on the temperature detection signal S2 from the main steam temperature detector 22, and specifically has the configuration shown in FIG. That is, as shown in FIG.
The flow rate detection signal S1 is taken into the main steam flow rate input section 31, and the change detection section 32 uses this main steam flow rate input section 31.
The fluctuation of the flow rate detection signal S1 taken in by 31 is monitored, and when the increase fluctuation of the main steam flow rate over a certain range is detected, the pulse signal P1 is sent to the command pulse output section 33. On the other hand, the temperature detection signal S2 is taken into the main steam temperature input section 34, and the temperature drop detection section 35 monitors the level of the temperature detection signal S2 taken into the main steam temperature input section 34. , When the lower limit level setting unit 36 detects that the temperature has dropped below the preset temperature level, the pulse signal P2
Is sent to the command pulse output unit 33. The command pulse output unit 33 is composed of a logical sum circuit, and when at least one of the pulse signals P1 and P2 from the change detection unit 32 or the temperature drop detection unit 35 is input, a start command pulse to the blow operation control unit 18 Outputs signal P3.

FIG. 3 is a block diagram showing a specific configuration of the blow operation control unit 18. In the figure, the upper lance drive unit 41
The blow start signal Qac is sent simultaneously to the upper lances a to c of the soot blow lances a to f for the superheater 9 in response to the input of the start command pulse signal P3. Further, the lower lance drive unit 42 responds to the input of the start command pulse signal P3 by the super heater 9
The blow start signals Qd, Qe, and Qf are respectively sent to the lower lances d to f of the soot blow lances a to f, and these blow start signals Qd, Qe, and Qf are sent to the order setting unit 43. By the action of the delay circuit 44 according to the lance sequence set as described above, the signals are intermittently transmitted at a constant time interval.

In the present embodiment configured as described above, the flow rate of the main steam F flowing through the main steam line 21 is always detected by the main steam flow rate detector 20, and the flow rate detection signal S1 indicates the main steam flow rate of the blow control command unit 17. The temperature of the main steam F supplied to the input unit 31 and flowing through the main steam line 21 is detected by the main steam temperature detector 22, and the temperature detection signal S2 is output to the main steam temperature input unit 34 of the blow control command unit 17. Is given to. And
The change detection unit 32 of the blow control command unit 17 monitors the fluctuation of the main steam flow rate, and the temperature drop detection unit 35 monitors the decrease of the main steam temperature.

In this state, if the amount of main steam F used in the turbine or other processes connected to the recovery boiler increases and the flow rate detection signal S1 fluctuates in the increasing direction at time t1 in FIG. As a result, the change detection unit 32 outputs the pulse signal P1, and the command pulse output unit 33 outputs the start command pulse signal P3 to the blow operation control unit 18. Then, the blow activating signal Qac is output from the upper lance drive unit 41 to the soot blow lances a to c according to the fall of the start command pulse signal P3, and the lower lance drive unit 42 outputs to the soot blow lances d to f. Order setting section
The blow start signals Qd, Qe, and Qf are opened according to the order set by 43 while opening a time interval of the delay time T of the delay circuit 44.
Are sequentially output. As a result, the soot blow lances a to f facing the superheater 9 perform soot blow operation at appropriate times, the dust attached to the upper side of the superheater 9 is removed at once by the soot blow lances a to c, and the dust is attached below by the soot blow lances d to f. Dust is intermittently removed little by little. As a result, the heat exchange efficiency in the superheater 9 is improved, and a rapid decrease in the main steam temperature, which started to decrease with an increase in the amount of water supplied, is prevented.

After that, if the amount of the main steam F used does not change, the combustion state in the furnace becomes violent, so that dust is likely to adhere to the super heater 9 and the like. For this reason, the heat exchange efficiency of the super heater 9 decreases, and the temperature of the main steam F gradually decreases. When the main steam temperature detected by the main steam temperature detector 22 reaches the lower limit temperature level L preset by the lower limit setting unit 36 at time t2 in FIG. Outputs a pulse signal P2, which causes the command pulse output unit 33 to output a start command pulse signal P3. Then, in the blow operation control unit 18, the soot blow lances a to c simultaneously perform soot blow, and the soot blow lances d to f control the blow actions of the respective lances a to f so as to perform them intermittently in the same manner as described above. Thus, soot is blown every time dust adheres to the superheater 9 to lower the main steam temperature, and the removal of dust increases the heat conversion efficiency of the superheater 9 to prevent the main steam temperature from decreasing.

As described above, according to the present embodiment, the main steam temperature starts to decrease as the usage amount of the main steam F increases, but at this time, the dust adhering to the super heater 9 is caused by the soot blow lances a to f. Since it is removed, the heat conversion efficiency in the superheater 9 is enhanced, and a rapid decrease in the main steam temperature can be prevented. Further, if dust adheres to the superheater 9, the heat exchange efficiency decreases, so the main steam temperature decreases, and eventually the lower limit temperature level set by the lower limit setting unit 36 is reached. Since the soot blowing operation removes dust and enhances heat conversion efficiency, it is possible to prevent the main steam temperature from decreasing. Therefore, since the desired temperature of the main steam F is always ensured, there is no fear that the turbine connected to the recovery boiler and each process will be adversely affected by the temperature decrease of the main steam F. Further, since the soot blow operation is executed only when the soot blow to the super heater 9 is requested,
It is not against energy saving and can be implemented easily. Further, the dust may drop on the char bed 4 due to the soot blowing action on the super heater 9 to collapse the char bed 4, resulting in poor combustion. However, in the present embodiment, the soot blow lance d provided below the super heater 9 Since ~ f is operated intermittently one by one, dust does not drop on the char bed 4 little by little, and the char bed 4 is not destroyed.
Therefore, a stable combustion state can always be obtained.

The present invention is not limited to the above embodiment. For example, in the above-mentioned embodiment, the case of applying to a recovery boiler for black liquor combustion used in a pulp manufacturing plant is shown, but soot blow control for the superheated part of various boilers such as coal-fired boilers and waste heat boilers in other plants. It goes without saying that it can be applied as a device. In addition, it goes without saying that 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 main steam flow rate of the boiler is detected by the main steam flow rate detection means, and the temperature of the main steam generated from the boiler is detected by the main steam temperature detection means. When the output signal from the main steam flow rate detection means determines by the soot blow control command means that the usage amount of the main steam is increased, a soot blow lance control command is output from the soot blow control command means, and the soot blow control is issued according to this control command. The sootblowing operation of the lance is controlled by the sootblowing operation control means, and thereafter the amount of main steam used does not change and the temperature detection signal from the main steam temperature detection means reaches the lower limit temperature setting level preset by the sootblowing control command means. If it is determined that the soot blow lance control command is issued again from the soot blow control command means. The soot blow operation of the soot blow lance is controlled by the soot blow operation control means in response to this control command, so that the effect of removing dust adhering to the heating section can be achieved without increasing the amount of steam used for soot blow. It is possible to provide a soot blow control device for a boiler that can be increased and can secure the main steam temperature and does not adversely affect the turbine or other processes connected to the boiler.

Further, since the soot blow control command means outputs the start command to the soot blow lance based on only one piece of information such as the main steam flow rate or the main steam temperature of the boiler, it can be realized with a simple hardware configuration and can be calculated. Therefore, the dust adhesion can be immediately detected and the reliability can be improved without generating the waiting time due to the calculation cycle.

Further, since the soot blow lance is operated intermittently by a predetermined number by the soot blow operation control means, dust is not dropped little by little and the char bed is not destroyed, so that the combustion state can be always stabilized.

[Brief description of drawings]

1 to 4 are diagrams showing an embodiment in which the present invention is applied to a recovery boiler, FIG. 1 is a system diagram showing a schematic configuration of the embodiment, and FIG. 2 is a blow control command unit. FIG. 3 is a block diagram showing a specific structure, FIG. 3 is a block diagram showing a specific structure of the blow operation control unit, and FIG. 4 is a time chart for explaining the soot blow operation. 1 ... Combustion chamber, 4 ... Char bed, 9 ... Super heater, 12
… Water supply line, 15… Water injection line, 16… Desuperheater, 17… Blow control command section, 18… Blow operation control section, 19… Black liquor line, 20… Main steam flow detector, 21… Main steam line, 22 … Main steam temperature detector, 32… Change detection unit, 33… Command pulse output unit, 35… Temperature drop detection unit, 36… Lower limit setting unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshikazu Fukushima, 1-chome, 1-chome, Jujo-machi, Yatsushiro-shi, Kumamoto Inside the Yatsushiro Mill, Jujo Paper Co., Ltd. Papermaking Co., Ltd. Yatsushiro Mill (72) Inventor Takashi Tanihara 4-135 Shimaya, Konohana-ku, Osaka City, Osaka Prefecture Kawasaki Heavy Industries, Ltd. Osaka Mill (72) Inventor Toshiyuki Ifoko 1 Kawasaki-cho, Akashi-shi, Hyogo Prefecture No. 1 Kawasaki Heavy Industries, Ltd. Akashi Factory (72) Inventor Shiro Nakabayashi 1-1 Kawasaki-cho, Akashi-shi, Hyogo Prefecture Kawasaki Heavy Industries Ltd. Akashi Factory (72) Inventor Kazuyuki Iizuka 1-1-1, Shibaura, Minato-ku, Tokyo No. 1 in Toshiba Headquarters office (72) Inventor Ryuichi Kuwata No. 1 Toshiba-cho, Fuchu-shi, Tokyo Inside Toshiba Fuchu factory (72) Inventor Kumaki Husband, No. 1 in Toshiba Town, Fuchu, Tokyo (72) Inventor Atsushi Muramatsu Atsushi Muramatsu No. 1 in Toshiba Town, Fuchu, Tokyo Tokyo (56) Reference: JP-A-57-87528 (JP, 57-87528) A)

Claims (2)

[Claims] 1. A soot blow control device for a boiler that operates a plurality of soot blow lances provided toward an overheated portion of a boiler to remove dust adhering to the overheated portion, and detects a main steam flow rate of the boiler. Steam flow rate detection means, main steam temperature detection means for detecting the temperature of the main steam generated from the boiler, and the soot blow when it is determined that the usage amount of the main steam has increased by the output signal from the main steam flow rate detection means. The soot blow lance control command is output when a lance control command is output, and thereafter it is determined that the main steam usage amount has not changed and the temperature detection signal from the main steam temperature detection means has reached the set lower limit temperature setting level. Outputting soot blow control instruction means, and the soot blow run command in response to a control instruction from the soot blow control instruction means. A soot blow control device for a boiler, comprising soot blow operation control means for controlling a soot blow operation by a soot. 2. When the control command from the soot blow control command means is input, the soot blow operation control means simultaneously outputs a start signal to the upper soot brolance and to the lower soot brolance. The soot blow control device for a boiler according to claim (1), wherein a start signal is intermittently output by a predetermined number each to control the soot blow operation by the soot brolance.