JPH0765729B2 - Boiler automatic control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a boiler automatic control device for a thermal power plant, and is particularly suitable for preventing a sudden change in steam temperature during soot blower injection into a heat transfer section. Boiler steam temperature control method.

[Conventional technology]

The boiler steam temperature control method is described in “Automatic control of boiler” (Ohm Co., Ltd.), pages 23 to 25, 2.6 Super (re) heater and steam temperature controller, and pages 260 to 263, 4, 6 steam temperature control. As described above, the generated steam is controlled to the rated steam temperature by the primary and secondary superheaters and the spray desuperheater, and the reheated steam controls the amount of flue gas passing through the reheater by the gas recirculation damper. , The rated steam temperature is secured. However, as for the soot blower control method, as shown in 9.1 Soot blower control on page 207 of "Automatic control of boiler" above, the scale adheres to the heat transfer surface of the boiler to reduce the heat transfer rate, The boiler heat absorption balance shifts, so the steam temperature does not rise to the rated temperature. In a naphtha-burning plant, soot blowers are injected into about 30 places in the entire boiler in a cycle of about 4 hours), but this is removed, but the effect on the steam temperature due to this soot blower injection is taken into consideration. It was never done.

[Problems to be solved by the invention]

The above-mentioned conventional technology does not consider the influence on the steam temperature due to the soot blower injection, and the steam temperature suddenly fluctuates with the improvement of the steam pipe heat transfer coefficient of the boiler due to the soot blower injection, causing a large disturbance of the plant. There was a problem that became.

It is an object of the present invention to provide a device that prevents fluctuations in steam temperature due to an increase in the heat transfer coefficient of a steam pipe during soot blower injection.

[Means for solving problems]

In order to achieve the above-mentioned object, the feature of the present invention resides in that, when soot blower is injected into a plurality of superheaters, the generator output is prevented so as to prevent the main steam temperature fluctuation due to the increase of the steam pipe heat transfer coefficient. Based on the set value set for each superheater, the desuperheater spray water is controlled according to the characteristics of each superheater, and when the soot blower is injected into the reheater, the steam pipe heat transfer rate is The gas recirculation fan inlet damper is controlled by a set value that is set based on the generator output so as to prevent the reheated steam temperature fluctuation due to the rise. Further, in the present invention, when soot blower is injected into a plurality of superheaters, each superheat is based on the generator output so as to prevent main steam temperature fluctuations and reheat steam temperature fluctuations due to an increase in the steam pipe heat transfer coefficient. The fuel flow control valve is controlled by a set value set corresponding to the fuel vessel.

[Action]

When the heat transfer part hest blower is injected, the main steam temperature suddenly changes due to the heat transfer part improving the steam pipe heat transfer rate of the heat transfer part, but the fluctuation range can be minimized by the advance control of the spray or recirculation gas amount.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

An outline of the thermal power plant will be described with reference to FIG.
The thermal power plant is composed of the entire boiler 50, the turbine 2 and the generator 3, and the boiler automatic control device 101 sets the pressure and temperature of the turbine inlet steam to specified values based on the request from the load (turbine / generator). Fuel flow regulator 7 to keep
0, control the water supply flow control valve 23 and the amount of air. To further explain the flow of the combustion gas, the gas burned in the furnace is first absorbed by the furnace wall 25 and then the secondary superheater (hereinafter
2SH) 29, reheater (hereinafter RH) 52, primary superheater (hereinafter 1SH) 27, economizer (hereinafter ECO) 24, part of which is a gas recirculation fan (hereinafter GR
It is injected into the furnace from the inlet damper 53 of the (F) 54, the furnace wall (hereinafter referred to as WW) 25, the drum 26, 2SH29, RH52,1SH2.
7, Used to adjust the amount of heat transfer at ECO24, and the rest is discharged from the chimney through the air preheater. Further, as other control devices, there are a central operation panel 102 and a soot blower panel 103.

This figure will be used to explain the flow of the water vapor system in more detail. First, after the flow rate of water pressurized by the boiler feed water pump (hereinafter referred to as BFP) 22 is adjusted by the feed water flow control valve 23,
It becomes high temperature and high pressure water at ECO24, and is superheated at WW25 to become steam. This steam is separated into saturated steam and saturated water in the drum 26, superheated in 1SH27, and part of the feed water is reduced to S.
After pouring water into the desuperheater 28 via the H spray valve 15, it is heated by 2SH29 and sent to the high-pressure turbine 2. The steam that has finished work in 2 passes through the emergency RH desuperheater 105, is reheated in RH 52, and is sent to the intermediate pressure turbine 49. Part of the feed water is injected into 105 through the RH spray valve 104, and the reheat temperature is controlled.

Each heat transfer part has a steam valve (shut-off valve 30-34) for the soot blower, which opens 30-34 and blows steam to the outer wall of each heat transfer part to remove the adhered scale. The thermal efficiency is improved. A soot blower can be used for each of the valves 30 to 34 by the operator's selection.

FIG. 8 shows the behavior of the main steam temperature deviation, the steam temperature deviation at the outlet of the desuperheater, and the SH spray valve operation signal when the soot blower is input in the conventional main steam temperature control method.

When soot blower is injected into 2SH29, the main steam temperature rises sharply due to the improvement of 2SH heat transfer coefficient. The reason why the temperature rise in 2SH29 is remarkable is that 2SH29 is installed after the desuperheater 28, and direct disturbance to 2SH29 (such as 2SH
This is because there is no control means for soot blower injection).

Next, when soot blower was injected into 1SH27, similar to 2SH29, the main steam temperature increased, but it was smaller than that of 2SH. This depends on the temperature reduction effect of SH spray injection in the desuperheater 28, but a control method for temperature fluctuations seen during conventional plant operation, for example, a rapid temperature change is calculated by a differentiator, and the SH spray valve Even if the method of compensating for 15 control signals is used, the temperature rise cannot be suppressed.

Also, in soot blower injection into WW25, it appears as a negative deviation from the main steam temperature. This is because the heat absorption rate at WW25 is improved, the flue gas temperature is lowered, and 2SH29
Because the heat absorption by the flue gas in the is reduced, the main steam temperature is lowered.

Similarly, although not shown, in the reheat steam temperature control system,
When soot blower is injected into RH52, by improving RH heat transfer rate,
The reheat steam temperature rises sharply.

From the above, as a measure against a sudden change in steam temperature during soot blower injection, it is necessary to forcibly operate the SH spray valve 15 or the GRF inlet damper depending on the conditions of using the soot blower.

FIG. 1 illustrates a control circuit of the main steam temperature control system to which the present invention is applied.

1 indicates the range of the control device. When the soot blower is not used, the deviation between the signal of the main steam temperature detector 6 and the set value is calculated by the adder 7, and this deviation is calculated by the proportional integrator 8.
Obtain the setting of the outlet steam temperature of the desuperheater 28. Next, the desuperheater
The deviation between the signal of the outlet steam temperature detector 5 of 28 and the output signal of the proportional integrator 8 is calculated by the adder 9, this deviation is calculated by the proportional integrator 10, and the temperature change amount by the differentiator 11 is calculated. Is calculated by the adder 12 to control the SH spray valve 15.

Next, when using the soot blower, since the influence on the main steam temperature during the soot blower injection to each heat transfer surface is different, the conditions for using each soot blower (2SH contacts 14,1S
H is contact 16; ECO is contact 18; WW is contact 21). Regarding the SH spray valve 15 correction signal, from the main steam temperature change characteristics when using each soot blower, the correction function of SH spray valve 15 (2SH is 13 , 1SH has 15, ECO17, WW has 19 and polarity converter 20),
The generator output signal 34 is set as a base, and the correction signal is added to the SH spray valve 15.

FIG. 2 illustrates a control circuit in which the present invention is applied to the reheat steam temperature control system.

1 indicates the range of the control device. When the RH soot blower is not used, the signal of the reheat steam temperature detector 42 and the deviation of the set value are calculated by the adder 45, this deviation is calculated by the proportional integrator 46, and the temperature change amount by the differentiator 47 is calculated. Is calculated by the adder 48 to control the entrance damper 53 of the GRF 54.

Next, when using the RH soot blower, the contact condition 44 of using the RH soot blower is taken in.For the GRF inlet damper correction signal, the GRF inlet damper correction function based on the generator output from the reheat steam temperature change characteristic at the time of RH soot blower injection. Four
Set 3 to correct the GRF inlet damper 53. The same gas recirculation control can be applied to the RH gas pass damper 55, SH gas pass damper 56, and furnace hopper inlet damper.

FIG. 3 illustrates a control circuit in which the present invention is applied to a fuel flow rate control system.

1 indicates the range of the control device. First, when the soot blower is not used, the deviation between the signal of the main steam pressure detector 63 and the set value is calculated by the adder 65, and the deviation signal is calculated by the proportional integrator 66 to create the fuel command signal. . Next, the deviation between the signal of the fuel flow rate detector 64 and the fuel command signal of 66 is calculated by the adder 67, and this deviation is calculated by the proportional integrator 68 to control the fuel flow control valve 70.

Next, when using the soot blower, the conditions for using the soot blower are taken in and the fuel flow rate correction function 61 is set to the generator output signal 34
To the base. This function is set to supplement the temperature control in the main steam temperature control system and the reheat steam temperature control system when using the soot blower, but it leads to the improvement of plant efficiency by saving fuel.

FIG. 7 shows a main steam temperature characteristic curve when the control method of the present invention is adopted. As is clear from comparison between this figure and FIG. 8, it is understood that the main steam temperature deviation is + 8 ° C. or less even when the soot blower is injected, and a good result is obtained.

Next, an example at the time of soot blower injection into 2SH will be described.

Improving the 2SH heat transfer rate by injecting soot blower into 2SH29
As a result, the main steam temperature process gain is increased, which has an adverse effect on the cascade control by the reduced-temperature outlet steam temperature that has been conventionally used for main steam temperature control.

FIG. 9 shows a schematic control block of this cascade control for explanation. This cascade control is composed of a main steam temperature detector dehumidifier outlet steam temperature setting group 111 and a group 112 having a process 113 consisting of an SH spray valve and a desuperheater outlet temperature detector by this setting signal.
Here, 111 is affected by 2SH Sootblower.
Is. In 111, the transfer function of the process consisting of 2SH and main steam temperature detector is 114. From this, the optimum constant of the proportional integrator 8 of 111 is as follows.

Here, K _P : Process gain T _P : Process time constant L _P : Process dead time K _C : Optimal PI gain T _C : Optimal PI time constant.

Therefore, when 2SH sootblower is injected into the process 114, this process constant changes, and the formula (1),
The PI constant shown in (2) also changes. However, the current boiler automatic control device does not have a solution to the above problem. This means that, as shown in FIG. 8, the SH spray valve has a slow response to a rapid temperature change during soot blower injection, and the RI gain and the time constant are inappropriate values. In other words, for the case where the heat absorption balance (relationship between the steam temperature at the outlet of the desuperheater and the main steam temperature in this case), which is determined by the buff performance of the boiler, changes when the soot blower is injected into the 2SH. Cannot use the cascade control method.

From the above, when 2SH soot blower is injected into the heat transfer surface, the heat absorption rate of the heat transfer surface improves, a rapid temperature change appears without dead time, and the heat absorption balance of the boiler is lost. But I understand. Therefore, as a countermeasure for the main steam temperature control at the time of injecting 2SH sootblower, in addition to correcting the SH spray valve control signal shown in Fig. 1, the cascade control by the steam temperature at the outlet of the desuperheater is used. It can be seen that it is effective to stop the above and use a direct control method based on the main steam temperature.

FIG. 4 shows a control circuit considering the above measures. The control circuit will be described below.

1 indicates the range of the control device. First, in the case of normal control without using the 2SH sootblower, the cascade control method by the steam temperature at the outlet of the desuperheater is used. That is, the deviation between the signal of the main steam temperature detector 6 and the set value is calculated by the adder 7, and this deviation is calculated by the proportional integrator 8 to obtain the setting of the steam temperature at the outlet of the desuperheater. Next, the deviation between the signal of the steam temperature detector 5 at the outlet of the desuperheater and the output of 8 is calculated by the proportional integrator 10 to control the SH spray valve 15.

Next, the control method when using the 2SH sootblower will be described. First of all, according to the condition 4 while using the 2SH sootblower, the cascade control circuit by the steam temperature at the outlet of the desuperheater is switched to
The signal is calculated by the proportional integrator 81, which is separated by 83, and the deviation between the main steam temperature signal 6 and the set value, and the correction signal, which is calculated by the differentiator 11 for the sudden change in the main steam temperature deviation, are added.
The SH spray valve 15 is controlled by the signal summed in 82. This control circuit can solve the problems of the SH spray valve response delay when injecting 2SH sootblower and the problems of the cascade control method.

FIG. 5 shows a functional explanation flow of the present invention. First, at operation block 91, it is determined whether the boiler is using the soot blower. If the soot blower is in use, the calculation block 95 controls the fuel flow rate. Next, the operation block 92 is used to confirm the position of the soot blower. Broadly speaking, if it is a spray control system, proceed to calculation block 94, and perform SH spray valve opening correction and direct SH spray valve control by main steam temperature deviation, while if it is a gas recirculation amount control system, calculation block 93.
Go to and add the signals to correct the GRF inlet damper, gas path damper, and furnace hopper inlet damper.

Finally, the calculation block 96 determines whether the soot blower injection is completed, and if so, removes the correction signals such as the SH spray valve and the GRF inlet damper due to the use of the soot blower, and returns to the normal control method. showed that.

〔The invention's effect〕

According to the present invention, it is possible to prevent sudden fluctuations in steam temperature, which occur during soot blower injection for preventing heat transfer coefficient deterioration due to heat transfer surface scale adhesion of a boiler of a thermal power plant, so that plant operation is safe and easy. It is also effective in reducing metal fatigue of the boiler and turbine body and improving boiler efficiency.

[Brief description of drawings]

1 to 4 show a control system diagram of an embodiment of the present invention.
FIG. 5 shows a functional explanatory flow chart of the present invention in the explanation of FIGS. FIG. 6 shows a main drum system diagram and a main controller configuration diagram of a typical drum boiler. FIG. 7 shows a main steam temperature characteristic curve when the control system of the present invention is adopted. FIG. 8 shows a main steam temperature characteristic curve in the case of the conventional control method. FIG. 9 is a diagram showing a schematic control block of cascade control. 101 …… Boiler automatic controller, 29 …… Secondary superheater, 52…
Reheater, 54 …… Gas recirculation fan, 24 …… Coal saver, 25…
… Furnace wall, 23 …… water supply pump, 27 …… primary superheater.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tadashi Komada 5-2-1 Omika-cho, Hitachi-shi, Ibaraki Inside Omika factory of Hitachi, Ltd. (56) Reference JP-A-59-21902 (JP, A) JP-A-53-85201 (JP, A) JP-A-60-226604 (JP, A)

Claims (5)

[Claims] 1. A boiler steam temperature control device having a soot blower for removing scale adhering to a heat transfer surface, a superheater for maintaining a steam temperature at a turbine inlet at a rated value, and a desuperheater by spraying water, for a plurality of superheaters. In order to prevent fluctuations in the main steam temperature due to an increase in the steam pipe heat transfer rate during soot blower injection, the set value set for each superheater based on the generator output is used for each superheater. An automatic boiler control device that controls the spray water of the desuperheater according to the characteristics. 2. The apparatus according to claim 1, wherein the main steam temperature control is a cascade control method using a deviation signal between the main steam temperature and the steam temperature at the outlet of the desuperheater, and the heat transfer of the superheater metal heat transfer is performed. The main feature is that the main steam temperature response delay is compensated by the delay and the side capacity effect, and when the soot blower is injected into the secondary superheater section, a circuit is provided to switch to the direct desuperheater spray control system depending on the main steam temperature. Boiler automatic control device. 3. A soot blower for removing scale adhering to the heat transfer surface and a part of the flue gas are recirculated to the furnace, and the gas recirculation for controlling the reheat steam temperature by changing the flue gas amount and the gas temperature. In a boiler steam temperature control device having a fan, at the time of soot blower injection into the reheater, in order to prevent reheated steam temperature fluctuations due to an increase in the steam pipe heat transfer rate, a setting set based on the generator output. An automatic boiler control device characterized by controlling a gas recirculation fan inlet damper according to a value. 4. The apparatus according to claim 3, further comprising a bypass damper in which the flue is divided into a superheater side and a recirculation side, wherein the flue gas is fed to the reheater when the soot blower is injected into the superheater. An automatic boiler control device equipped with a bypass damper control circuit that sends flue gas to the superheater when sending and injecting soot blower into the reheater. 5. A boiler steam temperature control device having a soot blower for removing scale adhering to a heat transfer surface and a superheater for keeping a turbine inlet steam temperature at a rated value, wherein a steam pipe is introduced into a plurality of superheaters during soot blower injection. The fuel flow control valve is controlled by the set value corresponding to each superheater based on the generator output so as to prevent the main steam temperature fluctuation and the reheat steam temperature fluctuation due to the increase of the heat transfer rate. A boiler automatic control device characterized by: