JP4526558B2 - Steam temperature control method and control device for marine boiler - Google Patents

Description

  [Technical Field] The present invention relates to a marine boiler that stably controls both the main steam temperature and the reheat steam temperature in a marine boiler having an internal heat sink that adjusts the main steam temperature and a reheat damper that adjusts the reheat steam temperature. The present invention relates to a steam temperature control method.

  A reheat boiler used for a marine turbine has, for example, a flue connected to a combustion chamber, and the flue is divided into a reheater path (RH path) and a superheater path (SH path). A damper is installed. The reheater path includes a economizer, first, second reheater, and third superheater, and the superheater path includes the economizer, first, second, and fourth superheaters. Be placed. The reheat boiler is further provided with a steam drum with a built-in heat sink, and the steam generated in the steam drum is superheated through the superheater and is supplied with water supplied through a spray valve as necessary. The steam is cooled and divided into steam that is cooled by a slow heat generator and steam that passes through the bypass, and then merged and mixed and supplied to the high-pressure steam turbine as main steam.

The marine boiler generates superheated steam of, for example, 565 ° C. and 12 MPa through steam through the superheater, drives the high-pressure steam turbine as main steam, and passes steam recirculated from the high-pressure steam turbine through the reheater, for example, steam at 545 ° C. and 3 MPa. And drive the medium and low pressure steam turbine. The steam turbine is uniaxially connected and cooperates to drive the propeller.
Two boilers having the same configuration may be installed in parallel.

In the conventional steam temperature control method, the temperature of the main steam is controlled by adjusting the amount of steam guided to the heat sink with a steam flow control valve. In order to secure a differential pressure in the steam flow rate control valve, an orifice plate is provided in the bypass passage.
On the other hand, the reheat steam is recirculated from the high pressure steam turbine and reheated by the reheater installed in the reheater path and supplied to the intermediate / low pressure steam turbine. It controls by adjusting the amount of combustion gas which flows through a reheater path | pass with the provided reheat damper.

Thus, in the conventional steam temperature control method, the main steam temperature is controlled by the internal slow heat supply steam flow control valve, and the reheat steam temperature is controlled by the reheat damper. Since it is linked to 1, the division of roles is clear and easy to understand.
However, if the opening of the reheat damper is increased in order to increase the temperature of the reheat steam, the amount of combustion gas in the superheater path decreases, the main steam temperature decreases, and conversely the temperature of the reheat steam decreases. Therefore, if the opening degree of the reheat damper is reduced, the amount of combustion gas in the superheater path increases and the main steam temperature rises. As described above, the main steam temperature and the reheat steam temperature are in a relationship of interfering with each other, so that control is difficult.

  In Patent Document 1, the boiler of a thermal power plant equipped with an exhaust gas recirculation path controls the opening degree of the exhaust gas recirculation damper based on the deviation from the set value of the reheat steam temperature, and further, the integrated value of the deviation A reheat steam temperature control device for controlling the opening degree of the superheater side gas distribution damper and the reheater side gas distribution damper based on the above is disclosed. Here, the main steam temperature is controlled by pouring water with a superheater spray.

In Patent Document 2, in a marine boiler, instead of replacing the orifice provided in the slow heatr bypass pipe according to the conditions, a superheated steam that can be manually adjusted by using a variable flow rate adjustment device having a needle valve mechanism. A temperature control apparatus is disclosed. However, in the present disclosure, adjustment of the bypass flow rate and the heat sink flow rate is performed manually, and it does not have a function corresponding to unexpected temperature fluctuations.
JP 58-2000907 A Japanese Patent Laid-Open No. 10-089612

  Therefore, the problem to be solved by the present invention is that the flue is divided into a reheater path and a superheater path, and the main steam is supplied to the high-pressure steam turbine by controlling the temperature by the amount of steam and the amount of spray passed through the heat sink. In addition, a steam temperature control method and device are provided that enable more efficient and stable operation of marine boilers that supply reheat steam to the medium and low pressure steam turbines by controlling the temperature according to the reheat damper opening of the reheater path. It is to be.

  In order to solve the above-described problems, the steam temperature control method for a marine boiler according to the present invention is such that the flue is divided into a reheater path and a superheater path, and the main steam passes through the slow heatr and / or the spray amount. This is a steam temperature control method applied to a marine boiler that supplies temperature to the high-pressure steam turbine and supplies it to the high-pressure steam turbine. The reheat steam temperature is controlled by setting a temperature obtained by adding a bias determined based on the difference between the rated temperatures of the main steam and the reheat steam to the measured value of the main steam temperature as a set value. To do.

According to this steam temperature control method, the reheat steam temperature is always controlled with an optimal correlation with the main steam temperature, so static characteristics are maintained when the fuel is changed or the number of burners is changed. Even if it changes, stable operation is possible.
Since boiler specifications and heat exchanger specifications are determined according to the rated temperature, for example, if temperature control is performed using a value that is lower than the measured value of the main steam temperature by the difference between both rated temperatures, In addition, the thermal stress of each part of the boiler is within the allowable range, and safe operation is possible.

  The optimum bias for determining the reheat steam temperature setting value differs depending on the boiler load. For example, when the main steam temperature is different from 565 ° C., 500 ° C., 450 ° C., and 400 ° C., the optimum bias is −20 ° C., respectively. , -25 ° C, -30 ° C, and -35 ° C. In on-shore boilers, there are cases where the reheat steam temperature is higher than the main steam temperature. In order to cope with such a change, a variable bias device can be provided.

In the main steam temperature control, in a region where the boiler load corresponds to the rated temperature of the main steam or less, the rated temperature is set as the upper limit, and a temperature obtained by adding a predetermined positive bias to the measured value of the main steam temperature is set as a set value. It is preferable. In this way, it is possible to perform a control that keeps the steam temperature as close to the rated temperature as possible and minimizes the temperature reduction (slow heat) means.
In the region where the boiler load corresponds to the rated temperature of the main steam, the temperature control of the main steam is performed using the rated temperature as a set value.

  In the region below the rated temperature, the relationship between the boiler load and the main steam temperature is determined according to the static characteristics. In the present invention, the main steam temperature setting value is always set above the load-steam temperature correlation line by setting a value obtained by adding a bias to the actual measurement value of the main steam temperature. At all times, the maximum value corresponding to the boiler load is maintained, and the highest thermal efficiency is maintained.

The main steam temperature can be controlled by passing a part of the main steam through a slow heat generator. Moreover, when the main steam temperature rises rapidly, a spray cooler for spraying water to the main steam to reduce the temperature can be provided, and spray water can be injected and controlled.
In addition, a desuperheater is placed between the superheaters, and is controlled by the amount of steam that passes through the slow-heater in normal cases. When the temperature exceeds the main steam set value plus a specified bias, the spray desuperheater is installed. It can also be used to reduce the temperature of the main steam.
In order to reliably control the flow rate of the steam that passes through the heat sink, the steam flow rate control valve that supplies the steam to the heat sink and the bypass flow rate control valve that is provided in the bypass flow path that bypasses the heat sink are in opposite directions. It can be configured to operate.

  When the main steam temperature suddenly rises, such as when switching between reheat mode and non-reheat mode, or during a crash astern, temperature control using a slow-heater is insufficient to respond sufficiently There is. Therefore, it is preferable to deal with the spray with good responsiveness. It is also possible to use a method in which when a factor that causes the main steam temperature to fluctuate rapidly is detected, this is regarded as a preceding signal and canceled in advance using a spray.

In addition, in the ship provided with two marine boilers, it is necessary to maintain balance about two boilers. For this reason, it is preferable that the set value of the reheat steam temperature is generated on the basis of the lower main steam temperature of the two marine boilers and provided in common to the two marine boilers. Similarly, for the main steam temperature, the set value is preferably generated on the basis of the lower main steam temperature of the two marine boilers and provided in common to the two marine boilers.
According to this method, the temperature reduction amount is minimized without causing a large temperature difference between the two steam temperatures, so that the overall efficiency is improved.

  Moreover, in order to solve the said subject, the steam temperature control apparatus of the marine boiler of this invention is a 1st common circuit which provides the temperature setting value of the reheat steam temperature control apparatus of two marine boilers, A comparator that selects and outputs the lower main steam temperature in the main boiler, a function generator that can set the difference between the rated temperatures of the main steam and reheat steam, and the output of the comparator and the function generator An adder for adding outputs is provided, and a common circuit is provided for providing the output of the adder as a temperature set value to a setter of a reheat steam temperature controller of two marine boilers.

  The first common circuit further includes an upper limiter for limiting the upper limit value for the temperature set value obtained from the adder, and a change rate limiter for limiting the change rate for the previously set temperature set value. The set value may be corrected to limit the upper limit value and the rate of change and provided as the temperature set value of the reheat steam temperature control device for the two marine boilers.

Further, a second comparator that selects and outputs the lower one of the main steam temperatures in the two boilers, a second function generator that can set a predetermined positive bias, and an output of the second comparator And a second adder for adding the outputs of the second function generator, and providing the output of the second adder as a temperature set value to the setter of the main steam temperature controller of the two marine boilers. The common circuit may be provided.
In addition, it has a differential circuit that calculates fluctuations in the exhaust gas amount from changes in the combustion intake air amount of the boiler, and a subtractor that subtracts the differential circuit output signal from the superheat damper opening control signal and outputs it. The overheat damper opening degree control signal may be adjusted using the value to adjust the opening degree of the overheat damper.

Further, an arithmetic device for calculating the combustion gas flow rate distribution ratio on the superheater path side by inputting an opening measurement value of the reheat damper, a multiplier for calculating a multiplication value of the arithmetic device output signal and the combustion air flow rate measurement value, , Which is composed of a differentiator and an adder, is equipped with a fluctuation estimator that predicts fluctuations in the main steam temperature from the multiplier output, and adjusts the opening control signal of the main steam flow control valve using the predicted fluctuation in the main steam temperature Then, the differential circuit calculates the fluctuation of the exhaust gas amount from the change of the combustion air amount, and the subtractor adjusts the steam flow control valve control signal with the opening adjustment signal to adjust the opening of the steam flow control valve. It may be.
A function generator for generating a bias temperature and an adder for adding the main steam temperature set value and the bias temperature are provided, and an override value that is higher than the main steam temperature set value by a predetermined temperature is used as a boiler for the SH spray temperature set value. It can be input to a comparator of the main steam temperature controller at the outlet.

By generating a negative deviation in the comparator of the controller, the SH spray control valve is normally closed normally, and when the main steam temperature exceeds the steam temperature set value and when the main steam temperature is SH When the spray set temperature is exceeded, the SH spray control valve is opened and water is supplied to quench the steam temperature.
When the boiler load decreases and the main steam temperature set value drops, such as during an astern, the SH spray temperature set value slides to the main steam temperature set value that also drops, and the SH spray temperature is increased to a temperature that is added to the specified temperature. It is preferable to set the temperature set value.

Hereinafter, a steam temperature control method for a marine boiler according to an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a steam flow diagram around a marine boiler in the present embodiment, FIG. 2 is a block diagram of a reheat steam temperature control method for a marine boiler according to the present embodiment, and FIG. 3 is a diagram for explaining a set temperature of reheat steam temperature control. 4 is a block diagram of a main steam temperature control method for a marine boiler of the present embodiment, FIG. 5 is a diagram for explaining a set temperature of main steam temperature control, and FIG. 6 is a block diagram of a main steam spray control method, FIG. 7 is a diagram explaining the set temperature of the spray control temperature control, FIG. 8 is a flowchart showing a procedure for switching from the non-reheat mode to the reheat mode, and FIG. 9 is a flowchart showing a procedure for switching from the reheat mode to the non-reheat mode. It is.

In this embodiment, the steam temperature control method of the present invention is applied to the marine boiler shown in FIG.
A marine boiler 1 to be applied in the present embodiment has a flue 13 divided into a reheater path (RH path) 14 and a superheater path (SH path) 15 in a combustion chamber 11 in which a burner 12 is installed downward. Is a reheat boiler installed.
The combustion chamber 11 is provided with a steam drum 16 at the top and a water drum 17 at the bottom, and is connected by an evaporation pipe (not shown) provided on the wall. Further, a slow heat generator 18 is incorporated in the evaporation drum 16 or the water drum 17.

  A economizer 21, a first reheater 22, a second reheater 23, and a third superheater 24 are disposed in the reheater path 14 of the flue 13, and a reheat damper 25 and an RH protection damper 26 are arranged downstream. Further, a seal air damper 28 is provided in an air pipe 27 connected between the reheat damper 25 and the RH protection damper 26. Further, in the superheater path 15, a economizer 31, a first superheater 32, a second superheater 33, and a fourth superheater 34 are arranged, and an SH damper 35 is provided downstream.

  The steam generated in the steam drum 16 is superheated by the first and second superheaters 32 and 33 of the superheater path 15, and then the temperature is reduced by the spray cooler 36 as necessary, so that the reheater path. 14 is heated by the third superheater 24, a part is passed through the slow heatr 18, the rest is passed through the bypass flow path 37, the temperature is adjusted by merging, and the temperature is further passed through the fourth superheater 34. The steam having the pressure is supplied to the high-pressure steam turbine 2 to drive the turbine.

The steam after working in the high-pressure steam turbine 2 is led to the first and second reheaters 22 and 23 of the reheater path 14 and reheated, and then supplied to the intermediate and low pressure steam turbine 3 to drive the turbine. Condensate with a condenser outside the figure, and supply to the boiler again via the feed water pump and feed water heater for use as main steam.
The high-pressure steam turbine 2 and the medium-low pressure steam turbine 3 share one shaft, and the rotating shaft is coupled to the propeller gear box to drive the screw.

  When the load is equal to or higher than a predetermined value, this boiler is operated in a reheat mode (RH mode) using the reheaters 22 and 23 through the combustion gas through the reheater path 14, but the ship speed decreases. When the boiler load becomes small, the operation is performed in the non-reheat mode (NRH mode) in which the reheater path 14 is not used.

In the reheat mode, the SH damper 35 and the RH protection damper 26 are fully opened, the seal air damper 28 is fully closed, and the reheat damper 25 has an opening adjusted by an operation signal.
In the non-reheat mode, the SH damper 35 is fully opened, the reheat damper 25 and the RH protection damper 26 are fully closed, and the seal air damper 28 is fully opened to perform air sealing at the upstream end of the reheater path 14 and reheat. The vessel path 14 is closed and the flow of combustion gas is shut off.

  The steam temperature control system in the present embodiment includes a reheat steam temperature control system, a main steam temperature control system, an SH spray control system, and a mode switching system.

(Reheat steam temperature control system)
The reheat steam temperature control system basically detects the temperature of the reheat steam supplied to the intermediate / low pressure steam turbine 3 with the temperature detector 51 and detects the temperature of the main steam supplied to the high pressure steam turbine 2 with the temperature detector. 61, the reheat damper driver 53 is driven by the temperature controller 52 to adjust the opening of the reheat damper 25, and the deviation from the reheat steam temperature set value derived from the main steam temperature is eliminated. Is to control.

  The reheat damper 25 adjusts the distribution of the combustion gas flowing through the reheater path 14 and the superheater path 15, and the reheat steam temperature and the main steam temperature have a contradictory relationship with respect to the operation of the reheat damper 25. That is, when the reheat damper 25 is increased in opening degree to increase the reheat steam temperature, the amount of combustion gas passing through the superheater path 15 decreases, so that the main steam temperature decreases. Conversely, if the reheat damper 25 is operated to lower the reheat steam temperature, the main steam temperature rises.

In this embodiment, the rated temperature of the main steam is 565 ° C., and the rated temperature of the reheat steam is 545 ° C., which is 20 ° C. lower than this. In addition, due to the static characteristics of this boiler, the main steam temperature cannot be maintained at the rated temperature of 565 ° C. in the boiler load zone that is equal to or less than the predetermined ratio of the maximum load, and the steam flow rate control valve 63 leading to the heat sink 18 is fully closed. Thus, the main steam temperature shows a temperature according to the static characteristics. Even in this case, it is desired that the reheat steam temperature is about 20 ° C. lower than the main steam temperature.
Therefore, the reheat steam temperature is basically controlled so that the difference between the main steam and the reheat steam temperature is always controlled to be about 20 ° C. lower than the main steam temperature.

In addition, when two marine boilers are provided in one ship, it is not preferable that a big temperature difference arises in the reheat steam temperature and main steam temperature of two cans.
To avoid differences in steam temperature, the load on the two cans is operated as evenly as possible, but the main steam temperature is set to the lower value, but the reheat steam temperature is A reheat steam temperature setting value common to the two cans is generated on the basis of the lower main steam temperature of the two cans so that a large deviation does not occur.
For this reason, it is preferable to provide a common circuit for giving the same set value to the reheat steam temperature controllers 52 of the first boiler and the second boiler so as to balance the boiler operation.

  Further, when the combustion air flow rate is changed together with the fuel due to load fluctuation or the like, the reheat steam temperature is affected and temporarily fluctuates. Therefore, when the air flow rate is measured and there is a change in the air flow rate, if the reheat damper 25 is operated in a direction to suppress the change in the exhaust gas flow rate flowing through the reheater path 14, the reheat steam temperature The change will be suppressed and stable.

FIG. 2 is a block diagram illustrating details of the reheat steam temperature control system.
When two marine boilers are provided in one ship, a common circuit 110 that gives the same set value to the reheat steam temperature controllers of the first boiler and the second boiler is provided to balance the boiler load. .

The common circuit 110 inputs a main steam temperature at the outlet of the first boiler and an outlet main steam temperature of the second boiler and selects a lower temperature, a reheat steam temperature setting deviation in the reheat mode. The first function generator 112 for generating the second function generator 113 for generating a large setting deviation such as -200 ° C. in order to make the reheat steam temperature sufficiently low in the non-reheat mode, and the output of the comparator 111 A first adder 114 that takes the sum of the outputs of the one function generator 112, a second adder 115 that takes the sum of the outputs of the comparator 111 and the second function generator 113, and the first adder 114 in the reheat mode. In the non-reheat mode, a selector 116 that selects and outputs the output of the second adder 115, and a limiter 117 that restricts the output of the selector 116 with an upper and lower limit value so as not to exceed the appropriate range of the apparatus. And more Consists of a change rate limiter 118 which constrains so as not to exceed the maximum rate of change output of the selector 116 is observed in the apparatus.
The output of the common circuit 110 is input to the setting device 121 of the reheat steam temperature controller 52. When two marine boilers are provided in a ship, the same set value is given to each reheat steam temperature controller.

The reheat steam temperature controller 52 includes a comparator 122 at an input unit, inputs a temperature signal from the temperature detector 51, and passes a deviation signal from the output signal of the setting device 121 to the controller 123. The controller 123 performs a proportional integration operation (PI) on the deviation to generate an appropriate operation output signal.
A differential circuit 124 and a subtractor 125 for detecting a change in the air amount by inputting a measured value of the combustion air amount and predicting a change in the reheat steam temperature in advance are provided. A value obtained by subtracting the influence amount is supplied to the reheat damper control drive 53 via the input switch 126 and the automatic manual switch 127, and the reheat damper 25 is driven.

  If the opening degree of the reheat damper 25 increases, the amount of combustion gas flowing through the reheater path 14 increases and the amount of heat received by the reheat steam increases, so that the reheat steam temperature rises. Moreover, if the opening degree of the reheat damper 25 becomes small, the reheat steam temperature falls. Therefore, the reheat steam temperature can be controlled to maintain a constant correlation with the main steam temperature measurement value by adjusting the opening degree of the reheat damper 25 in the reheat steam temperature control system.

  In addition to the signal from the controller 52, the input switch 126 includes a fully closed command signal for forcibly closing the reheat damper 25, an unburned gas at the time of boiler trip or furnace purge, etc. A full-open command signal for fully opening the reheat damper 25 to prevent stagnation, and an opening command signal at a ratio that gives an appropriate initial heat amount when switching the reheat mode can be selected and output.

FIG. 3 is a diagram showing the relationship between the set value and the steam temperature in the reheat steam temperature control system.
The common circuit 110 selects the lower measured value of the main steam temperature of the two cans, and sets the value obtained by subtracting 20 ° C. as the set value of the reheat steam temperature at the time of transition.
In a region lower than the rated output of a predetermined ratio or less with respect to the maximum load, the main steam temperature decreases as the load decreases according to the static characteristics of the boiler as shown by a solid line in the figure. Further, in a load range of a predetermined ratio or more with respect to the maximum load capable of rated operation, the main steam temperature is stabilized at the rated value of 565 ° C., and the reheat steam temperature set value is predetermined with respect to the main steam rated temperature. Stabilize the reheat steam rated temperature 545 ° C. lower by bias. Note that the reheat steam temperature set value is limited by the limiter 117 to 545 ° C. + α which does not greatly exceed the RH rated value of 545 ° C.

The common circuit 110 uses the lower main steam temperature of the first and second boilers, that is, the main steam temperature of the boiler with the smaller load as a reference, and in the reheat mode, for example, the reference main steam temperature is higher than the reference main steam temperature. A target value lower by 20 ° C. is generated and supplied as a set value for the reheat steam temperature controller 52. If the bias temperature to be adopted is the same value as the difference between the rated temperature of the main steam and the rated temperature of the reheat steam, it is preferable because changes in thermal stresses in the boiler and heat exchanger as well as the turbine are reduced.
Further, since the reheater path 14 is closed in the non-reheat mode, the reheat steam temperature set value is gradually decreased through the rate of change controller 118 at the time of transient by setting the reheater path 14 at a low temperature of 200 ° C., for example. The heat damper 25 is fully closed.

  According to the present embodiment, the reheat steam temperature set value is determined based on the measured value of the main steam temperature, so that the static characteristics are different for various fuel modes of liquid fuel, gas, and co-firing, and the boiler heat transfer surface The static characteristics change even when the surface is soiled, etc., but even if such a deviation of the static characteristics occurs, it is possible to keep the SH and RH heat distribution optimally without changing the setting of the function calculator or the like. In addition, it operates to keep the steam temperature as high as possible even in the middle and low load zones where the steam temperature decreases, and further operates to minimize the total temperature reduction of the two boilers, maximizing the boiler efficiency. There is an advantage that can be operated.

(Main steam temperature control system)
The main steam temperature control system basically performs temperature control mainly by adjusting the flow rate of steam flowing through the internal heat sink, and the steam flow rate for adjusting the amount of steam cooled by the heat sink 18 by the temperature controller 62. The opening degree of the control valve 63 is adjusted, and the main steam temperature detected by the temperature detector 61 is controlled so as to match a predetermined target temperature.

Conventionally, by providing a fixed orifice in the bypass passage 37, a differential pressure is generated between the inlet and the outlet of the steam flow control valve 63, and this is used as a propulsion force for the steam flowing through the slow heat generator. However, since the RH boiler is required to be able to control a larger flow rate range, the conventional method is insufficient.
Therefore, in this embodiment, a sufficient differential pressure is ensured between the inlet and the outlet of the steam flow control valve 63 by providing the bypass flow control valve 64 instead of the fixed orifice.
The temperature controller 62 operates the steam flow rate adjusting valve 63 effectively by simultaneously driving the bypass flow rate adjusting valve 64 provided in the bypass passage 37 in the opposite direction to the steam flow rate adjusting valve 63.

  However, when the reheat steam temperature is controlled by the reheat damper 25, the amount of combustion gas flowing through the superheater path 15 fluctuates. Variations caused by reheat steam temperature control must also be absorbed.

FIG. 4 is a block diagram illustrating details of the main steam temperature control system.
In preparation for the case where two marine boilers are provided, a common circuit 130 that provides the same set value to the main steam temperature controllers of the first boiler and the second boiler is provided.
The common circuit 130 receives a main steam temperature of the first boiler and a main steam temperature of the second boiler and selects a lower temperature, for example, a first function generator that generates a moderate bias such as 10 ° C. 132, a first adder 133 that adds the measured main steam temperature output from the comparator 131 and the bias temperature output from the first function generator 132, in this case, a second main steam temperature that generates a rated main steam temperature of 565 ° C. Function generator 134, third function generator 135 for generating 550 ° C., second function generator 134, selector 136 for outputting one of the third function generators 135, and output of adder 133 for the output of selector 136 A limiter 137 that restricts the upper limit by output, and a rate-of-change limiter 138 that restricts the change rate of the set temperature and prevents an extreme change in steam temperature.

The output of the common circuit 130 is input to the setting device 141 of the main steam temperature controller 62. When two marine boilers are provided, the same output is supplied to the setting device of the main steam temperature controller of the second boiler.
The main steam temperature controller 62 includes a comparator 142 at the input unit, inputs the main steam temperature signal from the temperature detector 61, and passes a deviation signal from the output signal of the setting device 141 to the controller 143. The controller 143 performs a proportional integration operation (PI) on the deviation to generate an appropriate operation output signal.

  In addition, the operation output signal includes a prior operation in order to predict and suppress the main steam temperature fluctuation caused by the combustion gas fluctuation. It is not sufficient to use the combustion air flow rate in the combustion chamber 11 as a substitute variable of the combustion gas flow rate in the superheater path, and the value obtained by multiplying the measured value of the combustion air flow rate by the combustion gas flow rate distribution in the superheater path. Use as a function.

  For this reason, an arithmetic unit 144 for calculating the distribution ratio estimated value of the combustion gas flow rate by inputting the opening degree of the reheat damper 25, and a multiplier 145 for multiplying the output of the arithmetic unit and the measured value of the combustion air flow rate. , A differential circuit 146 that inputs the output of the multiplier 145 and predicts the fluctuation of the main steam temperature in advance, and a second adder 147, the operation output of the controller 143 and the main output from the second adder 147. A third adder 148 that corrects by adding the steam temperature fluctuation predicted value and supplies the corrected operation signal to the steam flow rate adjustment valve 63 via the input switch 149 and the automatic manual switch 150. The output of the automatic manual switching device 150 is reverse-phase converted by the signal converter 151 and supplied to the bypass flow rate adjustment valve 64, and is generated in the bypass passage 37 so that the amount of steam flowing through the slow heat generator 18 can be adjusted widely. Adjust the differential pressure.

In addition to the signal from the third adder 148, the input switch 149 receives a full-close command signal for forcibly and fully closing the steam flow rate control valve 63, and can select and output it. .
Further, since the steam flow rate adjusting valve 63 and the bypass flow rate adjusting valve 6 need to be operated in reverse phase even when manually adjusting by separating from the controller, the signal converter 151 has a mechanism for mechanically performing reverse phase conversion. It is preferable to have it.

FIG. 5 is a drawing showing the relationship between the set value and the steam temperature in the main steam temperature control system.
When the load is low, the lower one of the measured values of the main steam temperature of the two cans is selected by the common circuit 130, and a value with a bias of 10 ° C. plus, for example, is used as the reference value for the main steam temperature at the time of transition. To do. In order to maintain the main steam temperature at the rated temperature in a high load state, it is necessary to reduce the temperature by passing a part of the steam through a slow heat generator.

  As a result, even if there is a change in static characteristics due to fuel mode switching, change in the number of burners, dirt in the furnace, etc., it is possible in the middle and low load range where the steam temperature does not reach the rated temperature and below the predetermined ratio of the maximum load As long as the main steam temperature is kept as high as possible, efficiency is maintained. In addition, the steam flow rate control valve is statically kept in a fully closed state in the low load region except when the steam temperature increases rapidly.

(SH spray control system)
The SH spray control system is used urgently when, for example, the main steam temperature rises sharply and the heat sink does not sufficiently absorb heat. When the main steam temperature detected by the temperature detector 61 rises abnormally, the spray regulator valve 72 is opened by the temperature controller 71 and water is sprayed into the steam by the spray cooler 36 to rapidly reduce the temperature. To deal with. The SH spray control system is superior in responsiveness as compared with temperature reduction by a heat sink.

  While the main steam temperature control, which controls the steam temperature by adjusting the flow rate of steam flowing through the heat sink, is inherently slow, the reheat gas flow rate that fluctuates due to the reheat damper operation in the reheat steam temperature control remains unchanged. Since it appears as a disturbance to the main steam temperature control, the main steam temperature is greatly affected. Further, during the crash astern, since the mode is switched to the non-reheat mode, the reheat damper is fully closed and the entire amount of the combustion gas flows into the superheater path, causing a sudden rise in the main steam temperature. An SH spray control system is prepared in preparation for such a rapid temperature rise.

FIG. 6 is a block diagram illustrating details of the SH spray control system.
Since the SH spray control system is used in an emergency, even when two marine boilers are provided, the first boiler and the second boiler are provided independently.
In the SH spray control system, a function generator 161 that generates an appropriate temperature difference given to a set value to keep the spray valve closed at all times, a boiler outlet main steam temperature set value and a temperature difference generated by the function generator 161 The first adder 162 and the change rate limiter 163 for adjusting the set value signal output from the first adder 162 so as not to exceed a predetermined change rate and the output of the change rate limiter 163 are input. A setting unit 164 for generating a set value for the controller, a comparator 165 for calculating the deviation between the boiler outlet main steam temperature measured by the temperature detector 61 and the set value, and a proportional integral operation (PI) ) To generate an appropriate operation signal, and a signal indicating that the reheat mode is converted to the non-reheat mode is input to generate a signal for driving the SH spray control valve 72. The second adder 168 adds the operation signal of the multiplier 167 and the SH spray controller 166 and the drive signal from the multiplier 167, and outputs either the operation signal output from the second adder 168 or the fully closed command signal. The input switch 169, the automatic manual switch 170, and the SH spray control valve 72 driven by the output of the automatic manual switch 170 are configured.

FIG. 7 is a diagram showing the relationship between the set value and the steam temperature in the SH spray control system.
The SH spray temperature set value is set to an override set value that is higher by Δt ° C. than the main steam temperature set value, and a slight negative deviation is generated in the comparator 165, so that the SH spray control valve 72 is fully closed at normal times. It is trying to become.
When the main steam temperature exceeds the steam temperature set value or when it rises rapidly and exceeds the SH spray set temperature, the steam temperature is rapidly cooled by opening the SH spray control valve 72 and supplying water. can do.

When the boiler load decreases and the main steam temperature set value drops, such as during an astern, the SH spray temperature set value slides to the main steam temperature set value that also drops, and the temperature of the SH spray temperature is added to this by adding Δt ° C. Set the setting value.
Before the steam temperature actually increases, an excessive temperature increase is prevented by blowing the SH spray in advance.

When the main steam temperature is not sufficiently increased, such as when the boiler is started, the SH spray control valve 72 is forcibly closed via the input switch 169 so as not to obstruct the temperature increase.
In addition, when there is an emergency switch from the reheat mode to the non-reheat mode, the heat recovery on the superheater path side increases rapidly, and thus the main steam temperature may temporarily rise excessively. In preparation for such a rapid rise in steam temperature, an excessive temperature rise can be suppressed by blowing SH spray in advance.

(Mode switching system)
The mode switching system operates the dampers 25, 26, and 28 of the reheater path 14 and the damper 35 of the superheater path 15 in accordance with a predetermined sequence, so that high output such as rated operation is required and the reheater path 14 is utilized. Switching between a reheat mode that operates at a high load and a non-reheat mode that operates by closing the reheater path when it is sufficient to perform a medium to low power operation such as when operating in a port.

FIG. 8 is a flowchart showing a procedure for switching from the non-reheat mode to the reheat mode.
When a command to switch from the non-reheat mode to the reheat mode is received, a command to close the seal air damper 28 is generated (S1). Subsequently, a command to release the RH protection damper 26 is generated (S2), the reheater path 14 is opened, and automatic control (CAS mode) of the reheat damper 25 is started (S3).

  Next, the set value is changed from the temperature drop state set value in the non-reheat mode to the normal reheat steam temperature set value in the reheat mode, and the temperature raising condition is set (S4). Further, an initial opening degree command for the reheat damper 25 is generated (S5). Thereafter, the process waits until the reheat steam temperature reaches a predetermined initial temperature (S6).

  When the reheat steam temperature reaches a predetermined temperature, automatic control of the reheat steam temperature is started using the reheat damper 25 (S7). The reheat steam temperature set value is set to be approximately −20 ° C. lower than the main steam temperature measurement value, and the temperature rises as the main steam temperature rises according to the setting of the main steam temperature measurement value + α. Therefore, it is waiting (S8). Then, the reheat steam set temperature eventually reaches the target value, the reheat steam temperature also reaches the target value (S9), and the switching from the non-reheat mode to the reheat mode is completed.

FIG. 9 is a flowchart showing a procedure for switching from the reheat mode to the non-reheat mode.
When a command to switch from the reheat mode to the non-reheat mode is received, when the control mode of the reheat damper 25 is not the CAS mode, the CAS mode is switched to the CAS mode (S11), and the CAS set value created by the common circuit 110 is normally set. The set value is switched to the target temperature decrease value, and the rate of temperature decrease is defined by the change rate limiter 118 (S12). As the reheat steam temperature setting value decreases, the reheat damper 25 narrows the opening degree, and thus waits until the reheat steam temperature sufficiently decreases (S13).

When the reheat damper 25 is nearly fully closed, the fully closed command is held by a command from the sequencer to hold the fully closed state (S14). Next, a command for fully closing the RH protection damper 26 is generated (S15), and a command for opening the seal air damper 28 is generated (S16).
When the flue of the reheater path 14 is closed by the RH protection damper 26 and the space between the reheat damper 25 and the reheat damper 25 is sealed with sealing air, the switching from the reheat mode to the non-reheat mode is completed.
Needless to say, the common circuit, the control circuit, the sequence circuit, and the like may be configured by an electronic computer.

It is a steam flow figure around a marine boiler in one example of the present invention. It is a block diagram of the reheat steam temperature control method of a present Example. It is a diagram explaining the preset temperature of the reheat steam temperature control of a present Example. It is a block diagram of the main steam temperature control method of a present Example. It is a diagram explaining the preset temperature of the heating steam temperature control of a present Example. It is a block diagram of the spray control method of the main steam in a present Example. It is a diagram explaining the preset temperature of spray control temperature control of a present Example. It is a flowchart showing the procedure which switches from the non-reheat mode of a present Example to the reheat mode. It is a flowchart showing the procedure switched from the reheat mode of a present Example to the non-reheat mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Marine boiler 2 High pressure steam turbine 3 Medium and low pressure steam turbine 11 Combustion chamber 12 Burner 13 Flue 14 Reheater path (RH path)
15 Superheater path (SH path)
16 Steam Drum 17 Water Drum 18 Slow Heater 21 Cargo Saver 22 First Reheater 23 Second Reheater 24 Third Superheater 25 Reheat Damper 26 RH Protection Damper 27 Air Pipe 28 Seal Air Damper 31 Cargo Saver 32 1st superheater 33 2nd superheater 34 4th superheater 35 SH damper 36 spray desuperheater 37 bypass flow path 51 temperature detector 52 temperature controller 53 reheat damper driver 61 temperature detector 62 temperature controller 63 Steam flow control valve 64 Bypass flow control valve 71 Temperature controller 72 Spray control valve 110 Common circuit 111 Comparator 112 First function generator 113 Second function generator 114 First adder 115 Second adder 116 Selector 117 Limiter 118 Change Rate Limiter 121 Setter 122 Comparator 123 Controller 124 Differentiation Circuit 125 Subtractor 1 26 Input switch 127 Automatic manual switch 130 Common circuit 131 Comparator 132 First function generator 133 First adder 134 Second function generator 135 Third function generator 136 Selector 137 Limiter 138 Change rate limiter 141 Setting Unit 142 Comparator 143 Controller 144 Arithmetic unit 145 Multiplier 146 Differentiation circuit 147 Second adder 148 Third adder 149 Input switch 150 Automatic manual switch 151 Signal converter 161 Function generator 162 First adder 163 Change Rate limiter 164 Setter 165 Comparator 166 SH spray controller 167 Multiplier 168 Second adder 169 Input switch 170 Automatic manual switch

Claims (7)

The flue is divided into a reheater path and a superheater path, and the main steam is supplied to the high-pressure steam turbine with the temperature controlled by the amount of steam and / or spray that passes through the slow heatr, and the reheated steam is reheater A steam temperature control method for a marine boiler that supplies temperature to a medium / low pressure steam turbine by controlling the temperature by the reheat damper opening of the path,
In the region where the boiler load corresponds to the rated temperature of the main steam, the temperature of the main steam is controlled with the rated temperature as the set value,
In the region where the boiler load corresponds to less than the rated temperature of the main steam, the temperature of the main steam is controlled using the temperature obtained by adding a predetermined bias to the measured value of the main steam temperature with the rated temperature as the upper limit,
A steam temperature control method for a marine boiler, characterized in that the reheat steam temperature is controlled by setting a temperature determined by adding a bias determined based on a difference between the rated temperatures of the main steam and the reheat steam to an actual measurement value of the main steam temperature. . A steam flow rate adjusting valve installed in a flow path that leads from the outlet of the third superheater provided in the reheater path to the inlet of the fourth superheater provided in the superheater path through the slow heater; In a bypass flow rate control valve installed in a bypass flow path that directly connects the 3 superheater outlet and the fourth superheater inlet and bypasses the slow heatr, the steam flow rate control valve and the bypass flow rate control valve are reversed. marine boiler steam temperature control method according to claim 1, wherein for controlling the main steam temperature by operating. Two marine boilers are provided, and the set value of the reheat steam temperature is generated on the basis of the lower main steam temperature of the two marine boilers, and is provided in common to the two marine boilers. The marine boiler steam temperature control method according to claim 1 or 2 . The flue is divided into a reheater path and a superheater path, and the main steam is supplied to the high-pressure steam turbine with the temperature controlled by the amount of steam and / or spray that passes through the slow heatr, and the reheated steam is reheater A marine boiler steam temperature control device for use in a ship equipped with two marine boilers for controlling the temperature according to the opening of a reheat damper of a path and supplying the medium / low pressure steam turbine ,
Comparator and main steam output and said function generator and said comparator capable of setting the difference between the nominal temperature of the reheated steam for selecting and outputting the lower of the main steam temperature in the boiler before Symbol 2 group A first common circuit comprising an adder for adding the output of the function generator, and providing the output of the adder as a temperature set value to a setter of the reheat steam temperature controller of the two marine boilers ;
A second comparator that selects and outputs the lower main steam temperature in the two boilers, a second function generator that can set a predetermined positive bias, and an output of the second comparator And a second adder for adding the output of the second function generator, and providing the output of the second adder as a temperature set value to the setter of the main steam temperature controller of the two marine boilers A steam temperature control device for a marine boiler, comprising a second common circuit that performs The first common circuit further includes an upper limiter for limiting an upper limit value for the temperature set value obtained from the adder, and a change rate limiter for limiting the change rate for the previously set temperature set value. And
5. The marine boiler according to claim 4, wherein the calculated set value is provided as a temperature set value of the reheat steam temperature control device for the two marine boilers by correcting the upper limit value and the rate of change. Steam temperature control device. An arithmetic device for calculating the combustion gas flow rate distribution ratio on the superheater path side by inputting an opening measurement value of the reheat damper, a multiplier for calculating a multiplication value of the output signal of the arithmetic device and the combustion air flow rate measurement value, A fluctuation estimator that is configured by a differentiator and an adder and predicts a fluctuation of the main steam temperature from an output of the multiplier, and an opening degree control signal of the main steam flow control valve using the fluctuation prediction value of the main steam temperature The differential circuit calculates the fluctuation of the exhaust gas amount from the change of the combustion air amount, the subtractor adjusts the control signal of the main steam flow rate control valve with the opening adjustment signal, and the main steam flow rate control valve The steam temperature control device for a marine boiler according to claim 4 or 5 , wherein the opening degree is adjusted. A function generator for generating a bias temperature, and an adder for adding the main steam temperature set value and the bias temperature, and using an override value higher than the main steam temperature set value by a predetermined temperature as the SH spray temperature set value The steam temperature control device for a marine boiler according to any one of claims 4 to 6 , wherein the steam temperature control device is input to a comparator of a main steam temperature controller at an outlet.

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