JPS5921902A - Controller for temperature of steam from boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a multi-stage desuperheater in a steam superheating system, a mixed combustion boiler that uses different types of fuel, a gas recirculation type boiler, Alternatively, the present invention relates to a steam temperature control device for a boiler that generates steam and superheats it using different types of heat transfer sources, such as an auxiliary combustion boiler for a Gannou steam combined cycle power plant.

[Technical background of the invention and its problems]

In order to control the temperature of steam generated in a boiler, a method is generally used in which a desuperheater is provided before a steam superheater, and water is sprayed there to adjust the steam temperature. Steam superheating processes are usually constructed by connecting several types of superheaters with different heat transfer characteristics in series. Therefore, in order to improve the control performance of the boiler outlet steam temperature, a multi-stage spray system with two or more stages in which a plurality of attemperators are provided between superheater groups is sometimes adopted.

In such a process, the steam temperature distribution inside the boiler increases almost uniformly from the inlet to the outlet.
Further, in each steady state, each is necessary so that an operating margin is secured in case of occurrence of disturbance.

As one solution, a method is sometimes used in which the amount of spray in the attemperator at the front stage is controlled so that the amount of spray at the attemperator at the rear stage is at a constant ratio with the flow rate of water or steam.

FIG. 1 is a conceptual diagram of a multi-stage spray type steam superheating process and its control mechanism, which is controlled by this conventional apparatus.

In FIG. 1, 1 is an evaporator, 2 is a pre-superheater, 3 is a pre-superheater, 4 is an intermediate superheater, 5 is a post-desuperheater, 6 is a final superheater, and 7 is a pre-stage superheater. 1 valve 1.8 is the rear stage Sugre valve,
, 10 is the main steam temperature control element, 109 is its output, 11
is a second stage desuperheater outlet steam temperature control element, 107 is its output, 12 is a division element, 13 is a sp/sp, and ratio control element,
105 is the output of the filter, 15 is the steam temperature control element at the outlet of the attemperator, 103 is its output, 100 is the water supply, 101 is the detected water supply flow rate, and 102 is the spray water that is regulated by the pre-stage spray valve 7. , 104 is the detected steam temperature at the outlet of the preheater, 106 is the spray water adjusted by the post-spray valve 8, or the flow rate of the detected 1 ton of spray water 106, and y is the main steam flow rate 112, which is the feed water flow [:101 , x/y is the output of the division element 12, 108 is the detected value of steam temperature at the outlet of the second stage desuperheater, 111 is the main steam temperature target value, 110 is the main steam temperature detection 11, and 113 is the main steam.

Is the water supply to the boiler 100 mainly for fuel? , evaporates into steam in the evaporator 1 (including the drum in the case of a drum-type boiler) due to radiation heat transfer due to sintering.

This steam is superheated in the pre-stage superheater 2, and then heated in the pre-stage desuperheater 3.
The temperature is lowered by spraying spray water 102 regulated by the front-stage spray valve 7.

First-stage desuperheater 3f: Superheat the emitted steam in the intermediate superheater 4, and then spray the spray water 106 adjusted by the second-stage spray valve 8 in the second-stage desuperheater 5 to raise the temperature again.

Then, it is heated to a predetermined temperature 1 in a final superheater 6 and sent out from the boiler as main steam.

The control mechanism of this conventional device ME1, on the one hand, controls the output 109 of the main steam temperature control element 10 based on the deviation between the main steam temperature target value 111 and the main steam temperature target value 110, and further controls the output 109 and the downstream desuperheater. The output 107 of the I throat attemperator outlet steam temperature control element 11 is determined by the deviation of the detected outlet steam temperature value 108.
Fully control and adjust the rear spray valve 8 to 1511 degrees.

On the 1 m side, y' consisting of the spray flow rate X of the spray water 106 and the main steam flow rate 112 or the feed water flow rate 101 is given to the division element 2 and output to the x/ye spray ratio control element 13, and its output ( The output 103 of the pre-stage desuperheater outlet steam temperature control element 15 is controlled based on the deviation between the target value) 105 and the detected value 104 of the pre-stage desuperheater outlet steam temperature, and this output 103
The opening degree of the front stage spray valve 7 is set to W4.

In addition, as a conventional mechanism, as a method of keeping the spray amount in the later stage desuperheater 5 at a ratio of one foot to the steam amount, the spray n: in the former stage desuperheater 3 is operated to control the population in the later stage desuperheater 5. FIG. 2 shows a method of controlling the steam temperature at the outlet so that the difference in steam temperature becomes -V value.

In the figures, the same reference numerals as in FIG. 1 represent the same or corresponding parts.

Reference numeral 115 indicates a detected value of the artificial steam temperature of the latter stage attemperator, 14 indicates the latter stage attemperator outlet steam temperature control element, and 114 indicates its output.

This conventional device has an output 109 of the main steam temperature control element 10.
The output 114 of the second stage desuperheater dense inlet and outlet steam temperature difference control element 14 is determined by the deviation between the detected value 115 of the steam temperature at the inlet of the second stage desuperheater.
The deviation between the output 114 and the detected value 104 of the steam temperature at the outlet of the front attemperator is controlled, and the opening degree of the front spray valve 7 is controlled by controlling the output 103'fc of the front attemperator outlet steam temperature control element 15. are being adjusted.

The opening degree adjustment of the rear stage spray valve 8 is the same as in the case of FIG.

Therefore, in a mixed combustion boiler, the ratio of recirculated gas to the fuel amount varies depending on the mixed combustion ratio, in a gas recirculation boiler, the ratio of the amount of recirculated gas to the amount of fuel, and in the case of auxiliary combustion in a combined cycle power plant, the amount of gas turbine exhaust gas relative to the amount of fuel in the boiler Depending on the ratio, the heat absorption distribution in each part of the boiler changes significantly.

For example, when co-firing liquid fuel and gaseous fuel, 1. The greater the proportion of liquid fuel, the greater the proportion of heat absorption in the furnace (evaporation section, for example, evaporator 1).

Conversely, the greater the proportion of gaseous fuel, the greater the rate of heat absorption in the flue section (eg superheater 2, 4.6).

For this reason, in a co-firing boiler, the amount of spray in the desuperheater 3 in the previous stage is controlled by manipulating the amount of spray in the desuperheater 3 in the previous stage so that the amount of spray in the desuperheater 5 in the downstream stage is a constant ratio with respect to the steam amount, regardless of the co-firing ratio. The method had the following difficulties.

That is, when the proportion of liquid fuel is large, superheater 2.
4. Since the amount of heat transferred at 6 is reduced, the spray amount must be reduced to prevent the steady state value of the spray amount of the preheating device 3 from reaching the lower limit.

Conversely, when the proportion of gaseous fuel increases, the superheater 2°4.6
As the amount of heat transferred increases, the amount of spray must be increased, and the steady value of the amount of spray from the attemperator 3 at the front stage becomes close to the upper limit.

As a result, the ability to adjust the steam temperature by the desuperheater 3 in the previous stage is reduced, and there is a problem in the ability to suppress fluctuations in steam temperature when disturbances such as load changes occur.

Furthermore, when the heat transfer source ratio of co-firing changes, control is performed in a feedback manner only after the effect appears on the steam temperature, resulting in poor control responsiveness.

Further, the amount of spray in the attemperator 3 at the front stage fluctuates significantly, and when the time constant of the control system is excessive, the fluctuation tends to persist, which also poses a problem from the standpoint of stability.

In addition, in a gas recirculation type boiler, the liquid fuel in the mixed combustion boiler is used as the fuel and the gaseous fuel is used as the recirculated gas amount, or in the auxiliary combustion type boiler in a combined cycle power plant, the liquid fuel is used as the fuel in the boiler and the gaseous fuel is used as the gas turbine. In the case of exhaust gas, the situation is the same as in the case of the co-fired boiler (therefore, the present invention will be explained with respect to the case of the co-fired boiler).

[Purpose of the invention]

Therefore, the present invention was made in view of the problems with conventional devices, and it is possible to maintain the steady value of the spray amount in each attemperator to cope with disturbances such as load changes even under various conditions with different heat transfer source ratios. Control T is set to an appropriate value and at the same time provides a four-forward control function when the heat transfer source ratio changes.
It is an object of the present invention to provide a steam temperature control device for a vessel with a high performance.

[Narrowness of the invention]

The present invention relates to a boiler consisting of a multi-stage spray system with two or more stages, in which steam is generated and superheated using a plurality of heat transfer sources, and a steam superheating system is provided with a multi-stage desuperheater to control the steam temperature. , the heat transfer source (co-firing) ratio is applied via a function element or its output is further passed through a dynamic characteristic element to a spray ratio control element or a latter-stage temperature reduction dense inlet and outlet steam temperature difference control element, depending on the heat transfer source ratio. This is a boiler steam temperature control device that allows the ratio between the water supply level or steam volume to be varied and the spray amount.

[Embodiments of the invention]

FIG. 3 is a block diagram showing the configuration of an embodiment of the present invention.

That is, the control device of the present invention is constructed by adding a new function element 16 and, if necessary, a dynamic characteristic element F to the components in the conventional f);IJ l+ltl device.

Here, the function element 16 is the heat transfer source (co-firing) ratio signal 115
Enter the appropriate spray ratio (
1.16 is its output.

In addition, the dynamic characteristic element 17 performs matching of the dynamic characteristic at the time of a transient change when there is a dynamic timing difference between the change in the heat transfer wire ratio signal 115 and the steam temperature change in each part due to the change in the heat transfer source ratio. At the same time, it is an element that converts the dynamic characteristics of the output signal 116 of the function element 16 and transmits the spray ratio target value 117 in order to realize good feedforward controllability.

Next, the operation of the present invention will be explained.

Spray ratio control element 1 such that the measured spray ratio value x/y from division element 12 matches its target value 117.
3 transmits a target value 105 of the steam temperature at the outlet of the preheater.

The surface element 15 controls the pre-stage attemperator outlet steam temperature by operating the pre-stage spray valve 7 so that the detected value 104 of the pre-stage attemperator outlet steam temperature matches its target value 105 .

That is, by operating the front spray valve 7 and changing the steam temperature 104 at the outlet of the rear attemperator, the spray flow rate 106 in the rear attemperator 5 is changed to the steam flow rate 112 or the feed water flow H-.
fli! so that the ratio with tot becomes a predetermined value. Control takes place.

Here, the function element 16 is the heat transfer source (co-firing) ratio signal 115
is manually transmitted, and a target value 116 of the spray ratio system that is '>Iη in that co-firing state is transmitted. In other words, the proportion of gaseous fuel increases or decreases in the superheater 2. 4. If the heat transfer sleeve in Part 6 is increased or decreased, the spray must be increased or decreased in order to keep the main steam temperature l&:llo constant.

For this reason, the target value 105 of the spray ratio is also changed, and the spray 44. As the power increases, the spray capacity of the post-temperature reducer 5 also increases or decreases.

As a result, conventionally, when the heat transfer source (wamoyaki) ratio changes, all the increase or decrease in spray bias is carried by the front spray valve 7,
The control problem at the time of load change, in which the opening degree of the front spray valve 7 becomes close to the limit value when the heat transfer source (co-firing) ratio is far from the standard value, has been solved.

Furthermore, since the spray valve is operated in a feedforward manner at the same time as the heat transfer source (co-firing) ratio without waiting for a change in steam temperature, responsiveness during transient changes is quickened and controllability is improved.

Furthermore, the dynamic characteristic element 17 can be inserted into the control system when it is necessary to further improve controllability during transient conditions by compensating for the slow speed of signal transmission when the heat transfer source (co-firing) ratio changes. , the change characteristic of the output signal 116 of the function element 16 is changed and transmitted as a spray target value signal.

Note that when the heat transfer source (mixed combustion) ratio changes, the change signal 115 changes the opening degree of the spray valve 7 via the device of the present invention, resulting in a main steam temperature response 110 and a change in heat absorption distribution inside the boiler. Main steam temperature response 110 due to
If the former response is quick, the element with the delay characteristic is used as the dynamic characteristic element 17, and conversely, if the response is slow, the element with the advance characteristic is used as the dynamic characteristic element 17.

Furthermore, the main steam temperature response 110 due to changes in heat absorption distribution.
In a boiler that exhibits a reverse response characteristic, an element of the reverse response characteristic that compensates for this is employed as the dynamic characteristic element 17.

As a result, response matching can be achieved and the heat transfer source (co-firing)
It is possible to obtain a boiler steam temperature control device that exhibits excellent controllability not only when the ratio is steady, but also when the heat transfer source (mixed firing) ratio changes.

FIG. 4 is a block diagram showing the configuration of an embodiment of the present invention.

An example of this function is that in the conventional device shown in FIG.
This method utilizes the fact that if the crystallinity difference is constant, the ratio of the spray flow rate to the steam flow rate will also be approximately constant.

That is, later, the attemperator inlet/outlet steam temperature travel control element 14 converts the temperature difference between the temporary attemperator inlet steam temperature detection value 115 and its outlet steam temperature target value 109 into the temperature difference - standard 1.
19, the pre-stage attemperator outlet steam temperature target value 114 is transmitted and the pre-stage attemperator outlet steam temperature detection value element 15 is used to control the pre-stage spray valve 7.

Furthermore, the function element 18 is a heat transfer source (co-firing) ratio signal 115
Input (-1) The temperature difference value when the spray ratio is appropriate in that co-firing state is transmitted as the temperature difference 1歟fig, 118.

Incidentally, if it is desired to further improve the transient control response when the heat transfer source (co-firing) ratio changes, the dynamic characteristic element 19 is inserted into the system and the output signal 11 of the function element 18 is changed as in the embodiment shown in FIG.
8 is changed and transmitted as a target value 119 of the temperature difference.

〔Effect of the invention〕

According to Kagushi and the present invention, even if the heat transfer source ratio is changed in a boiler that controls steam temperature using a multi-stage spray method, the steam will not be crystallized when the load changes in any state. The temperature can be well controlled. In addition, controllability is improved even during transient changes in the heat transfer source ratio, and the effect of reducing the width of steam temperature fluctuation can be obtained.

[Brief explanation of the drawing]

FIGS. 1 and 2 are block diagrams of a conventional device, and FIGS. 3 and 4 are block diagrams showing an embodiment of the present invention and the construction of an embodiment of a song. DESCRIPTION OF SYMBOLS 1... Evaporator, 2... Pre-stage superheater, 3... Pre-stage desuperheater, 4... Intermediate superheater, 5... Post-stage desuperheater, 6.
...Final superheater, 7.. Front stage spray valve, 8.. Later stage spray valve, 10.. Main steam temperature control element, 11..
- Post-stage desuperheater outlet steam temperature control element, 12... Division element, 13... Spray ratio control element, 14... Post-stage desuperheater outlet steam temperature control element, 15... Pre-stage desuperheater outlet Steam temperature system? ill element, 16.18...function element,
17.19...Dynamic characteristic element. Applicant's agent Kiyoshi Inomata 1

Claims (1)

[Claims] 1. Consists of a two or more stage multi-stage spray system in which steam is generated and superheated using multiple types of heat transfer sources, and the steam temperature is controlled by providing multiple stages of desuperheaters in the steam superheating system. In the boiler,
A boiler steam temperature control device characterized in that the ratio between the amount of water supplied or the amount of steam and the amount of spray is made variable according to the low heat source ratio. 2. In the multi-stage desuperheater, turning on/off the latter stage desuperheater
2. The steam temperature control device for a boiler according to claim 1, wherein the ratio between the amount of water supplied or the amount of steam and the amount of spray is changed by making the outlet steam temperature difference variable in accordance with the low heat source ratio. 3. The steam temperature control device for a boiler according to claim 1, wherein the ratio between the amount of water supplied or the amount of steam is adjusted by a predetermined dynamic response to a change in the low heat source ratio. 4. In a mixed combustion boiler where the heat transfer source uses different types of fuel,
Claim 1 using a co-firing ratio as a low heat source ratio
Bozu's steam temperature control device as described in Section 1. 5. In a gas recirculation boiler in which the heat transfer source is fuel and exhaust gas is recirculated to the furnace, the steam temperature of the boiler according to claim 1, in which the ratio of the amount of fuel to the amount of gas recirculated is used as the low heat source ratio. Control device. 6. In an auxiliary combustion boiler for which the heat transfer source is a combined cycle generator of gas turbine exhaust gas and fuel, the steam temperature of the boiler according to claim 1, in which the low heat source ratio is the ratio of the amount of fuel to the gas turbine exhaust gas salary. Control device.