JPH0694921B2 - Boiler control method and device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a boiler control method for supplying a heating medium that passes through a plurality of heating furnaces together to a drum, and generating steam from the drum, and a method thereof. Regarding the apparatus, in particular, the flow rate of the medium to be heated supplied to each heating furnace is adjusted to control the temperature of the medium to be heated that passes through each heating furnace, and to efficiently operate the boiler. The present invention relates to a control method and its device.

[Prior Art] In various plants such as oil refining, petrochemical, steelmaking, papermaking, and nuclear power generation, various heat recovery means are adopted in order to reduce costs by reducing input energy. For example, in an oil refining plant, there is a large amount of combustion exhaust gas from the heating furnace, so a boiler is used that recovers heat from the exhaust gas from a plurality of heating furnaces to obtain steam.

By the way, conventionally, in a boiler in which steam is generated by a heated medium that has been heat-recovered from a plurality of heating furnaces, temperature control of each heated medium has been performed using an apparatus as shown in FIG.

That is, in the figure, 1 is a medium to be heated (for example,
Water) supply parts 2a, 2b, 2c are heating furnaces for heating the medium to be heated, and 3 is a drum of the medium to be heated which is in a high temperature state after heat recovery, and these form a boiler. Also,
11a, 11b, 11c are flowmeters on the inlet side of the heating medium passing through the heating furnaces 2a, 2b, 2c, 12a, 12b, 12c are also flow rate control valves, 1
3a, 13b, 13c are thermometers on the outlet side, 14 is a drum level detector, 24 is a flow rate comparison that outputs a signal corresponding to the difference between the output signals of the flowmeter 11b and the level detector 14 to the flow rate control valve 12b. It is a container and constitutes a control device by these.

And the conventional temperature control using such a device is
Only the supply system in one heating furnace 2b is controlled by the drum level and the flow rate controlled by cascade control, and the other heating furnaces 2b
The supply system for a and 2b was controlled by adjusting the flow rate based on the operator's settings.

[Problems to be Solved by the Invention] The conventional temperature control described above has the following problems.

One is affected by other heating furnaces for the cascade control with the drum level of the boiler, and cannot supply the heated medium suitable for the corresponding heating furnace load, resulting in large variations in the temperature of the heated medium. And often does not reach saturation temperature.

Since the other two units are controlled by the operator's judgment, they cannot adjust the flow rate accurately and quickly in accordance with the heating furnace load, and the heat recovery rate is low.

The adjustment of the flow rate of the medium to be heated is a step response and is performed while checking the heating state of the medium to be heated, so that it takes a lot of time for the adjustment.

The present invention has been made in view of the above problems, and requires manual labor by automatically supplying a medium to be heated to each supply system of a plurality of heating furnaces at a flow rate suitable for the load of each heating furnace. In other words, it is an object of the present invention to provide a boiler control method and an apparatus therefor capable of efficiently recovering heat.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention control method for a boiler, in which each medium to be heated passing through a plurality of heating furnaces is supplied to a drum together and steam is generated from the drum, , Detecting the deviation between the target value level and the current value level of the boiler drum,
And, calculating the weighted average temperature of the plurality of heated medium,
The deviation between the weighted average temperature and the temperature of each heated medium is obtained, and the temperature deviation of each heated medium and the level deviation are adjusted to obtain the target flow rate of each heated medium. And the current flow rate of each medium to be heated are obtained, and the flow rate of each medium to be heated is adjusted in accordance with the difference.

Further, the boiler control device for carrying out the control method is a level detector for detecting a deviation between a target value level and a current value level of the boiler drum, a weighted average temperature of a heated medium passing through the plurality of heating furnaces. The average temperature calculator for calculating the temperature difference, the signal from this average temperature calculator and the signal from the temperature detector of each medium to be heated are compared to obtain the temperature deviation between them, The deviation signal and the deviation signal from the level detector are added and subtracted to obtain the target flow rate of each medium to be heated.The signal flow adjuster, the target flow rate obtained by each signal subtractor and the current flow rate of each medium to be heated are compared. And a flow rate control valve that adjusts the flow rate of each medium to be heated according to the deviation signal from each flow rate comparator.

[Operation] According to the boiler control method and the apparatus thereof of the present invention, it becomes possible to supply the medium to be heated to each supply system at a flow rate suitable for each heating furnace load of the plurality of heating furnaces, and the target system of each supply system can be supplied. It is possible to average the temperature of the heating medium and bring it to or close to the saturation temperature.

[Examples] Examples of the present invention will be described below.

First, an embodiment of the control device will be described with reference to FIG.

In the figure, the heating medium supply unit 1, a plurality of heating furnaces 2a, 2b,
2c, boiler drum 3, flow meters 11a, 11b, 11c, flow control valve 1
2a, 12b, 12c, thermometers 13a, 13b, 13c, and level detector 14 are the same as conventional ones. As the medium to be heated in the present invention, water, ammonia, chlorofluorocarbon, etc. can be used, and water is particularly preferable. Also, heating furnace 2
Examples of a, 2b and 2c include a waste gas recovery heating furnace and a combustion furnace.

Further, in the figure, reference numeral 15 denotes an average temperature calculator, which calculates a weighted average temperature of each heated medium that has passed through the heating furnaces 2a, 2b, 2c of each supply system. The weighted average temperature is calculated by detecting the flow rate and temperature of the heated medium passing through each supply system with respective flow meters 11a, 11b, 11c and thermometers 13a, 13b, 13c, and based on these data. To do. That is, the flow rate of the heated medium passing through each supply system is A, B, C, and the temperature is Ta, T.
If b and Tc, Can be found at.

Reference numerals 16a, 16b, 16c are temperature comparators in each supply system, and find the deviation between the current temperature detected by each thermometer 13a, 13b, 13c and the temperature calculated by the average temperature calculator 15, respectively.

17a, 17b, 17c is a signal adjuster in each supply system, the deviation signal from each temperature comparator 13a, 13b, 13c, and the deviation signal from the level detector 14 is added and subtracted, each heating furnace 2a, 2b , 2c to obtain the target flow rate of the heated medium.

18a, 18b, 18c is a flow rate comparator in each supply system, the target flow rate signal from each signal regulator 17a, 17b, 17c, and the heating medium actually supplied to each heating furnace 2a, 2b, 2c Flow rate of each supply system by comparing the flow rate of each
Output to 12a, 12b, 12c. Each flow control valve 12a, 12b, 12c,
The opening / closing operation is performed according to the output.

Next, an embodiment of the control method of the present invention, which is performed by using the above-described boiler control device, will be described.

The level detector 14 calculates the deviation between the target level and the current level of the boiler drum.

The temperature of the medium to be heated on the outlet side of each heating furnace 2a, 2b, 2c from each thermometer 13a, 13b, 13c is input to the average temperature calculator 15 every moment, and the weighted average temperature of these mediums to be heated is calculated.

Weighted average temperature calculated by average temperature calculator 15 and each heating furnace
The current temperature of each heated medium that has passed through 2a, 2b, 2c is compared with each temperature comparator 16a, 16b, 16c to obtain the temperature difference of the heated medium in each supply system.

The temperature deviation signal obtained by each temperature comparator 16a, 16b, 16c and the deviation signal at the above-mentioned level are applied to each signal adder / subtractor 17a, 17b, 17
c is added and subtracted to obtain the flow rate of the medium to be heated that matches the load of each heating furnace 2a, 2b, 2c, that is, the target flow rate of the medium to be heated in each supply system.

The target flow rate of the heated medium obtained by each signal regulator 17a, 17b, 17c and the current flow rate of the heated medium detected by each flow meter 11a, 11b, 11c are compared, and the heating medium in each supply system is Calculate the flow deviation.

Operate each flow rate control valve 12a, 12b, 12c according to the flow rate deviation of the medium to be heated obtained by each signal regulator 17a, 17b, 17c, and adjust the flow rate to the heating furnaces 2a, 2b, 2c of each supply system. To do.

As a result, the medium to be heated can be supplied to the heating furnaces 2a, 2b, 2c of each supply system at a flow rate suitable for the load of the heating furnace. As a result, the temperature of the medium to be heated supplied from each heating furnace 2a, 2b, 2c to the drum 3 can be averaged in a state close to the saturation temperature.

FIG. 2 shows the temperature change of the heated medium obtained by this control method, and FIG. 4 shows the temperature change of the heated medium obtained by the conventional example.

The graphs shown in Figs. 2 and 4 show that the fuel gas consumption of the three heating furnaces 2a, 2b, 2c is 70 to 120 (NKm ³ / day), the boiler drum pressure is 21 (Kg / cm ² · G), This is when low pure water was used as the heating medium.

As a result, in the present invention, the variation of the feed water temperature was changed from 15 ° C. to 3 ° C., the average feed water temperature was changed from 213 ° C. to about 220 ° C., and the saturated state under the boiler drum pressure was reached.

The amount of steam generated is about 2 tons for the same amount of fuel gas used.
/ hr increased. This was about 10% higher than the conventional average steam generation rate.

[Effects of the Invention] As described above, according to the boiler control method of the present invention, heat is automatically recovered by automatically supplying the medium to be heated at a flow rate suitable for the load of each heating furnace, so that heat recovery is possible. It can be done efficiently.

Further, according to the boiler control device of the present invention, the above control method can be reliably implemented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a boiler control device of the present invention, FIG. 2 is a graph showing a control result by an embodiment of the boiler control method of the present invention, and FIG. 3 is a block diagram showing a conventional device. FIG. 4 is a graph showing the control result by the conventional control method. 1: Heated medium supply part 2a, 2b, 2c: Heating furnace 3: Boiler drum 11a, 11b, 11c: Flow meter 12a, 12b, 12c: Flow control valve 13a, 13b, 13c: Thermometer 14: Level detector 15 : Average temperature calculator 16a, 16b, 16c: Temperature comparator 17a, 17b, 17c: Signal adjuster 18a, 18b, 18c: Flow comparator.

Claims (3)

[Claims] Claim: What is claimed is: 1. A method for controlling a boiler in which heating mediums passing through a plurality of heating furnaces are combined and supplied to a drum, and steam is generated from the drum, wherein a target value level and a current value level of the boiler drum are controlled. Detecting the deviation, and calculating the weighted average temperature of the plurality of heated media,
The deviation between the weighted average temperature and the temperature of each heated medium is obtained, and the temperature deviation of each heated medium and the level deviation are respectively adjusted to obtain the target flow rate of each heated medium. A boiler control method characterized in that a deviation between each target flow rate of a heating medium and a current flow rate is obtained, and the flow rate of each heating medium is adjusted according to the deviation. 2. A controller for a boiler that supplies heated media passing through a plurality of heating furnaces together to a boiler to generate steam from the boiler, wherein a deviation between a target value level and a current value level of the boiler drum is provided. A level detector for detecting the average temperature calculator for calculating the weighted average temperature of the heated medium passing through the plurality of heating furnaces, a signal from the average temperature calculator, and a temperature detector for each heated medium. A temperature comparator that compares the signals with each other to determine the temperature deviation between them, and a signal adjuster that calculates the target flow rate of each medium to be heated by adjusting the deviation signal from each temperature comparator and the deviation signal from the level detector. , The target flow rate obtained by each signal adjuster and the current flow rate of each heated medium are compared to obtain the flow rate deviation between the two, the flow rate of each heated medium according to the deviation signal from each flow rate comparator Flow to adjust Regulating valve, boiler control device characterized by comprising the city. 3. The boiler control device according to claim 2, wherein the heating furnace is a waste gas recovery heating furnace.