JPH086891B2 - Boiler forced cooling control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a boiler forced cooling control method after a recirculation type boiler is stopped.

[Prior Art] When inspecting a boiler, the operation of the boiler is stopped and then the cooling of the boiler is waited for. However, waiting for the boiler to cool naturally takes too much time, so that the boiler is forcedly cooled than before.

The conventional forced cooling method of the boiler in the recirculation type boiler is performed manually, and since the boiler cannot be cooled at a certain temperature drop rate or higher to maintain its soundness, the furnace pass outlet temperature, etc. While watching Q, open the Q valve and gradually reduce the recirculation flow rate by the recirculation pump as shown in FIG. 2A, and gradually increase the water supply amount by the water supply pump accordingly, and the cooling rate. Is controlled to be, for example, approximately 50 to 60 ° C./h.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional method, since the operator manually adjusts the recirculation flow rate and the feed water flow rate stepwise, the temperature drop is caused by A'in FIG. It is necessary to pay close attention so that it does not fluctuate and stabilize as shown in Fig. 4, and it does not exceed a certain temperature drop rate. Therefore, there is a problem that it takes time to cool.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to efficiently perform forced cooling of a boiler in the shortest time while maintaining safety.

[Means for Solving the Problem] The present invention is intended to solve the above technical problem, and detects the furnace path outlet temperature of the boiler at the time of forced cooling of the recirculation boiler, and detects the boiler temperature from the furnace path outlet temperature. The opening degree of the Q valve of the circulation passage is programmed to control the recirculation flow rate, and the opening degree of the Q valve is adjusted so that the temperature of the exit of the furnace pass becomes a set temperature drop rate. And a boiler forced cooling control method.

[Operation] Therefore, in the present invention, during forced boiler cooling, the circulation flow rate is controlled by adjusting the opening degree program based on the furnace path outlet temperature so that the opening degree of the Q valve decreases. By adjusting the opening degree of the Q valve so that the temperature becomes the set temperature drop rate, the boiler is efficiently and stably cooled within a short time.

[Examples] Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an apparatus for carrying out the method of the present invention, in which water supplied from a water supply pump 1 becomes steam through a water supply pipe 2, a economizer 4 of a boiler 3 and a furnace path 5. The steam is guided to the steam separator 6, and the steam is guided to a superheater (not shown). On the other hand, the hot water separated by the steam separator 6 is introduced into the separation tank 7, and further merged with the water supply pipe 2 through the recirculation pump 8 and the Q valve 9 to be introduced again into the boiler 3. Has become. Further, the level in the separation tank 7 is detected by the level control device 10, and the hot water is guided to the condenser P.
The level in the separation tank 7 is controlled to be constant by adjusting the valve 11.

In the above, a flow meter 12 is provided at the feed water inlet of the boiler 3 and a flow meter 13 is provided at the exit of the Q valve 9, and flow rate signals 14 and 15 from both flow meters 12 and 13 are added by an adder 16. , The addition signal is input to the subtractor 17 and compared with a preset minimum water supply amount 18, and the controller 19 is set so that the difference becomes zero.
The water supply pump 1 is controlled via.

On the other hand, a thermometer 20 is installed at the furnace pass outlet of the boiler 3,
A temperature signal 21 of the thermometer 20 is led to a subtractor 23 via a first-order delay circuit 22, and a preset cooling target value 24 (for example, lowering the temperature to 100 ° C.) is input to a rate-of-change limiter 25. The signal subjected to the rate of change limitation (for example, 50 to 60 ° C./h) is input to the subtractor 23 to perform the subtraction. Further, the lower signal of the subtractor 23 is guided to the function generator 26 to be converted into the opening of the Q valve 9, and the opening adjustment signal 27 is gain-adjusted by the controller 28 to be introduced into the adder 29, where The opening signal of the Q valve 9 is controlled by the addition signal by adding it to the opening program signal 30 from the function generator 31 in which the opening program is set by the temperature signal 21 from the total 20.

Further, the temperature signal 21 from the thermometer 20 is guided to the function converter 32 to output the air flow rate command 33 for cooling the boiler, and the command 33 and the air flow rate signal from the air flow rate detector 34 are subtracted.
Compare with 35 and controller so that the difference becomes zero
It is configured to control the fan (FDF) via 36.

The water supply pump 1 is controlled by the controller 19 so that the sum of the flow signal 14 of the flow meter 12 at the inlet of the boiler 3 and the flow signal 15 of the flow meter 13 at the outlet of the Q valve 9 becomes equal to the minimum water supply flow rate 18. . Therefore, when the recirculation flow rate from the Q valve 9 increases, the boiler input flow rate decreases correspondingly, and when the recirculation flow rate decreases, the boiler inlet flow rate increases correspondingly, so that the feed water pump 1 is automatically controlled.

In the state where the boiler 3 is stopped, the Q valve 9 is opened and recirculation is performed between the boiler 3 and the separation tank 7,
A small amount of water is supplied by the water supply pump 1 such that the level of the separation tank 7 does not drop (the P valve 11 does not open).

In this state, the function generator 31 sets the field program signal 30 based on the temperature signal 21 of the furnace path outlet temperature from the thermometer 20, and the field 30 of the Q valve 3 is throttled at a predetermined speed by this signal 30. To control. As a result, the recirculation flow rate is gradually decreased and the amount of water supplied by the water supply pump 1 is increased accordingly, so that the furnace path outlet temperature is also gradually decreased.

However, if the opening degree of the Q valve 9 is simply controlled by the opening degree program signal 30, the furnace pass outlet temperature fluctuates,
It cannot be lowered at a stable temperature drop rate of 50-60 ° C / h.

For this purpose, the temperature signal 21 from the thermometer 20 is input to the subtractor 23 via the primary delay circuit 22, and the cooling target value 24 (for example,
(100 ° C), the difference is calculated by comparing with the signal from the rate-of-change limiter 25 that is set so that the temperature up to 50-60 ° C / h, and the difference signal is output by the function generator 26 to adjust the opening. 27, the gain of the opening adjustment signal 27 is adjusted by the controller 28, and the result is introduced into the adder 29.
Add to.

In the above, even if the Q valve 9 is adjusted, the furnace pass outlet temperature does not change immediately. For this reason, the state of the temperature drop in which the temperature signal 21 is delayed by a first order and a predetermined drop rate (50 to
The set opening temperature which drops at 60 ° C./h) is compared and the opening degree program signal 30 is corrected based on the difference.

Therefore, the ratio between the recirculation flow rate by the Q valve 9 and the feed water flow rate by the feed water pump 1 is controlled substantially linearly as shown by the broken line B in FIG. 2, and the furnace pass outlet temperature is shown by the broken line B '. Thus, the boiler 3 can be cooled so as to stably drop to the target temperature within the shortest allowable time.

Further, the temperature signal 21 from the thermometer 20 is function-converted into a required air flow rate by the function generator 32, and the signal is subtracted from the detection signal from the air flow rate detector 34 by the subtractor 35 to obtain a difference. Is obtained, and the fan (FDF) is controlled via the controller 19 based on the difference, the air flow rate can be automatically controlled and the superheater can be cooled in parallel.

It should be noted that the present invention is not limited to the above embodiments, and various changes can be made without departing from the scope of the present invention.

[Advantages of the Invention] As described above, according to the boiler forced cooling control method of the present invention, the recirculation flow rate is controlled by adjusting the opening degree of the Q valve so that the furnace pass outlet temperature has the set temperature drop rate. Therefore, it is possible to achieve the excellent effect that the forced cooling of the boiler can be efficiently performed in the shortest time while stabilizing and maintaining safety.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a diagram showing changes in the flow rate of water supplied to the furnace and the temperature at the exit of the furnace when the boiler is cooled. 1 is a water supply pump, 3 is a boiler, 8 is a recirculation pump, 9 is a Q valve, 12 and 13 are flow meters, 20 is a thermometer, 21 is a temperature signal, 22
Is a primary delay circuit, 23 is a subtractor, 24 is a cooling target value, 25 is a change rate controller, 26 is a function generator, 29 is an adder, 30 is an opening program signal, and 31 is a function generator.

Claims (1)

[Claims] Claim: What is claimed is: 1. When forcedly cooling a boiler of a recirculation type boiler, the temperature of the exit of the furnace pass of the boiler is detected, and the opening of the Q valve of the boiler recirculation flow furnace is programmed from the temperature of the exit of the furnace pass to set the recirculation flow rate. And controlling the opening degree of the Q valve so that the furnace pass outlet temperature has a set temperature drop rate.