JPS5995301A - Method and device for controlling circulating water of forced circulation 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 The present invention relates to a method and device for controlling circulating water in a forced circulation boiler, and more particularly, the present invention relates to a method and apparatus for controlling circulating water in a forced circulation boiler, and more particularly, the present invention relates to a method and apparatus for controlling circulating water in a forced circulation boiler, and more particularly, the present invention relates to a method and apparatus for controlling circulating water in a forced circulation boiler. O Regarding a method and apparatus for controlling the circulating water flow rate of the boiler in relation to the heating source for a passing type boiler. One example is a billet cooling boiler that recovers the heat held by the billet at the time of completion of blooming. In this type of boiler, conventionally, the force I heat source such as the billet was intermittently applied to the heat transfer surface of the boiler. Since the circulating water passes through a position facing the boiler (charging → leaving → extraction or charging → extraction), even when there is no heating source on the heat transfer surface of the boiler, the circulating water flows on the heat transfer surface. However, if circulating water is constantly flowing through the heat transfer surface at the same flow rate, if there is no heating source on the heat transfer surface or the temperature of the heating source is low, the heat contained in the circulating water will be dissipated from the heat transfer surface. It's a waste of effort and there's a lot of energy loss.

The present invention was proposed to address the above-mentioned conventional problems, and its main purpose is to provide a circulating water control method for a forced circulation boiler that can reliably reduce heat radiation loss from the heat transfer surface of the boiler. The goal is to provide equipment.

The method of the present invention, which is suitable for this purpose, detects the passing state of the heating source with respect to the heat transfer surface of the boiler when the heat source intermittently passes through a position facing the heat transfer surface of the forced circulation boiler, and If the temperature of the heating source facing the heat transfer surface is above a predetermined temperature, boiler water will flow, but if there is no heat source facing the heat transfer surface of the boiler or its temperature is below the predetermined temperature. The percentage mark is that substantially no boiler water is allowed to flow.

In addition, the device of the present invention controls the circulating state of circulating water in a forced circulation boiler in which a heating source passes intermittently through a position facing the heat transfer surface of the boiler, and the device controls the circulating water from a steam drum. The water is branched and circulated through heat transfer surfaces in multiple parallel sections, and a temperature detector detects the presence or absence of a heating source and its temperature for each heat transfer surface section, and circulating water flows through each heat transfer surface section. The present invention is characterized in that a flow rate control means is provided, and the flow rate of the circulating water flowing through each heat transfer surface section is controlled based on the presence or absence of a heating source detected by the temperature detector.

In other words, the basic idea of the present invention is that if the heating source has not passed through the position relative to the heat transfer surface of the boiler, or if it has, it has already been cooled considerably and the temperature is low, then the boiler circulating water is allowed to flow as is. If so, only the heat retained in the circulating water is radiated from the heat transfer surface, so in this case, the circulating water should not be flowed, or if it should be flowed, it should be flowed in a small amount. For heat recovery boiler equipment with multiple parallel heat transfer sections, temperature detection in each section and flow rate control of circulating water flowing through it can be used to
The idea is to distribute the circulating water and to minimize the heat radiation loss of the heat retained in the circulating water as a whole.

Next, the present invention will be explained using a specific example shown in FIGS. 1 and 2. 1. Example h, bloomed steel billet e.g. diameter 147
~228φ711ffl billet) BT is used as the heating source.

The BT (fillets) are sequentially carried into the cooling bed 1, and after being cooled, they are extracted from the conveyor type cooling bed 1.

In order to recover the heat retained in the billet BT on this cooling bed 1 as steam/steam S, the heat transfer surface 3 of the boiler 2 is
04 is a steam drum that separates steam and water, and 5 is a circulation pump that circulates boiler water W to the heat transfer surface with residual oil. The input temperature is usually 800-900°C, and the mixture is left on the cooling bed 1 for about 2 hours and then cooled to a temperature of about 300-400°C, after which it is extracted from the cooling bed 1. During this time, the boiler 2 receives radiant heat from the billet BT on the boiler heat transfer surface 3, the boiler water W is heated and evaporated, and the heat retained in the billet BT is recovered in the form of steam S.

The charging pitch of fillets and BTs to the cooling bed is usually 5 lo/
In the equipment of this embodiment, the heat source is intermittently supplied facing the boiler heat transfer surface 3. Further, at the end of the period of standing in the cooling bed 1, the heating source is completely cooled down and no effective heat exchange can be performed. In such cases, i.e., when there is no heating source (ie, billet) BT on the heat transfer surface 3, or when the heating source (billet) BT has cooled down, the boiler water must be continuously circulated. If you let
As mentioned above, the heat radiation loss from the heat transfer surface 3 is large, so in the present invention, the presence or absence of the heat source or the temperature of the heat source is detected, and the heat source is placed facing the boiler heat transfer surface 3. When there is no boiler water or when the temperature of the heat source is low, boiler water W
If there is a heating source against the boiler heat transfer surface 3 and the heating source temperature is constant, that is, 300 to 400°C
Only when the above conditions are met, the boiler water W is circulated.

Now, in the equipment shown in Fig. 1, the boiler 2 is composed of three parallel heat transfer surface sections A, B, and C, and each section A-C has heat transfer surfaces 3A to 3C, heat transfer surfaces 3A to 3C, and Temperature sensors 6a to 6c for detecting the temperature of the fillet 1-BT
, temperature control device 7a~ which receives a detection signal from a temperature sensor.
7c, flow rate adjustment valve 8a~ that adjusts the flow rate of boiler water W
8c, orifices 9a to 9c provided on the inlet or outlet side of the flow rate control valve (inlet side in the illustrated example); differential pressure transmitters 10a to 10c for detecting the differential pressure between the inlet and outlet of the orifice;
, flow rate adjustment devices 11a to 11c are provided that receive a differential pressure signal from a differential pressure transmitter and control the opening degree of the flow rate regulating valve. Each section A to C constitutes an independent system,
Although the billet charging timing to each section A to C is different, the boiler water flow rate adjustment in each section A to C is performed as follows.

That is, the temperature sensors 6a to 6c provided on the heat transfer surface 3
The temperature of the billet BT is detected, and the signal is taken into the temperature control devices 7a to 7C. Temperature control device 7a
- 7c have predetermined reference temperatures, and are used to determine whether to open or close the flow control valves 8a-8C based on this reference temperature and the detected temperature signal.

On the other hand, orifices 9a to 9C provided on the inlet side of the flow rate control valves 8a to 8c are for detecting the flow rate to each section A to C, and the differential pressure between the inlet and outlet of the orifices 9a to 9c is is transmitted to the flow rate adjustment devices 11a to llc via the differential pressure transmitters 10a to 10c, and this flow rate adjustment device 11a
~lie and the temperature control device 7a~7
The opening degrees of the flow rate control valves 8a to 8C are controlled by the C command.

Here, when controlling the flow rate, if each heat transfer surface section A
- If there is a heating source in all sections, it is best to flow the same circulating water to each section.If some sections do not have a heating source or the heating source temperature is low, the total The flow rate of circulating water to each section is made to be an optimal distribution amount, and in particular, circulating water is not supplied to sections where no heating source is present.

In this way, the circulating flow rate of boiler water is determined based on the temperature of the heating source located at a position facing the heat transfer surface 3 of the boiler 2. When the temperature of the heating source is low, the circulation of boiler water is stopped or its flow rate is suppressed, so that unnecessary heat radiation from the heat transfer surface in these cases can be avoided.

In the embodiment shown in FIG. 1, the boiler is composed of three sections, but if the number of sections is large and the fluctuation in the circulation flow rate is large, the rotation speed of the circulation pump 5 may be controlled. By doing so, power consumption can also be reduced. Depending on the case, if only the presence or absence of a heating source is to be determined, a known method such as an optical method or a mechanical method may be used in addition to temperature detection.

Next, the effects of the present invention will be explained using experimental examples.

Heat transfer area is 73.8m, heat transfer tube diameter is 76.2φ x 4t1
The amount of heat released from the heat transfer surface was measured using the equipment shown in FIGS. 1 and 2 with a circulation flow rate of 0 to 80 m/hr. The results are shown in FIG. In addition, in Figure 3,
The time when billet extraction from the heat transfer surface is completed is set as 0, the elapsed time thereafter is plotted on the horizontal axis, and the amount of heat dissipated from the heat transfer surface at that time is plotted on the vertical axis.

Comparing the amount of heat released when the circulation flow rate is 80 m/hr (constant throughout the period when the billet is on the heat transfer surface) and Om'/hr (circulation stopped), the following table shows the excess.

Table 1 From these results, it can be seen that according to the present invention, the amount of heat dissipation is considerably reduced.

As described above, according to the present invention, the heat radiation loss on the heat transfer surface can be reliably reduced, and the boiler capacity can be improved accordingly.

[Brief explanation of the drawing]

Fig. 1141 is a schematic diagram of the method and device for controlling the circulation flow rate of a forced circulation boiler according to the present invention, Fig. 2 is a view taken along the line G in Fig. 1', and Fig. 3 shows the amount of heat radiation from the heat transfer surface. It is a graph. 1. Cooling bed 2. Boiler 3. Heat transfer surface 3A~3
C...Heat transfer section 4...Steam drum 5...Circulation pump 6a, 6b, 6c...Temperature sensor 7a, 7b, 7
c...Temperature control device 8a, 8b, 8c...Flow control valve 9a, 9b+ 9cm/orifice 10a, 10b, 10c" differential pressure transmitter

Claims (2)

[Claims] (1) When a heating source intermittently passes through a position facing the heat transfer surface of a forced circulation boiler, the presence or absence of the heat source or its temperature on the boiler heat transfer surface is detected, and the heat source on the boiler heat transfer surface is detected. A forced circulation boiler with a characteristic that boiler water is allowed to flow when the temperature is above a predetermined temperature, but when no heating source is present or when the temperature is below a predetermined temperature, the boiler water is not substantially allowed to flow. Circulating water control method. (2) A device for controlling the circulation state of circulating water in a forced circulation boiler in which a heating source intermittently passes through a position facing the heat transfer surface of the boiler, the circulating water being branched from a steam drum and arranged in parallel. A temperature detector for detecting the presence or absence of a heating source and its temperature for each heat transfer surface section, and means for controlling the flow rate of circulating water flowing through each heat transfer surface section. A circulating water control device for a forced circulation boiler, characterized in that the circulating water control device for a forced circulation boiler is configured to control the flow rate of circulating water flowing through each heat transfer surface section based on the presence or absence of a heating source or the temperature thereof determined by the temperature detector.