JPH0226121B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the amount of heat exchanged in a condensing section of a separate heat exchanger, and particularly to a control method that can maintain the amount of heat exchanged at a constant value.

The separate type heat exchange device is as shown in Figure 1.
The evaporator section 2 that receives heat and the condensation section 4 that radiates heat are connected by separate insulated steam pipes 6 and condensate pipes 8, and when the evaporator section 2 is heated by, for example, high-temperature exhaust gas, steam of the working fluid is generated. It flows to the condensing section 4 via the steam pipe 6. The vapor of the working fluid flowing into the condensing section 4 exchanges heat with a heated fluid, such as air or water, and then liquefies and becomes a condensate, which flows to the evaporating section 2 via the condensate pipe 8, and the working fluid is It circulates between the evaporation section 2 and the condensation section 4 while undergoing phase transformation. The working fluid is circulated by natural circulation or forced circulation by the circulation pump 10 depending on the height relationship between the evaporating section 2 and the condensing section 4. This separate type heat exchange device has the advantage that the reflux of steam and condensate is good, and that it can effectively function as a heat pipe even if the evaporator section 2 and the condensate section 4 are placed far apart.

However, when such a heat pipe device is actually applied to waste heat recovery, etc., the conditions of the waste heat source such as exhaust gas, which is the heating source, such as temperature and flow rate, usually fluctuate, so The amount of steam generated fluctuates, and the amount of heat exchanged in the condensing section 4, which is a heat radiating section, fluctuates accordingly, so objects to be heated in the condensing section 4, such as hot air for product drying, product cleaning, etc. The temperature conditions of hot water, combustion air for improving combustion efficiency, fuel preheating fluid, etc. fluctuate, and when these heated objects are used, it has a negative impact on the product and combustion efficiency. There was a strong desire to prevent fluctuations.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for controlling the amount of heat exchanged in a condensing section of a separate type heat exchanger, which reduces fluctuations in the amount of heat exchanged, in response to the above-mentioned demands for the prior art.

The gist of the present invention is as follows. In other words, in a separate type heat exchange device in which an evaporating section and a condensing section are arranged separately and connected by an insulated pipe to circulate a working fluid, the amount of steam generated in the evaporating section or the amount of condensed liquid in the condensing section is By detecting either one and comparing the detected value with a set value and controlling the working liquid level of the evaporator, the amount of steam generated in the evaporator is maintained at a constant value, and the steam in the condensing part and the heated This is a method for controlling the amount of steam generated in a separate heat exchanger, which is characterized by controlling the amount of heat exchanged between fluids to a fixed value.

The details of the present invention will be explained by examples. first,
The apparatus used in the present invention will be explained with reference to FIGS. 2 and 3. The embodiment is an example of producing hot water using the sensible heat of the exhaust gas of a steel plate heating furnace.
The exhaust gas 2 enters the evaporator 2 consisting of a plurality of evaporator tubes 16 from the gas outlet 14 and is dissipated into the atmosphere from the chimney 18 at the top. The evaporator 2 communicates with the condensing section 4 through a steam pipe 6, and the lower part of the condensing section 4 communicates with the evaporating section 2 via a condensate pipe 8, a condensate tank 20, and a circulation pump 10. Further, the condensing section 4 includes a cold water pipe 2 that supplies cold water for heat exchange.
2. It is connected to a hot water pipe 24 that discharges heated hot water, and the hot water pipe 24 is connected to a hot water tank 26. FIG. 3 mainly shows the control relationship; the steam pipe 6 is provided with a steam flow meter 28, the condensate pipe 8 is provided with a condensate flow meter 30 immediately after the outlet of the condensing section 4, and the circulation pump 10 is provided with a A branch pipe 32 is provided in the condensate pipe 8 on the outlet side, and a condensate tank 20 is provided.
A level adjustment valve 34 is installed in the branch pipe 32.

Next, the steam generation amount control method of the present invention will be explained.
First, steam flow meter 28 or condensate flow meter 30
The set value is compared with the measured flow rate, and the signal is transmitted to the level adjustment valve 34 to automatically adjust the level of the working fluid in the evaporator 2. It is possible to control the amount of steam generated at a constant value and maintain the temperature of the hot water on the heated side at a constant value. That is, when the flow rate of the steam flow meter 28 or the condensate flow meter 30 becomes larger than the set flow rate, the level adjustment valve 34 operates in the open direction, and the secondary flow rate of the circulation pump 20 returns to the level adjustment valve 34. The amount increases, the flow rate to the evaporator section 2 decreases, and the level of the working fluid in the evaporator section 2 decreases until the measured flow rate reaches the set flow rate. Conversely, if the measured flow rate of the steam flow meter 28 or the condensate flow meter 30 becomes smaller than the set flow rate, the level adjustment valve 34 operates in the closing direction, the flow rate to the evaporator 2 increases, and the working fluid in the evaporator 2 increases. level increases. The above-described control is performed in response to changes in the temperature, flow rate, etc. of the exhaust heat source, and the amount of evaporation is maintained constant, so the amount of heat exchanged to the heated body can also be kept constant. Of course, this control method can be applied whether the pressure inside the heat exchange device is positive pressure or negative pressure.

In this example, the coke oven gas combustion exhaust gas flow rate is 1680 to 2000 Nm ³ /H, and the temperature is 320 to 400°C.
Hot water is produced using combustion exhaust gas that fluctuates within the range of 20 to 200 nm as an exhaust heat source, and Figure 4 shows the temporal changes in the amount of hot water, the temperature of the hot water, the water level in the evaporation section, the amount of exhaust gas, and the temperature of the exhaust gas. As is clear from Figure 4, despite fluctuations in exhaust gas amount and exhaust gas temperature,
We were able to consistently obtain 2t/h of hot water.

In this embodiment, water is used as the working fluid of the heat exchange device, but any suitable heat medium can be used depending on the type of fluid to be heated and the purpose. Further, in the present invention, a flow meter is used to detect the amount of evaporation and the amount of condensed liquid, but instead of this, a thermometer, pressure gauge, or current meter may be used to control the amount of heat exchanged to a constant value.

As is clear from the above embodiments, the present invention measures the amount of steam generated or the amount of condensed liquid, compares it with a set value, controls the working liquid level in the evaporator, and maintains the amount of steam generated in the evaporator at a constant value. This made it possible to keep the amount of heat exchange constant and prevent the negative effects of heat fluctuations during product processing and preheating using waste heat.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of a separate type heat exchange device, Fig. 2 is a layout diagram of a heat exchange device used in an embodiment of the present invention, Fig. 3 is a layout diagram showing control relationships in an embodiment of the present invention, and Fig. 4 1 is a diagram showing time-series changes in hot water amount, hot water temperature, evaporation section water level, exhaust gas amount, and exhaust gas temperature in an example of the present invention. 2... Evaporation section, 4... Condensation section, 6... Steam pipe,
8... Condensate pipe, 10... Circulation pump, 28...
Steam flow meter, 30... Condensate flow meter, 32... Branch pipe, 34... Level adjustment valve.

Claims (1)

[Claims] 1. In a separate type heat exchange device in which an evaporating section and a condensing section are arranged separately and connected by an insulated pipe to circulate a working fluid, either the amount of steam generated in the steam section or the amount of condensed liquid in the condensing section is By detecting one of the two and comparing the detected value with a set value and controlling the working liquid level in the evaporator, the amount of steam generated in the evaporator is maintained at a constant value, and the steam in the condenser and the heated fluid are controlled. A method for controlling the amount of heat exchanged in a condensing section of a separate type heat exchanger, characterized by controlling the amount of heat exchanged with a condensing section to a fixed value.