JPS5929765B2 - Heat exchanger temperature control method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control method for a heat exchanger and a structure of the device.

Generally, in a heat exchanger, the area of the heat exchange tube is designed by setting the heat transfer area for effective heat transfer at the rated time, the heat exchanger outlet temperature of the heat receiving fluid to be discharged, etc.

However, in actual operating conditions, due to the balance of operating conditions, the expected fluid outlet conditions, such as steam temperature, cannot be obtained, and in order to adjust the effective heat transfer area, baffle plates are installed on the heat exchange tubes, and heat exchangers are installed. Countermeasures have been taken, such as cutting off or increasing the number of heat exchanger tubes.

However, this is not a desirable method as it takes time and costs.

This invention relates to a method of ejecting fluid in front of a heat exchanger to form a fluid film, changing the effective heat transfer area of the heat exchanger, and controlling the temperature of a fluid such as steam passing through the heat exchanger at the outlet of the heat exchanger. The purpose is to propose equipment.

An embodiment of this invention will be described below with reference to the drawings.

FIG. 1 shows the structure of a steam generator equipped with a device according to the present invention.

The combustion gas burned in the furnace 1 is transferred to a secondary superheater 2, a reheater 3,
It exchanges heat with the primary superheater 4 and the economizer 5, and is discharged through an air preheater (not shown).

Further, for the purpose of preventing the generation of nitrogen oxides (NOx) and controlling the furnace temperature, a part of the combustion gas is supplied to the furnace via the conduit 1 by the recirculation fan 6 as recirculation gas.

In order to implement the present invention in such a steam generator, a pipe line 8 is branched from the pipe line 7 and is located between the secondary superheater 2 and the reheater 3 and at the bottom plate of the high-temperature gas passage 9. It connects the gas injection device 10 and the conduit 8.

In this case, an adjustment damper 11 and, if necessary, a boost fan 12 for boosting the pressure are provided in the conduit 8 to control the amount of gas supplied to the injection device 10 and the gas pressure.

The recirculating gas supplied from the pipe line 8 is ejected from the injection device 10 having a nozzle 13 with a constricted opening and forms a fluid film as shown in FIG. becomes the ineffective heat transfer area B, and the outlet steam temperature of the reheater 3 will decrease.

Further, the above-mentioned area B can be changed by increasing the gas pressure by the boost fan 12 and by operating the adjustment damper 11.

The above explanation has been given by taking a steam generator as an example, and in this case, the fluids that exchange heat are steam and combustion gas, but the present invention is not limited to only gas bodies, but can also be applied to liquids, liquids, and gases. Needless to say, this also applies to the heat exchanger between the two.

Although exhaust gas is used as the ejected fluid in this example, it may also be cold air.

Further, instead of the ejected gas, heated liquid pressure water such as boiler water or blow water may be ejected and vaporized, or may be ejected together with the recirculated gas.

Further, the ejected fluid does not always have to be lower than the fluid flowing in the heat exchange tube, and may be a high temperature gas combusted at the nozzle opening.

Further, the fluid flowing inside the pipe may be cooled by heat exchange.

This invention has the following features.

(1) In a device that controls the temperature of a heat exchanger, a fluid film is formed on the front surface of the heating fluid inflow side of the heat exchanger to change the effective convection heat transfer area by the heating fluid of the heat exchanger. The temperature control method of the device.

(2) A temperature control method for a heat exchanger in which the fluid of the fluid film formed on the front surface of the heating fluid inflow side of the heat exchanger is collected from the exhaust gas pipe and used as recirculated exhaust gas.

(3) The heat exchanger temperature control method uses air as the fluid of the fluid film formed on the front surface of the heating fluid inflow side of the heat exchanger.

(4) A temperature control method for a heat exchanger in which the fluid in the fluid film formed on the front surface of the heating fluid inflow side of the heat exchanger is a liquid.

(5) In a steam generator, a gas having a temperature lower than the exhaust gas of the steam generator is ejected between a superheater and a reheater to form a gas film, and the effective convection heat transfer area of the reheater is changed to generate steam. It must be a temperature control device for a heat exchanger that controls temperature.

By implementing this invention, modification work such as installing baffle plates, adding or cutting heat exchange tubes, etc. is unnecessary,
The effective convection heat transfer area can be changed and controlled, and when using recirculated gas, the heat absorption rate of the superheater, reheater, etc. can be changed without impairing the heat absorption of the steam generator as a whole. It has various effects such as.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a steam generator according to an embodiment of the present invention, and FIG. 2 is a drawing showing details of section A in FIG. 1. 1...Furnace, 2...Secondary superheater, 3.
... Reheater, 6 ... Recirculation fan, 7.
... Conduit, 8 ... Conduit, 9 ...
High temperature gas passage, 10... Injection device, 11...
... Adjustment damper, 12 ... Boost fan,
13...Nozzle, 14...Fluid film, B
...Ineffective heat transfer area.

Claims (1)

[Scope of Claims] 1. A method for controlling the temperature of a heat exchanger by the flow of a heating fluid, in which a fluid film is formed on the front surface of the heating fluid inflow side of the heat exchanger, and the temperature of the heating fluid of the heat exchanger is controlled. A method for controlling the temperature of a heat exchanger, characterized in that the effective convective heat transfer area of the heat exchanger is changed and controlled. 2. Claim 1, characterized in that the fluid of the fluid film formed on the front surface of the heating fluid inflow side of the tube group for convective heat transfer of the heat exchanger is used as recirculated exhaust gas collected from the exhaust gas pipe.
A method for controlling the temperature of a heat exchanger described in Section 1. 3. Temperature control of a heat exchanger according to claim 1, characterized in that the fluid of the fluid film formed on the front surface of the heating fluid inflow side of the tube group for convective heat transfer of the heat exchanger is air. Method. 4. Temperature control of a heat exchanger according to claim 1, characterized in that the fluid of the fluid film formed on the front surface of the heating fluid inflow side of the tube group for convective heat transfer of the heat exchanger is a liquid. Method. 5. In a steam generator, a fluid having a temperature lower than the exhaust gas of the steam generator passing through the superheater and the reheater is ejected between the superheater and the reheater to form a fluid film and change the effective convection heat transfer area of the reheater. 1. A temperature control device for a heat exchanger, comprising a device for controlling steam temperature. 6 A boost fan 12 is connected to the conduit 8 that connects the conduit 7 and the injection device 10 that spouts out a fluid having a lower temperature than the exhaust gas.
6. The temperature control device for a heat exchanger according to claim 5, further comprising: and an adjustment damper 11.