JPS6226711Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a corrosion prevention structure for a heat exchanger. Specifically, _the present invention relates to _a corrosion prevention structure for a heat exchanger. This involves a corrosion-preventing structure for a heat exchanger that prevents sulfuric acid corrosion caused by sulfuric acid water.

A heat exchanger that arranges a large number of smoke pipes in a metal case, circulates heated combustion gas through the smoke pipes, and sends a fluid to be heated in a direction crossing the flow direction of the heated combustion gas to exchange heat; In a so-called shell-and-tube heat exchanger, for example, when the heat exchanger itself is still at a low temperature at the start of the heat exchanger, or when the heated combustion gas has not yet reached a sufficient thermal combustion state and is in a low-temperature combustion state. When the sulfuric acid gas (H ₂ SO ₄ ) in the combustion gas is supplied with a It has the disadvantage of causing sulfuric acid corrosion.

Therefore, conventionally, in order to prevent sulfuric acid corrosion of such a heat exchanger, combustion gas in a low temperature state is bypassed so that it does not pass through the heat exchanger.

By applying materials or surface treatment that are resistant to sulfuric acid corrosion, a heat exchanger that does not corrode even when low-temperature combustion gas is passed through the heat exchanger is provided.

etc. are being implemented.

However, all of these corrosion prevention means not only increase the cost of the heat exchanger, but also have the drawback that the combustion gas bypass method is wasteful from the standpoint of recovering exhaust heat (energy saving).

The present invention solves these drawbacks of conventional heat exchangers, and in shell and tube heat exchangers,
The areas susceptible to sulfuric acid corrosion differ depending on how the heated fluid flows, but in all cases the combustion gas is most likely to be cooled down in the smoke pipe through which the combustion gas passes, in other words, the area where the surface temperature of the smoke pipe is least likely to rise. To provide a corrosion-preventing structure for a heat exchanger that enables opening and closing of the smoke pipe inlet using a bimetal that operates at a temperature above the sulfuric acid dew point at the smoke pipe inlet end where sulfuric acid corrosion is expected. The purpose is to

According to the present invention, such a purpose is achieved by disposing a large number of smoke pipes in a metal case, allowing heated combustion gas to flow through the smoke pipes, and directing the heated fluid in a direction crossing the flow direction of the heated combustion gas. A corrosion prevention structure for a heat exchanger for parts of the heat exchanger that are likely to suffer from sulfuric acid corrosion, which are likely to suffer from sulfuric acid corrosion when heated combustion gas flows through the smoke pipe. The smoke tube closing cap placed at the heated combustion gas inflow end of the smoke tube placed in This is achieved by the anti-corrosion structure of the heat exchanger, which is characterized in that a closing cap operated by the heat exchanger is attached to the flue section.

Embodiments of the present invention will be described below based on the accompanying drawings.

The corrosion prevention structure of the heat exchanger according to the present invention, as shown in FIG. It consists of a cap 1 and a bimetal 2 that opens and closes a smoke pipe 3 by detecting heat.

Under such a configuration, as shown in FIG. 2, when the heated combustion gas 4 is at a low temperature, such as during cold start operation, and the heat exchanger 7 can be preheated, the low temperature section is heated. A cap 1 attached to the inlet end of a certain smoke pipe 3 covers the inlet end of the smoke pipe, blocks the inlet of the smoke pipe 3, and directs the heated combustion gas 4 to the smoke pipe 3 in the low-temperature area until the temperature reaches a predetermined temperature. prevent the influx of

When the heated combustion gas 4 etc. becomes high temperature and the bimetal reaches a predetermined temperature or higher, the cap 1 attached to the inlet end of the smoke pipe 3 is opened as shown in FIG.
is removed from the inlet end of the smoke pipe 3 by the bimetal 2,
The smoke pipe 3 is opened, and the heated combustion gas 4 is allowed to flow into the smoke pipe 3, exchange heat with the heated fluid 5, and discharged to the outside.

FIG. 4 shows an enlarged view of part A of another embodiment of the corrosion prevention structure for a heat exchanger according to the present invention.

Figures 4a and 4b show that the inlet end of the smoke tube 3 is opened and closed by two bimetal wires attached to the lower side of the smoke tube 3, and a shows the state in which the inlet end of the smoke tube 3 is closed at a temperature below a predetermined temperature, and b becomes higher than the specified temperature,
The inlet end of the smoke pipe 3 is shown open.

Figures 4c and d open and close the inlet end of the smoke pipe 3 using two bimetal wires or two thin plates attached to the separator 6, and c shows the state in which the inlet end of the smoke pipe 3 is closed at a predetermined temperature or lower. , and b indicates a state in which the temperature reaches a predetermined temperature or higher and the inlet end of the smoke pipe 3 is opened.

Fig. 4 e and f open and close the inlet end of the smoke pipe 3 using two bimetals 2 attached to the smoke pipe 3, and e shows the state in which the inlet end of the smoke pipe 3 is closed at a predetermined temperature or lower. , and f indicates a state in which the temperature reaches a predetermined temperature or higher and the inlet end of the smoke pipe 3 is opened.

Figures 4g and 4h show that part of the smoke pipe 3 is composed of a spiral bimetal 2, and the bimetal 2 changes as the temperature changes.
The inlet end of the smoke tube 3 is opened and closed by the expansion and contraction of , where g indicates the state in which the inlet end of the smoke tube 3 is closed when the temperature is below a predetermined temperature, and h indicates the state in which the inlet end of the smoke tube 3 is opened when the temperature exceeds a predetermined temperature. Indicates the state in which

As is clear from the above, according to the corrosion prevention structure of the heat exchanger according to the present invention, in the shell and tube type heat exchanger, the parts susceptible to sulfuric acid corrosion vary depending on the way the heated fluid flows. By focusing on the fact that the combustion gas is most likely to be cooled in the smoke pipe where the combustion gas passes, in other words, the surface temperature of the smoke pipe is concentrated in the area where it is difficult to rise, we have determined in advance the location of the smoke pipe entrance where sulfuric acid corrosion is expected. Finally, the bimetal, which operates at a temperature above the sulfuric acid dew point, has the advantage of making it possible to open and close the flue inlet, thereby preventing sulfuric acid corrosion of the flue pipe of the heat exchanger.

[Brief explanation of the drawing]

Figure 1 is a front cross-sectional view of the corrosion prevention structure of a heat exchanger according to the present invention, Figure 2 is an enlarged view of part A in Figure 1 (when the bimetal is at a predetermined temperature or lower), and Figure 3 is the same as in Figure 1. FIG. 4 is an enlarged view of part A of another embodiment of the corrosion prevention structure for a heat exchanger according to the present invention. 1... Cap, 2... Bimetal, 3... Smoke pipe, 4... Heated combustion gas, 5... Fluid to be heated, 6
...Separator, 7...Heat exchanger.

Claims (1)

[Scope of Claim for Utility Model Registration] A large number of smoke pipes are arranged in a metal case, heated combustion gas is made to flow through the smoke pipes, and heated fluid is sent in a direction crossing the flow direction of the heated combustion gas. , a corrosion prevention structure for a heat exchanger for a portion of the heat exchanger that is likely to suffer from sulfuric acid corrosion, which is located in a portion of the smoke pipe that is likely to suffer from sulfuric acid corrosion when heated combustion gas is distributed. The smoke tube closing cap placed at the heated combustion gas inflow end of the smoke tube is operated by the bimetal to open the smoke tube end when the bimetal reaches a predetermined temperature or higher, and to close the smoke tube end when the bimetal reaches a predetermined temperature or lower. A corrosion-preventing structure for a heat exchanger characterized by a closed cap attached to the smoke pipe.