JP2006132901A - Heat exchange type blowing method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat exchange type blowing method and device capable of cooling the temperature of a boiler blow water at an outlet of a heat exchanger to a safe temperature (normally below 95°C) for discharge even when the temperature of boiler feed water is high such as 60°C or higher without increasing a heat transfer area. <P>SOLUTION: The heat exchange type blowing method for preheating boiler feed water and cooling blow water to discharge it by bringing the boiler feed water and blow water of a boiler into contact to exchange heat in a heat exchanger is characterized by exchanging heat by a plurality of heat exchangers provided in series, and the heat exchange type blowing device for preheating the boiler feed water and cooling the blow water to discharge it by connecting a blow water discharge pipe 3 from the boiler 1 to the heat exchanger 2, and bringing the boiler feed water and the blow water of the boiler into contact to exchange heat in the heat exchanger 2 is characterized by providing a plurality of heat exchangers 2 in series. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat exchange type blowing method in which when boiler water is blown (blow-off), heat is exchanged between the blow water of the boiler and the boiler feed water, the boiler feed water is preheated and the blow water is cooled and discharged. And device.

When operating the boiler, it is necessary to blow boiler water (continuous blow) in order to prevent various obstacles such as boiler corrosion failure, scale failure, and steam purity reduction due to carry-over due to boiler water quality.
The heat contained in the hot blow drainage is not only discarded but also cannot be overlooked from the viewpoint of preventing global warming.
For this reason, various heat exchange type blow devices which collect heat from blow water and give this to boiler feed water are proposed (for example, refer to patent documents 1, 2, and 3).

In this conventional heat exchange type blower, the blow water discharge pipe from the boiler is connected to the heat exchanger, and the boiler water supply and the boiler blow water are contacted by the heat exchanger in the heat exchanger to exchange heat. The boiler feed water is preheated and the blow water is cooled and discharged (see FIG. 3).
Usually, since the temperature of the water used for boiler feed water is a room temperature level of 20 to 30 ° C., heat exchange is performed using such a heat exchange type blow device, and high temperature blow water such as 170 ° C. is not flushed. The water supply temperature is raised to, for example, about 40 ° C. while being discharged to a safe water temperature of less than 95 ° C., for example, about 70-80 ° C., and heat is recovered satisfactorily. Can do.

  However, in recent years, heat recovery technology has progressed, and measures such as recovering boiler steam condensate and reusing it for boiler feed water have been taken. It tends to be considerably higher than the temperature of 20-30 ° C.

Under such circumstances, when the temperature of the boiler feed water is as high as 60 ° C. or higher, the temperature of the boiler blow water (saturated water) at the outlet of the heat exchanger is set to a safe temperature (usually less than 95 ° C., preferably Has a problem that a large heat exchanger having a very large heat transfer area is required for cooling (heat exchange) to a temperature of less than 90 ° C.).
If the heat transfer area is not increased here, the blow water will not be cooled sufficiently at the outlet of the heat exchanger, and part of it will evaporate, impacting the heat exchanger tubes of the heat exchanger, the float of the flow meter, etc. May be damaged. In particular, when the heat transfer tube is damaged, the boiler blow water leaks to the feed water side, the feed water outlet temperature also exceeds 100 ° C., this high temperature feed water enters the feed water pump, causes cavitation, and the equipment with low heat resistance of the boiler May also swell and damage the boiler plant. In addition, there is a great danger that boiler water is mixed into the water supply, and normal boiler water supply is virtually impossible.
Therefore, when the feed water temperature is high as described above, the fact is that the recovery of heat has been abandoned from the viewpoint of safety of the apparatus or from the viewpoint of avoiding the enlargement (installation space) of the apparatus.

JP 54-16003 A Japanese Patent Laid-Open No. 55-31201 JP 2002-22106 A

  The present invention eliminates the above-mentioned conventional problems, and increases the boiler blow water temperature at the outlet of the heat exchanger even when the boiler feed water temperature is high (for example, 60 ° C. or higher) without increasing the heat transfer area of the heat exchanger. It is an object of the present invention to provide a heat exchange type blowing method and apparatus capable of cooling (heat exchange) and discharging to a safe temperature (usually less than 95 ° C., preferably less than 90 ° C.).

  As a result of intensive studies to solve the above problems, the present inventors have surprisingly found that a plurality of small heat exchangers and a series of large heat exchangers are provided by providing a plurality of small heat exchangers in series. Even when the total heat transfer area of the plurality of heat exchangers is smaller than the case where the boiler feed water temperature is high, for example, 60 ° C. or higher, the boiler blow water temperature at the heat exchanger outlet is It has been found that it can be cooled (heat exchange) to a safe temperature (usually less than 95 ° C., preferably less than 90 ° C.) and discharged, and the present invention has been completed based on this finding. Thus, the idea of providing a plurality of small heat exchangers in series has never been seen.

That is, the present invention according to claim 1 is a heat exchange type blow that preheats the boiler feed water and cools and discharges the blow water by bringing the boiler feed water and the blow water of the boiler into contact with each other by a heat exchanger to perform heat exchange. In the method, a heat exchange type blowing method is provided, wherein heat exchange is performed by a plurality of heat exchangers provided in series.
This invention which concerns on Claim 2 provides the method of Claim 1 whose temperature of boiler feed water is 60 degreeC or more.
The present invention according to claim 3 provides the method according to claim 1 or claim 2, wherein the blow water temperature at the outlet of the heat exchanger is less than 95 ° C.
According to a fourth aspect of the present invention, a blow water discharge pipe from a boiler is connected to a heat exchanger, the boiler water supply and the blow water of the boiler are brought into contact with each other in the heat exchanger, and heat exchange is performed. In a heat exchange type blower that preheats and cools and discharges blow water, a heat exchange type blower provided with a plurality of the heat exchangers in series is provided.

According to the present invention, even when the total heat transfer area of the plurality of heat exchangers is reduced as compared with the case of one large heat exchanger, large heat exchange (heat recovery) is achieved. It has become possible.
That is, according to the present invention, by setting a plurality of smaller heat exchangers in series and performing heat exchange between the feed water and the blow water, the water supply amount, the feed water temperature, the blow water amount, and the blow water temperature are set. Compared with the case of using one heat exchanger having a heat transfer area, a large heat exchange can be obtained even with a smaller heat transfer area.
As a result, even when the boiler feed water temperature is as high as 60 ° C. or higher, the boiler blow water temperature at the outlet of the heat exchanger is cooled to a safe temperature (usually less than 95 ° C., preferably less than 90 ° C.) (heat exchange). As a result, a part of the blow water is vaporized and impacts the heat transfer tube in the heat exchanger, the float of the flow meter, etc., and the equipment is not damaged. Further, the apparatus can be reduced in size accordingly, the strength as a pressure vessel can be easily maintained, and the risk of damage to the heat exchanger is reduced.
Further, according to the present invention, a large amount of heat can be recovered from the blow water, and the heat recovery rate is increased, so that the effects of reducing fuel costs for boiler operation and reducing carbon dioxide emission can be obtained. .
Furthermore, according to the present invention, each heat exchanger can be made smaller, so that it is easy to maintain the strength as a pressure vessel, and it is not within the standards for the first type pressure vessel in the pressure vessel safety regulations of the Ministry of Health, Labor and Welfare. Therefore, it can be manufactured and installed according to the standard of a small pressure vessel or a simple pressure vessel, and there is an advantage that the maintenance can be simplified.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a flow diagram showing one aspect of a heat exchange type blower embodying the present invention. Moreover, FIG. 2 is a flowchart which shows the other aspect of the heat exchange type blow apparatus which is implementing this invention.
In the figure, reference numeral 1 is a boiler, and reference numeral 2 is a heat exchanger. Reference numeral 3 is a blow water discharge pipe from the boiler 1, and reference numeral 4 is a water supply pipe to the boiler 1. Further, reference numeral 5 is a water supply pump, reference numeral 6 is a hot well tank (water supply tank), reference numeral 7 is a blow water drain pipe, and reference numeral 8 is a blow valve.

The water sucked up from the hot well tank (water supply tank) 6 by the water supply pump 5 is usually supplied to the boiler 1 through the heat exchanger 2 and the water supply pipe 4 as shown in FIG. In FIG. 1, a branch is provided in the feed water pipe 4 between the heat exchanger 2 and the boiler 1, and a part of the boiler feed water exchanged with the boiler blow water is returned to the hot well tank (feed water tank) 6. However, this branch can be omitted if necessary.
On the other hand, a blow water discharge pipe 3 from the boiler 1 is connected to the heat exchanger 2, and is discharged from the blow water drain pipe 7 through the heat exchanger 2.
Here, in the heat exchanger 2, the boiler feed water supplied from the boiler 1 to the boiler 1 and the boiler blow water discharged from the boiler 1 through the blow water discharge pipe 3 are brought into contact with each other to exchange heat.
As a result, the boiler feed water is preheated and the blow water is cooled. The preheated boiler feed water is fed to the boiler 1 through the feed pipe 4. On the other hand, the cooled blow water is drained from the blow water drain pipe 7. However, the preheated boiler feed water may be collected in the hot well tank (feed water tank) 6 and circulated again.
If necessary, as shown in FIG. 2, the boiler feed water heat-exchanged with the boiler blow water by the heat exchanger 2 is once put (returned) into the hot well tank (feed water tank) 6, and the hot well tank (feed water) Water can be supplied from the tank 6 to the boiler 1 through the water supply pipe 4.

Here, as described in claim 2, when the temperature of boiler feed water is as high as 60 ° C. or higher, particularly 80 ° C. or higher, the present invention can be used particularly suitably.
As described above, when the temperature of the boiler feed water is as high as 60 ° C. or higher, the temperature of the boiler blow water at the outlet of the heat exchanger is set to a safe temperature (usually less than 95 ° C., preferably 90 ° C.). However, according to the present invention, there is a problem that a large heat exchanger having a very large heat transfer area is required. The conventional problems such as these were solved.

The present invention is characterized in that a plurality of heat exchangers 2 as described above are provided in series, and heat exchange is performed by such heat exchangers 2 provided in series.
In FIG. 1, although the example (1st heat exchanger 2A and 2nd heat exchanger 2B) which provided the two heat exchangers in series is shown, it is not limited to this, As needed 3 or more can be provided in series. For example, when three or more small heat exchangers are provided in series, the total heat transfer area of the heat exchanger 2 is slightly increased as compared with the case where one large heat exchanger is provided. There is an advantage that the blow water temperature at the outlet of the heat exchanger can be remarkably lowered.
In the present invention, a large number of heat exchangers 2 are provided in series to enable large heat exchange (heat recovery).
In the present invention, it is necessary to provide a plurality of heat exchangers in series, and even if a plurality of heat exchangers are provided, the object of the present invention cannot be achieved if they are provided in parallel. The reason is not clear, but it is thought that the fact that the flow rate can be further increased by providing a plurality of heat exchangers in series may be a cause.
Here, the flow of water flowing through the heat exchanger 2 includes two flows: a flow of blow water and a flow on the water supply side (boiler water supply side). From the gist of the present invention, it is indispensable to provide a plurality of heat exchangers 2 in series when viewed from the flow of blow water. In other words, it is necessary to always flow the blow water through the heat exchanger 2 in series, and it is not absolutely essential for the flow on the water supply side (boiler water supply side) to always flow in series. Conceivable.
Therefore, when the pressure loss becomes too large, a configuration in which the water supply side flow (boiler feed water) can be flowed in parallel to the heat exchanger 2 can be adopted as necessary. However, in this case, it is considered that the heat recovery rate slightly decreases (about 5%) as compared with the case where both blow water and boiler feed water are flowed in series with the heat exchanger 2.

In the present invention, the total heat transfer area of a plurality of heat exchangers 2 provided in series is equal to or less than the heat transfer area in the case of only one heat exchanger, Larger heat exchange (heat recovery) can be performed. In other words, for example, by installing two small heat exchangers in series instead of one large heat exchanger, even if the total heat transfer area is equal to or less than that, a larger heat exchange (heat Recovery) can be performed.
According to the present invention, as described in claim 3, the blow water temperature at the outlet of the heat exchanger can be less than 95 ° C, more preferably less than 90 ° C, and a part of the blow water is vaporized. There was no risk of damaging the equipment by impacting the heat transfer tubes in the heat exchanger, the float of the flowmeter, etc.

  In the present invention, a plurality of smaller heat exchangers 2 are provided in series, and heat exchange is performed by such heat exchangers 2 provided in series. It can be performed by a blowing method and a blowing device. Although not shown, for example, a check valve provided in a conventionally known blow device is provided between the water supply pump 5 and the heat exchanger 2. Further, a blow valve 8 for blowing boiler water is provided in the pipe line of the blow water drain pipe 7. Furthermore, an operation control device provided in a conventionally known blow device can be provided. By this operation control device, the blow timing can be controlled by opening the blow 8 valve.

As the boiler 1 in the present invention, not only a boiler generally used in the past, but also a technique incorporating recent heat recovery technology, that is, a method of recovering steam condensate of the boiler and reusing it for boiler feed water It is also possible to use those in which is incorporated. In this case, the boiler feed water temperature before the heat exchange is considerably higher than the temperature of 20 to 30 ° C. in a conventionally used boiler, and is higher than 60 ° C., particularly 80 ° C. or higher. The present invention can be particularly preferably used in such a case.
In the present invention, the boiler feed water and the boiler blow water are heat-exchanged. However, the water for recovering the heat is not necessarily limited to the boiler feed water, and other water that needs to be heated and the boiler blow water. The present invention is also applied to heat exchange, and heat exchange can be performed by a plurality of heat exchangers provided in series.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, the scope of the present invention is not limited at all by these Examples.

Example 1
In the first embodiment, various heat exchangers shown in Table 1 are installed in the blow line of an actual boiler system as shown in FIG. 1 (the present invention) or FIG. 3 to perform heat exchange with water supply. The blow water temperature at the outlet of the heat exchanger, the feed water outlet temperature, and the heat exchange amount were measured. The results are shown in Table 1.
The operating pressure of the boiler was 1 MPa, the blow water temperature was 183 ° C., the blow water amount was 1200 L / h, the feed water temperature was 70 ° C., and the feed water amount was 12000 L / h.
Moreover, all the heat exchangers used the continuous blow apparatus made from Aqua Co., Ltd. (mini blow: registered trademark owned by Aqua Co., Ltd.). The model HOT-1200 has a blow water maximum flow rate of 1200 L / h, the model HOT-1600 has a blow water maximum flow rate of 1600 L / h, and the model HOT-2000 has a blow water maximum flow rate of 2000 L / h.

According to the results in Table 1, in this embodiment, where the feed water temperature is as high as 70 ° C., when one small heat exchanger (HOT-1200) is used, the blow water temperature at the heat exchanger outlet is 111. It can be seen that the temperature is extremely high as ℃. If the blow water temperature at the outlet of the heat exchanger is not less than 95 ° C., there is a risk of causing a damage accident due to steam vibration.
Next, even when one medium heat exchanger (HOT-1600) is used, it can be seen that the blow water temperature at the outlet of the heat exchanger is 104 ° C. and 95 ° C. or higher.
Further, even when one large heat exchanger (HOT-2000) was used, the blow water temperature at the outlet of the heat exchanger could not be made safe below 95 ° C. If a heat exchanger having a larger heat transfer area is used, there is a risk that the heat exchanger may fall under the first type pressure vessel, and maintenance becomes complicated.
In contrast, in the case of the present invention in which two small heat exchangers (HOT-1200) are installed in series, the total transmission is compared with the case where one large heat exchanger (HOT-2000) is used. Despite the small heat area, the blow water temperature at the outlet of the heat exchanger could be lowered to 86 ° C. The amount of heat exchange at this time was 117000 kcal / h, which was larger than when one large heat exchanger (HOT-2000) was used.
When two small heat exchangers (HOT-1200) were installed in parallel, the blow water temperature at the heat exchanger outlet was 102 ° C. and could not be less than 95 ° C.

Example 2
Also in the second embodiment, various heat exchangers shown in Table 2 are installed in the blow line of an actual boiler system as shown in FIG. 1 (the present invention) or FIG. The blow water temperature at the outlet of the heat exchanger, the feed water outlet temperature, and the heat exchange amount were measured. The results are shown in Table 2.
However, in Example 2, the boiler operating pressure is 2 MPa, the blow water temperature is 212 ° C., the blow water amount is 600 L / h, the feed water temperature is 80 ° C., and the feed water amount is 6000 L / h. In comparison, the feed water temperature was as high as 80 ° C., and the blow water temperature was as high as 212 ° C.
Moreover, all the heat exchangers used the continuous blow apparatus (mini blow: registered trademark) by Aquas Corporation. Model HOT-600 has a maximum flow rate on the blow water side of 600 L / h. Other types of heat exchangers are as described in Example 1.

According to the results in Table 2, in Example 2 where the feed water temperature is as high as 80 ° C. and the blow water temperature is as high as 212 ° C., when one small heat exchanger (HOT-1200) is used. Shows that the blow water temperature at the outlet of the heat exchanger is as extremely high as 117 ° C. If the blow water temperature at the outlet of the heat exchanger is not less than 95 ° C., there is a risk of causing a damage accident due to steam vibration.
Next, even when one medium heat exchanger (HOT-1600) is used, it can be seen that the blow water temperature at the outlet of the heat exchanger is 104 ° C. and 95 ° C. or higher.
In addition, even when one large heat exchanger (HOT-2000) was used, the blow water temperature at the outlet of the heat exchanger was 99 ° C. and 95 ° C. or higher.
In contrast, in the case of the present invention in which two small heat exchangers (HOT-1200) are installed in series, the total transmission is compared with the case where one large heat exchanger (HOT-2000) is used. Despite the small heat area, the blow water temperature at the outlet of the heat exchanger could be lowered to 91 ° C. The amount of heat exchange at this time was 72500 kcal / h, which was larger than when one large heat exchanger (HOT-2000) was used.
Furthermore, in the case of the present invention in which three small heat exchangers (HOT-600) are installed in series, the total heat transfer area is larger than when one large heat exchanger (HOT-2000) is used. Although slightly larger, the blow water temperature at the heat exchanger outlet could be remarkably lowered to 85 ° C. The amount of heat exchange at this time was 76200 kcal / h, which was larger than when one large heat exchanger (HOT-2000) was used. In the case of the present invention in which three small heat exchangers (HOT-600) are installed in series in this way, in the case of the present invention in which two small heat exchangers (HOT-1200) are installed in series Compared with, the total heat transfer area was increased, but the blow water temperature at the outlet of the heat exchanger could be lowered, and the amount of heat exchange could be increased.

Example 3
Two small heat exchangers (HOT-1200) are used as shown in Fig. 2 for boilers that have given up the heat recovery of blow water in order to avoid the vaporization of blow water in order to avoid the vaporization of blow water . Heat recovery was attempted by installing in series. As a result, large heat recovery is possible.
That is, it operates for 8 hours a day, 22 days a month for 1 year under the conditions of a blow water amount of 800 L / h, a water supply amount of 12000 L / h, a water supply (inlet) temperature of 80 ° C., a blow water temperature of 183 ° C., and a boiler pressure of 1 MPa. About the boiler (12 months x 22 days x 8 hours / day operation), when two small heat exchangers (HOT-1200) were installed in series and heat recovery was attempted, blow water at the outlet of the heat exchanger The temperature was 83 ° C., and heat recovery was 710,000 yen / year in terms of heavy oil A.
In particular, it has been found that it can contribute to the reduction of 64.5 tons / year in terms of heavy oil A, especially in the recent severe demand for carbon dioxide emission reduction.

It is a flowchart which shows the one aspect | mode of the heat exchange type blower which is implementing this invention. It is a flowchart which shows the other aspect of the heat exchange type blow apparatus which is implementing this invention. It is a flowchart of the conventional heat exchange type blower.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Boiler 2 Heat exchanger 2A 1st heat exchanger 2B 2nd heat exchanger 3 Blow water discharge pipe 4 Water supply pipe 5 Water supply pump 6 Hot well tank 7 Blow water drain pipe 8 Blow valve

Claims (4)

  Heat exchange with multiple units in series in a heat exchange type blow method in which boiler feed water and boiler blow water are brought into contact with a heat exchanger to perform heat exchange to preheat boiler feed water and cool and discharge blow water A heat exchange blow method, wherein heat exchange is performed by a vessel.   The method of Claim 1 that the temperature of boiler feedwater is 60 degreeC or more.   The method according to claim 1 or 2, wherein the blow water temperature at the heat exchanger outlet is less than 95 ° C. The blow water discharge pipe from the boiler is connected to the heat exchanger, and the heat exchange is performed by contacting the boiler feed water and the boiler blow water in the heat exchanger, so that the boiler feed water is preheated and the blow water is cooled and discharged. In the heat exchange type blow apparatus, a plurality of the heat exchangers are provided in series.

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