JPH09264676A - Cooling tower and method for preventing white smoke - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent the occurrence of a white smoke while enabling a low-cost running and a space saving by supplying a part of a cooling water which is cooled by main body of a cooling to means for supplying cooling water and mixing such a cooling water with a cooling water supplied to the main body of the cooling tower. SOLUTION: In winter season, a part of a cooling water supplied through a cooling water supply pipe 7 is supplied to a cooling water return pipe 8 by way of a bypass pipe 13 and a three-way valve 12 and such a cooling water is mixed with a cooling water supplied from a main body 1 of a cooling tower. Furthermore, a part of the cooling water cooled by the main body 1 of the cooling tower is sucked through a circulating pipe by an operation of a circulating pump 11 and is mixed with a remaining cooling water. Based on a temperature of the cooling water which is measured by water temperature measuring means 6, the circulating pump 11 is operated to control the amount of water supplied to the cooling water supply pipe 7 such that an air discharged from the main body 1 of the cooling tower does not fall in a supersaturated condition relative to an outdoor air temperature. When the cooling water of a low temperature is heat exchange with the outside air in the main body 1 of the cooling tower, the temperature of the moisture sucked air is lowered. Accordingly, even when the discharged air is mixed with the outside air, it does not fall in the supersaturated condition so that the white smoke is not generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling tower for cooling cooling water by heat exchange with outside air and a method for preventing white smoke in the cooling tower.

[0002]

2. Description of the Related Art Generally, in air-conditioning equipment, industrial equipment, etc., a cooling tower is widely used in which cooling water is brought into direct contact with air for heat exchange to perform predetermined cooling. When the heat-exchanged air in the cooling tower is discharged from the cooling tower, the hot and humid air is almost saturated. Therefore, when the outside air temperature is low, such as in winter, the hot and humid air that is discharged becomes supersaturated and is discharged as a white smoke state. The occurrence of this white smoke is caused by sunshine failure,
It has problems such as visual pollution or obstacles to traffic.

In order to prevent the generation of such white smoke,
A method of reducing the humidity of air discharged from the cooling tower has been adopted, and conventionally, cooling towers having various white smoke preventing functions have been developed. Among them, a cooling tower in which a dry air heater is arranged in the wet cooling tower is known. That is, a dry air heater is incorporated in a wet cooling tower, and air is heated and water is cooled by a common blower. Such a cooling tower is an energy-saving type that uses return hot water after cooling as a heat source for heating air in the dry section and does not require a new heat source. In addition, normally, wet operation is performed in the period such as summer when white smoke is unlikely to occur, and dry and wet combined operation is performed in the cold season or during periods when high-humidity white smoke is likely to occur.

FIG. 6 shows a thermal characteristic diagram of the dry / wet type cooling tower. In the figure, the process of cooling and diffusing the humid air discharged in the wet cooling tower is represented by a straight line 2'-1. Of these, the shaded area that crosses the supersaturated area is the area where white smoke is generated due to condensation of the vapor. Therefore, in the dry / wet combined cooling tower, the dry air heated by passing through the dry section and the moist air passing through the wet section are mixed by the blower and discharged from the cooling tower. It is necessary to design the diffusion process so that it does not pass through the supersaturation region as much as possible.

In FIG. 6, a straight line 1-2 shows a change in the state of the air in the wet portion, and a straight line 1-3 shows the change in the state of the air in the dry portion. The air in the state shown in (4) is discharged from the cooling tower. Therefore, when the straight line 4-1 is below the saturation curve, that is, in the non-saturation region, the white smoke is not generated or becomes very small, and the white smoke decreases as the distance from the saturation curve becomes lower.

[0006]

The conventional dry / wet type cooling tower described above requires a space for incorporating the dry air heater in the cooling tower, and a connecting pipe for the dry air heater. However, there is a problem in that the outer dimensions, especially the dimension in the height direction, becomes large. In addition, there is a problem in that the manufacturing cost is also increased accordingly.

Further, although the dry air and the moist air are mixed by an axial fan, it is difficult to sufficiently mix them, which is an obstacle to complete generation of white smoke. Was becoming.

[0008] The present invention has been proposed to solve the problems of the prior art as described above.
An object of the present invention is to provide a cooling tower that effectively prevents generation of white smoke while realizing low cost and space saving.

[0009]

In order to achieve the above object, the cooling tower according to the invention of claim 1 cools the cooling water heated on the load side by exchanging heat with the outside air to perform heat exchange. Cooling tower body that discharges
In a cooling tower having cooling water supply means for supplying cooling water from the load side to the cooling tower body, and cooling water returning means for supplying cooling water cooled in the cooling tower body to the load side, It is characterized by comprising a cooling water circulating means for supplying a part of the cooling water cooled in the cooling tower main body to the cooling water supply means and mixing it with the cooling water supplied to the cooling tower main body.

According to the first aspect of the invention, the following operation is performed in the winter when white smoke is likely to occur. That is,
Before the cooling water heated on the load side is supplied to the cooling tower body, a part of the cooling water discharged from the cooling tower body is mixed with the cooling water to lower the temperature. For this reason, the temperature of the exhaust air generated as a result of heat exchange of the cooling water in the cooling tower body is considerably lower than that of the conventional cooling tower, the temperature difference from the outside air temperature is reduced, and even if mixed with the outside air, it is oversaturated. Not in a state. Therefore, it is possible to effectively prevent the generation of white smoke even in the winter when the outside air temperature decreases. In addition, the installation space can be reduced as compared with a conventional cooling tower in which a dry air heater is incorporated in a wet cooling tower.

According to a second aspect of the present invention, in the cooling tower according to the first aspect of the present invention, the cooling water circulation means includes a circulation pipe connected from the cooling means to the cooling water supply means, and the cooling means. It is characterized by comprising a cooling pump for supplying the cooled cooling water to the cooling water supply means through the circulation pipe.

According to the second aspect of the present invention, since only the space for the circulation pipe and the circulation pump is required, the installation space and the size can be reduced as compared with the conventional combined cooling / drying type cooling tower.

A cooling tower according to a third aspect of the present invention is the cooling tower according to the first or second aspect of the present invention, wherein the cooling water supply means and the cooling water returning means are connected to each other by bypass means, and the bypass means is connected to the cooling means. A three-way valve for controlling the mixing of the cooling water supplied from the cooling water supply means and the cooling water passing through the cooling water returning means is provided.

According to the third aspect of the invention, in winter, the temperature of the cooling water supplied to the cooling tower main body is lowered, so that the temperature of the cooling water after cooling is also lowered. Therefore, the temperature of the cooling water supplied to the load side can be appropriately raised by appropriately mixing the cooling water before cooling supplied from the load side and the cooling water after cooling by the bypass pipe and the three-way valve. This makes it possible to supply cooling water having the same temperature as in summer to the load side.

According to a fourth aspect of the present invention, there is provided a method for preventing white smoke in a cooling tower, wherein cooling water heated on the load side is supplied, and the cooling water is heat-exchanged with outside air to cool the heat-exchanged air. In the white smoke prevention method for a cooling tower that discharges, in winter, before supplying the cooling water from the load side to the cooling tower, the cooling water is a part of the cooling water cooled in the cooling tower. It is characterized by mixing.

According to the fourth aspect of the present invention, during the winter when white smoke is likely to occur, the cooling water heated on the load side is mixed with the low-temperature cooling water cooled in the cooling tower. As a result, the temperature of the cooling water supplied to the cooling tower drops, and the temperature of the exhaust air generated by heat exchange in the cooling tower drops. Therefore, it is possible to effectively prevent the generation of white smoke even in the winter when the outside air temperature decreases.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a cooling tower according to the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a conceptual diagram showing the structure of a cooling tower according to this embodiment. In the figure, a packed bed (not shown) is housed in the cooling tower body 1, and a spraying device 2 for spraying cooling water to the packed bed is arranged above the packed bed. Further, the cooling tower main body 1 is provided with air suction ports 3 on opposite side surfaces, and outside air is sucked into the tower through the air suction ports 3.

A fan 4 is provided on the upper part of the cooling tower body 1.
Are arranged. By driving the fan 4, the outside air sucked into the cooling tower body 1 from the air suction port 3 exchanges heat with the cooling water. As a result, the air that has absorbed moisture and has a high temperature is sucked by the fan 4 and exhausted to the outside of the tower. Reference numeral 5 denotes a cooling water tank, which stores cooling water that has cooled by exchanging heat with the outside air. Further, 6 is a water thermometer, which measures the water temperature of the cooling water stored in the cooling water tank 5.

A cooling water supply pipe 7 supplies cooling water whose temperature has risen on the load side (not shown) to the cooling tower body 1. On the other hand, 8 is a cooling water return pipe, and the cooling water stored in the cooling water tank 5 is supplied to the load side through the cooling water return pipe 8 by the action of the return pump 9. And
This cooling water is again supplied to the cooling tower body 1 by the cooling water supply pipe 7.

A circulation pipe 10 supplies the cooling water stored in the cooling water tank 5 to the cooling water supply pipe 7 by the action of the circulation pump 11. That is, the circulation pipe 10
Is provided for mixing the cooling water cooled in the cooling tower body 1 with the high temperature cooling water supplied from the load side. As a result, the temperature of the cooling water supplied from the load side to the cooling tower body 1 and sprayed by the spraying device 2 decreases.

The circulation pump 11 is operated and controlled by inverter control or the like based on the water temperature of the cooling water measured by the water temperature gauge 6 and the outside air temperature measured by a thermometer (not shown). Further, 12 is a three-way valve, which is connected to the cooling water return pipe 8 and the bypass pipe 13 that connects the cooling water supply pipe 7 and the cooling water return pipe 8.

Next, the operation of the cooling tower according to this embodiment will be described. First, FIG. 2 is a conceptual diagram illustrating the operation of the cooling tower in summer. As shown in FIG. 2, the bypass pipe 13, the circulation pipe 10, and the circulation pump 11 are not used during the winter. That is, the cooling water supplied from the cooling water supply pipe 7 to the cooling tower main body 1 is sprayed to the packed bed (not shown) by the spraying device 2 and cooled by exchanging heat with the outside air sucked from the air suction port 3, Cooling water tank 5
Stored in Then, by the action of the return pump 9, the cooling water is supplied to the load side from the return pipe 8.

A specific case will be described below. For example,
In this case, the wet-bulb temperature of the outside air is 27 ° C, and the approach in this cooling tower is 5 ° C. Further, it is assumed that 100 liters of cooling water heated to 37 ° C. on the load side is supplied from the cooling water supply pipe 7. This cooling water is supplied to the cooling tower body 1 and cooled to 32 ° C.,
It returns to the cooling water return pipe 8 and is again supplied to the load side by the return pump 9.

FIG. 3 is a thermal characteristic diagram showing the thermal characteristics of the cooling tower in summer. In the figure, the straight line 4-1 is
The change of the state of exhaust air in the summer is shown. in this way,
In summer, straight line 4-1 is below the saturation curve, so white smoke does not occur.

On the other hand, FIG. 4 is a conceptual diagram for explaining the operation of the cooling tower in winter. As shown in the figure, in winter,
Bypass pipe 13, circulation pipe 10, and circulation pump 11
Is used. Specifically, a part of the cooling water supplied by the cooling water supply pipe 7 is supplied to the bypass pipe 13 and the three-way valve 1.
It is supplied to the cooling water return pipe 8 via 2 and mixed with the cooling water from the cooling tower body 1. Further, a part of the cooling water cooled by the cooling tower main body 1 is sucked up by the circulation pipe 10 by the action of the circulation pump 11 and mixed with the remaining cooling water of the cooling water supply pipe 7 to form the cooling tower main body 1 Is supplied to. Here, the circulation pump 11 uses the cooling water supply pipe 7 to prevent the air discharged from the cooling tower body 1 from becoming supersaturated with respect to the outside air temperature based on the cooling water temperature measured by the cooling water temperature gauge 6. Control the amount of cooling water supplied to.

A specific case will be described below. For example,
In this case, the wet-bulb temperature of the outside air is −3 ° C., and the approach in this cooling tower is 7 ° C. Further, it is assumed that 100 liters of cooling water at 37 ° C. is supplied from the load side (not shown) from the cooling water supply pipe 7 as in the case of the summer. Of the cooling water of 37 ° C., 85 liters are supplied to the cooling water return pipe 8 through the bypass pipe 13 by controlling the three-way valve 12. The remaining 15 liters are mixed with 85 liters of cooling water at 4 ° C. from the circulation pipe 10 to obtain 100 liters of cooling water, and the cooling tower main body 1
Is supplied to. At this time, the temperature of 100 liters of cooling water is 9 degreeC.

100 liters of the cooling water of 9 ° C. is cooled to 4 ° C. in the cooling tower body 1. And 15 liters of it is discharged by the cooling water return pipe 8,
By the control of the three-way valve 12, 85 liters of the cooling water at 37 ° C. is appropriately mixed, and the cooling water at 32 ° C. is supplied to the load side. The remaining 85 liters of cooling water is supplied from the circulation pipe 10 to the cooling water supply pipe 7 by the circulation pump 11.
Is supplied to. Then, the cooling water supplied from the circulation pipe 10 is mixed with the cooling water from the load side as described above, thereby lowering the temperature of the high-temperature cooling water from the load side, and the cooling tower body 1 Is supplied to.

FIG. 5 is a thermal characteristic diagram showing the thermal characteristics of the present cooling tower in winter. In the same figure, the straight line 2'-1 shows the state change of the exhaust air in winter in the conventional wet cooling tower, and the straight line 4-1 shows the change state of the exhaust air in winter in this cooling tower. In this way, in this cooling tower,
Since the straight line 4-1 is below the saturation curve, white smoke does not occur.

As described above, according to this embodiment, the following effects can be obtained by performing the above-described operation in winter. That is, the high-temperature cooling water heated on the load side is mixed with the low-temperature cooling water from the cooling tower body 1 to lower the water temperature. When such low-temperature cooling water is supplied to the cooling tower body 1 and exchanges heat with the outside air, as a result, the temperature of the absorbed air becomes considerably lower than in the conventional case. That is, since the temperature of the exhausted air decreases with respect to the outside air temperature, even if the exhausted air is mixed with the outside air, the exhausted air does not become oversaturated and white smoke can be prevented from being generated. Therefore, the amount of cooling water supplied to the cooling water supply pipe 7 is controlled by the circulation pump 11, and cooling is supplied to the cooling tower body 1 so that white smoke does not occur even if the exhaust air is mixed with the outside air. Adjust the water temperature.

Further, in the present embodiment, since it is sufficient to provide the three-way valve 12, the circulation pipe 10, and the circulation pump 11, the installation space can be reduced as compared with the cooling tower to which the dry air heater is added. It is possible to reduce the production cost. Furthermore, for conventional cooling towers,
It can be easily applied by attaching the three-way valve 12 or the like.

[0032]

As described above, according to the present invention, as compared with the conventional cooling tower having the white smoke prevention function, the installation space can be reduced, the cost can be reduced, and the generation of white smoke can be prevented. It can be effectively prevented.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a configuration of a cooling tower according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram illustrating the operation of the cooling tower according to the embodiment in summer.

FIG. 3 is a thermal characteristic diagram showing the thermal characteristics in the summer of the cooling tower according to the same embodiment.

FIG. 4 is a conceptual diagram illustrating the operation of the cooling tower according to the same embodiment in winter.

FIG. 5 is a thermal characteristic diagram showing winter thermal characteristics of the cooling tower according to the same embodiment.

FIG. 6 is a thermal characteristic diagram showing the thermal characteristics of a conventional dry / wet type cooling tower.

[Explanation of symbols]

 1 ... Cooling tower body 2 ... Spraying device 3 ... Air inlet 4 ... Fan 5 ... Cooling water tank 6 ... Water temperature gauge 7 ... Cooling water supply pipe 8 ... Cooling water return pipe 9 ... Return pump 10 ... Circulation pipe 11 ... Circulation pump 12 ... Three-way valve 13 ... Bypass pipe

Claims (4)

[Claims] 1. A cooling tower body for cooling cooling water heated on the load side by exchanging heat with the outside air and discharging the heat-exchanged air, and cooling water from the load side for the cooling tower body. A cooling water supply means for supplying the cooling water cooled in the cooling tower body to the load side, and one of the cooling water cooled in the cooling tower body. The cooling tower is provided with a cooling water circulating means for supplying the cooling water to the cooling water supply means and mixing it with the cooling water supplied to the cooling tower body. 2. The cooling water circulation means includes a circulation pipe connected from the cooling means to the cooling water supply means, and cooling water cooled by the cooling means via the circulation pipe. The cooling tower according to claim 1, comprising a circulation pump that supplies the supply means. 3. A bypass unit connecting the cooling water supply unit and the cooling water returning unit, and a cooling water supplied from the cooling water supplying unit and the cooling water returning unit through the bypass unit. The cooling tower according to claim 1 or 2, further comprising: a three-way valve that controls mixing with the cooling water. 4. A method for preventing white smoke in a cooling tower, wherein cooling water heated on the load side is supplied, the cooling water is cooled by exchanging heat with the outside air, and the heat-exchanged air is discharged. The white smoke prevention of the cooling tower, characterized in that, before supplying the cooling water from the load side to the cooling tower, a part of the cooling water cooled in the cooling tower is mixed with the cooling water. Method.