JPH0345316B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for controlling the temperature of the cooling water sent out from a multi-cell cooling tower in which a plurality of unit cell sections each equipped with a cooling fan are arranged in a row to maintain it at a target temperature, particularly an automatic control method. Regarding.

In the so-called water industry, such as steel, chemical, and electric power industries, a single water cooling tower is simply not enough to recirculate the large amount of cooling water that is required.
It is not uncommon for individual water cooling towers equipped with cooling fans to be connected as unit cell parts to form a multi-cell cooling tower, and furthermore, multi-cell cooling towers are arranged in a distributed manner to form a tower group. In the case of a multi-cell cooling tower, the side walls between adjacent unit cell parts can be shared or simplified, and the cold water tank for collecting cooling water below can also be consolidated into one tank, resulting in a reduction in construction costs. There are advantages such as requiring less inventory for maintenance.

The cooling capacity of this type of multi-cell cooling tower is designed based on maximum load conditions and is often operated at partial load, so that the cooling water that is circulated during the entire operation period can be cooled to the required temperature. . The cooling capacity required at any given time or point in time varies significantly due to load fluctuations caused by weather conditions such as the outside air wet bulb temperature and the operating status of plants that require cooling water. For example, in winter when the outside temperature drops, The required cooling capacity is approximately 1/3 of that in summer. Therefore, if all of the cooling fans in a multi-cell cooling tower are operated at all times, in the case of large or low temperatures, more cooling capacity than is necessary will be exerted, and energy will be wasted due to excess cooling capacity. be done.

In general, the cooling capacity of a cooling tower can be changed by adjusting the air volume of the cooling fans, and specific methods include adjusting the air volume in stages by increasing or decreasing the number of operating cooling fans, or by adjusting the fan blade. The air volume is continuously adjusted by changing the pitch angle and rotation speed. In either method, if the air volume of the cooling fan is adjusted in response to fluctuations in the load on the cooling tower, the cooling tower will be operated at a capacity that is somewhat close to the required cooling capacity, thereby reducing unnecessary consumption of fan power.

However, in order to maintain a constant temperature of the cooling water sent out from the cooling tower, even if the air volume of the cooling fan is automatically controlled so that the appropriate cooling capacity is always exerted in response to fluctuations in various conditions, the temperature of the cooling water sent out from the cooling tower remains stable. is not easy to maintain.

As a result of various investigations into the causes, it was found that stagnation and short-circuit flow occur in the water held in the cold water tank, and that it is difficult to properly control the water temperature to deal with the unevenness caused by this. I found out. In particular, in multi-cell cooling towers, the cold water tank has to be in the form of a long straight channel, so when controlling the number of operating cooling fans by detecting the temperature of the water at the outlet of the cold water tank, for example, the water that falls into the cold water tank must be in the form of a long straight channel. The temperature of the cooling water varies depending on the longitudinal position of the unit cell, and the difference in water density due to temperature may cause water to stagnate in the upper or lower layer of the cold water tank, causing detection delays, or Water in the upper or lower layer may short-circuit and flow into the cooling water delivery section, and when the load fluctuates, this will cause a considerable detection error, and there is a risk that the control system will malfunction. Even if controlled, fluctuations in the cooling tank outlet water temperature cannot be avoided. One way to deal with this is to actually measure or analyze the characteristics of the cooling tower in question, determine in advance the correlation between fluctuation factors such as outside temperature and the water temperature at the outlet of the cold water tank, and perform predictive control based on this. It is possible that However, even with this method, all the fluctuation factors such as the amount and temperature of water returned from the water plant are related to multiple factors, so it is difficult to judge and control them comprehensively, and the equipment costs are high. cannot obtain sufficient effect.

The present invention has been made to solve this problem, and actively prevents the occurrence of stagnation and short-circuit flow in the flow of cooling water in the cold water tank below the multi-cell cooling tower toward the delivery section. However, the first objective is to ensure that at least the cooling water delivery section delivers water that is equalized in temperature and has a target temperature. For this reason, the unit cooling cell part that makes up the multi-cell cooling tower and the cold water tank below it are divided into the most downstream unit cell part and the upstream unit cell part in relation to the cooling water delivery part from the cold water tank. The former part is divided into a sectioned cold water tank part below the latter part and a common cold water tank part below the latter part, and both cold water tank parts are separated by a partition wall having a communicating part, and the water in the common cold water tank part flows through the communicating part of the partition wall. The cooling water flows into the section cooling water tank section through the cooling water tank and mixes well with the water in this section, so that there is no short-circuit flow toward the cooling water delivery section or stagnation.

Based on this divided configuration of cooling cells and cold water tanks, the air volume adjustment of the cooling fan in the most downstream unit cell part is controlled relatively precisely so that the cooling water sent out in the section cold water tank ultimately matches the target temperature. The cooling fan of the upstream unit cell part is controlled relatively coarsely before the temperature of the cooling water from the common cold water tank part flowing into and mixing with this part exceeds the final control limit of this part. The second purpose is to perform stepwise control over a temperature range.
Therefore, in the most downstream unit cell part, we use a variable air volume fan that can adjust the air volume by changing the rotation speed or fan blade angle according to the detected water temperature of the cooling water in the delivery section, and use this air volume adjustment value as an index. The number of operating cooling fans in the upstream unit cell section is controlled as follows. In this way, the temperature of the cooling water that flows into the section cooling water tank through the communication part of the bulkhead is controlled within a range that can be adjusted at the lowest downstream by the variable air volume cooling fan in this part, and the temperature can change suddenly depending on the outside temperature and return water conditions. Even if there is a problem, the target water supply temperature can be maintained at a stable target temperature by immediately responding to it and quickly following it.

Summarizing the above objectives, problems, and countermeasures, the present invention provides a method for controlling the temperature of cooling water sent out from a multi-cell cooling tower, in which the cooling water at the bottom of the tower is A partition wall that has a communication part between a cold water tank for collecting water and a section cold water tank part below the most downstream unit cell part where the cooling water delivery part is located and a common cooling tank part below the other upstream unit cell parts. The cooling water flowing from the common cold water tank part is mixed with the cooling water in the compartment cold water tank part in the divided cold water tank part, and the air volume of the cooling fan in the most downstream unit cell part is Equipped with variable means, the air volume of the cooling fan is adjusted according to the temperature of the cooling water in the delivery section, and the number of operating cooling fans in the upstream unit cell section is controlled based on this adjusted air volume value. It is characterized by what it did.

Hereinafter, the method of the present invention will be explained in detail with reference to the accompanying drawings.

In FIG. 1, in order to explain the method of the present invention by way of an example, a multi-cell cooling tower 1 consisting of five cells is illustrated as an apparatus used, and this is installed on a cold water tank 2 having the structure described below. The unit cooling cell portions 1-1, 1-2, 1-3, 1-4, 1-5 are cooling fans 3-1, 3-2, 3-3, 3-, respectively.
4, 3-5. Return water from a plant that uses cooling water is distributed to each unit cell section through piping 4, and in the process of subdividing the column packing material section and flowing down, the water is absorbed into each unit cell section by a cooling fan. It contacts and falls into the cold water tank 2 where it is cooled. The cooling water held in the cold water tank 2 is sent to the plant by the water pump 5 of the delivery section and is circulated and reused.

In order to carry out the method of the present invention, the unit cooling cell part and the cold water tank are divided into the most downstream unit cell part 1-5 and the other four upstream unit cell parts 1-1 to 1- in relation to the cooling water delivery part. The former section is divided into a section cold water tank section 2' below the cell section 1-5, and the latter common cold water tank section 2'' below the cell sections 1-1 to 1-4. The cold water tank portions 2', 2'' are separated by a partition wall 6 in the form of a baffle wall that crosses the tank, and this partition wall has a communication portion 7. Therefore, the cooling water that has fallen from the four upstream unit cell parts into the common cold water tank part 2 flows through the communication part 7 into the section cold water tank part 2', where it falls from the most downstream unit cell part 1-5. It is mixed with the retained cooling water, and then sent out from the cooling water delivery section.

In order to improve the mixing of the cooling water, the communication portions 7 may be provided at multiple locations on the partition wall 6, or a perforated plate 8 may be placed in front of the partition wall 6, so that the cooling water in the common cold water tank portion 2 can be mixed in an upper layer. Cooling water is received from the lower layer and the temperature is as averaged as possible. In addition, a baffle wall 9 is provided in the section cooling water tank portion 2 at a distance from the partition wall 6 and facing the cooling water delivery section, so that the upstream cooling water flowing from the communication section 7 is mixed with the water pump 5.
It is best to prevent short-circuit current from flowing to the suction side. In addition, Fig. 2 A and B show a distribution nozzle 11 attached to a communication pipe 10 penetrating the partition wall 6 and disposed inside the cold water tank section 2 to replace the communication section 7, and the water level before and after the partition wall 6 Due to the difference, the flow rate of the cooling water flowing in from the communication part 7 affects stirring, but the
1 can be used for stirring and mixing more effectively.

In particular, in the present invention, the most downstream unit cooling cell portion 1-5
The cooling fan 3-5 is equipped with means for varying the air volume by changing the rotation speed, changing the blade angle, etc. In this example, the air volume variable means is the rotation speed variable means 12 of the cooling fan 3-5. In order to change the air volume, a water temperature detector 13 is provided near the suction side of the pump 5 corresponding to the cooling water delivery section, and the most downstream cooling fan 3 is
Change the air volume by changing the rotation speed of -5. As the rotation speed variable means 12, a frequency converter or a continuously variable transmission may be used to continuously change the rotation speed in accordance with the detected water temperature, or the rotation speed may be changed in multiple stages.

In the present invention, the adjusted air volume value of the cooling fan or other signal value corresponding thereto is further sent to the operating number control device 14, thereby controlling the upstream unit cell portion 1-1.
The cooling fans 3-1 to 3-4 are commanded to start and stop.

Control of the number of operating cooling fans 3-1 to 3-4 of the upstream unit cell portions 1-1 to 1-4 differs depending on the number of cells. That is, as the number of upstream cells increases, the width of the temperature difference that needs to be adjusted toward the target water supply temperature by the cooling fan 3-5 of the most downstream unit cell portion 1-5 becomes smaller; The residence time of the cooling water in the section cooling water tank section 2' is short, so the temperature adjustment time is shortened, and the effects of starting and stopping the cooling fans 1-1 to 1-4 of the upstream cells are significantly reduced. Since the time that appears in the cooling water tank portion 2' generally tends to be prolonged, that is, accompanied by a time delay, the start/stop command is issued at a stage when the cooling fan 3-5 has sufficient capacity to adjust the air volume. For example, when the rotational speed of the cooling fan 3-5 reaches 75% of its change adjustment width, a command is given to start one of the cooling fans in the upstream cell. The rotational speed of the cooling fan 3-5 is low until cooling water whose temperature has decreased from the common cooling tank section 2'' flows into the section cooling tank section 2' due to the activation of the cooling fan of this one upstream cell. The cooling water is maintained in the high speed region and the cooling water sent out is maintained at the target temperature.On the contrary, when the rotation speed of the cooling fans 3-5 becomes less than 25% of its changeable range, one of the cooling fans of the upstream cell is A shutdown is commanded and the outgoing cooling water temperature is maintained at the target temperature by the same but opposite process as before.

When the number of upstream unit cell parts 1-1 to 1-4 is large, the cooling fans 3-1 to 3
-4, the temperature can be controlled in relatively fine steps with respect to the cooling water flowing from the common cooling water tank section 2' to the sectional cooling water tank section 2', and the proportion of the water amount can be increased depending on the number of units started and stopped. The speed control in step 3-5 reduces the range of change in water temperature to be adjusted. In such a case, the most downstream cooling fan 3
A pole number converting motor is used as the rotation speed variable means 12 in -5 to enable changing the rotation speed between full speed, half speed, and stop, and normally operates at half speed, but requires full speed rotation as the cooling water temperature rises. When this happens, one of the cooling fans 3-1 to 3-4 of the upstream cell is started, and conversely, when the most downstream cooling fan 3-5 stops due to a drop in cooling water temperature, cooling of the upstream cell is started. Even with an operating method in which one of the fans is stopped, a stable target water supply temperature can be maintained.

In this way, the cooling fan 3 in the upstream cell section
-1 to 3-4 can be operated as long as they can roughly control the inflow cooling water temperature within a range that allows fine adjustment of the sending water temperature by the cooling fan 3-5 in the section cooling water tank section 2'. , common cold water tank part 2″
The effect of delays caused by stagnation of water in the cooling tower is reduced, and the frequency of starting and stopping the cooling fans is reduced compared to the control method for the number of operating fans in a normal multi-cell cooling tower, which extends the life of each cooling fan. It turns out. In addition, the selection of the cooling fans 3-1 to 3-4 in the upstream cell part to be started and stopped is as follows: fans 3-4 and 3-3 are started in the order closest to the most downstream cell part, and when stopped, the fans are selected in the same order. 3-4, 3-
If the cooling fans 3-1 to 3-4 in the upstream cell portion are stopped in the order of 3, the operating time of the cooling fans 3-1 to 3-4 in the upstream cell portion is made uniform, and oil shortage in the rotating portion due to long-term operation stoppage is prevented.

In addition, the cooling fans 3-1 to 3 in the upstream cell section
It is possible to use a pole number conversion motor for -4.
In this case, the rotation speed can be changed in two steps, and the water temperature can be controlled in finer steps in the common cold water tank section 2'.
The power of the cooling fan is also significantly reduced.

The method of the present invention can be carried out advantageously by making various additions and changes to the apparatus. For example, the third
The figure shows a water pipe 15 that penetrates the partition wall 6 and has an open end in the common cold water tank section 2'' to facilitate the reception of cooling water that has fallen from the upstream cell section 1-1. In this method, when there are many upstream unit cooling cell parts 1-1 to 1-4, the cooling fan 3-1 of the most upstream unit cooling cell part 1-1 is
This can be advantageously employed in cases where the influence of cooling fan 3-5 is likely to exceed the limit adjustable by cooling fan 3-5 if it takes a long time for the influence of cooling fan 3-5 to reach section 2'. Note that it is preferable to provide a plurality of water conduit pipes 15 to reduce the time difference in receiving cooling water from each upstream cell portion. These serve effectively to collect cooling water evenly from each upstream cell section. In this example, two riser pipes 16 are provided in the water pipe 15 to collect water from the overflow of water in the upper layer in the common cold water tank portion 2''.
If the water from the lower layer is also collected at the same time, the dead water area will disappear and the entire area of the cold water tank 2'' will be effectively used, and the rapid temperature changes of the falling cooling water can be absorbed, making it possible to absorb various types of water. Helps stabilize control during sudden load changes.

4A and 4B, a water collection trough 18 is provided at the upper part of the section cooling water tank section 2', and the inflow cooling water from the common cold water tank section 2'' rising from below the section cooling water tank section 2' is shown. and the cooling water falling from the most downstream unit cell portion 1-5 are mixed and taken into the water collection trough 18,
Cooling water is sent out from here. In this embodiment method, when the outside temperature, the amount of return water, and the water temperature suddenly change, the cooling water can be preferentially taken from the most downstream unit cell part 1-5, which is affected quickly by the change, so that the cooling water can be taken from the upstream cell part. The number of operating cooling fans 3-1 to 3-4 can be quickly controlled.

FIG. 1 shows an embodiment in which the end cell of the cell row of a multi-cell cooling tower is the most downstream unit cooling cell section 1-5, and cooling water is sent from the section cooling water tank section 2' below it, and will be described in detail. However, the present invention is not limited to implementation using this arrangement. For example, as shown in FIG. 5, the central cell of the cell row is the most downstream unit cooling cell section 1c, and the upstream unit cell sections 1c are on both sides.
b, 1a are arranged, and the cold water tank part of the most downstream unit cell part 1c is made into a sectional cold water tank part 2', with common cold water tank parts 2'', 2'' on both sides thereof, Cooling water can be delivered from part 2'. The most downstream with respect to the arrayed cell section is to be understood as meaning the unit cooling cell section located above the section cooling water tank section 2 where the cooling water outlet is located. In FIG. 5, the cooling fans of the unit cooling cell portions 1a, 1b, and 1c are shown with reference numerals 3a, 3b, and 3c, and the other parts are shown with the same reference numerals as the equivalent parts in FIG.

As explained above, according to the method of the present invention, difficult problems in control caused by water stagnation, short-circuit flow, etc. in the cold water tank of a multi-cell cooling tower are solved, so the amount of return water and the water temperature are reduced. Even when conditions such as outside temperature suddenly change, stable automatic control is possible and the target water supply temperature is maintained. The driving device and automatic control system of the cooling fan do not need to be sophisticated and complicated, so they are inexpensive and highly reliable. Furthermore, when controlling the water temperature of an existing multi-cell cooling tower, if the method of the present invention is applied, the optimum cooling capacity will always be maintained at a small additional cost, the wastage of fan power will be prevented, and stable temperature and Various effects such as being able to send out a large amount of cooling water can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partial vertical side view showing the overall configuration of a multi-cell cooling tower used in one embodiment of the method of the present invention;
Figure A is a vertical cross-sectional side view showing different configurations of the portion near the partition wall of the multi-cell cooling tower used in the present invention, Figure 2 B is a vertical cross-sectional end view thereof, and Figure 3 is a common cold water tank of the multi-cell cooling tower used in the present invention. FIG. 4A is a vertical side view showing different configurations of the section cooling water tank portion of the multi-cell cooling tower used in the present invention;
FIG. 4B is a vertical cross-sectional end view thereof, and FIG. 5 is a partial vertical cross-sectional side view showing the overall configuration of a multi-cell cooling tower used in another embodiment of the method of the present invention. 1...Multi-cell cooling tower, 1-1, 1-2, 1-
3, 1-4, 1a, 1b... Upstream unit cooling cell part, 1-5, 1c... Most downstream unit cooling cell part,
2... Cold water tank, 2'... Sectional cold water tank part, 2''...
Common cold water tank part, 3-1, 3-2, 3-3, 3-
4, 3-5, 3a, 3b, 3c...cooling fan,
4... Piping, 5... Water pump, 6... Bulkhead, 8
...Communication section, 9...Break wall, 10...Communication pipe, 1
DESCRIPTION OF SYMBOLS 1...Nozzle, 12...Rotation speed variable means, air volume variable means, 13...Water temperature detector, 14...Operation number control device, 15...Water pipe, 16...Rise pipe,
17...Water collection hole, 18...Water collection trough.

Claims (1)

[Scope of Claims] 1. In a multi-cell cooling tower consisting of a plurality of unit cell sections equipped with cooling fans, a cold water tank for collecting cooling water at the bottom of the tower is connected to the most downstream unit cell section where the cooling water delivery section is located. The lower section cold water tank part and the lower common cold water tank part of other upstream unit cells are separated by a partition wall having a communicating part, so that cooling flows into the section cold water tank part from the common cold water tank part. The water is stirred and mixed with the cooling water in the section cooling water tank section, and the cooling fan in the most downstream unit cell section is equipped with an air volume variable means, so that the cooling fan is adjusted according to the temperature of the cooling water in the delivery section. A method for controlling the temperature of cooling water sent out from a multi-cell cooling tower, characterized in that the number of operating cooling fans in the upstream unit cell section is controlled based on the adjusted air volume value. 2. Using a continuously variable rotational speed cooling fan as a cooling fan equipped with an air volume variable means in the most downstream unit cell portion, continuously changing the rotational speed of the cooling fan according to the temperature of the cooling water in the delivery section, 2. The control method according to claim 1, wherein the number of operating cooling fans in the upstream unit cell portion is controlled based on this rotational value. 3 Using a cooling fan driven by a pole number conversion motor as a cooling fan equipped with an air volume variable means for the most downstream unit cell part, one cooling fan in the upstream unit cell part is started and stopped when the pole number conversion motor is rotating at full speed. 2. The control method according to claim 1, wherein the number of cooling fans in operation is controlled so that one cooling fan in the upstream unit cell section is stopped at a certain time. 4. The control method according to claim 1, characterized in that the cooling water flowing in from the common cold water tank portion provides water flow agitation to the cooling water in the separate cold water tank portions. 5. The control method according to claim 1, wherein a water conduit pipe is provided on the upstream side of the partition wall to uniformly collect the cooling water falling from each upstream unit cell portion. 6. Claim 1 characterized in that a water collection trough is provided in the section cooling water tank section to preferentially collect cooling water falling from the most downstream unit cell section.
How to control terms.