Closed-loop cooling tower antifreeze measures

1. A bypass water pipe is installed to carry most or all of the water normally used during winter operation. The bypass pipe is connected to the inlet pipe of the cooling tower and leads directly to the collection basin, where it mixes with the existing cold water already present in the basin. This process effectively regulates the basin water temperature, helping to raise it and thus preventing freezing. When introducing the bypass pipe system, it’s essential to start the circulating pump first upon unit startup, while slightly opening the valve on the standby pipeline—just a few turns—to allow a small amount of circulating water to flow through the line without passing through the fill media for heat dissipation. Instead, this water flows directly into the collection basin, warming both the pipeline and the basin water. The primary benefit of this approach is that it prevents circulating water—with either no heat load or a very low heat load—from freezing as it passes through the fill media. By doing so, it safeguards the inactive cooling tower and its associated pipelines from frost damage. Similarly, when shutting down the unit, the steam turbine should be stopped before the circulating pump is turned off. This sequence helps avoid the same freezing issue described earlier. Moreover, adjusting the valve’s opening degree directly influences the amount of cooling tower circulation water entering the system, effectively serving as an indirect method for hot-water bypass regulation.

2. Steam tracing, due to its convenient steam availability, high latent heat of condensation, and easy temperature control, is an effective insulation and freeze-protection measure widely used in various engineering projects. The principle behind steam tracing is to utilize the heat emitted by the tracing medium—either directly or indirectly through steam-water heat exchange—to compensate for the heat loss in the object being traced, thereby achieving the desired effects of heating, insulation, or freeze prevention. In the case of cooling tower freeze protection, steam tracing involves routing a steam pipe from the main steam line into the cooling tower’s sump, where a coil is installed at the bottom of the sump. As steam flows through the coil, it transfers heat to the water in the sump via steam-water heat exchange, raising the water temperature and effectively preventing freezing.

3. Use Electric Heating for Treatment When the ambient temperature is around 0°C, consider installing electric heaters or other heat sources on the piping system or circulating water tank to raise the surface temperature of the closed cooling tower, thereby preventing freezing.

4. Install water-deflecting plates at the air inlets of the cooling tower. On the tower wall adjacent to the air inlet, a significant amount of water flows downward along the wall and eventually freezes at the inlet area. To prevent this from happening, install water-deflecting plates on the inner side of the tower wall at an angle of 30 to 45 degrees, directing the water flowing down the wall back into the pool—thus avoiding ice formation on the tower wall near the air inlet.

 5. Hang wind shields at the air inlets of the cooling tower. During winter operation, installing these shields at the cooling tower’s air inlets helps prevent cold air from entering the tower, thereby protecting the water flow in this area from being exposed to external cold air. This maintains the temperature at the air inlets and effectively eliminates ice formation around the inlet openings. The installation and removal of the wind shields should be adjusted promptly based on local climate conditions, wind patterns and directions, as well as the specific ice buildup inside the cooling tower—allowing for flexibility such as installing them only on the windward half-circle, focusing solely on the upper section, or even covering the entire tower structure.

The air temperature at the water-spraying device should be maintained above 0°C, while the pool water temperature should remain between 10°C and 15°C—or higher—and large-scale ice formation should be avoided. According to the production process of the windbreak panels, their height typically does not exceed 3 meters, and their width is limited to no more than 0.88 meters. Additionally, the structure of the windbreak panels should facilitate both mechanical and manual installation as well as easy disassembly.

 6. Implementation of the "Anti-Ice Ring" The so-called "anti-ice ring" refers to a circular anti-freeze spray pipe installed around the perimeter of the cooling tower's water distribution system, positioned just above the inner side of the air inlet. Several smaller branch pipes are evenly connected beneath this main pipe, spraying hot water into the tower interior. This creates a curtain of hot water at the cooling tower's air inlets, effectively blocking cold air from entering while simultaneously slicing through any ice curtains or icicles forming at the inlets, thus preventing them from growing larger. The hot water used in the "anti-ice ring" is supplied directly from the circulating water supply line.

The specific approach is:

Two antifreeze pipes are branched off from the circulating water supply line, running as looped pipes along the inner walls of the tower in opposite directions. Each pipe is responsible for delivering half of the tower's total spray water volume, and the pipes are sealed at their junction points. Meanwhile, several smaller pipes extend downward from the lower end of the "ice-prevention ring," evenly distributed around the perimeter of the tower to form the spray lines. Typically, these spray lines consist of segmented, arc-shaped tubes that remain disconnected from one another. The water flow rate within the "ice-prevention ring" is precisely controlled by a temperature-controlled valve installed atop the pipe. The antifreeze principle behind the "ice-prevention ring" is straightforward: the hot water sprayed from the ring preheats the air entering the cooling tower, thereby altering the atmospheric conditions around the water-distribution fill media. Additionally, the hot-water curtain created by the "ice-prevention ring" at the tower's air intake significantly increases the resistance to airflow moving from outside into the tower. This reduced air intake effectively limits the amount of cold air infiltrating the system, preventing ice formation at the intake and improving insulation conditions at this critical point—thus avoiding ice buildup altogether.

 7. When there are several cooling towers, some of them can be shut down to concentrate the heat load onto fewer towers, thereby increasing the thermal load on those specific towers. Alternatively, the fans can be stopped altogether to raise the temperature of the cooled water, preventing ice formation.

 8. Reversing the Fans: In mechanical ventilation cooling towers, in addition to using the methods mentioned above to prevent freezing, you can also reverse the fans. By periodically exhausting warm air from the tower’s air inlets, this helps avoid ice formation at the inlets—another effective approach. However, the fan-reversal duration should generally be kept short, ideally no longer than 30 minutes per session, to prevent potential damage to the fans and ensure optimal cooling performance.

 9. Adjust the operation mode of the anti-icing system promptly.