Cooling Water Technology for Fresh Water

This case study highlights how 3D TRASAR Cooling Water Technology helped troubleshoot system low conductivity and improved cycle of concentration which saved more than 144,000 m3 of precious fresh water for a global Air Separation Company in India.

A global air separation company has installed capacity of 2,550 TPD plant to supply the Oxygen, Nitrogen and Argon gas to a major local steel manufacturer.

The cooling tower has a system volume of 1,960 m3 with a recirculating rate of 6,075 m3/hour, while the cooling water is used mainly to cool the compressed air coming from the MAC (Main Air Compressor) and BAC (Booster Air Compressor), respectively.

The plant was commissioned in January 2012, and it was observed during the start-up that the residual product ppm level was not well maintained in the specific boundary limit.

Nalco has conducted an onsite investigation to find the plausible causes for such an anomaly. The COC (Cycle of Concentration) of the system was designed to operate at 4 to 5 cycles while the system prevented the COC from increasing above a maximum value of 3 (Average 2.8 cycles).

Solutions
A 3D TRASAR system was installed for real time online data logging, monitoring, and control capabilities in order to understand system conditions and fluctuations 24/7 and adjust the water treatment regime accordingly. In addition, Nalco 360 Service for system performance monitoring also provides 24/7 monitoring, alarm notification, and timely rectification by trained a group of Nalco experts.

Low Cycle Reflection on Nalco’s 3D TRASAR Data Analysis: The 3D TRASAR data analysis revealed a decreasing conductivity value trend. The chemical reserve could not be maintained because of water losses. See Figure 2.

Low Conductivity Alarm: Low conductivity alarms were sent through web connectivity (monitored by the Nalco 360 Service team) to the Nalco team and triggered further site investigation in identifying the source of water losses. The water losses occurred through overflow or through Side Stream Filter (SSF) backwashing with the following identified root causes:
• SSF backwash line was taken from the cooling tower
• Backwash frequency was timer based and backwash interval was automated at a frequency of 24 hours
• Overflow line was lower in cell number 2 of cooling tower compared to the rest of the overflow lines of the other three cells.

3D TRASAR technology was logging other low conductivity incident alarms, which were sent out to the Nalco representative to ensure the system was brought back to normal conditions in the shortest possible time.

A few events are given for reference in Table 1 above.

Nalco has recommended the following modifications to address the water losses:

• A staggering of the timer-based auto backwashing system was extended from 24 hours to 40 hours without any effect on asset reliability
• The overflow line required to be modified as suggested by Nalco

Results
The COC has increased from average 2.8 cycles to 4 cycles, saving more than 140,000 m3 of precious fresh water per year, reducing annual total cost of operation by USD 20,800. Figure 3 shows the upwards trend of the COC value after 3D TRASAR technology identification of water losses and implementation of recommended improvement plan to rectify the system condition.

Conclusion
Nalco 3D TRASAR Technology coupled with Nalco 360 Service, and on-site expertise helped the client identify root cause of water losses to achieve the desired system cycle operating condition and saved on precious fresh water.