Cooling Tower Ozone Installation
Ethanol Plant Cooling Tower
We have recently completed an installation of a 300 g/hr ozone generation system into a large cooling tower at an ethanol plant. The use of ozone will replace chlorine and bi-sulfate chemical additions while eliminating the need to transport, store, and purchase bulk chemicals.
Reason for Ozone Use
- Chemical costs at this plant are very high as the cooling tower is a major consumer of chlorine and bi-sulfate chemicals.
- Blow down water sent to the waste stream carries a high level of chemicals and minerals from this cooling tower. This is undesirable as the plant must treat this water prior to discharge.
- New regulations on hazardous chemicals are forcing extra labor costs by staffing the facility during non operational hours.
Ozone Solutions Used
We supplied a 300 g/hr ozone generation system to implement ozone as a biocide for this application. The ozone system produces ozone from a 300 g/hr water cooled ozone generator. This will produce 300 g/hr of ozone from 40 LPM of oxygen at 9% by weight from oxygen. Oxygen is provided by an Air-Sep AS-D oxygen concentrator using compressed air to provide 40 LPM of oxygen feed gas for the ozone generator. The AS-D is fed with compressed air supplied by the customer's current compressed air systems.
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Ozone is injected directly into a water recirculation line using a custom ozone injection point.
This image shows the ozone gas plumbed into this injection point. The injection point will diffuse the ozone into the pipe via micro bubbles. The pipe recirculates roughly 300 gpm of water, which travels 150 yards and then discharges into the cooling tower basin. This pipe distance allows the ozone to achieve excellent mass transfer efficiency.
Results
Currently this ozone system is rented by the customer with the option to purchase at any time. The rental process offers great flexibility for the customer along with cost savings over the previous chemical additions.
- After ozone use, bacterial counts dropped to non detectable levels and stayed non detectable for every test taken.
- ORP levels used for control dropped from previous levels of 500 - 600 with chemical, to 300 with ozone, while still maintaining non detectable bacteria levels. These decreased levels will likely result in lower corrosion rates of the cooling tower than with the previous chemical application.
- COD levels in the water dropped to 0-5 ppm.
- Overall visual clarity of the water improved.
- Effluent blow down water contains lower mineral levels and no added chemicals.
