CASE STUDIES

NASA Cooling Tower Ozone Treatment

Kennedy Space Center, Florida
June 2000

Agrimond^SM was contracted by NASA to review ozone treatment systems employed to treat two large cooling towers supporting the Vehicle Assembly Building (VAB) and O&C Facility at Kennedy Space Center. The first objective was to review their existing practices for two cooling tower systems that were 10,000 and 12,050 tons. The second objective was to analyze the economic and performance feasibility of multiple solutions. The final objective was to design a treatment system for the cooling tower that would deliver the required results.

Problem: Existing ozone treatment systems as designed, were not working, resulting in twice re-tubing condensers. Low cycles of concentration increased the tower blow-down and served to hydraulically overload the permitted waste treatment facility resulting in noncompliance. The pre-existing ozone generation equipment was universally deemed unreliable. There was no mass transfer of ozone gas into solution. Additionally, the original ozone system was installed under the beneficial premise that using ozone required no blow-down. NASA learned after two years of operation that the condenser tubes were completely scaled with reported cycles of concentration exceeding 80 at times. Both of these factors are the result of severe design problems.

Requirement: The Phase-One Study was necessary to identify the specific deficiencies associated with their existing ozone water treatment plant and to suggest solutions. The Phase-Two Study included an economic and feasibility analysis to address cooling tower water treatment issues. This study addressed the following alternatives: A) Utilizing the existing ozone system for the next 30 years, B) Utilizing conventional chemical treatment, and C) Upgrading the existing ozone water treatment system to improve its effectiveness. The merits and concerns of utilizing each of the alternatives were individually addressed. The Phase-Three Study was to provide engineered designs and drawings for the best alternative. The overwhelming best alternative was to upgrade their existing ozone system and resolve issues identified as deficiencies in the Phase One Study.

Solution: Ozone applications developed by the R&D staff of AgrimondSM with regard to the mass transfer of ozone gas into water were incorporated into the overall design of the cooling tower treatment. Taking into account the size of the towers, Agrimond^SM designed a system that introduced ozone to multiple feed points to increase the concentration of the ozone in the treating water. The concept was to incorporate the use of a large contact column for mass transfer however; the existing expanse of piping was used in lieu of the contactor. Modifications to the existing piping were made in substitution of the contact-tank. The Multiple feed points take advantage of areas that promote solubility of a gas into solution.

Results: Agrimond^SM applied a new and innovative approach and produced a successful design that has been successfully operating for over 4 years. Prior to going on-line with the newly designed ozone system, the VAB tower was operating with chemicals at about 4 cycles of concentration. They now operate between 10 and 12 cycles of concentration, which results in compliant operation of the waste treatment facility, clean condenser tubes, and reliable ozone treatment without supplemental chemical dosing.

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