Masters Theses

Date of Award

12-1990

Degree Type

Thesis

Degree Name

Master of Science

Major

Environmental Engineering

Major Professor

R. Bruce Robinson

Committee Members

Gregory Reed, Bruce Tschantz

Abstract

Conventional treatment to reduce scaling and corrosion in cooling water systems is based on chemical treatment. Corrosion inhibition is usually accomplished by the addition of inorganic phosphate or zinc. Inorganic phosphate and organic compounds are normally used to control scale build-up. However, the use of chemicals for these purposes may present problems in that some of them are classified as hazardous substances which requires special handling, storage, and paper work. Besides this, chemicals are costly and are very labor intensive. To provide a solution to these problems, periodically a non-chemical treatment device is introduced that the manufacturer claims will reduce scale and/or corrosion without all the problems associated with chemical treatment. The purpose of this research was to determine if such a device, developed by Aqua Dynamics Corporation, did produce a positive effect on the scaling and corrosion rates in the cooling water. The Aqua Dynamics device allegedly alters the zeta potential of the particles present in the cooling water by emitting a radio frequency (R/F). Zeta potential is a measure of the repulsive force between colloidal particles. The theory behind the device is that by altering the zeta potential, particles will aggregate more easily into light chemical floe that are easily removed by flushing or other means, and therefore will be unable to produce scale. In order to evaluate the non-chemical device effectively, three similar cooling systems, located at different sites, were examined at the same time. One system continued the chemical treatment currently being used to treat the cooling water. A second cooling system was only treated with a biocide, and the third cooling system had the non-chemical treatment device installed in it. To evaluate the effects of the three systems on the cooling water, several water quality tests were performed. These tests were pH, conductivity, hardness, chloride concentration, and alkalinity. Zeta potential was measured since the non-chemical device was supposed to alter this. Also the particle size distribution was determined to see if there were any changes in particle/floc growth. Additionally, the corrosion potential of each system was tested, and X-ray diffraction and energy dispersive analysis (EDS) tests were made on any products formed. Side by side comparison of the water quality data indicated no discernible differences. Analysis of the zeta potential data also indicated no discernible differences between the effects of the non-chemical device and the other two systems. Examination of the particle size distribution showed no difference in the flocculating tendency of the particles. The corrosion data indicated that the non-chemical treated water had substantially higher corrosion and scale build-up rates than the other cooling systems. However, the EDS analysis of the scale indicated that iron was the predominant compound present, indicating corrosion, not scale formation, was occurring. It is possible that the Aqua Dynamics device caused the dissolution of any existing scale, and also prevented the formation of extensive new scale, and thus contributed to the increased corrosion rate. It was a conclusion of this research that the Aqua Dynamics R/F device had little effect on the chemistry of the cooling system, except to substantially increase the corrosion rate and formation of corrosion products.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS