Title

Prevention and control of marine biofouling in power plant condensers

Date of Award

1990

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Mechanical Engineering

First Committee Member

Subrata Sengupta, Committee Chair

Abstract

Marine biofouling represents a major problem in industrial heat rejection systems such as cooling towers and condensers, and is of concern to the power utilities and the process industry. This phenomenon leads ultimately to loss of equipment heat transfer efficiency due to maintenance and replacement. The major cost is diminished equipment performance which results in more fuel usage. This investigation evaluated three different methods of prevention and control of marine biofouling in shell and tube heat exchangers.An experimental test facility was designed and constructed to conduct several series of tests to better understand the process of biofilm development. The experimental setup was made of two prototype shell and tube heat exchangers operating in parallel, with 7 tubes per shell. The research program consisted of six different tests. One preliminary test was used as a reference test. Three targeted chlorination tests covered the effects of variation in chlorine dosage, duration and frequency on biofilm formation. A velocity test studied the effects of wall shear on biofilm growth, heat transfer and fluid resistance. A final test studied the effects of very low concentrations of copper and chlorine used simultaneously as biocides. In this last study, both ions were produced by electrolysis of seawater using electrolytic cells designed for this purpose.The tests employed temperature, velocity and pressure readings to calculate the heat transfer resistance and friction factor as indicators of biofilm growth. The test rig operated as a fully automated fouling monitor. A data acquisition system consisting of a data logger and a personal computer was configured to collect and process information. Experimental reduction and further statistical analysis was completed by using a one-way analysis of variance (ANOVA).A computer model for prediction of biofouling rates was developed. This model is a modification to the Kern-Seaton equation. Statistical analysis was done to validate the model predictions. In general, the correlation coefficients and the standard errors indicate that the shape of the predicted curves agreed fairly well with measured experimental data. After validation of data, this model could be used with a test facility running parallel to a power plant stream to determine what levels of biofouling are expected and to decide which scenarios are suitable for maintaining cleanliness.The effectiveness of the different control methods employed was with visual and in-situ non-destructive biomass deposit analysis. The research was conducted at the Biofouling Laboratory facilities of the department of Mechanical Engineering located at the Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, in Virginia Key, Florida.

Keywords

Engineering, Marine and Ocean; Engineering, Mechanical

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9032056