The report describes tests to demonstrate the feasibility of using a vertical-tube, falling-film, vapor-compression evaporator to concentrate waste water from a flue gas desulfurization (FGD) process. Tests showed that waste water from the Chiyoda FGD process can be concentrated up to 140 times and with recovery of more than 99% of the waste stream as high quality water (< 10 ppm TDS). Two series of tests were conducted: one with a 25 gpd bench model evaporator; the other with a 6000 gpd pilot size evaporator. Process conditions were identified and verified for scale free operation. Heat transfer coefficients of 500-750 Btu/hr-sq ft-degrees F were consistently achieved throughout the tests. A conceptual design and economic study of a full size treatment facility showed that capital costs will range from $5110 to $8706/1000 gpd of waste water processed, depending on system capacity. Operating costs will vary from $2.46 to $3.60/1000 gal. of waste water processed, depending on system capacity and waste water composition. Some credit can be taken for savings on boiler makeup water treatment costs by providing the high quality distillate to that process.

Prepared by Resources Conservation Company, Renton, Wash., for U.S. Environmental Protection Agency, Office of Research and Development, under contract no. 68-02-2171, program element no. EHE624A. Issued Sept. 1977. Includes bibliographical references.