Determining boiler-water makeup

In boiler operations, it is desirable to determine blowdown--and, thus, the feedwater`s concentration cycles--because it enables operators to calculate the theoretical concentrations of iron, copper or dispersant in the system. These calculations are important for maintaining boiler cleanliness. In practice, however, it isn`t always feasible to determine blowdown. For example, if the steam, feedwater and blowdown flows are not measured in a system, or if the measurements are not accurate, the blowdown and feedwater concentration cycles cannot be accurately determined. Also, if demineralized makeup water with very-low silica concentrations is mixed with essentially silica-free condensate, the ratio of silica in the boiler water to the silica in the feedwater may not yield accurate values for the concentration cycle. This method for calculating concentration cycles is accurate to within 5%, when the accuracy of the parameters measured are within the following limits: steam flow (2%); phosphate, residual (5%); micro calcium (50%); micro iron (25%); and phosphate, feed (10%).