TECHNICAL AND ECONOMIC-FEASIBILITY OF ULTRA-HIGH LIME TREATMENT OF RECYCLED COOLING WATER

A set of experiments was conducted to evaluate the technical and economic feasibility of the ultra-high lime process for treating recycled cooling water. These experiments used a bench-scale, continuous-flow reactor system with automatic control of reactor pH and flow. Sixty-two experiments were conducted over a range of values for pH (pH 10.9 to pH 12.1), temperature (25, 35, and 45C), hydraulic retention time (2 to 64 minutes), and solids retention time (2 to 425 minutes). Good silica removal was observed at hydraulic and solids retention times below those typically employed in conventional lime softeners. The solids produced in the ultra-high lime process had settling characteristics similar to those found in conventional softeners. An economic comparison of the ultra-high lime process and conventional lime softening was performed using a cooling system simulation model and cost equations for water treatment processes. This analysis showed that the ultra-high lime process applied in the combined treatment configuration was more economical than conventional lime softening in the combined, sidestream, and makeup configurations. The economic advantage of the ultra-high lime process increased as the degree of recycle increased and as the concentration of scalants in the makeup water increased.

TECHNICAL AND ECONOMIC-FEASIBILITY OF ULTRA-HIGH LIME TREATMENT OF RECYCLED COOLING WATER Academic Article