Case Study

Hydrated Lime Slurry for Water Treatment

Problem: A natural gas fired electrical power plant was using well water from deep water wells in Maricopa County, Arizona.  The well water was extremely hard and contained a substantial amount of silica.  Various methods of treating the water were not successful in meeting standards.  Dry hydrated lime was first used, followed by carbide lime, and then dolomitic lime slurry from an offsite source was tried.  All with major cost and/or quality and logistical drawbacks.

Solution: In 2006, Applied Specialties, Inc. and Bromatco were awarded a contract to manufacture high calcium hydrated lime slurry, on site, from quicklime with the first year estimated calcium oxide usage of 3,400 tons.  Magnesium chloride was used to offset the loss of magnesium from the dolomitic lime in the previous process.  This was the maiden voyage of what in now called the Lime-Save process.

A combination of additives was employed in the quicklime slaking process to produce a high solids, low viscosity, and non scaling hydrated lime slurry.  Brookfield viscosities of less than 800 cps were achieved with solids content as high as 45%.  Existing agitated tanks with 35 hp motors were replaced with new tanks with 5 hp motors.  Grit was removed through a basket strainer.  A 9 hp gasoline powered 3” trash pump was utilized to pump the slurry over 100 feet into a 16 foot high storage tank at a rate of 250 gallons per minute.

Water quality was improved to required standards of hardness and, with the magnesium being injected and controlled separately, silica was consistently reduced to below the minimum requirements.  No downtime due to inoperative equipment was experienced.

Best of all, the plant saved hundred thousand dollars a year in water treatment costs because of lower product costs and lower lime usage.  On average, less than 2,100 tons of quicklime per year was used compared to the expected 3,400 tons estimated in the first purchase order, a 38% savings.   The large dry hydrated lime and magnesium oxide silos and mixing equipment were no longer needed.  After 2 ½ years, no buildup on the inside of tanks or feed lines was observed.