The photo shows one of four 42 inch diameter Komax Systems 316L stainless steel static mixers installed at the Air Force Academy water treatment plant by the M. A. Mortenson Construction Organization. The Komax static mixers were selected to flash mix chemical additives into the water treatment plant’s 40 mgd water stream. Each chemical additive was introduced by a removable, side-mounted injector. Black and Veatch of Kansas City, Missouri were the consulting engineers.
Komax static mixers for additive mixing in both pipe and in-channel installations handle very small and large flow rates. This photo is of a 66 inch diameter Komax static mixer manufactured in fiberglass with multiple additive inlet ports for a 70 MGD application. Low pressure drop of Komax mixers translates into huge energy savings of over 90% when compared with mechanical mixing. No maintenance is required and service life exceeds 30 years. Pipeline mixers are available in FRP, PVC, stainless steel, carbon steel and lined mixers. Sizes of large pipeline mixers range up to 120″ in diameter.
Komax 96 inch diameter flanged carbon steel static mixer. Mixer has removable chemical injectors. The internal pipe walls and static mixing elements are epoxy coated.
A pair of these very large static mixers will be installed in the Scott Candler Water Filter Plant in Dekalb County, Georgia. Mixing sodium hypochlorite and hydrofluosilicic acid into the main filtered water stream.
Flow rate: 150 mgd.
Mixer pressure drop: Under 0.4 psi. @ 150 mgd.
Contractor: Archer Western
Engineers: Camp Dresser McKee
High concentrations of Sulfuric Acid (i.e., 93% or 98%) should not be injected directly into a 316 Stainless Steel Static Mixer. Within one to one and a half pipe diameters downstream of the injection point, concentration of the Sulfuric Acid is diluted to a very corrosive 50% to 30%
Continuous exposure of the 316 Stainless Steel mixing elements and mixer housing to this concentration of Sulfuric Acid will result in severe corrosion in just a few months.
Concentrated Sulfuric Acid has a specific gravity of 1.8 so it tends to migrate to the bottom of the mixer housing particularly at lower fluid velocities (i.e., less than 2 feet per second) which compounds the problem.
Pre-diluting concentrated Sulfuric Acid with additive water by means of a small diameter Kynar-lined static mixer will reduce the acid concentration down to a safe 10% or 5% level. This simple and inexpensive precaution extends the service life of the larger process stream Stainless Steel static mixer for years.
An additional advantage is the larger volume of diluted acid solution will provide equal flow rates through each discharge orifice of the acid injector resulting in improved acid distribution. When injecting one to two gallons per hour of concentrated Sulfuric Acid the resultant flow exiting the injector is only 2 to 4 ounces per minute. At this flow rate all of the acid will exit the first injector orifice precluding uniform dispersion of acid across the mixer housing diameter.