BetzDearborn Introduces Major Breakthrough in Cooling Water Treatment
Dianodic Plus features several compounds, new to water treatment, that are immune to attack from halogens-in particular, the chlorine and bromine that are commonly used as biocides. It also comprises new biodispersants to improve biological control. The end result is higher performance for a cost comparable to existing Dianodic protection programs, or lower cost for equal performance. In addition, <%=company%> maintains that the program will allow plants to use less makeup water, discharge less blowdown, and run their systems at higher cycles, further lowering the overall costs of providing water treatment in a cooling system.
As explained by Gary Geiger, market development manager for <%=company%>, most cooling-water treatment programs operate at either near-neutral or alkaline pH. Both treatment approaches rely on inorganic phosphate for steel corrosion control and an organic azole (tolyltriazole, or TTA) to inhibit copper corrosion. Copper protection is important because as copper corrodes, soluble copper is released to the cooling water, and will plate out on steel surfaces, in turn causing pitting, corrosion and premature equipment failure there. Alkaline programs differ from near-neutral treatments in that they require an organic-phosphorus (phosphonate) scale inhibitor to prevent scaling by calcium carbonate. The most commonly used phosphonate is HEDP (hydroxyethylidene-diphosphonic acid).
Both TTA and HEDP are highly susceptible to degradation by free halogens, Cl and Br. "The most common problem in water treatment is today is the destruction of copper-corrosion and scale inhibitors by chlorine," says Geiger. Typically, operators must add extra TTA or HEDP to get the right level of protection, and if too much chlorine is added, must provide yet more TTA and HEDP. In some cases, chlorine feed is reduced to prevent excessive loss of treatment chemicals; this results in a loss of microbiological control.
To address this, <%=company%> has developed a proprietary azole, designated as HRA (halogen-resistant azole) and a calcium-carbonate scale inhibitor, AEC (alkyl epoxy carboxylate) for alkaline programs. The Dianodic Plus treatment programs include Continuum AEC for alkaline systems and Dianodic III for near-neutral pH operation. "The Dianodic Plus programs are the only halogen-stable cooling water treatments in the world, and Continuum AEC is the only treatment on the market that does not use a phosphonate scale inhibitor," says Geiger. Dianodic Plus also includes a nonoxidizing biocide, and a biosurfactant, that can be used in conjunction with halogens to provide biological growth control. The biosurfactant and biocide are brandnamed Spectrus BD and NX. "Spectrus has been shown to work synergistically with chlorine-you get better protection without using more chlorine," says Geiger.
For the end user, the new products allow a treatment system to run for more cycles before makeup water and chemicals must be added, which at one and the same time reduces blowdown (saving on sewer charges) and reduces makeup water (important for water-short regions) and cuts operating costs. Alternatively, a user could adjust the treatment program to use a lesser amount of chemicals while providing roughly comparable cycle times.
BetzDearborn has tested these new formulations for several years, and has found water demand to go down by as much as 20% in selected instances. It expects that most, if not all, of its current Dianodic II customers will switch in the next year or so, and that Dianodic Plus positions the company well against other water treatment vendors that are changing the chemistry of their biocides, rather than changing the copper-corrosion and scale-control agents. "Water treatment vendors have been in the unfortunate position of asking customers to replace chlorine or bromine biocides, which cost pennies per pound, with other chemicals that cost dollars per pound," says Geiger. "We believe that we have a better alternative."
By Nick Basta