Beyond Corrosion Control: Sustainable Filming Amine Technology Applications for Cooling Water Systems

A Distributor’s Perspective – Mary Wolter Glass, Mexel USA, LLC

Introduction

Innovative filming amine blends offer a new paradigm in cooling water treatment. They are the leading edge for cooling towers and once-through systems to control corrosion, biofouling, and scaling with one biodegradable emulsion that can be used in the environment. Extensive laboratory research, supported by almost two decades of commercial use around the world, has demonstrated the efficacy. With increasing regulation of chemical discharges to the environment, successful adoption of technologies that meet higher standards will fall on AWT members. This paper will address the science behind filming amines and their benefits. Then, the field experience and treatment programs from companies that have used and rigorously tested the amines will be shared. Using filming amines in cooling water systems provides a treatment method that is different from traditional chemicals which treat the entire water column.

Some Filming Amine History

Filming amines have been used for decades, particularly in boiler condensate systems, to control corrosion. The amine group of the molecule is hydrophilic so it will attach to wetted surfaces, while the “tail” is hydrophobic providing protection of the metal surfaces from corrosive condensates. Amines have been developed in a number of formulations over the years. Octadecylamine (CH3(CH2)16CH2NH2) has been the most widely applied amine salt in the past. Although amines have been successfully used with volatile oxygen scavengers in previously corroded systems, they are most effective in preventing corrosion in new systems. Historically, filming amine programs have required careful management to avoid a variety of problems including clogging and blockage of traps.1

Dosing programs for filming amines in condensate systems were based on the internal surface area of the system rather than system volume. These programs work have worked well in feedwater that was highly alkaline or had air in-leakage because they did not attempt to neutralize the CO2. In water with a pH above 8.0 or below 6.5, previous amine regimes sometimes required additional chemicals to condition the water for the amines to be effective. Treatment programs typically started with low levels of amines, gradually increasing to desired residual concentrations that are effective without potential adverse impacts, such as developing sticky masses (“gunk balls”) that can clog the system.2,3

Amine programs and products have evolved over time and a large number are now available for condensate treatment and other fouling problems. Cocoaalkylamine and diaminepropane have been deployed in products designed for open and closed cooling water systems to control corrosion and as a molluscicide.4

As the newest innovative filming amine blends have continued to evolve, they now offer a new paradigm beyond boiler condensate treatment to new applications in cooling water treatment with a strong focus on prevention and low impact. Unlike single purpose amine blends, some are blends that address multiple problems.

Multipurpose filming amine applications to cooling water – An Example

Cooling water treatment programs for cooling towers and once-through applications are designed to address three common forms of fouling that decrease the efficiency of heat transfer. Depending on the site-specific requirements, traditional chemical treatment programs have included chemicals to control corrosion, prevent or remove silt and/or mineral deposits, and control or remediate biological growth. Corrosion inhibitors include filming and neutralizing amines, metal-based inhibitors (e.g. molybdates and salts of zinc) and nonmetal-based inhibitors (e.g. inorganic phosphates, phosphonates, aromatic azoles, nitrates, etc.).5 Control of deposits from various constituents found in the cooling water is often achieved through the use of polyphosphates, organophosphorus compounds such as phosphonates, chelants, polymeric agents and other chemicals.6 Control and remediation of bio-fouling is also a critical concern in a cooling water treatment program due to its pervasive nature and significant effect on the efficiency of heat transfer. A wide variety of oxidizing and non-oxidizing biocides are in use including the popular chlorine and bromine. The frequency of application and concentrations of chemicals used for treatment vary widely, depending on the site-specific problems, equipment configuration, operating parameters and regulatory requirements.

New specialty blends of filming amines offer single products that can address all three major areas of concern for fouling of cooling water systems. One product, Mexel 432/0, exemplifies how this is accomplished and the potential benefits for water treatment professionals. The filming amine emulsion provides a molecular coating to the wetted internal surfaces of the water circuit in a manner similar to filming amines in condensate systems. In doing so it prevents three kinds of fouling, keeping the cooling systems cleanliness consistently high, and maintaining efficient heat transfer. This particular product can be employed in fresh, salt and reclaimed water, and is most effective in new or newly cleaned systems. Some remedial effect on existing systems has occurred over time as shown in the figure below. This emulsion has been registered with the U.S. Environmental Protection Agency as a pesticide to control biofouling in cooling water systems – open and recirculating.

The product is injected into the cooling water using a chemical pump with automated control of the dosing rate and timing. Because the emulsion replaces several chemicals, is in a concentrated form, and requires only small quantities, the equipment and space used is minimized. Biweekly or monthly monitoring includes visual inspection, chemical residual measurements, feed calibration, and adjustments as needed. Metrics monitored include conductivity, pump calibration, feed time, corrosion, pH, and total bacteria counts.

Laboratory testing has determined that this emulsion is effective in forming films on all common cooling and heating equipment internal surfaces including metals, plastics, weldings and concrete. Extensive testing has also determined that the emulsion has no detectable adverse effect on materials used in typical cooling water systems. This specific amine emulsion is not volatile and does not burn or explode.

Since 2007, an amine blend, MexClear, has been in commercial use in more than 30 chiller/cooling tower applications in the Mid-Atlantic region preventing corrosion and scaling significantly lowering cleaning requirements. I

Other operating experience over two decades of commercial use around the world, has further confirmed the efficacy of filming amines. In a large cooling tower at a nuclear plant in France, the emulsion reduced biofouling by factors of 8 to 10 by removing the habitat that fostered biological growth. In Poland, two cooling towers at a fertilizer factor used the product to stop pitting and new perforations to heat exchangers by reducing corrosion to less than 0.1 mm/yr. In addition, it stabilized the water pH at 8.6 and reduced sediment by 50% while acting as an effective anti-fouling agent.

New filming amine emulsions vary significantly in cost but, based on overall program costs, are comparable to traditional programs on an annual basis. Secondary financial benefits from the ability to maintain cleanliness of the system can also accrue. These include improved heat transfer efficiencies that can be significant in chiller systems, along with reduced maintenance and annual cleaning costs. Estimates of annual savings from fully effective chiller water treatment for a 300 ton chiller range from $13,000 to $20,000.

Why filming amines are beneficial technology

Environmental performance and safety have always been important components of any water treatment program. Increasingly, customers are specifying them in their designs and procurement planning. Water treatment specialists must respond with sustainable water treatment programs that are equally effective and cost competitive. New alternative treatment programs, such as specialized filming amines, are now being considered for potential positive impact on performance.

Filming amines can reduce the total chemical load in surface waters by 1) providing a single chemical that replaces the use of multiple chemicals to treat common fouling problems, and 2) providing an alternative to some traditional chemicals that have been identified as problematic.

The method of action of the amine emulsion is different from most conventional treatments. They are intended to prevent and control fouling from progressing. This film prevents biofouling from gaining a foothold that can lead to corrosion, deposits, and poor heat transfer. It also helps prevent the build-up of layers of fouling that are hard to penetrate. When these problems are prevented, the amount of chemicals required and introduced to the environment for routine treatment, remedial chemical treatment, and other special maintenance (e.g. acid tube cleaning) is substantially reduced.

Because of the product’s filming characteristics it is readily adsorbed onto organic material in the cooling water and rapidly disappears from the water column. Further, extensive laboratory and field testing has shown no adverse impact of filming amine products when used as directed. In addition, because the amine films are chemically bonded to the interior surfaces, continuous treatment is not required. Instead, short daily doses of extremely small quantities reduce the potential for chemical exposures.

The frequency of application and concentrations of chemicals used for cooling water treatment can vary widely, depending on the plant-specific requirements, from occasional, concentrated “slug” dosing for remediation to continuous low level dosing for prevention and control. Since the mid-1970’s, extensive research studies conducted by the EPA have recognized the adverse impacts of chlorine on aquatic species (Hergott, et al., 1978). One study found that even routine, short term exposure of larval and juvenile fish to short-term exposure to chlorine levels of <0.2 ppm produce “significant biological effect” (Gentile, et al., 1976). The same study identifies complete growth inhibition at 0.3 ppm after only 5 minutes in some algal species. Many large cooling water systems now have a limit on chlorine use to 0.2 ppm for no more than two hours per day, but some states (e.g. Maryland) are currently seeking further reductions in discharges, or de-chlorination before discharge. Chlorine gas is toxic to mammals by inhalation; very hazardous to workers; has the potential for significant community hazards in the event of a release; and can vaporize creating human health and explosion dangers that are difficult to control. Chlorine based pesticides are also physically unstable and very corrosive to many materials. The breakdown of chlorine based compounds can form a variety of hazardous chemicals, including haloacetic acids, trihalomethanes, bromamines, and chloramines.

Other chemicals used in cooling water applications including biocides, corrosion and scale inhibitors, and water conditioners can have additional adverse environmental effects.

An AWT Member’s Experience – David Boyle, Chemstar

International Chemstar Incorporated, trading as Chemstar, is a regional water treatment company and AWT member. Chemstar first became aware of filming amine technology for cooling water when we lost a few accounts so that our customer could run a trial with this new technology.

When we found out the small amounts of the Mexel 432/0 that would be fed, only once daily, we predicted it would fail. But by the end of the first season the customer was so pleased with the results they expanded the number of sites to use this new treatment and we lost more business.

Adopting an “If you can’t beat them, join them!” attitude, we were able to start offering this filming amine emulsion to our own customers. We have evaluated the product’s performance and have tried to learn all of its limitations. We developed an economical feed system, adopted a lower cost test kit, and experimented with biocides that we can use in conjunction with the product.

We have been using this filming amine technology for 4 years. The products advantages over conventional water treatment have been well received by our customers and prospective customers. We’ve learned quite a bit from our experience in the field with alternative treatment regimens and are confident of its efficacy.

Applications

We currently use filming technology in cooling towers of in office buildings, medical centers, Federal and local government buildings. It is also used in cooling water for large air compressors that have bleed off that goes to outfalls that go to environmentally sensitive creeks and rivers. We also use an EPA Registered product filming amine emulsion in a once-through system to control Asiatic Clams. The largest once-through application is for reduction of Copper corrosion rates and therefore Copper discharges. Without treatment the Copper discharges were in violation of permitted limits. Azoles were used previously to lower the corrosion rates but were replaced with filming amine technology.

How this technology can be used in cooling water.

In cooling towers we determine or estimate the volume of the system. The required dose is dependent on the surface area in the system. The treatment protects the surfaces. This correlates to the volume. Water quality and cleanliness of the condenser water system are also factors on the demand for treatment.

Applications where space is a concern.

Another advantage that customers like is the small amount of space that is required for the feed system. Only a small amount of product is needed on site. Some customers that like the solid feed systems due to the small foot print in mechanical rooms. This technology offers the same advantages.

Business Perspective

There is no shortage of competition in the water treatment business. As there is more competition selling the same old technology the profit margins decrease. Smart water treatment companies try to differentiate themselves from their competition.

In a search for easier to use treatment programs, some water treatment companies have gone back to selling solids instead of liquids. It comes packaged in different ways and the feed methods vary. The cost of the feed systems can be expensive and troublesome. Some of the advantages of solids are lower shipping costs, easy to handle, no big storage tanks and a smaller footprint. At the end of the day, however, it is still the same treatment program chemistry that is normally offered.

Filming amine emulsions in cooling water work in a totally different way than standard cooling water treatment. Due to the low dosages and no detectable level of discharge, it is as close to not using “chemicals” as you can get without being a NCD (Non Chemical Device).

The “no chemicals” advantage of NCD is often used to replace standard water treatment accounts. There are a variety of disadvantages to NCD’s but one of the greatest is high capital equipment cost. Filming amine technology in cooling water offers the key advantages of both solid treatment and the NCD. Recent efforts to make this technology available to smaller water treatment companies created an opportunity to offer something new to your prospects. It gives the salesmen something new to talk about to the prospect.

Endnotes:
1. Ashland Chemical Company, Drew Industrial Division, 1994. Principles of Industrial Water Treatment, p. 230-231.
2. Nalco Company, 2009. The Nalco Water Handbook, Daniel J Flynn, Editor, Third Edition, p 13.19-13.20.
3. Deborah M. Bloom, “Advanced Amines Cut Condensate Erosion”, 2001. Power Magazine, July/Aug. 20001, Ondeo Nalco, Co.
4. Colin Frayne, CWT, Aquassurance, Inc. The Analyst, 2009. Association for Water Treatment, Volume 16, Number 4 p. 24-33.
5. Ashland, 1994, p. 13.19
6. Ashland, 1994, p 15.32

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