GCM Water Treatment Technologies provides a wide range of chemicals for a variety of applications. Below are the chemicals groups classified by functionality.
Corrosion Inhibitors
Corrosion leads to failure of critical parts of boiler systems, deposition of corrosion products in critical heat exchange areas, and overall efficiency loss. Corrosion inhibitors are chemicals applied to protect the metals surface from corrosion by creating a thin protective layer on the metal. There are different kinds of corrosion inhibitors and are classified by how they prevent or inhibit corrosion.
Passivators such as chromate, nitrite, nitrate are called oxidising anions, phosphate and molybdate are called non-oxidising anions. These inhibit corrosion by shifting the corrosion potential forcing the metal surface into a passive state. Cathodic inhibitors such as calcium, zinc, or magnesium protect the metal by forming oxide layers on the metal surface. Organic inhibitors are adsorbed onto the metal surface forming a hydrophobic film that prevents corrosion.
Precipitation inducing inhibitors are compounds that cause the formation of precipitates on the surface of the metal, thereby providing a protective film.
The most common inhibitors of this category are silicates and phosphates. Volatile Corrosion Inhibitors are compounds transported in a closed environment to the site of corrosion by volatilisation from a source. Examples are morpholine and hydrazine and volatile solids such as salts of dicyclohexylamine, cyclohexylamine and hexamethylene-amine. On contact with the metal surface, the vapour of these salts condenses and is hydrolysed by moist environment, to liberate protective ions.
Scale inhibitors
Scale is the deposit that forms on surfaces of heat exchangers when the solubility of the dissolved salts has been exceeded as the temperature increases. Some examples of scale are calcium and magnesium carbonates, sulphates, and silicate. Scale inhibitors are negatively charged polymers which attach themselves to the crystal structure of the scale disrupting the formation of the scale. The scale then remains in suspension.
Some of the examples of scale inhibitors are phosphate esters, phosphoric acid and solutions of low molecular weight polyacrylic acid.
Disinfectants
These are chemicals used to kill unwanted micro-organisms in water. There are different types of disinfectants namely:
Chlorine
Chlorine kills bacteria and viruses by breaking down the chemical bonds in their molecules. However, the effectiveness of chlorine as a disinfectant is depended on pH. The most effective pH range for chlorine is between 5.5 – 7.5 above which it is ineffective. When chlorine enters water, it forms hypochlorous acid which is an electrically neutral. Because the molecule of pathogens is negatively charged, it can only be penetrated by the neutral hypochlorous acid. However, chlorine reacts with ammonia, organics in water which forms chloramines and other compounds before free chlorine is available for disinfection.
Chlorine dioxide disinfection
ClO2 is used principally as a primary disinfectant for surface waters with odour and taste problems. It is an effective biocide at concentrations as low as 0.1 ppm and over a wide pH range. ClO2 penetrates the bacterial cell wall and reacts with vital amino acids in the cytoplasm of the cell to kill the organisms. The by-product of this reaction is chlorite. Chlorine dioxide disinfects according to the same principle as chlorine, however, as opposed to chlorine, chlorine dioxide has no harmful effects on human health and is easy to apply and manage.
Hypochlorite disinfection
Hypochlorite is applied in the same way as chlorine dioxide and chlorine. Hypo chlorination is a disinfection method that is not used widely anymore, since an environmental agency proved that the Hypochlorite for disinfection in water was the cause of bromate consistence in water.
Algaecides
These are the chemicals applied to kill algae.
Antifoams
Antifoam blends contain oils combined with small amounts of silica which break down foam due to two of silicone properties namely, incompatibility with aqueous systems and ease of spreading. Antifoam compounds are available either as powder or as an emulsion of the pure product – polydimethylsiloxane. The antifoams are chemically inert and do not react with the medium that is defoamed. They are odourless, tasteless, non-volatile, non-toxic and they do not corrode materials.
Boiler water chemicals
GCM Water supplies chemicals for boiler treatment for the following applications:
Coagulants
High valence positive ions such as aluminium and iron are preferred as either aluminium sulphate or ferric chloride. Coagulation is very dependent on the doses of coagulants, the pH and colloid concentrations. To adjust pH levels Ca(OH)2 is applied as co-flocculent. Doses usually vary between 10 and 90 mg Fe3+/ L, but when salts are present a higher dose needs to be applied.
Flocculants
To promote the formation of flocs in water that contains suspended solids polymer flocculants (polyelectrolytes) are applied to promote bonds formation between particles. These polymers have a very specific effect, dependent upon their charges, their molar weight and their molecular degree of ramification. The polymers are water-soluble and their molar weight varies between 105 and 106 g/ mol. There can be several charges on one flocculent. There are cationic polymers, based on nitrogen, anionic polymers, based on carboxylate ions and polyampholytes, which carry both positive and negative charges.
Oxygen scavengers
Oxygen scavenging refers to the removal of oxygen from the water to prevent corrosion.
Oxygen scavengers include both volatile products, such as hydrazine (N2H4) or other organic products like carbohydrazine, hydroquinone, diethylhydroxyethanol, methylethylketoxime, but also non-volatile salts, such as sodium sulphite (Na2SO3).