Industrial steam plants and combined steam and power plants, also known as cogeneration plants, typically use boilers to provide high quality steam and electricity. As the heart of the plant, these boilers are vital for efficient energy creation. If impurities enter the boiler feedwater or corrosion occurs within the boiler, equipment can be damaged, plants can experience unplanned shutdowns and energy creation can be extremely inefficient. Limiting impurities and corrosion in boiler systems to maximise boiler output and prevent these challenges is essential.
Chemical reducing agents can reduce dissolved oxygen levels to prevent or minimise corrosion within boilers and turbines. These materials include chemical scavengers or corrosion inhibitors that are injected into the boiler or boiler feedwater. They are typically delivered via injection equipment, such as atomisers or sample tubes.
Ferric Chloride
For example, in steam generators typically operating at 600 psi or below, uncatalyzed or catalyzed sodium sulfite (Na2SO3) is a non-volatile deaerator that adds inorganic dissolved solids to the feedwater.
In addition, corrosion and cooling/heating equipment can help to maintain pure water with few material contaminants.
Industrial boiler water treatment helps to protect the low pressure steam generators commonly found in thermal power plants. A variety of reagents can be used to treat boiler water, including phosphate/polymer combinations, polymers alone and (rarely) chelating agents.
Ferric chloride is mainly used as water treatment agent. Ferric chloride is also known as iron trichloride, Iron(III) chloride, etc. Ferric chloride is a covalent inorganic compound with the chemical formula FeCl3. It is easily soluble in water and has strong water absorption, which can absorb moisture in the air and deliquescence.
Trisodium phosphate (Na3PO4), also known as TSP, is a common boiler water conditioning chemical that establishes moderately alkaline conditions in the boiler to minimise corrosion and reduce the occurrence of hardness-intruding scaling. Phosphate treatment procedures also use a mixture of trisodium phosphate and monosodium phosphate to control pH.
Carbohydrazide
In addition to phosphate treatment, sludge conditioners using water soluble polymers are recommended to help maintain solids in suspension through a combination of dispersion, crystal modification and chelation. Sludge conditioners can also help to keep iron particles in suspension for subsequent discharge.
Chelating agents, such as ethylenediaminetetraacetic acid (EDTA), can sometimes be used to bind to metals to keep them in suspension. However, chelating agents can only be used for well degassed feed water, good pretreatment control and low feed water iron concentrations.
Carbohydraizde (Hydrazine Carbonate, H2NNHCONHNn2, CHZ for short) is an important chemical raw material. It has a wide range of uses in industry. It can be used as a deoxidizer for boiler water and a passivator for metal surfaces in water treatment. It can also be used as a deoxidizer for boiler water and metal surface passivation.
The choice of the appropriate treatment depends on a number of factors including boiler design and pressure, the effectiveness and reliability of the make-up water treatment system, and the risk of impurity ingress and iron oxide entrainment from condensate return. These factors must be carefully assessed for each plant, as standardised methods can lead to serious problems.
Once a treatment has been selected, monitoring the chemical reaction is the best way to ensure that the treatment is carried out properly. A Soda Water Analysis System (SWAS) consisting of properly selected sampling and conditioning equipment and in-line instrumentation is key to controlling and monitoring the treatment programme of the system.
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