The phenomenon of scaling is a type of fouling typically observed in heat exchangers, steam generators and cooling systems. It is caused by the interaction of chemical species dissolved in the water to form inorganic salts. The most common species which bring about the formation of scales are calcium and sodium-based compounds. The solubility of […]
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In cooling towers, the heat is rejected by the partial evaporation of water as it flows through the unit. The evaporation will bring along a rapid concentration of the chemical species naturally dissolved in the water. The principal scale found in cooling towers is calcium carbonate which comes from the decomposition of calcium bicarbonate. This
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A sudden change in a fluid cross-section area provokes a dynamic condition in which water pressure drops sharply below its boiling point and produces instant vaporization. Since this process is adiabatic, there is no exchange of heat with its surroundings, therefore, the total enthalpy remains the same. Consequently, most of the water molecules will absorb
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Flash steam is a dynamic condition in which the water pressure suddenly drops below its boiling point and produces instant vaporization. While the fluid experiences an abrupt expansion, the total enthalpy and temperature will remain the same. Most of the water molecules will absorb the excess of energy, as latent heat, and end up forming
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The main purpose of material selection is to reduce the cost of the design while meeting the operation performance target. However, due to the transient nature of commissioning, field activities can be significantly aggressive, and under some circumstances, can even exceed the operation conditions of in-line equipment. For this reason, it is very important to
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FAC Corrosion When a steel surface is in contact with water under specific chemical and thermodynamic conditions, an oxide protective layer of magnetite (Fe3O4) is developed. Controlling the growth mechanism, the morphology and the solubility of such corrosion product it is possible to minimize the risk of failure and extend the life-time of the plant.
Short-Term Overheating Commissioning is likely the most critical stage in the life time of a power plant due to the transient conditions which boilers are subjected to. From the first ramp-up to normal operation, the plant is exposed to a variety of transitory conditions, thermal expansions cycles, chemical excursion and equipment adjustments that potentially increase
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Chloride Attack on CS This photo illustrates the corrosion pattern of chloride attack on carbon steel and it was taken during an inspection carried out in a cooling water pump of a steam-water cycle. Description The pump was subject to severe degeneration due to the formation of corrosion cells in which the corrosion product forms
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Back-End Corrosion Background When sulphur is present in natural gas, the average content is generally around 0.01% and it comes in the form of hydrogen sulfide. Problem Even in small quantities, sulfides will react with atomic oxygen in the flame zone of the combustion chamber to be converted to sulphur dioxide and subsequently oxidized to
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