Definition of Sediment:
When water is used as a thermal fluid, the solubility and hardness of the water are separated by thermal shock and settling on the surface and depositing. These sediments are one of the most important factors of erosion and corrosion in thermal and refrigerating plants. The presence of sediments, in addition to corrosion, also drains a significant amount of energy due to the lack of heat exchange and reduces the efficiency of the plant.
The effect of sedimentation on energy losses is a subject that is being considered today, so that it is estimated , about $ 45 billion annually is our waste of energy from sediment in all countries, which is equivalent to 0.2% of the world’s net production.
With increasing concentrations of substances and solids dissolved and suspended in boilers (boilers), heat exchangers and … the possibility of forming
Sediment increases. According to Fig. 1, the formation of sediment in water comes from two sources:
1 concentration of substances and particles dissolved in water), which occurs as the temperature increases and the saturated ions become deposited
2 suspended matter In water, which can be caused by corrosion products, suspended particles of air or growth of microorganisms in water.
The factors influencing the formation of a sticky sedimentary layer are:
1 Fluid temperature and surface temperature …
2 speed of Fluid
3. Size and composition of particles in the fluid
4 time fluid flow
Disadvantages and problems caused by the formation of sediment:
The presence of sediments reduces the inner diameter of the pipes and, as a result, decreases the flow of water. Also, sediments act as a thermal insulator at heat transfer surfaces. Therefore, both factors reduce the heat transfer and thermal efficiency of steam boilers, heat exchangers, and so on. The presence of any deposits in equipment such as steam boilers is undesirable, so its constituent elements, such as calcium, magnesium, iron and silica, should be separated from the water entering the boiler. Because the heat absorption of combustion gases is reduced by reducing the heat transfer and heat recovery of the boiler, energy is wasted and steam production is reduced. Therefore, the amount of fuel consumed by the boiler is increased to compensate for the reduced steam production.
Thermal surfaces and pipes that are insulated on one side with insulators, and on the other hand at hot gas temperatures, are very hot, losing their resistance. In this case, the cracking of the tubes and even the boiler’s skin will be inevitable. Therefore, providing appropriate solutions to these problems is of great importance. Meanwhile, sediments can accelerate corrosion. Accumulation of sediments, corrosion products and their aggregation causes formation of bulges and swollen spots on surfaces.
Problems creating sediment in the facility:
Increasing sediment causes problems and problems, the most important of which are:
– Severe reduction of heat transfer system
– Reduce the speed and amount of water in the system
– Corrosion of boilers and other thermal systems
– Reduced production of steam-water quality
– Waste of chemicals
– Remaining stain on products and food and textile
– Increase the amount of heat and energy required for the operation of cooling and heating
– Significant reduction in system efficiency
In order to remove the remaining sediment, facility operators with any type of treatment system will eventually encounter a significant amount of sediment that will inevitably be dissolved. Eliminating the remaining residues by acid.
Different chemicals are used in various industries, but in the general way, there is a lot of similarity.