Fouling In Heat Exchangers - self-cleaning heat exchanger technology
The deposition of unwanted materials, such as scale, suspended solids, insoluble salts and even algae on the internal surfaces of the heat exchanger is called fouling. The presence of these deposits represents a resistance to the fluid flow and heat transfer and therefore increase the pressure drop and reduces the efficiency of the heat exchanger. The degree of fouling varies considerably with physical properties of fluids being handled. In severe fouling conditions, the heat exchanger may become blocked and hence inoperable because of the back pressure. Depending on the fouling deposits involved, they can lead to corrosion of the heat exchanger which can often be hidden by the fouling layer itself. This shortens the working life of the heat exchanger and can result in catastrophic failure.
Fouling removal
Despite the best efforts of engineers and technologists to eliminate heat exchanger fouling the growth of deposits will still occur. Periodic cleaning of the heat exchangers will be necessary to restore the heat exchanger to efficient operation. If the deposits are difficult to remove by mechanical means chemical cleaning may be required. The chemicals used for this purpose will often be aggressive in character and represent an effluent problem after the cleaning operation. Unless this effluent is properly treated it could also represent an environmental problem. Even water used for cleaning can become contaminated and may require suitable treatment before discharge.
However, in all cases, fouling prevention/reduction is more effective and also cheaper compared to the cure, i.e., fouling removal and heat exchanger cleaning. Klaren International offers innovative self-cleaning fluidized bed heat exchanger that prevents fouling in the early stages. With the Klaren’s self-cleaning heat exchanger technology, you can achieve up to zero fouling operations in your liquid stream, keep system clean and run plant without any operational constraints.
Conventional heat exchangers have the problem of severe fouling in the tubes. This can happen in just a matter of hours in severe cases. With the solid particles of our innovative self-cleaning heat exchanger technology, solid particles will be continuously cleaning the walls of the heat exchanger tubes with a mild scouring effect. These solid particles have diameters of 1.6 to 4 mm and consist of glass, ceramic or metal. A constant heat transfer coefficient is maintained by cleaning the heat exchanger tubes at an early stage of formation. Moreover, these particles reduce pressure drop compared to conventional heat exchangers and enhance the heat transfer at lower liquid velocities. When the rate of removal of deposits by the particles exceeds the rate of precipitation of deposits, zero-fouling is guaranteed.
How does the self-cleaning heat exchanger technology work?
The cleaning principle of the heat exchanger tubes is an ongoing cycle. It is based on the circulation of solid particles through the tubes of a vertical shell and tube heat exchanger. First, the fouling fluid flows up through the heat exchanger tube bundle and passes through the inlet and outlet channels. These channels are specially designed for this process. Second, the solid particles are fed to the fluid using a distribution system in the inlet channel. This happens to ensure consistent division of particles over all the tubes. The particles are then fluidized by the upward flow of liquid to remove any deposit at the beginning of fouling formation. They create the mild scouring, cleaning effect on the wall of the heat exchanger tubes. Lastly, after the particles are detached and separated from the liquid by the tube bundle, they move to the inlet channel through an external downcomer. After this, the cycle is repeated.
To control the amount of particles fed to the inlet, a part of the inlet flow to the heat exchanger is used to push the particles from the downcomer into the inlet channel. Changing the amount of particles is one of the parameters to influence the cleaning mechanism. Other parameters are particle size and material and the fluid velocity.
With this technology, fouling or clogging of heat exchangers can be prevented or minimized. The fluidized bed effectively handles many types of fouling including scaling, whether hard or soft, originating from biological, crystallization, chemical or particulate fouling mechanism, or a combination of these. A wide variety of fluids can be handled ranging from aqueous solutions to oils and slurries.
The cleaning particles used in the self-cleaning fluidized bed heat exchangers create the mild abrasive effect on the wall of the heat exchanger tubes, which removes the fouling deposits at an early stage of formation of the tube wall and keeps the heat transfer surface clean.
Depending on the application, i.e. the properties of the liquid and the fouling tendency, a specific type of cleaning particle is selected and used.
The removal rate of the self-cleaning fluidized bed heat exchanger is besides the volume fraction of the cleaning particles in the tubes (porosity of fluidized bed) influenced by the type (density and hardness) and the size of the cleaning particles.
Zero Fouling
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The cleaning particles are made of chopped metal wire or ceramics, with a diameter between 1.6 and 4 mm.
Credits https://klarenbv.com/
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