The study of the mechanism of magnetic water treatment for the prevention of scale and corrosion.
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Date
2004
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Abstract
Scaling and corrosion cost industries all over the world millions of rands each year.
Chemical treatment of water to prevent scale is expensive and can be hazardous. As a
result industry is always looking for new, cheaper alternate methods of reducing scale.
One such method is magnetic water treatment. Magnetic water treatment involves
passing hard water (the main cause of scale) through a magnetic field. This method
favors the precipitation of calcium carbonate in the form of aragonite instead of
calcite. Aragonite is a softer, less tenacious material that does not adhere to the walls
of pipes or heating surfaces. These particles remain in suspension and may settle out
somewhere along the system where the velocity of the water has been reduced.
A simple bench-top heating system was set up to determine whether magnetic
treatment works and, if it does, to determine the optimum conditions under which it
operates. A saturated solution of calcium carbonate was circulated through the heating
system with, and without the magnets, so that comparisons could be made.
The precipitate was analysed (via X-ray diffraction) to calculate the proportions of
calcite and aragonite, while atomic absorption was used to test the hardness of the
filtrate. This gave an indication of the effectiveness of the magnetic system. pH
graphs and absorption graphs were plotted to compare the rates of precipitation. The
precipitate was also observed under the electron microscope in order to view the
different structures of calcite and aragonite.
Experiments were carried out at different temperatures and different flow rates in
order to test the effect of these parameters on the magnetic system.
Results showed that the magnetic field increased the rate of precipitation and caused
aragonite rather than calcite to be formed. This was in contradiction with most
literature surveyed, which stated that magnetism increased the dissolution of calcium
carbonate. Results indicated that the higher the temperature, the greater was the rate
of precipitation and as a result, the greater the amount of aragonite formed, even
without the magnets. Increased flow rate also increased the amount of aragonite
formed. As a result hereof, conclusive results could not be obtained at high
temperatures and high flow rates.
Description
Thesis (M.Sc.Eng.)-University of Durban-Westville, 2004.
Keywords
Chemical engineering., Water treatment., Theses--Chemical engineering.