“If you define the problem correctly, you almost have the solution.”
– Steve jobs
Fractional Electro De Mineralisation (FEDI) Process
The ElectroDe Mineralisation (EDI) process, invented over 20 years ago,
is a continuous, chemical-free method that removes ionized and ionizable
impurities from the feed water. EDI is most commonly used to treat
Reverse Osmosis (RO); permeate and replace Mixed Bed (MB) ion exchange;
producing ultrapure water of up to 18 M Ω.cm. EDI eliminates the need to
store and handle hazardous chemicals required for resin regeneration
and the associated neutralization steps.
Fractional ElectroDe Mineralisation (FEDI) process is an advancement of
EDI and was developed by taking into account the limitations of
conventional EDI. FEDI has been in the market for over five years now
and has been installed in power stations, refineries, and more. Many of
these FEDI systems supplied are some of the largest installed systems in
the world.
The patented dual voltage process allows
for a higher flexibility and tolerance to inlet water conditions, thus
lowering the risk of scaling, and improving the plant’s design economics
and reliability. FEDI products are supported with CE conformity
certificates.
FEDI Technology
There are two types of ionic impurities removed in an EDI process; strongly ionized impurities (divalent ions such as Ca, Mg, SO4 and monovalent ions such as Na, Cl and HCO3) and weakly ionized impurities (such as CO2 B and SiO2).
Both types of ionic impurities require a different driving force
(current) for movement and separation. Strongly ionized impurities
require less current, whereas weakly ionized impurities require more.
Rather than applying one current to the entire module, the FEDI process
differentiates the treatment of weakly ionized and strongly ionized
impurities by applying different currents and voltages in a two stage
process. This allows a significant portion of strongly ionized
impurities, mainly the divalent ions, which can cause precipitation at a
higher voltage, to be removed in Stage-1. Subsequently, a higher
voltage is applied for removing weakly ionized impurities in Stage-2.
The rejected ions from both stages are removed, using separate reject
streams, thus preventing hardness precipitation.
FEDI Technology
Hardness is the scaling component and the main limiting factor for feed
conditions in a conventional EDI. By incorporating a two-stage
separation process with different voltages the FEDI process is able to:
1. Achieve a higher hardness tolerance by having distinctly
different concentrate chambers with separate reject streams and thus
reducing the potential of hardness scaling.
2. Optimize power consumption by using higher electrical current only where required.
3. Ensure
the best water quality, continuously & consistently by removing a
major part of the De Mineralisation load in the ‘hardness removal zone’,
while residual ionic impurities are effectively removed in the ‘silica
removal zone’, which stays in a polishing mode.
