Danfoss iSave 21, Руководство пользователя

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User manual iSave 21
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180R9221 / 521B1174 / DKCFN.PS.003.A1.02
The high-pressure (HP) concentrate (7) flows to the low-pressure (LP) concentrate outlet (3).
The LP sea water (2) flows to the HP sea water outlet (5).
The rotor, moving between the high-pressure and low-pressure streams, removes the high-
pressure concentrate (7) and replaces it with feed water (2).
The flow rate on the HP sea water outlet (5) is controlled by the iSave alone.
The flow rate on the LP concentrate outlet (3) is controlled by the sea water feed pump (1)
and the back pressure valve. This means that changing the LP feed flow (2) will not affect
HP outlet flow (5) and, vice versa, that changing the HP outlet flow (5) will not affect the LP
outlet flow (3).
As LP sea water (2) is flushing the LP concentrate to LP outlet (3), it is essential that the flow
on the LP inlet (2) is equal to or slightly higher than the HP inlet (7). Otherwise there will be
an “under-flush” and higher mixing will occur in the HP outlet (5). This higher mixing will
result in a slightly higher pressure at the membrane.
The booster pump integrated in the iSave must only overcome the pressure drop from the
high-pressure outlet (5) to the high-pressure inlet (7).
During the RO process operation, water is pumped into the HP-membrane feed (6) by the
HP pump (4) and the iSave (5). Almost all water coming from the HP pump (4) penetrates the
membranes (8). Only a slight amount of the water is used as lubrication flow in the iSave.
The lubrication flow is measured as the difference between the HP pump flow rate (4) and
the permeate flow rate (8). The resistance to permeate in the membrane pressurises the HP
loop.
The isobaric pressure exchanger technology in an SWRO or BWRO change the HP con-
centrate into HP seawater that is feed into the HP membranes. The iSave energy recovery
technology thus significantly reduces flow needed from the main HP pump (4).
Overall energy consumption of a SWRO or BWRO plant using the iSave depends on the
recovery rate.
The operator can change the recovery rate to optimise the RO system performance. Chang-
ing the recovery rate in an RO system equipped with iSave is easy. Using the VFD, change
the speed of the iSave and thereby the flow in the HP flow rate. Then change the LP feed (2)
flow to the iSave to minimise mixing and optimise energy consumption. Make sure that flow
and pressure are within the rated parameter of the iSave in question.
5.8 Seawater quality
5.8.1 Pre-filtration
It is important that the incoming water is filtered properly to assure optimum service life of
the iSave. A true graded density melt-blown depth filter cartridge rated at 3 μm is therefore
recommended. Poor pre-filtration of the feed water will result in reduced service life of the
iSave.
The iSave may request a different pre-filter of the seawater than the HP pump and other
components in the RO system.
As the various filters on the market differ greatly, Danfoss RO Solutions recommends us -
ing cartridges with consistent, reliable performance and high efficiency, in which fibres
are blown continuously onto a central support core.
Danfoss RO Solutions does not recommend cartridges requiring any type of binders or
resins.
NB!
Filters can be purchased from Danfoss RO Solutions.
NB!