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chemicals for the periodical cleaning (CIP, cleaning replacement were considered for the membrane
in place) and periodical biocide addition were taken deaeration project.
into account. In terms of operative costs, the process based on
Finally, to complete the operative costs also the the utilization of membrane deaeration is more ex-
consumption of consumables was evaluated: pensive. In the costs analysis, the adsorbed power
random packing was considered for the vacuum was not associated to any costs, since usually in
towers while both membrane and cartridge filters platforms the electricity is produced in place. The
higher adsorbed power of the vacuum deaerator
project is due to the utilization of the booster pum-
Properties MDA VT ps and of all the chemical dosing pumps which are
Biocide I, not required in the MDA based project.
Chemicals CIP mainly for biocide II, In addition, a lower annual chemical consumption
(Antifoaming and surface / raw antifoaming of chemicals is required for the membrane deaera-
tion than in the vacuum towers: in fact, while in the
Biocide) water and oxygen case of VT oxygen scavenger biocide I, biocide II
scavenger and antifoaming should be dosed to the tower, in
the case of membranes only a periodical cleaning
Membrane Random
Internals (CIP) is required.
Cartridge filters Packing
On the other side, regarding the consumables
Of the FRP Related to costs, the use of vacuum towers is cheaper since
Expected Service Life vessel is higher packing the plastic random packing has very long life while
than 10 years material in the case of MDA project, membrane cartridge
replacement after about 3 years and cartridge fil-
Easy Installation ters replacement 4 times per year should be provi-
Installation More Complex
and Modularity ded.
As a conclusion of costs comparison between
Table 7. VT vs MDA: General characteristics vacuum towers and membrane deaeration sy-
stems, a capex saving of 14% is obtained when
membrane deaeration systems
are used instead of vacuum
VACUUM % OF THE
MEMBRANE % OF THE towers. On the contrary, the
CAPEX DEAERATION (€) TOTAL CAPEX TOWERS TOTAL utilization of the MDA instead
(€) CAPEX
of VTs implies 14% higher ope-
rative costs (OPEX) because of
EQUIPMENT 330000 67% 405000 71% the high membranes replace-
ment cost.
INSTRUMENTS 68000 14% 63000 11%

PIPING & VALVES 91000 19% 102000 18%
5. Conclusions
TOT(€) 489000 570000 Membrane deaeration repre-
sents a promising alternative
Table 8. Capex comparison between membrane deaeration and vacuum towers project to the conventional deaeration
based on vacuum towers in
the field of offshore seawater
MDA VT injection applications. A com-
parison between two equi-
valent systems with an equal
% of the total % of the total capacity of 92.5 m /h, showed
3
OPEX OPEX
OPEX OPEX that MDA overperformed VT
system in many aspects:
Adsorbed Power 200000 KWh/y - 540000 KWh/y -
• In terms of processing
performances: oxygen outlet
Chemicals 6700€/year 9% 66000€/year 100%
concentration was lower than
10 ppb while in VT was about
Consumables 70000€/year 91% 0 0% 50 ppm;
• From an economical
TOT 76700€ 66000€ point of view: 14% CAPEX sa-
vings and 14% OPEX loss;
Table 9. Opex comparison between membrane deaeration and vacuum towers project • In terms of space and
weight savings: 21% overall

Impiantistica Italiana - Luglio-Agosto 2017 71