لخّصلي

Many differences exist between the two configurations, whereby the OT design is not only
easier in concept and design but also has a higher performance ratio, especially in the case of
large-scale projects. According to [22], three major features verify the advancement of the OT
design—the performance ratio, the top brine temperature and the brine loading, all of which
are superior. For example, the performance ratio is just like efficiency, and it can reach 12 for
the once-through design. The top brine temperature can increase106C, which means efficient
absorption of thermal energy (heat) from heating steam. It should be noted here that the main
disadvantage of the OT design is its high consumption of chemicals for the pretreatment of
water. On the other hand, the elimination of the heat rejection section and the recirculation
pump, with all of the associated controls and civil work, means lower capital investment and
simpler operation than is the case with the brine recirculation (BR) configuration. In any case,
the selection of a specific configuration depends mainly on economic and operational
considerations.
The BR practice uses very few chemicals for makeup pretreatment. The consumption of
chemicals depends on the volume of seawater to be treated, as well as the concentration ratio.
While dosing rates, in ppm, are lower for the OT process, as the coolant seawater has the
equivalent feed concentration, the large intake flow rate calls for a higher rate of chemical
dosing than in the case of BR. The net result is higher overall chemical consumption in the
OT process. In the BR process, deaeration of the pretreatment is accomplished in a deaerator,
which is integrated with the last rejection stage. Further, deaeration takes place in the first few
stages of the OT process. This is a disadvantage since the amounts of noncondensable gases
released, including oxygen, are much higher than what is released by recycling in The BR
process [23].
1.6.1 Process Description
In this part, the process by which seawater goes through the desalination stages is described.
As mentioned above, the first level of the process is the start-up of the water supply to the
station.
The temperature of the intake was around 25–30 ◦C; therefore, a preheater was added to the
simulated plant to moderate the intake seawater temperature through the year, whereby the
influent seawater into the plant was fixed at approximately 40 ◦C. Some chemicals are added
to the feed water (anti-scaling, chlorine, and anti-foaming). Chlorine is added to the seawater
feed at the source to avoid bio-fouling inside the condenser tubes [24].
The water is then pumped to the deaerator and then into the condenser tubes (the heat
recovery section) to increase its temperature, stage by stage. After warming the seawater feed
in the condenser tubes, part of this feed water is evacuated to the sea (known as cooling
water),while the rest of the feed water is delivered to the deaerator (known as makeup wate