Annual Report 2009-2010 - Ministry Of Earth Sciences

The existing in situ soil testing system is being
upgraded for soil testing up to a depth of 6000m
in ocean.
Fig. 6.5: Conceptual and Schematic view of
LTTD plant installed in NCTPS
6.2 Desalination
6.2.1 Thermal Power Plants
Thermal power plants discharge warm water from
their condensers. The process that involves transfer
of tremendous levels of energy usually includes
heat recovery systems like cooling towers or heat
dissipating open channels before the condenserreject-water
is discharged back into the surrounding
environment at acceptable temperatures.
Consequently, the resultant thermal pollution by
the power plants is a serious issue today. An efficient
way to utilise the heat available in the condenserreject-water
would reduce the load on the cooling
towers and in turn the resultant thermal pollution.
One of the aspects of Low Temperature Thermal
Desalination (LTTD) is that it transfers the available
heat from warmer water to the colder water while
generating fresh water from the warm water. This
aspect could therefore, be aptly used in thermal
power plants resulting in the double benefits of
cooling the condenser reject-water and generating
the fresh water. A small temperature gradient of
about 8°-10°C, as is the case with most power plants,
would be sufficient to utilise the concept.
This concept has been demonstrated in North
Chennai Thermal Power Station (NCTPS). The 600
MW NCTPS plant discharges about 100,000 m 3 /hr
of condenser-reject-water at about 37°C. In order
to reduce the thermal pollution issues arising out
of mixing this water with the nearby seawater at
29°C, NCTPS lets the water run through a long
open channel where the water is brought down to
about 33°C.
A conceptual and schematic view of the plant is
shown in Fig. 6.5.
Here, the salinity of the freshwater was reduced
from 35000 ppm of the seawater to about 24 ppm,
the quality well suited for drinking water as well as
the use in the boilers.
6.2.2 Desalination Plants at Islands
After successful commissioning of land-based
demonstration plant in Kavaratti producing more
than 1 lakh litre per day of freshwater in May 2005,
similar plants in three more islands are being
established at the Agatti, Andrott & Minicoy islands
of Union Territory of Lakshadweep.
The major work of welding and deployment of
pipe for the cold water intake has been completed
at all the three islands. The construction of sump
at Agatti is in final stages and it is ready to be
placed in its location. The bridge connecting
plant to the shore is in progress in full swing
at Agatti. In Minicoy, sump has been placed in
its location and the construction of bridge is in
progress. The construction of plant structure
at both the islands is in advanced stage. All
the mechanical components required for the
establishment of the plant have reached the
site and commencement of erection of plant
components will start shortly after the Reinforced
Cement Concrete (RCC) plant structure has
Ministry of Earth Sciences : Annual Report 2009-10 35