The CVOC System has been designed to utilize hydrostatic
pressure in the cargo tanks to re-absorb emitted VOC back into the
Crude Oil. This process allows tank pressure to be reduced without
venting to the atmosphere, and thus eliminates all emissions from
the cargo during transit – including H2S. The CVOC
system will also reduce VOC emissions from the cargo during loading
and cargo transfer operations.
The CVOC system is based on direct absorption of VOC in
the crude oil. The Swirl Absorber, a combined ejector and mixing unit,
are using crude oil from one of the cargo tanks to create a low-pressure
area where vapour from the main inert gas line can be mixed with crude
oil. The mix of VOC, inert gas and crude oil is then led back into
the same cargo tank the crude oil was originally taken from. VOC is
absorbed in the crude oil due to increased pressure in the bottom
of the cargo tank, while inert gas rises to the surface without being
absorbed.
Oil circulation is obtained by using a standard centrifugal
pump driven by an electrical motor, and system operation is controlled
by a simple PLC located in the engine-room and a number of pressure
and temperature sensors. Operation and monitoring is done on two 10"
LCD touch screen panels located in the Cargo Control Room and on the
Bridge.
Automatic system operation is controlled by a dedicated
pressure sensor installed in the main inert gas line, and is based
on pre-set pressure levels determined by the crew. The CVOC system
can also be operated manually as long as the cargo tank pressure is
sufficient.
The CVOC System is a stand-alone installation, and has no
interference with existing safety features or operational procedures.