Trapping of Volatile
Emissions by Cryogenic Condensation
Air Products PLC had identified a market for
their Cryo-CondapTM technology which reduces pollution
using cryogenic condensation. They needed technical
support to handle the technical sales, and to design,
build, install and commission the system at the customer’s
site. They used Monroe Brothers Ltd engineering abilities
to resource these needs for a new customer installation.
The Service Provided
A responsible approach towards protecting
the environment means limiting the emissions of volatile components.
One method is the condensation of these components by cooling
the exhaust stream with liquid nitrogen. As the vapours are
cooled the volatile components condense and then freeze. These
solid particles can be trapped leaving a clean stream of gas
to vent to the atmosphere. Air Products has branded this offering
as Cryo-Condap™ for CRYOgenic CONDensation
Working on behalf of Air Products, Monroe Brothers Ltd has
developed computer design tools to model these heat
transfer mechanisms and generate valid heat exchanger
designs. The understanding of the heat transfer mechanisms
has promoted special heat exchanger geometries which
are best suited to the properties of boiling nitrogen
and condensation of gases within incondensable vapours.
The temperatures required to meet acceptable
emission standards of the order of tens parts per million
(ppm) are typically -100°C and lower. The obvious
choice of a cooling medium is liquid nitrogen which
is stored at temperatures around -180°C. The design
of the heat exchangers poses a special challenge which
is beyond the remit of typical heat exchanger packages.
Not only are the temperatures outside the normal parameters
but the heat transfer relationships have to consider
the boiling and gas heating of the nitrogen, and the
condensation and freezing of multiple volatile components
in an incondensable stream.
Above: The vertical
heat exchanger mounted above the 1500 litre vinyl chloride
The system presented in this
case study was successfully installed on the Manchester Ship
Canal to recover Vinyl Chloride from the ship loading arm.
The requirement arises at the end of a loading process when
the connection between the ship and the loading arm has to
broken without losing any vinyl chloride. To achieve this
the loading arm is purged with nitrogen and the discharge
gas is passed through the Cryo-CondapTM to trap and remove
the vinyl chloride. Monroe Brothers Ltd designed the system
and project managed the construction and installation.
The specification required
cooling the gases to -120°C and collecting 1500 litres
of vinyl chloride. The system has operated successfully since
Monroe Brothers Ltd applied its skills in technical sales
to help Air Products win the contract. The system was designed
and the manufacture was project managed by Monroe Brothers
Ltd resulting in a successful commissioning on the Manchester
Ship Canal in Runcorn.
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