Trapping of Volatile Emissions by Cryogenic Condensation

The Need
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 Air Products.

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 tank

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 1999.

The Benefit
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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