Technology

GRS utilises liquid nitrogen as coolant. The nitrogen never mixes with the cargo vapour stream and leaves the unit as a pure gas. The vaporised nitrogen can be used for purging or blanketing of the cargo containment system or for in-plant operations. The cargo vapours to be recovered from the cargo containment system are simply replaced by nitrogen vapours generated during the liquefaction process in the GRS unit.

A direct heat exchange between the liquid nitrogen and the cargo vapours would result in operational problems in the GRS unit, due to solidification of most of the hydrocarbons at the extremely low temperatures. To avoid this problem, a heat transfer fluid is used as the intermediate between both the liquid nitrogen and cargo vapours. The temperature of the heat transfer fluid is adjusted as a function of the nature of the compound to be liquefied.

Liquid nitrogen is introduced to a nitrogen vaporiser where it is vaporised against the heat transfer fluid with the result of cooling down the latter.

In the cargo condenser, the VOC’s are liquefied by heat exchange with the chilled heat transfer fluid. From the condenser, the liquefied VOC – incondensable mixture flows to the vapour / liquid separator. Incondensable, such as nitrogen vapours, are released from the top of the separator to the atmosphere. The condensate is pumped from the liquid collector of the separator to storage or to plant facilities. Complete condensation occurs in the condenser and an extremely efficient recovery of the product is achieved.

A fully integrated control system makes this system easy to adjust for flow and concentration fluctuations. Few moving parts makes the compact and transportable GRS unit very reliable, provides low energy consumption and guarantees a low maintenance cost.