Patent ID: 8277562

Claim:
A vacuum pan including: a vessel for receiving massecuite, the vessel being in flow communication with a low pressure source in order for the vessel in use to be operable under a low pressure; a heat exchanger for heating the massecuite located in the vessel; the heat exchanger including a first massecuite flow path for conveying massecuite therethrough, and a heat transfer medium flow path for receiving a heat transfer medium; wherein the vacuum pan is configured such that a second massecuite flow path is defined in the vessel at least partially adjacent a side of the heat exchanger, and wherein an insulated zone is provided between the heat transfer medium flow path of the heat exchanger and the second flow path, in order to reduce heat transfer between the heat exchanger and the second flow path, wherein the insulated zone is in the form of a double wall defining an internal cavity therebetween, and which separates the heat transfer medium flow path of the heat exchanger from the second flow path, and wherein the internal cavity is in flow communication with a vapour space of the vacuum pan in which the heat exchanger is located in order for the internal cavity to be evacuated to a pressure similar to the pressure in the vapour space, at which pressure the saturated vapour temperature of vapour in the internal cavity is below the boiling point of massecuite in the second flow path.