Finned tube heat exchanger used as a desublimator for isolating sublimation products, especially phthalic anhydride, from reaction gases

Claim 1

A finned tube heat exchanger used as a desublimator for isolating sublimation products, especially phthalic anhydride, from reaction gases, which consists of a housing with connections to permit the passage of the reaction gas and the discharge of the molten sublimation product, and of several rows, fitted one above the other, approximately horizontally, within the housing, of identical finned tube bundles, supported so that they can move independently of one another when undergoing thermal expansion or contraction, the bundles being intended alternately to be subjected, from the inside, to a heating medium and a coolant, especially a heat transfer oil, wherein the reaction gas travels, within the housing, transversely to the direction of flow of the heating medium and coolant in the tubes, and finned tube bundles, arranged parallel, above one another and optionally also alongside one another, consist of at least two rows of tubes, arranged above one another, which are connected to one another, at one end, by tube bends, to form a hairpin tube, and at the opposite end, the rows of tubes are connected, by means of a tube plate, to a collecting and distributor chamber for the heating medium or coolant, and the transverse fins mounted on the core tubes are staggered laterally in rows, in opposite directions, within each tube bundle, wherein each finned tube bundle (1) consists of four superposed rows of tubes, with the said superposed tubes (2, 2a, 2b) being aligned with one another relative to the direction of flow of the reaction gases, the tubes of the rows of tubes being connected to one another, by the common header (6), in such a way that the same stream of heating medium or coolant successively flows through the tubes or groups of tubes of the first and third row of tubes and of the second and fourth row of tubes and the transverse fins (3, 3a, 3b) fixed on the core tubes (2, 2a, 2b) being mounted on the latter eccentrically to the axes of the tubes and staggered in rows, laterally in opposite directions, by an amount corresponding to about from half the spacing to the whole spacing between the laterally adjacent edges of fins.