Recovery is a section of Refining where syrups in excess from Affination and Crystallization are crystallized in successive boilings, normally in four boilings, untill a syrup is obtained from where it is not economically possible to extract more sucrose. This final syrup is named molasses.
Sugar recovered in the last two crystallizations is used, as a magma for crystallization foot, in the previous boilings. Sugars produced in the two first boilings, (PR and A bolilings) (PR-pre recovery), are melted in Affination.
Simplified scheme of Recovery
In this scheme it is presented three boilings (A, B, C) in the double-einwurf way. In the first boiling A massecuite is obtained by crystallizing affination syrup and 4th syrup. In this boiling a magma footing, A magma, prepared with B sugar and A syrup, is used to start the crystallization . A massecuite is centrifuged in batch or continual machines and the sugar obtained, A sugar or recovered sugar, is sent to the affination melter to be mixed with affined sugar, producing the affination liquor. The syrup resulting from A massecuite, A syrup, is crystallized in the second recovery boiling, producing B massecuite. This boiling uses a footing, B magma, prepared with C sugar and B syrup. From this massecuite, B sugar and B syrup are separated in continual centrifuges. B syrup is used to crystallize the C massecuite. This boiling is seeded using powder sugar slurry in ethanol or isopropanol. Before centrifugation, C massecuite is cooled to increase crystal size allowing the maximum possible sucrose extraction. After cooling, C massecuite is re-heated before centrifugation. Centrifugation is done in continual centrifuges and low purity syrup, molasses, is obtained. Sugar obtained in this centrifugation, C sugar is used to form the B magma.
Lyle, O., Recovery, in Technology for Sugar Refinery Workers, Ed. Chapman &
Hall Ltd, London, 3rd ed, rep. 1970, Chap.15, 333-343