Processing P. Gorce, Vo Ngoc Truoc, L. Lincoln ndustrielle Sucriere de Bourbon, Reunion ABSTRACT During the 1985 sugar crop, the patented "continuous crystallization under vacuum" process was operated with success in Reunion sland at the GOL and Bois Rouge factories. At GOL it was possible after only two weeks of trial to change the boiling formula from 3 to 2 boilings. Besides appreciable reduction in energy consumption, the system has resulted in considerable savings in investment, maintenance, and labour costs, and contributed to better boiling house recovery and better sugar quality. HSTORCAL n 1981 the Beghin-Say Company successfully experimented with continuous crystallization under vacuum at its Nantes (France) cane sugar refinery. The increase in crystal weight in refinery 1st strikes was 45%. The process, tested and patented in 1982, was subsequently adapted at the Sermaize (France) syrup plant on beet derived products of 90-95 " purity; the resulting increase in crystal weight reached over 20%. More units have since been installed in France and Germany with similar results Also in 1985 the Beghin-Say Co. and the Sucreries L. Benard signed an agreement to test and "optimize" the process on A-strikes at the GOL raw cane sugar factory. At the same time, a similar agreement was concluded with the ndustrielle Sucriere de Bourbon with a view to testing the process on a small existing vacuum crystallizer at Bois Rouge factory. This adaptation to the cane sugar industry, now to be described, is the normal and logical step in generalising the process of continuous crystallization under vacuum (CCUV). DESCRPTON OF THE PROCESS The CCUV process has been described in several technical papers presented at the annual meeting of the Sugar ndustry Technicians in 1984 and certain magazines in 1984, namely: "ndustries Agricoles et Alimentaires", "Sucreries Francaises" (France) and "Sugar y Azucar" (U.S.A.). Massecuite from the pans is pumped into a continuous crystallizer under constant vacuum. After coming out of the crystallizer, it is purged and part of the low-purity runnings derived from it are heated, and returned to the crystallizer at a rate proportional to the massecuite flow. The rest is sent back to the boiling house. The violent agitation, the cooling, and the concentration of the mixture through Keywords: Vacuuni crystallization, continuous crystallization, molasses recirculation
PROCESSNG flashing due to the high vacuum inside the vessel, produce a rapid but controlled growth of sugar crystals. The whole process is quite different from the established crystallization by air or water cooling, the inconveniences of which are well-known: air cooling is slow, and requires a long retention time, and consequently lots of equipment; more rapid cooling by water also requires substantial investment and maintenance costs, more labour etc. a Vacuum-pump FGURE 1. @ Massecuite in the C.V.C. @ Sight glass for run-off intake @ Plate heat-exchanger for treatment of run-off a Drive for spiral agitator @ Massecuite pumps
p GORCE, VO NGOC TRUOC AND L. LNCOLN TABLE. Preliminary results with continuous crystallization BOlS ROUGE G 0 L List of tems 1984 CROP 1985 CROP 1984 CROP 1985 CROP without with without with Contin. Crystal. Contin. Crystal. Contin. Crystal. Contin. Crystal. Syrup purity 88.1 88.0-86.5 A massecuite, ex pan Brix... 92.15 91.5 91.4 92.7 Purity... 87.6 86.9 86.7 84.3 Crystal %... 51.68 51 55 54.7 Temperature OC... 74 76, 74 70174 Runnings recycled O/o massecuite... - 30-42 A massecuite, ex C.C. Brix... - 89-90.2 Purity... - - - 78.2 Crystal %... - 48-47.6 Temperature OC... - 60165-5 1 Crystal gain in C.C. % massecuite... - 1011 5-17 Pol of sugar... 98.78 98.78 98.5 99 - A massecuite, m31t sugar - - 1.47 1.22 Molasses purity 42.0 43.5 42.6 40.77 Reduction in sugar loss - - 0 0.3 Steam saving, kglt cane... 10 Equiv. fuel oil kglt cane... 0.8 Labour savings 8
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p. GORCE, VO NGOC TRUOC AND L. LNCOLN 687 \, WEGHT OF SUGAR - 59 51 1 70 WEGHT OF CANES = 506 547 90 water evaporated : 43.8 water evaoorated. 1.9 washlng 7 6 C C U v heating Steam H P R ccuv~ut~~n 038, l ~ S 26 ~ 1 ~. BRX 90 2 PUR 78 2,HGH RUNNNGS PURTY D.Mi76 S 138 1 N.S. 38 TOT. 195 TOT. 55 A SUGAR HGH PURTY RUNNNGS LOW PURTY RUNNNGS BRX 99 1 PUR 98 9 BRlX 80 6 PUR 60 0 BRlX 73 7 PUR 66 7 D M 79 S 78 DM 75 S 45 /\ DM 22 S 15 N S 1 TOT 79 N S 30 TOT 94 N s 7 TOT 30 water evaporated 9 9 /', LPR Masseculte C DM12 S 8 BRX957 PUR 61 8 N S 4 TOT 16 \ / d~lutlon water 1.8 N S 4 TOT 23 NS 12 TOT27 D M =Dry Matter N S =Non Sugar C C U V CONTNUOUS CRYSTALLZATON UNDER VACUUM PUR =Purity S =Sugar FGURE 2. Crystallization flow diagram, GOL factory