Study On Sucrose Separation From Molasass By Membrane Filtration

The molasses is a subsidiary product of sugar industry, containing about 35% sucrose, equal 5.5%～6.0% of sugar concentration in sugarcane. As the high impurities, it's difficult to extract sucrose from molasses, so this part sugar was lost, but this loss is the biggest one during sugar produce process, if it can be recycled, the sugar output will be raised and the economic benefit of sugar mill will be increased.In this thesis, the membrane filtration is applied to separate sucrose from molasses, the purify conditions are studied firstly, including the factors of dilution degree , pH value , phosphoric acid amounts , flocculation dosages and the temperature, which can influence molasses solution purification, and optimize the experiment condition by orthogonal design. According to the experiment results, the optimum condition is diluting 7 times, 450 mg/L phosphoric acid, pH 8.0, 4mg/L flocculant, constant temperature of 85℃. On this condition, the OD value decreased 74.58% after be treated, and sugar content lost 12.47%.In order to separate big molecule impurities from molasses solution further, multi-level membrane filtration is used, the MWCO is 10 KDa,5 KDa,3 KD. Through this treatment, the color value is 4239 IU, reduced 60%, sugar content lost 12.02%, sucrose is 40.80mg/mL, reducing sugar is 7.96mg/mL. The membrane can achieve 90% recovery rate after three steps wash by water-chemistry-water, it's regenerated.The polysaccharides and monosaccharides can be separated by nanofiltration in throry, so the MWCO200 membrane is applied to study the effect on sucrose separation in molasses solution after ultrafiltration. The result indicated the rejection of sucrose is above 86%, the recovery rate of membrane reached above 97% after wash as little pollution of membrane. Furthermore, a MWC-SHP model is established based on SHP model, and the correlative membrane parameters in the sucrose separate process are gotten.The membrane filtration is applied in this thesis, based on the actual conditions in sugar mill, the pretreatment conditions and separate sucrose conditions by membrane were preliminary studied, this method is simple, more than 65% sucrose can be separated, and the membrane can be regenerated as little pollution, it can give a reference for synthetically utilization of molasses in sugar mill.