| A large amount of edible oil is consumed in China each year,which leads to theemergence of more than5million ton waste oil.The waste oil can not be eaten onceagain because of containing toxic and harmful substances,however,they can berecycled and used as industrial raw materials for producing biodiesel,soap, mineraldressing collector,casting binder,organic fertilizer and so forth.In this paper, feasible technologies of biodiesel and soap production have beenstudied in consideration of waste oil properties collected in the central and westernregions of Inner Mongolia. Meanwhile,the technology of recycling and refiningglycerol,the byproduct of biodiesel, has been studied.Details of the study are asfollowing:1.The properties of waste oil collected in Inner Mongolia were tested.The data areimportant for pre-treatment,transesterification for producing biodiesel as well assaponification for producing soap.2.Three waste oil degumming methods, acidification degumming,hydrationdegumming and combined acidification-hydration degumming were compared.Theresult shows that the method of combined acidification-hydration degumming is mosteffective.The optimal degumming technological conditions have been achievedthrough singal factor experiments and an orthogonal experiment. The degumming ratereached to96.70%at the temperature of60℃, phosphoric acid dosageof0.1%,acidification time of40min,water dosage of3%,hydration time of30min.3.Degummed waste oil was decolored by applying the method of combinedhydrogen peroxide-diatomaceous earth decoloring.A89.75%decoloration rate wasachieved at degumming temperature of90℃,hydrogen peroxide dosage of0.12mL/gand decoloration time of30min,diatomaceous earth dosage of10%and decolorationtime of40min through singal factor experiments and an orthogonal experiment.4.Esterification of glycerol and free fat acids was catalyzed by solid superacidSO42-/ZrO2for the purpose of lowering the acid value(AV) of pretreated feedstock.Thereaction conditions were optimized through singal factor experiments and anorthogonal experiment as molar ratio of glycerol to acid of1.0,catalyst dosage of0.25%,reaction temperature of220℃and reaction timeof1.5h. The estification ratereached to99.87%under such a condition. The AV of waste oil was lowed as0.22mgKOH/g which meets the transesterification requirement(AV<3mgKOH/g). 5.Biodiesel was produced through sodium hydrated catalyzed transesterification oflow AV waste oil.The transesterification technological conditions were optimizedthrough singal factor experiments and an orthogonal experiment as molar ratio ofmethonal to oil of12:1, catalyst dosage of1.5%, reaction temperature of70℃andreaction time of1h.The yield of biodiesel was88.19%.6.The biodiesel quality was evaluated according to GB/T20828–2007《Biodieselblend stock (BD100) for diesel engine fuels》.The results demonstrated that elevenitems meet the requirements except for water,sulfated ash and cetane number.7.Soap was produced by the steps of saponification,salting out,washing,shapingand drying. The optimal reaction condition was achieved through singal factorexperiments and an orthogonal experiment as temperature of65℃, mass ratio of waterto oil of0.5, the amount of exceeding alkali of8%,saponification time of4h.Thesaponification rate of98.36%was achieved under such a conditon.Light colored soaphas been produced after salting out,washing,shaping and drying soap base.Threequality indicators were determined,however,results showed that the amount of NaOHand NaCl residue are excessive respectively.8.Glycerol,the byproduct of biodiesel,has been recycled and refined through thesteps of dilution,neutralization,drying and distillation.The results of single factorexperiments showed that water is a better diluent and the recovery rate is higher in theconditions of water dosage20%and pH=2.The final recovery rate of refined glycerolreached to97.86%through reduced pressure distillation.The refined glycerol is nearlycolorless and its purity is98.12%. |
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