【作者】 林琳；

【导师】 董英；

【作者基本信息】 江苏大学 ， 食品科学， 2007， 博士

【摘要】 相对于传统石油基燃料而言,生物柴油因其具有可再生、有害物质排放少等优点,而日益引起人们的关注。以大豆油、菜籽油制备生物柴油的主要问题在于其原料与粮争地和成本过高,迫切需要寻找一种资源丰富、价格低廉的原料,以降低生产成本。米糠是稻米加工的副产物,约占稻米质量分数6～10%,目前多用于畜禽饲料。米糠中油的含量为质量分数16～32%,由于脂酶的存在,米糠油极易水解、氧化,从而导致不宜食用,即便作为饲料,其品质也难以保证。我国米糠资源丰富,将其用于制备生物柴油,既可合理利用米糠油资源,又可提高饲料的质量。本论文以米糠油为原料制备生物柴油,即米糠甲酯(RBME),进行了米糠油原料特性、酯交换反应工艺条件及乳化油制备的研究,并对所制备的燃料油的燃烧与排放性能进行了台架试验研究。主要研究工作如下:1.米糠油的理化性能指标和脂肪酸组成是其能否制备或作为石化柴油替代燃料的关键。本文采用气相色谱—质谱仪和常规分析仪器对米糠油的理化性能指标和脂肪酸组成进行了测定与分析。结果表明米糠油主要由棕榈酸、油酸和亚油酸三种脂肪酸组成,其结构与理想的柴油替代品结构类似,具有制备生物柴油的条件。同时,由于其酸价过高,在进行酯交换反应前需要做降酸处理。2.采用机械搅拌碱催化酯交换反应制备RBME。试验结果显示在KOH催化条件下,根据转化率所得最佳工艺条件为:醇油摩尔比为6,催化剂用量0.9%,反应温度60℃,反应时间45min。而由得率所得的米糠油制备RBME的最优反应条件为:醇油摩尔比6,催化剂用量1%,反应温度50℃,反应时间60min。4因素对转化率和得率的影响大小顺序均为醇油比＞催化剂用量＞反应温度＞反应时间。3.采用超声波辅助碱催化酯交换反应制备RBME。结果显示与传统的机械搅拌相比,超声波辅助方法可以缩短酯交换反应的时间15～20min。超声频率40kHz条件下反应速度较28kHz快,但是由于产物水洗分离困难而使得产物得率反而有所下降。超声辅助酯交换法还可以减少催化剂的用量,当催化剂用量为质量分数0.5%时可得到最高的转化率和得率。4.对RBME的燃烧及排放性能进行发动机台架试验。试验结果显示其各项燃料指标均能达到美国ASTM或德国DIN相关生物柴油标准,具有良好的燃料特性。在不对发动机结构进行改动的情况下,未造成燃烧恶化,燃烧情况和0~#柴油十分接近。燃用RBME输出功率与0~#柴油基本相当,油耗略有增加,可以显著降低CO、HC的排放,但NO_x排放有少量增加。5.在柴油—乙醇混合燃料中添加RBME制备柴油—RBME—醇混合燃料并对其稳定性和燃料特性进行研究。试验结果表明,加入RBME可以显著改善柴油—醇混合燃料的稳定性以及十六烷值等燃料特性,同时还可以相应的提高柴油—醇混合燃料的燃烧及排放状况。但是柴油—RBME—乙醇三相混合燃料在0℃以下稳定性较差,有待进一步的研究。6.以柴油—RBME—乙醇混合燃料为对象,研究了混合燃料中含氧量对排放性能的影响。试验结果显示,在混合燃料含氧量低于RBME含氧量时,CO和HC的排放量随着含氧量增加而减少。但随着混合燃料中乙醇所占比例增加,虽然燃料含氧量不断增加,但是CO和HC排放量增加。NOx排放量则随着燃料含氧量的增加而增加,而碳烟颗粒物的排放量则随着燃料含氧量的增加而减少。7.采用Span80和Tween80制备RBME—水乳化燃料。试验结果显示制备W/O型乳化油的较佳条件是:加入乳化剂量的质量分数为0.5%,温度30℃时,油水体积比为9,搅拌转速3000r/min,搅拌时间15min,HLB值为4。制备O/W/O型乳化油时,其较佳HLB值范围在6～9之间。当含水量大于10%时,其乳化油的粘度远高于普通柴油,不适合在柴油机上应用。8.对RBME—水乳化油的燃烧和排放性能进行台架试验研究。试验结果显示乳化油的燃油消耗率略高于0~#柴油,输出功率则低于0~#柴油。如果去除水所占的比例,乳化油的实际油耗比单烧RBME要低,具有一定的节油作用。乳化油的CO、HC、NOx和碳烟颗粒物的排放量均低于普通柴油。9.采用大豆磷脂、Span80、Tween80复配制备RBME—水乳化油。试验结果显示大豆磷脂和其它化学乳化剂配制的复合乳化剂,具有良好的乳化性能,与纯化学复合乳化剂的乳化能力相当,优于单一的化学乳化剂。在HLB值相同情况下,复合乳化剂的组成对乳化能力影响并不明显。同时,大豆磷脂的加入对乳化油的燃料特性并不产生负面影响。综上,利用米糠油制备RBME及其乳化油是可行的。大力发展RBME及其乳化油对发展循环经济和新能源开发,减少环境污染,保护生态环境都具有重大意义。研究工作为加快我国生物柴油的产业化进程,提供了理论与实践基础。更多还原

【Abstract】 Recently,biodiesel has been receiving increasing attention due to its less polluting characteristics and because it is a renewable energy resource as against the conventional diesel,which is a fossil fuel leading to a potential exhaustion.The main hurdle to the commercialization of biodiesel is the cost of raw materials.However,use of cheap and abundant feedstock may result in substantial reduction in the biodiesel production cost.Rice bran is an important by-product in rice processing.The rice contains 6～10 wt%of bran which contains 16～32 wt%oil.Due to the presence of an active lipase in the bran,FFA content in crude rice bran oil is higher compared to the other edible oil.Because of this reason,rice bran oil is not considered as edible oil.Even though the bran produced is used as poultry and cattle feed,to ensure its quality is difficult.Using rice bran oil as feedstock of biodiesel not only gives full play to the advantage in abundant bran resources but also improves the quality of feed.The biodiesel(RBME)was prepared from rice bran oil.The properties of rice bran oil,the technological conditions of transesterification and the preparation process of emulsion fuel were researched.The study on the performance and emissions of the biodiesel and the emulsion fuel was conducted in a DI engine.Main contents of the research were as fallows:1.Physical and chemical characteristics and fatty acid composition of rice bran oil were studied.The study results showed that oleic,linoleic and palmitic acids were three major FA in rice bran oil.Molecular structure of biodesel product was similar to diesel,ideal for alternative fuel substitution. Acid value of the rice bran oil was high,so it needs to deacidfy before making biodiesel. 2.The transesterification of rice bran oil with methanol,in presence of base catalyst,by means of mechanical stirring in order to obtain RBME fuel was studied.The study results showed that the optimal conditions of the conversion rate were:ratio of methanol to oil,6,reaction temperature, 60℃,dosage of catalyst,0.9%,reaction time,45min,but the optimal conditions of the yield rate were:ratio of methanol to oil,6,reaction temperature,50℃,dosage of catalyst,1%,reaction time,45min.The conversion rate and the yield rate were 98.6%and 91.2%,respectively.3.The transesterification of rice bran oil with methanol,in presence of base catalyst,by means of low frequency ultrasound in order to obtain biodiesel fuel was studied.By using ultrasounds the reaction time was much shorter(15～20min)than for mechanical stirring.The quantity of required catalyst is lower than for mechanical stirring.At 40 kHz ultrasounds the reaction time was shorter,but the yields were lower than at 28 kHz.The differences in the product yield were mainly due to difficulties through washing.4.Fuel properties of RBME were studied and compared according to ASTM D6751-02 and DIN V51606 standards for biodiesel.Most fuel properties comply with the limits prescribed in the aforementioned standards.The consequent engine test was shown a similar power output compared with regular diesel,but consumption rate was slightly increased. Emission tests have shown a marked decreasing in CO,HC,and PM, however with a slight increasing in NOx.5.The mutual solubility and the physicochemical properties of the diesel-RBME-ethanol blend fuel were investigated,and the power and fuel economy and emission characteristics of the diesel engine were measured under the condition of burning diesel fuel and the diesel-RBME-ethanol blend fuel.The results showed that the solubility and fuel properties were improved when added RBME in diesel—ethanol blend fuel.But the solubility of blend fuel was not good when the temperature is lower than 0℃.6.The influence of diesel-RBME-ethanol blend fuel oxygen content on diesel engine exhaust emissions was investigated.The CO and HC emissions decreased with the oxygen content increasing when the oxygen content was lower than the oxygen content of RBME.With the content of ethanol increasing,though the oxygen content increased,the CO and HC emissions increased.At all time,with the fuel oxygen content increasing, the NOx emissions continued increased,but the soot emissions continued decreased.7.Using Span80 and Tween80 as emulsifier,the preparation process of RBME-water emulsion fuel were researched.The results showed that the optimal conditions of preparing W/O emulsion fuel were:dosage of emulsifier,0.9%,temperature,30℃,ratio of oil to water,9:1,stirring intensity,3000r/min,mixing time,15min,HLB value,4.The optimal HLB value of preparing O/W/O emulsion fuel was in the range from 6 to 9. When the content of water was over 10%,the viscosity of emulsion fuel was too high to be used in diesel engine.8.The power and fuel economy and emission characteristics of the diesel engine were measured under the condition of burning diesel fuel and the RBME -water emulsion fuel.The consequent engine test was shown a slightly low power output compared with regular diesel,but consumption rate was slightly increased.However,if the 10vol%of water is taken out of the calculation for the consumption,then the emulsion fuel has less consumption than neat RBME.Emission tests have shown a decreasing in CO,HC,soot,and NOx.9.Using Span80,Tween80 and soybean phospholipids as emulsifier, the preparation process of RBME-water emulsion fuel were researched. The compound emulsifier made from soybean phospholipids and chemical synthesis emulsifier has the similar emulsifying capacity with neat chemical compound emulsifier,but has higher emulsifying capacity than the single chemical synthesis emulsifier.When the compound emulsifiers had the same HLB value,the influence of emulsifier type on emulsifying capacity was not marked.As soybean phospholipids been added in emulsion fuel,the negative influence on fuel properties was not found.To sum up,this research showed that it is feasible to prepare biodiesel and emulsion fuel from rice bran oil.The development of making biodiesel from rice bran oil has great practical significance to develop cyclic economy and new energy,ruduce pollution and protect environment.This study gave the theoretic and experimental base to advance the industrialization of biodiesel.更多还原