University of Johannesburg, Department of Mechanical Engineering Science, PO Box 17011, Doornfontein 2028, Johannesburg, South Africa.
Waste Manag. 2013 Jun;33(6):1509-15. doi: 10.1016/j.wasman.2013.02.014. Epub 2013 Mar 11.
This study investigated the recovery of oil from waste grease through the process of thermal degradation in an aqueous solution of potassium hydroxide (KOH) followed by solvent extraction. Waste high temperature metal bearing grease was dissolved in a 15 w/w% KOH solution at 80°C while being agitated at 2000 rpm using a shear action agitator for a period of 15 min. Two distinct layers were observed after 8 min of settling time. The top layer being of dark brown oil and the bottom layer was a heterogeneous mixture. The two layers were separated by decantation. The bottom layer was cooled down to 45°C followed by slow addition of toluene (C7H8) while agitating at 1200 rpm for 15 min to prevent solids settling and minimise rapid volatilisation of the organic compounds in the mixture. Two distinct layers were also formed, the top homogeneous mixture of light brown oil-toluene mixture and the bottom sludge layer. The solvent was recovered from the oil for re-use by fractional distillation of the homogenous mixture. It was observed that 15 w/w% potassium hydroxide solution can chemically degrade the soap matrix in the grease and extract up to 49 w/w% of the fuel oil when subjected to high shear stress at a temperature of 80°C. The 26 w/w% extraction of oil in the remaining sludge was obtained by solvent extraction process with mass ratios of sludge to solvent of 2:1. Solvent recovery of 88% by mass was obtained via fractional distillation method. The combined extraction processes brought an overall oil yield of 75 w/w% from the waste grease. The fuel oil obtained from this process has similar properties to paraffin oil and can be blended with other oils as an alternative energy source.
本研究通过在氢氧化钾（KOH）水溶液中进行热降解，然后进行溶剂萃取的方法，从废油脂中回收油。将废高温金属轴承油脂在 80°C 的 15 w/w% KOH 溶液中溶解，同时在 2000 rpm 的搅拌速度下使用剪切作用搅拌器搅拌 15 分钟。在 8 分钟的沉降时间后观察到两层明显的分层。上层是深棕色的油，下层是不均匀的混合物。通过倾析将两层分离。将下层冷却至 45°C，然后缓慢加入甲苯（C7H8），同时在 1200 rpm 的搅拌速度下搅拌 15 分钟，以防止固体沉降并最大限度地减少混合物中有机化合物的快速挥发。也形成了两层，上层是浅棕色油-甲苯混合物的均相混合物，下层是污泥层。通过对均相混合物进行分馏回收溶剂以重新使用。观察到 15 w/w%氢氧化钾溶液可以在 80°C 的高温和高剪切应力下化学降解油脂中的肥皂基质，并从油脂中提取高达 49 w/w%的燃料油。通过溶剂萃取过程从剩余污泥中获得 26 w/w%的油萃取，其中污泥与溶剂的质量比为 2:1。通过分馏法获得 88%的溶剂回收率。通过组合萃取工艺，从废油脂中获得了 75 w/w%的总油收率。从这个过程中获得的燃料油具有与石蜡油相似的性质，可以与其他油混合作为替代能源。
