OPTIMIZATION OF THE EXTRACTION OF FREE FATTY ACIDS APPLIED TO BIODIESEL PRODUCTION

Abstract The liquid-liquid extraction of free fatty acids (FFA) from residual oils and fats for biodiesel production, employing methanol as the solvent, has been optimized using process simulation and response surface methodology. The parameters investigated were temperature, number of stages and solvent-to-feed ratio (S/F). Responses evaluated were FFA mass fraction in the oil-rich phase ( w FFA B) and total cost, using yellow and brown greases as the raw materials. Quadratic and linear models were fitted for w FFA B and cost responses, respectively. The optimal conditions satisfying technical ( w FFA B ≤ 0.5%) and economic (minimum cost, including capital and operation costs, except for raw material cost) criteria were 321 K, 6 stages, S/F = 1.27, w FFA B = 0.41%, cost = $84.93/ton (yellow grease), and 318 K, 6 stages, S/F = 1.32, w FFA B = 0.49%, cost = $102.89/ton (brown grease).

摘要 以甲醇为溶剂，从用于生物柴油生产的残留油脂中液液萃取游离脂肪酸（free fatty acids, FFA）的工艺，已通过流程模拟与响应面法完成优化。本次研究考察的工艺参数包括反应温度、萃取级数以及溶剂与进料比（S/F）；评估的响应指标为富油相中的FFA质量分数（w FFA B）与总成本。研究采用黄色油脂与棕色油脂作为原料。分别针对FFA质量分数与总成本响应指标，拟合得到二次模型与线性模型。满足技术指标（FFA质量分数≤0.5%）与经济指标（总成本最低，包含建设成本与运营成本，原材料成本除外）的最优工艺条件为：针对黄色油脂，最优工艺参数为321 K、6级萃取、S/F=1.27，此时FFA质量分数为0.41%，总成本为84.93美元/吨；针对棕色油脂，最优工艺参数为318 K、6级萃取、S/F=1.32，此时FFA质量分数为0.49%，总成本为102.89美元/吨。