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

Allan A Albuquerque,Luiz Stragevitch,Maria Fernanda Pimentel,Cícero H M Soares,Cláudia J S Cavalcanti

doi:10.1590/0104-6632.20180352s20160265

Allan A Albuquerque, Luiz Stragevitch + Show 3 more

Open Access

https://doi.org/10.1590/0104-6632.20180352s20160265

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Abstract

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 (wFFAB) and total cost, using yellow and brown greases as the raw materials. Quadratic and linear models were fitted for wFFAB and cost responses, respectively. The optimal conditions satisfying technical (wFFAB ≤ 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, wFFAB = 0.41%, cost = $84.93/ton (yellow grease), and 318 K, 6 stages, S/F = 1.32, wFFAB = 0.49%, cost = $102.89/ton (brown grease).

Highlights

Biodiesel production is usually carried out through a transesterification reaction, which consists of a chemical reaction of a vegetable oil, animal fat or residual oil and fat (ROF) with a short chain alcohol in the presence of a catalyst (Van Gerpen, 2005; Gnanaprakasam et al, 2013)
A rigorous thermodynamic modeling applied to vegetable oil/free fatty acids (FFA)/methanol systems was carried out to represent the liquid-liquid equilibrium (LLE) in the liquid-liquid extraction (LLEx) column
The ROF composition used in the LLEx column was defined based on a mixture of the vegetable oils found in the vegetable oil/FFA/methanol LLE systems available (Batista et al, 1999a; Mohsen-Nia and Dargahi, 2007; Liu et al, 2008; Mohsen-Nia and Khodayari, 2008)

Summary

INTRODUCTION

Biodiesel production is usually carried out through a transesterification reaction, which consists of a chemical reaction of a vegetable oil, animal fat or residual oil and fat (ROF) with a short chain alcohol (methanol or ethanol) in the presence of a catalyst (Van Gerpen, 2005; Gnanaprakasam et al, 2013). Refined vegetable oils are largely employed as raw materials in the biodiesel industry; they can represent up to 85% of biodiesel costs. To increase the production yield, ROF is usually subjected to an initial pretreatment step with an acid-catalyzed esterification reaction; the resulting stream undergoes an alkali-catalyzed transesterification step (Canakci and Van Gerpen, 2001), which is known as the conventional process. Alternative processes employing the FFA separation from the oil have proven to be economically more attractive (Albuquerque et al, 2016). FFA separation can be carried out by liquid-liquid extraction (LLEx) using a short-chain alcohol as the solvent (Bhosle and Subramanian, 2005; Rodrigues et al, 2007; Vaisali et al, 2015), making it a potentially interesting process for the biodiesel industry. 1999); and to attain technical and economic feasibility of the process with a minimum total cost

METHODOLOGY

RESULTS AND DISCUSSION

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CONCLUSIONS