Optimized conditions for the design and operation of a vacuum distillation column for the purification of crude glycerol from biodiesel production

Abstract

Due to the growth in global demand for biodiesel, there is a tendency for the volume of its main by‐product, glycerol, available on the market to increase. This has led to a search for new uses for this by‐product and the development of new processes that use glycerol as a raw material because it has wide industrial applications. However, to be used in many of these processes, the glycerol must go through a purification stage before reaching the purity required for the application (which can reach 99.7% w/w). Taking this into account, the optimization of the parameters for the main glycerol purification stage (vacuum distillation) is essential to reduce the cost of this stage as much as possible. In this article, optimization of the vacuum distillation column was carried out using an artificial neural network (ANN) and a genetic algorithm (GA) together. With the optimization, it was found that four theoretical stages of equilibrium (separation) is the optimal value, in economics terms, for the distillation column on an industrial scale, leading to better performance (in terms of glycerol purity) than patents that used a smaller number of theoretical stages and an equal performance in relation to the patents that used a greater number of stages, which in this case reduces the cost with the size of the column. This result helps to increase the financially viability of using glycerol as a raw material, which can make several processes cheaper, thus generating greater added value to this sustainable by‐product.

Effects of Assisting Solvents on Purification Efficiency in the Layer Melt Crystallization of Glycerol

“…17, 18 Guardani et al 17 explained the higher effective Table 1. Melting Temperature Predicted by UNIFAC-DMD Model and Measured Viscosity for Systems Consisting of Glycerol [1], DEG [2], 1-Butanol [3], and Acetone [4] Quantified by Mole Fraction distribution coefficient of the crystal layer in static mode crystallization due to the increase in impurity concentration at the solid−liquid interface, as a result of the slow transport of impurities from the interface to the bulk melt.…”

“…Purification of glycerol by distillation requires vacuum operation due to its high boiling point and sensitivity to high temperatures. 3,4 Recent efforts have been focused on optimizing the vacuum distillation process using computational methods to reduce the cost associated with this purification step. 4 Nevertheless, the overall efficiency of purification methods relies on the impurity content of crude glycerol.…”

“…Glycerol can be used as a renewable resource for diverse applications such as pharmaceuticals, cosmetics, and food products, or as a raw material for the production of other chemicals , depending on its grade. Purification of glycerol by distillation requires vacuum operation due to its high boiling point and sensitivity to high temperatures. , Recent efforts have been focused on optimizing the vacuum distillation process using computational methods to reduce the cost associated with this purification step . Nevertheless, the overall efficiency of purification methods relies on the impurity content of crude glycerol.…”

Experimental Scale-Up and Technoeconomic Assessment of Low-Grade Glycerol Purification from Waste-Based Biorefinery

“…5 Industrial process design assessments, supported by experimental evidence of the purification steps, are not available in the literature. Oliveira et al 21 and Braga et al 22 have both simulated the purification of crude glycerol using vacuum distillation with a slight physiochemical pretreatment to achieve a purity of 99.7%. Despite the appreciable attempt to assess the process performance on the industrial scale, Braga et al 22 have assumed a starting purity of 80 wt % with an ash content of 3 wt %, and Oliveira et al 21 have used an initial purity of 50 wt % not including any ash content and a very high methanol content (35 wt %).…”

“…Oliveira et al 21 and Braga et al 22 have both simulated the purification of crude glycerol using vacuum distillation with a slight physiochemical pretreatment to achieve a purity of 99.7%. Despite the appreciable attempt to assess the process performance on the industrial scale, Braga et al 22 have assumed a starting purity of 80 wt % with an ash content of 3 wt %, and Oliveira et al 21 have used an initial purity of 50 wt % not including any ash content and a very high methanol content (35 wt %). Another study from Xiao et al 23 simulated a complex physiochemical purification process to reach purities of up to 94 wt % when neglecting the ash removal step.…”