Splitting Triglycerides with a Counter-Current Liquid–Liquid Spray Column: Modeling, Global Sensitivity Analysis, Parameter Estimation and Optimization

Abstract

In this work we present the model of a counter-current spray column in which a triglyceride (tripalmitic triglyceride) is hydrolyzed by water and leads to fatty acid (palmitic acid) and glycerol. A finite volume model (FVM) of the column was developed to describe the reactive extraction process with a two-phase system and validated with an analytical model from the literature with the given data set encompassing six experimental runs. Global, variance-based (Sobol) sensitivity analysis allowed assessment of the sensitivity of the sweet water glycerol content in respect to liquid density, overall mass-transfer coefficient, reaction rate coefficient and the equilibrium ratio to rank them accordingly. Furthermore, parameter estimation with a differential evolution (DE) algorithm was performed to obtain among others the mass transfer, backmixing and reaction rate coefficients. The model was used to formulate and solve a process design problem regarding economic and sustainable performance. Multi-criteria optimization was applied via DE to minimize total annual cost (TAC) and the Eco99 indicator by varying the steam inlet flow rate and distribution over the two steam inlets as the independent variables. The model and analysis was implemented in Fortran and Python where the Fortran model can also be embedded in a process simulator such as PRO/II or Aspen.

Multivariate Analysis of Industrial Biorefinery Processes: Strategy for Improved Process Understanding with Case Studies in Fatty Acid Production

“…Existing mechanistic models for fat/oil hydrolysis don't include side reactions such as the breakdown of C18:3 and use simplified compositions, such as one fatty acid and glyceride component. 29,30 This study has shown the importance of differentiating between feedstock types, which underlines the importance of using a more specific composition if modelling is used to optimize process parameters. Existing models of fatty acid distillation focus on the vapour-liquid equilibrium (VLE) of fatty acids and don't include quality parameters such as colour.…”

Iterative lumping approach for representing lipid feedstocks in fatty acid distillation simulation and optimization

“…This first iteration thereby represents the case where all FAs are lumped and represented by one and the same key compound, a lumping scheme often seen in literature. [13][14][15] The compounds with highest wt% in the feedstock are chosen as key compound for the lump of FFA and glyceridic compounds, being oleic acid (42.0 ± 0.7 wt%) and monoolein (0.45 ± 0.26 wt%). For the lump minor compounds, butyric acid is chosen as key compound due to the availability of physical property data for this pure compound and mixtures with FFA.…”

“…Most frequently, all FAs were lumped and represented by one key compound for the whole range of carbon chain length and saturation. Kiss, 13 for example, used solely lauric acid to represent all FAs, while Tehlah et al 14 used oleic acid and Jones et al 15 used palmitic acid. This approach accelerates initial model building and limits the amount of property data required.…”

“…However, for this example, by starting with a simple initial lumping scheme, the ability of the iterative lumping approach to guide toward an optimal set of key compounds is demonstrated, even when starting from a very limited set of initial lumps. This first iteration thereby represents the case where all FAs are lumped and represented by one and the same key compound, a lumping scheme often seen in literature 13‐15 . The compounds with highest wt% in the feedstock are chosen as key compound for the lump of FFA and glyceridic compounds, being oleic acid (42.0 ± 0.7 wt%) and monoolein (0.45 ± 0.26 wt%).…”

Simulation of an Industrial-Scale Reactive Liquid–Liquid Extraction Tower Using Polar PC-SAFT Toward Understanding and Improving the Hydrolysis of Triglycerides

“…In other fields, process modelling has been used for optimization of processes with a variable feedstock, for example, in the biodiesel industry . However, modelling research on fatty acid production is scarce . This motivates developing a process model of triglyceride hydrolysis to investigate the optimal processing parameters for different renewable feedstock types.…”