Iván D. Gil

Control of an extractive distillation process to dehydrate ethanol using glycerol as entrainer

Abstract In this paper, an investigation of the design and control of an extractive distillation process to produce anhydrous ethanol using glycerol as entrainer is reported. The extractive distillation process receives the azeotropic mixture ethanol–water that is fed into a dehydration column in one of the intermediate stages while at the same time glycerol is fed into one of the top stages. As overhead product high purity ethanol is withdrawn and in the bottom stream a mixture of water/glycerol is sent to a recovery column. The effects of the entrainer to feed molar ratio, reflux ratio, feed stage, feed entrainer stage and entrainer feed temperature were studied to obtain the best design with minimal energy requirements. A control scheme is developed in order to maintain stable operation for large feed disturbances. Dynamic simulations show that is possible to use only one temperature control to hold the purity specifications.

Separation of ethanol and water by extractive distillation with salt and solvent as entrainer: process simulation

The aim of this work is to simulate and analyze an extractive distillation process for azeotropic ethanol dehydration with ethylene glycol and calcium chloride mixture as entrainer. The work was developed with Aspen Plus® simulator version 11.1. Calculation of the activity coefficients employed to describe vapor liquid equilibrium of ethanol - water - ethylene glycol - calcium chloride system was done with the NRTL-E equation and they were validated with experimental data. The dehydration process used two columns: the main extractive column and the recovery column. The solvent to feed molar ratio S/F=0.3, molar reflux ratio RR=0.35, number of theoretical stages Ns=18, feed stage Sf=12, feed solvent stage SS=3, and feed solvent temperature TS=80 oC, were determined to obtain a distillate with at least 99.5 % mole of ethanol. A substantial reduction in the energy consumption, compared with the conventional processes, was predicted by using ethylene glycol and calcium chloride as entrainer.

Simulation and pre-feasibility analysis of the production process of α-methyl ester sulfonates (α-MES)

alpha-Methyl esters sulfonates (alpha-MES) are anionic surfactants that are derived from biorenewable resources, offering interesting environmental and chemical properties for application in the detergent industry. A simulation of their production process was conducted using a commercial production process currently used for palm oil. Results, prices of raw materials were submitted to economic analysis, and final MES price was compared with available data for linear alkyl benzene sulfonates (LAS) prices. The results for substances properties and product streams obtained from simulation were reliable in agreement to real values. It was found that increasing methyl ester national price by 20%, 50% and the equivalent to linear alkyl benzene price, the final price of alpha-methyl ester sulfonates was lower than the current price of linear alkyl benzene sulfonates. The capital cost and payout period for a production capacity of 49,000tons of surfactant per year were obtained. Results indicate that the process is economically feasible and can be applied to palm oil-based industries in Colombia.

Simulation of ethanol extractive distillation with mixed glycols as separating agent

Extractive distillation is an alternative for ethanol dehydration processes that has been shown to be more effective than azeotropic distillation and, in close proximity, to be very competitive against the process that uses adsorption with molecular sieves. Glycols have been shown to be the most effective solvents in extractive distillation, mainly ethylene glycol and glycerol. In this work, an extractive distillation column was simulated with the Aspen Plus software platform, using the RadFrac module for distillation columns, to investigate the effect on the separation of the ethylene glycol-glycerol mixture composition, the separating agent feed stages, the separating agent split stream feed, and the azeotropic feed temperature. The NRTL model was used to calculate the phase equilibrium of these strongly polar mixtures. A rigorous simulation of the extractive distillation column finally established was also performed, including a secondary recovery column for the mixture of solvents and a recycle loop, to simulate an industrially relevant situation. This simulation allowed establishing the complete parameters to dehydrate ethanol: the optimal stage for separating agent feed is stage 4; the most adequate composition for the glycols mixture is 60 mol% ethylene glycol and 40 mol% glycerol. Finally, energetically efficient operating conditions for each one of the columns were established through a preliminary pinch analysis.

Using process simulators in the study, design, and control of distillation columns for undergraduate chemical engineering courses

Nowadays high schools should teach students how to use the software that they will use at work. This article shows the importance to promote a closer relationship between the engineering computer programs offered by companies like Aspen Technology Inc., and the chemical engineering students. The methodology consists of creating a tutorial which illustrates, in an interesting way, subjects through engineering software packages. The main theme treated in this tutorial is distillation column simulation and design; it also includes a brief look into distillation column control by means of dynamic simulations. This article presents an interactive guide with three case studies, where the subjects of design and control for a binary simple system and the development of a simulation for a complex ternary system are studied. These guides were implemented in Separation Processes and Process Design courses and the guide evaluation results show an acceptance by the students.

Dynamic Simulation and Optimisation of an Industrial Process for Tributyl Citrate Production

Abstract Demand of free-phthalate plasticizers has increased due to the concern about the negative effect that phthalate compounds could have on the human health, and because the market trends have been pushing for bio-based products consumption. Tributyl citrate has been identified as a functional alternative for phthalate plasticizers, however there are still challenges regarding the industrial production in a semi-batch process, mainly associated with large excess of reactants, high energy and processing costs. In order to improve the process performance, this work developed a dynamic model a reaction-separation process, which was contrasted with industrial data and optimized using gPROMS®.