Conceptual design for the extractive distillation of cyclopentane and neohexane using a mixture of N,N-dimethyl formamide and ionic liquid as the solvent

Hydrofluorocarbon refrigerants are being phased out over the next two decades due to their high global warming potential. To separate and recycle refrigerants that form azeotropic mixtures, current distillation methods are inadequate and a new technology is required. Extractive distillation using an ionic liquid as the entrainer offers a solution. Vapor liquid equilibria data for refrigerants difluoromethane (HFC-32), chlorodifluoromethane (HCFC-22), pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and 1,1,1,2-tetrafluoroethane (HFC-134a) in ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2C1im][Tf2N]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([C4C1im][PF6]) were fit with the Peng–Robinson equation of state to simulate the separation of four azeotropic refrigerant mixtures (R-404A, R-407C, R-410A, and R-410A + HCFC-22) and to develop rate-based and equilibrium models in ASPEN Plus. Process flow diagrams were developed and optimized based on a set of physical and chemical constraints. The goal was to optimize the parameters to achieve refrigerant grade (>99.5 wt %) purity. The ionic liquids were found to be effective entrainers for separating refrigerant mixtures.

Section: Simulation Processmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Process Designs for Separating R-410A, R-404A, and R-407C Using Extractive Distillation and Ionic Liquid Entrainers

Finberg

Shiflett

2021

“…Ionic liquids were first introduced as entrainers in 2001 by the BASF Chemical Company and patented in 2004 by Wolfgang Arlt et al , Only two institutions, BASF and Eindhoven University of Technology (EUT), have published details regarding the experimental setup for testing extractive distillation with ILs. However, 33 articles have been published on the simulation of ILs as entrainers for extractive distillation. − Table S3 provides a summary of all of the published material on extractive distillation with IL entrainers, including the (i) components being separated, (ii) IL entrainer, and (iii) thermodynamic model used to predict the equilibrium of the system. Most of these separations were binary systems; however, the italicized labels shown in Table S3 represent multicomponent mixtures.…”

Section: Introductionmentioning

confidence: 99%

Multicomponent Refrigerant Separation Using Extractive Distillation with Ionic Liquids

Finberg

May

Shiflett

2022

Hydrofluorocarbon refrigerants are being phased out over the next two decades due to concerns about high global warming potential. In order to separate refrigerant mixtures that form azeotropes, new technologies will be required. Currently, fractional distillation is unable to efficiently separate azeotropic refrigerant mixtures. Extractive distillation using an ionic liquid as the entrainer offers a solution. Vapor–liquid equilibria data for refrigerants difluoromethane (HFC-32), pentafluoroethane (HFC-125), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane (HFC-143a), chlorodifluoromethane (HCFC-22), propane (HC-290), and isobutane (HC-600a) and ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([C4C1im][PF6]) was regressed using the Peng–Robinson equation of state with the van der Waals 1-parameter mixing rule and Boston–Mathias nonideal correction. Process flow diagrams using ASPEN simulations were prepared for demonstrating how multicomponent mixtures of these refrigerants can be separated. Opportunities for measuring and modeling the solubility of new refrigerants in ionic liquids are discussed, and challenges remain for effectively separating some azeotropic refrigerant mixtures containing hydrofluorocarbons and hydrocarbons.

“…Although many works have addressed the separation of azeotropic mixtures using ILs as entrainers for ED in the past, ,− process synthesis for the determination of optimal process configurations and optimal operating conditions remains a challenge. An ED column consists of many stages where each stage has both liquid and vapor flows that are determined by gas absorption and phase equilibria.…”

Section: Introductionmentioning

confidence: 99%

Separation Process Synthesis for High-GWP Refrigerant Mixtures: Extractive Distillation using Ionic Liquids

Monjur

Iftakher

Hasan

2022

Due to high global warming potential (GWP) of hydrofluorocarbons (HFCs), the separation and recovery of HFCs from different refrigerant mixtures is an important issue. Most HFC mixtures are azeotropic in nature, thereby rendering the conventional distillation-based separation difficult and energy intensive. Extractive distillation (ED) with ionic liquid (IL) as solvent provides an attractive strategy for selective separation of HFC mixtures. However, systematic design and optimization of ED-based separation processes is nontrivial. In this work, we present SPICE_ED which is a software framework for the detailed design, synthesis, and techno-economic analysis of ED-based separation processes. The framework employs a building block representation followed by superstructure optimization that is able to automatically generate numerous design solutions and screen the best without requiring prior expert knowledge of candidate configurations. For a given IL as solvent and a set of design specifications, one can automatically determine the feasibility of the solvent and obtain the optimal process flowsheets that correspond to minimum energy consumption, minimum separation cost, or minimum emission/waste. We demonstrate the capability of SPICE_ED for the separation of R-410A (50 wt % R-32 and 50 wt % R-125) using [bmim][PF 6 ], a commonly used IL. Our optimized design requires an equivalent work of only 338.2 kJ/kg R-410A, which is about 48% less than the previously reported value of 656 kJ/kg. The newly identified design also achieves more than 47% and 27% reductions in CO 2 -equivalent emission (sustainability) and cost, respectively. Through multiobjective optimization, we further identify an operating regime to separate R-410A at a near-minimum cost without significantly increasing the energy consumption and emission. The processes obtained from SPICE_ED show excellent agreement with the key performance metrics when simulated in Aspen Plus, thereby establishing confidence in our designs as realistic and implementable.