Separating azeotropic mixtures of hydrofluorocarbons (HFCs) for reuse and recycle is environmentally and economically imperative. While ionic liquid (IL)-enabled HFC separations show promise, Edisonian trial-and-error screening for the optimal IL entrainer is intractable and expensive. Here, we propose an open-source, equation-oriented modeling framework to rapidly translate HFC/IL solubility data into regressed thermodynamic models which can be used for process design under uncertainty and rapid IL screening. Moreover, we use data science and process systems engineering tools to contemplate which data are the most valuable for IL screening. We find that binary solubility data collected at multiple temperatures is adequate for separation process design, and newly available ternary solubility measurements should be reserved for validation. Additionally, we use uncertainty quantification analyses to show up to 10% experimental error is acceptable for IL screening decisions. Informed by these results, we recommend a multistep workflow for IL screening.
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Modeling and Optimization of Ionic Liquid Enabled Extractive Distillation of Ternary Azeotrope Mixtures
To help slow climate change, international efforts have begun to mandate the phase-out of high global warming potential (GWP) hydrofluorocarbons (HFCs) throughout the next decade. Most HFC refrigerant mixtures form azeotropes, complicating separation into the individual HFC components for reuse and recycling. In this paper, we design and analyze ionic liquid (IL)-enabled extractive distillation processes for ternary HFC separations using AspenPlus. Specifically, we design processes to separate three commercially important HFC refrigerant mixtures (R-404A, R-407C, and R-410A) into high purity HFC streams. We find added value of the separation of R-410A of 0.58 $/kg with current market conditions, specifically laboratory-scale IL manufacturing costs (1000 $/kg of IL) and a low-price differential of 1.00 $/kg between raw materials and separated products. If the IL purchase cost decreases 90 % due to mass production, consistent with prior adoption of ILs for niche separations, the added value increases to 0.76 $/kg. Moreover, under proposed reductions in HFC manufacturing, the price of recovered products may dramatically increase in the future. For example, if the price of R-32 increases by 50 %, the added value would reach 3.08 $/kg. In summary, we find IL-based recycling of HFCs is economically viable based on simple technoeconomic analysis. Moreover, this paper reports capital and operation cost curves and a general analysis framework to analyze evolving market conditions.
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- Award ID(s):
- 1917474
- NSF-PAR ID:
- 10403698
- Editor(s):
- Yamashita, Y.; Kano, M.
- Date Published:
- Journal Name:
- Computer aided chemical engineering
- Volume:
- 49
- ISSN:
- 2543-1331
- Page Range / eLocation ID:
- 307-312
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Separating azeotropic mixtures of hydrofluorocarbons (HFCs) for reuse and recycle is environmentally and economically imperative. While ionic liquid (IL)-enabled HFC separations show promise, Edisonian trial-and-error screening for the optimal IL entrainer is intractable and expensive. Here, we propose an open-source, equation-oriented modeling framework to rapidly translate HFC/IL solubility data into regressed thermodynamic models which can be used for process design under uncertainty and rapid IL screening. Moreover, we use data science and process systems engineering tools to contemplate which data are the most valuable for IL screening. We find that binary solubility data collected at multiple temperatures is adequate for separation process design, and newly available ternary solubility measurements should be reserved for validation. Additionally, we use uncertainty quantification analyses to show up to 10% experimental error is acceptable for IL screening decisions. Informed by these results, we recommend a multistep workflow for IL screening.more » « less
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null (Ed.)Growing concerns about the global warming potential of hydrofluorocarbons (HFCs) has led to increasing interest in developing technologies to effectively recover and recycle these refrigerants. Ionic liquids (ILs) have shown great potential to selectively separate azeotropic HFC gas mixtures, such as R-410A composed of HFC-32 (CH2F2) and HFC-125 (CHF2CF3), based on solubility differences between the refrigerant gases in the respective IL. Isothermal vapor−liquid equilibrium (VLE) data for HFC-32 and HFC-125 were measured in ILs containing fluorinated and nonfluorinated anions using a gravimetric microbalance at pressures ranging from 0.05 to 1.0 MPa and a temperature of 298.15 K. The van der Waals equation of state (EoS) model was applied to correlate the experimental solubility data of each HFC refrigerant/IL mixture. The solubility differences between HFC-32 and HFC-125 vary significantly depending on the choice of IL. The diffusion coefficients for both HFC refrigerants in each IL were calculated by fitting Fick’s law to time-dependent absorption data. HFC-32 has a higher diffusivity in most ILs tested because of its smaller molecular radius relative to HFC-125. Based on the calculated Henry’s law constants and the mass uptake for each system, [C6C1im][Cl] was found to have the highest selectivity difference for separating R-410A at 298.15 K.more » « less
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null (Ed.)Growing concerns about the global warming potential (GWP) of hydrofluorocarbons (HFCs) has led to increasing interest in developing technologies to effectively recover and recycle these refrigerants. Ionic liquids (ILs) have shown great potential to selectively separate azeotropic HFC gas mixtures such as R-410A composed of HFC-32 (CH2F2) and HFC-125 (CHF2CF3), based on solubility differences between the refrigerant gases in the respective IL. Isothermal vapor−liquid equilibrium (VLE) data for HFC-32 and HFC-125 were measured in ILs containing fluorinated and non-fluorinated anions using a gravimetric microbalance at pressures ranging from 0.05 to 1.0 MPa and a temperature of 298.15 K. The van der Waals Equation of State (EoS) model was applied to correlate the experimental solubility data of each HFC refrigerant / IL mixture. The solubility differences between HFC-32 and HFC-125 vary significantly depending on the choice of IL. The diffusion coefficients for both HFC refrigerants in each IL were calculated by fitting Fick’s law to time-dependent absorption data. HFC-32 has a higher diffusivity in most ILs tested due to its smaller molecular radius relative to HFC-125. Based on the calculated Henry’s law constants and the mass uptake for each system, the [C6C1im][Cl] was found to have the highest selectivity difference for separating R-410A at 298.15 K.more » « less
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Accepted Manuscript1.0
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- The DOI is not currently available.
