ChemEngineering

12 pages, 4142 KiB

Open AccessArticle

Drying Technology Assisted by Nonthermal Pulsed Filamentary Microplasma Treatment: Theory and Practice

by Ivan Shorstkii and Evgeny Koshevoi

ChemEngineering 2019, 3(4), 91; https://doi.org/10.3390/chemengineering3040091 - 02 Dec 2019

Cited by 10 | Viewed by 2556

Nonthermal pulsed filamentary microplasma treatment for drying is a nonthermal technology with promising perspectives to dehydrate plant agricultural materials. The modified set of Luikov’s equations for heat, mass and pressure transfer, has been used to analyze nonthermal pulsed filamentary microplasma treatment effects. The [...] Read more.

Nonthermal pulsed filamentary microplasma treatment for drying is a nonthermal technology with promising perspectives to dehydrate plant agricultural materials. The modified set of Luikov’s equations for heat, mass and pressure transfer, has been used to analyze nonthermal pulsed filamentary microplasma treatment effects. The finite element method in combination with the step-by-step finite-difference method for a coupled system of differential equations in partial derivatives was used for numerical simulation of heat, humidity and pressure potentials transfer. The drying time of samples treated by nonthermal pulsed filamentary microplasma treatment assisted by thermionic emission was reduced up to 20.6% (5 kV/cm; 1200 discharges) in comparison to intact tissue. The effect of the obtained approach is very useful for studying process mechanisms and for explaining nonthermal pulsed filamentary microplasma treatment effects. Refined transfer kinetic coefficients from a set of equations based on experimental drying curve can be used for the quantitative determination of thermodynamic coefficients. The agreement of the simulation data with the analytical equation and experimental results is satisfactory (discrepancy less than 3%). Obtained results showed that the proposed model with the refined transfer kinetic coefficients adequately describe the experimental data. Full article

(This article belongs to the Special Issue Selected papers from the Third Nordic Baltic Drying Conference (NBDC 2019))

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9 pages, 1255 KiB

Open AccessArticle

Dissolution of Chitin in Deep Eutectic Solvents Composed of Imidazolium Ionic Liquids and Thiourea

by Satoshi Idenoue, Kazuya Yamamoto and Jun-ichi Kadokawa

ChemEngineering 2019, 3(4), 90; https://doi.org/10.3390/chemengineering3040090 - 02 Dec 2019

Cited by 20 | Viewed by 4360

Abstract

Chitin is an abundant organic resource but shows poor solubility, leading to difficulty in utilization as materials. We have already reported that an ionic liquid (IL), 1-allyl-3-methylimidazolium bromide, dissolves chitin at concentrations up to ca. 5 wt %. However, the color of the [...] Read more.

Chitin is an abundant organic resource but shows poor solubility, leading to difficulty in utilization as materials. We have already reported that an ionic liquid (IL), 1-allyl-3-methylimidazolium bromide, dissolves chitin at concentrations up to ca. 5 wt %. However, the color of the resulting solution is blackened, mainly owing to the presence of bromide. On the other hand, some deep eutectic solvents (DESs) have been already reported to dissolve chitin. In this study, we found that DESs composed of imidazolium ILs and thiourea dissolved chitin without obvious coloring. DESs are systems formed from eutectic mixtures of hydrogen bond accepters and donors. We first prepared DESs by heating mixtures of imidazolium ILs with thiourea at 100 °C for 30 min with stirring. Predetermined amounts of chitin were then added to the DESs, and for the dissolution, the mixtures were left standing at room temperature for 24 h, followed by heating at 100 °C for 24 h with stirring. The dissolution processes were evaluated by CCD camera views, which revealed in most cases the dissolution of chitin at 2–5 wt % concentrations with the present DESs. Full article

(This article belongs to the Special Issue Advanced Ionic Liquid-Based Mixed Solvent Systems)

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19 pages, 3432 KiB

Open AccessArticle

Effect of Chain Length and Functional Group of Organic Anions on the Retention Ability of MgAl- Layered Double Hydroxides for Chlorinated Organic Solvents

by Karen Maria Dietmann, Tobias Linke, Raquel Trujillano and Vicente Rives

ChemEngineering 2019, 3(4), 89; https://doi.org/10.3390/chemengineering3040089 - 28 Nov 2019

Cited by 11 | Viewed by 2661

Abstract

Nowadays, the contamination of groundwater and soils by chlorinated organic solvents is a severe and worldwide problem. Due to their swelling properties, Layered Double Hydroxides (LDHs) are potentially excellent compounds to retain chlorinated organic solvents from aquifers. By intercalating organic anions, the polarity [...] Read more.

Nowadays, the contamination of groundwater and soils by chlorinated organic solvents is a severe and worldwide problem. Due to their swelling properties, Layered Double Hydroxides (LDHs) are potentially excellent compounds to retain chlorinated organic solvents from aquifers. By intercalating organic anions, the polarity of the interlayer space can be changed from hydrophilic to hydrophobic, enhancing the adsorption of chloro-organic molecules onto the alkyl chains of intercalated organic anions. In this study, organically modified LDHs were synthesized and their efficiency was tested in batch experiments with three different chlorinated organic solvents, namely trichloroethylene, 1,1,2-trichloroethane and trichloromethane (chloroform), to examine the influence of the chain length and the functional group of the intercalated organic anion upon the retention ability of a LDH due to different electronic interactions and different sizes of the interlayer space. All synthesized and used samples were characterized using powder X-ray diffraction, thermal analysis coupled with mass spectrometry and Fourier-transform infrared spectroscopy; freshly synthesized materials were additionally analyzed regarding their particle size distribution and specific surface area. Results of the batch experiments showed that only LDHs with intercalated long-chain organic anions could be efficient adsorbents for the removal of chlorinated organic solvents from contaminated water. A selective efficiency towards 1,1,2-trichloroethane and trichloromethane can be proposed for these reactants. Full article

(This article belongs to the Special Issue Advanced Applications of Layered Double Hydroxides)

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16 pages, 3112 KiB

Open AccessFeature PaperArticle

Performance Evaluation of a Small-Scale Latent Heat Thermal Energy Storage Unit for Heating Applications Based on a Nanocomposite Organic PCM

by Maria K. Koukou, George Dogkas, Michail Gr. Vrachopoulos, John Konstantaras, Christos Pagkalos, Kostas Lymperis, Vassilis Stathopoulos, George Evangelakis, Costas Prouskas, Luis Coelho and Amandio Rebola

ChemEngineering 2019, 3(4), 88; https://doi.org/10.3390/chemengineering3040088 - 01 Nov 2019

Cited by 10 | Viewed by 3369

Abstract

A small-scale latent heat thermal energy storage (LHTES) unit for heating applications was studied experimentally using an organic phase change material (PCM). The unit comprised of a tank filled with the PCM, a staggered heat exchanger (HE) for transferring heat from and to [...] Read more.

A small-scale latent heat thermal energy storage (LHTES) unit for heating applications was studied experimentally using an organic phase change material (PCM). The unit comprised of a tank filled with the PCM, a staggered heat exchanger (HE) for transferring heat from and to the PCM, and a water pump to circulate water as a heat transfer fluid (HTF). The performance of the unit using the commercial organic paraffin A44 was studied in order to understand the thermal behavior of the system and the main parameters that influence heat transfer during the PCM melting and solidification processes. The latter will assist the design of a large-scale unit. The effect of flow rate was studied given that it significantly affects charging (melting) and discharging (solidification) processes. In addition, as organic PCMs have low thermal conductivity, the possible improvement of the PCM’s thermal behavior by means of nanoparticle addition was investigated. The obtained results were promising and showed that the use of graphite-based nanoplatelets improves the PCM thermal behavior. Charging was clearly faster and more efficient, while with the appropriate tuning of the HTF flow rate, an efficient discharging was accomplished. Full article

(This article belongs to the Special Issue Advanced Heat Exchangers for Waste Heat Recovery Applications)

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11 pages, 1695 KiB

Open AccessArticle

Clean Hydrogen and Ammonia Synthesis in Paraguay from the Itaipu 14 GW Hydroelectric Plant

by Massimo Rivarolo, Gustavo Riveros-Godoy, Loredana Magistri and Aristide F. Massardo

ChemEngineering 2019, 3(4), 87; https://doi.org/10.3390/chemengineering3040087 - 01 Nov 2019

Cited by 29 | Viewed by 21525

Abstract

This paper aims at investigating clean hydrogen production from the large size (14 GW) hydroelectric power plant of Itaipu, located on the border between Paraguay and Brazil, the two countries that own and manage the plant. The hydrogen, produced by a water electrolysis [...] Read more.

This paper aims at investigating clean hydrogen production from the large size (14 GW) hydroelectric power plant of Itaipu, located on the border between Paraguay and Brazil, the two countries that own and manage the plant. The hydrogen, produced by a water electrolysis process, is converted into ammonia through the well-known Haber-Bosch process. Hydraulic energy is employed to produce H₂ and N₂, respectively, from a large-scale electrolysis system and an air separation unit. An economic feasibility analysis is performed considering the low electrical energy price in this specific scenario and that Paraguay has strong excess of renewable electrical energy but presents a low penetration of electricity. The proposal is an alternative to increase the use of electricity in the country. Different plant sizes were investigated and, for each of them, ammonia production costs were determined and considered as a term of comparison with traditional ammonia synthesis plants, where H₂ is produced from methane steam reforming and then purified. The study was performed employing a software developed by the authors’ research group at the University of Genoa. Finally, an energetic, environmental, and economic comparison with the standard production method from methane is presented. Full article

(This article belongs to the Special Issue 2019 HYPOTHESIS XIV)

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16 pages, 4760 KiB

Open AccessArticle

Effect of Pyrolysis Temperature on the Electrical Property and Photosensitivity of a PAN-PMMA Derived Carbon Fiber

by Tyler Xu, Antonino Nguyen, Noe Rosas, Isidro Flores, Cindy Chen, Jeremy B. Gan, Anan S. Hamdan and Yong X. Gan

ChemEngineering 2019, 3(4), 86; https://doi.org/10.3390/chemengineering3040086 - 01 Nov 2019

Cited by 5 | Viewed by 5108

Abstract

Fibers are promising materials being utilized in electronics, principally in the areas of capacitors and sensors. In this study, we examine the effect of pyrolysis temperature on the electrical conductive behavior and photosensitivity of a carbon-based fiber, which was made by electrospinning a [...] Read more.

Fibers are promising materials being utilized in electronics, principally in the areas of capacitors and sensors. In this study, we examine the effect of pyrolysis temperature on the electrical conductive behavior and photosensitivity of a carbon-based fiber, which was made by electrospinning a polymer solution containing polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and dimethylformamide (DMF). Converting the polymeric fiber into a carbon fiber was performed through the controlled pyrolysis during which oxidation, stabilization, and carbonization happened. After oxidation at an elevated temperature, the linear polymer fiber was stabilized to have a backbone structure. Then the oxidized fiber was treated in an even higher temperature range to be partially carbonized under the protection of argon gas. We utilized multiple samples of the fibers treated at various pyrolysis temperatures inside a heat furnace and examined the effects of the temperatures on the properties. The partially carbonized fiber is highly active in view of electron generation under photon energy excitation. The unique electrical and photovoltaic property are due to their semiconducting behavior. The morphology of the specimen before and after the pyrolysis was examined using scanning electron microscopy (SEM). The SEM images displayed the shrinkage of the fiber due to the pyrolysis. There are two stages of pyrolysis kinetics. Stage I is related to the oxidation of the PAN polymer. Stage II is associated with the carbonization and the activation energy of carbonization is calculated as 118 kJ/mol. Full article

(This article belongs to the Special Issue Carbon-Based Materials and Their Electrochemical Applications)

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20 pages, 1988 KiB

Open AccessArticle

An Engineering Toolbox for the Evaluation of Metallic Flow Field Plates

by Uwe Reimer, Dieter Froning, Gert Nelissen, Leonard F. J. M. Raymakers, Shidong Zhang, Steven B. Beale and Werner Lehnert

ChemEngineering 2019, 3(4), 85; https://doi.org/10.3390/chemengineering3040085 - 11 Oct 2019

Cited by 6 | Viewed by 3330

Abstract

Metallic flow field plates, also called bipolar plates, are an important component of fuel cell stacks, electrolyzers, hydrogen purification and compression stacks. The manufacturing of these plates by means of stamping or hydroforming is highly suitable for mass production. In this work, a [...] Read more.

Metallic flow field plates, also called bipolar plates, are an important component of fuel cell stacks, electrolyzers, hydrogen purification and compression stacks. The manufacturing of these plates by means of stamping or hydroforming is highly suitable for mass production. In this work, a toolbox is created that is suitable for a screening process of different flow field design variants. For this purpose, the geometry and computational mesh are generated in an automated manner. Basic building blocks are combined using the open source software SALOME, and these allow for the construction of a large variant of serpentine-like flow field structures. These geometric variants are evaluated through computational fluid dynamics (CFD) simulations with the open source software OpenFOAM. The overall procedure allows for the screening of more than 100 variants within one week using a standard desktop computer. The performance of the flow fields is evaluated on the basis of two parameters: the overall pressure difference across the plate and the relative difference of the hydrogen concentration at the outlet of the channels. The results of such a screening first provide information about optimum channel geometry and the best choice of the general flow field layout. Such results are important at the beginning of the design process, as the channel geometry has an influence on the selection of the metal for deep drawing or hydroforming processes. Full article

(This article belongs to the Special Issue 2019 HYPOTHESIS XIV)

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9 pages, 3859 KiB

Open AccessArticle

Preliminary Study on the Application of Concentrated Solar Power in Metallurgy of Titanium

by Jaroslav Kováčik, Natália Mináriková, Tomáš Dvorák, Jose Rodríguez, Inmaculada Cañadas, Klaled Saleh Al-Athel, Peter Šugár, Jana Šugárová and Štefan Emmer

ChemEngineering 2019, 3(4), 84; https://doi.org/10.3390/chemengineering3040084 - 10 Oct 2019

Cited by 3 | Viewed by 2809

Abstract

The applicability of concentrated solar power for metallurgy of titanium is discussed based on preliminary experimental works performed at Plataforma Solar de Almeria Spain, using solar furnace SF40 under protective argon atmosphere. As a starting material, titanium powder was used. The possibility of [...] Read more.

The applicability of concentrated solar power for metallurgy of titanium is discussed based on preliminary experimental works performed at Plataforma Solar de Almeria Spain, using solar furnace SF40 under protective argon atmosphere. As a starting material, titanium powder was used. The possibility of melting titanium compacts on yttria stabilized zirconia mat was investigated, and the effect of density and size of different green compacts was studied. It was observed that the time to achieve melting point is very short when concentrated solar power is used. The obtained results are expected to be similar for titanium sponge from which titanium powder is processed. After optimization of processing parameters, this will probably lead to a significant decrease of carbon footprint in the titanium ingots and castings production. Full article

(This article belongs to the Special Issue Concentrated Solar Energy for Materials)

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19 pages, 3095 KiB

Open AccessReview

Solar Heat for Materials Processing: A Review on Recent Achievements and a Prospect on Future Trends

by Luís Guerra Rosa

ChemEngineering 2019, 3(4), 83; https://doi.org/10.3390/chemengineering3040083 - 08 Oct 2019

Cited by 23 | Viewed by 6043

Abstract

Considering works published in the literature for more than a decade (period from January 2008 till June 2019), this paper provides an overview of recent applications of the so-called “solar furnaces”, their reactors, process chambers and related devices, aiming specifically at the processing [...] Read more.

Considering works published in the literature for more than a decade (period from January 2008 till June 2019), this paper provides an overview of recent applications of the so-called “solar furnaces”, their reactors, process chambers and related devices, aiming specifically at the processing of (solid) materials. Based on the author’s own experience, some prospects on future trends are also presented. The aim of this work is to demonstrate the tremendous potentialities of the usage of solar heat for materials processing, but also to reveal the necessity of further developing solar-driven high-temperature technologies (which are required to displace the use of electricity or natural gas). In particular, it is essential to improve the temperature homogeneity conditions inside reaction chambers for materials processing using solar heat. Moreover, new innovative modular systems, practical and flexible, for capture, concentration, control and conduction of concentrated solar radiation are suggested. Solar thermal technologies for the production of electricity, as well as solar thermochemical processes for production of gases or liquids, are outside the scope of this review. Full article

(This article belongs to the Special Issue Concentrated Solar Energy for Materials)

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17 pages, 4931 KiB

Open AccessArticle

Heat Integration of a Boiler and Its Corresponding Environmental Study in an Oleochemical Production Plant: An Industry Case Study in Malaysia

by Kai Seng Koh, Shee Jia Chew, Chee Ming Choo and Vui Soon Chok

ChemEngineering 2019, 3(4), 82; https://doi.org/10.3390/chemengineering3040082 - 04 Oct 2019

Cited by 2 | Viewed by 3937

Abstract

The growing demands for oleochemical products are expected to reach approximately RM 157.59 billion by 2026 due to an increased drive from the food and beverages, chemicals, and pharmaceutical industries. However, this will lead to an increase in energy consumption and subsequent flue [...] Read more.

The growing demands for oleochemical products are expected to reach approximately RM 157.59 billion by 2026 due to an increased drive from the food and beverages, chemicals, and pharmaceutical industries. However, this will lead to an increase in energy consumption and subsequent flue gas emission. Proper utilization of waste gas recovery systems is thus a major research area, focusing on reducing fuel consumption and emissions of greenhouse gases without affecting process performance. In this paper, a palm oil-based oleochemical plant is studied. The fuel consumption and emission of flue gas from a thermal oil boiler were measured and the feasibility of implementation of a waste heat recovery system and its environmental impact study. The results show that the implementation of such a system can reduce natural fuel gas consumption by 17.29% and approximately 149.29 t per annum of carbon dioxide gas (CO₂). Moreover, the concentration of CO₂ released into highly-populated communities is estimated through a Gaussian Plume Model at different wind speed conditions. The preliminary results show that the CO₂ concentration at two locations—an apartment and a local school located within 1.5 km of the plant—is well below the concentration limit of 1.938 g/m³ recommended by the Wisconsin Department of Health and Services. Full article

(This article belongs to the Special Issue Advanced Heat Exchangers for Waste Heat Recovery Applications)

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14 pages, 2668 KiB

Open AccessArticle

Conductivity, Viscosity, Spectroscopic Properties of Organic Sulfonic Acid solutions in Ionic Liquids

by Anh T. Tran, Jay Tomlin, Phuoc H. Lam, Brittany L. Stinger, Alexandra D. Miller, Dustin J. Walczyk, Omar Cruz, Timothy D. Vaden and Lei Yu

ChemEngineering 2019, 3(4), 81; https://doi.org/10.3390/chemengineering3040081 - 01 Oct 2019

Cited by 8 | Viewed by 4803

Abstract

Sulfonic acids in ionic liquids (ILs) are used as catalysts, electrolytes, and solutions for metal extraction. The sulfonic acid ionization states and the solution acid/base properties are critical for these applications. Methane sulfonic acid (MSA) and camphor sulfonic acid (CSA) are dissolved in [...] Read more.

Sulfonic acids in ionic liquids (ILs) are used as catalysts, electrolytes, and solutions for metal extraction. The sulfonic acid ionization states and the solution acid/base properties are critical for these applications. Methane sulfonic acid (MSA) and camphor sulfonic acid (CSA) are dissolved in several IL solutions with and without bis(trifluoromethanesulfonyl)imine (HTFSI). The solutions demonstrated higher conductivities and lower viscosities. Through calorimetry and temperature-dependent conductivity analysis, we found that adding MSA to the IL solution may change both the ion migration activation energy and the number of “free” charge carriers. However, no significant acid ionization or proton transfer was observed in the IL solutions. Raman and IR spectroscopy with computational simulations suggest that the HTFSI forms dimers in the solutions with an N-H-N “bridged” structure, while MSA does not perturb this hydrogen ion solvation structure in the IL solutions. CSA has a lower solubility in the ILs and reduced the IL solution conductivity. However, in IL solutions containing 0.4 M or higher concentration of HTFSI, CSA addition increased the conductivity at low CSA concentrations and reduced it at high concentrations, which may indicate a synergistic effect. Full article

(This article belongs to the Special Issue Advanced Ionic Liquid-Based Mixed Solvent Systems)

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12 pages, 2054 KiB

Open AccessArticle

Corrosion Protection of Monel Alloy Coated with Graphene Quantum Dots Starts with a Surge

by Charles Bopp and Kalathur Santhanam

ChemEngineering 2019, 3(4), 80; https://doi.org/10.3390/chemengineering3040080 - 30 Sep 2019

Cited by 7 | Viewed by 4373

Abstract

There has been an active interest in protecting metals and alloys using graphene coating. The mechanism by which corrosion protection occurs has not been well understood as the couple involved are both good electron conductors. In this work, we demonstrate that Monel alloy [...] Read more.

There has been an active interest in protecting metals and alloys using graphene coating. The mechanism by which corrosion protection occurs has not been well understood as the couple involved are both good electron conductors. In this work, we demonstrate that Monel alloy coated with graphene quantum dots (GQD) changes the corrosion rate with a surge (increase) caused by the galvanic coupling of the two materials. This surge results in the protective layer formation on Monel to inhibit the corrosion. X-ray fluorescence spectrum of Monel (400) alloy showed the composition of it as Ni (67.05%) and Cu (29.42%). The Tafel experiments carried out in NaCl and Na₂SO₄ electrolytes showed an initial enhancement of the corrosion rate followed by a decrease upon successive polarizations. Monel coated with graphene oxide (an insulator) shows no initial enhancement of corrosion rate; the coated samples showed a lower corrosion rate in comparison to the uncoated samples. X-ray fluorescence, Fourier Transform spectroscopy (FTIR) and Raman imaging studies have been carried out for understanding this transformation. Distinct peaks due to Ni-O stretching and Ni-O-H bending vibration were observed in the FTIR spectrum. Full article

(This article belongs to the Special Issue Carbon-Based Materials and Their Electrochemical Applications)

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12 pages, 3299 KiB

Open AccessArticle

The Effect of Cu and Ga Doped ZnIn₂S₄ under Visible Light on the High Generation of H₂ Production

by Ikki Tateishi, Mai Furukawa, Hideyuki Katsumata and Satoshi Kaneco

ChemEngineering 2019, 3(4), 79; https://doi.org/10.3390/chemengineering3040079 - 29 Sep 2019

Cited by 8 | Viewed by 3424

Abstract

A Cu⁺ and Ga³⁺ co-doped ZnIn₂S₄ photocatalyst (Zn_(1−2x)(CuGa)_xIn₂S₄) with controlled band gap was prepared via a simple one-step solvothermal method. Zn_(1−2x)(CuGa)_xIn₂S₄ acted as [...] Read more.

A Cu⁺ and Ga³⁺ co-doped ZnIn₂S₄ photocatalyst (Zn_(1−2x)(CuGa)_xIn₂S₄) with controlled band gap was prepared via a simple one-step solvothermal method. Zn_(1−2x)(CuGa)_xIn₂S₄ acted as an efficient photocatalyst for H₂ evolution under visible light irradiation (λ > 420 nm; 4500 µW/cm²). The effects of the (Cu and Ga)/Zn molar ratios of Zn_(1−2x)(CuGa)_xIn₂S₄ on the crystal structure (hexagonal structure), morphology (microsphere-like flower), optical property (light harvesting activity and charge hole separation ability), and photocatalytic activity have been investigated in detail. The maximum H₂ evolution rate (1650 µmol·h⁻¹·g⁻¹) was achieved over Zn_0.84(CuGa)_0.13In₂S₄, showing a 3.3 times higher rate than that of untreated ZnIn₂S₄. The bandgap energy of Zn_(1−2x)(CuGa)_xIn₂S₄ decreased from 2.67 to 1.90 eV as the amount of doping Cu⁺ and Ga³⁺ increased. Full article

(This article belongs to the Special Issue Advances in Metal-Based Catalysts)

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13 pages, 690 KiB

Open AccessArticle

Assessing Environmental Sustainability Using Ecological Limits Expressed as Mass Flowrates with the Inclusion of a Sustainable Time Perspective

by John J. Fitzpatrick and Brian Mullally

ChemEngineering 2019, 3(4), 78; https://doi.org/10.3390/chemengineering3040078 - 24 Sep 2019

Cited by 3 | Viewed by 2681

Abstract

This study explores the concept of ecological limits (ELs) for determining the sustainable extraction of natural resources and sustainable discharge of emissions. ELs are expressed as limiting mass flowrates and equations are developed and presented for their quantitative estimation. These [...] Read more.

This study explores the concept of ecological limits (ELs) for determining the sustainable extraction of natural resources and sustainable discharge of emissions. ELs are expressed as limiting mass flowrates and equations are developed and presented for their quantitative estimation. These include a sustainable time perspective term. This is a time duration that provides sufficient time for humans to adapt to the depletion of a resource stock or emission budget, e.g., the time for a number of human generations. Thus, even if a resource is utilised at a greater rate than its regeneration rate, it could be considered sustainable if the resource extraction rate is adjusted so that the stock continuously lasts for more than the sustainable timeframe. The application of this ecological limits concept is illustrated by applying it to assessing the environmental sustainability of global fossil fuel energy, specific water resources, and global fertilisers. Exceeding ELs can act as a warning signal and highlight those resources and emissions where actions need to be taken to bring their extraction and discharge rates to within the ELs. Full article

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19 pages, 3851 KiB

Open AccessArticle

Energy and Resource Efficient Production of Fluoroalkenes in High Temperature Microreactors

by Konstantin Mierdel, Andreas Jess, Thorsten Gerdes, Achim Schmidt and Klaus Hintzer

ChemEngineering 2019, 3(4), 77; https://doi.org/10.3390/chemengineering3040077 - 24 Sep 2019

Cited by 3 | Viewed by 3276

Abstract

Tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) are the most common monomers for the synthesis of fluoropolymers at industrial scale. Currently, TFE is produced via multistep pyrolysis of chlorodifluoromethane (R22), resulting in a high energy demand and high amounts of waste acids, mainly HCl and [...] Read more.

Tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) are the most common monomers for the synthesis of fluoropolymers at industrial scale. Currently, TFE is produced via multistep pyrolysis of chlorodifluoromethane (R22), resulting in a high energy demand and high amounts of waste acids, mainly HCl and HF. In this study, a new chlorine-free process for producing TFE and HFP in a microreactor is presented, starting from partially fluorinated alkanes obtained from electrochemical fluorination (ECF). In the microreactor, high conversion rates of CHF₃, which is used as a surrogate of partly fluorinated ECF streams, and high yields of fluoromonomers could be achieved. The energy saving and the environmental impact are shown by a life cycle assessment (LCA). The LCA confirms that the developed process has economical as well as ecological benefits, and is thus an interesting option for future industrial production of fluoroalkenes. Full article

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ChemEngineering, Volume 3, Issue 4 (December 2019) – 15 articles

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