Design of a Solar Reactor to Split CO2 Via Isothermal Redox Cycling of Ceria

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Roman Bader ◽  
Rohini Bala Chandran ◽  
Luke J. Venstrom ◽  
Stephen J. Sedler ◽  
Peter T. Krenzke ◽  
...  
Keyword(s):  
Gas Flow ◽  
High Surface ◽  
High Surface Area ◽  
Design Procedure ◽  
Redox Cycling ◽  
Operating Conditions ◽  
Heterogeneous Reactions ◽  
Small Scale ◽  
Static Factor ◽  
Mechanical Models

The design procedure for a 3 kWth prototype solar thermochemical reactor to implement isothermal redox cycling of ceria for CO2 splitting is presented. The reactor uses beds of mm-sized porous ceria particles contained in the annulus of concentric alumina tube assemblies that line the cylindrical wall of a solar cavity receiver. The porous particle beds provide high surface area for the heterogeneous reactions, rapid heat and mass transfer, and low pressure drop. Redox cycling is accomplished by alternating flows of inert sweep gas and CO2 through the bed. The gas flow rates and cycle step durations are selected by scaling the results from small-scale experiments. Thermal and thermo-mechanical models of the reactor and reactive element tubes are developed to predict the steady-state temperature and stress distributions for nominal operating conditions. The simulation results indicate that the target temperature of 1773 K will be reached in the prototype reactor and that the Mohr–Coulomb static factor of safety is above two everywhere in the tubes, indicating that thermo-mechanical stresses in the tubes remain acceptably low.

Investigation of BTEX Adsorption on Carbon Nanotubes Cartridges from Air Samples

2019 ◽  
Vol 889 ◽  
pp. 216-222 ◽  
Author(s):  
Huu Quynh Anh Le ◽  
Dinh Tuan Phan
Keyword(s):  
Carbon Nanotubes ◽  
Adsorption Capacity ◽  
Flow Rate ◽  
Gas Flow ◽  
High Surface ◽  
High Surface Area ◽  
Operating Conditions ◽  
Multiwalled Carbon ◽  
Air Samples ◽  
Environmental Treatment

The volatile organic compounds (VOCs) contribute to serious air pollution problems in Viet Nam. Many studies have investigated in air quality monitoring and treatment, in order to determine the average concentrations of Benzene, Toluene, Ethylbenzene and Xylene (BTEX). Carbon nanotubes (CNTs) have been widely used as adsorbent in environmental treatment, especially for VOCs. This paper aims to determine the adsorption capacity of multiwalled carbon nanotubes for removal of BTEX from air samples. In preliminary study, the effects of various parameters during adsorption experiments were monitored such as flow rate, temperature and BTEX concentrations in air samples. The equipment for BTEX removal was developed by our research team consisting of filter columns, air sample bags, adsorption cartridge. The air samples containing BTEX were conducted directly through a cartridge packed with adsorbent. The adsorption experiments were carried out under various operating conditions such as temperature (30 - 40°C), gas concentration (0,57 - 4,77 mg/L) and the gas flow rate (10 - 90 mL/min). In addition, isotherm studies of CNTs for BTEX removal were achieved by using Langmuir and Freundlich models. The results showed that the experimental parameters were optimized at a flow rate of 30 mL/min and an ambient temperature at 30°C. The adsorption capacity of CNTs increased proportionally with BTEX concentrations. The specific affinity of CNTs for BTEX from air samples was in order of X > E > T > B. The experimental isotherm data were well-fit with the Langmuir model for Benzene and Xylene removal, and the Freundlich model for Toluene and Ethylbenzene adsorption. The CNTs presented highly potential application for BTEX adsorption thanks to their microporous structure and high surface area.

scholarly journals Improved Catalytic Transfer Hydrogenation of Levulinate Esters with Alcohols over ZrO2 Catalyst

2020 ◽  
Vol 2 (1) ◽  
pp. 28
Author(s):  
Tommaso Tabanelli ◽  
Paola Blair Vásquez ◽  
Emilia Paone ◽  
Rosario Pietropaolo ◽  
Nikolaos Dimitratos ◽  
...  
Keyword(s):  
Gas Flow ◽  
Agricultural Waste ◽  
High Surface ◽  
High Surface Area ◽  
Tetragonal Zirconia ◽  
Transfer Hydrogenation ◽  
Catalytic Transfer Hydrogenation ◽  
Flow Conditions ◽  
Catalytic Transfer ◽  
Alkyl Levulinates

Levulinic acid (LA) and its esters (alkyl levulinates) are polyfunctional molecules that can be obtained from lignocellulosic biomass. Herein, the catalytic conversion of methyl and ethyl levulinates into γ-valerolactone (GVL) via catalytic transfer hydrogenation (CTH) by using methanol, ethanol, and 2-propanol as the H-donor/solvent, was investigated under both batch and gas-flow conditions. In particular, high-surface-area, tetragonal zirconia has proven to be a suitable catalyst for this reaction. Isopropanol was found to be the best H-donor under batch conditions, with ethyl levulinate providing the highest yield in GVL. However, long reaction times and high autogenic pressures are needed in order to work in the liquid-phase at high temperature with light alcohols. The reactions occurring under continuous gas-flow conditions, at atmospheric pressure and a relatively low contact time (1 s), were found to be much more efficient, also showing excellent GVL yields when EtOH was used as the reducing agent (GVL yield of around 70% under optimized conditions). The reaction has also been tested using a true bio-ethanol, derived from agricultural waste. These results represent the very first examples of the CTH of alkyl levulinates under continuous gas-flow conditions reported in the literature.

Influence of nanoparticles on the polymer-conditioned dewatering of wastewater sludges

2013 ◽  
Vol 67 (9) ◽  
pp. 2117-2123
Author(s):  
N. J. Boyle ◽  
G. M. Evans
Keyword(s):  
Activated Sludge ◽  
Titanium Dioxide Nanoparticles ◽  
Low Cost ◽  
High Surface ◽  
High Surface Area ◽  
Wastewater Sludge ◽  
Small Scale ◽  
Sludge Dewatering ◽  
Solids Content ◽  
The Impact

The effect of using small-scale, high surface area, nanoparticles to supplement polymer-conditioned wastewater sludge dewatering was investigated. Aerobically digested sludge and waste activated sludge sourced from the Hunter Valley, NSW, Australia, were tested with titanium dioxide nanoparticles. The sludge samples were dosed with the nanoparticles in an attempt to adsorb a component of the charged biopolymer surfactants present naturally in sludge. The sludge was conditioned with a cationic polymer. The dewatering characteristics were assessed by measuring the specific resistance to filtration through a modified time-to-filter testing apparatus. The solids content of the dosed samples was determined by a mass balance and compared to the original solids content in the activated sludge. Test results indicated that nanoparticle addition modified the structure of the sludge and provided benefits in terms of the dewatering rate. The samples dosed with nanoparticles exhibited faster water removal, indicating a more permeable filter cake and hence more permeable sludge. A concentration of 2–4% nanoparticles was required to achieve a noticeable benefit. As a comparison, the sludge samples were also tested with a larger particle size, powdered activated carbon (PAC). It was found that the PAC did provide some minor benefits to sludge dewatering but was outperformed by the nanoparticles. The solids content of the final sludge was increased by a maximum of up to 0.6%. The impact of the order sequence of particles and polymer was also investigated. It was found that nanoparticles added before polymer addition provided the best dewatering performance. This outcome was consistent with current theories and previous research through the literature. An economic analysis was undertaken to confirm the viability of the technology for implementation at a full-scale plant. It was found that, currently, this technology is unlikely to be favourable unless the nanoparticles can be sourced for a low cost.

Oxygen uptake by porcine colon contents

1998 ◽  
Vol 1998 ◽  
pp. 163-163
Author(s):  
K. Hillman
Keyword(s):  
Dissolved Oxygen ◽  
Surface Area ◽  
Gas Flow ◽  
High Surface ◽  
High Surface Area ◽  
Oxygen Electrode ◽  
Gut Contents ◽  
Constant Flow Rate ◽  
Anaerobic Microorganisms ◽  
Ringer’S Solution

Since the gut environment is generally assumed to be anaerobic, studies of the monogastric intestinal microflora have concentrated on the anaerobic microorganisms. However, the intestinal epithelium constitutes a very high surface area in relation to the volume of the gut contents, and all of this surface area is richly supplied with blood. Appreciable dissolved oxygen concentrations can be detected in the intestines of anaesthetised piglets (Hillman et al, 1993), although this is never detectable in the intestines of killed animals. It was considered important to investigate the persistence of intestinal oxygen after death, in order to determine the accuracy of postmortem measurements of this component of the intestinal environment. This report demonstrates the rapidity of removal of oxygen by porcine colon contents, and indicates that, since the oxygen supply to the intestine stops when the blood circulation stops, accurate measurements of dissolved oxygen can never be made in the intestines of killed animals.Colon contents were obtained from three freshly slaughtered 20 kg piglets and diluted to 20% (w/v) slurries in quarter-strength Ringer's solution (Unipath, UK). The slurries were transferred (25 ml) to 50 ml conical flasks, stirred by magnetic follower (approx 400 rpm) and surrounded by a water jacket to maintain a temperature of 39°C in the vessel contents. A polarographic oxygen electrode was inserted so that the membrane was submerged. Gas flow through the headspace was provided by compressed air and nitrogen, mixed via a pair of needle valves to provide a constant flow rate of 600 ml min-1. Calibration of the system was performed in sterile Ringer's solution using air and oxygen-free nitrogen: calibration was repeated between each experiment.

Gas permeability of carbon aerogels

1993 ◽  
Vol 8 (12) ◽  
pp. 3100-3105 ◽  
Author(s):  
F-M. Kong ◽  
J.D. LeMay ◽  
S.S. Hulsey ◽  
C.T. Alviso ◽  
R.W. Pekala
Keyword(s):  
Pore Size ◽  
Gas Flow ◽  
Gas Permeability ◽  
High Surface ◽  
High Surface Area ◽  
Supercritical Drying ◽  
Flow Equation ◽  
Carbon Aerogels ◽  
Thin Specimen ◽  
Potential Applications

Carbon aerogels are synthesized via the aqueous polycondensation of resorcinol with formaldehyde, followed by supercritical drying and subsequent pyrolysis at 1050 °C. As a result of their interconnected porosity, ultrafine cell/pore size, and high surface area, carbon aerogels have many potential applications such as supercapacitors, battery electrodes, catalyst supports, and gas filters. The performance of carbon aerogels in the latter two applications depends on the permeability or gas flow conductance in these materials. By measuring the pressure differential across a thin specimen and the nitrogen gas flow rate in the viscous regime, the permeability of carbon aerogels was calculated from equations based upon Darcy's law. Our measurements show that carbon aerogels have permeabilities on the order of 10−12 to 10−10 cm2 over the density range from 0.05–0.44 g/cm3. Like many other aerogel properties, the permeability of carbon aerogels follows a power law relationship with density, reflecting differences in the average mesopore size. Comparing the results from this study with the permeability of silica aerogels reported by other workers, we found that the permeability of aerogels is governed by a simple universal flow equation. This paper discusses the relationship among permeability, pore size, and density in carbon aerogels.

Development of magnetic nano-geocomposite for groundwater and leachate treatment: A Landfill Management Perspective

2020 ◽  
Author(s):  
Nivedita Pradhan ◽  
Manish Kumar
Keyword(s):  
Landfill Leachate ◽  
Emerging Contaminants ◽  
High Surface ◽  
High Surface Area ◽  
Operating Conditions ◽  
Future Research ◽  
Leachate Treatment ◽  
Freundlich Isotherms ◽  
Landfill Management ◽  
Physical And Chemical

<ul>Landfill leachate, a highly contaminated percolating effluent can cause a considerable threat to human as well as environmental health. We developed a novel nano composite using the polymer encapsulated magnetic geopolymer for efficient removal of multi contaminants (As, Zn, Fe, Co, Cu, Ni, Pb, F, NO 3 - , and PO 4 3- ) present in the landfill leachate and groundwater of the Pirana solid waste dumping site, Ahmedabad, Gujarat. A series of batch and column sorption experiments were carried out to find the best-operating conditions for optimum removal efficiency. Results revealed that in the range of 50-60% of multi-contaminant removal is possible using the newly developed adsorbent which has high surface area as well as mixed functional groups for the removal of both cationic (Zn, Fe, Co, Cu, Ni, and Pb) and anionic (F, NO 3 - , and PO 4 3- ) contaminants present in the leachate. Batch study shows that both physical and chemical sorption are equally operational and multilayer removal following the Freundlich isotherms predominantly. The batch test mimics the equilibrium condition only. The study recommends column study under different follow conditions using leachate and groundwater, followed by a regeneration study for its reusability and development of the field implementation schemes. The future research is required to address the decontamination of emerging contaminants like pharmaceuticals, pesticides and fertilizers, industrial additives and antibacterial agents.</ul>

A Novel Direct Carbon Fuel Cell Concept

2006 ◽  
Vol 4 (3) ◽  
pp. 280-282 ◽  
Author(s):  
Sneh L. Jain ◽  
J. Barry Lakeman ◽  
Kevin D. Pointon ◽  
John T. S. Irvine
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
High Surface ◽  
Tape Casting ◽  
High Surface Area ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Direct Carbon Fuel Cell ◽  
Fuel Material

This paper describes a direct carbon fuel cell (DCFC) based on a solid oxide fuel cell (SOFC) system which has been used to assess the performance of a high surface area carbon fuel material. The cell, consisting of a co-fired anode, electrolyte, and cathode, has been produced by standard tape casting methods and is of tubular geometry. The operating conditions of the cell require a 62mol%Li2CO3 and 38mol%K2CO3 eutectic secondary electrolyte and the operation of the cell is described over the temperature range 525–700°C. The cell performance has been examined by standard electrochemical methods.

scholarly journals Feasibility Study and Demonstration of an Aluminum and Ice Solid Propellant

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Timothee L. Pourpoint ◽  
Tyler D. Wood ◽  
Mark A. Pfeil ◽  
John Tsohas ◽  
Steven F. Son
Keyword(s):  
Hydrogen Generation ◽  
High Surface ◽  
High Surface Area ◽  
Sounding Rocket ◽  
Small Scale ◽  
Solid Propellants ◽  
Aluminum Particles ◽  
Underwater Propulsion ◽  
Binary Formulation

Aluminum-water reactions have been proposed and studied for several decades for underwater propulsion systems and applications requiring hydrogen generation. Aluminum and water have also been proposed as a frozen propellant, and there have been proposals for other refrigerated propellants that could be mixed, frozen in situ, and used as solid propellants. However, little work has been done to determine the feasibility of these concepts. With the recent availability of nanoscale aluminum, a simple binary formulation with water is now feasible. Nanosized aluminum has a lower ignition temperature than micron-sized aluminum particles, partly due to its high surface area, and burning times are much faster than micron aluminum. Frozen nanoscale aluminum and water mixtures are stable, as well as insensitive to electrostatic discharge, impact, and shock. Here we report a study of the feasibility of an nAl-ice propellant in small-scale rocket experiments. The focus here is not to develop an optimized propellant; however improved formulations are possible. Several static motor experiments have been conducted, including using a flight-weight casing. The flight weight casing was used in the first sounding rocket test of an aluminum-ice propellant, establishing a proof of concept for simple propellant mixtures making use of nanoscale particles.

Determination of the Permeability of Carbon Aerogels by Gas Flow Measurements

1992 ◽  
Vol 270 ◽  
Author(s):  
F-M. Kong ◽  
S.S. Hulsey ◽  
C.T. Alviso ◽  
R.W. Pekala
Keyword(s):  
Pore Size ◽  
Gas Flow ◽  
Cell Structure ◽  
Average Pore Size ◽  
High Surface ◽  
High Surface Area ◽  
Carbon Aerogels ◽  
Average Pore ◽  
Thin Specimen ◽  
Flow Measurements

ABSTRACTCarbon aerogels are synthesized via the polycondensation of resorcinol and formaldehyde, followed by supercritical drying and pyrolysis at 1050 °C in nitrogen. Because of their interconnected porosity, ultrafine cell structure and high surface area, carbon aerogels have many potential applications, such as in supercapacitors, battery electrodes, catalyst supports, and gas filters. The performance of carbon aerogels in the latter two applications depends on the permeability or gas flow conductance in these materials. By measuring the pressure differential across a thin specimen and the nitrogen gas flow rate in the viscous regime, we calculated the permeability of carbon aerogels from equations based upon Darcy's law. Our measurements show that carbon aerogels have apparent permeabilities on the order of 10−12 to 10−10 cm2 for densities ranging from 0.44 to 0.05 g/cm3. Like their mechanical properties, the permeability of carbon aerogels follows a power law relationship with density and average pore size. Such findings help us to estimate the average pore sizes of carbon aerogels once their densities are known. This paper reveals the relationships among permeability, pore size and density in carbon aerogels.

Data-Driven Predesign Tool for Small-Scale Centrifugal Compressor in Refrigeration

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Mounier Violette ◽  
Picard Cyril ◽  
Schiffmann Jürg
Keyword(s):  
Centrifugal Compressor ◽  
High Efficiency ◽  
Design Procedure ◽  
Integrated System ◽  
Operating Conditions ◽  
Data Driven ◽  
Small Scale ◽  
Centrifugal Compressors ◽  
Starting Point ◽  
Isentropic Efficiency

Domestic scale heat pumps and air conditioners are mainly driven by volumetric compressors. Yet the use of reduced scale centrifugal compressors is reconsidered due to their high efficiency and power density. The design procedure of centrifugal compressors starts with predesign tools based on the Cordier line. However, the optimality of the obtained predesign, which is the starting point of a complex and iterative process, is not guaranteed, especially for small-scale compressors operating with refrigerants. This paper proposes a data-driven predesign tool tailored for small-scale centrifugal compressors used in refrigeration applications. The predesign model is generated using an experimentally validated one-dimensional (1D) code which evaluates the compressor performance as a function of its detailed geometry and operating conditions. Using a symbolic regression tool, a reduced order model that predicts the performance of a given compressor geometry has been built. The proposed predesign model offers an alternative to the existing tools by providing a higher level of detail and flexibility. Particularly, the model includes the effect of the pressure ratio, the blade height ratio, and the shroud to tip radius ratio. The analysis of the centrifugal compressor losses allows identifying the underlying phenomena that shape the new isentropic efficiency contours. Compared to the validated 1D code, the new predesign model yields deviations below 4% on the isentropic efficiency, while running 1500 times faster. The new predesign model is, therefore, of significant interest when the compressor is part of an integrated system design process.

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