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Presentation given by Dr Hao Liu from University of Nottingham on "CO2 capture from NGCC Flue Gas and Ambient Air Using PEI-Silica Adsorbent" in the Capture Technical Session on Solid Adsorption at the UKCCSRC Biannual Meeting - CCS in the Bigger Picture - held in Cambridge on 2-3 April 2014
Presentation given by Professor Joe Wood from University of Birmingham on "Studies of Hydrotalcite Clays for CO2 Adsorption " in the Capture Technical Session on Solid Adsorption at the UKCCSRC Biannual Meeting - CCS in the Bigger Picture - held in Cambridge on 2-3 April 2014
Thermal regeneration of activated carbon saturated with nitrate ions from an ...IJAEMSJORNAL
The present study was initiated to help the simple and less expensive regeneration of activated carbons after saturation in rural area. In order to determine a regeneration time and the number of regeneration cycles, an adsorption test was necessary. Thus, 3h and 4 cycles of carbon regeneration are obtained after evaluation of the performance, percentage and adsorption capacity after each cycle. Regeneration percentages of 71.29, 54.05, 40.40, 28.06 % and 72.6, 69.84, 64.33, 34.98 %for respective concentrations of 30± 1.2 mg/L and 55 ± 1.6 mg/L are observed. Also, the performances of activated carbon 8.5, 10, 12, 20 g/L and capacities 24.04, 19.93, 14.9 and 10.35mg/g 35.7, 34.12, 31.43 and 17.09 mg/g respectively for dry season and rainy season were necessary to fix the number of cycles. The artisanal furnace with its ease of installation and its maximum temperature of 500±2°C is suitable for the regeneration of saturated activated carbon.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after 24 h irradiation was 9934 μmol g−1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride 145 μmol g−1cat under identical conditions. The presence of triethylamine was found to be vital for the higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Solar Thermochemical Conversion of CO2 into C via SnO2/SnO Redox Cycle: A The...IJERA Editor
In this paper we report the computational thermodynamic modeling of the solar thermochemical SnO2/SnO
redox cycle for solid C production via CO2 splitting. In this redox cycle, the first step corresponds to the solar
thermal reduction of SnO2 into SnO and O2 in presence of inert atmosphere. The second step, which is a nonsolar
exothermic stage, is the reaction of SnO with CO2 to produce solid C together with SnO2 that is recycled
back to the first step. Commercially available HSC Chemistry software and databases were used for the
computational thermodynamic modeling of this process. The thermodynamic analysis was performed in two
sections: 1) equilibrium composition analysis, and 2) exergy analysis. Results obtained via the computational
thermodynamic modeling are presented in detail. The simulation results indicate that the solar thermochemical
SnO2/SnO redox cycle for solid C production via CO2 splitting can achieve the solar to fuel conversion
efficiency upto 12%.
Presentation given by Dr Hao Liu from University of Nottingham on "CO2 capture from NGCC Flue Gas and Ambient Air Using PEI-Silica Adsorbent" in the Capture Technical Session on Solid Adsorption at the UKCCSRC Biannual Meeting - CCS in the Bigger Picture - held in Cambridge on 2-3 April 2014
Presentation given by Professor Joe Wood from University of Birmingham on "Studies of Hydrotalcite Clays for CO2 Adsorption " in the Capture Technical Session on Solid Adsorption at the UKCCSRC Biannual Meeting - CCS in the Bigger Picture - held in Cambridge on 2-3 April 2014
Thermal regeneration of activated carbon saturated with nitrate ions from an ...IJAEMSJORNAL
The present study was initiated to help the simple and less expensive regeneration of activated carbons after saturation in rural area. In order to determine a regeneration time and the number of regeneration cycles, an adsorption test was necessary. Thus, 3h and 4 cycles of carbon regeneration are obtained after evaluation of the performance, percentage and adsorption capacity after each cycle. Regeneration percentages of 71.29, 54.05, 40.40, 28.06 % and 72.6, 69.84, 64.33, 34.98 %for respective concentrations of 30± 1.2 mg/L and 55 ± 1.6 mg/L are observed. Also, the performances of activated carbon 8.5, 10, 12, 20 g/L and capacities 24.04, 19.93, 14.9 and 10.35mg/g 35.7, 34.12, 31.43 and 17.09 mg/g respectively for dry season and rainy season were necessary to fix the number of cycles. The artisanal furnace with its ease of installation and its maximum temperature of 500±2°C is suitable for the regeneration of saturated activated carbon.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after 24 h irradiation was 9934 μmol g−1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride 145 μmol g−1cat under identical conditions. The presence of triethylamine was found to be vital for the higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Solar Thermochemical Conversion of CO2 into C via SnO2/SnO Redox Cycle: A The...IJERA Editor
In this paper we report the computational thermodynamic modeling of the solar thermochemical SnO2/SnO
redox cycle for solid C production via CO2 splitting. In this redox cycle, the first step corresponds to the solar
thermal reduction of SnO2 into SnO and O2 in presence of inert atmosphere. The second step, which is a nonsolar
exothermic stage, is the reaction of SnO with CO2 to produce solid C together with SnO2 that is recycled
back to the first step. Commercially available HSC Chemistry software and databases were used for the
computational thermodynamic modeling of this process. The thermodynamic analysis was performed in two
sections: 1) equilibrium composition analysis, and 2) exergy analysis. Results obtained via the computational
thermodynamic modeling are presented in detail. The simulation results indicate that the solar thermochemical
SnO2/SnO redox cycle for solid C production via CO2 splitting can achieve the solar to fuel conversion
efficiency upto 12%.
Carbon Dioxide to Chemicals and Fuels Course Material.
National Centre for Catalysis Research (NCCR, IIT Madras), considered for the first on-line course the topic of Carbon dioxide to Chemicals and Fuels. NCCR has learnt many such lessons which are necessary for the researchers to understand and also have a complete comprehension of the limitations.
Presentation given by Professor Colin Snape from University of Nottingham on "Performance Enhanced Activated Spherical Carbon Adsorbents for CO2 Capture" in the Capture Technical Session on Solid Adsorption at the UKCCSRC Biannual Meeting - CCS in the Bigger Picture - held in Cambridge on 2-3 April 2014
Jonathan Lee (Newcastle University) - Intensification of Solvent Based Carbon Capture using Rotating Packed Beds - UKCCSRC Cranfield Biannual 21-22 April 2015
CVD grown nitrogen doped graphene is an exceptional visible-light driven phot...Pawan Kumar
The photocatalytic potential of large area CVD grown nitrogen doped graphene (NGr) has been explored though the chemical transformation of 4-nitrobenzene thiol into p, p'-dimercaptoazobenzene. Decoration of NGr with Ag nanocubes with rounded edges to form NGr/Ag nanohybrids resulted in a slight increase in the work-function and a decrease in the n-type character of NGr due to ground state transfer of negative charge from NGr to Ag. The Ag nanocubes exhibited a localized surface plasmon resonance (LSPR) at~ 425 nm. When the NGr/Ag nanohybrids were illuminated with visible light of wavelength close to the LSPR peak, Kelvin probe force microscopy (KPFM) indicated a dramatic change in surface potential of− 225 mV and Raman spectra detected electron accumulation in NGr, which are attributed to a high local field enhancement-mediated hot electron injection into NGr and the formation of long …
CVD grown nitrogen doped graphene is an exceptional visible-light driven phot...Pawan Kumar
The photocatalytic potential of large area CVD grown nitrogen doped graphene (NGr) has been explored though the chemical transformation of 4-nitrobenzene thiol into p,p'-dimercaptoazobenzene. Decoration of NGr with Ag nanocubes with rounded edges to form NGr/Ag nanohybrids resulted in a slight increase in the work-function and a decrease in the n-type character of NGr due to ground state transfer of negative charge from NGr to Ag. The Ag nanocubes exhibited a localized surface plasmon resonance (LSPR) at ~425 nm. When the NGr/Ag nanohybrids were illuminated with visible light of wavelength close to the LSPR peak, Kelvin probe force microscopy (KPFM) indicated a dramatic change in surface potential of −225 mV and Raman spectra detected electron accumulation in NGr, which are attributed to a high local field enhancement-mediated hot electron injection into NGr and the formation of long-lived charge separated states. Pristine nitrogen doped graphene and its coupled system with plasmonic Ag nanoparticles showed superior photocatalytic performance compared to bare plasmonic Ag catalyst. While standalone Ag NPs were unable to complete the transformation of 4-NBT into DMAB even at a laser power of 10 mW, NGr/Ag nanohybrids completed this transformation at a laser power of 1 mW, pointing to the high photoreduction strength of NGr/Ag. Density functional theory (DFT) based computational modeling was used to examine the electronic structure of graphene doped with graphitic, pyridinic and pyrrolic nitrogen dopant atoms. DFT results indicated an enhanced chemical reactivity of NGr due to stronger localization of charge at the dopant sites and a pronounced difference in the projected density of states (PDOS) for carbon atoms in proximity to, and distant from, the nitrogen dopant sites.
The most difficult goal in the next few decades is the replacement of conventional petro-based fuels with more sustainable fuels that can be used in the existing infrastructure. By the use of Renewable energy or nuclear energy, CO2 and H2O can be recycled into liquid hydrocarbon fuels (the reverse of fuel combustion). Capture of CO2 from the atmosphere will form a close carbon-neutral fuel cycle loop. This article also reviews the aspects regarding thermodynamics involved, involved mechanisms and possible technological pathways for recycling CO2 into fuels using renewable energy. These pathways can be broken into three staged- CO2 capture from atmosphere, H2O and CO2 dissociation, and fuel synthesis.
Carbon Dioxide to Chemicals and Fuels Course Material.
National Centre for Catalysis Research (NCCR, IIT Madras), considered for the first on-line course the topic of Carbon dioxide to Chemicals and Fuels. NCCR has learnt many such lessons which are necessary for the researchers to understand and also have a complete comprehension of the limitations.
Presentation given by Professor Colin Snape from University of Nottingham on "Performance Enhanced Activated Spherical Carbon Adsorbents for CO2 Capture" in the Capture Technical Session on Solid Adsorption at the UKCCSRC Biannual Meeting - CCS in the Bigger Picture - held in Cambridge on 2-3 April 2014
Jonathan Lee (Newcastle University) - Intensification of Solvent Based Carbon Capture using Rotating Packed Beds - UKCCSRC Cranfield Biannual 21-22 April 2015
CVD grown nitrogen doped graphene is an exceptional visible-light driven phot...Pawan Kumar
The photocatalytic potential of large area CVD grown nitrogen doped graphene (NGr) has been explored though the chemical transformation of 4-nitrobenzene thiol into p, p'-dimercaptoazobenzene. Decoration of NGr with Ag nanocubes with rounded edges to form NGr/Ag nanohybrids resulted in a slight increase in the work-function and a decrease in the n-type character of NGr due to ground state transfer of negative charge from NGr to Ag. The Ag nanocubes exhibited a localized surface plasmon resonance (LSPR) at~ 425 nm. When the NGr/Ag nanohybrids were illuminated with visible light of wavelength close to the LSPR peak, Kelvin probe force microscopy (KPFM) indicated a dramatic change in surface potential of− 225 mV and Raman spectra detected electron accumulation in NGr, which are attributed to a high local field enhancement-mediated hot electron injection into NGr and the formation of long …
CVD grown nitrogen doped graphene is an exceptional visible-light driven phot...Pawan Kumar
The photocatalytic potential of large area CVD grown nitrogen doped graphene (NGr) has been explored though the chemical transformation of 4-nitrobenzene thiol into p,p'-dimercaptoazobenzene. Decoration of NGr with Ag nanocubes with rounded edges to form NGr/Ag nanohybrids resulted in a slight increase in the work-function and a decrease in the n-type character of NGr due to ground state transfer of negative charge from NGr to Ag. The Ag nanocubes exhibited a localized surface plasmon resonance (LSPR) at ~425 nm. When the NGr/Ag nanohybrids were illuminated with visible light of wavelength close to the LSPR peak, Kelvin probe force microscopy (KPFM) indicated a dramatic change in surface potential of −225 mV and Raman spectra detected electron accumulation in NGr, which are attributed to a high local field enhancement-mediated hot electron injection into NGr and the formation of long-lived charge separated states. Pristine nitrogen doped graphene and its coupled system with plasmonic Ag nanoparticles showed superior photocatalytic performance compared to bare plasmonic Ag catalyst. While standalone Ag NPs were unable to complete the transformation of 4-NBT into DMAB even at a laser power of 10 mW, NGr/Ag nanohybrids completed this transformation at a laser power of 1 mW, pointing to the high photoreduction strength of NGr/Ag. Density functional theory (DFT) based computational modeling was used to examine the electronic structure of graphene doped with graphitic, pyridinic and pyrrolic nitrogen dopant atoms. DFT results indicated an enhanced chemical reactivity of NGr due to stronger localization of charge at the dopant sites and a pronounced difference in the projected density of states (PDOS) for carbon atoms in proximity to, and distant from, the nitrogen dopant sites.
The most difficult goal in the next few decades is the replacement of conventional petro-based fuels with more sustainable fuels that can be used in the existing infrastructure. By the use of Renewable energy or nuclear energy, CO2 and H2O can be recycled into liquid hydrocarbon fuels (the reverse of fuel combustion). Capture of CO2 from the atmosphere will form a close carbon-neutral fuel cycle loop. This article also reviews the aspects regarding thermodynamics involved, involved mechanisms and possible technological pathways for recycling CO2 into fuels using renewable energy. These pathways can be broken into three staged- CO2 capture from atmosphere, H2O and CO2 dissociation, and fuel synthesis.
Gobernancia y particionacion en comunidades de Software Libre v2Alexandro Colorado
Presentacion que explica los pasos para participar en comunidades de software libre como OpenOffice y ejemplos de la infraestructura y como usarla. Tambien se habla de como gestionar tu propia comunidad y finalmente como empresas e instituciones academicas pueden participar en dichas comunidades.
ALey para Establecer Salvaguardas y Garantías para Acceder a Información Públ...Camara de Representantes
Capitolio (20 de enero de 2010) – Los Representantes del Partido Popular Jaime Perelló Borrás y Carmen Yulín Cruz Soto, presentaron legislación para crear una ley uniforme que garantice el derecho de todo ciudadano a acceder información pública en todas las agencias, instrumentalidades y corporaciones públicas del Estado Libre Asociado así como en la Asamblea Legislativa e imponer, entre otras cosas, términos para atender las peticiones.
Compañerxs, con el fin de que toda la comunidad esapista este al tanto de las discusiones que a nivel nacional se vienen desarrollando, les DEJAMOS LAS CONCLUSIONES DEL PRIMER ENCUENTRO ORGANIZATIVO. MANE - IBAGUÉ, los días 28 y 29 de Enero del 2012.
Production of CH4 and C2 hydrocarbons by axial and radial pulse H2/CO2 discha...theijes
Production of methane CH4 from a mixture gas of carbon dioxide CO2 and hydrogen H2 has been established by two types of pulse discharges. One is an axial discharge with a use of thin pair Ni wire electrodes separated by a narrow gap, and the other is a coaxially radial discharge with a use of inner rod and outer tube electrodes made of stainless steel (SUS). The former provides an intense gap discharge, while the latter provides a gentle discharge in the annular region. Decomposition of CO2 is enhanced in the former case when Ni (nickel) mesh disc electrode is placed behind the gap. Ni is known as catalysis. When the radial discharge proceeds in a closed gas system, 2C hydrocarbons such as ethane and ethylene are generated in case that a cylindrical mesh electrode made of Ni is attached to the powered SUS tube electrode. Both of the CH4 production and the energy efficiency for CH4 production are enhanced in case of Ni mesh electrodes, without a use of additional heating for the Ni catalysis. Synergy effect of plasma and Ni catalyst is observed
Post-combustion CO2 capture from natural gas combined cycles by solvent supported membranes - presentation by Matteo Romano of Politecnico di Milano at the UKCCSRC Natural Gas CCS Network Meeting at GHGT-12, Austin, Texas, October 2014
Mathematical modeling of a solid oxide fuel cell operating on biogasjournalBEEI
Solid oxide fuel cells (SOFC) are the most efficient devices for directly converting the chemical energy of a fuel into electrical energy. This is one of the main reasons why these fuel cells have received a lot of attention from the scientific community and from several developers who have invested in the use of this technology in various applications. Biogas is one of the products of anaerobic decomposition (absence of gaseous oxygen) of organic matter, which occurs due to the action of certain types of bacteria. Biogas is mainly composed of methane (CH4) and carbon dioxide (CO2) and its use in solid oxide fuel cells has been investigated since Biogas is a renewable biofuel. The aim of this paper was to perform mathematical modeling of a solid oxide fuel cell operating on biogas. The results confirmed that the overall efficiency of the system is above 94% and the largest irreversibilities of the system are related to heat exchangers.
Similar to International Journal of Computational Engineering Research(IJCER) (20)
Mathematical modeling of a solid oxide fuel cell operating on biogas
International Journal of Computational Engineering Research(IJCER)
1. International Journal Of Computational Engineering Research (ijceronline.com) Vol. 2 Issue. 8
Exergy Requirements for the Manufacturing of Carbon Nanotubes
Renish M vekariya1, Rakesh P Ravani2
1. HOD, A.I.E.T, MECH Dept., Rajkot-GJ, India,
2. Lec.VVP, MECH, Rajkot-GJ, India,
Abstract
The purpose of this paper is to address both the high values, and the large variation in reported values for the energy
requirements for the production of carbon nano tubes. The paper includes an estimate of the standard chemical exergy for single
walled carbon nano tubes, as well as a historical look at how the minimum physical flow exergy improved as the HiPco process
developed.
Keywords— Carbon Nanotubes, Exergy Analysis, SWNT
I. Introduction
Early estimates by Isaacs et al [1] indicated the potentially very large value of the specific energy requirements for
carbon single walled nano tubes (SWNT). More recently, energy estimates have been performed for a variety of carbon fibers
(SWNTs, multiwall carbon nano tubes – MWNT, and carbon fibers) and a variety of manufacturing processes (Arc, CVD and
HiPco) [2]–[6]. These studies show considerable variation in energy estimates (as much as 3 orders of magnitude), and almost
two orders of magnitude variation between nominally identical processes. In this paper we review the available data and then look
further into the so called HiPco process, (for high pressure carbon mono xide process) [7]-[9] to attempt to explain the large
variation in specific energy requirements.
II. Data Summary
In Table 1 we summarize data for various carbon nanofiber production methods (synthesis only) from the literature [1 -
4]. The Synthesis Reaction Carbon Yield (SRCY) is the amount of process carbon needed to produce carbon nano tubes/fibers. It
is based upon the flow rates of the process carbon and the carbon product output. Note that these values differ by almost three
orders of magnitude, while the specific electrical energy estimates for the synthesis reaction differ by more than three orders of
magnitude. The purification step after synthesis may add up to 50% more to the value given in column four [2].
Note: further that estimates for the HiPco process vary by almost two orders of magnitude. We will show that this variation is due
in part to the changing nature of the HiPco process as it has been improved. Further, important details of the process are not
generally available, and important assumptions in various analyses may differ, and in some cases are not reported.
TABLE 1
Results From The Literature For The Specific Work Input In The Form Of Electrical Energy Per Mass For The Production
Synthesis Process For Carbon Nano-Tubes And Fibers.
Process/Product Source SRCY1 GJ/kg2 Ref.
HiPco/SWNT CO 50% 465.8 [1]
HiPco/SWNT CO 0.08% 31.8 [2]
HiPco/SWNT CO NA 5.8 [3]
Arc/SWNT Carbon Anode 4.5% 458.7 [1]
Arc/SWNT Carbon Anode 4.5% 83.7 [2]
CVD/SWNT [ CH4 2.95% 915.8 [1]
III. Standard Chemical Exergy Of Swnt
The specific standard chemical exergy of a chemical compound is the minimum (reversible) work per mass to produce
this component starting from the identified chemical components of the reference environment at the “dead state”. For the
production of SWNTs the process would start from the carbon stored in the atmosphere as CO2 gas and include the following
steps; 1) the concentrating of the CO2 from its reference concentration in the atmosphere to pure, 2) the reduction of CO2 into
its chemical constituents, carbon graphite) and oxygen,
||Issn 2250-3005(online)|| ||December||2012 Page 162
2. International Journal Of Computational Engineering Research (ijceronline.com) Vol. 2 Issue. 8
1 SRCY = Synthesis Reaction Carbon Yield
2 Electricity for synthesis reaction only, does not include loss at utility
3 CNF = carbon nano fiber
(3) the separation of a graphene layer from the graphite, and 4) the bending of the graphene layer
into a carbon SWNT. The first two steps can be obtained from previous results for the standard chemical exergy for graphite as
410.26 kJ/mol or 34.16 kJ/g [10]. The work of cohesion to reversibly separate a layer from a bulk material is two times the
surface energy for the new surface [11]. Abrahamson [12] has provided a review of the surface energy of graphite, and estimates
it at 25kJ/mol or 2.08kJ/g. Finally, Lu [13] has analyzed the anisotropic bending of a graphene layer and estimated the (fully
elastic) moment – curvature behavior. This bending stiffness is due to the bond angle effect on interatomic interactions. From this
we may estimate the strain energy for the bending of a flat sheet 0.34nm thick to a tube with an outside diameter of 1.2 nm as 0.78
kJ/g. Putting this together we estimate the specific standard chemical exergy of a carbon SWNT as,
ex,o,SWNT = 34.16 + 4.16 + 0.78 = 39.1 kJ/g.
This is the minimum reversible work to produce SWNT at the “reduced dead state” (To, po) from components of the environment
at the ultimate dead state, or just the “dead state”. Note that this value is diameter dependent.
IV. Analysis of the Hipco Process
The HiPco process was developed by Prof. Richard Smalley’s group at Rice University in the late 1990’s. The process is
based on the so called disproportionation (Boudouard) reaction as given below. This reaction, under appropriate conditions and in
the presence of a suitable catalyst can produce carbon SWNT. Note that the reaction given in equation (1) is spontaneous and
exothermic, yielding (at standard conditions) an exergy output of 5.06 kJ/g of SWNT.
CO + CO C(s) + CO (1) 2
However, to produce SWNTs this reaction is carried out at elevated temperatures and pressures (~1000oC, ~30 atm)
requiring significant exergy inputs, currently several orders of magnitude larger than the chemical exergy change. In what follows
we calculate the minimum physical exergy required to create the conditions necessary to produce SWNT as reported in a series of
publications by the Smalley team [7]– [9] and others [2], [3]. During the approximately 9 year period of development covered by
these publications, we will see that the process has been significantly improved, reducing the exergy requirement by a factor of
34. The process, illustrated in Fig. 1 taken from their 2007 patent [9] shows recycling flows of CO gas that are repeatedly
exhausted and then reheated and repressurized. Our analysis focuses on a highly idealized version of the process that looks only at
the CO gas flows through the reaction chamber and compressor. These flows are treated separately as steady state open systems,
with only a work input (no heat inputs). The gas flow requirements are governed by the flow rates and production rates of the
process. We assume that the recycled CO is hot (100C) and at atmospheric pressure before being returned to the process
conditions (1000 C and 30 atm). This calculation can be done assuming ideal gas behavior and using
(2), see Gutowski and Sekulic [14].
Fig. 1. Schematic representation of the HiPCo process [Ref].
||Issn 2250-3005(online)|| ||December||2012 Page 163
3. International Journal Of Computational Engineering Research (ijceronline.com) Vol. 2 Issue. 8
= (T- )- T0 ln(T/T0)+T0Rln(P/P0)
This is the change in the specific physical flow exergy for an ideal gas. To convert the results in [3] to the minimum
exergy for comparison purposes, we used an assumed efficiency of 0.75 as discussed in their paper.
The key operating parameters and results for the minimum physical exergy to produce SWNT by the HiPco process are given in
Table 2 for different times in the evolution of this process. These results are also plotted in Fig. 2 at the end of this paper. The
results clearly show the improvement in the process and imply the difficulty in making energy estimates for new rapidly changing
technologies.
V. Comparison with Other Manufacturing Processes
In a previous publication [6], we reviewed a wide range of manufacturing processes. Here we add the new data on carbon
nano tube manufacturing (synthesis only) to our summary plot given in Fig. 3 at the end of this paper. We add two types of data:
1) the historical data for the improvement of the HiPco process as given in Table 2 and some of the data from the literature as
given in Table 1.
TABLE 2
Estimated Specific Energy Requirements And Process Rates For Synthesis Of Cnts
Compared to other processes, the carbon nanotube (CNT) manufacturing data shows several noteworthy trends. First,
while the specific electrical energy requirements are quite large, (generally exceeding 1 GJ/kg) they are not the largest we have
seen. In general, they seem comparable to semi conductor processes. Secondly, the power requirements for CNT are generally on
the low side of manufacturing processes, at least currently, for the current modest scales of production. Of course, this can, and is
changing as various companies announce the openings of large scale production facilities. The data also clearly show how the
HiPco process has improved over recent times.
VI. The Degree of Perfection for Swnt Production Processes
For resource accounting purposes, the so called “Degree of Perfection” can be a useful metric for evaluating
manufacturing processes. We define the Degree of Perfection for manufacturing processes as the ratio of the standard chemical
exergy of the output product(s) divided by the sum of the input exergies including the exergy equivalents of any work and/or heat
inputs as well as the standard chemical exergies of all material inputs. See [10], [14].
=
||Issn 2250-3005(online)|| ||December||2012 Page 164
4. International Journal Of Computational Engineering Research (ijceronline.com) Vol. 2 Issue. 8
The degree of perfection is a second law efficiency measure that can be used to identify opportunities for improvement
and to compare with other processes. To illustrate, consider the 2004 version of the idealized HiPco process with ideal reversible
thermal treatment and pressurization stages, but operated in an open loop i.e. without recycling of the CO gas. The degree of
perfection would be given by (39.1 kJ/g) / (12,500g x 9.82 kJ/g +12,040 kJ/g) = 2.9 x 10-4. This low value is due to the
requirement for large amounts of input CO and complete destruction of the physical exergy that was previously invested into the
CO gas stream. Now if CO recycling can reduce the input CO from 12,500 grams to 4.67 grams (the minimum stoichiometric
quantity as given by (1)) this would improve the degree of perfection to (39.1kJ/g)/ (4.67g x 9.82kJ/g + 12,040kJ/g) = 3.2 x 10-3.
This is about an order of magnitude improvement, but still low because of the complete loss of the invested physical exergy. A
further improvement could involve the preheating of the incoming CO gas stream using some of this lost exergy. In general, the
degree of perfection measure for the performance of other synthesis reactions for CNT are also quite low (on the order of 10-3 to
10-4) owning to; 1) the one time use of large quantities of high exergy material inputs – primarily the carbon source inputs, and 2)
the high physical exergy requirements – most processes are performed at high temperatures. However, these low values are still
quite highcompared to some semi conductor processes, which can be in the range of 10-5 and 10-6 for SiO2 processes, see [5],
[6]. The main difference is due to the relatively high standard chemical exergy of CNTs.
VII. Closing Comments
One purpose of this paper was to examine the minimum exergy requirements to make carbon nanotubes. We find that
while the exergy requirements are high, they are falling at a rather fast rate due to process improvements and could fall still more
in the future. This exercise underlines the challenges of trying to perform a Life Cycle Assessment of an evolving technology.
Early in the life of a new technology one may be following a moving target. We believe that the results given here help explain
some of the variation seen in early LCI reports as given in Table 1.
Note that the values reported here are only for the synthesis part of the nanotube production process. Furthermore these
values are for minimum exergy requirements, not actual. To make a full estimate one would have to consider: 1) the exergy
required to make the input materials. Because of the purity requirements for some of these inputs, this is likely to be very large.
For example according to Williams et al [16] for gases with purities in the 0.1 ppm level, the energy required for purification can
in the range of 20 – 200 GJ/g. (These are very high energy requirements indeed!) In addition, 2) the carbon nanotube purification
step needs to be added, including the effect of yield losses. And 3) the minimum synthesis values given here need to be increased
to account for losses in the synthesis step. Finally, 4) additional energy required for infrastructure needs to be added
(environmental conditioning etc), and 5) losses at the electric utility need also to be added. Taking this into account it is quite
reasonable to expect an order of magnitude estimate of the embodied energy requirements for carbon nanotubes to be in the
region of 0.1-1.0 TJ/kg. Such a high value compared to other materials would make this one of the most energy intensive
materials known to humankind. See for example [1], [18]. Ironically this enormous specific energy requirement constitutes only a
very small fraction of the manufacturing costs (< 1% as discussed by Healy [2] and Isaacs [15]). For example, say the energy cost
for making carbon nanotubes is on the order of 36GJ of electricity per kilogram or 36MJ/g.
This is equal to 10 kWh/g. Now at 7 cents a kilowatt hour this yields a cost of 70 cents per gram. But carbon nanotubes
can sell for around $300/g. In other words, the electricity cost in this case is on the order of 0.2% of the price, and according to a
recent cost study, energy costs for all manufacturing processes for nanotubes result in about 1% of the cost [15]. It appears that
new manufacturing processes can produce novel products with high demand resulting in a value that far exceeds the energy
(electricity) cost. At the same time however, since our current electricity supply comes primarily from fossil fuels, most of the
environmental impacts associated with these materials (e.g. global warming, acidification, mercury emissions) are related to this
use of electricity [15]. How can we reconcile this inconsistency? One comment would be that the current price for carbon
nanotubes may well be inflated due to the rather substantial government funds for nanotechnology research worldwide. Another
comment, of course, is that, from an environmental perspective, electricity from fossil fuels is vastly underpriced. That is, the
environmental and health externalities associated with the use of fossil fuels are not included in the price of electricity.
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5. International Journal Of Computational Engineering Research (ijceronline.com) Vol. 2 Issue. 8
References
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[14] T.G.Gutowski and D.P. Sekulic, “The thermodynamic analysis of manufacturing processes”, chapter in Thermodynamics
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[15] J.A.Isaacs, A. Tanwani, M.L. Healy, “Economic assessment of single-walled carbon nanotube processes”, J. Nanopart
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Manufacturing, ISEE, IEEE 2008
[17] V. Smil, Energy in Nature and Society, MIT Press 2008.
[18] M.F. Ashby, Materials and the Environment – Eco- Informed Material Choice, Elsevier Inc., 2009. Fig. 2 Evolution of the
HiPco process development over time in terms of the calculated minimum theoretical physical exergy requirements and
estimated actual exergy over a nine year period. IEEE, International Symposium on Sustainable Systems and
Technologies, Washington D.C., May 16-19, 2010 Fig. 3a. Energy intensity (J/kg) Vs process rate (kg/hr) for 20 different
processes. Data and References cited in the figure are from Ref. [6]. Fig 3b. Energy intensity (J/kg) Vs process rate
(kg/hr) for the production for Carbon Nano-fibers. See Table 3 and text.
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