Abstract: Three alumina-supported Pt-Sn catalysts have been
prepared by means of co-impregnation and characterized by XRD and
N2 adsorption. The influence of catalyst composition and reaction
conditions on the conversion and selectivity were investigated in the
hydrogenation of acetic acid in an isothermal integral fixed bed
reactor. The experiments were performed on the temperature interval
468-548 K, liquid hourly space velocity (LHSV) of 0.3-0.7h-1,
pressures between 1.0 and 5.0Mpa. A good compromise of
0.75%Pt-1.5%Sn can act as an optimized acetic acid hydrogenation
catalyst, and the conversion and selectivity can be tuned through the
variation of reaction conditions.
Abstract: Green propellants used for satellite-level propulsion
system become attractive in recent years because the non-toxicity and
lower requirements of safety protection. One of the green propellants,
high-concentration hydrogen peroxide H2O2 solution (≥70% w/w,
weight concentration percentage), often known as high-test peroxide
(HTP), is considered because it is ITAR-free, easy to manufacture and
the operating temperature is lower than traditional monopropellant
propulsion. To establish satellite propulsion technology, the National
Space Organization (NSPO) in Taiwan has initialized a long-term
cooperation project with the National Cheng Kung University to
develop compatible tank and thruster. An experimental propulsion
payload has been allocated for the future self-reliant satellite to
perform orbit transfer and maintenance operations. In the present
research, an 1-Newton thruster prototype is designed and the thrusting
force is measured by a pendulum-type platform. The preliminary
hot-firing test at ambient environment showed the generated thrust and
the specific impulse are about 0.7 Newton and 102 seconds,
respectively.
Abstract: Computational study of two dimensional supersonic reacting hydrogen-air flows is performed to investigate the nitrogen effects on ignition delay time for premixed and diffusion flames. Chemical reaction is treated using detail kinetics and the advection upstream splitting method is used to calculate the numerical inviscid fluxes. The results show that just in stoichiometric condition for both premixed and diffusion flames, there is monotone dependency of the ignition delay time to the nitrogen addition. In other situations, the optimal condition from ignition viewpoint should be found using numerical investigations.
Abstract: The present energy situation and the concerns
about global warming has stimulated active research interest
in non-petroleum, carbon free compounds and non-polluting
fuels, particularly for transportation, power generation, and
agricultural sectors. Environmental concerns and limited
amount of petroleum fuels have caused interests in the
development of alternative fuels for internal combustion (IC)
engines. The petroleum crude reserves however, are declining
and consumption of transport fuels particularly in the
developing countries is increasing at high rates. Severe
shortage of liquid fuels derived from petroleum may be faced
in the second half of this century. Recently more and more
stringent environmental regulations being enacted in the USA
and Europe have led to the research and development
activities on clean alternative fuels. Among the gaseous fuels
hydrogen is considered to be one of the clean alternative fuel.
Hydrogen is an interesting candidate for future internal
combustion engine based power trains. In this experimental
investigation, the performance and combustion analysis were
carried out on a direct injection (DI) diesel engine using
hydrogen with diesel following the TMI(Time Manifold
Injection) technique at different injection timings of 10
degree,45 degree and 80 degree ATDC using an electronic
control unit (ECU) and injection durations were controlled.
Further, the tests have been carried out at a constant speed of
1500rpm at different load conditions and it can be observed
that brake thermal efficiency increases with increase in load
conditions with a maximum gain of 15% at full load
conditions during all injection strategies of hydrogen. It was
also observed that with the increase in hydrogen energy share
BSEC started reducing and it reduced to a maximum of 9% as
compared to baseline diesel at 10deg ATDC injection during
maximum injection proving the exceptional combustion
properties of hydrogen.
Abstract: Carboneous catalytical methane decomposition is an
attractive process because it produces two valuable products:
hydrogen and carbon. Furthermore, this reaction does not emit any
green house or hazardous gases. In the present study, experiments
were conducted in a thermo gravimetric analyzer using Fluka 05120
as carboneous catalyst to analyze its effectiveness in methane
decomposition. Various temperatures and methane partial pressures
were chosen and carbon mass gain was observed as a function of
time. Results are presented in terms of carbon formation rate,
hydrogen production and catalytical activity. It is observed that there
is linearity in carbon deposition amount by time at lower reaction
temperature (780 °C). On the other hand, it is observed that carbon
and hydrogen formation rates are increased with increasing
temperature. Finally, we observed that the carbon formation rate is
highest at 950 °C within the range of temperatures studied.
Abstract: Hydrogen is an important chemical in many industries
and it is expected to become one of the major fuels for energy
generation in the future. Unfortunately, hydrogen does not exist in its
elemental form in nature and therefore has to be produced from
hydrocarbons, hydrogen-containing compounds or water.
Above its critical point (374.8oC and 22.1MPa), water has lower
density and viscosity, and a higher heat capacity than those of
ambient water. Mass transfer in supercritical water (SCW) is
enhanced due to its increased diffusivity and transport ability. The
reduced dielectric constant makes supercritical water a better solvent
for organic compounds and gases. Hence, due to the aforementioned
desirable properties, there is a growing interest toward studies
regarding the gasification of organic matter containing biomass or
model biomass solutions in supercritical water.
In this study, hydrogen and biofuel production by the catalytic
gasification of 2-Propanol in supercritical conditions of water was
investigated. Pt/Al2O3and Ni/Al2O3were the catalysts used in the
gasification reactions. All of the experiments were performed under a
constant pressure of 25MPa. The effects of five reaction temperatures
(400, 450, 500, 550 and 600°C) and five reaction times (10, 15, 20,
25 and 30 s) on the gasification yield and flammable component
content were investigated.
Abstract: Recent progress in calculation of the one-loop selfenergy
of the electron bound in the Coulomb field is summarized.
The relativistic multipole expansion is introduced. This expansion
is based on a single assumption: except for the part of the time
component of the electron four-momentum corresponding to the
electron rest mass, the exchange of four-momentum between the
virtual electron and photon can be treated perturbatively. For non Sstates
and normalized difference n3En −E1 of the S-states this
itself yields very accurate results after taking the method to the third
order. For the ground state the perturbation treatment of the electron
virtual states with very high three-momentum is to be avoided. For
these states one can always rearrange the pertinent expression in such
a way that free-particle approximation is allowed. Combination of
the relativistic multipole expansion and free-particle approximation
yields very accurate result after taking the method to the ninth order.
These results are in very good agreement with the previous results
obtained by the partial wave expansion and definitely exclude the
possibility that the uncertainity in determination of the proton radius
comes from the uncertainity in the calculation of the one-loop selfenergy.
Abstract: Hydrogen is regarded to play an important role in
future energy systems because it can be produced from abundant
resources and its combustion only generates water. The disposal of
waste tyres is a major problem in environmental management
throughout the world. The use of waste materials as a source of
hydrogen is particularly of interest in that it would also solve a waste
treatment problem. There is much interest in the use of alternative
feedstocks for the production of hydrogen since more than 95% of
current production is from fossil fuels. The pyrolysis of waste tyres
for the production of liquid fuels, activated carbons and gases has
been extensively researched. However, combining pyrolysis with
gasification is a novel process that can gasify the gaseous products
from pyrolysis. In this paper, an experimental investigation into the
production of hydrogen and other gases from the bench scale
pyrolysis-gasification of tyres has been investigated. Experiments
were carried using a two stage system consisting of pyrolysis of the
waste tyres followed by catalytic steam gasification of the evolved
gases and vapours in a second reactor. Experiments were conducted
at a pyrolysis temperature of 500 °C using Ni/Al2O3 as a catalyst. The
results showed that there was a dramatic increase in gas yield and the
potential H2 production when the gasification temperature was
increased from 600 to 900 oC. Overall, the process showed that high
yields of hydrogen can be produced from waste tyres.
Abstract: The recycling process of Tungsten alloy (Swarf) by
oxidation reduction technique have been investigated. The reduced
powder was pressed under a pressure 20Kg/cm2 and sintered at
1150°C in dry hydrogen atmosphere. The particle size of the recycled
alloy powder was 1-3 μm and the shape was regular at a reduction
temperature 800°C. The chemical composition of the recycled alloy
is the same as the primary Swarf.
Abstract: A computational study at the level density functional theory (DFT) was carried out to investigate the influences of Si and C-doping on the 14N and 27Al quadrupole coupling constant in the (10, 0) zigzag single ? walled Aluminum-Nitride nanotube (AlNNT). To this aim, a 1.16nm, length of AlNNT consisting of 40 Al atoms and 40 N atoms were selected where the end atoms are capped by hydrogen atom. To follow the purpose, three Si atoms and three C atoms were doped instead of three Al atoms and three N atoms as a central ring in the surface of the Si and C-doped AlNNT. At first both of systems optimized at the level of BLYP method and 6-31G (d) basis set and after that, the NQR parameters were calculated at the level BLYP method and 6-311+G** basis set in two optimized forms. The calculate CQ values for both optimized AlNNT systems, raw and Si and C-doped, reveal different electronic environments in the mentioned systems. It was also demonstrated that the end nuclei have the largest CQ values in both considered AlNNT systems. All the calculations were carried out using Gaussian 98 package of program.
Abstract: Natural gas is the most popular fossil fuel in the
current era and future as well. Natural gas is existed in underground
reservoirs so it may contain many of non-hydrocarbon components
for instance, hydrogen sulfide, nitrogen and water vapor. These
impurities are undesirable compounds and cause several technical
problems for example, corrosion and environment pollution.
Therefore, these impurities should be reduce or removed from natural
gas stream. Khurmala dome is located in southwest Erbil-Kurdistan
region. The Kurdistan region government has paid great attention for
this dome to provide the fuel for Kurdistan region. However, the
Khurmala associated natural gas is currently flaring at the field.
Moreover, nowadays there is a plan to recover and trade this gas and
to use it either as feedstock to power station or to sell it in global
market. However, the laboratory analysis has showed that the
Khurmala sour gas has huge quantities of H2S about (5.3%) and CO2
about (4.4%). Indeed, Khurmala gas sweetening process has been
removed in previous study by using Aspen HYSYS. However,
Khurmala sweet gas still contents some quintets of water about 23
ppm in sweet gas stream. This amount of water should be removed or
reduced. Indeed, water content in natural gas cause several technical
problems such as hydrates and corrosion. Therefore, this study aims
to simulate the prospective Khurmala gas dehydration process by
using Aspen HYSYS V. 7.3 program. Moreover, the simulation
process succeeded in reducing the water content to less than 0.1ppm.
In addition, the simulation work is also achieved process
optimization by using several desiccant types for example, TEG and
DEG and it also study the relationship between absorbents type and
its circulation rate with HCs losses from glycol regenerator tower.
Abstract: The aim of this study was to synthesize the single
walled carbon nanotubes (SWCNTs) and determine their hydrogen
storage capacities. SWCNTs were firstly synthesized by chemical
vapor deposition (CVD) of acetylene (C2H2) on a magnesium oxide
(MgO) powder impregnated with an iron nitrate (Fe(NO3)3·9H2O)
solution. The synthesis parameters were selected as: the synthesis
temperature of 800°C, the iron content in the precursor of 5% and the
synthesis time of 30 min. Purification process of SWCNTs was
fulfilled by microwave digestion at three different temperatures (120,
150 and 200 °C), three different acid concentrations (0.5, 1 and 1.5
M) and for three different time intervals (15, 30 and 60 min). Nitric
acid (HNO3) was used in the removal of the metal catalysts. The
hydrogen storage capacities of the purified materials were measured
using volumetric method at the liquid nitrogen temperature and gas
pressure up to 100 bar. The effects of the purification conditions such
as temperature, time and acid concentration on hydrogen adsorption
were investigated.
Abstract: The main issue in sweetening natural gas is H2S
dissociation. The present study is concerned with simulating thermal
dissociation of H2S in industrial natural gas carbon black furnace.
The comparison of calculated results against experimental
measurements shows good agreement. The results show that sulfur
derived from H2S thermal dissociation peaked at φ=0.95. H2S
thermal dissociation is enhanced in equivalence ratio upper than 1
and H2S oxidization is increased in equivalence ratio lower than 1.
H2 concentration of H2S thermal dissociation is increased with
increase of equivalence ratio up to 1. Also, H2S concentration
decreased in outlet as equivalence ratio increases. H2S thermal
dissociation to hydrogen and Sulfur reduces its toxic characteristics
and make economical benefits.
Abstract: Application of pesticides in the paddy fields has
deleterious effects on non-target organisms including cyanobacteria
which are photosynthesizing and nitrogen fixing micro-organisms
contributing significantly towards soil fertility and crop yield.
Pesticide contamination in the paddy fields has manifested into a
serious global environmental concern. To study the effect of one such
pesticide, three cyanobacterial strains; Anabaena fertilissima,
Aulosira fertilissima and Westiellopsis prolifica were selected for
their stress responses to an Organochlorine insecticide - 6, 7, 8, 9, 10,
10-hexachloro-1, 5, 5a, 6, 9, 9a-hexahydro-6, 9-methano-2, 4, 3-
benzodioxathiepine-3-oxide, with reference to their photosynthesic
pigments-chlorophyll-a and carotenoids as well as accessory
pigments-phycobiliproteins (phycocyanin, allophycocyanin and
phycoerythrin), stress induced biochemical metabolites like
carbohydrates, proteins, amino acids, phenols and enzymes-nitrate
reductase, glutamine synthetase and succinate dehydrogenase. All
the three cyanobacterial strains were adversely affected by the
insecticide doses and inhibition was dose dependent. Reduction in
photosynthetic and accessory pigments, metabolites, nitrogen fixing
and respiratory enzymes of the test organisms were accompanied
with an initial increase in their total protein at lower Organochlorine
doses. On the other hand, increased amount of phenols in all the
insecticide treated concentrations was indicative of stressed activities
of the organisms.
Abstract: An experiment of vented gas explosions involving two
different cylinder vessel volumes (0.2 and 0.0065 m3) was reported,
with equivalence ratio (Φ) ranged from 0.3 to 1.6. Both vessels were
closed at the rear end and fitted at the other side with a circular
orifice plate that gives a constant vent coefficient (K =Av/V2/3) of
16.4. It was shown that end ignition gives higher overpressures than
central ignition, even though most of the published work on venting
uses central ignition. For propane and ethylene, it is found that rich
mixtures gave the highest overpressures and these mixtures are not
considered in current vent design guidance; which the guideline is
based on mixtures giving the maximum flame temperature. A strong
influence of the vessel volume at constant K was found for methane,
propane, ethylene and hydrogen-air explosions. It can be concluded
that self- acceleration of the flame, which is dependent on the
distance of a flame from the ignition and the ‘suction’ at the vent
opening are significant factors affecting the vent flow during
explosion development in vented gas explosion. This additional
volume influence on vented explosions is not taken into account in
the current vent design guidance.
Abstract: In order to investigate a PROX microreactor
performance, two-dimensional modeling of the reacting flow
between two parallel plates is performed through a finite volume
method using an improved SIMPLE algorithm. A three-step surface
kinetics including hydrogen oxidation, carbon monoxide oxidation
and water-gas shift reaction is applied for a Pt-Fe/γ-Al2O3 catalyst
and operating temperatures of about 100ºC. Flow pattern, pressure
field, temperature distribution, and mole fractions of species are
found in the whole domain for all cases. Also, the required reactive
length for removing carbon monoxide from about 2% to less than 10
ppm is found. Furthermore, effects of hydraulic diameter, wall
temperature, and inlet mole fraction of air and water are investigated
by considering carbon monoxide selectivity and conversion. It is
found that air and water addition may improve the performance of
the microreactor in carbon monoxide removal in such operating
conditions; this is in agreement with the pervious published results.
Abstract: In pressure vessels contain hydrogen, the role of
hydrogen will be important because of hydrogen cracking problem. It
is difficult to predict what is happened in metallurgical field spite of a
lot of studies have been searched. The main role in controlling the
mass diffusion as driving force is related to stress. In this study, finite
element analysis is implemented to estimate material-s behavior
associated with hydrogen embrittlement. For this purpose, one model
of a pressure vessel is introduced that it has definite boundary and
initial conditions. In fact, finite element is employed to solve the
sequentially coupled mass diffusion with stress near a crack front in a
pressure vessel. Modeling simulation intergrarnular fracture of AISI
4135 steel due to hydrogen is investigated. So, distribution of
hydrogen and stress are obtained and they indicate that their
maximum amounts occur near the crack front. This phenomenon is
happened exactly the region between elastic and plastic field.
Therefore, hydrogen is highly mobile and can diffuse through crystal
lattice so that this zone is potential to trap high volume of hydrogen.
Consequently, crack growth and fast fracture will be happened.
Abstract: Foodborne Salmonella infections have become a
major problem world wide. Salmonellosis transmitted from fish are
quite common. Established quality control measures exist for export
oriented fish, none exists for fish consumed locally. This study aimed
at characterization of Salmonella isolated from Nile tilapia . The
study was carried out in selected beaches along L. Victoria in
Western Kenya between March and June 2007. One hundred and
twenty fish specimens were collected. Salmonella isolates were
confirmed using serotyping, biochemical testing in addition to malic
acid dehydrogenase (mdh) and fliC gene sequencing. Twenty
Salmonella isolates were confirmed by mdh gene sequencing. Nine
(9) were S. enterica serotype typhimurium, four (4) were S. enterica
Serotype, enteritidis and seven (7) were S. enterica serotype typhi.
Nile tilapia have a role in transmission of Salmonellosis in the study
area, poor sanitation was a major cause of pollution at the beach
inshore waters.
Abstract: By analyzing the sources of energy and power
loss in PWM (Pulse Width Modulation) controlled drivers of
water electrolysis cells, it is possible to reduce the power
dissipation and enhance the efficiency of such hydrogen
production units. A PWM controlled power driver is based on
a semiconductor switching element where its power
dissipation might be a remarkable fraction of the total power
demand of an electrolysis system. Power dissipation in a
semiconductor switching element is related to many different
parameters which could be fitted into two main categories:
switching losses and conduction losses. Conduction losses are
directly related to the built, structure and capabilities of a
switching device itself and indeed the conditions in which the
element is handling the switching application such as voltage,
current, temperature and of course the fabrication technology.
On the other hand, switching losses have some other
influencing variables other than the mentioned such as control
system, switching method and power electronics circuitry of
the PWM power driver. By analyzings the characteristics of
recently developed power switching transistors from different
families of Bipolar Junction Transistors (BJT), Metal Oxide
Semiconductor Field Effect Transistors (MOSFET) and
Insulated Gate Bipolar Transistors (IGBT), some
recommendations are made in this paper which are able to
lead to achieve higher hydrogen production efficiency by
utilizing PWM controlled water electrolysis cells.
Abstract: The modified Claus process is the major technology
for the recovery of elemental sulfur from hydrogen sulfide. The
chemical reactions that can occur in the reaction furnace are
numerous and many byproducts such as carbon disulfide and carbon
carbonyl sulfide are produced. These compounds can often contribute
from 20 to 50% of the pollutants and therefore, should be hydrolyzed
in the catalytic converter. The inlet temperature of the first catalytic
reactor should be maintained over than 250 °C, to hydrolyze COS
and CS2. In this paper, the various configurations for the first
converter reheating of sulfur recovery unit are investigated. As a
result, the performance of each method is presented for a typical
clause unit. The results show that the hot gas method seems to be
better than the other methods.