Abstract: Due to the complexity of olefinic plants, various environmental pollutants exist such as NOx, CO2, Tar Water, and most importantly Spent Caustic. In this paper, instead of investigating ways of treating this pollutant, we evaluated the production in relation to plant’s variable items. We primarily discussed the factors affecting the quality of the output spent caustic such as impurities in the feed of olefin plant, the amount of injected dimethyl disulfide (DMDS) in furnaces, variation in feed composition, differences among gas temperatures and the concentration of caustic solution at the bottom of the tower. The results of the laboratory proved that in the formation of Red Oil, 1,3butadiene and acetaldehyde followed free radical and aldol condensation mechanism respectively. By increasing the injection rate of DMDS, Mercaptide amount increases in the effluent. In addition, pyrolysis gasoline accumulation is directly related to caustic concentration in the tower. Increasing naphtenes in the liquid feed augments the amount of 1,3butadiene, as one of the sources of Red Oil formation. By increasing the oxygenated compound in the feed, the rate of acetaldehyde formation, as the main source of Red Oil formation, increases.
Abstract: Scrubbing by a liquid spraying is one of the most
effective processes used for removal of fine particles and soluble
gas pollutants (such as SO2, HCl, HF) from the flue gas. There are
many configurations of scrubbers designed to provide contact
between the liquid and gas stream for effectively capturing
particles or soluble gas pollutants, such as spray plates, packed bed
towers, jet scrubbers, cyclones, vortex and venturi scrubbers. The
primary function of venturi scrubber is the capture of fine particles
as well as HCl, HF or SO2 removal with effect of the flue gas
temperature decrease before input to the absorption column. In this
paper, sulfur dioxide (SO2) from flue gas was captured using new
design replacing venturi scrubber (1st degree of wet scrubbing).
The flue gas was prepared by the combustion of the carbon
disulfide solution in toluene (1:1 vol.) in the flame in the reactor.
Such prepared flue gas with temperature around 150°C was
processed in designed laboratory O-element scrubber. Water was
used as absorbent liquid. The efficiency of SO2 removal, pressure
drop and temperature drop were measured on our experimental
device. The dependence of these variables on liquid-gas ratio was
observed. The average temperature drop was in the range from
150°C to 40°C. The pressure drop was increased with increasing of
a liquid-gas ratio, but no too much as for the common venturi
scrubber designs. The efficiency of SO2 removal was up to 70 %.
The pressure drop of our new designed wet scrubber is similar to
commonly used venturi scrubbers; nevertheless the influence of
amount of the liquid on pressure drop is not so significant.
Abstract: An efficient and green method for oxidation of thiols
to the corresponding disulfides is reported using ionic liquid
[HSO3N(C2H4OSO3H)3] in the presence of free nano-Fe2O3 at 60°C.
Ionic liquid is selective oxidant for S-S Coupling variety aliphatic
and aromatic of thiols to corresponding disulfide in the presence of
free nano-Fe2O3 as recoverable catalyst. Reaction has been performed
in methanol as an inexpensive solvent. This reaction is clean and easy
work-up with no side reaction.
Abstract: The relationship between different types of Molybdenum disulfide greases under extreme pressure loading and different speed situations have been studied using Design of Experiment (DOE) under 1200rpm steady state rotational speed and cyclic frequencies between 2400 and 1200rpm using a Plint machine software to set up the different rotational speed situations.
Research described here is aimed at providing good friction and wear performance while optimizing cyclic frequencies and MoS2 concentration due to the recent concern about grease behavior in extreme pressure applications. Extreme load of 785 Newton was used in conjunction with different cyclic frequencies (2400rpm -3.75min, 1200rpm -7.5min, 2400rpm -3.75min, 1200rpm -7.5min), to examine lithium based grease with and without MoS2 for equal number of revolutions, and a total run of 36000 revolutions; then compared to 1200rpm steady speed for the same total number of revolutions. 4 Ball wear tester was utilized to run large number of experiments randomly selected by the DOE software. The grease was combined with fine grade MoS2 or technical grade then heated to 750C and the wear scar width was collected at the end of each test. DOE model validation results verify that the data were very significant and can be applied to a wide range of extreme pressure applications. Based on simulation results and Scanning Electron images (SEM), it has been found that wear was largely dependent on the cyclic frequency condition. It is believed that technical grade MoS2 greases under faster cyclic speeds perform better and provides antiwear film that can resist extreme pressure loadings. Figures showed reduced wear scars width and improved frictional values.
Abstract: Pyrite (FeS2) is a promising candidate for cathode
materials in batteries because of it`s high theoretical capacity, low
cost and non-toxicity. In this study, nano size iron disulfide thin film
was prepared on graphite substrate through a new method as battery
cathode. In this way, acetylene black and poly vinylidene fluoride
were used as electron conductor and binder, respectively. Fabricated
thin films were analyzed by XRD and SEM. These results and
electrochemical data confirm improvement of battery discharge
capacity in comparison with commercial type of pyrite.
Abstract: Carbon disulfide is widely used for the production of
viscose rayon, rubber, and other organic materials and it is a
feedstock for the synthesis of sulfuric acid. The objective of this
paper is to analyze possibilities for efficient production of CS2 from
sour natural gas reformation (H2SMR) (2H2S+CH4 =CS2 +4H2) .
Also, the effect of H2S to CH4 feed ratio and reaction temperature on
carbon disulfide production is investigated numerically in a
reforming reactor. The chemical reaction model is based on an
assumed Probability Density Function (PDF) parameterized by the
mean and variance of mixture fraction and β-PDF shape. The results
show that the major factors influencing CS2 production are reactor
temperature. The yield of carbon disulfide increases with increasing
H2S to CH4 feed gas ratio (H2S/CH4≤4). Also the yield of C(s)
increases with increasing temperature until the temperature reaches
to 1000°K, and then due to increase of CS2 production and
consumption of C(s), yield of C(s) drops with further increase in the
temperature. The predicted CH4 and H2S conversion and yield of
carbon disulfide are in good agreement with result of Huang and TRaissi.
Abstract: Hydrodesulfurization (HDS) of dibenzothiophene
(DBT) in a high pressure batch reactor was done at 320 °C on
CoMoS/Al2O3-B2O3 (4, 10, and 16 wt. % of Boria) using nhexadecane
as solvent, dimethyldisulfide (DMDS) in tetradecane as
sulfur agent, and stirring at 1000 rpm. The effects of boria were
investigated by using X-ray diffraction (XRD), Temperature
programmed desorption (TPD) of ammonia, and Brunauer-Emmet-
Teller (BET) experiments. The results showed that the catalyst
prepared with low boria content (4 wt. %) had HDS activity (in
pseudo first order kinetic constant basis) value ~1.45 times higher to
that of CoMoS/Al2O3 catalyst.
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.