TiO<Subscript>2</Subscript>-based shaped catalyst for the recovery of elemental sulfur from H<Subscript>2</Subscript>S and SO<Subscript>2</Subscript> gas streams

The Claus process has been used for the conversion of H₂S and SO₂ to elemental sulfur. These two sulfur compounds need special attention because they are very poisonous with negative impact on both the environment and human health. Here, highly active Fe–Ni/TiO₂ catalyst has been prepared and shaped by three different binders (bentonite, polyethylene glycol and carboxymethyl cellulose) into extrudes. Comparing the mechanical strength and surface area of prepared extrudes, the optimal shaped catalyst was selected with 20% of bentonite, 2% of PEG and 2% of CMC. The optimal catalyst was characterized by X-ray powder diffraction, temperature-programmed reduction, Brunauer–Emmett–Teller specific surface area, Barrett–Joyner–Halenda, scanning electron microscopy and energy-dispersive X-ray techniques and used for sulfur recovery process. The performance of this product for sulfur recovery via Claus process was excellent with the conversion of hydrogen sulfide of 76.77% and sulfur dioxide of 97.83%. The catalyst also provides high hydrolysis activity of CS₂ (83.06%). Therefore, a highly active TiO₂-supported shaped catalyst with 85.62% of conversion efficiency has been prepared successfully to convert the small amounts of H₂S, SO₂ and CS₂ to elemental sulfur.     

Larger Foraminiferal Biostratigraphy and Facies Analysis of the Oligocene–Miocene Asmari Formation in the Western Fars Sub-basin, Zagros Mountains, Iran

The Oligocene–Miocene carbonate record of the Zagros Mountains, known as the Asmari Formation, constitutes an important hydrocarbon reservoir in southern Iran. This marine carbonate succession, which developed under tropical conditions, is explored in terms of larger foraminiferal biostratigraphy, facies analysis and sequence stratigraphy in a new section at Papoon cropping out in the western Fars sub-basin, in the south-east of the Zagros belt. Facies analysis shows evidence of re-working and transport of skeletal components throughout the depositional system, interpreted here as a carbonate ramp. The foraminifera-based biozones identified include the Globigerina–Turborotalia cerroazulensis–Hantkenina Zone and Nummulites vascus–Nummulites fichteli Zone, both of Rupelian age, the Archaias asmaricus–Archaias hensoni–Miogypsinoides complanatus Zone of Chattian age and the ‘Indeterminate’ Zone of Aquitanian age. The vertical sedimentary evolution of the formation exhibits a progressive shallowing of the facies belts and thus the succession is interpreted as a high-rank low-order regressive systems tract. This long-lasting Rupelian–Aquitanian regressive event is in accordance with accepted global long-term eustatic curves. Accordingly, long-term eustatic trends would have been a factor controlling accommodation during the deposition of the Asmari Formation studied in the western Fars sub-basin.     

Determination of Geopotential Differences between Local Vertical Datums and Realization of a World Height System

The methodology developed for connecting Local Vertical Datums (LVD) was applied to the Australian Height Datum (AHD) and the North American Vertical Datum (NAVD88). The geopotential values at AHD and NAVD88 were computed and the corresponding vertical offset of 974 mm with rms 51 mm was obtained between the zero reference surfaces defined by AHD and NAVD88. The solution is based on the four primary geodetic parameters, the GPS/levelling sites and the geopotential model EGM96. The Global Height System (or the Major Vertical Datum) can be defined by a geoidal geopotential value used in the solution as the reference value, or by the geopotential value of the LVD, e.g. NAVD88.     

Differences between Mean Sea Levels for the Pacific,Atlantic and Indian Oceans From Topex/Poseidon Altimetry

Geopotential values W of the mean equipotential surfaces representing the mean ocean topography were computed on the basis of four years (1993 - 1996) TOPEX/POSEIDON altimeter data: W = 62 636 854.10m ² s ^–2 for the Pacific (P), W = 62 636 858.20m ² s ^–2 for the Atlantic (A), W = 62 636 856.28m ²s^–2 for the Indian (I) Oceans. The corresponding mean separations between the ocean levels were obtained as follows: A – P = – 42 cm, I– P = – 22 cm, I – A = 20 cm, the rms errors came out at about 0.3 cm. No sea surface topography model was used in the solution.     

Prediction of Flyrock in Mine Blasting: A New Computational Intelligence Approach

Natural Resources Research - Blasting is the predominant rock fragmentation technique in civil constructions, underground and surface mines. Flyrock is the unwanted throw of rock fragments during...     

Model tree approach for prediction of pile groups scour due to waves

Scour around piles could endanger the stability of the structures placed on them. Hence, an accurate estimation of the scour depth around piles is very important in coastal and marine engineering. Due to the complex interaction between the wave, seabed and pile group; prediction of the scour depth is not an easy task and the available empirical formulas have limited accuracy. Recently, soft computing methods such as Artificial Neural Networks (ANNs) and Support Vector Machines (SVMs) have been used for the prediction of the scour depth. However, these methods do not give enough insight about the process and are not as easy to use as the empirical equations. In this study, new formulas are given that are easy to use, accurate and physically sound. Available empirical equations for estimating the pile group scour depth such as those of Sumer et al. (1992) and Bayram and Larson (2000), are less accurate compared to the given equations. These equations are as accurate as other soft computing methods such as ANN and SVM. Moreover, in this study, safety factors are given for different levels of acceptable risks, which can be so useful for engineers.     

Determination of the Geopotential Scale Factor from TOPEX/POSEIDON Satellite Altimetry

The geopotential scale factor R _o = GM/W _o (the GM geocentric gravitational constant adopted) and/or geoidal potential Wo have been determined on the basis of the first year's (Oct 92 – Dec 93) ERS-1/TOPEX/POSEIDON altimeter data and of the POCM 4B sea surface topography model: R _o °=(6 363 672.58°±0.05) m, W _o °=(62 636 855.8°±0.05)m ² s ^–2 . The 2°–°3 cm uncertainty in the altimeter calibration limits the actual accuracy of the solution. Monitoring dW _o /dt has been projected.     

Acid-treated zeolite (clinoptilolite) and its potential to zinc removal from water sample

Zinc compounds are important group of pollutants which enter water flows from industrial factories sewage. In this research, use of both natural zeolite (clinoptilolite) and its sulfuric acid-modified form as a cheap adsorbent for removing zinc from its solutions has been investigated. The effect of acid concentration, contact duration, pH of solution, initial concentration of zinc, amount of adsorbent and its size was investigated. On average, the maximum adsorption amount is calculated to be 91.1 % with contact duration of 300 min. By increasing contact duration, more adsorption is achieved. Results show that if the more zeolite is used, the more adsorption is achieved. According to results, Langmuir and Freundlich isotherm models were investigated and the adsorption of zinc by modified zeolite was described by both models very well.