Deposition and flocculation of asphaltenes from crude oils

A crude oil has four main constituents: saturates, aromatics, resins, and asphaltenes. The asphaltenes in crude oil are the most complex and heavy organic compounds. The classic definition of asphaltenes is based on the solution properties of petroleum residuum in various solvents. Asphaltenes are a solubility range that is soluble in light aromatics such as benzene and toluene, but are insoluble in lighter paraffins. The particular paraffins, such as n-pentane and n-heptane, are used to precipitate asphaltenes from crude oil. Deposition of asphaltenes in petroleum crude and heavy oil can cause a number of severe problems. The precipitation of asphaltene aggregates can cause such severe problems as reservoir plugging and wettability reversal. Asphaltenes can precipitate on metal surface. Cleaning the precipitation site as well as possible appears to slow reprecipitation. To prevent deposition inside the reservoir, it is necessary to estimate the amount of deposition due to various factors. The processes can be changed to minimize the asphaltene flocculation, and chemical applications can be used effectively to control depositions when process changes are not cost effective. Asphaltene flocculation can be controlled through better knowledge of the mechanisms that cause its flocculation in the first place. The processes can be controlled to minimize the asphaltene flocculation, and chemical applications can be used effectively to control depositions when process changes are not cost effective.     

Heavy oil upgrading: Unlocking the future fuel supply

Currently, more than half of the oil reserves (53.3%) in the world are in the form of restorable oils such as heavy oil, extra heavy oil, oil sand, tar sands, oil shale, and bitumen. Heavy oil is one of the petroleum oil varieties that contain long chain hydrocarbons. All types of heavy oils contain asphaltenes and thus are considered very dense substances. The asphaltenes are one of the most complex and heavy organic compounds present in the heavy oil. The heavy oil is defined as one having an American Petroleum Institute scale index equal or smaller than 20°. In conventional refining procedures, heavy oil poses many challenges. Recycling and re-refining are applied techniques for the processing of petroleum based heavy oils into reusable light oils such as gasoline and diesel fuel. In this regard, catalytic pyrolysis and thermal cracking are promising technologies for light oil production. The authors review the heavy oil upgrading processes and their associated challenges with ambition to find cost-effective ways to ensure a constant future fuel supply.     

Removing of resins from crude oils

Crude oil contains four chemical group classes, namely saturates, aromatics, resins, and asphaltenes (SARA fractions). Resins fraction of crude oil comprises polar molecules often containing heteroatoms such as nitrogen, oxygen, or sulfur. Resin is a heavier fraction than aromatics and saturates. Resins are composed of fused aromatic rings with branched paraffin and polar compounds. The resin fraction is soluble in light alkanes such as pentane and heptane, but insoluble in liquid propane. The resins are adsorbed on a solid such as alumina, clay, or silica, and subsequently recovered by use of a more polar solvent and the oils (aromatics and saturates) remain in solution. The resins often coprecipitate with the asphaltenes in controlled propane deasphalting procedures. The composition of the resins can vary considerably and is dependent on the kind of precipitating liquid and on the temperature of the liquid system. The resins are adsorbed on a solid such as alumina, clay, or silica, and subsequently recovered by use of a more polar solvent and the oils (aromatics and saturates) remain in solution.     

Experimental studies on mushroom and pollen drying

In this study, drying periods of mushrooms and pollens (for Anzer honey) were investigated. The experiments of mushrooms were carried out under both laboratory and shady‐ and sunny‐atmospheric conditions and those of pollens were conducted in the drying cupboard heated by electric heater and under sunny atmospheric conditions. The temperature of the drying cupboard was regulated at 45°C during the drying experiment of pollen. The mass loss of pollens and the temperature of each shelf including pollens in the drying cupboard were measured. Drying curves of mushrooms and pollens for each experiment and the variation of the mass change ratio, the moisture ratio of pollens and the temperatures in the shelves with drying time were presented, respectively. Furthermore, their equations of drying curves and the average experimental uncertainty ratios were calculated based on the experimental results. It was concluded that mushrooms can be dried in the cupboards by using hot air at 50°C in a time period of 5–6 h, and the dried must be protected in vacuum, and the pollens also must be dried at temperatures between 40 and 45°C in a time period of 2·5–3 h without their losing the colour, flavour, smell and structure. The average experimental uncertainty ratio of mushrooms and pollens during the drying process were calculated to be 22 and 18%, respectively. Copyright © 1999 John Wiley & Sons, Ltd.     

Controlling tip–sample interaction forces during a single tap for improved topography and mechanical property imaging of soft materials by AFM

We introduce a method that exploits the “active” nature of the force-sensing integrated readout and active tip (FIRAT), a recently introduced atomic force microscopy (AFM) probe, to control the interaction forces during individual tapping events in tapping mode (TM) AFM. In this method the probe tip is actively retracted if the tip–sample interaction force exceeds a user-specified force threshold during a single tap while the tip is still in contact with the surface. The active tip control (ATC) circuitry designed for this method makes it possible to control the repulsive forces and indentation into soft samples, limiting the repulsive forces during the scan while avoiding instability due to attractive forces. We demonstrate the accurate topographical imaging capability of this method on suitable samples that possess both soft and stiff features.     

Gabapentin-induced coma in a patient with renal failure

We describe a 60-year-old woman who became comatose after a single dose of gabapentin for right-sided sciatalgia. The patient was improved by hemodialysis. Gabapentin toxicity should be considered when mental status changes develop in patients with renal failure after even a single dose.     

A technical review of building-mounted wind power systems and a sample simulation model

Small scale wind turbines installed within the built environment is classified as micro generation technology. This paper reports the investigation results of wind power application in buildings. First, general information is given for common type of wind turbines are used on buildings. Second, the wind aerodynamics and wind flows over the buildings are investigated based on local meteorological data and local building characteristics. However, to receive the highest potential wind energy resource and avoid turbulent areas, the tool of Computational Fluid Dynamics (CFD) has to be used to model the annual wind flows over buildings to help analyze, locate, and design wind turbines on and around buildings. Three different sample models for buildings and rural residential areas are explained with CFD models.     

Preservation initiatives for the truncated pyramid-shaped traditional housesof Siirt,Turkey

The traditional houses of the residential areas in and around Siirt in the southeastern region of Turkey are notable because of their interesting forms. The most successful examples are the "truncated pyramidal-shaped houses" that have existed for centuries and are unique to the locality; however, these forms are demolished rapidly. In this study, the structures of small- scale settlements in Siirt province and its environs have been evaluated to highlight the cultural aspects of the region. The subject of this research is to investigate the design principles of the rural houses constructed in vernacular style to raise international awareness of the need to preserve vernacular architecture. Surviving examples have been examined in terms of multiple case approach by their forms, spatial compositions, changes in their forms over time, their layouts in urban and rural areas, the construction techniques used to produce them from material production through implementation, the composition of the living space and its uses, their differences or similarities to other houses in the region and their aesthetic details. The research reveals that the design principles of traditional rural architecture offer the use of local material and techniques in a unique way that promote highlights to the future.     

Conversion of oil shale to liquid hydrocarbons

Oil shale is a complex fossil material that is composed of organic matter and mineral matrix. The thermal decomposition of the organic matter generates liquid and gaseous products. Oil shale is a porous rock containing kerogen, an organic bituminous material. Kerogen is a solid mixture of organic compounds that is found in certain sedimentary rocks. The kerogen can be pyrolyzed and distilled into petroleum-like oil. Oil shale and bituminous materials are suitable for obtaining petroleum-like products. The process designed in this study has the ability to control unwanted volatile materials. The mineral matter is removed from oil shale before pyrolysis. The pyrolysis of the oil shale is performed in a retort. The temperature at which the kerogen decomposes into usable hydrocarbons begins at 300°C, but the decomposition proceeds more rapidly and completely at higher temperatures. Decomposition takes place most quickly at a temperature between 475 and 525°C. Shale oil from oil shale consists of the hydrocarbons: paraffins, olefins, isoparaffins and naphthenes, isoolefins and cycloolefins, monocyclic aromatics, and poly-cyclic aromatics. The nonhydrocarbons are nitrogen, sulfur, and oxygen (NSO) compounds.