Burgas University

Burgas, Bulgaria

Burgas University

Burgas, Bulgaria
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Koleva B.B.,Ruhr University Bochum | Koleva B.B.,TU Dortmund | Kolev T.,TU Dortmund | Tsanev T.,Burgas University | And 4 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2010

The novel 3-phenylpyridinium hydrogensquarate (1) has been synthesized and its structure and properties are elucidated spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid-state IR-spectroscopy, UV-spectroscopy, TGA, DSC, DTA and ESI MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and electronic spectrum. 3-Phenylpyridinium hydrogensquarate, crystallizes in the space group P-1 and the ions in the unit cell are joined into layers by intermolecular NH⋯O{double bond, long}C(Sq) bonds with bond lengths of 2.625 and 2.626 Å, respectively. Hydrogentartarates form dimers by strong O{double bond, long}COH⋯OCO interactions (2.499 Å). © 2009 Elsevier B.V. All rights reserved.

Tasheva Y.,Burgas University
Petroleum and Coal | Year: 2013

Sulfur content of diesel fuel has been cut down to ultra low levels by environmental regulation in many countries with the aim of reducing diesel engine's harmful emissions and improving air quality. As a result, research on the production of ultra low sulfur diesel has gained enormous interest in the scientific community worldwide. The present paper considered some possibilities for decreasing of sulfur content in diesel fractions by different methods. It's established that extraction processes with selective solvents decrease sulfur content in different degree. It was calculated distribution coefficients of the systems. It was applying an adsorption process for purifying of middle distillated fractions from unlikely components. The obtained results show the possibility for looking for new techniques for optimization of the adsorption process.

Stratiev D.S.,Lukoil | Dinkov R.K.,Lukoil | Shishkova I.K.,Lukoil | Nedelchev A.D.,Lukoil | And 8 more authors.
Petroleum Science and Technology | Year: 2015

Thirty-four heavy oils originating from the four main groups of crude oils around the world - I group: light, low sulfur (30-400 API; S ≤ 0.5% mass); II group: light sulfur (30-400 API; S = 0, 5-1.5% mass); III group: heavy, high sulfur (15-300 API; S = 1.5, 3.1% mass); IV group: extra heavy, high sulfur (150 API, S ≥ 3% mass) - were investigated for distribution of boiling point and molecular weight. The three-parameter distribution model of Riazi and the four-parameter Webull extreme distribution function were tested to approximate the distribution of the heavy oil properties mentioned. It was found that the Weibull extreme more accurately approximates the heavy oil boiling point distribution up to temperatures of 750°C, and molecular weight distribution up to 955 g/mol. To approximate distribution of higher values extrapolation is needed. Riazi's distribution model was found to be more precise in the extrapolation than the Weibull extreme. © 2015 Taylor & Francis Group, LLC.

Al Rawi S.A.,Burgas University | Aidan A.,American University of Sharjah | Nenov V.,Burgas University
Desalination and Water Treatment | Year: 2016

The main objective of this research was to study the effect of coagulation on membrane performance by assessing the effect of retention of fine suspended and colloidal matter contained in industrial wastewater. Hybrid process was studied to show the improved efficiency of the coagulation–membrane filtration. It was found that some positively charged fine materials are forming a deposit on the inner surface area of the membrane that leads to its fast blockage, lowering the membrane performance life. In aiming to avoid such a fouling, a new technique was made from a combination between microfiltration and ultrafiltration used as a practical solution to overcome the problem. The combined process was named as micro-ultrafiltration (MUF) and investigated to check out the efficiency and the quality through the treatment plant for industrial wastewater of ceramic factory. The results showed (MF) modified devices were able to remove bacteria, cysts, and fine particles while the UF membranes were very effective to deal with viruses, color, and some colloidal natural organic matter. The whole process is aimed to find practical solution to deal with the extremely high turbidity where most of the standard process failed. The currently applied processes of treatment plant went through many modified stages starting from the equalization tank ending with UF passing through the type of coagulation/flocculation and the mixing conditions. © 2016 Balaban Desalination Publications. All rights reserved.

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