Browsing by Author "Cholakov G."

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Analysis of hybrid separation schemes for levulinic acid separation by process intensification and assessment of thermophysical properties impact
    (2023-04-01) Tronci S.; Garau D.; Stateva R.P.; Cholakov G.; Wakeham W.A.; Errico M.
    From the time levulinic acid was listed as one of the top-12 building blocks for the sugars-high value compounds conversion, the interest in this compound increased. As part of its possible production route, the definition of viable separation schemes appears of paramount importance in the overall development of levulinic acid exploitation. Hybrid sequences where liquid-liquid extraction is followed by distillation were considered proving how the direct and direct -indirect separation schemes appeared to be the best alternatives in terms of total annual cost and environmental impact. These alternatives were further analyzed to improve their design by complementing the process simulator database with thermophysical experimental values. After obtaining a reliable design for the hybrid direct and direct-indirect configurations used as benchmarks, two intensified alternatives were generated. The first intensified configuration is classified as thermodynamically equivalent sequence, while the second one includes a divided wall column. For both, it was achieved a reduction of the total annual cost of 11% without any penalty for the environmental impact compared to the reference case.
  • No Thumbnail Available
    Item
    Esterification of mixtures of pure fatty acids with methanol
    (2013-11-05) Cholakov G.; Yanev S.; Markov V.; Stoyanov S.
    Extracts from secondary biomass, e. g. spent coffee grounds (SCG), can be utilized in the production of biodiesel additives (esters of fatty acids with low molecular mass alcohols). However, they contain a significant amount of free fatty acids, so the transesterification of their glycerides has to be preceded by catalytic esterification of these acids. SCG extracts are essentially a mixture of compounds with approximately equal amounts of glycerides with saturated and unsaturated fatty acid moieties, so their iodine values are much lower than those of the typical highly unsaturated biodiesel feedstocks - e.g., sunflower oil, soybean oil, etc. In the wider context of our studies on the preparation of renewable fuel additives from SCG and other extracts from secondary biomass, this work presents results on direct esterification of mixtures of pure fatty acids, modeling the unsaturation of such extracts. They are also relevant to the utilization of biodiesel feedstocks, consisting entirely or predominantly of fatty acids like tall oil, soapstock and synthetic fatty acids, etc.
  • No Thumbnail Available
    Item
    Extracts from coffee by-products as potential raw materials for fuel additives and carbon adsorbents
    (2013-11-05) Cholakov G.; Toteva V.; Nikolov R.; Uzunova S.; Yanev S.
    Data about coffee consumed world-wide are somewhat contradictory. A conservative estimate, suggests a number of around 8 mln tones per year. Its production involves a comparable amount of by-products, mainly pulp, husks, skins and spent coffee grounds. Thus, a sustainable coffee industry requires the development of methods for utilization of coffee by-products. Among these, the preparation of renewable fuel additives (e.g. biodiesel) and carbon adsorbents is a promising alternative to the eventual dumping of biogenic substances, harmful to the environment. Extraction of coffee by-products is the first step towards their utilization. This work presents results on laboratory extraction of spent coffee grounds (SCG) with different solvents, discussed in the context of the preparation of renewable fuel additives. The aim of the present study is to develop a procedure for extraction of coffee residues, suitable for production of biofuels and adsorbents.