Skip to main content

Chavdar Chilev

Followers

5

Following

3

Public Views

Interests

Uploads

Papers by Chavdar Chilev

Numerical Simulation of a Valorisation-Oriented Hybrid Process for the Bio-Oil-Related Separation of Acetol and Acetic Acid

Simulation of Biodiesel Production by Transesterification of Vegetable Oils

This work presents an ChemCAD 6.0 Simulation study for biodiesel production. The simulation illus... more This work presents an ChemCAD 6.0 Simulation study for biodiesel production. The simulation illustrates the production of biofuel from pure vegetable oil with an alkaline catalyst. The main areas are transesterification, methanol separation, water washing, FAME purification, catalyst neutralization and glycerol purification. The equipment used includes in particular reactors, distillation and extraction columns and components splitters. As a result of the simulation, the two final target products-biodiesel and glycerol, are obtained with purity 98 % and 99 %, respectively. The suggested technological scheme provides a possibility for recuperation of the heat streams.

Multi-Compound H2, CH4, and N2 Adsorption Analysis

Metals, Nov 5, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more

Modelling of Single-Gas Adsorption Isotherms

Metals

The present paper reviews and analyses different models that could be used to describe the adsorp... more The present paper reviews and analyses different models that could be used to describe the adsorption equilibrium of pure gases. The adsorption equilibrium of hydrogen, nitrogen and methane is characterised and modelled. Several thermodynamic conceptions have been selected and tested for the calculation of physico-chemical parameters. The model of Dubinin has been selected to estimate the pseudo-saturation vapour pressure. The best results for the molar volume of the adsorbate have been obtained by using Do’s equation. Eight models, namely Langmuir, Freundlich, Sips, Toth, Jovanovic, UNILAN, OBMR and Potential Theory, describing the adsorption equilibrium of pure gases, have been tested and compared with experimental data obtained from the literature at three different temperatures (283 K, 298 K and 313 K). In order to determine the best fit, the correlation coefficient and the standard errors for each parameter have been used to evaluate the data. All the models used in this study,...

Microscopic Examination of Microporous Adsorbents

Food Science, Engineering and Technologies, Oct 18, 2013

Investigation of Thermal Effects by Adsorption of Hydrogen for Use in Automotive Industry

Food Science, Engineering and Technologies, Oct 15, 2010

International audienceThe possibility of application of new materials using hydrogen in automotiv... more International audienceThe possibility of application of new materials using hydrogen in automotive industry is examinated - porous materials such as activated carbon into which structure metal particles are implanted. temperature profiles were investigated for the volume of model dynamic reservoir by filling it with hydrogen. A thermodynamic analysis of the impact of thermal effetcs of adsorption and compression at different temperatures are made. We examinated the possibility of dynamic cryogenic storage of hydrogen at 77 K

A Comparison Between the Different Methods for the Measurement of an Excess Adsorption of Pure Gases on Porous Adsorbents at High Pressure

The topic of this work is to compare several experimental methods such as volumetric and volumetr... more The topic of this work is to compare several experimental methods such as volumetric and volumetric-gravimetric methods for measuring the equilibrium states of pure gases being adsorbed on the surface of solid materials. The investigation of different type methods and their advantages end disadvantages are discussed. The installations used for measuring the adsorption equilibrium by these methods are discussed in details. The installation for measuring the helium density of materials, i.e. volumetric density of solid adsorbents is also presented.

format_quoteThe volumetric-gravimetric method shows high correlation with AIR LIQUIDE Co.'s data for hydrogen adsorption, with maximum deviations of 3.5% across temperatures.format_quote

Flavonoids Extraction Kinetics, Antimicrobial Activity and Radical Scavenging Potential of Bulgarian Woundwort (Solidago virgaurea L.)

Separations

The medicinal plant woundwort (Solidago virgaurea L.) characterizes by diuretic, antimutagenic, a... more The medicinal plant woundwort (Solidago virgaurea L.) characterizes by diuretic, antimutagenic, anti-inflammatory activity and it has been applied for urinary tract, nephrolithiasis and prostate disorders treatment. The aim of the present study was to analyze the extraction kinetics of catechin, epigallocatechin and quercetin from Bulgarian woundwort extracts, to assess the antibacterial potential of the medicinal plant extracts against four bacterial strains (Staphylococcus aureus ATCC25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Bacillus cereus), their antioxidant capacity and radical scavenging potential. The concentrations of the flavonoids in the extracts obtained at different extraction conditions (solvent, temperature, extraction time) were determined by newly-developed by the scientific team RP-HPLC-PDA methodologies. The agar well diffusion method was applied to evaluate the antibacterial activity of the plant extracts. The 70% EtOH extracts at 2...

Features for the Determination of Parameters of Equilibrium Adsorption Model by a Nonlinear Regression Process of Experimental Data

A mathematical model with four parameters describing the adsorption equilibrium of supercritical ... more A mathematical model with four parameters describing the adsorption equilibrium of supercritical gases on microporous adsorbents in a wide range of pressures is studied. Numerical experiments related to determining the model parameters by nonlinear regression process of experimental data are carried out. From a physical point of view for a particular system adsorbent/adsorbat at a given temperature, these parameters are strictly defined. There was instability in determining the two of the parameters during the process of nonlinear regression related to proposed different initial values and obtained incorrect final results. The mathematical model is transformed by combining of these two parameters. Thus a three parametric model is received. The parameters of the resulting model are correctly determined during the process of nonlinear regression independently of the given initial values.

Modeling and Kinetics Study of Solid-Liquid Extraction from Leaves of Nicotiana Tabacum L

Experimental kinetics has been obtained by extraction from leaves of Nicotiana tabacum L.at perio... more Experimental kinetics has been obtained by extraction from leaves of Nicotiana tabacum L.at periodical conditions in a stirred vessel. The influence of the liquid-solid ratio and the kind of the solvent have been determined. A four parameters model for calculating the values of D eff has been found using non-linear regression of the experimental results. The diffusion model have been solved using variable D eff. There is a very good coincidence between the numerical and experimental data.

Simulation of Biodiesel Production by Transesterification of Vegetable Oils

This work presents an ChemCAD 6.0 Simulation study for biodiesel production. The simulation illus... more This work presents an ChemCAD 6.0 Simulation study for biodiesel production. The simulation illustrates the produc tion of biofuel from pure vegetable oil with an alkaline catalyst. The main areas are transesterification, methanol separation, water washing, FAME purification, catalyst neutralization and glycerol purification. The equipment used includes in particular reactors, distillation and extraction columns and components splitters. As a result of the simulation, the two final target prod ucts - biodiesel and glycerol, are obtained with purity 98 % and 99 %, respectively. The suggested technological scheme provides a possibility for recuperation of the heat streams.

format_quoteSimulation produced 900 kg/h biodiesel (purity 99.4%) and 103.78 kg/h glycerol (purity 99.63%) from 1000 kg/h vegetable oil and alkaline catalyst.format_quote

Extraction of Protodioscin from Tribulus terrestris-Optimisation of Kinetics and Modeling

Revista De Chimie, 2021

The aim of the present study was to establish the optimal conditions for protodioscin extraction ... more The aim of the present study was to establish the optimal conditions for protodioscin extraction from Tribulus terrestris plant and to investigate the possibilities of mathematical modeling of the process and calculation of the diffusion coefficients essential for the industrial scale-up and management of the extraction process. The kinetics of protodioscin extraction from Tribulus terrestris was experimentally studied at varying the solvent type (70% and 96% ethanol) and temperature (20°C, 30°C, 40°C). The optimal process conditions for these parameters were determined. The experimental results were mathematically modelled. Numerical solutions of the propsed in the study empirical model with constant and variable effective diffusivity in the solid phase, Deff, were obtained. The empirical model was based on comparative analyses with the Regular regime model solutions. It was established that the experimental data complied satisfactorily with the the resulting numerical solutions.

format_quote70% EtOH extraction yielded significantly more protodioscin; water presence enhanced extraction rate, confirming a temperature-extraction efficiency relationship.format_quote

Reactive Distillation for Ethyl Acetate Production

We describe a model and calculation technique that supports the design of reactive distillation c... more We describe a model and calculation technique that supports the design of reactive distillation columns using ChemCAD simulation software. The approach is illustrated for the production of ethyl acetate because it is inevitably needed as an active solvent used in a wide range of applications across many industries. Ethyl acetate is normally produced by esterification of ethanol and acetic acid. A reactive distillation column, combining the reaction and separation into a single stage, is proposed. The ethyl acetate is always distilled and withdrawn out of the reaction zone, the equilibrium is shifted to the right and the reactants conversion is improved. These are the advantages of this combination. Sensitive analyses are carried out to investigate the influence of the different parameters such as pressure, reflux ratio, feed stage location. The effect of reactants excess on the reactants conversion and the ethyl acetate production is also studied. The optimum operation conditions an...

Study of the biological activity of essential oils-water mixtures

This study aimed to investigate the biological activity of aqueous mixtures of two essential oils... more This study aimed to investigate the biological activity of aqueous mixtures of two essential oils. The mixtures were prepared by mixing certain amounts of lavender and clove oils with distilled water at room temperature. In the case of lavender oil, a relatively clear saturated aqueous phase was obtained after mixing with an excess of the essential oil. The clove oil formed stable oil-in-water emulsions. The antibacterial activity of the samples was tested against two model bacterial strains. The growth of the Gram-negative Escherichia coli K12 and the Gram-positive Bacillus subtilis 3562 was determined in 96-well microplates. A more prominent inhibition activity against E. coli K12 strain compared to B. subtilis 3562 for both oilwater mixtures was observed. A disk diffusion test indicated growth inhibition by the lavender oil during the tests against the Gram-positive strain (zones of around 11.7 mm) while clove oil inhibited both bacteria (12 mm B. subtilis 3562 and 13.66 mm E. co...

format_quoteClove oil emulsion at 2.33 mg/ml inhibited bacterial growth by over 90%, indicating strong antimicrobial efficacy, especially at lower concentrations initially.format_quote

Une nouvelle méthode pour la description de l’équilibre d’adsorption gaz-solide dans des conditions normales et supercritiques La dépendance des paramètres du modèle de la température

Une nouvelle approche pour la description de l’equilibre d’adsorption gaz-solide est presentee. L... more Une nouvelle approche pour la description de l’equilibre d’adsorption gaz-solide est presentee. La methode combine l’approche basee sur la mecanique quantique de la theorie classique de Polanyi et la conception de grille de gaz. Cette approche mene a un modele a trois parametres pour la description de l’equilibre. L’approche thermodynamique des parametres dependant de la temperature est egalement developpee. Une bonne coincidence entre les valeurs experimentales et calculees a partir du modele propose a ete demontree pour une large plage de variation des pressions.

Investigation of Acetic Acid Dehydration by Various Methods

Some separation methods for acetic acid dehydration, such as azeotropic distillation, extractive ... more Some separation methods for acetic acid dehydration, such as azeotropic distillation, extractive distillation and hybrid extraction/distillation process (HEDP) are investigated and further analyzed. In order to optimize the separation process, different separation agents were investigated. The phase equilibria (vapor-liquid and vapor-liquid-liquid) of the ternary system acetic acid/water/separating agent are analyzed in order to choose an appropriate thermodynamic model suitable for the simulation of the system. The results show that the azeotropic distillation is the most undesirable dehydration method among the three separation processes investigated. Almost similar results are obtained using the extractive distillation and HEDP. The latter is energetically more favorable, but the extractive distillation requires less equipment and control operations costs. Therefore, HEDP using methyl tert-butyl ether as an extraction agent is the most promising separation method for the system s...

format_quoteHEDP is identified as the most favorable method for acetic acid dehydration, outperforming azeotropic distillation and offering energy efficiency and cost advantages.format_quote

Modeling and Kinetics Study of Solid-Liquid Extraction from Leaves of Nicotiana Tabacum

Experimental kinetics has been obtained by extraction from leaves of Nicotiana tabacum L.at perio... more Experimental kinetics has been obtained by extraction from leaves of Nicotiana tabacum L.at periodical conditions in a stirred vessel. The influence of the liquid-solid ratio and the kind of the solvent have been determined. A four parameters model for calculating the values of Deff has been found using non-linear regression of the experimental results. The diffusion model have been solved using variable Deff. There is a very good coincidence between the numerical and experimental data.

Carbon Dioxide Capture by Adsorption ( Review )

The present paper reviews the different types of adsorbents that could be used for CO2 capture fr... more The present paper reviews the different types of adsorbents that could be used for CO2 capture from flue gases. They include carbon-based adsorbents, zeolites, molecular sieves, metal-organic frameworks, hydrotalcite-like compounds and advanced adsorbents. Their possibilities are described and confronted. In particular, it has been demonstrated that classical adsorbent materials need further functionalization or impregnation with different nitrogen-containing species in order to become suitable for CO2 capture. The different methods for CO2 capture by adsorption cyclic processes such as Pressure Swing Adsorption (PSA), Vacuum Swing Adsorption (PSA), Thermal Swing Adsorption (TSA), Electric Swing Adsorption (ESA) as well as the combination of TSA and chemical reaction, known as Thermal Swing Sorption-Enhanced Reaction (TSSER), are also mentioned in the cited literature.

Computation Programming of McCabe-Thiele and Ponchon-Savarit Methods for SHORT-CUT Distillation Design

International Journal of Science, Technology and Society

A New Procedure for Porous Material Characterization

International Journal of Science, Technology and Society

A new procedure for quantitative characterization of different types of solid materials is propos... more A new procedure for quantitative characterization of different types of solid materials is proposed. The technique is based on the Scanning Electron Microscopy (SEM) analysis results of porous materials and their processing by the software ImageJ. Several types of porous adsorbents AX21, AC35, GAC250, ACENO and IRH3 activated carbons were investigated. Based on SEM analysis, different characteristics of the samples such as porosity, pore size distribution, bed particles porosity can be obtained. In this study, the particle size, the average macropore size and pore size distributions (PSD) of samples were determined with a new procedure for SEM analysis treatment using ImageJ software. Three distribution functions (Gamma, Weibull and Lognormal) were selected to describe the experimental results. The Lognormal distribution fitted more accurately the experimental data.