Mathematical Modeling of Biodiesel Production under Intense Agitation

2016 ◽  
Vol 14 (1) ◽  
pp. 445-451
Author(s):  
Aliakbar Roosta ◽  
Jafar Javanmardi ◽  
Elham Sadat Behineh
Keyword(s):  
Mass Transfer ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Rapeseed Oil ◽  
Catalyst Concentration ◽  
Biodiesel Production ◽  
Transfer Coefficients ◽  
Increasing Temperature ◽  
Intense Agitation

AbstractIn this study, a new approach is proposed to investigate the kinetics of sunflower oil and rapeseed oil transesterification in the presence of potassium hydroxide. Transesterification is a heterogeneous process which affected by a number of parameters, that are not readily available in the literature, such as mass transfer coefficients, partition coefficients, and specific surface area of the dispersed phase. However, under intense agitation condition, mass transfer restrictions may be neglected, and the two phases are supposed to remain in thermodynamic equilibrium, during the process. Therefore, a model was developed independent of the mass transfer coefficient and specific surface area, which is reliable for the intense agitation condition. According to the results, the model is valid at least for mixing rates over 500 rpm. The results of the model were used to study the effects of temperature, methanol-to-oil ratio, and catalyst concentration on the biodiesel conversion. Biodiesel production rate increases with increasing temperature, although rapeseed oil transesterification is more temperature dependent. The results show that the maximum amount of catalyst concentration is less than 1% (by weight); however, the optimum value depends on the operating temperature. The optimum value of the methanol-to-oil-ratio decreases with increasing temperature. Thus, at higher temperatures, less amount of methanol and catalyst are required, which leads to easier purification of biodiesel.

Direct molecular hydrogen sulphide scrubbing with hollow fibre membranes

2001 ◽  
Vol 44 (9) ◽  
pp. 135-142 ◽  
Author(s):  
N. Boucil ◽  
B. Jefferson ◽  
S.A. Parsons ◽  
S.J. Judd ◽  
R.M. Stuetz
Keyword(s):  
Mass Transfer ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Flow Rate ◽  
Hydrogen Sulphide ◽  
Gas Flow ◽  
Hollow Fibre ◽  
The Other ◽  
Gas Flow Rate

The emission of hydrogen sulphide is a major problem associated with anaerobic treatment of sulphate and sulphite containing wastewaters. Conventional absorbing processes, such as packed towers, spray towers or bubble columns, are all constrained by factors such as flooding and foaming. Membrane systems, on the other hand, enable independent control of the liquid and gas flow rate and a step change order of magnitude increase in the specific surface area of the contact process. The membrane acts as a gas absorber with a design similar to a shell and tube heat exchanger. On the other hand, they are limited by facets of the membrane such as its resistance to mass transfer and permselectivity, as well as its cost. The work presented in this paper refers to an absorption process based on a non-wetted hollow fibre membrane for the scrubbing of hydrogen sulphide from air, with water as the contact solvent. Results presented describe the performance of the unit in terms of overall transfer and outlet liquid concentration as a function of circulation regime, gas flow rate, liquid flow rate and specific surface area. In particular, results are presented using traditional plots of Sherwood number (Sh) against Graetz (Gr) number for the liquid flowing in the lumens, such that experimental and available empirical descriptions of the process performance are directly compared. Results suggest that, as expected, very efficient mass transfer is obtained. However, the mass transfer was found to reach a maximum value against Gr, contrary to available empirical models.

REPRESENTATION OF THE SPECIFIC SURFACE AREA OF A POROUS MEDIUM BY STATISTICAL CONTINUOUS MONOMIAL FUNCTIONS

2021 ◽  
Author(s):  
В.Г. ЖУКОВ ◽  
В.М. ЧЕСНОКОВ ◽  
Н.Д. ЛУКИН
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Food Systems ◽  
Transfer Processes ◽  
Pore Length ◽  
Mass Transfer Processes ◽  
Size Groups

Удельная поверхность пористых сред является важным геометрическим параметром в расчетах процессов пищевых систем и оборудования для их переработки. Расчетные формулы процессов тепло- и массообмена в настоящее время содержат осредненные значения геометрических параметров, получаемые в эксперименте. Использование формул удельной поверхности по осредненным характеристикам пористой среды существенно ограничивает точность и надежность расчетов. Получены непрерывные одночленные по всему диапазону размеров сообщающихся пор расчетные формулы удельной поверхности, основанные на функции распределения плотности вероятности размеров сообщающихся пор разных модельных конфигураций в полиразмерной дисперсной (несцепленной) и связной (сцепленной) пористых средах для двух видов исходных формул удельной поверхности, различных видов модельных поперечных сечений и длины пор. Проведен их сравнительный анализ. Установлено, что на расчет удельной поверхности влияет моделируемая длина пор. Вид поперечного сечения не влияет на расчет удельной поверхности. Полученные формулы позволяют вычислять удельную поверхность для ансамбля отдельных размерных групп пор и в целом для всей совокупности их размеров. Приведен пример расчета по полученным формулам. The specific surface area of porous media is an important parameter in the calculations of the processes of food systems and equipment. The calculated formulas of the heat and mass transfer processes currently contain the averaged values of the geometric parameters obtained in the experiment. The use of formulas the specific surface area based on the averaged characteristics of a porous medium significantly limits the accuracy and reliability of calculations. Continuous monomial calculated formulas for the specific surface and based on the function of the probability density of the size distribution open pores ware obtained. Their comparative analysis is carried out. It was found that the transverse shape is not reflected in the formulas for the specific surface area, but the simulated pore length does. The specific surface area formulas allow calculating the specific surface area for an ensemble of separate size groups of pores and, in general, for the entire set of their sizes. An example of calculation by the obtained formulas is given.

scholarly journals Adsorption of carbon dioxide on MIL53(Al), CuBTC and K- NaX zeolite

2020 ◽  
Vol 4 (3) ◽  
pp. 30-42
Author(s):  
Fehime Cakicioglu-Ozkan
Keyword(s):  
Carbon Dioxide ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Co2 Adsorption ◽  
Ultrasonic Method ◽  
Metal Organic Frameworks ◽  
Isosteric Heat ◽  
Metal Organic ◽  
Increasing Temperature

CO2 adsorption on K exchanged NaX zeolites, and metal organic frameworks (MOFs), namely Cu-BTC and MIL53 (Al) was studied at 5 °C and 25 °C.  Exchange via ultrasonic and traditional methods, was conducted at 50 °C and 70 °C. The maximum replacement of Na+ ion with K+ ion in the extra framework of zeolite was increased from 76% to 83% with increasing temperature from 50 °C to 70 °C in the ultrasonic method which is more effective than traditional one. Compared with the zeolites, the MOF adsorbents used in this work have higher Langmuir specific surface area values namely 1278, 1473 and about 1000 m2/g for MIL 53, Cu-BTC and zeolite adsorbents respectively. The resulting CO2 isotherms can be well represented by the Toth equation. Comparison of the isosteric heat of adsorption at zero loading shows that CO2 was adsorbed more weakly on MOFs than zeolites.

scholarly journals Adsorption of phosphate ions from an aqueous solution by calcined nickel-cobalt binary hydroxide

2016 ◽  
Vol 75 (1) ◽  
pp. 94-105 ◽  
Author(s):  
Fumihiko Ogata ◽  
Erimi Ueta ◽  
Megumu Toda ◽  
Masashi Otani ◽  
Naohito Kawasaki
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Correlation Coefficients ◽  
Hydroxyl Groups ◽  
Order Model ◽  
Molar Ratios ◽  
Phosphate Ions ◽  
Increasing Temperature ◽  
Adsorption Desorption

Different molar ratios of a Ni/Co binary hydroxide (NiCo82, NiCo91, and Ni100) were prepared and calcined at 270 °C (NiCo82-270, NiCo91-270, and Ni100-270). The properties of the adsorbents and the amount of adsorbed phosphate ions were evaluated. The adsorbents calcined at 270 °C had a nickel oxide structure. The amount of adsorbed phosphate ions, the amount of hydroxyl groups, and the specific surface area of the calcined adsorbents at 270 °C were greater than those of the uncalcined adsorbents. The amount of adsorbed phosphate ions was related to the amount of hydroxyl groups and the specific surface area; the correlation coefficients were 0.966 and 0.953, respectively. The adsorption isotherm data for NiCo91 and NiCo91-270 were fit to both the Freundlich and Langmuir equations. The amount of adsorbed phosphate ions increased with increasing temperature. The experimental data fit the pseudo-second-order model better than the pseudo-first-order model. A neutral pH was optimal for phosphate ion adsorption. In addition, the phosphate ions that were adsorbed onto NiCo91-270 could be recovered using sodium hydroxide, and the adsorbent was useful for the repetitive adsorption/desorption of phosphate ions. Collectively, these results suggest that NiCo91-270 is prospectively useful for the adsorption of phosphate ions from aqueous solutions.

scholarly journals Improvement of Biohydrogen and Usable Chemical Products from Glycerol by Co-Culture of Enterobacter spH1 and Citrobacter freundii H3 Using Different Supports as Surface Immobilization

Fermentation ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 154
Author(s):  
Biniam T. Maru ◽  
Francisco Lopez ◽  
Francesc Medina ◽  
Magda Constantí
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
H2 Production ◽  
Dark Fermentation ◽  
Biodiesel Production ◽  
Citrobacter Freundii ◽  
Surface Immobilization ◽  
Iron Species ◽  
Glycerol Conversion

Glycerol is a by-product of biodiesel production in a yield of about 10% (w/w). The present study aims to improve the dark fermentation of glycerol by surface immobilization of microorganisms on supports. Four different supports were used—maghemite (Fe2O3), activated carbon (AC), silica gel (SiO2), and alumina (γ-Al2O3)—on which a newly isolated co-culture of Enterobacter spH1 and Citrobacter freundii, H3, was immobilized. The effect of iron species on dark fermentation was also studied by impregnation on AC and SiO2. The fermentative metabolites were mainly ethanol, 1,3-propanediol, lactate, H2 and CO2. The production rate (Rmax,i) and product yield (Yi) were elucidated by modeling using the Gompertz equation for the batch dark fermentation kinetics (maximum product formation (Pmax,i): (i) For each of the supports, H2 production (mmol/L) and yield (mol H2/mol glycerol consumed) increased in the following order: FC < γ-Al2O3 < Fe2O3 < SiO2 < Fe/SiO2 < AC < Fe/AC. (ii) Ethanol production (mmol/L) increased in the following order: FC < Fe2O3 < γ-Al2O3 < SiO2 < Fe/SiO2 < Fe/AC < AC, and yield (mol EtOH/mol glycerol consumed) increased in the following order: FC < Fe2O3 < Fe/AC < Fe/SiO2 < SiO2 < AC < γ-Al2O3. (iii) 1,3-propanediol production (mmol/L) and yield (mol 1,3PDO/mol glycerol consumed) increased in the following order: γ-Al2O3 < SiO2 < Fe/SiO2 < AC < Fe2O3 < Fe/AC < FC. (iv) Lactate production(mmol/L) and yield (mol Lactate/mol glycerol consumed) increased in the following order: γ-Al2O3 < SiO2 < AC < Fe/SiO2 < Fe/AC < Fe2O3 < FC. The study shows that in all cases, glycerol conversion was higher when the support assisted culture was used. It is noted that glycerol conversion and H2 production were dependent on the specific surface area of the support. H2 production clearly increased with the Fe2O3, Al2O3, SiO2 and AC supports. H2 production on the iron-impregnated AC and SiO2 supports was higher than on the corresponding bare supports. These results indicate that the support enhances the productivity of H2, perhaps because of specific surface area attachment, biofilm formation of the microorganisms and activation of the hydrogenase enzyme by iron species.

scholarly journals Metal Foams as Novel Catalyst Support in Environmental Processes

Catalysts ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 587 ◽  
Author(s):  
Anna Gancarczyk ◽  
Katarzyna Sindera ◽  
Marzena Iwaniszyn ◽  
Marcin Piątek ◽  
Wojciech Macek ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Mechanical Stability ◽  
Packed Bed ◽  
Metal Foams ◽  
High Porosity ◽  
Slow Kinetics

Metal foams are considered as promising catalyst carriers due to their high porosity, large specific surface area, and satisfactory thermal and mechanical stability. The study presents heat transfer and pressure drop experiments performed for seven foams of different pore densities made from diverse metals. Mass transfer characteristics are derived using the Chilton–Colburn analogy. It was found that the foams display much more intense heat/mass transfer than a monolith, comparable to packed bed. Next, the foams’ efficiencies have been compared, using 1D reactor modeling, in catalytic reactions displaying either slower (selective catalytic reduction of NOx) or faster kinetics (catalytic methane combustion). For the slow kinetics, the influence of carrier specific surface area at which catalyst can be deposited (i.e., catalyst amount) was decisive to achieve high process conversion and short reactor. For this case, monolith appears as the best choice assuming it’s the lowest pressure drop. For the fast reaction, the mass transfer becomes the limiting parameter, thus solid foams are the best solution.

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