Production of Biodiesel from a Novel Combination of Raphia Africana Kernel Oil and Turtle Shell (Centrochelys Sulcata) Heterogenous Catalyst

This work investigated the viability of a non-edible oil obtained from raphia africana in the production of biodiesel using a novel heterogeneous catalyst derived from turtle shells (Centrochelys sulcata). The study also proposed the use of acetone as co-solvent to enhance the solubility of the reacting mixtures. The turtle shells were calcined at 900oC for 3hr, impregnated in KOH to improve its activity and then supported with activated carbon produced from cassava peels to increase its surface area. The influences of KOH concentration, catalyst loading, catalyst/carbon mix ratio and concentration of acetone/methanol on the yield of biodiesel were investigated. The results obtained revealed that maximum biodiesel yield of 93% was obtained from the bio-oil at KOH concentration of 30% (w/w), catalyst loading of 6.5%, solvent/methanol ratio of 0.4 and catalyst/carbon weight ratio of 1.25. The activated carbon supported turtle shell catalyst has been found to possess very high catalytic activity converting bio-oil with high saturated fatty acid content to biodiesel with excellent fuel properties having low saturated fatty acids profile. Doi: 10.28991/HEF-2021-02-03-07 Full Text: PDF

High-temperature effect of a gas jet of reacting components on an inclined plate

The purpose of the research was to experimentally and computationally study the distribution of pressures and heat fluxes when near-design jets of high-temperature reacting mixtures on the oxygen-kerosene, oxygen-methane, oxygen-ethanol components act on an inclined plate in the near field of the jet within the distance equal to nozzle exit diameter for pressure ratio The paper introduces the results of these studies. They were carried out with jets flowing with total temperatures of into ambient environment with normal pressure and temperature. The level of heat fluxes created by the jet on the plate was in range within Calculations in the SolidWorks Flow Simulation environment for the effect of a high-temperature flow for a perfect gas with parameters corresponding to the chemical composition in a model combustion chamber showed good agreement with experimental data.

High-temperature effect of a gas jet of reactants on the front plate

The paper introduces the results of measuring and predicting the heat and force effect of jets of high-temperature reacting mixtures on the oxygen-methane, oxygen-alcohol components when acting on the front plate in the near field of the jet. A high-temperature supersonic gas jet flows out of a model chamber with a Laval nozzle into a medium with atmospheric pressure at a degree of off-design ratio of about unity. In the chamber, ignition and stable combustion of a mixture of selected substances occur, the ratio of these substances providing a stagnation temperature in the range of 1900 ... 3400 K. The pressure distribution function on the front plate obtained in the experiment is used. The proposed model of the high-temperature flow effect on the frontal surface can be used to test software systems and determine the levels of thermal effect during sample tests.

On the similarities and differences between the products of oxidation of hydrocarbons under simulated atmospheric conditions and cool-flames

Whereas the kinetics of oxidation of limonene has been extensively studied and mechanisms for its oxidation by OH and/or ozone have been proposed, more studies are required for better understanding its oxidation pathways. The oxidation of limonene-oxygen-nitrogen mixtures was studied using a jet-stirred reactor at elevated temperature and atmospheric pressure. Samples of the reacting mixtures were collected and analyzed by high resolution mass spectrometry (Orbitrap) after direct injection or after separation by reverse-phase ultra-high-pressure liquid chromatography and soft ionization by (+/−) HESI and (+/−) APCI. The results indicate that among the 1138 detected products, many oxygenates found in earlier studies of limonene oxidation by OH and/or ozone are also produced under the present conditions. Other highly oxygenated products and oligomers were also detected in the present work. The results are discussed in terms of reaction pathways involving the initial formation of peroxy radicals, isomerization reactions yielding keto-hydroperoxides and other oxygenated intermediates and products up to C25H32O17. The possible occurrence of the Waddington mechanism and of the Korcek mechanism are also discussed. The present work demonstrates similarities between the oxidation products and oxidation pathways of limonene under simulated atmospheric conditions and in those encountered during the self-ignition of hydrocarbons at low temperatures, which should stimulate future interactions between communities of atmospheric chemistry and combustion chemistry to improve current chemical models.

SIMULATION OF HOMOGENEOUS NUCLEATION OF BORIC ANHYDRIDE VAPOR IN AXISYMMETRIC NOZZLE

A model of unsteady homogeneous nucleation of boron oxide vapors in chemically reacting mixtures is proposed. The nucleation of condensation nuclei in the model is considered as a bimolecular reaction of boron oxide molecules capture by clusters of boron oxide.

Charged Species Concentration in Combusting Mixtures Using Equilibrium Chemistry

Ionization in flames is of interest in the design and development of modern combustion devices. The identity and concentration of various charged species in reacting mixtures can play an important role in the diagnostics and control of such devices. Simplified chemistry computations that provide good estimates of ionic species in complex flow-fields can be used to model turbulent reacting flows in various combustion devices, greatly reducing the required computational resources for design and development studies. A critical assessment of the use of the equilibrium chemistry method to compute charged species concentration in combusting mixtures under various temperatures, pressures, and thermal disequilibrium conditions is presented. The use of equilibrium chemistry to compute charged species concentrations in propane-air mixtures performed by Calcote and King has been extended. A more accurate computational methodology that includes the effect of negative ions, chemi-ions (H3O+ and CHO+), and thermal nonequilibrium was investigated to evaluate the suitability of equilibrium computations for estimating charged species concentrations in reacting mixtures. The results show that equilibrium computations which include the effects of H3O+ and elevated electron temperatures can indeed explain the levels of ion concentrations observed in laboratory flame experiments under lean and near-stoichiometric conditions. Furthermore, under engine-like conditions at higher temperatures and pressures, equilibrium computations can be used to obtain useful estimates of charged species concentrations in modern combustion devices.