Detailed Kinetic Modelling of the Oxidation and Combustion of Large Hydrocarbons Using an Automatic Generation of Mechanisms

A mechanism generator code to automatically generate mechanisms for the oxidation and combustion of large hydrocarbons has been successfully modified in this work. The modification was through: (1) improvement of the existing rules such as cyclic-ether reactions and aldehyde reactions, (2) inclusion of some additional rules to the code, such as ketone reactions, hydroperoxy cyclic-ether formations and additional reactions of alkenes, (3) inclusion of small oxygenates, produced by the code but not included in the handwritten C1-C4 sub-mechanism yet, to the handwritten C1-C4 sub-mechanism. In order to evaluate mechanisms generated by the code simulation of observed results in different experimental environments has been carried out. The simulation of auto-ignition of n-pentane in a rapid-compression machine shows good agreement with experimental results. Experimentally derived and numerically predicted ignition delays of n-heptane/air and n-decane/air mixtures in high-pressure shock tubes in a wide range of temperatures, pressures and equivalence ratios agree very well. Concentration profiles of the main products and intermediates of n-heptane, iso-octane and n-decane oxidation in jet-stirred reactors at a wide range of temperatures and equivalence ratios are generally well reproduced. Sensitivity and reaction flow analyses were performed for shock tube and jet-stirred reactor environments, respectively, in an attempt to identify the most important reactions under the relevant conditions of study. In addition, the ignition delay times of different normal alkanes was numerically studied

Modeling of Partial Hydrogenation of Polyunsaturated Fatty Acid Methyl Esters in a Trickle Bed Reactor

Partial hydrogenation of polyunsaturated fatty acid methyl esters in a trickle-bed reactor was modeled and simulated in this study with the objectives being to investigate the performance of the reactor, to predict the effect of process parameters on the reactor performance, and to observe the radial heat transfer in the reactor. The reactor possessed the aspect ratio of 100 and was packed with spherical catalyst particles. A steady-state heterogeneous model was applied. The gas and liquid phases were modeled in two-dimensional axisymmetric model, which consist of mass balance for each phase, energy balance and momentum balance. The momentum balance was based on the Darcy equation for two fluid phases passing through porous media. Mixing in both fluid phases is also described by dispersion coefficients. The three-dimensional solid phase model considered diffusive transport in the catalyst pores and surface reactions. Methyl linoleate was considered as polyunsaturated fatty acid methyl ester representative, and cis-methyl oleate, trans-methyl oleate and methyl stearate were as the hydrogenated fatty acid methyl esters. The simulation results for the inlet temperature of 433 K and the reactor pressure of 611 kPa with the gas flowrate being 43 times higher than the liquid one shows that the process reached 78.22% methyl linoleate conversion. The concentrations of cis-methyl oleate, trans-methyl oleate and methyl stearate at the reactor outlet are 16.2 mol/m3, 17.4 mol/m3 dan 16.6 mol/m3, respectively. The total methyl oleate produced is about twice that of methyl stearate, and its selectivity is about 53%

Computational Fluid Dynamic Application in Scale-up of a Stirred-batch Reactor for Degumming Crude Palm Oil

The research aims to scale up a small-scale stirred batch reactor to a large-scale stirred batch reactor in order to degum crude palm oil for use as a raw material in biodiesel production. The scale-up is based on the similarity of fluid Reynolds numbers in the two differently sized reactors. To achieve this aim, computational fluid dynamic modeling and simulations of the two reactors were performed. A small-scale palm oil degumming process was carried out in a 250 cc autoclave reactor using a magnetic stirrer at 500 rpm. The simulation results of this small reactor yielded a fluid Reynolds number in the range of 5 to 3,482. The large-scale reactor proposed in this research is 1.25 m3 in volume and is equipped with two impellers: a pitched blade impeller and a Rushton turbine impeller. The pitched blade impeller is placed over the Rushton turbine impeller. They are rotated at 100 rpm. Under this setting and operation, the resulting fluid Reynolds number was in the range of 486 to 202,000. This result indicates that the large-scale reactor was able to reproduce the reaction performance obtained in the small-scale reactor

Simulation of Gas Leakage in a Gas Utilization System in Household Sector

The Indonesian Government is setting up a program of city gas utilization for household sector. People are not convinced of the safety of city gas utilization. One of the accidents people worry about is gas leaks in utilization systems, such as kitchen. Leaking gas is not dangerous when ones can prevent fire ignition. Therefore, information on potential fires caused by leaking gas and methods to prevent their occurrence is needed. This research was intended to obtain the information on fire prevention caused by leaking gas in a kitchen through simulation. The system simulated in the research is a rectangular room of 3 m × 2 m × 3 m. The models consider mass and momentum transfers. The simulation results show that when leaking gas is detected, the leak source must be closed. With the leak source being open, the safe limit is not reached, even if an exhaust fan is provided

Hydrodeoxygenation of Vegetable Oil in a Trickle Bed Reactor for Renewable Diesel Production

The hydrodeoxygenation of vegetable oil in a trickle bed reactor for renewable diesel production was observed in this research. Vegetable oil was represented by triolein. The NiMo/Al2O3 catalyst with a composition of 6.13% w/w Ni, 12.49% w/w Mo, and 81.33% w/w Al2O3 was used. The reactions took place in the temperature range of 272-327.5°C and pressures of 5 and 15 bar. A trickle bed reactor of 2.01 cm in diameter and 24 cm in bed length was able to convert triolein into renewable diesel. C18 hydrocarbons became the dominant reacting compounds at temperatures above 310°C and a pressure of 15 bar, which reached more than 50% w/w. At 5 bar pressure, fatty acids with stearic acid as the acid with the highest concentration were the dominant reacting component, reaching more than 60% w/w at temperatures above 280°C. This led to double bond saturation once the reactants were mixed

Kualitas dan Kuantitas Nanotube Karbon yang Dihasilkan dari Dekomposisi Katalitik Metana pada Berbagai Promotor Tekstural dengan Katalis Berbasis Ni-Cu

Nowadays, nanocarbon is one of the most developed nanotechnology products. Carbon nanotubes are the most conducted nanocarbons because of their unique properties and structures, hence they are applied as hydrogen storages, nanoscale transistors, flat panel display, supercapasitors, nanoprobes, sensors, and catalysts.However, there is a structure limitation of carbon nanotubes for every application. Carbon nanotubes that ere fit for hydrogen storages, has single-walled, small diameter, long, and uniform. Quality of carbon nanotubes is not only influenced by the reaction temperatures of catalytic decomposition of methane, but also by the catalyst particle size which is influenced by catalyst preparation method.This research is to observe the quality and quantity of carbon nanotubes produced from catalytic decomposition of methane at various textural promoters in the Ni-Cu-based catalysts. The textural promoters (SiO2 , MgO, Al2O3) were added to the Ni-Cubased catalysts by impregnation method. Furthermore, the catalysts were packed to a reactor which is online with gas chromatography. The temperature inside the reactor is 700oC. The results analyzed are the catalyst characterization, methane conversion, carbon and hydrogen yields, and carbon characterization. Activity test shows that the Ni-Cu-SiO2 catalyst is the most active one with the average CH4 conversion of 93.30. SEM characterization shows that the Ni-Cu-Al2O3 catalyst is of producing carbon with smaller diameter (100-250 nm). This results is consistent with the XRD tests performed to determine the size of catalyst particles, where the catalyst with alumina as the textural promoter has the smallest diameter. Keywords: Carbon nanotube, impregnation, textural promoter, catalytic decomposition of methan

Modelling and Simulation of Acid Extraction of Lanthanum from Indonesian Low Grade Bauxite using Fixed-Bed Extractor

Demand on lanthanides is growing rapidly due to significant growth of the utilization of advanced materials for industries. Efficient and large scale extraction process of lanthanide from their sources is studied. In this sense, extraction of lanthanum from Indonesian low grade bauxite using a fixed-bed cylindrical extractor with dimension of 30 × 3 cm was modelled and simulated. This simulation model would provide the optimum conditions, extraction time, and cost of extraction, useful for industrial application. A mathematical modelling and simulation was also used to investigate the effects of several parameters, such as particle size, fluid velocity, and acid concentration, on extraction yield of lanthanum. The simulation suggested that the maximum amount of lanthanum sulfate extracted from the low grade bauxite was as high as 6.6 mg after an extraction time of 300 min. The extraction yield can be increased when particle size was decreased, sulfuric acid flow rate was decreased, and concentration of sulfuric acid was increased

Effect of Anode Depth in Synthesis of Biodiesel using the Anodic Plasma Electrolysis Method

Plasma electrolysis is a process of electrolysis that uses a DC current to excite electrons in the electrolyzed solution. The method is very prolific in producing hydroxyl radical (OH•), which is then used to react with methanol and form a methoxyl radical (CH3O•). Methoxyl radical is used to break the bond of triglycerides to form methyl ester (biodiesel) and glycerol. The purpose of this study is to obtain a good quality and quantity of biodiesel by examining the effect of anode depth with a constant contact area where the anode is the spot of plasma formed. The solution used contains Refined, Bleached, and Deodorized Palm Oil and methanol with a molar ratio of 1:24 and a concentration of KOH 1%-wt. The variations of anode depth are 0.5 cm, 1.5 cm, and 3.5 cm below the surface of the solution, with 5 mm as the constant contact area. The results of this research show an improvement in efficiency, as indicated by yield, and the energy consumption of biodiesel synthesis with increasing depth of the anode. The maximum yield was reached at an anode depth of 3.5 cm, which produced 96.09% as a biodiesel yield with 0.039%-vol water content, 0.138 as the acid number, and a specific energy requirement of 0.909 kJ/ml

Computational Study of the Time-dependent Flow Field of a Water-Molasses Mixture Inside a Stirred Vessel

Detailed information on the flow field in the operation of a mixing unit is necessary for the optimal design of the reactor. The flow field characteristic is an essential factor in obtaining an optimal stirred vessel design. The efficiency of the stirred vessel system depends on, for example, the stirred vessel geometry, the flow induced by the impeller, the working fluid properties and the operating condition. The aim of this study is to exhibit the time-dependent flow field of the mixing process inside a stirred vessel for different propeller rotational speeds using computational fluid dynamics methods. The working fluid in question is molasses and water, which is a miscible liquid. The stirred vessel is a conical-bottomed cylindrical vessel (D = 0.28 m and H = 0.395 m) equipped with a three-blade propeller (d = 0.036 m). The transient calculation was conducted using ANSYS Fluent version 18.2. The Mixture multiphase flow model coupled with the Reynolds-averaged Navier-Stokes Standard k-? (SKE) turbulence model was applied to capture the information on the time-dependent flow fields at various propeller rotational speeds inside the stirred vessel. The flow generated by the propeller was compared at 1000 rpm, 1300 rpm and 1500 rpm. The Multiple Reference Frame method was used to solve the moving domain and stationary domain multiple frames case. The results revealed the local velocity, flow pattern, molasses volume fraction value, density gradient distribution, power number and flow number. The profile of all the variables determines the optimal operating conditions for the degree of mixing required

Modeling of Coal Spontaneous Fire in A Large-Scale Stockpile

The increasing need for energy consumption has resulted in the use of energy sources in coal continuing to increase. The transportation and distribution activities of coal also cause the pile to be exposed to heat when it is in a pile. Due to the kinetic characteristics of low-rank coal, the pile is very susceptible to spontaneous fire processes. Of course, this spontaneous fire phenomenon harms the safety and economic aspects of the coal pile. This study aims to model finite elements using Multiphysics simulation to determine the effect of the relative humidity of the pile on the temperature distribution of large-scale coal piles. Thus, handling methods and things that must be considered in storing and transporting coal piles can be formulated. Thermal phenomena modelling in coal piles is modeled using COMSOL Multiphysics software. The simulation is carried out by varying relative humidity of the environmental conditions (ambient). The simulation results show that this parameter can change the level of vulnerability of the pile to burn at an earlier time