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Bagasse as solid waste in sugarcane industry can be utilized as one of the potential raw materials in the bioprocess industry. This research aims to investigate the conversion of bagasse to bioethanol using simultaneous saccharification and fermentation in an airlift bioreactor. Neurospora intermedia was used as a biological agent that carried out the saccharification and fermentation of sugarcane bagasse simultaneously for bioethanol production. Cell morphology of N. intermedia in the form of pellet was required to provide free movement in the axial flow of airlift bioreactor. The medium pH strongly affects the morphological shape of N. intermedia. Therefore, the formation of good pellets of inoculum was observed under acidic conditions, i.e. pH 3.0 – 3.5. The effect of the initial concentration of nutrient on the inoculum growth was also investigated. Inoculums cultured in potato dextrose broth (PDB) medium with a half the strength of the common nutrient concentration of PDB qualitatively indicated good growth in terms of the size and density of cells. The inoculums with good morphological form were fed into the airlift bioreactor, which already contained a liquid medium with initial pH of 3.5 and also contained pre-treated bagasse. In experiments using the airlift bioreactor, the pre-treated bagasse was added to various nutrient concentrations of the PDB infusion medium. The highest bioethanol production from bagasse was monitored in the medium culture of half strength PDB infusion. The yield of bioethanol obtained from total sugarcane bagasse and PDB in an air lift bioreactor achieved approximately 40%, which has an infusion medium with a half-strength PDB and initial pH of 3.0. ©2020. CBIORE-IJRED. All rights reserved

The energy shortage and environmental pollution crises have prompted the investigation of hydrogen based cleaner energy system. Therefore, hydrogen has been considered as a promising energy carrier due to its sustainability and environmentally friendly. This research considered the separation of hydrogen from mixed gas (H2 and N2) by using Pd-based membrane. In order to produce extra high purity of hydrogen, the separation of hydrogen using Pd-based membrane under steady state operation suffers from long time lag and membrane deactivation. These two technical problems leading to the decrease of hydrogen permeability were intensively addressed in this work. The separation of hydrogen was conducted by using a Pd/α-Al2O3 membrane with aim to improve the performance of separation, indicated by time lag and hydrogen recovery. The novel method of the dynamic membrane operation was applied by performing a composition modulation of the feed gas flow rate. The steady state operation was used as a base case for comparison to dynamic operation. All experiments were carried out at 325 °C, atmospheric pressure, and H2/N2 ratio of 1:1, while varying the switching time and concentration amplitude for dynamic operation. The Pd based membrane was prepared, characterized, and it showed no pin hole could be found. The permeability constants for unsteady state condition resulted in higher when compared to steady state condition. The experiment results showed that the recovery of hydrogen under steady state condition was 21%. On the other hands, the recovery of hydrogen under invoked unsteady state operation was significantly improved three times higher than that of the steady state operation. The recovery of hydrogen increased 8–13% when the feed gas amplitude decreased from 1.5 mL/s to 0.5 mL/s. Operations at 300 s switching time and 0.5 mL/s flowrate amplitude reached the hydrogen recovery up to 63%.

Dry reforming of methane was studied over high-ratio zirconia in ceria-zirconia-mixed oxide-supported Ni catalysts. The catalyst was synthesized using co-precipitation and impregnation methods. The effects of the catalyst support and Ni composition on the physicochemical characteristics and performance of the catalysts were investigated. Characterization of the physicochemical properties was conducted using X-ray diffraction (XRD), N

Platina play a crucial role in catalytic converter device as one of catalyst that convert toxic gases in the exhaust gas emission to less toxic gas pollutant. The performance of this device can be significantly elevated by implementing platina nanoparticles (Pt NPs) because catalytic performance can be increased by decreasing its particles size. However, nanoparticles are not stable and tend to agglomerate, thus prohibit formation of nano particles. In this context, utilization of cellulose nano crystals (CNCs) in fabrication of Pt NPs are attractive due to their ability to encourage nucleation and prevent agglomeration of nanoparticles. In this study, Pt NPs was prepared by reduction of H2PtCl6 solution at various temperature (25, 33 and 40 °C) with the presence of CNCs. Based on visual observation, darker precipitate was observed by increasing temperature. Further characterization using UV-Vis spectroscopy showed that about 90% of Pt4+ in solution were successfully convert to dark particles at 40 °C. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) revealed that the dark particles in sample is Pt NPs with particles size 16.5 ± 3.2 nm.

Palm oil has fulfilled most of the oil needs in the food sector in the world. However, palm oil is indicated to contain small amounts of compounds that are harmful to humans, especially to infants. These toxic contaminants are 3-monochloropropanediol (3-MCPD) esters and glycidyl esters (GE), which are formed during the deodorization of palm oil at high temperatures. This study aims to reduce the 3-MCPD ester concentration in refined, bleached, and deodorized palm oil (RBDPO) through adsorption using activated carbon. The activated carbons were treated with heat and acid-washing using HCl at various concentrations and were characterized. The treatment altered the physicochemical characteristics of the activated carbon (surface area, pore volume, pHPZC, and CEC), resulting in the enhancement of its adsorption characteristics (adsorption capacity). The activated carbon treated with 2 N HCl (AC 2 N) was chosen as the proper adsorbent, due to better surface area, better pore volume, highest CEC value, and better positive charge in RBDPO. The 3-MCPD and GE adsorption capacity of AC 2 N was 1.48 mg g−1 and 29.68 mg g−1, respectively. The adsorption ability of pretreated activated carbon towards 3-MCPD esters was examined in a batch system at various adsorption temperatures. The 3-MCPD ester concentration in RBDPO was successfully reduced by up to 80% at 35 °C using the activated carbon treated with 2 N HCl solution. On the other hand, the activated carbon was able to reduce the other contaminant of GE in RBDPO up to 97% from the initial concentration of GE.

The Natuna gas field is one of the largest natural gas reserves in Indonesia with estimated natural gas reserves of 222 TCF. However, until now, the use of Natuna gas is still hampered because of the very high CO2 content reaching 71%, while the methane content is around 28%. The dry reforming of methane (DRM) process is one of the potential ways to be applied for solving these problems to convert CH4 and CO2 to synthesis gas containing CO and H2 as a raw material that can be applied to manufacture as intermediate products or end products in the petrochemical industry such as acetic acid. The simulation of the acetic acid production was conducted by using ASPEN HYSYS v.10, considering mass and heat balances. The PengRobinson was applied for dry reforming of methane process. In order to produce 496.8 kmol/h of the acetic acid, the 500 kmol/h for each CH4 and CO2 were used as feed gas. The total energy required is 4.7 MMBtu per ton of acetic acid. The acetic acid has a purity of 99.4% with a concentration of 500 ppm methanol, and moisture content of 5,700 ppm.

The performance of a reverse flow reactor (RFR) is strongly influenced by the switching time used to alternate the flow direction. This research aimed to study the effect of the switching time on reactor dynamics including the heat propagation along the bed and reaction rate in the oxidation methane for low concentration using catalytic reverse flow reactor. The experimental results show that the reverse flow operating mode can influence heat propagation along the reactor and reaction conversion. Based on the three switching times was tested, the temperature dynamics formed were in the sliding regime. The effect of switching time on RFR on conversion is very significant. When compared to steady operation, RFR operation provides the highest conversion at smaller switching times. At large switching times, the effect of reversal of flow direction becomes less dominant and reactor behavior approaches steady state.

Miscanthus is a bioenergy crop that is very easy to cultivate. It has high volatile content with an average energy value of about 18.8 MJ/kg on a dry basis. With the benefits mentioned above, Miscanthus is potential as a fuel for the suspended furnace. Therefore, the furnace design for the Miscanthus particle needs to be developed immediately. A relatively fast and low-cost technique to develop a burner furnace design is the modeling. This study aims to determine the intrinsic parameter values of dry Miscanthus particles needed in cold particle dynamic modeling. The various reasonable experimental techniques were used to obtain these parameter’s values. Then, a series of simulations and experiments of dry chopped Miscanthus dynamic in a special burner was conducted to assess the conformity of these values. The intrinsic parameters values of dry chopped Miscanthus obtained are as follows; shape factor (fs) 0.52, true particle density (ρp) 245 kg m-3, minimum, maximum, and mean particle diameters (dp) 106, 9520, and 1384 µm respectively, and spread parameter (n) 1.22. Qualitatively, the particle dynamic simulation results, using RSM and k-e models, showed similar particle pathlines to the experiment results, in terms of the frequency and intersection of the helical structure formed in the burner cylinder. It indicates that the intrinsic parameter values obtained in this study are reliable results and can be used for further simulation works. In addition, particle dynamics experiments and simulations also revealed that the particle pathline in the burner cylinder tend to move near the cylinder wall in a helical pattern; a single helix pattern in a single tangential inlet burner and a double helix pattern in a double tangential inlets burner. Regardless of the effect of the tangential inlet number, the helical pattern in the burner cylinder was also influenced by the initial swirl number (ISN) of the flow. The lower the ISN, the lower the helical frequency formed and vice versa. This study also proved that at low to moderate swirl intensities, the k-e turbulent model can be relied upon to model particle dynamics in a cyclone burner.

This study deals with bioethanol production from vetiver leaves contaminated with heavy metal ions, Al(iii) and Ni(ii). The effects of these ions on the growth of Neurospora intermedia and the prod...

Cellulose nanocrystals (CNCs) are one of the emerging nanomaterials that have several interesting and unique properties such as high mechanical strength (Young modulus of 100–140 GPa), low density (1.6 g cm−3), and large surface area (150–250 m2 g−1) that are advantageous in a myriad of applications. In this study, CNCs were successfully prepared from empty fruit bunch (EFB), an agricultural waste from palm oil, using a one-step extraction method using ammonium persulfate oxidation. EFB was directly reacted with ammonium persulfate (APS) at different concentrations (1.0; 1.5 and 2.0 M) at 60 °C for 15 h to undergo the oxidation. The oxidised EFB samples were characterised by dynamic light scattering (DLS), x-ray diffraction (XRD), transmission electron microscope (TEM), Fourier-transform infrared (FTIR), and thermogravimetric analysis (TGA). The FTIR result shows that lignin and hemicellulose in the EFB were successfully removed using one-step extraction method with minimum APS concentration of 1.5 M. The CNCs product has a crystallinity index of 64.1%, a crystallite size of 3.86 nm, and (0 0 2) plane lattice spacing of 3.95 Å. Based on the lattice spacing calculation of all samples, the crystalline structure of cellulose does not change during the oxidation process. The proposed one-step extraction method has been proven to produce the CNCs from EFB with a crystallinity index of 64.1%, a length of 275.9 ± 82.8 nm, and a diameter of 25 ± 5.3 nm.

Reactor mikro telah menempatkan diri pada posisi yang diminati dalam pengembangan teknologi reactor modern yang memiliki karakteristik pokok dalam hal percepatan laju perpindahan massa dan panas yang berlipat ganda. Dengan dimensi yang berskala mikron, distribusi aliran dari pipa induk menuju masing-masing kanal merupaka salah satu persoalan penting untuk menjamin keseragaman aliran di setiap kanal. Makalah ini mengkaji distribusi aliran dalam lima model reactor dan shift converter yang mengkonversi CO menjadi CO2 agar tidak meracuni katalis dalam sel bahan bakar. Selanjutnya pada model reactor dengan distribusi terbaik, karakteristik cold start up ditelaah lebih mendalam melalui teknik reaksi kimia tak tunak. Hasil studi menunjukkan bahwa start up pada shift converter dapat dilakukan dalam waktu yang sangat singkat yang menunjukkan bahwa secara praktis unit reactor mikro ini dapat diterapkan.Kata kunci : reactor mikro, pemodelan dan simulasi, shift converter, miniaturisasi

Over the past decade, the technology of enzyme immobilization has been developed because it is able to produce reusable immobilized enzymes to reduce production costs. This research aims to synthesize cellulose nanocrystals (CNC) from sugarcane bagasse. The CNC was then used as a matrix in immobilization of lipase to be applied in triglyceride lipolysis. Lipase was immobilized onto CNC through covalent bonding method at 25°C dan pH 7 with immobilization period variation of 0.5–4.5 hours. The immobilized lipase will be utilized to catalyze lipolysis reaction of triglyceride from palm oil, with lipolysis period 2–10 hours, reaction temperature of 25–60°C, and pH of 6.25–11.25. Lipase was successfully immobilized onto CNC so it can be utilized in lipolysis of palm oil with degree of hydrolysis about 10%. The optimum immobilization time and reaction time of lipolysis was 1.5 hours and 6–8 hours, respectively. Both free lipase and immobilized lipase had the optimum temperature at 40°C. In contrast to the optimum temperature, the optimum pH of the lipolysis reaction using free lipase is different from that of lipolysis using immobilized lipase. The optimum pH of lipolysis using free lipase is pH 7.25, while the optimum pH for reaction using immobilized lipase is shifted to pH 8.25.

This research focuses on extraction of cellulose nanocrystals (CNCs) from industrial denim waste using oxidation method in a batch reactor by varying pretreatment methods, ammonium persulfate (APS) concentrations, and reaction times. This oxidation method shows beneficial when compared to the conventional hydrolysis methods in term of less corrosive and shorter extraction time. Two-step method was developed instead of using one-step only to judge the beneficial of alkali pretreatment. The raw material of industrial denim waste was prepared in the form of powder with particle size range of 80–120 mesh. This raw material was characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Thermogravimetric analysis (TGA). The CNCs products were characterized using Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD) for confirming the particle size distribution, morphology, and crystallinity, respectively. The results showed that increasing the reaction time from 5 h to 15 h decreased the particle size of CNCs and increased the crystallinity of CNCs, while increasing the APS concentration from 1 to 1.5 M decreased the particle size of CNCs and the crystallinity of CNCs. The optimum operating conditions were obtained that the reaction time was 15 h at 60 °C and 1.5 M APS concentration, which produced the rod like morphology of CNCs with 76.14 ± 8.56 nm length, 18.10 ± 3.54 diameter and the crystallinity of 83 %. From the DLS and XRD characterizations, it was confirmed that the CNCs from denim waste could be produced through the oxidation method using APS.

This paper deals with reactor design, modeling, and simulation of a pilot-scale reverse flow operation used for catalytic oxidation of lean benzene-air mixtures. The reactor was designed for conducting lean benzene with adiabatic temperature rise less than 54°C. According to the rule of thumb, this kind of condition requires the reaction to be accomplished under reverse flow operation. In the reactor design, some criteria were calculated such as Mears, Weisz-Prater and Ergun’s criteria The reactor model was developed for 1D, pseudo-homogeneous, involving mass and energy balances. The fixed bed consisted of the inert section, placed at the outer part of the catalyst section. The results of the simulation indicated that the switching time, inlet concentration and heat extraction imposed an important influence on the performance of the reactor. Under the suitable operating conditions, the system can achieve a favorable running status, without reactor extinction, and can be operated auto-thermal, in fact, more thermal energy from the catalyst section was feasible to extract. The temperature profile remained smooth and continuous in the case of desired energy extracting from the heat exchanger.

CO oxidation in the catalytic converter hasn’t showed best performance particularly during cold start-up, since the catalyst is not active during this period. The purpose of this experiment was to develop the forced unsteady state operation procedure of CO oxidation using 0.05%-w Pt/γ-Al2O3 and space velocity of 0.406 mmol/s/gram. The catalytic converter was gradually ramped-up, while introducing the feed gas containing CO in the air. The feed gas was modulated following a square wave model with switching time variation at 3, 6, 15, and 30 s and various operation modes. To gain the intrinsic reaction rate, the external mass transfer criterion was determined. Ramping-up the temperature from 50 until 150°C increased the CO conversion with different profiles between steady state and dynamic flow rate. The dynamic system with modulated CO feed flow gave lower light-off temperature and higher average CO conversion than the steady state system which gave light off temperature 115°C and average CO conversion of 48.86%. The switching time of 3 s gave highest average CO conversion during ramping-up, which was 79.35%. Meanwhile the dynamic operation system with modulated feed flow gave higher lightoff temperature and lower average CO conversion than steady state system.

The simulation of dynamic reverse flow operation (RFO) with reactor side feeding for selectivity issue during exothermic reaction, while incorporating mass and energy balances both solid phase and gas phase, is presented in this paper with particular aim to investigate the product distribution. The reactor model consisted of mass balances on the level of elementary steps, which led to detailed dynamic influence of flow reversal effect on kinetics. The results showed the production rate of the desired product can be kept at high level, which may exceed the level of regular RFO and even of steady state operation (SSO). Even for the quasi-steady state regime, the reverse flow reactor with side feeding shows a different product distribution in comparison to SSO. The influence of shifting the feed positions to the reactor center is most pronounced. The reverse flow operation with reactor side feeding is a prime key for improved conversion and manipulation of product distribution.

Mesoporous Ce0.75Zr0.25O2 solid solution powders were successfully synthesized by a co-precipitation method. A combination of 10 wt% copper oxide, manganese oxide, and nickel oxide was added to the Ce0.75Zr0.25O2 support by impregnation method and calcined in the air with a flow rate of 2 ml s−1 at 400 °C for 4 h. All catalysts were characterized using Hydrogen Temperature Programmed Reduction (H2-TPR), X-ray Diffraction (XRD), and Brunauer-Emmet-Teller (BET) isotherm methods to find the interaction between metals, the crystallinity of the catalyst, surface area and pore volume of the catalyst, respectively. The 3.3% CuO-3.3% MnO2-3.3% NiO/Ce0.75Zr0.25O2 catalyst showed higher catalytic activity for benzene oxidation with benzene conversion of 90% at 250 °C and weight hourly space velocity (72,000 mL g−1 h−1) when compared to one metal oxide only. This finding presents a high activity and low-cost catalysts for removing a very lean concentration of benzene containing in the industrial flue gas at low temperatures.

A combination of the experimental and numerical methods was used to investigate the fluid flow behaviors in a proposed cyclone burner. Recirculation flow and pressure drop, two of the important fluid flow behaviors that affect the burner's performance, have been studied here. Experimentally, the recirculation flow phenomenon in the burner was observed through paper slices dynamic in a transparent burner, and pressure drop was measured using a tube manometer. Meanwhile numerically, the fluid flow behaviors were simulated using the standard k-e turbulence model, under Ansys-Fluent software. The simulation results showed that, at a certain value of inlet aspect ratio (R IA ) and initial tangential intensity (I IT ), especially for high I IT , the recirculation flow phenomenon was clearly observed in the center of the burner cylinder which closely resembles a tornado-tail. The indication of existence recirculation flow was also found from the experiment results. The study also exhibited that the results of simulated static pressure drop were closely approaching the experiment results, particularly for I IT values £ 4.3. The mean deviation of static pressure between the simulation and the experiment results, for a varied range of R IA and I IT ,was about 15%. From the results above, it was obvious that fluid flow behaviors (recirculation flow and static pressure) in the proposed cyclone burner are greatly influenced by the R IA and I IT values, where the I IT effect was more significant compared to the R IA . This study also suggests that, the standard k-e turbulence model could be relied upon to well predict the behaviors of fluid flow in the proposed cyclone burner, at low to moderate swirl intensities.

Gas leakage is one of hazard sources in a gas processing plant, where the released gas may form vapor cloud, which is dispersed or accumulated. At certain concentration, the vapor cloud may induce fire and explosion, which could harm people, equipment and environment. The effects of the incidents can be estimated to determine the consequences and to improve the plant design. Due to several complexities including congestion of plant equipment, 3D CFD model was developed to represent real configuration. In this study, the as-built 3D plant geometry and FLACS software were utilized to run the CFD model simulation to evaluate the quantity and placement of the existing gas detectors. The recommendation given according to evaluation results was to install two additional gas detectors. Thereby, in the case of gas leak, the gas detection system may alarm personnel and preventive action may be taken into consideration. The effects of explosion result from the selected scenario were predicted to not be able to cause steel frame distortion or eardrum rupture. These demonstrated that the evaluation of release consequence using 3D CFD model gave more advantage than 2D method by representing accurately physical characteristic of gas dispersion and explosion, which could eventually improve the plant safety strategy.

Flow structure inside a chamber greatly determines the process performances. Therefore, the flow structure inside a chamber are often constructed in such a way as an effort to obtain equipment performances in accordance with the expectations. This study explored flow structure inside several chamber geometries and operating conditions. Three types of chamber, namely; GTC, DTC and TJC were set as the investigated chambers. The Computational Fluid Dynamics technique, supported by some experimental data from the literature, is used as an investigation method. The RANS based models, under Ansys-Fluent software were used in this numerical investigation. Simulation results revealed that the flow structures of GTC and DTC are predominantly created by spiral and vortex patterns. The vortex stabilizer diameter in the GTC affects the vortex pattern, velocity profile and pressure drop. The flow structure of DTC presents the most complex behavior. The flow structure inside TJC, in the case of unconfined outlet boundary, is characterized by the helical and wavy jet pattern. This structure is determined by the initial tangential intensity (IIT) and the inlet aspect ratio (RIA). The structures of vortex, helical, and wavy axial flow are properly constructed and visualized in this paper. There is no a turbulence model which is always superior to the other models, consistently. The standard k-ε model exhibits the realistic and robust performances among all of investigatied cases.

Solid fuel combustion is always preceded by chemical decomposition. This process is largely determined by the flow structure and affected by the geometry and operating conditions of the combustion chamber. This study aimed to investigate the effect of relative axial inlet diameter (Dai//Dbc) on the flow structure in the proposed cyclone burner. The flow structure was determined with the standard k-e turbulent model using the Ansys-Fluent software. From the simulation results it was concluded that with all the axial inlet diameters used an integrated vortex formed in the center of the burner cylinder. The integrated vortex consisted of two vortices, namely a primary vortex and a secondary vortex. The primary vortex penetrated from the furnace box to the burner cylinder, while the secondary vortex was formed in the burner cylinder itself. There were two integration patterns from the primary vortex and the secondary vortex, namely a summation pattern and a multilayer pattern. The presence of a vortex in the center of the burner cylinder is allegedly responsible for an increase in the degree of mixing and pressure drop in that zone. The flow structure induced from the proposed burner had high symmetricity and was largely determined by the burner's axial inlet diameter.

A steady state hydrogen separation through a Pd–Ag membrane from a gas mixture like synthesis gas may encounter a rapid decrease of hydrogen permeation due to interaction of hydrogen and nitrogen, which blocks the palladium surface. In this study, a dedicated composition modulation for enabling unsteady state operation of the feed gas was proposed to control the process of hydrogen permeation and improve the stability of the Pd–Ag membrane. The investigated parameters were focused on hydrogen recovery and deactivation time as influence of varying the switching time. The application of the unsteady state operation on Pd75–Ag25 membrane obviously showed the influence of the dynamic operation on the performance of H2 permeation, which decreased or increased, depending on the switching times. The unsteady operation with switching times 1 and 5 min resulted in the H2 recovery of 27% and 24%, respectively, without showing any deactivation times. It has also been observed during experiment that the unsteady state operation of the Pd75–Ag25 membrane for hydrogen separation could show better performance compared to steady state operation if proper transient operation procedure could be developed.

The role of the presence of Ag atom in Pd 3 Ag(111) surface on the adsorption of N and H atoms and NH species was studied by using first principles calculations based on density functional theory (DFT). The adsorption energies of N and NH species are weakened by at least 0.50 eV when Ag atom is one of the nearest neighbors, in contrast to the case of H, in which the adsorption energies are weakened by at most 0.15 eV. Local density of states (LDOS) profiles show that for N and NH adsorption near the silver alloy atom, the derived anti-bonding states are shifted below the Fermi level and hence the adsorption energy is weakened on the alloyed surface. In the presence of adsorbed N, the adsorption energies of H on the nearby sites are also reduced. Nonetheless, this reductions in H adsorption energies on the most stable sites are lower in Pd 3 Ag(111) surface. NH formations with H moving across the Pd atom on both surfaces show comparable activation barriers but the barrier is increased by 0.2–0.3 eV when the formation happens across Ag atom.

The stability of reactor operation for catalytic oxidation of lean CH4 has been investigated through modeling and simulation, particularly the influence of switching time and heat extraction on reverse flow reactor (RFR) performance. A mathematical model of the RFR was developed, based on one-dimensional pseudo-homogeneous model for mass and heat balances, incorporating heat loss through the reactor wall. The configuration of the RFR consisted of inert-catalyst-inert, with or without heat extraction that makes it possible to store the energy released by the exothermic reaction of CH4 oxidation. The objective of this study was to investigate the dynamic behavior of the RFR for lean methane oxidation and to find the optimum condition by exploring a stability analysis of the simple reactor. The optimum criteria were defined in terms of CH4 conversion, CH4 slip, and heat accumulation in the RFR. At a switching time of 100 s, the CH4 conversion reached the maximum value, while the CH4 slip attained its minimum value. The RFR could operate autothermally with positive heat accumulation, i.e. 0.02 J/s. The stability of the RFR in terms of heat accumulation was achieved at a switching time of 100 s.

Hydrogen absorption from surface to second subsurface layer of ordered and substitutionally disordered Pd 3 Ag(110) was investigated by performing density functional theory-based calculations. Ag segregation to topmost layer was found to be energetically favored for clean surface structure. The absorption of H in the alloy surface, for both ordered and substitutionally disordered structures, is generally characterized by lower activation barrier as compared to pure Pd surface. When H is present in the surface or subsurface regions, our results strongly suggest the tendency of subsurface Pd atoms to segregate to the surface or near surface region. The reverse segregation of Pd, along with the large lattice constant and the modified electronic structure of Pd atoms in Pd 3 Ag alloy could help in understanding the experimentally determined high hydrogen permeability of PdAg membranes.

This paper describes akinetic study for the determination of the kinetic parameters of lean methane emission oxidation over Pt/γ-Al 2 O 3 in a dedicated laboratory scale fixed bed reactor. A model ofthemechanistic reaction kinetic parameters has been developed. The reaction rate model was determined using therate-limiting step method, which was integrated and optimized to find the most suitable model and parameters. Based on this study, the Langmuir-Hinshelwood reaction rate model with the best correlationis the one where the rate-limiting step is thesurface reaction between methane and one adsorbed oxygen atom. The pre-exponential factor and activation energy were 9.19 x 10 5 and 92.04 kJ/mol, while the methane and oxygen adsorption entropy and enthalpy were –17.46 J/mol.K, –2739.36 J/mol,–16.34 J/mol.K, and –6157.09 J/mol, respectively.

The governing equations describing methane oxidation in a reverse flow reactor are given by a set of convective-diffusion equations with a nonlinear reaction term, where temperature and methane conversion are dependent variables. In this study, the process is assumed to be a one-dimensional pseudo- homogeneous model and takes place with a certain reaction rate in which thewhole process ofthereactor is still workable. Thus, the reaction rate can proceed at a fixed temperature. Under these conditions, we can restrict ourselves to solving the equations for the conversion only. From the available data, it turns out that the ratio of the diffusion term to the reaction term is small. Hence, this ratio is considered as a small parameter in our model and this leads to a singular perturbation problem. Numerical difficulties will be found in the vicinity of a small parameter in front of a higher order term. Here, we present an analytical solutionby means of matched asymptotic expansions. The result shows that, up to and including the first order of approximation, the solution is in agreement with the exact and numerical solutions of the boundary value problem.

Hydrogen separation from nitrogen containing gas mixture using Pd–Ag membrane shows a time lag and low hydrogen recovery during start-up period. In this study, forced unsteady state operation using a composition modulation of the feed gas was employed as a new operation method to increase the hydrogen recovery and to shorten the time lag. In this work, the performance of Pd75–Ag25 membrane during the separation of hydrogen from H 2 /N 2 mixture under forced unsteady state operation at 623 K was investigated. During natural start-up without forced operation, the hydrogen recovery results in 35% and 14% for H 2 /N 2 feed gas compositions of 70%/30% and 50%/50%, respectively, while the time lag in the natural operation results in 195 and 147 min for H 2 /N 2 feed gas compositions of 70%/30% and 50%/50%, respectively. The experimental results show that forced unsteady state operation affects considerably on hydrogen recovery from H 2 /N 2 mixture and the time lag during start-up. The maximum hydrogen recovery in the forced unsteady state operation is 60%, obtained at switching time 5 min and H 2 /N 2 feed gas composition of 70%/30%, while for H 2 /N 2 feed gas composition of 50%/50% the hydrogen recovery is not significantly influenced by switching time. The time lag indicates a profound decay trend monotonically by decreasing the switching time for both H 2 /N 2 feed gas compositions.

An analysis of reverse flow operation and its experimental study for ammonia oxidation to produce either N 2 , N 2 O, and NO have been carried out. An experimental set- u p of reverse flow reactor was constructed for a laboratory scale. The experiment under steady state operation was performed as a base case in order to judge the potential during the reverse flow operation. Aim was to investigate the behavior of reverse flow operation and to observe the reactor performance. Focus was on the comparison of the stead y state and reverse f low operations. The experiments show that the behavior of reverse flow reactor is strongly influenced by the ratio of the switching time over the residence time. The ammonia conversion during the regular reverse flow operation shows lower values compared to the steady state operation which is even worse during asymmetric mode. The product distributions may change under f low reversal, depending on the operating conditions, regime of operation, and operation mode. Keyw ords : Reverse Flow Operation, Fixed Bed Reactor, Selectivity Manipulation, Steady State Operation, Ammonia Oxidation Abstrak Sebuah analisis operasi aliran bolak-balik dan studi eksperimental oksidasi amoniak untuk menghasilkan baik N 2 ., N 2 O, dan NO telah dilakukan. Sebuah perangkat eksperimen reaktor aliran bolak-balik dikonstruksi untuk skala laboratorium. Eksperimen dalam operasi keadaan tunak dilakukan sebagai kasus dasar untuk menilai potensi operasi aliran bolak-balik. Tujuan penelitian ini adalah untuk meneliti kelakuan operasi aliran bolak-balik dan untuk mengamati kinerja reaktor. Kajian ini dititikberatkan pada perbandingan operasi keadaan tunak dan operasi aliran bolak-balik. Hasil percobaan menunjukkan bahwa kelakuan reaktor aliran bolak-balik sangat dipengaruhi oleh nisbah waktu pembalikan arah aliran (switching time) terhadap waktu tinggal. Konversi amomiak dalam operasi aliran bolak-balik menunjukkan nilai yang lebih rendah dibandingkan dengan operasi keadaan tunak dan dalam mode asimetrik konversinya bahkan lebih rendah lagi. Distribusi produk dapat berubah dalam pembalikan aliran yang bergantung pada kondisi-kondisi operasi, daerah operasi, dan mode operasi. Kata Kunci : Operasi Aliran Bolak-balik, Reaktor Fixed Bed, Manipulasi Selektivitas, Operasi Tunak, Oksidasi Amoniak

A study on simulation and optimization of coupling reaction between methanol synthesis and isopropyl alcohol (IPA) dehydrogenation was performed. The analysis is carried out theoretically to obtain the optimum operation conditions which give the best performance. The reactions are just interacting thermally. In this study, both reactions are held catalytically in a heat-exchanger type reactor. As a high pressure reaction, methanol synthesis is placed in the inner side of reactor tube while dehydrogenation of IPA is in the opposite. Tube wall acts as a heat transfer media. The reactor is modeled by a steady state heterogeneous equation for a fixed bed reactor. Optimization is done in order to find the optimum value of operation conditions, those are the inlet temperature of both side of reactor and the molar feed flow ratio between the exothermic side and the endothermic side. Sum of weighted reaction conversion is considered to be the objective function that is maximized. The simulation result shows that coupled reactor makes the reaction conversion higher than a conventional adiabatic reactor and the optimum operation conditions give the maximum value of the conversion. This study presents a theoretical proof that coupling reaction is feasible. Keywords: coupling reaction, IPA dehydrogenation, methanol synthesis, optimization, simulated annealing Abstrak Telaah mengenai simulasi dan optimisasi reaksi perangkaian (coupling reaction) antara sintesis metanol dengan dehidrogenasi isopropil alkohol (IPA) telah dilakukan. Analisis dilaksanakan secara teoretik guna mendapatkan kondisi optimum yang akan memberikan hasil terbaik. Pada penelitian ini, kedua reaksi dilaksanakan secara katalitik dalam reaktor bertipe buluh-cangkang. Karena bertekanan tinggi, sintesis metanol ditempatkan pada sisi buluh, sedangkan dehidrogenasi IPA ditempatkan pada sisi cangkang. Dinding buluh berperan sebagai media perpindahan panas. Reaktor dimodelkan dengan reaktor heterogen tunak unggun tetap. Optimisasi dilakukan dalam rangka mendapatkan nilai optimum dari kondisi operasi yang mencakup temperatur inlet sisi eksotermik dan endotermik serta rasio umpan molarnya. Jumlah total konversi reaksi terbobotkan dipilih sebagai nilai objectif yang akan dioptimumkan. Hasil simulasi menunjukkan bahwa reaktor perangkaian termal mampu meningkatkan konversi reaksi jika dibandingkan dengan reaktor adiabatik dan pada kondisi operasi yang optimum diperoleh konversi maksimal. Penelitian ini menunjukkan bahwa reaksi perangkaian layak untuk dilaksanakan. Kata kunci : reaksi perangkaian, dehidrogenasi IPA, sintesis methanol, optimisasi, simulated annealing

Modeling and simulation of reverse flow reactor for the catalytic oxidation of methane: the development of start-up operating procedures In this modelling and simulation study, three operating procedures during start-up of lean methane (1%-v) oxidation in reverse flow reactor (RFR) have been investigated to get auto-thermal condition, high methane conversion, faster pseudo steady state, and low preheating energy requirement. The RFR model developed based on one-dimension pseudo-homogeneous model for mass balance and heterogeneous model for energy balance. Procedure 1 , the preheating was employed only on the catalyst zone, fails to conduct the auto-thermal reaction and to achieve high conversion. Procedure 2, the preheating was employed for inert and catalyst of left side only, able to achieve the auto-thermal up to switching time (ST) 230 s. Procedure 3, the preheating was employed along the reactor bed, achieve the auto-thermal condition up to ST 300 s. Procedure 2 and 3 achieved the pseudosteadystate at 1000 s for ST 200 s with total conversion during start-up are 95% and 99%. The conversion of Procedure 3 higher than Procedure 2, unfortunately the heat load of Procedure 3 two times higher than Procedure 2. Keywords: modelling and simulation, catalytic methane oxidation, start-up procedure, reverse flow reactor, switching time Abstrak Di dalam studi pemodelan dan simulasi ini, berbagai prosedur operasi reverse flow reactor (RFR) selama start-up untuk oksidasi katalitik metana encer (1%-v) dikaji dengan target sistem beroperasi secara ototermal, konversi metana tinggi, waktu pencapaian kondisi tunak semu (pseudosteady state) cepat, dan beban panas rendah. Pemodelan reaktor didasarkan pada model satu dimensi dan pseudohomogeneous untuk neraca massa, serta heterogen untuk neraca energi. Pemanasan katalis saja pada awal reaksi (Prosedur 1) tidak dapat mencapai kondisi reaktor yang ototermal. Pemanasan katalis dan inert bagian kiri (Prosedur 2) mampu mencapai kondisi reaktor yang ototermal hingga switching time (ST) 230 detik. Pemanasan seluruh bagian reaktor pada awal reaksi (Prosedur 3) mampu mencapai kondisi reaktor yang ototermal pada ST paling lama 300 detik. Prosedur start-up 2 dan 3 untuk ST 200 detik sama-sama mencapai waktu pseudosteady state pada 1000 detik dengan konversi total selama start-up masing-masing 95% dan 99%. Meskipun Prosedur 3 memberikan konversi sedikit lebih tinggi daripada Prosedur 2, namun beban panas Prosedur 3 mencapai dua kali lebih besar daripada Prosedur 2. Kata kunci: emisi metana, pemodelan dan simulasi, prosedur start-up, reverse flow reactor, switching time.

The terminology of micro-reactor development is one of the keywords in process intensification, which plays an important role, particularly in the reaction system requiring extremely large heat and mass transfers. This paper conveys an idea about miniaturization of the combustion engine through a combination of fuel processor system and fuel cell system. Hydrogen as a fuel cell feedstock is provided in-situ by methanol reforming. The synthesis gas produced by reformer is introduced into preferential oxidation reactor to remove CO before it enters the fuel cell. The process system for producing hydrogen is equipped in the micro-technology package as an answer to hydrogen storage at high pressure, which meets several shortcomings. Keywords: Process intensification; Modeling and simulation; Micro-reactor technology Abstrak Terminologi pengembangan reaktor mikro merupakan salah satu 'kata kunci' dalam intensifikasi proses yang memainkan peranan penting, terutama dalam sistem reaksi yang memerlukan laju perpindahan panas dan massa yang besar. Makalah ini menyampaikan gagasan tentang miniaturisasi mesin kendaraan bermotor melalui kombinasi sistem proses or bahan bakar dan sel bahan bakar. Hidrogen yang diperlukan sebagai umpan sel bahan bakar disediakan secara insitu dari reformasi metanol. Gas sintesis dari reformer diumpankan ke dalam reaktor oksidasi preferensial untuk menyisihkan CO sebelum diumpankan ke dalam sel bahan bakar. Rangkaian sistem proses penyedia hidrogen secara insitu ini dikemas dalam paket teknologi mikro sebagai jawaban atas kebuntuan sistem penyediaan hidrogen pada tekanan tinggi yang memiliki banyak kelemahan. Kata Kunci: Intensifikasi proses; Pemodelan dan simulasi; Teknologi reaktor mikro

Operation method of reverse flow reactor with fluctuating feed for methane gas emmision processing in compressor station. The leak of CH4 from the compressor stations can not be avoided and it may cause the global warming. The impact of the global warming can be reduced by oxidizing CH4 into CO2. The CH4 capture strategy using the exhaust mounted on the top of the building causes (1) CH4 levels detected in the gas mixture is very small (±1% volume), (2) the feed gas temperature is near the ambient temperature (±30 oC), (3) the CH4 concentration fluctuates over time. The reverse flow reactor (RFR) is a fixed bed reactor, which has the ability to abate the leak of CH4 and has the ability to act as an autothermal reactor. The purpose of this research is to find a proper operation procedure of the fixed bed reactor for the oxidation of lean methane emission via modeling and simulation. The reactor model is based on the continuity equation and the heat balance, while the concentration of the feed gas behavior dynamic and modeled as a step function. The model was solved numerically using the software package FlexPDE version 6. At ST (switching time) 50 seconds, the RFR operates autothermally with heat accumulation in the inert section fluctuating between 12.4 to 14.2 kJ. At ST 100 seconds, the heat trap inside the reactor increases monotonically. The use of ST 100 seconds requires an additional operation procedure to keep the reactor safe. Keywords : Global warming, concentration dynamic, autothermal operation, modeling and simulation, reverse flow reactor. Abstrak Kebocoran gas CH 4 dari stasiun kompresor tidak dapat dihindarkan dan ini merupakan salah satu sumber penyebab pemanasan global. Dampak pemanasan global ini dapat dikurangi dengan mengoksidasi gas CH 4 menjadi gas CO 2 . Strategi penangkapan gas CH 4 menggunakan exhaust yang terpasang pada bagian atas gedung menyebabkan (1) kadar CH 4 yang terdeteksi dalam campuran gas cukup kecil (±1% volume), (2) temperatur gas umpan mendekati temperatur ruangan (± 30 o C), (3) konsentrasi gas CH 4 akan berperilaku dinamik. Reverse flow reactor (RFR) mempunyai kemampuan untuk mengatasi akibat yang ditimbulkan oleh proses penangkapan gas CH 4 di stasiun kompresor dan mempunyai kemampuan secara ototermal. Tujuan penelitian ini adalah mendapatkan metode operasi yang tepat untuk mengatasi gas umpan yang berperilaku dinamik. Model yang dikembangkan mengacu pada persamaan kontinuitas dan konsentrasi gas umpan yang berperilaku dinamik dimodelkan sebagai fungsi step. Model diselesaikan menggunakan software FlexPDE versi 6. Penggunaan switching time (ST) yang tepat dapat mengatasi permasalahan konsentrasi gas umpan yang berperilaku dinamik. Pada ST 50 detik, RFR mampu bekerja secara ototermal dengan nilai akumulasi panas di bagian inert yang berfluktuasi antara 12,4–14,2 kJ. Pada ST 100 detik, panas yang terjebak di dalam reaktor semakin lama semakin meningkat. Penggunaan ST 100 detik memerlukan prosedur operasi tambahan untuk menjaga reaktor agar tidak meleleh dan menjaga reaktor tetap beroperasi secara ototermal. Kata Kunci : Pemanasan global, dinamika konsentrasi, operasi ototermal, pemodelan dan simulasi, reaktor aliran bolak-balik.

Study of utilization of reverse flow reactor for the catalytic oxidation of gasoline vapor Catalytic oxidation of gasoline vapor is one of methods to reduce the gasoline vapor emission at fuel station. This reaction is exothermic with large heat of reaction, so that the heat released can be used for heating the feed gas, leading to auto thermal condition.. The auto thermal conditions with low feed concentration, like gasoline vapor emission, can be achieved by using a reverse-flow reactor (RFR), a kind of fixed bed reactor in which flow direction is periodically changed. The objective of this research is to develop the using of a RFR to reduce the gasoline vapor emissions at fuel station, based on simulations using FlexPDE version 6 and later used as the basis for the experimental development. The model of RFR was developed, by using iso-octane as a model component. The simulation consists of: (1) RFR with one way direction, which was used as the basis for the determination of RFR operating conditions and (2) RFR at current start-up conditions. The simulations were conducted using a software package FlexPDE version 6. The kinetic parameters and physical properties were taken from literature. The simulation results of the RFR at one way direction show that catalytic oxidation of gasoline vapor can conducted best at temperature of 773 K, while the RFR shows the accumulation of heat in the reactor bed that can be utilized for process start-up. Time to reach 100% conversion of gasoline for reverse flow operation mode is faster than one way operation mode. Thus the operation of gasoline emission catalytic oxidation reaction in reverse flow reactor can be developed experimentally. Keywords: Dynamic reactor, Catalytic oxidation Abstrak Oksidasi katalitik uap bensin adalah salah satu cara untuk mengurangi emisi uap bensin di stasiun pengisian bahan bakar umum. Reaksi ini adalah reaksi eksotermik, sehingga panas reaksi yang timbul dapat dimanfaatkan untuk memanaskan umpan agar reaktor dapat berperilaku ototermal. Kondisi ototermal dengan umpan emisi uap bensin yang berkonsentrasi rendah dapat tercapai dengan menggunakan reverse flow reactor (RFR), yaitu reaktor unggun tetap yang arah alirannya diubah secara periodik. Tujuan kajian ini adalah untuk mengkaji pemanfaatan RFR untuk menurunkan emisi uap bensin di SPBU, berdasarkan simulasi menggunakan FlexPDE versi 6 dan nantinya digunakan sebagai dasar pengembangan secara eksperimental. Model RFR dikembangkan dengan menggunakan iso-oktana sebagai komponen model. Simulasi terdiri dari (1) simulasi RFR satu arah, yang digunakan sebagai dasar penentuan kondisi operasi RFR dan (2) simulasi RFR dengan konfigurasi start-up tertentu. Parameter kinetika dan sifat–sifat fisik yang diperlukan diambil dari literatur. Hasil simulasi RFR satu arah menunjukkan bahwa reaksi oksidasi katalitik uap bensin dapat terselenggara dengan baik pada suhu 773 K, sedangkan simulasi RFR kondisi aliran bolak-balik menunjukkan adanya akumulasi panas di unggun reaktor yang dapat dimanfaatkan saat proses start-up. Waktu untuk mencapai konversi 100% untuk simulasi mode operasi bolak-balik lebih cepat daripada mode operasi satu arah. Dengan demikian penyelenggaraan reaksi oksidasi katalitik emis uap bensin di reverse flow reactor secara eksperimental dapat dikembangkan. Kata Kunci: Reaktor dinamik, Oksidasi katalitik