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"ABSTRAKPenelitian ini bertujuan menerapkan metode computational fluid dynamics dalam scale-up reaktor batch berpengaduk dengan studi kasus proses penghilangan getah minyak sawit mentah. Dalam scale-up tersebut, kesebangunan geometri reaktor tidak bisa dipenuhi. Koefisien perpindahan massa volumetrik kca dijadikan parameter kesamaan. Koefisien perpindahan massa yang diperoleh dari pengukuran laboratorium dikorelasikan dalam bentuk bilangan Sherwood sebagai fungsi bilangan Reynolds butir dan bilangan Schmidt dengan bentuk persamaan Shd = 0,02576 Red0,673Sc0.431. Luas bidang antarfasa diturunkan dari hasil simulasi menggunakan model mixture, setelah divalidasi dengan persamaan empiris. Sebagai acuan, digunakan kondisi operasi skala laboratorium 500 rpm dan 80 C dengan nilai kca sebesar 5,551x10-6 s-1. Simulasi reaktor skala besar dilakukan dengan variasi jenis impeller radial dan aksial , serta kecepatan putar 40, 75, 93, 141, dan 500 rpm . Dengan variasi tersebut, tidak diperoleh kesamaan nilai kca. Dari ekstrapolasi tren linear kca vs rpm, diperkirakan kriteria kesamaan diperoleh pada kecepatan 16,07 rpm. Namun, simulasi pada kecepatan tersebut tidak memberikan nilai yang diperkirakan. Penyebabnya gravitasi menjadi lebih dominan terhadap medan aliran sehingga dispersi tidak merata dan nilai kca terlalu kecil. Diperlukan studi lebih lanjut mengenai parameter geometri reaktor yang menghasilkan dispersi merata, sehingga dicapai kriteria kesamaan dalam scale-up reaktor.

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ABSTRACTThis research aims to implement computational fluid dynamics for scale up of stirred batch reactor with case study of CPO degumming process. Reactor geometric similarity cannot be maintained while scale up. Volumetric mass transfer coefficient kca becomes similarity criteria. Mass transfer coefficient from laboratory data is correlated in Sherwood number as the function of drop Reynolds number and Schmidt number with the form Shd 0.02576 Red0,673Sc0.431. Interfacial area is derived from simulation using mixture model, by validating to empirical correlation. Laboratory scale reactor operating condition of 500 rpm, 80 C with kca of 5.551x10 6 s 1 is set as reference. Simulation of large scale reactor is run by varying the impeller type radial and axial and speed 40, 75, 93, 141, and 500 rpm . However, by those variations, kca similarity cannot be achieved. By extrapolating the linear trend between kca vs rpm, similarity is expected at 16.07 rpm. However, simulation doesn rsquo t confirm that. This is due to gravitational effect become more dominant and the equal dispersion is not obtained so that the kca is too low. It needs further investigation of the reactor geometries that will produce equal dispersion, so that similarity criteria of scale up can be achieved. "

"ABSTRAKPenelitian ini bertujuan untuk mempelajari hidrodinamika dalam reaksi transesterifikasi pada reaktor batch berpengaduk. Parameter hidrodinamika yang didapatkan kemudian digunakan sebagai kriteria kesamaan scale-up. Penelitian ini menerapkan metode computational fluid dynamics CFD dalam studi hidrodinamika fluida pada reaksi transesterifikasi di reaktor batch berpengaduk. Pemodelan reaktor batch berpengaduk untuk reaksi transesterifikasi dikomputasi dengan menggunakan COMSOL Multiphysics. Nilai kecepatan fluida, pola aliran, distribusi tekanan, fraksi volume, kerapatan jumlah partikel, kecepatan relatif, shear rate, diameter butir fasa terdispersi, serta luas bidang antarfasa spesifik a didapatkan. Nilai a pada reaktor skala laboratorium didapatkan sebesar 45120 1/m dan dijadikan sebagai parameter kesamaan scale-up. Dengan ukuran reaktor skala besar sebesar 1,309 m3, diperlukan kondisi operasi kecepatan putar impeller sebesar 285,16 rpm untuk mendapatkan nilai luas bidang antarfasa spesifik a yang sama dengan kriteria kesamaan scale-up.

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ABSTRACTThe purposes of this research is to study the hydrodynamics of transesterification reaction in stirred batch reactor. The obtained hydrodynamics then used as scale up similariy criterion. This research used computational fluid dynamics CFD as method to study the transesterification in stirred batch reactor. By using COMSOL Multiphysics, the modeled transport equation is computed. The hydrodynamics parameters observed are mean velocity field, flow pattern, pressure distribution, volume fraction of dispersed phase, number density of droplet, dispersed phase relative velocity, shear rate, average diameter of dispersed phase droplet, and interfacial area per volume. The simulation results show that the specific interfacial surface area a on laboratorium scale reactor is 45120 1 m and used as scale up similarity criterion. For 1,31 m3 large scale reactor, the rotational speed condition to obtain specific interfacial surface area a is 285,16 rpm to match the scale up similarity criterion."

"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."

"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."

"Industri yang menggunakan bahan bakar fosil terus berkembang dan mengakibatkan kebutuhan akan minyak bumi semakin meningkat. Akan tetapi, minyak bumi yang akan habis menyebabkan diperlukannya bahan baku alternatif. Salah satu bahan baku alternatif yang saat ini paling berpotensi adalah biomassa dari kayu tumbuhan, yang dapat digunakan untuk memproduksi bio oil menggunakan proses pirolisis. Kinetik pirolisis biomassa kayu pada penelitian ini diwakilkan dengan hemiselulosa, dimulai dari tahap aktivasi biomassa hingga terdekomposisi menjadi komponen-komponen kecil, seperti gas hidrogen, gas karbon monoksida, hingga char, seperti yang diusulkan oleh Dussan et al. (2017). Dari berbagai macam reaktor pirolisis yang ada, reaktor yang diteliti pada penelitian ini adalah fluidized bed. Reaktor pirolisis dimodelkan dengan pendekatan computational fluid dynamics dengan metode Euler berdasarkan model Xue et al. (2010) kemudian disimulasikan menggunakan software COMSOL Multiphysics. Simulasi yang dilakukan pada suhu 700 K menghasilkan konversi biomassa mencapai 95,5%. Produksi bio oil dan gas hidrogen yang optimal berada pada suhu 700 K, laju alir nitrogen 2 L/menit dan kecepatan fluidisasi 0,083 m/s. Sedangkan, untuk produksi gas karbon monokisda yang lebih banyak, suhu sistem berada pada 650 K, laju alir nitrogen 2,7 L/menit, dan kecepatan fluidisasi 0,073 m/s.

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Industries that use fossil fuels continue to grow and result in increasing demand for petroleum. However, petroleum that will run out causes the need for alternative raw materials. One alternative raw material that is currently the most potential is biomass from plant wood, which can be used to produce bio oil using the pyrolysis process. The kinetic pyrolysis of wood biomass in this study is represented by hemicellulose, starting from the biomass activation stage to decomposing into small components, such as hydrogen gas, carbon monoxide gas, to char, as proposed by Dussan et al. (2017). Of the various types of pyrolysis reactors that exist, the reactor examined in this study was fluidized bed. The pyrolysis reactor was modeled using the computational fluid dynamics approach using the Euler method, based on Xue et al. (2010) model, and then simulated using COMSOL Multiphysics software. Simulations carried out at a temperature of 700 K resulted in biomass conversion reaching 95.5%. The optimal production of bio oil and hydrogen gas is at a temperature of 700 K, nitrogen flow rate of 2 L/minute and fluidization speed of 0.083 m/s. Whereas, for the production of more monocyte carbon gas, the system temperature is at 650 K, nitrogen flow rate is 2.7 L/minute, and fluidization velocity is 0.073 m/s."

"Model reaktor pembentukan metanol merupakan faktor yang penting untuk menentukan parameter kinetika reaksi pembentukan metanol. Walaupun demikian, model yang digunakan dalam riset-riset mengenai kinetika metanol yang ada masih menggunakan model yang disederhanakan. Graaf et.al (1982) mengevaluasi kinetika percobaanya dengan model CSTRsatu dimensi, sementara Froment dan Bussche (1996) mengevaluasi parameter kinetikanya dengan model reaktor homogen-semu satu dimensi. Penelitian ini bertujuan untuk memodelkan reaksi pembentukan metanol dalam sebuah reaktor unggun diam multitubular tiga dimensidengan menggunakan Computational Fluid Dynamics (CFD) yang dikoplingdengan efek perpindahan panas dan perpindahan massa dalam reaktor multitubular. Evaluasi model berupa karakterisasi pola aliran dalam tube dan shell, karakterisasi temperatur tube dan shell, distribusi konsentrasi dalam tube. Kondisi operasi reaktor suhu inlet tube sebesar 230°C, tekanan 76.89 bar, dan komposisi inlet seperti yang ditentukan darivalidasi penelitian oleh Samimi et.al (2018). Dari hasil simulasi didapat nilai optimal kecepatan aliran pendinginan sebesar 3 m/s dan parameter faktor tumbukkan laju reaksi A1 dan A7 sebesar 1.685 dan 1.6, dengan kesalahan parameter terbesar adalah konsentrasi CO sebesar 33% error.

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The methanol formation reactor model is an important factor for determining the kinetics parameters of the methanol formation reaction. Nonetheless, the model used on existing research in methanol kinetics still uses a simplified model. Graaf et.al (1982) evaluated the experimental kinetics with the one dimensional CSTR model, while Froment and Bussche (1996) evaluated the kinetic parameters with the model of one dimensional pseudo homogeneous reactor. This study aims to model the reaction of methanol formation in a three-dimensional multitubular fixed bed reactor using Computational Fluid Dynamics (CFD) coupled with the effects of heat transfer and mass transfer in multitubular reactors. Evaluation of the model in the form of characterization of flow patterns in the tube and shell, characterization of tube and shell temperature, and characterization of concentration distribution in the tube. The operating conditions of the reactor inlet tube temperature are 230 ℃, pressure 76.89 bar, and the composition of the inlet as determined from the validation of research by Samimi et.al (2018). The simulation results obtained an optimal value of flow velocity 3 m/s and the collision factor of A1 and A7 is 1.6685 and 1.6 respectively, with the biggest error being the CO concentration of 33% error."