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"ABSTRAKKonversi CO2 menjadi metanol dapat ditingkatkan dengan menggunakan katalis dalam reaksinya. Katalis yang biasa dipakai untuk hidrogenasi CO2 menjadi metanol adalah katalis log am kompleks CuO/ZnO/AI203. Akan tetapi, katalis ini masih memiliki kekurangan yaitu kinerja yang masih rendah dan stabilitas yang kurang baik. Hal ini disebabkan H2 yang harus diabsorpsi oleh katalis untuk reaksi hidrogenasi CO2 Iebih tinggi dibanding reaksi pembuatan metanol dengan umpan CO dan H2. Untuk itu diperlukan tambahan oksida logam PdO yang memiliki kemampuan adsorpsi H2 tinggi.Untuk pengembangan proses hidrogenasi CO2 menjadi metanol perlu dilakukan studi kinetika reaksi dengan tujuan memperoleh persamaan laju reaksi kimia yang berlaku pada rentang kondisi operasi tertentu. Persamaan laju reaksi ini diperlukan dalam perancangan reaktor yang akan digunakan pada skala industri. Pada penelitian ini katalis yang digunakan adalah CuO/ZnO/AI2O3/PdO dengan luas permukaan katalis sebesar 108,6 m2 /gr.Untuk mendapatkan persamaan laju reaksi yang berlaku umum, harus diusahakan agar reaksi secara keseluruhan hanya dikendalikan oleh kejadian-kejadian kimia saja (tidak termasuk adsorpsi eksternal dan internal).Pada studi kinetika makro, model kinetika untuk laju konversi CO2 yang cukup representatif adalah model kinetika hukum pangkat sederhana dengan pendekatan model Cherif, dengan kesalahan absolut rata-rata sebesar 7,31 % dan koefisien korelasi R2 sebesar 89,69 %.Model kinetika untuk laju pembentukan CH3OH yang secara statistik cukup representatif adalah model kinetika hukum pangkat sederhana dengan kesalahan absolut rata-rata sebesar 8,05 % dan koefisien korelasi R2 sebesar 97,54."

"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."

"ABSTRAKDalam penelitian ini dilakukan pemodelan reaktor shiny tipe kolom gelembung untuk sintesis Fischer-Tropsch. Fenomena-fenomena hidrodinamika yang ada di dalam reaktor dipertimbangkan. Pola aliran hidrogen fasa gas dan fasa cair dimodelkan dengan menggunakan konsep dispersi aksial. Persamaan laju reaksi yang digunakan adalah orde pertama untuk hidrogen. Persamaan-persamaan yang diperoleh merupakan model yang sama dengan yang dikembangkan sebelumnya oleh Deckwer dkk [1982].Model yang telah dikembangkan diselesaikan dengan menggunakan metode kolokasi ortogonal enam titik. Persamaan-persamaan aljabar tak-linear yang diperoleh diselesaikan dengan metode iterasi Newton-Raphson. Program yang dikembangkan selain digunakan untuk menghitung profil-profil konsentrasi hidrogen dan katalis, temperatur, kecepatan gas, konversi dan space time yield, juga untuk mensìmulasikan pengaruh temperatur, tekanan, kecepatan gas umpan, rasio CO/H2 umpan, diameter reaktor, panjang reaktor dan konsentrasi katalis terhadap kinerja reaktor.Dari perhitungan, diperoleh bahwa konversi gas sintesis naik dengan naiknya temperatur dan tekanan. Penurunan konversi gas sintesis yang sangat tajam terjadi bila kecepatan gas umpan dinaikkan dan 8 hingga 12 cm/detik. Apabila rasio CO/H2 dinaikkan dan 1,3 hingga 2,5 maka konversi gas sintesis berkurang sekitar 45,78% dari harga awalnya.Konversi gas sintesis berkurang dari 0,882 menjadi 0,778 jika diameter reaktor dinaikkan dari 100 hingga 500 cm. Batas panjang reaktor yang efektif terjadi apabila rasio panjang terhadap diameter reaktor sama dengan 10. Jika konsentrasi katalis bergerak naik dan 8 hingga 20% berat, maka konversi gas sintesis naik sekitar 103,35% dari harga awalnya.Perubahan hold up fasa gas yang disebabkan oleh perubahan kondisi operasi, geometri dan konsentrasi katalis memberikan pengaruh yang lebih sensitif terhadap konversi gas sintesis dibandingkan parameter-parameter hidrodinamika dan perpindahan lainnya.Bila kenaikan perpiridahan massa gas-cair dan panas disebabkan oleh kenaikan temperatur dan tekanan maka dapat menyebabkan konversi gas sintesis naik, Perhitungan menggunakan metode kolokasi ortogonal sembilan titik memakan waktu dua kali Iebih lama dibandingkan enam titik namun memberikan kesaiahan 8304 kali lebih sedifrit dan tjtjk-titik penyelesaian lebih banyak.

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ABSTRACT

In this research a model of Slurry bubble column reactors used for Fischer-Tropsch synthesis was developed. The relevant hydrodynamic phenomenon in the reactors were considered. Flow patterns of gas and liquid phase were modeled using an axial dispersion concept. The model was based on a kinetic rate expression of first order for hydrogen and zero order for carbon monoxide, The differential equations obtained are similar to that of Deckwer [1982].

The model was solved using six points orthogonal -collocation method to get eighteen non-linear algebraic equations that solved numerically by iterative Newton Raphson method. A program was developed to obtain profiles of hydrogen and catalyst concentration, temperature, gas velocity, synthetic gas conversion and space time yield, and to simulate the influences of temperature, pressure, inlet gas velocity, inlet COIH2 ratio, diameter and length of reactor as well as catalyst concentration on the reactor performances.

It was found that synthetic gas Conversion increases with increasing temperature and pressure. An extreme decrease in synthetic gas conversion was obtained when increasing inlet gas velocity from 8 to 12 cm/s. When inlet CO/H2 ratio was raised from 1.3 to 2.5, synthetic gas conversion reduces about 45.78%.

Synthetic gas conversion decreases from 0.882 to 0.778 as the reactor diameter was increased from 100 to 500 cm. The limit of effective reactor lenght is provided when ratio of the reactor lenght to the reactor diameter is 10, When the catalyst concentration was moved from 8 to 20 % vt., synthetic gas conversion raises about 103.35%.

A change in gas phase hold up due to the changes in operating conditions, geometry and catalyst concentration gives more sensitive effects on synthetic gas conversion than the other hydrodynamic and transport parameters.

When an increase in gas-liquid mass and heat transfer due to increase in temperature and pressure, an increase in synthetic gas conversion was occurred.

The calculation of nine collocation points takes twice longer time than that of six COllocation points, but gives less error of 8304 time and more solution points."

"ABSTRAKDalam penelitian ini dilakukan pemodelan reaktor sharry tipe kolom gelembung untuk sintesis Fischer-Tropsch, Fenomena-fenomena hidrodinamika yang ada di dalam reaktor dipertimbangkan. Pola aliran bidrogen fasa gas dan fhsa cair dimodelkan dengan rnenggunakan konsep dispersi aksiai. Persamaan laju reaksi yang digunakan adalah orde pertama unluk hidrogen. Persamaanpersamaan yang diperoleb menipakan model yang sama dengan yang dikembangkan sebelumnya oleh Deckwer dkk [1982}.Model yang telah dikembangkan diselesaikan dengan meuggunakan metode kolokasi ortogonal eriam titik. Persamaan-persamaan aijabar tak-linear yang diperoleh diselesaikan dengan metode iterasi Newton-Raphson Program yang dikembangkan selain digunakan urituk menghitung profil-profil konsentrasi hidrogen dan katalis, temperatur, kecepatan gas, konversi dan space time yield, juga unifik mensimulasikan pengaruh temperatur, tekanan, kecepatan gas umpan., rasio CO/H2 umpan, diameter reaktor, panjang retor dan konsentrasi katalis terhadap kineja reactor.Dari perhitungan, diperoleh bahwa konversi gas sintesis naik dengan naiknya temperatur dan tekanan. Penurunan konversi gas sintesis yang sangat tajam teijadi bila kecepatan gas umpan dinaikkan dan 8 hingga 12 cmldetik. Apabila rasio CO/H2 dinaikkan dad 1,3 hingga 2,5 maka konversi gas sintesis berkurang sekitar 45,78% dan harga awalnya.Konversi gas sintesis berkurang dad 0,882 menjacli 0,778 jika diameter retor dinaikkan dan 100 hingga 500 cm. Batas panjang reaktor yang efektifterjadi apabila rasio panjang terhadap diameter reaktor sama dengan 10. Jika konsentrasi katalis bergerak naik dad 8 hingga 20% berat, maka konversi gas sintesis naik sekitar 103,35% dañ harga awalnya.Perubahan hold up fasa gas yang disebabkan oleh penabahan kondisi operasi, geometri dan konsentrasi katalis memberikan pengaruh yang lebih sensitif terhadap konversi gas sintesis dibandingkan parameter-parameter hidrodinamika dan perpindahan lainnya.Bila kenaikan perpindahan massa gas-cair dan panas disebabkan oleb kenaikan temperatur dan tekanan maka dapat menyebabkan konversi gas sintesis naik. Perhitungan menggunakan metode kolokasi ortogonal sembilan titik memakan waktu dua kali lebih lama dibandingkan enam titik namun memberikan kesalahan 8304 kali lebih sedikit dan titik-titik penyelesaian Iebih banyak.

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ABSTRACT

In this research a model of slurry bubble colu reactors used for Fischer-Tropsch synthesis was developed. The relevant hydrodynamic phenomenon in the reactors were considered. Flow patterns of gas and liquid phase were modeled using an axial dispersion concept. The model was based on a kinetic rate expression of first order for hydrogen and zero order for carbon monoxide. The differential equations obtained are similar to that of Deckwer [1982].

The model was solved using six points orthogonal -collocation --method to get eighteen non-linear algebraic equations that solved numerically by iterative Newton Raphson method. A program was developed to obtain profiles of hydrogen and catalyst concentration, temperature, gas velocity, synthetic gas conversion and space time yield, and to simulate the influences of temperature, pressure, inlet gas velocity, inlet CO/H2 ratio, diameter and length of reactor as well as catalyst concentration on the reactor performances.

It was found that synthetic gas conversion increases with increasing temperature and pressure. Art extreme decrease in synthetic gas conversion was obtained when increasing inlet gas velocity from 8 to 12 cm/s. When inlet CO/H2 ratio was raised from 1.3 to 2.5, synthetic gas conversion reduces about 45.78%.

Synthetic gas conversion decreases from 0.882 to 0.778 as the reactor diameter was increased from 100 to 500 cm. The limit of effective reactor leught is provided when ratio of the reactor lenght to the reactor diameter is 10. When the catalyst concentration was moved from 8 to 20 % vit., synthetic gas conversion raises about 103.35%.

A change in gas phase hold up due to the changes in operating conditions, geometry and catalyst concentration gives more sensitive effects on synthetic gas conversion than the other hydrodynarnic and transport parameters.

When an increase in gas-liquid mass and heat transfer due to increase in temperature and pressure, an increase in synthetic gas conversion was occurred. The calculation of nine collocation points takes twice longer time than that of six collocation points, but gives less err or of 8304 time and more solution points."

"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."

"An adsorbed natural gas storage tank was simulated in this work, with the objective being to predict the filling time, the filling capacity and the storage efficiency. A high-capacity HKUST-1 type metal-organic framework was used as adsorbent. The time-dependent phenomenological model of the adsorbed natural gas storage tank was developed considering mass, momentum and energy transfers. The cylindrical tank was 1.09 m in length with a radius of 0.15 m, and was equipped with an inlet hole for gas inflow. The simulation results show that the temperature increase in the tank due to adsorption heat is very significant. This affects the adsorption ability of the bed inside the tank, so the storage efficiency is consequently low. For the inlet gas flowrate of 50 L/min, the storage efficiency is 38% and increases to only 47% at 5 L/min. Corresponding filling capacities for the two flowrates are not very different, i.e. 89 V(STP)/V and 109 V(STP)/V. However, the difference in the filling times is extremely significant, which are 16 min at 50 L/min and 255 min at 5 L/min."

"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."