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ITS » PhD Theses » Program Doktoral Teknik Kimia
Posted by dee@its.ac.id at 10/10/2012 15:22:13  •  2069 Views


MODEL RATE-BASED DUA-FILM ABSORPSI MULTIKOMPONEN GAS ASAM DALAM LARUTAN KALIUM KARBONAT DENGAN PROMOTOR

TWO FILM RATE-BASED MODEL SOUR ACID MULTICOMPONENT ABSORPTION INTO PROMOTED POTTASIUM CARBONATE SOLUTION

Author :
PUDJIASTUTI, LILY  ( 2308301004 )




ABSTRAK

Absorpsi gas dalam cairan disertai dengan reaksi kimia absorpsi reaktif merupakan operasi yang mendasar dalam berbagai teknologi proses kimia. Pada kilang minyak gas buang harus dimurnikan untuk memenuhi standar pencemaran udara. Pada pabrik pupuk dan petrokimia CO2 harus dihilangkan dari umpan gas asam pada unit sintesis amonia dan unit polimerisasi untuk menghindari terjadinya keracunan katalis. Absorpsi CO2 dengan larutan alkanolamin atau kalium karbonat telah digunakan secara luas untuk menangkap CO2 dan H2S dari gas alam. Namun larutan alkanolamin rentan terhadap degradasi oksidatif pada suhu tinggi. Keuntungan utama dari larutan kalium karbonat sebagai penyerap CO2 adalah kelarutan CO2 dalam sistim karbonatbikarbonat relatif tinggi biaya pelarut dan kebutuhan energi untuk regenerasi pelarut rendah. Kelemahan dan sekaligus tantangan utama absorpsi CO2 oleh larutan kalium karbonat adalah laju reaksi dalam fasa liquida yang relatif rendah sehingga menyebabkan laju perpindahan massa rendah. Oleh karena itu perlu ditambahkan promotor agar tingkat absorpsi meningkat dimana piperazine sering digunakan untuk tujuan ini. Atas dasar pertimbangan ketahanan terhadap degradasi pada suhu tinggi dan keamanan bagi lingkungan maka penelitian ini akan membahas methyldiethanolamine MDEA dan asam borat sebagai promotor alternatif. Telah dilakukan penelitian eksperimen untuk menentukan data kinetika reaksi absorpsi CO2 dengan pelarut K2CO3 dan promotor MDEA atau asam borat menggunakan kontaktor gas-liquida WWC. Data diperoleh pada range temperature 303-323K dan dengan menambahkan promotor masing-masing 12 dan 3 berat. Penambahan 1 2 dan 3 berat MDEA atau asam borat kedalam larutan kalium karbonat dapat meningkatkan absorpsi CO2 secara signifikan. Untuk kedua promotor ada dua model kinetik yang diperoleh dalam penelitian ini. Model pertama berdasarkan konstanta laju reaksi orde dua sedangkan model kedua berdasarkan konstanta laju reaksi pseudo first-order. Laju absorpsi CO2 dalam larutan K2CO3 30 dengan promotor MDEA lebih besar dari pada laju absorpsi CO2 dalam larutan K2CO3 30 dengan promotor asam borat. Penelitian eksperimen juga telah dilakukan untuk menentukan data kesetimbangan larutan fasa gas-cair sistim elektrolit untuk CO2- K2CO3-MDEA-H2O. Pengaruh penambahan promotor MDEA dalam larutan K2CO3 dapat meningkatkan CO2 loading dan menurunkan tekanan parsial gas CO2. Tingkat absorpsi CO2 telah diukur menggunakan Packed Column pada kondisi atmosferik untuk keperluan validasi model. Disamping penelitian eksperimental juga dilakukan pengembangan model matematik untuk proses absorpsi. Pemodelan alat absorpsi reaktif berdasarkan pada gambaran teori dari pasangan reaksi dan perpindahan massa di sistim fluida yang bersifat multikomponen. Sifat multikomponen dari fenomena ini mengarah ke perilaku proses yang kompleks karena adanya superposisi dari beberapa driving force difusi multikomponen dan interaksi kimia. Untuk alasan ini penggunaan persamaan Maxwell-Stefan adalah yang paling memadai untuk memberikan gambaran teori pada sistim absorpsi reaktif multikomponen dan selanjutnya digunakan untuk persamaan gabungan perpindahan massa dengan kinetika reaksi yang relevan. Fluk absorpsi masing-masing komponen Ni di film ditentukan dengan menggunakan model film dengan teori difusi multikomponen Maxwell-Stefan yang telah diselesaikan secara analitis oleh Kenig 2001. Pemodelan matematika dilakukan dengan membuat neraca massa dalam Packed Column. Neraca massa mikroskopis dibuat untuk setiap komponen dalam fase cair dan gas. Sebagai aplikasi dilakukan simulasi absorpsi reaktif gas asam dalam Packed Column. Validasi model dilakukan dengan membandingkan data hasil prediksi dengan data hasil eksperimen tekanan rendah dan data riil di salah satu indusatri pupuk di Indonesia tekanan tinggi. Hasil studi menunjukkan bahwa hasil simulasi rate based model menggunakan teori difusi Maxwell-Stefan dapat diterima. Dari kajian teoritis menggunakan pendekatan difusi Maxwell-Stefan dapat disimpulkan bahwa peningkatan konsentrasi CO2 yang mengakibatkan driving force sisi gas naik tidak signifikan mempengaruhi fluks CO2 karena tahanan sisi gas juga meningkat tetapi jika menggunakan pendekatan enhancement factor peningkatan konsentrasi CO2 secara signifikan mempengaruhi fluks CO2. Model difusi Maxwell-stefan dapat mengakses adanya titik optimum pada pengaruh temperatur. Hasil prediksi distribusi konsentrasi komponen dapat diketahui bahwa pada posisi atas kolom pengaruh tahanan sisi gas lebih dominan dibandingkan tahanan sisi liquida pada posisi bawah kolom terjadi phenomena yang berlawanan. Pengaruh variabel proses dan parameter operasi seperti laju aliran dan temperatur inlet larutan tekanan kolom dan jenis promotor terhadap kinerja absorpsi gas asam pada Packed Column telah dikaji yang hasilnya dibahas dalam laporan ini.


ABSTRACT

Absorption of gases in liquids accompanied by chemical reaction reactive absorption is a fundamental operation in a broad spectrum of chemical process technologies. In oil refineries flue and tail gases need to be purified to meet pollution standards in fertilizer and petrochemical plants acid gases have to be removed from the feed to ammonia synthesis plants and polymerization units to avoid catalyst poisoning. The absorption of carbon dioxide with alkanolamine or potassium carbonate solvent has gained widespread acceptance for the removal of CO2 and H2 from natural gas. However alkanolamine solution are prone to oxidative degradation at high temperature. The main advantages of potassium carbonate solution for CO2 removal are the high chemical solubility of CO2 in the carbonatebicarbonate system low solvent costs and the low energy requirement for solvent regeneration. The major challenge concerning absorption of CO2 into aqueous solution of potassium carbonate is a relatively slow rate of reaction in the liquid phase causing low mass transfer rates. It is often advantageous to add a promoter to increase the absorption rate. While piperazine is often used for this purpose. In this work we consider methyl-diethanolamine MDEA and boric acid as an alternative promoter. Experimental studies have been conducted to determine the reaction kinetics data of CO2 absorption with K2CO3 solvent and promoter MDEA or boric acid using WWC. Data were obtained over the temperature range of 303-323K and for 1-3 wt MDEA or boric acid. The addition of 1 2 and 3 wt MDEA or boric acid to 30 wt K2CO3 system results in a significant enhancement of CO2 absorption rates. Both of the promotor two kinetic models were proposed in this work. The first model based on second-order reaction rate constant measurement the second model based on pseudo first-order reaction rate constant measurement. The rate of absorption of CO2 in a solution of 30 wt K2CO3 with the promoter MDEA is greater than the rate of absorption of CO2 in 30wt K2CO3 solution with boric acid promoter. Research experiments have also been conducted to determine equilibria data of gas-liquid electrolyte system for CO2-MDEA-K2CO3- H2O. Effect of the addition of MDEA in a solution of K2CO3 can increase the CO2 loading and lowering the partial pressure of CO2. CO2 absorption rate has been measured using the Packed Column on atmospheric conditions for model validation. Beside experimental work this study developed mathematical model of the proposed process. Modeling of reactive absorption are based on the theoretical description of the reaction and mass transport in multi component systems. The multi component nature of these phenomena leads to complex process behavior due to the superposition of many driving forces multi component difusion chemical interactions etc. For this reason adequate theoretical description of multi component reactive systems calls for the application of the Maxwell-Stefan equations and further for the use of coupled mass transfer equations together with the relevant reaction kinetics. On this basis a two-phase gas-liquid reactive system is considered and a general static model is developed for its design. Absorption flux of each component Ni were determined using steady-state film model film with Maxwell-Stefan multi component difusion theory which has been solved analytically by Kenig 2001. Mathematical modeling is done by making a mass balance on a Packed column. Microscopic mass balance is performed for each component in the liquid and gaseous phase. As an application the reactive absorption of sour gases with Packed columns is simulated. For the validation of the model experiments were carried out. The study showed that the rate-based model simulation results using Maxwell-Stefan difusion theory are in a good agreement with the experimental data. From the theoretical study using Maxwell-Stefan diffusion approach it can be concluded that increasing CO2 concentration so increasing the gas side driving force does not significantly affect the calculated CO2 absorption flux because the gas side resistance also increases. However if enhancement factor approach is used increasing CO2 concentration does significantly affect the calculated CO2 absorption flux. The predicted concentration distribution in the column shows that on the top column position the effect of gas side resistance is more dominant than the liquid side resistance however in the bottom column position opposite phenomena occured. The effects of process variables and operating parameters on the performance of absorber were investigated.The effect of process variables and operating parameters such the flow rate of solution inlet temperature of solution the pressure of Packed column and type of promoter on the performance of a Packed column absorber have been examined which has been discussed in this report.



KeywordsAbsorpsi Reaktif; Enhancement Factor; Kalium Karbonat; Maxwell Stefan; Multikomponen; Promotor; Model Rate-Based
 
Subject:  Absorption
Contributor
  1. Prof. DR. Ir. Ali Altway, MS
  2. Prof. DR.Ir. Nonot Soewarno, M.Eng.
Date Create: 27/02/2012
Type: Text
Format: pdf
Language: Indonesian
Identifier: ITS-PhD-23004120000049
Collection ID: 23004120000049
Call Number: RDK 660.284 23 Pud m


Source
PhD Thesis of Chemical Engineering, RDK 660.284 23 Pud m, 2012

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Copyright @2012 by ITS Library. This publication is protected by copyright and per obtained from the ITS Library prior to any prohibited reproduction, storage in a re transmission in any form or by any means, electronic, mechanical, photocopying, reco For information regarding permission(s), write to ITS Library




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  1.  ITS-PhD-21361-2308301004-Abstract_id.pdf - 173 KB
  2.  ITS-PhD-21361-2308301004-Abstract_en.pdf - 164 KB
  3.  ITS-PhD-21361-2308301004-Conclusion.pdf - 186 KB




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