PENGUKURAN KINERJA DAN PENDETEKSIAN TERJADINYA FLOODING PADA ABSORBER UNGGUN ISIAN

Abstract

Packed bed absorber is very greatly used to treat the dangerous waste gases (NO3, CO2, SO3, NH3), halogen acid gases (NCI, HF, HBO, flue gas (Cl2, Br2, MTBE), and solid particulate (Pb, S), etc. The flow maldistribution and flooding is frequently occurred in the operation of packed bed absorber. These phenomena is very complicated and damage, because can decrease the performance of absorber, in the other hand is percentage of gas absorption. Therefore, in this research will to find the limitation of parameter of condition operations and design absorher to know how the flow maldistribution and flooding is occurred. The firstly of this research is design of instruments in Process Technology Laboratory of Chemical Engineering Department. Mixture of carbon dioxide gas in air is focus of this research, which absorb with sodium hydroxide liquid. The amount of absorbed carbon dioxide is analyzed using acid titration method. In addition, the dates are used to calculate the mass transport coefficient of gas to liquid of mass conservation model. Runge-kutta and golden section is numerical method to solve the mass conservation model. The performance of absorber is tested in variation of conditioning operation; gas flow rate (liter/sec) = 0.2 —1.5; flow rate of liquid (liter/sec) = 0.02 — 0.08; temperature of liquid (°C) = 30 — 60; concentration of liquid (M) = 1 — 3. The results are shown that flooding is occurred if the measurement of pressure drop is fluctuates. Some of liquid carry over on gases stream up to top of absorber and flood the top section of absorber. Beside that, the flow maldistribution is occurred which liquid stream from the top section is majority near with wall of absorber. The increasing of flow rate, temperature, and concentration of liquid will be raising the mass transport coefficient of gas to liquid. The value of the mass transport coefficient of gas to liquid is 0.02 — 0.14 molI(cc.atm.hr). This research needs to develop using pressure drop instrument, which connected with computer. The model must to develop with combined the model of mass conservation, energy conservation, and momentum conservation Absorber unggun isian (packing) merupakan alat proses yang paling banyak digunakan untuk mengolah gas-gas buang yang berbahaya seperti NO„ CO2, SO„, NH3, gas asam-asam halogen HCI, HP, HBr, gas-gas lepas Cle, Br2, MTBE, dan partikulat-partikulat padatan Pb, S, dlsb. Dalam pengoperasinnya seringkali ditemui gejala distribusi aliran tidak seragam (flow maldistribution) dan flooding (=banjir). Kedua fenomena ini sangat memgikan karena dapat menurunlcan kinerja absorber yakni tingkat esifisiensi pemisahannya. Sehingga perlu dilakukan penelitian untuk mencari batasan-batasan parameter-parameter operasi dan perancangan absorber yang pada akhimya kinerja absorber bisa optimal, temiasuk dicari metoda untuk mendeteksi tetjadinyaflooding. Penelitian dilakukan di Laboratorium Teknologi Proses Jurusan Teknik Kitnia Fakultas Teknik, dengan terlebih dahulu merancang alat. Gas buang yang diteliti adalah gas karbon dioksida dan dicampur dengan udara. Sebagai absorben digunakan larutan NaOH. Jumlah gas CO2 terabsorbsi yang dianafisa menggunakan metoda acidi-alkalimetri. Selanjutnya data-data ini digunakan untuk menghitung harga koefisien perpindahan massa gas ke cairan (kg.) menggunakan model yang telah diturunIcan dengan metoda numerik runge kutta orde 4 untuk integrasi dan metoda optimasi golden section. Penelitian kinerja diuji dengan merubah variabel-variabel proses seperti; laju alir gas (1t/det) = 0,2 —1,5; laju alir NaOH (liter/detik) = 0,02 — 0,08; temperatur penyerap (DC) = 30 — 60; konsentrasi NaOH (M) = I — 3. Hasil penelitian menunjukkan bahwa flooding (pembanjiran) terjadi jika beds tekan yang terukur kondisinya berfluktuatif. Fenotnena ini dapat teramati secara langsung dimana sebagian cairan mulai terikut oleh aliran gas sehingga terbawa Ice atas dan akbimya membanjiri bagian atas absorber. Selain itu, fenomena distribusi aliran penyerap yang tidak merata (flow maldisiribution) juga teramatiKetidak¬seragaman ini terjadi balk ke arah aksial maupun ke arah radial. Kebanyakan aliran cairan penyerap mengalir melalui bagian yang mendelcati dinding absorber