Desain Kolom Pemisah Distilasi Ada beberapa macam pemilihan kolom pemisah distilasi yaitu :

1. Packed Tower

Sebuah kolom yang dilengkapi packing utk memperluas bidang kontak dan membuat turbulensi shg kontak lebih sempurna. Prinsip kerjanya zat yg berbeda fase mengalir berlawanan arah yg dpt menyebabkan komponen kimia ditransfer dari satu phase ke phase lain. Zat berfase cair mengalir dari atas dan gas dari bawah sehingga terjadi kontak antara keduanya.

Dipilih packed tower karena Utk liquid korosif, karena alat lebih murah Membutuhkan tahanan liquid yg rendah karena densitasnya yg besar Memberikan pressure drop per tahap kesetimbangan yg rendah Utk diameter kolom yg kecil

Packed TowerSyarat packing yang bagus adalah :

Bulk density kecil (tdk terlalu membebani kolom) Luas yg terbasahi besar Volume rongga besar (mengurangi pressure drop) Sifat pembasahan baik Tahan korosi Memiliki struktur yg kuat utk menahan beban tumpukan Murah

Macam - macam bentuk packing :

Rasching ring

Berl saddle

Pall ring sederhana : rasching ring, harga lebih murah tapi efisiensi lebih rendah,

sering chanelling sedang : pall ring, batas flooding tinggi dan distribusi liquid baik tinggi : berl saddle, mahal, bed seragam, batas flooding tinggi dan

pressure drop rendah

Pemilihan bahan packing : Keramik, utk liquid yg bersifat korosif Plastik, cocok utk temperatur sedang dan tidak cocok utk pelarut organik Logam, utk kondisi operasi yg tdk stabil

"There are several types selection of distillation separating column such as :

       1. Packed Tower A column is completed of packing to enlarge contact area and creating turbulence so more perfect contacting. The working principle is different phase substance flow counter current, so chemical component transferred from one phase to another phase . Liquid phase flow from above and gas from bottom so both is contact.

Selected packed tower because For corrosive liquid, because cheaper instrument Requires low liquid resistance because large density Provide low pressure drop per equilibrium stage For small column diameter

The requirement of quality packing are : Small bulk density (not loading column) Large the wetted area Large the hole volume (reducing pressure drop) Good wetting properties Corrosion resistant Have a strong structure to hold the piles load Cheap

Selection of packing material : Ceramic, for corrosive liquid Plastic, suitable for moderate temperature and not suitable for organic

solvent Metal, for unstable operating condition"

      2. Tray / Plate ColumnBentuk sama dengan packed column tapi tidak mempunyai packing, sebagai gantinya ada plate-plate yang berfungsi memperbesar kontak antar komponen shg bisa dipisahkan menurut rapat jenisnya.

Jumlah tahapan plate disusun berdasarkan :

Tray Tower Tingginya kesulitan pemisahan zat yg akan dipisahkan Perhitungan neraca massa dan kesetimbangan

Dipilih jenis ini tdk packed tower karena : Bisa menangani laju alir liquid dan gas yang besar Pembersihan mudah karena bisa dipasang manhole

Lebih mudah utk pengambilan produk melalui samping Desain plate lebih terjamin efisiensi kerjanya

      "2. Tray / Plate ColumnSame shape with packed column but haven't packing, for substitute there are plates have function enlarge contact betweeen component so can be separated by density.

The number of plate stage formed according to : Height of difficult separation of substances will be separated Calculatton of mass balance and equilibrium

Selected this type not packed tower because : Can handle large liquid and gas flow rate Easy maintenance because can be installed manhole Easier to taking the product through side stream Plate design more secure working efficient"

      2. Bubble Cap

Spesifikasinya adalah :

Kapasitas sedang sampai tinggi Efisiensi sedang sampai tinggi Biaya instalasi dan perawatan lebih mahal Laju alir rendah karena pressure drop tinggi

Bubble Cap Tray Korosi tinggi 

     "2. Bubble CapThe specifications are :

The capacity is moderat to high  Efficiency is moderat to high Installation cost and maintenance are more expensive Low flow rate due to high pressure drop

High corrosion"

     3. Sieve TraySpesifikasinya adalah :

Kapasitas tinggi Efisiensi tinggi Pressure drop sedang Biaya instalasi dan perawatan murah Korosi rendah

        "3. Sieve TrayThe specifications are :

High capacity High efficiency Moderate pressure drop Cheap installation and maintenance cost Low corrosion"

Istilah-istilah yg biasanya muncul adalah :

Downcomer : lubang tempat masuknya aliran dari atas (liquid) ke plate bawah (kita memandang plate ini sbg acuan)

Downflow : lubang tempat keluaran liquid dari plate (kita memandang sbg acuan) ke plate di bawahnya

Entrainment : peristiwa liquid terangkut ke plate atasnya karena dorongan gas dari bawah yg berlebihan, disebabkan laju alir gas terlalu besar

Flooding : menggenangnya liquid di plate karena kiriman liquid yg berlebihan dr plate atasnya, bisa disebabkan karena adanya entrainment, shg plate atas menerima kelebihan liquid

Weeping : liquid yg ada pada plate jatuh bebas ke plate bawahnya karena tekanan gas dari bawah kurang, disebabkan karena laju alir gas kecil.

Cap : penghalang / pengkontak antara liquid dan uap yang dipasang di setiap tray, bentuk seperti topi yg pinggirnya ada slot utk mengatur besar kecilnya gas yg keluar keatas

Tray / Plate : lapisan atau level disetiap kolom, biasanya terbuat dari besi baja yg kuat menahan beban liquid atau cap

Slot : tempat bukaan pada cap yg mempunyai macam-macam bentuk (trapesium, persegi, segitiga dll) yg berfungsi mengatur bukaan gas yg keluar ke atas shg liquid dan gas berkontak secara normal

Enriching : bagian plate yg berada diatas tempat masukan feed Exhausting / Stripping : bagian plate yg berada dibawah tempat masukan

feed Baffle : penghalang yg berada di tengah-tengah tray utk membuat aliran

lebih lama berada di tray (penerapan hanya di reverse flow) Weir : penghalang yg dipasang di pinggir dari downflow utk membuat

agar volume liquid yg tertampung di tray banyak, sehingga efektif terjadinya kontak antara liquid dan gas

Cross Flow : aliran liquid datang dari atas (downcomer) lalu mengalir di sepanjang tray dan mengalir ke plate bawahnya di downflow. Disebut cross flow karena letak downcomer dan downflow di sisi berseberangan. Jarak yg dilewati liquid panjang shg efisiensi tinggi

Reverse Flow :  aliran liquid datang dari atas (downcomer) lalu mengalir di sepanjang tray dan berbelok ke bagian tray sebelahnya karena adanya baffle lalu mengalir ke plate bawahnya di downflow. Disebut reverse flow karena letak downcomer dan downflow di sisi yg sama. Dapat digunakan utk menampung cap lebih banyak, L/V rendah, luas downcomer kecil

Double Pass :  aliran liquid datang dari atas dari 2 downcomer lalu mengumpul di tengah-tengah plate bawahnya dan aliran pecah menjadi 2 di 2 downfow (terletak di sisi kiri dan kanan). Digunakan utk beban liquid yg besar, L/V tinggi

"Means commonly appear such as : Downcomer : hole as place input flow from above (liquid) to under plate

(we know this as a reference) Downflow : hole as place output liquid from plate ( we know this as a

reference) to the below plate Entrainment : even liquid carry up to above plate because excess gas

pressure from below, caused by gas flow rate is too large  Flooding : excess liquid in plate because sending of excess liquid from

above plate, can due to entrainment so above plate give excess liquid Weeping : liquid in the plate free fall to below plate due to less gas

pressure from under, caused by small gas flow rate

Cap : barrier / contacter between liquid and gas in every plate, form like a cap which edge there is slot to manage large small out gas to above

Tray / Plate : layers or levels each column, commonly makes from stainless steel which strong to hold liquid load or cap

Slot : opening at cap have varieties shape (trapezoidal, square, triangle etc) function to manage out gas throttle above so liquid and gas normal contacted

Enriching : part of plate have place above from feed hole Exhausting / Stripping :  part of plate have place under from feed hole  Baffle : barrier in the center tray to make flow longer in the tray

(applicated only in reverse flow) Weir : barrier installed in edge of downflow to make much liquid volume

contained in the tray, so that effective contacted between liquid and gas Cross Flow : liquid flow coming from above (downcomer) then flow in

along the tray and flow to the under plate pass downflow. Called cross flow because position of downcomer and downflow is opposite. The distance liquid passing is long so high efficiency

Reverse Flow : liquid flow coming from above (downcomer) then flow along the plate and turn to side tray due to baffle then flow to under plate pass downflow. Called reverse flow because position of downcomer and downflow is same. Can be used to collect more cap, very low L/V and small downcomer area 

Double Pass : liquid flow coming from 2 downcomer then collect in the under middle plate and flow split to 2 and flow in 2 downflow (position in the right and left of tray). Can be used to large liquid load and high L/V"