kolom distilasi

LEMBAR PERHITUNGANNama AlatDistillation CoulumnKodeFungsiMemurnikan Metanol hingga 99,85%D-401

DibuatDiperiksaDisetujui

Fungsi : Memurnikan Metanol hingga 99,85%Jenis : Sieve trayBentuk: Silinder vertikal dengan alas dan tutup torispericalBahan konstruksi : Carbon Steel SA-283 Grade CJumlah : 1 unitDataLight key (LK): MetanolHeavy key (HK): Air

Tabel 1. Thermodinamic PropertiesPers Antoine {In P = A - B/(T + C)}

KomponenABCMetanol18,58573626,55-34,29Air18,30363816,44-46,13

feed, F =173560,12kg/jamkomponen%beratkg/jamCH3OH0,15107099526219,9Air0,848929005147340,2total1173560,1

P= 3,74 atm =3,79 bar =2842,734 mmHgT= 391 oK

Kondisi operasi bagian top :Destilat, Tdew = 64,94oC = 338,09 K, P= 1 atm

KomponenF(kg/jam)BMN (kmol/jam)Pi (mmHg)Kixi = ki/khkCH3OH26180,5732818,1428172771,553281,00286640,99854,123063206Air221,010331812,27835167187,131080,24323330,00151total26401,58

Tabel 2. Komposisi bahan alur distilat

Kondisi operasi bagian bottom :Komponen

F (kg/jam)BMN (kmol/jam)Pi (mmhg)KiXib = ki/khkCH3OH39,32985321,2290578121523,42431,00225280,00153,756612208Air147119,21188173,289426405,531420,2667970,99851total147158,54Bottom, Tbubl = 83,3 oC = 356,45 K, P= 2 barTabel 3. Komposisi bahan alur bottomD = 830,4211689 kmol/jam W = 8174,518484 kmol/jam XLF = 0,15XHF = 0,84XLW = 0,0015XHW = 0,9985XLD = 0,9985XHD = 0,0015

Mencari Jumlah Tray Minimum dengan Menggunakan Metode Fenske

3,829

9,84 10 tray

Menentukan Rmq = 1 , = 1,2

T rata = 347,27 oK = 74,12 oC Tabel 4. Perhitungan RmKomponenXidKii.X/-CH3OH0,99851095,0309223,9284541,437649782Air0,0015278,74347211-0,0075Total14,928454Rm + 1=1,4301498Rm =0,4301498R = 0,6452247(R = 1,5*Rm)

Mencari Jumlah Tray Teoritis

[Pers.15-4, Peters, 2003]

N = 20,53 21 plateMaka, jumlah tray teoritis: 21 Tray

Effisiensi Tray (Eo): 80%(hal 429, Wallas, 1990)Maka, jumlah tray aktual: 26 plate

Penentuan Umpan Masuk Dengan Metode Kirkbride

Log Nr/Ns = 0,308Nr/Ns = 2,033

Nr = 2,033*NsNr + Ns = 2,033*Ns + NsNr + Ns = 25,66Ns = 8,4Nr = 17,2 Jadi, umpan masuk pada tray ke-17 dari atas.

Perhitungan diameter dan tinggi menaraBagian Top menaraR = Lo/D

Lo = R.DV = Lo + DTabel 5. Perhitungan laju alir gasKomponenF (kg/jam)BMxMr avgMetanol 26180,57320,998531,952Air221,01033180,00150,027Lo =26401,5831,979

Jadi, laju alir gas (V): V = 17034,95112 + 26401,58 = 43436,5316 kg/jam

Densitas gas ,

=1,166 kg/m3Bagian Bottom menaraV2 = V1 + (1- q)F

Maka V2 = V1 = 147158,54 kg/jam

Maka, laju alir cairan, L :L = Lo + qFL = 190595,1kg/jam

Densitas cairan :Tabel 6. Thermodinamic propertiesKomponenABnTcDensitas (Kg/m3)xixi.densitasDEG0,271970,271920,2331512,6729,81150,00151,09471724EG0,34710,2740,28571647,1972,2370,9985970,778662971,873379

Maka, densitas cairan = 971,873379 kg/m3

Laju volumetrik gas, Qv :

Qv = 37221,334 m3/jam = 10,33925946 m3/s

Laju volumetrik cairan, Ql :

QL = 0,054475 m3/s

FLV = 0,15204 [Pers 11.82; Coulson. Vol 6, 1999]

Sehingga diperoleh, K1 dan dipilih plate spacing 0,45 m :K1 =0,041 [Fig11.27; Coulson, Vol.6, 1999]

Surface Tension (): 0,04 N/m

Korelasi K1 :Kcor = . K1

Kcor = 0,079260186

Kecepatan alir maksimum , UF :UF = K1. [Pers 11.81 ; Coulson, Vol.6, 1999]UF = 1,99 m/s

Kecepatan flooding = 80 %UF = 1,592 m/sLuas area yang dibutuhkan, An:

An = 6,494 m2

Downcomer area = 12% ACross-sectional area column, Ac

Ac = 7,379 m2Diameter Menara, ID :

ID = 3,064 m

sehingga diameter kolom destilasi =ID = 3,064 m= 120,65 inr = 1,532 m = 60,32 in

Perhitungan tebal shell, tutup dan tinggi menaraTebal shell,ts :Bahan Carbon steel SA-283 grade C P = 115,99 psiaP design (20% kelong) = 139,198 psiaE = 0,8C = 0,125 inf = 12650 psia

1959)

ts = 0,962 in = 0,0244 m Tebal tutup ,th :

OD = ID + 2.tsOD = 122,582in Th = 1,619 in = 0,0411 m

Provisional Plate designDiameter kolom, Dc= 3,064 m

Area kolom, Ac = 7,379 m2Area downcomer, Ad = 0,885 m2Area net, An = 6,494 m2Area aktif, Aa = 5,609 m2hole area, Ah ambil 10 % Aa sebagai trial= 0,5608 m2Ad/Ac x 100% = 12weir lenght, lw (Gambar 11.31 Coulson) = 2,299 m

asumsi :weir height, hw = 0,05 mhole diameter, dh = 0,005 mplate thickness = 0,005 m

Check weepingMax liq rate = 52,943075 kg/s

turn-down = 70 % maka, Min liq rate = 0,7 . 52,943075 = 37,060153 kg/s

Max hw : hw = = 61,88 mm= 0,06188 m

Min hw =

hw =

= 48,78 mm= 0,04878 m

Total laju = 110,666 mmDari gambar 11.30 Couldson didapat K2 =31,2

7,724 m/s

Kecepatan uap minimum aktual =13,772Kesimpulan tidak terjadi weeping karena kec uap min aktual > uh (min)

Kecepatan uap max melewati lubang:

uh =

uh = 18,43404 m/sPressure dropTebal plate/ diameter hole = 1

= 1

Dari gambar 11.34 Coulson, didapat Co =0,84

hd = 29,492 mm

Residual head, hr :

hr = 12,862 mmtotal plate pressure drop,ht = hd + hr + (hw + how) = 153,020002 mm

Downcomer liq back - uphap = hw 10

= 51,881 mm

area under upron, Aap = hap.lw = 131,9643 m2

hdk = 448,935 mm

Downcomer back - uphb = ht + hdc + (hw + how)

= 712,6218 mm Tray spacing dapat diterima karena hb < (tray spacing + panjang weir)check residence time, tr :

tr = 3,22 s

Residence time bisa diterima karena direkomendasikan > 3 detik (Coulson, vol 6, 1999)

Check entrainmentDari Gambar 11.29, Coulson vol 6 (1999), didapat nilai = 0,02



Entrainment tidak bisa diterima karena direkomendasikan < 0,1 detik (Couldson, vol 6, 1999)

Perforated arealw/dc= 0,75



Dari gambar 11.32 Coulson didapat nilai c = 97oAngle subtended at plate edge by unperforated strips = 180 97 = 83oMean length, unperforated edge strips = (Dc-hw) ((180-c)/180) = 4,368 mArea of unperforated edge strips = hw x mean length = 0,21845 m2Mean length of calming zone = (Dc-hw) x sin (c/2) = -2,9578 mArea of calming zone = -0,29578 m2

Total area for perforations, Ap = 5,686m2Ah / Ap = 0,09864Dari Gambar 11.33, Coulson vol 6 (1999), didapat nilai lp/dh =3



Nilai lp/dh bisa diterima karena direkomendasikan antara 2,5 - 4 (Coulson, vol 6, 1999)

Jumlah hole

area satu hole = 0,0000785 m2jumlah hole = 7144,9513 buahPerhitungan tinggi tutup :OA = th + b + sfBerdasarkan Tabel 5.6 dan 5.8, Brownell and Young [1959] untuk OD = 122,582 in dan ID = 120,659 diperoleh:

icr = 6 inrc = 180Sf = 2 in

AB =543296 BC =174 AC = 165,3006

B = rc - AcB = 14,699

tinggi tutup:(jenis torispherical)OA = Sf + B = 16,699 in = 0,424 m

Tinggi kolom destilasiN = 26 buah

plate spacing = 0,45 mtebal plate = 0,005 mOA = 0,424 mTinggi kolom = (N - 1)*plate spacing + (N*tebal plate) + (2*OA)= 12,077 m

kolom distilasi

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