5. absorption dehydration
TRANSCRIPT
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Dehidrasi GlikolDehidrasiDehidrasi GlikolGlikol
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Syarat cairan yangdapat menyerap air
Sangat higroskopis Tidak membentuk padatan pada
konsentrasi tinggi
Tidak korosif Tidak mengendap bila meyerap gas
Mudah diregenerasi
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Syarat cairan yangdapat menyerap air
Mudah dipisahkan Tidak larut dalam HC
Stabil dengan adanya sulfur atau CO2
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Syarat cairan yangdapat menyerap air
Yang memenuhi syarat Glikol DEG TEG
TREG Yang paling populer TEG
TREG memiliki suhu absorpsi50o
C
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Unit dehidrasi glikol Gambar 18.1 Unit regenerasi dirancang pada tekanan
atm Initial thermal decomposition
Glikol Suhu EG 165oC, 329oF DEG 164oC, 328oF TEG 206oC, 404oF
TREG 238oC, 460oF
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Unit dehidrasi glikol
The glycol dehydration processesremoves water vapor from naturalgas.
Removing water vapor preventshydrate formation and corrosion, andmaximizes pipeline efficiency.
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Unit dehidrasi glikol Wet gas enters the tower at the bottom. Dry glycol flows down the tower from the
top, from tray to tray, or through packingmaterial.
NATCO's special bubble cap configurationmaximizes gas/glycol contact, removingwater to levels below 5 lbs/MMscf.
Systems can be designed to achieve levels
down to 1lb/MMscf.
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Unit dehidrasi glikol
The dehydrated gas leaves the towerat the top and returns to the pipelineor goes to other processing units.
The waterrich glycol leaves thetower at the bottom, and goes to thereconcentration system.
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Unit dehidrasi glikol
In the reconcentration system, thewet glycol is filtered of impuritiesand heated to 400F.
Water escapes as steam, and thepurified glycol returns to the towerwhere it contacts wet gas again.
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Contactor featuresavailable Diameters from 8-5/8 in. to 15 ft. Design pressures from 230 to 2,160 psig Flowrate capacities from 100 to 200,000
Mscfd ASME Code, National Board, or British
Standard stamped Corrosion allowance with ASME code
inspection openings
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Contactor featuresavailable
Internal or external glycol-gas heatexchangers or air coolers Integral inlet scrubber
3 to 15 trays or packed columns 18, 24 or 30 inch tray spacing Carbon steel or stainless steel trays
and bubble caps
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Contactor featuresavailable
Tray drains Tray inspection openings
External or inter-tray manways
Gas piping and valves
Instrumentation and alarm systems
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Contactor featuresavailable
Special coatings Safety caged ladders and platforms
Construction materials are carbon
steel, 304 or 316-L stainless steel,316-L stainless steel clad, or 316-Lstainless steel overlay
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Regenerator featuresavailable Glycol purity to 99.0% with standard type
and to 99.97% with stripping gas type Heat duty from 75,000 to 8,000,000
Btu/h
Heat sources can be direct fired, steam,hot oil, electric, or natural gas
ASME Code or TEMA C or R design heat
exchanger
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Regenerator featuresavailable
ASME Code or National BoardStamped
Pulsation dampeners
Flame arrestors Internal or external glycol-glycol
heat exchangers or air coolers
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Regenerator featuresavailable Glycol flash drums or hydrocarbon
skimmers Glycol sock or charcoal filters with
standby
Glycol pumps can be electric, gas or glycolpowered, with standby, automaticswitching.
Automatic reflux/overhead temperature
control
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Regenerator featuresavailable
Temperature or filter differentialpressure recorders Instrumentation and alarm systems
High level, low level, and hightemperature alarms Automatic shutdown panels
Automatic pilot re-light systems
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Regenerator featuresavailable Moisture analyser Construction materials are carbon steel,
304 or 316-L stainless steel, 316-Lstainless steel clad, or 316-L stainless
steel overlay. Special coatings Galvanized skids, ladders, and access
platforms
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Regenerator featuresavailable Galvanized skids, ladders, and access
platforms
Fiberglass cold-weather housings
Modular design Stripping gas recovery system
Combustion Air Controller or Firetube
Turbulator for increased fuel efficiency
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Regenerator featuresavailable Galvanized skids, ladders, and access
platforms
Fiberglass cold-weather housings
Modular design Stripping gas recovery system
Combustion Air Controller or Firetube
Turbulator for increased fuel efficiency
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wv
w yPPx
Xw: fraksi mol air dalam glikol
P : tekanan sistem
Pv: tekanan uap air pada suhu reboiler
Yw: fraksi mol air dalam uap reboiler
Gambar 18.2 digunakan untuk gas dengankandungan S dan CO2 tinggi
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Basic process designfactor
Konsentrasi TEG minimum dalam leansolution yang masuk ke bagian atasabsorber yang diperlukan
Laju sirkulasi TEG yang diperlukan Jumlah kontak dalam absoeber yang
diperlukan
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Konsentrasi Lean TEGminimum
Digunakan Gambar 18.3 f(Tg-in, Tdew-eq)
Contoh: berapa suhu Tdew-eq air jika
suhu gas masuk 40oC dan lean glikolmengandung 99.5% berat TEG
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Konsentrasi Lean TEGminimum
Actual water dew point umumnya 5.5-8.5oC > Tdew-eq Pendekatan ini dapat digunakan untuk
menentukan konsentrasi lean glikolminimum
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Konsentrasi Lean TEGminimum Prosedur:
Tentukan suhu dew point air keluarandari kontrak penjualan atau suhuminimum system
Kurangi langkah 1 untuk menentukanTdew-eq actual
Gunakan Gambar 18.3 untuk menentukan
konsentrasi minimum lean TEG
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Konsentrasi Lean TEGminimum Contoh:
Kontrak penjualan gas mempunyaispesifikasi kandungan air100kg/106stdm3 gas pada tekanan 6.9MPa. Suhu inlet gas adalah 40oC.Berapakah konsentrasi minimum leanTEG yang diperlukan.
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Konsentrasi Lean TEGminimum Prosedur:
Suhu dew point air (Gb App. 18A)=f(100,6.9)
Tdew-eq= T1 8o
C Gambar 18.3 untuk menentukankonsentrasi minimum lean TEG = f(40,
Tdew-eq)
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Regenerasi TEG Konsentrasi lean TEG
tertentu dihasilkandalam reboiler danregenerator denganmengendalikan suhu reboiler
tekanan gas
stripping gas yangdigunakan
wv
w yP
Px
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Regenerasi TEG Jika digunakan stripping gas, konsentrasi rich
TEG yang meninggalkan absorber diperoleh darineraca massa di sekitar absorber
eanTEGwtwaterinlorbedwtwaterabswtleanTEG
wtleanTEGrichTEGwt
100%
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Regenerasi TEG Gb 18.4 dapat digunakan untuk memprediksi
kerja regenerator Jika kandungan air dalam lean TEG kecil maka
persamaan terdahulu menjadi
m
LeanTEGRichTEG
/1
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Regenerasi TEG Rich TEG = wt% TEG in Rich TEG solution
Lean TEG = wt% TEG in Lean TEG solution = densitas cairan = 1.12 kg/L (9.3lb/USgal)
m = Lean TEG rate, L/kg (USgal/lb)
m
LeanTEGRichTEG
/1
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Regenerasi TEG Konsentrasi Lean TEG min pd Gb 18.4
T (204oC) = 98.7 wt%
T (193oC) = 98.4 wt%
T (182oC) = 98.1 wt%
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Regenerasi TEG Prosedur umum penggunaan Gb 18.4
Tekanan atm tanpa stripping gas
Tekanan atm dengan stripping gas
Tekanan Vakum dengan stripping gas
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Regenerasi TEG Contoh
96.8 wt% Rich TEG memasukiregenerator menggunakan 0.03m3stripping gas/L larutan glikol.Berapakah konsentrasi Lean TEG jikasuhu regenerator 204oC pada tekanan 1atm dan 500 mmHg
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Regenerasi TEG Lean TEG (1 atm) =
Lean TEG (500 mmHg) =
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Ci l ti R t
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Circulation Rate Absorber Contacts
Untu laju sirkulasi tertentu maka
diperlukan jumlah kontak absorber yangtertentu pula
11
01
11
1
N
N
N
A
AA
yy
yyEa
N
Ci l ti R t
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Circulation Rate Absorber Contacts
yN+1: fraksi mol air dalam inlet gas
y1: fraksi mol air dalam outlet gas y0: fraksi mol air dalam outlet gas bila berada
dalam kesetimbangan dengan Lean TEG yangmasuk (
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Circulation Rate Absorber Contacts
A: faktor absorbsi = L/KV L: laju sirkulasi TEG, mol/waktu V: laju alir gas, mol/waktu K: konstanta kesetimbangan utk air antara air dlm gas
dan air dlm larutan TEG-air, y=Kx N: jumlah plat teoritis dlm absorber
11
01
11
1
N
N
N
A
AA
yy
yyEa
N
Ci l ti R t
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Circulation Rate Absorber Contacts
Fraksi mol air, yw, berhubungan dengan W yaitu
massa air per std volume gas yaitu: Yw = 1.33x10-6W dimana W dalam kg/106std m3
Yw = 2.11x10-5W dimana W dalam lb/MMscf maka
01
11
01
11
WW
WW
yy
yy
N
N
N
N
Ci cul ti n R t
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Circulation Rate Absorber Contacts
Persamaan sebelumnya dapat ditulis
menjadi persamaan di bawah yangplotnya ada di Gb. 18.5.
01
11
01
11
WW
WW
yy
yyE
N
N
N
Na
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Circulation Rate
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Circulation Rate Absorber Contacts
Perhitungan laju Lean TEG utkeffisiensi absorbsi dan N tertentu
1. Hitung y0 (W0)
2. Tentukan effisiensi absorbsi3. Tentukan A dari persamaan atauGb.18.5
4. Hitung L0, laju sirkulasi Lean TEG
Circulation Rate
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Circulation Rate Absorber Contacts
Perhitungan N utk laju Lean TEG dan
effisiensi absorbsi tertentu1. Hitung y0 (W0)
2. Tentukan effisiensi absorbsi
3. Tentukan A dari persamaan atau Gb.18.54. Tentukan N dari persamaan atau Gb. 18.5
5. Overall efisiensi 25-40 %
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Circulation Rate
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Circulation Rate Absorber Contacts
y0 = Kx0 dan W0= (W)()(x0) (18.7)
Y0: fraksi mol air dalam lean TEG x0 dpt dihitung menggunakan pers. (18.8)
melalui xgl, yaitu wt% TEG yang masukabsorber yang tidak boleh lebih kecil dari
nilai minimum pd Gb. 18.3.
150/18/100
18/100
0
glgl
gl
xx
xx
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Circulation Rate
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Circulation Rate Absorber Contacts
Jika menggunakan metode Kremser-Brown,
V dan L harus dalam satuan molar, shgdiperlukan utk mengestimasi MW
Berat molekul larutan air TEG
MW = 18x0 + 150 (1-x0)
150/18/100
18/100
0
glgl
gl
xx
xx
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Circulation Rate
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Circulation Rate Absorber Contacts
Contoh:
Hitunglah laju sirkulasi 98.7 wt% Lean TEGyang diperlukan utk mengeringkan 106 stdm3/d gas pada 7 MPa dan 40oC dalam
absorber 4 tray (1 tray teoritis), shg gaskeluarannya hanya mengandung air 117 kg/106 std m3 gas. Kandungan air pada inlet
gas adalah 1100 kg/ 106 std m3gas.
Circulation Rate
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irculation RateAbsorber Contacts
Xgl = 98.7%
W= 1100 kg/ 106 std m3gas
W1= 117 kg/ 106 std m3 gas
N = 1
Circulation Rate
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Absorber Contacts
1. Hitung x0menggunakanpersamaan 18.8 150/18/100
18/100
0
glgl
gl
xx
xx
Circulation Rate
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Absorber Contacts
1. Tentukanmenggunakan Gb.18.6 = f(xgl)
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Circulation Rate
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Absorber Contacts1. Hitung W0
menggunakanpers. 18.7 W0= (W)()(x0)
2. Hitung effisiensiabsorbsi Eamenggunakan
pers. 18.5.
01
11
01
11
WW
WW
yy
yyE
N
N
N
Na
Circulation Rate
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Absorber Contacts1. Tentukan A menggunakan Gb. 18.5 =
f(N,Ea)
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Circulation Rate
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Absorber Contacts Hitung K dari pers 18.6
K = (yw)()=(A)(W)() Hitung Lo = (A)(K)(VN+1) Hitung Mol gas/Jam
Hitung Mol TEG/jam Hitung MW Lean TEG menggunakan pers.
18.9
MW = 18x0 + 150 (1-x0)
Circulation Rate
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Absorber Contacts Hitung laju sirkulasi TEG/jam
WTEG = mol TEG/jam x MW VTEG = WTEG/TEG H2O absorbed/hr = (W-W1)/24
Circulation rate =VTEG/ H2O absorbed/hr
(liter/kg H2O absorbed)
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