stabilizer design(part 2)

Composition of feed, top and bottom and relative volatilities are:

The key components selected are n-C4 and i-C5 as light and heavy key respctively.

Components Xf Xd Xb K-Values

H2 0.0953 0.5399 0 42.301999852CH4 0.0235 0.1334 0 14.6248911009C2H6 0.0209 0.1148 0.0008 5.2478040536C3H8 0.0375 0.114 0.0212 2.5630552627i-C4 0.031 0.0514 0.0267 1.4622811889n-C4 0.0179 0.0239 0.0166 1.241435261i-C5 0.2959 0.0214 0.3547 0.6927922272n-C5 0.0992 0.0011 0.1202 0.60893354975N5 0.0221 0.1 0.0269 0.47709872372,2 DMC4 0.058 0 0.0704 0.43643681892,3 DMC4 0.0167 0 0.0203 0.37147303972MC5 0.0607 0 0.0737 0.3605294133MC5 0.0372 0 0.0452 0.3362551971NP6 0.0214 0 0.026 0.29825794245N6 0.0396 0 0.0481 0.28752830576N6 0.0362 0 0.044 0.2449354634NP7 0.078 0 0.0947 0.15532483226N7 0.0024 0 0.0029 0.1502743966N8 0.0063 0 0.0076 9.55E-02

K-Value (HK) 0.6927922272Avg Temp T 238 F 114.4 C

Calculation of minimum number of stages Nm:

From Fenske Equation

Nm 5.4386996977Nm 6

Calculation of minimum reflux ratio:

From Colburn and Underwood we have an expression for minimum reflux ratio

(i * Xif)/(i - )

0.09802927190.02555821020.0269478038

-value can be found by 0.06938135010.15931541650.3489122836

-0.4227142857feed is at boiling point so q=1 -0.1061969101

-0.0150487561therefore at =1.7 -0.0341467626

-0.0076941607-0.0267788426

-0.014864906-0.0072573063

Rm+1 1.689562929 -0.0127902545Rm 0.689562929 -0.0095053132

-0.0118496447-0.0003510153-0.0005556325

Sum 0.0583905457-Value 1.7

Reflux ratio is 1.2 times the minimum reflux ratio

Reflux Ratio 1.2 RmReflux Ratio 0.8274755148

Calculation of Number of theoretical plates:

we first need to find the ratios of (Rm/Rm+1) and (R/R+1)

Rm/Rm+1 0.4081309534

R/R+1 0.452797046

From Erbar-Maddox correlation Vis A Vis B

Nm/N 0.37 13.82 5.39Nm 6 114.14 57.6N 16.216216216 156.6 95.57

222.67 133.41Number of theoretical plates 302.51 170.2

265.84 160.217 367.32 191.58

313.66 182.48406.69 231.67438.44 226.67

O'Connell's correlation. 444.19 228.86384.13 208.27372.11 207.55362.79 207.09

For Viscosity we have 440.52 243.24653.62 290.84436.73 232.53528.41 271.58506.43 280.76

0.1221891351.7919301232

a*a 0.2189543918

Eo 67.5 %

Actual Number of Trays:

170.675

Actual Plates

Nth

Plate Efficiency calculation (Eo):

Molar avg Viscosity a mNs/m2Relative volatility a

from O'Connell's graph for efficiency of the column (Eo)

NthEo

Nth/Eo

N 25.185185185N 26

Feed-point location:

Using Krikbride empirical equation

here B 2022 lbmol/hrD 456.5 lbmol/hr

log (Nr/Ns) 0.3386683122Nr/Ns 2.1810635114

Plates in stripping section (Below the feed)

N=Nr+NsNr+Ns 26Ns 8.173367148Ns 9

Plates in rectifying section (Above the feed)

Nr N-NsNr 17Feed-point 18

Column Diameter Calculation:

Flooding velocity can be estimated from the correlation given by Fair

here Uf is the flooding velocity based on net area An

At this stage we need to find the liquid-vapor flow factor FLV for top and bottom for constant K1

Assume tray spacing of 0.5 m

Rectifying Section:

Following are the necessary physical properties for Diameter calculation taken from HYSYS

24.76510

6.37 dyne/cm or 0.00637

Lw 14610 kg/hrVw 18840 kg/hr

0.1708675332

from graph0.06

0.04773

Now the flooding velocity0.2112886239 m/s

Design for 85% flooding at maximum flow rate

Maximum allowable vapor velocity based on the net column cross sctional area

0.1795953303 m/sMaximum volumetric flow rate 760.6

0.211278

Net Area required An 1.2

Take downcomer area as 12% of the total cross sectional area

v Kg/m3L Kg/m3

FLV

K1for values other than 0.02N/m surface tension a correction is applied for K1

K1

Uf

Uv Uf * 0.85Uv

m3/hrm3/s

Total column cross sectional area Ac 1.34

Diameter of the column D=((At 4)/)Dia 1.3045627066 m or 4.3

Stripping Section:


40.64466

4.135 dyne/cm or 0.004135

Lw 107300 kg/hrVw 33440 kg/hr

0.9475831828

from graph0.03

0.02

Now the flooding velocity0.0708128106 m/s

Design for 85% flooding at maximum flow rate


0.060190889 m/sMaximum volumetric flow rate 822.7

0.228528

Net Area required An 3.8

v Kg/m3L Kg/m3

FLV

K1for values other than 0.02N/m surface tension a correction is applied for K1

K1

Uf

Uv Uf * 0.85Uv

m3/hrm3/s

Take downcomer area as 12% of the total cross sectional areaTotal column cross sectional area Ac 4.31

Diameter of the column D=((At 4)/)

Dia 2.3436334528 m or 7.7

Both diameters differ more than 20%, therefore we will have two different diameters for the column.

Plate Areas:

Ac Total column cross seectional area for top Ac 1.34for bottom Ac 4.31

Ad Cross sectional area of downcomer 12% of Acfor top Ad 0.1604195722for bottom Ad 0.5177341502

An Net area available Ac-Ad (for single pass)for top An 1.18for bottom An 3.80

Aa Active or bubbling area Ac-2Adfor top Aa 1.0159906241for bottom Aa 3.278982951

Ah Hole area normally 10% of Aafor top Ah 0.1015990624for bottom Ah 0.3278982951

Weir Dimensions:

Recommended values for columns operating above atmospheric pressure for Weir Height

hw 40-50mmhw 50 mm

Weir length of 0.77 times Dc is recommended or we can use graph for weir length

Ad/Ac 0.12 or 12

m2m2

m2m2

m2m2

m2m2

m2m2

From graph the ratiolw/Dc 0.77

for top lw 1.0045132841 m orfor bottom lw 1.8045977587 m

Number of tray passes:

for top sectionliq flow 126.1 gpmweir length lw 39.547788447 inRatio 3.1885474498 gpm/in of weir

for bottom sectionliq flow 1014 gpmweir length lw 71.047194218 inRatio 14.272203303 gpm/in of weir

Both top and bottom liquid flow rate are nearly in the given recommended range.So we have selected singe pass cross flow with sgmental downcomer.

Other tray specifications:

Assumed tray spacing 0.5 mHole diameter 5 mmPlate thickness 5 mm for carbon steel

Tray Hydraulics:

Weep Point:

from HYSYS Maximum liquid rate 107300 kg/hr29.80556 kg/s

Turn down ratio 70 %Min liq rate 20.86389

For one pass design, the liquid flow rate does not exceed 7to 13 gpm/in of outletweir .

Weir crest

Maximum how 80.92484 mm of liqMinimum how 63.799 mm of liq

At minimum rate hw+how 113.799 mmFrom graph 31

minimum design vapor velocity 1.9827603442Actual minimum vapor velocity Minimum Vapor rate/Ah

0.4878629954

Plate pressure drop:Plate pressure drop is given by

first we calculate dry plate pressure drop

Plate thickness/Hole diameter 1Percent perforated area

0.1 or

from graph 0.84maximum vapor velocity through holes 0.6969471363now 3.0618158187

Residual head is given by

hr 26.824034335 mm of liq

The total plate drop is given by ht=hd+hr+(hw+how)

ht 160.81069162 mm of liq

now P 735.13964434 orfor total pressure drop across all trays

K2

for orifice coefficient Co we use graph

CoUhhd

N/m2

Downcomer liquid backup:

here

Am is either the downcomer area or clearance area under the downcomer Aap, whichever is smaller

Taking height of Apron hap=hw-10hap 40 mm

Area Aap hap*lw

Aap 0.0721839103 m less than downcomer area

130.3316481 mm of liq

downcomer liquid backup 422.0672 mm of liq0.422067 m

Residence time calculation:

tr 3.4164659109 s 3s

Entrainment Check:

percentage flooding = Un (act velocity based on net area)/Uf (flooding velocity based on net area)

Un 0.060190889 m/sUf 0.0708128106 m/spercentage flooding 0.85

85 %0.9475831828

from graph

fractional entrainment 0.001 well below 0.1

hdc

hb

FLV

Total Number of holes:

Number of holes = Ah/ah

here ah area of one hole

dh 5 mmahah 1.96375E-005

Number of holes 5173.72692095174 holes

Height of Distillation Column:

Number of plates 26Tray spacing 0.5Distance between 26 plates tray space*N

13

Top and bottom clearance usually amount to 15% of that required by trays

Top and Bottom Clearance 1.95Tray thickness 5total thickness 0.13

Total height of the column 15.0849.4750672

50

* dh2/4m2/hole

Composition of feed, top and bottom and relative volatilities are:

The key components selected are n-C4 and i-C5 as light and heavy key respctively.

Relative Volatility

61.060153666521.1100681079

7.57485988953.69960164392.11070669031.7919301232

10.87895551630.68866061860.6299678342

0.5361968930.52040048790.4853622543

0.4305157170.41502819230.35354822670.22420117620.21691120380.1377809003

From Colburn and Underwood we have an expression for minimum reflux ratio

(i * Xid)/(i - )

0.55536205570.14508362720.14801951560.21091930420.26415523890.4658661216

-0.0305714286-0.0011775867-0.0680939189

0000000000

1.689562929

Viscosity Xf * Viscosity

0.00296246 0.00028232240.020555101 0.0004830449

0.0582756837 0.00121796180.0804438475 0.00301664430.1007373902 0.00312285910.1062978504 0.00190273150.1072707083 0.03174140260.1231593616 0.01221740870.1967505846 0.00434818790.1574151096 0.00913007640.1604235033 0.00267907250.1402137612 0.00851097530.1469910158 0.00546806580.1528496492 0.00327098250.2116548985 0.0083815340.2749104037 0.0099517566

0.177310109 0.01383018850.261682442 0.0006280379

0.3183940376 0.0020058824

Sum 0.122189135

for top and bottom for constant K1


N/m


m2

ft


N/m


m2

m2

ft

Both diameters differ more than 20%, therefore we will have two different diameters for the column.

Recommended values for columns operating above atmospheric pressure for Weir Height

Weir length of 0.77 times Dc is recommended or we can use graph for weir length

%

m2

39.5477884471 in71.0471942183 in

Both top and bottom liquid flow rate are nearly in the given recommended range.

For one pass design, the liquid flow rate does not exceed 7to 13 gpm/in of outletweir .

m/s

m/s

10

m/smm of liq

0.7351396443 KPa19.1136307527 KPa

Am is either the downcomer area or clearance area under the downcomer Aap, whichever is smaller

less than downcomer area

Setisfactory

percentage flooding = Un (act velocity based on net area)/Uf (flooding velocity based on net area)

Setisfactory

mm

mmm/platem

mftft

Sheet1

stabilizer design(part 2)

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