Absorber

Appendix F - 52

Production of 100,000 MTA Hydrogen

F.9 SIZING AND COSTING FOR ABSORBER

Absorber T-20

(a) Flowrate Data from simulation :Top Column (tray above feed)

= 20331.00 kmol/hr = 6.540E+05 kg/ hr

= 7208.80 kmol/hr = 1.95E+04 kg/ hr

= 838.3

= 2.687Surface tension, s = 0.02530 N/m

Bottom Column (tray below feed)

= 22059.0 kmol/hr = 7.298E+05 kg/ hr

= 7282.2 kmol/hr = 2.18E+04 kg/ hr

= 838.80

= 2.714Surface tension, s = 0.02127 N/m

(b) Column DiameterEstimation of vapor-liquid flow factorFor top column

== 0.1597

For bottom column

== 0.1723

Take tray spacing as = 0.55m

Liquid flowrate, Ln

Vapor flowrate, Vn

Liquid density, rL kg/ m3

Vapor density, rv kg/ m3

Liquid flowrate, Lm

Vapor flowrate, Vm

Liquid density, rL kg/ m3

Vapor density, rv kg/ m3

FLV Ln / Vn [ (rV / rL)1/2 ]

FLV Lm / Vm [ (rV / rL)1/2 ]

Estimation of correction factor, K1

Appendix F - 53


Chemical Engineering Volume 6 Second Edition (R.K. Sinnott, 1996)From Figure 11.27

= 0.0900

= 0.0800Correction for surface tensions,

== 0.0943

== 0.0810

== 1.6635 m/s

== 1.4215 m/ s

Design for 85 % flooding at maximum flowrate

= 1.4140 m/ s

= 1.2083 m/ s

Maximum volumetric flowrates

=

= 2.0136

=

= 2.2322

K1 (top column)

K1 (bottom column)

K1,c (top column) K1 (top column) [ s / 0.02 ] 0.2

K1,c (bottom column) K1 (bottom column) [ s / 0.02 ] 0.2

Estimate the flooding velocity, Uf

Uf (top column) K1,c (top column) [ ( rL - rv ) / rv] 1/2

Uf (bottom column) K1,c (bottom column) [ ( rL - rv ) / rv] 1/2

Therefore, Uf = 0.85 x Uf

Uf (top column)

Uf (bottom column)

Vmax (top column) Vn

3600 × rv

m3/ s

Vmax (bottom column) Vm

3600 × rv

m3/ s

Appendix F - 54


Net area required

=

= 2.01361.4140

= 1.4241

=

= 2.23221.2083

= 1.8473

Take downcomer area as 12% of total column cross-sectional area.Column cross-sectional area

= 0.88

= 1.42410.8800

= 1.6182

= 0.88

= 1.8473 0.88

= 2.0992

Column diameter

== 1.4353 m

== 1.6348 m

Take the larger diameter as a final diameter for further design procedure, so

= 1.6348 m

An (top column) Vmax (top column)

Uf (top column)

m2

An (bottom column) Vmax (bottom column)

Uf (bottom column)

m2

Ac (top column) An (top column)

m2

Ac (bottom column) An (bottom column)

m2

Dc (top column) [ (Ac (top column) × 4) / p ]1/2

Dc (bottom column) [ (Ac (bottom column) × 4) / p ]1/2

Dc

Appendix F - 55


(c) Liquid Flow Pattern

aximum volumetric =

liquid rate,Lmax = 0.2417

Chemical Engineering Volume 6 Second Edition (R.K. Sinnott, 1996)

= 1.6348 mand

= 0.2417

Therefore,The selected recommended liquid flow pattern is single pass tray

(d) Provisional Plate Design

= 1.6348 m

= 2.0992

Downcomer area, =

Ad (at 12%) = 0.2519

=

= 1.8473

=

= 1.5954Take 10% as first trial :

=

= 0.1595


Therefore,

= 0.77

= 0.77 × Dc= 1.2588 m

Take the recommended value

= 50 mm (above 1 atm operation)= 0.050 m

= 5 mmPlate thickness = 3 mm (stainless steel)

Lm / (rL × 3600)

m3/ s

From Figure 11.28

For Dc

Lmaxm3/ s

Column diameter, Dc

Column area, Ac m2

12% × Ac

m2

Net area, An Ac - Ad

m2

Active area, Aa Ac - 2Ad

m2

Hole area, Ah 10% × Aa

m2

From Figure 11.31

For (Ad / Ac) x 100% = 12%,

Iw / Dc

Weir length, Iw

Weir height, hw

Hole diameter, dh

Appendix F - 56


(e) Check Weepingaximum liquid rate, = 729820.0 kg / hrLmax = 202.7278 kg /s

Minimum liquid rate =at 70% turn down, = 141.9094 kg/sLmin

== 249.6116 mm liquid

== 196.7872 mm liquid

At minimum rate, = 246.7872 mmhw + how, min


= 31.0

Minimum vapor velocity through the holes

=

= 7.6726 m/s

Actual minimum vapor velocity,

=

= 9.7936 m/s

so minimum operating rate will not be well above weep point

Lmax × 70%

Maximum how 750 [ Lmax / ( rLIw) ]2/3

Minimum how 750 [ Lmin / ( rLIw) ]2/3

From Figure 11.30

K2

Uh (min) [ K2 - 0.90( 25.4 - dh ) ]

rv1/2

Ua (min) 0.7 x Maximum volumetric flowrate, Vmax

Ah

Since Ua (min) < Uh (min),

Appendix F - 57


(f) Plate Pressure Drop

Maximum vapor =velocity through = 2.2322 holes, Uh 0.1595

= 13.9909 m/s


For (i) plate thicknes= 0.6

Therefore, Orifice = 0.7400coefficient, Co

== 58.9862 mm liquid

== 14.902 mm liquid

= 373.500 mm liquid

(g) Downcomer Liquid Back-UpDowncomer pressure loss

= 40 mm= 0.0400 m

=

=

= 0.0101

== 0.010 mm= 0.000010 m

== 112.32 mm= 0.1123 m

Since0.1123 < 1/2 ( plate spacing + weir height )0.1123 < #VALUE!

So, tray spacing is acceptable

Vmax / Ah

(ii) Ah/ Ap @ Ah/ Aa = 0.1

Dry plate drop, hd 51 [ Uh / Co]2 rv / rL

Residual head, hr (12.5 × 103) / rL

Total plate pressure drop, ht = hd + hw + how (max) + hr

Take hap = hw -10 = 50 - 10

Area under apron, Am hap × It

(40 × 10-3) × 1.0383

m2

Head loss in downcomer, hdc 166[ Lmax / (rL x Am) ]2

Back-up downcomer, hb hw + how + ht + hdc

Appendix F - 58


=

= 0.1171 s(since tr > 3s, the retention time is satisfied)

= 0.0020 min

(h) Check EntrainmentActual percentage flooding for design area :

=

= 2.2322

1.8473= 1.2083 m/ s

% flooding == 1.2083 × 100

1.4140= 85.45 %

Chemical Engineering Volume 6 Second Edition (R.K. Sinnott, 1996)From Figure 11.34For % floooding = 85.45 %

= 0.1723Fractional = 0.0350entrainment, y

y well below 0.1, satisfactory (y below 0.1 give small effect only to the column efficiency.)

(i) Perforated AreaFrom Figure 11.32Chemical Engineering Volume 6 Second Edition (R.K. Sinnott, 1996)

= 1.25881.6348

= 0.7700

= 99°

Angle subtended at plate edge by unperforated strip, = 180° - 99° = 81°

Mean length, unperforated edge = (1.6348 - 0.05)π × (81/ 180) strips = 2.2131

Check retention time, tr AdhbrL

Lmax

Uv Maximum volumetric flowrate, Vmax

An

(Uv / Uf) × 100

and FLV

At Iw/ Dc

Therefore, qc

= ( Dc - hw )π × (81 / 180)

Appendix F - 59


Area of unperforated = edge strips = 0.05 × 2.2131

= 0.1107

Area of calming =zones = 2 × 0.05 ( 1.2588 - 2 (0.012) )

= 0.1159

=

= 1.3689

= 0.15951.3689

= 0.1165

hw × mean length

m2

2hw ( weir length, Iw - 2hw )

m2

Total area available for perforation, Ap

Aa - (area of unperforated + area of calming)

m2

Ah/ Ap

Appendix F - 60



= 2.76 (satisfactory, within 2.5 to 4.0)

(j) Number of Holes

Area of one hole = 1.964E-05

Number of holes =Area of one hole

= 0.15951.964E-05

= 8123.4= 8123 holes

(k) Height of Column

Number of trays, n = 8assume stage efficiency = 0.7

Number of real = (n-1)/0.7stages,N

= 10

Ip / dh

m2

Ah

Appendix F - 61


Plate thickness = 3 mm= 0.003 m= N × plate thickness = 0.024 m

plate, Hp

Single plate spacing, = 0.55 m24"

Number of spacing = N - 1= 9

Tray stack = (N-1) x tray spacing = 5.40 mExtra feed space = 1.5 m

Disengagement space = 2.0 m(top & column)

Skirt height = 1.5 mTotal height of = 10.42 m

column, Ht

= 6.3764Equipment Costing for Absorber T-20From sizing results :

Pressure vessel = 21.7800 atm= 22.0686 bar

Column height = 10.42 m = 34.20 ftInside diameter = 1.63 m = 5.36 ftNumber of trays = 8Type of vessel = Vertically orientedMaterial of = Stainless steelconstructionEconomic data :

= 405.60

= 115

Equipment cost, C = Co

From Table 4.11, page 134, Systematic Methods of Chemical Process Design:With Co = 1000; Lo = 4.0; Do = 3.0; a = 0.81 ; b = 1.05

BC == $10,466.85

MF = 4.23

Total thickness of

Check : Ht/ Dc (satisfactory if Ht/ Dc < 20)

CE Index Year 2003, CEI03

CE Index Year 1968, CEI68

1000 × (34.22/4.0)0.81 × (19.67/3.0)1.05

( LLO

)α

( DDO

)β

Appendix F - 62


MPF =

= 1.93 (Stainless steel)

= 1.0MPF = 1.0 × 1.93

= 1.93

Update factor, UF = 3.53Update bare module = UF (BC) (MPF + MF - 1)cost = 3.57 (40992.46) (1.93 + 4.23 - 1)

= $190,487.22 = RM 725,756.30

Price of sieve trays

Equipment cost,C = Co

From Table 4.11, Systematic Methods of Chemical Process Design:With Co = 180; Lo = 10; Do = 2.0; a = 0.97; b = 1.45

C == $2,037.12

MF = 1

MPF =

= 1.7 (Stainless steel)

= 0 (sieve tray)

= 1 (24 inch.spacing)then,

MPF = 2.7000

Update factor, UF = 3.53Update bare module = Update bare module cost = UF(BC)(MPF+MF-1)cost = 3.57 (13418.05) (2.7 + 1 - 1)

= $19,399.04 = RM 73,910.34

Total equipment = 799,666.65cost, (RM)

Fm × Fp

Fm

Fp

180 × (34.22/10)0.97 × (19.67/2.0)1.45

Fm + Fs + Ft

Fm

Ft

Fs

( LLO

)α

( DDO

)β

Absorber

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