design of dehydrator

8/6/2019 Design of Dehydrator

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Dehydration design:

Gas production rate = 250 MMscfd = 7.078 Msd

Operating Pressure = 1000 psig = 1014.7 psia = 6997.93 Kpa

Container maximum working pressure = 1500 psig = 1514.7 psia = 10344.82 Kpa

Gas inlet temperature = 100 = 37.78 = 560° = 310.78°

Given sample of gas is:

S.no Compound Mole fraction Molecular Mass Kg/Kg-mol

Of mixture

1 C1 89.470 16.043 14.35367

2 C2 6.0664 30.070 1.824166

3 C3 2.7386 44.097 1.20764

4 iC4 0.1000 58.124 0.0581245 nC4 0.1200 58.124 0.069749

6 iC5 0.0769 72.150 0.055483

7 nC5 0.0081 72.150 0.005844

8 N2 0.0000 28.013 0

9 CO2 1.4200 44.010 0.624942

Total Total 10018.19962

Hence

Now we need to calculate Z

Calculations for Pseudo-critical Temperature and Pressure: By using the correlations we get:

Or

Or



Pseudo-reduce Temperature and Pressures are calculated as:

Now,

= 0.9790

From Standing & Katz chart we will calculate Z-factor as 0.88



Optimized required Dehydration rate = 95% (Based on economical aspects)

Glycol to water circulation rate = 5.5 gal TEG/ lb = 45.89 litres TEG/Kg

Lean Glycol concentration = 99.5

Water content specification is 7 lb = 112.13 mg

From figure 20-4 (GPSA) @ 6997.93 Kpa, dew point is -3, 970 mg

Now, Water removal efficiency is given as

= 88.44%

This value is less than our required Removal efficiency of 95%.

Hence we proceed as follows



From figure 20-70, numbers of theoretical stages are calculated as

Given: 45.89 litres TEG/Kg & Lean Glycol concentration = 99.5%

This gives:

Required water removal efficiency is 95% which is greater than 94.5%, hence numbers of

required stages are more than 1.5



From figure 20-71 GPSA

This gives:

Required water removal efficiency is 95% which is lesser than 96.5%, hence numbers of

required stages are 2.

2 trays = 8 bubble cap trays @ 0.6 m tray spacing or is equal to 3 m of structural packing.

(From table 20-75 GPSA)



For size of contactor:

From table 20-75 GPSA

C = 176

For TEG = 1119.7 (From table 20-56 GPSA)

Now,

H

M=

Now, Area (A) = M/G =/31032.23 = 7.3138

Hence we get diameter = 3.052 m

For structured packing:

From table 20-75 (GPSA)

C structured packing = 384 (Taking average value of 329 and 439)

D = *(D bubble cap)

= *3.052 = 2.066 m.

design of dehydrator

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