Page 1 of 27

A

Summer

Project Report

on

“Designing of De-superheating propane condenser for

DPD train installed in ONGC HAZIRA PLANT”

Submitted by:

Jay Tailor

B.E Chemical engineering

M.S. University, Baroda

Page 2 of 27

ACKNOWLEDGEMENT

Sharing our experience is one of the biggest honors’ which

every one cannot experience. To share our experience at ONGC as

engineering student is a matter of great Honors and Pride.

We are grateful to ONGC for letting us to do this project. We

express our gratitude to Mr. Y.K.VERMA (I/C, Training Center), Mr.

Vicky Motwani (Project guide) and our sincere thanks to Mr.

N.R.CHAUDHARY, ONGC Hazira for guiding us through the various

aspects. We are really thankful to Employees of ONGC who have been

guiding us in this path Step by Step and have made our path really

simple to get through. We will use this experience throughout our career

and will make our future bright. So once again we thank all of them.

And the most precious part of our life, our parents who have

showered their love and support which can be never repaid in any form

but can be commemorated without them this achievement could not

have been achieved.

Page 3 of 27

PREFACE

The vocational training provided is essential step towards making

future engineer familiar with the practice aspect of their field .During the training

period the trainee is exposed to the work of the company.

During the training the trainee gets an opportunity to relate the

theoretical knowledge with practical operation. He is the first given a brief

overview of the entire setup and then detailed description of individual units

follows.

ONGC is one of the leading enterprises in the country with substantial

contribution to the energy demand in particular and its industrial and economic

growth in general. Born in a modest corporate house with in serene Himalayan

setting 55 year ago in 1956 as commission, ONGC has growth, today into a fully

fledged integrated upstream petroleum company with in house service

capabilities and infrastructure into the range of oil and gas exploration and

production activities.

We feel privileged to make the opportunity of undergoing this training

at ONGC (HAZIRA PLANT). During training we made familiar with the various

operations, equipment and their function and their safety measure of individual

working units. We made these humble efforts to put up in words sum

information, in brief, about the operation of the plant that we could gather during

training.

Page 4 of 27

INTRODUCTION

Hazira gas processing complex was set-up in September 1985 to receive gas

from Mumbai high initially and subsequently to process sour natural gas from bassein and

other offshore fields. Sour along with associated condensate is transfer through two subsea

pipeline form bassein offshore platform to hazira plant.

1. 36” diameter pipeline (231 Km)

2. 42” diameter pipeline (244 Km)

Hazira plant is the largest gas processing complex in the country. It is designed

to process 41MMSCMD (Million Standard Cubic Meters per Day) sour gas Sour natural gas

and associated condensate. Natural gas containing toxic and corrosive H2S gas is given a

special treatment to making it sweet, marketable and safe for domestic and industrial use. The

gas and condensate are received at the gas terminal in a slug catcher where gas and slug

containing HC condensate, moisture and chemicals (like corrosion inhibitors) are separated.

Gas and associated condensate are sent further in separate system for processing. The various

processing units are,

1. Gas Receipt Terminal,

2. Gas Sweetening Unit (GSU),

3. Gas Dehydration Unit (GDU),

4. Dew Point Depression Unit (DPDU),

5. Sulphur Recovery Unit (SRU),

6. our Condensate Processing Unit,

7. Gas Based LPG Recovery Unit and

8. Kerosene Recovery Unit (KRU)

Page 5 of 27

The sour gas and condensate are received from offshore in a multiphase flow.

They are separated by gravity into two steams, gas and liquid at initial stage. The sour gas

separated is taken out from top riser pipes of slug catcher to Gas Sweetening Unit (GSU) and

the sour liquid thus collected is routed to Condensate Fractionation Unit (CFU).

The purpose of GSU is to remove lethal H2S from sour gas. Sour gas from slug

catcher is distributed to different GSU trains, which comes in counter current contact with

lean amine solution (Methyl Di Ethanol Amine) in absorption column. The sweet gas leaves

from the top of the column with 4 ppm H2S which is routed to GDU/LPG units. The rich

amine enters the regeneration and re-circulation in the system. Acid gas liberated from top of

the regenerator column during recycling of amine forms feed for sulphur recovery unit.

The Gas Dehydration Unit (GDU) aims at removal of water vapors from

sweetened gas from GSU. The sweet gas in counter-current contact with lean Tri-Ethylene

Glycol (TEG) solution in absorption column. The dry gas liberated from top of the absorber

forms feed for Dew Point Depression Unit. The rich TEG is sent to reboiler to regenerator to

remove moisture. The regenerated TEG continuously recycled and reused in the system.

The purpose of DPD unit is to remove hydrocarbon condensate from the

sweetened and dehydrated gas by chilling to avoid hydrate formation in the long distance H-

B-J pipeline. The feed gas from GDU trains is chilled to about -5 0C in a chiller with the help

of propane refrigerator in closed circulation cycle. The cooled gas condensate is pumped to

LPG plant for distillation. The treated gas is then sent to GAIL for onward transmission to H-

B-J pipeline and partly to local consumers.

Page 6 of 27

The Condensate Fractionation Unit (CFU) aims at removal of H2S and recovery

of LPG and NGL (Natural Gas Liquid) from the sour hydrocarbon condensate separated in

the slug catcher. The liquid from slug catcher is distributed into stripper columns of various

CFU trains. H2S is stripper from the condensate along with lighter hydrocarbons and fed to

GSU trains for removal of H2S. The liquid from stripper bottom is fed to LPG column for

recovery of LPG from the top and NGL from the bottom. The LPG is sent to caustic wash

unit for removal of H2S. The LPG is sent to Caustic Wash Unit for removal of H2S. The NGL

forms the feed for KRU.

The LPG from CFU contains upto 20 ppm H2S which has to be removed to less

than the permissible limit of 4 ppm in CWU before it is sent for storage in Horton spheres.

The LPG is passed through absorber tower containing caustic solution to wash and remove

H2S.NGL produced from CFU is given value addition in KRU by way of producing aromatic

rich naptha (ARN), superior kerosene oil (SKO), heavy cut (HC) and/or high-speed diesel

(HSD). The hot NGL is fed to Naptha Column for distillation from where Naptha is

recovered as a top product. The bottom steam is fed to the kerosene column through the gas

fired furnace for further fractionation. Kerosene/ATF is recovered from top of the kerosene

column and HSD is recovered from the bottom.

A part of sweet gas from outlet of GSU (about 5 MMSCMD) and all the sweet

condensate from DPD are taken as feed to LPG recovery unit. Here cryogenic process is done

by turbo-Expander. The feed gas is first dried in molecular sieve dryers and then chilled in a

cold box to -300C. The chilled vapor is expanded isentropically in turbo-expander wherein

temperature of the gas falls to -570C. In the chilling process heavier hydrocarbons (C3+) get

liquefied and separated for fractionation in the LEF and LPG columns. The lean gas liberated

is further compressed as per requirement of consumer. The product come out from the LPG

unit is naphtha from bottom and LPG from top. A part of the LPG is further distillate to

obtain propane, which is used as a refrigeration cycle in LPG and DPD unit.

Page 7 of 27

The purpose of SRU is to convert acid gas liberated from GSU into elemental

sulphur for environment protection. Acid gas comes in contact with catalyst LOCAT solution

in absorber. H2S is oxidized to elemental sulphur in presence of the catalyst. Air is introduced

into Absorber for regeneration for catalyst. Sulphur is palletized up to 99% purity and sand

for disposal in HDPE bags in the market. The catalyst is re circulated in the system and make

up chemicals are dosed to maintain the quality. The vent gas from the top of absorber vessel

containing CO2, N2, O2 and moisture vented to atm.

Hazira plant also has utility units & offsite facilities for safe and smooth

operations. They are as follows,

1.) Cogeneration power

2.) Steam system

3.) Water system

4.) Air system

5.) Inert gas system

6.) Effluent treatment plant

7.) Product storage

8.) Dispatch

Page 8 of 27

Page 9 of 27

AIM:- Designing of de-superheating propane condenser for DPD unit from the

given data and compare the result with actual design.

DATA GIVE:-

Over all heat duty: - 2105798 Kcal/hr = 2448.458 KW

Hot fluid temperature, Inlet: - 75.67 0C

Outlet: - 45.00 0C

Cold fluid temperature, Inlet: - 43.00 0C

Outlet: - 33.00 0C

Operating Pressure: - 14.88 Kg/cm2

Baffles space: - 0.4 m

Outer diameter of tube: - 0.020 m

Inner diameter of tube: - 0.018 m

Length of tube: - 5.9 m

RESULT SHOULD BE MATCHED

WITH: -

Diameter of the shell: - 1.157 m

Heat transfer area: - 526.71 m2

Number of tubes: - 1432

Page 10 of 27

SOLUTION: -

Now properties of water at average temperature T = 38 0C (311.5 K)

Density 992.0466 Kg/m3

Specific heat Cp 4183.144 J/Kg K

Viscosity 6.0814*10-4

Pa sec

Thermal conductivity k 0.6276 W/m K

Now for water,

Q = mCpt

Where,

Q = Total heat duty, KW = KJ/sec

m = mass flow rate of water, Kg/sec

t = Temperature gradient of water, K

Cp = specific heat of water, J/Kg K

K

KKgJ

J

tCp

Qm

10*.

144.4183

sec10*458.2448 3

= 58.53 Kg/sec

From P-H diagram (given on page no. 10) of propane at 1.46 MPa pressure,

Saturation temperature, Tset = 45 0C (318.15 K),

Specific heat, = 300 KJ/Kg.

Page 11 of 27

Page 12 of 27

FOR DESUPERHEATING

Now properties of propane at average temperature of de-superheating T = 60 0C

(333.15 K)

Density 30.51 Kg/m3

Specific heat Cp 2268.63 J/Kg K

Viscosity 9.087*10-6

Pa sec

Thermal conductivity k 0.02388 W/m K

Total heat duty for propane,

Q = MCp

Where,

Q = Total heat duty, W = J/sec

M = mass flow rate of propane, Kg/sec

T = Temperature gradient of propane, K

= latent heat of propane at P= 1.48 MPa, J/Kg

Cp = specific heat of propane, J/Kg K

KgJK

KKgJ

J

TCp

QM

30000010*.

63.2268

sec10*458.2448 3

= 6.62 Kg/sec

Now Heat duty for condensation of Propane,

QC =

QC = 6.62 (Kg/sec)*300000 (J/Kg) = 1987.477 KW

Now Heat duty for de-superheating of Propane,

Qd = Cp T

Qd = 6.67 (Kg/sec)*2190.45 (J/Kg K)*(75.67-45) (K) = 460.98 KW

Page 13 of 27

Now by using heat duty of condensation we find temperature gradient

required for water in condensation,

QC = mCptc

Where, QC = heat duty for condensation, KW = KJ/sec

tc = Temperature gradient required for water in condensation, K

sec83.58*

.144.4183

sec10*458.2448 3

KgKKg

J

J

Cpm

Qtc = 8.17 Kg/sec

DESUPERHEATING

CONDENSATION

HOT FLUID

(PROPANE)

COLD FLUID

(WATER) DIFFERENCE

75.670 High Temp. 34.88 40.78

45.000 Low Temp. 33.00 12.00

30.670 Difference 01.88 28.84

60.335 Avg. Temp. 33.94 -

HOT FLUID

(PROPANE)

COLD FLUID

(WATER) DIFFERENCE

45 High Temp. 43.00 02.00

45 Low Temp. 34.88 10.12

00 Difference 08.17 08.17

45 Avg. Temp. 38.94 -

Page 14 of 27

Tln = log mean temperature difference (LMTD), K

22

11

2211

ln

)(

ch

ch

chchin

TT

TT

TTTTT

Where,

Th1 = Inlet of hot fluid,

Th2 = Outlet of hot fluid,

Tc1 = Inlet of cold fluid,

Tc2 = Outlet of cold fluid.

Now, LMTD for de-superheating;

Here in our case there is only De-superheating and condensation is occurs. There is no sub-

cooling in our case.

3345

88.3467.75ln

)3345()88.3467.75(DLMTD = 23.53 K

Now, LMTD for condensation;

88.3445

4345ln

)88.3445()4345(CLMTD = 5.0074 K

Now, T ln weighted;

K

KWK

KW

KWKW

LMTD

Q

LMTD

Q

QQT

D

D

C

C

DC

53.23

98.460

0074.5

477.1987

)(98.460)(477.1987ln

= 5.8784 K

Page 15 of 27

For given system of water-propane condenser, value of overall heat transfer co-

efficient is lies between 454.264 W/m2K to 1135.66 W/m

2K.

Let take estimate value of overall heat transfer co-efficient as 800 W/m2K, as it

is mean of above values.

Now,

Q = U A Tln

Where,

U = Overall heat transfer co-efficient, (W/m2 K)

A = Total heat transfer area, m2

KmW

J

TU

QA

in 8784.5sec)/(800

sec1048.2448

2

3

= 520.69 m

2

NOW, TUBE SIDE HEAT TRANSFER CO-EFFICIENT CALCULATION

Here we use seamless low carbon steel tubes,

Inside diameter of tube, di = 0.018 m,

Outside diameter of tubes, do = 0.020 m, ………… (From data)

Length of tubes, L = 5.9 m

Total heat transfer area, A=Nt (doL)

1405)9.5)(020.0(

63.520

Ld

AN

o

t

So, 1340 tubes are used. Now if we take 6 pass on shell side then,

Number of tubes per pass = 235 tubes,

So, total tubes required according to pass are 1410 tubes,

Total heat transfer area = 1410*()*(5.9)*(.020) = 522.69 m2

Volumetric flow rate = sec/059.00466.992

53.58 3m

Page 16 of 27

Cross section area per pass = 22

)018.0(4

2354

it dN = 0.0598 m

2

Velocity through tube, u = 2

3

0598.0

sec059.0

/

_

m

m

passarea

flowratevolumetric = 0.9866 m/sec

sec.108014.6

0466.992sec

9866.0)(018.0

4

3

Pa

mKgmm

udN i

RE

= 28781.6817

NRE = Reynolds Number,

di = inside diameter of tube, m

u = velocity through tubes, m/sec

= density of tube site fluid, Kg/m3

= viscosity of tube site fluid, Pa.sec = Kg/m3sec

Km

W

PaKKg

J

k

CN P

PR

.6278.0

sec.10*8014.6.

144.4183 4

= 4.533

NPR = Prandtl Number,

= viscosity of tube site fluid, Pa.sec = Kg/m3sec

Cp = specific heat of tube site fluid, J/Kg K

k = thermal conductivity tube site fluid, W/m K

Page 17 of 27

Details Boltzmann equation,

NNU = 0.026 (NRE) 0.8

(NPR) 0.3

= 0.026 (35544.7278)0.8

(4.533)0.3

=151.075

Where, k

dhN ii

NU

NNU = Nusselt Number,

hi = Inside tube side heat transfer coefficient , W/m2 K

di = Inside tube diameter, J/Kg K

k = thermal conductivity tube site fluid, W/m K

)(018.0

)06276)(075.151(

m

mKW

hi 5267.5 W/m2K

CALCULATION ON SHELL SIDE

As per given here we take rotated square

pitch,

o

oT

ed

dPD

22

44

Where,

De = Effective Diameter,

PT = Pitch,

PT = 1.25 dO = 1.25*0.02 = 0.025 m

02.0*

)02.0*4

025.0(4 22

eD = 0.01975 m

Page 18 of 27

SHELL DIAMETER CALCULATION

LCTP

dPRACLD o

s*

**.*637.0

2

Where,

Ds = shell diameter, m A = total heat transfer area, m2

L = length of the tubes, m dO = outside tube diameter, m

C.L. = Tube layout constant ……………….. (Appendix table 2)

C.T.P = Tube counting calculation constant ...………………. (Appendix table 3)

Ds =)(9.5*85.0

)(02.0*25.1*)(7.522*1637.0

22

m

mm = 1.149m

Now,

T

s

sP

BCDA

...

Where, As = cross flow area,

Ds = shell diameter,

C = PT - do= 0.25*0.02= 0.005 m

B = baffle space = 0.4 m

)(025.0

)(4.0*)(005.0*)(149.1

m

mmmAS = 0.09196 m

2

Page 19 of 27

HEAT TRANSFER COEFFICIENT FOR DESUPERHEATING

Mass velocity, Gs =)(09196.0

sec625.6

2m

Kg

A

M

s

= 72.035 Kg/m2 sec

Now from kern’s equation,

14.03

155.0 *

36.0

w

pseeo

k

cGD

k

Dh

14.0

6

63

1655.0

6 10*46.9

10*089.9

0237.0

63.2268*10*089.9

10*089.9

035.72*01975.036.0

0237.0

01975.0*

oh

ho = 295.077 W/m2 k

Now, overall heat transfer coefficient for de-superheating,

f

i

o

m

m

i

o

iod

Rr

r

k

X

r

r

hhU

ln

111

Where,

Ud = overall heat transfer coefficient for de-superheating, W/ m2K

Xm = thickness of the tube, m

km = thermal conductivity of metal, W/m K tsf RRR

111

Rf = Overall fouling resistance, K m2/W

Rs = Shell side fluid fouling resistance, K m2/W ………… (Appendix table 1)

Rt = Tube side fluid fouling resistance, K m2/W

000235.0

1

0002.0

1

1

11

1

ts

f

RR

R =0.00010805 K m2/W

Rf = 0.00010805 K m2/W

00010805.0017.0

021.0ln

)45(

)018.0020.0(

5.5267

1

018.0

02.0

077.295

11

dU

Ud = 269.35 W/m2 K

Page 20 of 27

Now, let’s find area required for de-superheating only,

)(55.23)/(33.265

sec)/(1098.4472

3

KKmW

J

LMTDU

QA

dd

dd

= 72.733 m

2

So, area required for de-superheating = 100698.522

733.72 = 13.915%

So, total area required for condensation is equal to 86.085%

HEAT TRANSFER COEFFICIENT FOR CONDENSATION

Effective length= 86085.09.5 = 5.079 m

Condensation load, 3

2

1410)(079.5

)/(625.6'

m

skgG = 0.010373 Kg/m K

CALCULATION FOR FLIM TEMPERATURE

Wall temperature, ioo

vcocw

hh

TThTT

)( & film temperature,

2

wvf

ttt

;

Where,

Tw = wall temperature, K

Tc = average temperature of cold fluid, K

Tv = saturation temperature, K

hio = Tube outside heat transfer coefficient based on hi, W/m2 K

)/)(5.5267(02.0

018.0 2KmWxhd

dh i

o

iio = 4740.74 W/m

2 K

Value of ho for condensation is lies between 567.86 W/m2 K to 1703.49 W/m

2 K. Let

estimate the value of heat transfer co-efficient ho = 1100 W/m2 K, as it is mean value

of the above range.

Page 21 of 27

74.47401100

)4538(1100

2

3343

wT = 39.8

0C = 312.56 K

2

458.39

2

wV

f

ttt = 42.38

0C = 315.35 K

Now properties of propane at film temperature tf = 42.38 0C (315.53 K)

Specific gravity Sf 0.59 -

Viscosity 80.95*10-6

Pa sec

Thermal conductivity k 0.08502 W/m K

From graph ho =1325.56 W/m2K,

Now we take this value as initial guess of ho and further calculate ho, till ho (est) = ho (cal).

After performing 2 iteration final value of ho = 1220.83 W/m2K is to be found and we

consider this value for further calculation.

Now, overall heat transfer coefficient for condensation,

f

i

o

m

m

i

o

ioc

Rr

r

k

X

r

r

hhU

ln

111

00010805.0017.0

021.0ln

45

)018.002.0(

018.0

02.0

5.5267

1

83.1220

11

cU

Uc = 875.058 W/m2 K

Now, let’s find area required for de-superheating only,

)(0072.5)/(058.875

sec)/(105.19872

3

KKmW

J

LMTDU

QA

cc

cc

= 453.59 m

2

Page 22 of 27

Page 23 of 27

Total area, At = Ac + Ad = 453.59 + 72.73 = 526.36 m2

t

ddcc

A

UAUAU

=

36.526

35.26973.72058.87559.453 = 791.35 W/m

2 K

Now we take this value as initial guess of U (in Q = U A Tln) and further calculate U,

till U (est) = U (cal). After performing 4 iteration final value of U = 789.66 W/m2K is to

be found and we consider this value as over all heat transfer coefficient. Based on this

value of overall heat transfer coefficient data sheet for propane condenser is as bellow.

PRESSURE DROP CALCULATION

SHELL SIDE

se

sBss

D

DNfGP

2

)1(2

Where, f = exp (0.576-0.19ln (NRE))

= exp (0.576-0.19ln (155854.254)) = 0.1834

NRE = Reynolds number on shell side,

s = (/w) 0.14

NB = No. of baffles = effective length / baffle space

Now pressure drop calculation for de-superheating and condensation, only difference in both

calculations is baffles number, all other parameters remains constant in both the cases.

Number of baffles used for de-superheating:-

Effective length for de-superheating = L (Ad %) = 5.9*0.1383 = 0.1816 m

No of baffles for de-superheating = effective length/baffle space = 0.1816/0.4 = 2.13 = 2

Effective length for condensation = L (Ac %) = 5.9*0.8616 = 5.08389 m

No of baffles for condensation = effective length/baffle space = 5.08389/0.4 = 12.98 = 13

Page 24 of 27

For de-superheating

96.001974.051.302

15.1)12(72.711834.0

2

)1( 22

se

sBss

D

DNfGP

= 2784.83 Pa

For condensation

96.001974.051.302

15.1)113(72.711834.0

2

)1( 22

se

sBss

D

DNfGP

= 12467.76 Pa

Total pressure drop on shell side = 2784.83 + 12467.76

= 15232.59 Pa

= 0.16 Kg/cm2

TUBE SIDE

rttotal PPP ; i

mPt

d

ufLNP

2

42

;

2

42

mPt

uNP

;

Where,

Pt = tube side pressure drop, Pa

Pr = reverse pressure drop, Pa

f = 0.046NRE-0.25

= 0.046(28538.97)-0.25

= 0.0035

Np = no. of pass = 6

018.02

9783.00466.99269.50035.04

2

4 22

i

mPt

d

ufLNP

= 13217.22 Pa

2

9783.00466.99264

2

4 22

mPt

uNP

= 11393.6431 Pa

6431.1139322.13217 rttotal PPP

= 24610.87 Pa

= 0.25 Kg/cm

Page 25 of 27

Flow

type cross current heating surface 527.45 m

2

PERFORMANCE

NO. Unit SHELL SIDE TUBE SIDE

1 Fluid circulated Propane Water

2 Flow rate Kg/sec 6.624991188 58.53152868

3 Flow rate Kmol/hr 542.0447335 11706.30574

4 Flow rate m3/hr 781.7098746 212.4028279

5 Specific gravity - 0.59 -

6 Latent Heat KJ/Kg 300 -

7 Viscosity (DSH/Cond.) Pa.sec 9E-06 8E-05 0.00068014

8 Molecular Weight Kg/Kmol 44 18

9 Thermal conductivity W/m K 0.0237 0.0859 0.6276

10 Specific heat J/Kg K 2268.636364 4183.144

11 Temp of cond. (In/Out) K 318.15 318.15 308.03 316.15

12 Temp of DSH. (In/Out) K 348.82 318.15 306.15 308.03

13 Saturation Temp K 318.15 -

14 Operating Pressure MPa 1.48 1.48

15 Velocity m/sec - 0.974195312

16 Pressure Drop

(allow/calc) Kg/cm

2 0.2 0.16 0.5 0.25

17 Overall heat transfer

coefficient W/m2k 789.6631484

18 Total Heat exchanged KW 2448.45813

19 LMTD K 5.878490415

20 Tube Diameter (In/Out) m 0.018 0.02

21 Tube Length m 5.9

22 No. of tubes - 1424

23 No. of baffles

(DSH/Cond.) - 2 13

Page 26 of 27

APPANDIX

Table 1

Table 2 Table 3

passes CTP

1 pass 0.95

2 pass 0.9

more pass 0.85

Angle C.L.

900C or450C 1

600C or 300C 0.87

Page 27 of 27

RESULT:-

Number of tubes: - actual = 1432 tubes

Calculated = 1424 tubes

Pressure drop on shell side: - allowable = 0.2 Kg/cm2

Calculated = 0.16 Kg/cm2

Pressure drop on tube side: - allowable = 0.5 Kg/cm2

Calculated = 0.25 Kg/cm2

CONCLUSION

By doing this project on design of de-superheating condenser for DPD unit and compare it with

actual data we can say that our design is more or less same as actual design. So design can be

acceptable.

REFERENCES:-

Process Heat Transfer By DQ Kern, Unit 12

Perry’s Chemical Engineers Handbook – McGrawHill - 8th

edition, Unit 11

For thermal conductivity of metals:- http://www.bnl.gov/magnets/staff/gupta/cryogenic-

data-handbook/Section7.pdf