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Petroleum and Gas Processing(TKK-2136)

14/15 Fall semester

Instructor: Rama OktavianEmail: [email protected] Hr.: M.13-15, Tu. 13-15, W. 13-15, Th. 13-15, F. 09-11

Outlines

1. Crude distillation unit: Desalter

2. Distillation column configuration

3. CDU material balance

4. Crude oil products uses

Crude Distillation Unit (CDU)

Crude Distillation UnitCrude desalter unit

Salt content crude oil is usually denoted as pounds salt (measured as NaCl) per thousand barrels of crude oil (ptb)


The salt content should be lowered to between 5.7 and 14.3 kg/1000 m3 (2 and 5 PTB)

Poor desalting has the following effects:1. Salts deposit inside the tubes of furnaces and on the tube

bundles of heat exchangers creating fouling, thus reducing the heat transfer efficiency

2. Corrosion of overhead equipment3. The salts carried with the products act as catalyst poisons

in catalytic cracking units

Crude Distillation UnitCrude desalter unit operation variable

1. Desalting temperature – affect settling rate, typical desalting temperature can vary between 50 and150 C (122 and 302 F)

2. Washing water ratio – affect in salt removal, Kuwait crude (31.2 API) requires 7–8 vol% water addition relative to the crude rate

3. Water level - Raising the water level reduces the settling time for the water droplets in the crude oil, thus improving the desalting efficiency

4. Washing water injection point5. Demulsifier injection rate6. Type of washing water - relatively soft to prevent scaling, slightly acidic

with a pH in the range of 6, free from hydrogen sulphide and ammonia7. Pressure drop in the mixing valve - A pressure drop between 0.5 and

1.5 bar (7.4 and 22 psi) is used

Crude Distillation UnitCrude electrostatic desalting unit

Crude Distillation UnitAtmospheric distillation unit

Crude oil from the desalter is heated in a train of heat exchangers up to a temperature of 250°C–260°C and further by a tube-still heater (also known as a pipe-still furnace) to a temperature of 350°C–360°C

Top pressure is maintained at 1.2–1.5 atm

Vapours from the top of the column, consisting of hydrocarbon gases and naphtha, emerge at a temperature of 120°C–130°C

A few plates below the top plate, the kerosene fraction is drawn at a draw temperature of 190°C–200°C

A few plates below the kerosene draw plate, the diesel fraction ) is drawn at a temperature of 280°C–300°C

The temperature of the stream at the bottom reaches around 340°C–350°C


A typical atmospheric distillation column contains 41 plates

The hot feed crude oil is flashed in the fifth plate

Products:

- top distillate (IBP–140°C cut)

- straight run kerosene (140°C–270°C cut)

- straight run diesel (270°C–340°C cut)

- JBO (340°C–365°C cut)

- the bottom residue (RCO, 365°C +cut)

Crude Distillation UnitProduct stabilization

Crude Distillation UnitCondition parameter

Column PressureControlled by the back pressure of the overhead reflux drum

The top tray pressure is 0.4–0.7 bar gauge (6–10 psig) higher than the reflux drum

The flash zone pressure is usually 0.34–0.54 bar (5–8 psi) higher than the top tray

Overhead Temperaturemust be controlled to be 14–17 C (25–31 F) higher than the dew point temperature for the water to prevent water liquid condensation

Crude Distillation UnitCondition parameter

Crude Distillation UnitCrude material balance

Crude Assay Data

Crude Distillation UnitCrude material balance

Crude Assay Data PROPERTIES OF TBP CUTS

Cuts Yield YieldDen 15°C S RSH RON MON Napht. Aro. RVP

LIGHT °C wt% vol % kg/m3 wt% mg/kg clear clear vol% vol% kPa

NAPHTHA 15-65 3.52 4.52 644 0.0032 0 86.2 81.5 4.6 0.1 185.28

15-80 5.29 6.62 661 0.0037 1 86.1 81.2 9.9 0.3 150.93

Cuts Yield YieldDen 15°C S RSH Napht. Aro.

HEAVY °C wt% vol % kg/m3 wt% mg/kg vol% vol%

NAPHTHA 80-150 16.41 18.03 752 0.0081 2 32.2 11.3

80-175 22.45 24.29 764 0.0103 2 32.0 13.3

100-150 12.35 13.38 763 0.0090 2 32.9 14.5

Cuts Yield YieldDen 15°C S RSH Smoke Acidity Cetane Freez. Pt Aro. Visc cSt Flash

KEROSENE °C wt% vol % kg/m3 wt% mg/kg Pt mmmgKOH/

g Index °C vol% 50°C Point

150-230 21.72 22.08 813 0.029 2 16 0.08 35.6 -54 16.2 1.0 -

175-230 15.68 15.82 820 0.033 2 16 0.09 36.9 -50 15.1 1.2 -

150-250 27.87 28.16 818 0.034 2 16 0.09 37.9 -49 16.2 1.2 -

Cuts Yield YieldDen 15°C S Anilin Cetane Cloud Pt CFPP Pour Pt Visc cSt Visc cSt UOPK Flash

GASOIL °C wt% vol % kg/m3 wt% Point °C Index C C C 50°C 100°C Point

175-400 55.55 53.75 854 0.072 64 45.3 -6 -9 -12 2.5 1.2 11.7 -

230-400 39.86 37.93 869 0.088 68 48.1 -1 -1 -2 3.6 1.5 11.7 -

230-375 34.31 32.90 862 0.083 67 48.4 -7 -7 -8 3.1 1.4 11.7 -

Cuts Yield YieldDen 15°C S Conrad. Anilin Ni Va Total N Bas N Pour Pt Visc cSt Visc cSt UOPK Asp C7

VACUUM °C wt% vol % kg/m3 wt% wt% Point °C mg/kg mg/kg wt% mg/kg C 100°C 150°C wt %

DISTILLATE 375-550 17.84 15.73 937 0.15 0.5 80 0 0 0.027 102 41 6.1 2.5 11.6 0.1

375-565 18.53 16.31 939 0.15 0.8 80 0 0 0.031 110 41 6.6 2.7 11.6 0.1

375-580 19.09 16.77 941 0.16 1.2 80 0 0 0.041 117 42 7.0 2.8 11.6 0.2

400-580 13.54 11.74 953 0.18 1.7 81 0 1 0.052 152 47 10.1 3.7 11.6 0.2

Cuts Yield YieldDen 15°C S Conrad. Acidity Ni Va Total N Pour Pt Visc cSt Visc cSt Pene Asp C7

RESIDUE °C wt% vol % kg/m3 wt% wt%mgKOH/

g mg/kg mg/kg wt% C 100°C 150°C mm/10 wt%

> 375 20.77 18.11 948 0.17 4.2 0.3 1 2 0.179 34 9 3 587000 0.4

> 550 2.93 2.38 1020 0.32 26.5 0.4 5 15 1.100 48 869 74 199 2.0

> 565 2.24 1.80 1028 0.34 31.8 0.4 6 19 1.400 51 2470 145 124 2.4

> 580 1.68 1.34 1036 0.36 37.6 0.4 8 23 1.750 55 8420 321 91 2.7

This crude oil data sheet is for information purposes only. No guaranty is given as to its accuracy or as to any consequences arising from its use. TOTAL DTS / AM Mar-14

Crude Distillation UnitMaterial balance

Crude Distillation UnitSolution

Step 1: Construct fifth order polynomial fit of TBP data versus vol%


Step 2: From the end point of each cut, calculate the cumulative volume percent, example: the cumulative volume percent for the off gas and the light straight run naphtha is 1.33 and 8.6%, respectively


Step 3: Calculating average normal boiling point. The average normal boiling point for each cut is calculated at the mid percent of each cut.

in this case the light straight run naphtha is 1.33 + 7.27/2 or 4.965%Average boiling point - to be 43.6 C


Step 4: Calculating Molecular weight.


Step 5: Calculating specific gravity.

Crude Distillation UnitMaterial balance

Vacuum Distillation UnitProducts

Light vacuum gas oil (LVGO)

Medium vacuum gas oil (MVGO)

Heavy vacuum gas oil (HVGO)

Vacuum residue

Vacuum Distillation UnitProcess overview

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