(Microsoft Word - 103-109 \323\341\355\343)


Al-Khwarizmi Engineering Journal,Vol. 13, No. 1, P.P.  

 

Preparation of Light Fuel Fractions 

by Thermal Cracking Reaction

Saleem
Department of Chemical Engineering/

Email:

(Received 2  

https://doi.org/10.22153/kej.2017.11.003 

Abstract 

This work deals with thermal cracking of heavy vacuum gas oil which produced from the top of vacuum 

distillation unit at Al- DURA refinery, by continuous process. An experimental laboratory plant scale was 

constructed in laboratories of chemical engineerin

The thermal cracking process was carried out at temperature ranges between 460

with liquid hourly space velocity (LHSV) equal to 15hr

distilled by atmospheric distillation device according to ASTM D

as a gasoline fraction and above 220
o
C as light cycle oil (LCO).

fractionated to light fractions (gasoline, kerosene and gas oil) by atmospheric distillation device.

(gasoline, kerosene and gas oil) were distilled by atmospheric distillation device in order to obtained distillation 

curve for these fractions. Physical properties

in order to studying the possibilities of industrial uses.

obtained by this process equal to 82 wt. %

Keywords: light fuel, thermal cracking, heavy vacuum

 

 

1. Introduction 
 

Vacuum gas oil is a part of petroleum 

hydrocarbon heavy distillate family.

distillation recovers gas oil from the residual oil; 

in a vacuum tower so that the boiling point 

temperature is reduced, this allows distillation at 

temperatures that are not possible in 

atmospheric distillation. 

The thermal cracking unit is consisting

scission of the hydrocarbon C–C bonds present 

in the feedstock. It is occurring 

temperature is raised (400-900)
 o 

C to a point at 

which the bonds that hold a molecule together 

are broken. Cracking reaction start to occur at a 

temperatures of about (315-370)
 o 

C,

on the hydrocarbon nature of the material being 

cracked, feed stock type and product 

requirement. 

  

Khwarizmi Engineering Journal,Vol. 13, No. 1, P.P. 103- 109 (2017)

 

Light Fuel Fractions from Heavy Vacuum Gas Oil 

Thermal Cracking Reaction 
 

Saleem Mohammed Obyed 
Engineering/ Collage of Engineering / Al-Nahrain University

Email:Saleem_mo71@yahoo.com 

 
23 May 2016; accepted 29 November 2016)

https://doi.org/10.22153/kej.2017.11.003

 

 
This work deals with thermal cracking of heavy vacuum gas oil which produced from the top of vacuum 

DURA refinery, by continuous process. An experimental laboratory plant scale was 

constructed in laboratories of chemical engineering department, Al-Nahrain University and Baghdad University. 

The thermal cracking process was carried out at temperature ranges between 460-560
o
C and atmospheric pressure

with liquid hourly space velocity (LHSV) equal to 15hr
-1

.The liquid product from thermal cracking unit was 

distilled by atmospheric distillation device according to ASTM D-86 in order to achieve two fractions, below 220

C as light cycle oil (LCO).The first fraction which was 

fractionated to light fractions (gasoline, kerosene and gas oil) by atmospheric distillation device.

(gasoline, kerosene and gas oil) were distilled by atmospheric distillation device in order to obtained distillation 

Physical properties were recorded for these cuts to compare it with standard

in order to studying the possibilities of industrial uses. The maximum conversion of heavy vacuum gas oil was 

obtained by this process equal to 82 wt. % of feed at 540
o
C. 

heavy vacuum ,gas oil. 

gas oil is a part of petroleum 

family. Vacuum 

distillation recovers gas oil from the residual oil; 

in a vacuum tower so that the boiling point 

temperature is reduced, this allows distillation at 

temperatures that are not possible in 

consisting of the 

C bonds present 

occurring when the 

C to a point at 

a molecule together 

Cracking reaction start to occur at a 

, depending 

of the material being 

feed stock type and product 

Treatment in any thermal process results in 

the formation of gases, gasoline

distillate fractions (kerosene and gas oil

residual fractions, and coke.  

The yield, relation between the reaction 

product's and the properties of these products 

depend on many factors, but the main role is 

played by the composition of the feed stock, the 

temperature, pressure and duration

reaction. [1] 

The rate of a reaction grows with elevation 

of the feed stock boiling point. Feed stock 

containing mainly alkanes is preferable for 

thermal cracking plants because they 

decompose more readily with the formation of 

target products such as gas, gasoline, and 

middle distillate, as the same time a little coke 

forms. 

The degree of conversion in the thermal 

cracking is characterized by the gasoline yield 

 

    
Al-Khwarizmi 

  Engineering  

Journal 

Heavy Vacuum Gas Oil 

Nahrain University 

  

This work deals with thermal cracking of heavy vacuum gas oil which produced from the top of vacuum 

DURA refinery, by continuous process. An experimental laboratory plant scale was 

and Baghdad University. 

C and atmospheric pressure 

al cracking unit was 

86 in order to achieve two fractions, below 220
o
C 

 below 220
o
C was 

fractionated to light fractions (gasoline, kerosene and gas oil) by atmospheric distillation device. The fractions 

(gasoline, kerosene and gas oil) were distilled by atmospheric distillation device in order to obtained distillation 

were recorded for these cuts to compare it with standard property test, 

The maximum conversion of heavy vacuum gas oil was 

Treatment in any thermal process results in 

gasoline, middle 

distillate fractions (kerosene and gas oil), heavy 

The yield, relation between the reaction 

product's and the properties of these products 

depend on many factors, but the main role is 

played by the composition of the feed stock, the 

temperature, pressure and duration of the 

The rate of a reaction grows with elevation 

of the feed stock boiling point. Feed stock 

containing mainly alkanes is preferable for 

thermal cracking plants because they 

decompose more readily with the formation of 

as gas, gasoline, and 

middle distillate, as the same time a little coke 

The degree of conversion in the thermal 

cracking is characterized by the gasoline yield 



Saleem Mohammed                  Al-Khwarizmi Engineering Journal, Vol. 13, No. 1, P.P. 103- 109 (2017) 

 

 

104 

relative to the feed stock. The degree of 

conversion is limited by the formation of coke 

and gas. The coke yield grows with increasing 

temperature and residence time of the stock in 

the reaction zone. [2]. 

Elevation of the cracking temperature at a 

constant pressure and constant degree of 

conversion leads to an increase in the constant 

of light components and to a reduction in the 

yield of heavy fractions and coke. [3] 

The feed stock consists of a large number of 

individual componentsso, it is impossible to 

predict or follow the fate of each of these 

components under the action of high 

temperatures.  

The aim of this work study the thermal 

cracking reaction of heavy vacuum gas oil at a 

temperature ranges (460-560)
 o 

C and tested 

some major physical and chemical properties of 

light product fractions to compare it with 

standard property test, in order to studying the 

possibilities of industrial uses. 

 
 

2. Experimental Work  
Materials  

 

Heavy vacuum gas oil which produced from 

top of vacuum distillation unit in Al -Dura 

refinery was used as feedstock in this study. The 

properties of heavy vacuum gas oil were 

determined by laboratory of AL-Dura refinery, 

as shown in Table 1. 

 
Table 1,  

Physical and chemical properties of vacuum gas 

oil sample. 

Characteristics Value 

Viscosity (40
 0

C) 48 C.st 

Flash point (open cup) 110
 0

C 

PH 7 

Color brown 

Melting point / freezing point >15
 0

C 

Initial boiling point and 

boiling range 

306-532 
0
C 

Vapor pressure 0.01 kpa. 20 
0
C 

Relative density 0.9 

Auto-ignition temperature >220 
0
C 

Specific gravity 0.91 

 

 

 

 

 

 

 

 

3. The Experimental Work Units 
  

The desired quantity of HVGO(6300 ml/hr.) 

pumped by dosing pump at the desired flow to 

the evaporator. In the evaporator the feed heated 

to 330
o
C, and then enters the reactor, its volume 

was (420 ml). 

The reactor temperature was measured by 

thermocouples. The product discharged to the 

condenser section, where the condensates are 

collected, for all runs in various operating 

temperature. The uncondensed gases are 

collected in gas collector. The duration time for 

each experiment was 30 minute. 

Fig. (1) Shows the fixed bed reactor unit 

where experiments which took place at 

temperature range 460-560
o
C and liquid hour 

space velocity 15hr
-1

. 

Fig. (2) Shows the distillation unit of 

cracking liquid products which were achieved in 

atmospheric distillation unit which consist of 

heater and condenser according to (ASTM D-

86) for light cuts. 

 

 
 

Fig. 1. Photograph picture of the fixed bed reactor 

unit. 

 

 
 

Fig. 2. ASTM D-86 distillation unit. 

 

 

 

 



Saleem Mohammed                  Al-Khwarizmi Engineering Journal, Vol. 13, No. 1, P.P. 103- 109 (2017) 

 

 

105 

 

 
 

Fig. 3. Schematic flow diagram of laboratory continuous cracking unit. 

1-Feed reservoir: 2- Dosing pump; 3-Preheater; 4- One way valve; 5- Reactor system; 6- Temperature 
controller; 7- Condenser; 8- Flow meter; 9- Control valves; 10- Separator; 11- Cooling machine.  

 

4. Results and Discussion 
4.1. Effect of Temperature on Thermal 

Cracking Reaction 
 

The effect of temperature ranges (460-

560)°C on the heavy vacuum gas oil conversion 

and the yield of gases, gasoline, light cycle oil 

and coke that were studied at constant liquid 

hour space velocity (LHSV)15hr
1
were shown in 

Table 2. 

 

 
Table 2, 

Effect of temperature on liquid products from thermal cracking of heavy vacuum gas oil. 

560 540 500 460 Temperature 
o 

C  

15 15 15 15 Liquid hour space velocity hr
-1

  

82 81 77.5 75.6  Conversion wt.%  

52 52 51 49  Gasoline wt.% 

18 19 22.5 24.4 

   
  

Light cycle oil (LCO)wt.%  

70  71 73.5 73.4 Total liquid product wt.%  

3.4 3 2.6 2 Coke wt.%  

24 22 18 15 Gases wt.%  

1.6  2 5.9  5.4 Residue wt.%  

1 2 3.5 4.2 Losses  

 

 

Figure 4 shows the effect of temperature 

ranges (460-560) ° C on the heavy vacuum gas 

oil conversion by thermal cracking. As shown 

from this figure the heavy vacuum gas oil 

conversion increases with increasing 

temperature. This may be attributed to; the 

increase of temperature which accelerates 

intermolecular motions assists the 

transformations of the reactants into new 

compounds and thus enhances the rate of 

chemical reaction, as mentioned also by 

Decroopcq [4]. 

 

 
 
Fig. 4. Effect of temperature on conversion of 

thermal cracking of heavy vacuum gas oil. 

 

 



Saleem Mohammed                  Al-Khwarizmi Engineering Journal, Vol. 13, No. 1, P.P. 103- 109 (2017) 

 

 

106 

Fig. (5) and fig. (6) Shows the yield of gases 

and gasoline respectively. The gasoline yield is 

chiefly affected by gas formation.  

The increasing in the temperature reaction 

firstly increases the gasoline yield, then higher 

temperature gives lower gasoline yield and 

higher gases yield, this due to cracking gasoline 

itself to lighter fractions so the best temperature 

of thermal cracking of HVGO is 540 °C for this 

reason. 

 

 
 

Fig. 5. Effect of temperature on gases yield by 

thermal cracking of HVGO. 

 

 
 

Fig. 6 .Effect of temperature on gasoline yield by 

thermal cracking of HVGO.  

 

 

Fig.(7) and fig. (8) Shows that the yield of 

light cycle oil (LCO) decreases by temperature 

increasing and slightly increases in coke yield 

respectively. 

 

 

 
  

Fig. 7. Effect of temperature on light cycle oil 

yield by thermal cracking of HVGO. 

 

  
 

Fig. 8. Effect of temperature on coke yield by 

thermal cracking of HVGO. 

 

 

Fig. (9) Shows the thermal cracking products 

distribution at different temperatures ranges 

(460 – 560) ºC and constant LHSV. 

 

 
 

Fig. 9. Effect of temperature on thermal cracking 

products yield from HVGO. 

 

 

The increasing in the reaction temperature 

firstly increases the gasoline yield then higher 

560 °C temperature gives lower gasoline yield 

and higher gases yield, (figures 6 and figure 5). 

Since the conversion increases with temperature 

increasing, the light cycle oil decreases by 

temperature increasing at constant LHSV as 



Saleem Mohammed                  Al-Khwarizmi Engineering Journal, Vol. 13, No. 1, P.P. 103- 109 (2017) 

 

 

107 

 

shown from figure 7. And slightly decreases in 

coke yield (figure 8). 

 Clear pictures for thermal cracking products 

distribution at different temperatures ranges 480 

- 540 ºC and constant LHSV were presented at 

figure 9. 

The above results agreed with those obtained 

by Reagan [5]. 

 

 

4.2. The atmospheric distillation results 
4.2.1. Heavy Vacuum Gas Oil 

 

The results of atmospheric distillation for 

heavy vacuum gas oil and true boiling point 

distillation (TBP)were tabulated in table 3 

which used to calculate some physical 

properties after calculate the mean average 

boiling point .  

 

Table 3  

Results of ASTMD-86 and TBP distillation for heavy vacuum gas oil. 

 

  

4.2.2. Light Fractions 

 

The results of atmospheric distillation for 

light fractions (gasoline, kerosene and gas oil) 

according to ASTM–D86were tabulated in table 

4which used to calculate some physical 

properties after calculate the mean average 

boiling point for any fraction.   

 
Table 4,  

Results of ASTM D-86 distillation for (gasoline, kerosene and gas oil) 

ASTM D-8 (
o 
C ) gas oil  ASTM D-86 (

o 
C ) kerosen  ASTM D-86 (

o 
C ) gasoline  Volume  %  

195  135  44  Initial boiling point  

215  170  57  5  

230  178  63  10  

247  176  73  20  

259  190  82  30  

262  197  92  40  

279  205  103  50  

289  210  116  60  

299  216  130  70  

309  228  150  80  

329  241  180  90  

  258  195  95  

  

 

T.B.P (
o 
C )  T.B.P (

o 
R )  ASTM D-86 ( 

o 
R )  ASTM D-86 (

o 
C ) Volume% 

63  606 654 90  0 

253 948 942  250    5 

259  959  978  270  10  

270 978 989  276  15  

280 996 996  280  20  

296  1040  1032  300  25 

304 1040 1043  306  30 

310 1051 1050  310  35 

318 1065 1061  316  40  

322 1073 1068 320  45  

327  1080  1072  322  50  

332 1090 1079  326  55  

339 1103 1086  330  60  

342 1107 1090  332  65  

348  1118  1097  336  70  

352 1127 1097  336  75  

358 1137 1100  338  80  

362 1145 1111  344  85  

365  1150  1122  350  90  

383  1181  1149  365  95  

390 1194 1158  370 100  



Saleem Mohammed                  Al-Khwarizmi Engineering Journal, Vol. 13, No. 1, P.P. 103- 109 (2017) 

 

 

108 

 

5. The Physical and Chemical Properties 

of Fractions  
 

Table 5 shows the properties for light 

fractionswhich were produced from distillation 

of liquid thermal cracking for heavy vacuum gas 

oil, to compared it with standard property for 

the same fraction, in order to possibility 

commercial uses these fractions. 

 

Table 5,  

The results of physical properties for (gasoline, kerosene and gas oil). 

Property 

Type of fraction which were produced 

from liquid thermal cracking of VGO 
standard property for fraction 

gasoline kerosene Gas oil gasoline kerosene gasoil 

Specific gravity. 0.77 0.81 0.85 0.72-0.77 0.77-0.82 0.82-0.86 

API gravity. 85 48 44 50-60 40-50 35-45 

�� (ºR) 640 870 975    
K-index 12 12.2 12.3 11-13 11-13 11-13 

Molecular weight. 93 167 214 115 170 225 

Flash point(ºk) 300 310 325 Min.327 Min.315 Min.305 

Diesel Index. 90 61 73    

Aniline point (ºC) 67 70 72 60 65 70 

Viscosity at 100 ºF (Cst.) 0.5139 1.3238 2.511 0.6 1.6 Max.5.6 

refractive 

index 

Experimental 1.4104 1.435 1.4456    
Empirical 1.4395 1.456 1.4877    

Pour point (ºk) 165 246 218 Max.264 Min.220 Min.160 

Smoke point (mm) 
 

23 
  

Min.21 
 

 
6. Conclusion  

 
1- It was concluded that the possibility produced 

of light fractions (gasoline, kerosene, gas oil) 

from heavy vacuum gas oil by thermal 

cracking process at different temperatures and 

constant space velocity at atmospheric 

pressure. 

2- It was concluded that the heavy vacuum gas oil 
conversion increases with increasing the 

temperatures of thermal cracking. 

3- Possibilty uses these light fractions for internal 
combustion engine or for domestic usesand 

diesel fuel. 
  

 

7- References 

 
[1] Alkilani.A.  Haitham M. S. Taher A. AL-

Sahhaf "fundamental of petroleum 

refining", (2010) 

[2] Pillion L. Z, interfacial properties of 
petroleum products, by Tayler& Francis 

Group, LLC, (2005). 

[3] Levenspiel, O., "Chemical reaction 
engineering" John Wiley and Sons Inc.3ed 

(1999).  

[4] Denial Decroopcq “Catalytic Cracking Of 
Heavy Petroleum Fractions”, Paris (1984). 

[5] Reagan, W.J., U.S. Department of Energy, 

Pittsburgh Energy Technology Center, 

Liquefaction Conttractors' Review, 

Conference Proceedings, September, 1992, 

Pittsburgh, PA., 261-290. 

[6] Speight, J.G. "The Chemistry and 
Technology of Petroleum,",3

rd
 ed. Marcel 

Dekker, New York (1999). 

[7] BhaskaraRao B.K. "Modern Petroleum 
Refining Processes" 4

th
 ed. Indian Institute 

of Technology. (2004) 

[8] Speight, J.G. "Hand book of petroleum 
product analysis", USA. (2002) 

[9] Alan G. Lucas "Modern Petroleum 
Technology", Vol.2 Downstream New 

York 2001. 

[10] Lappas, A. 2
nd

 European summer school on 

renewable motor fuels Warsaw, Poland 

(2007). 

 

 



 )2017( 103-109، ?<+3 1، ا1>&د13&3.0 ا9:1ارز,6 ا451&/'3 ا1*0.,                                                         /.'- ,+*& ()'&

 

109 

 

 

 

 

 
,V زTU اES1ز اG>1ا6R ا9P N'FQ1ا/N)E>I 3O اG'KLM1 اG+1اري EF, G'H+I3طC و9Aد @<'<  

 

&'() &*+, -'./  

��� ا	�����  /ا	���������  / �ا	����
و� ا	�������� �  

Saleem_mo71@yahoo.com ����	و�� ا���	�:ا  
  

  

  

3?W:1ا  
  


ول ھ�ا ���8 رة، و�� ا	6)ء ا	��4ي �� و�3ة ا	�,��2 ا	*�ا(� �1 �0*
ة ا	� ا	�ي ���. � ا	-,�+*�ا(ا	)�' ا	&
ز ا	����� ا	"�اري 	 ا	�"!�
���ة ;���� �3اري ����8 ط��9��.- ���� ��>��4 ;� ;���0 و;�*�=�>� �����6; ��?
���ات ��� ا	����� ا	����=� �1 �1  ���

��� ا	����� و��

دي وا	I&J ا	46ي ٥٦٠oC- �3٤٦٠ارة ;��اوح ��B �1 ���ل در�� و�� أ���' ����8 ا	����� ا	"�اري  .B&�اد��8�
 اJ*	�8 ا�� K���? 

)LHSV ( وي
�;١٥
�
��

.  -  �;?

ا	���. �� و�3ة ا	����� ا	"�اري 4B +;,��2 ا	�� �*M4ا��	 
��  ASTM D-86ط� ��
ز ا	�,��2 ا	46ي ط�,

م٢٢٠ ;"'، �,���2أ�+ ;",�9 
°

  
�2,� >*M4B	 و41ق ��م���٢٢٠)
°

  >*M4B�
ز� *�*Q
اSول ا	�ي �
ن ;"'  ء;,��2 ا	LCO.( -  �;(6( ��ور 

م٢٢٠
°

  T	إKط

ز ا	�,��2 ا	46ي �8 ط��9) ا	��)�� وا	���و��� وز�' ا	&
ز(ا	=*�*�  ا	�,��. -  V	�ا	��)�� وا	���و��� ( 	�,
طKا	�,��2,;  �2 ;��
�ه  ا	�ي ;� ا	"40ل T�"��>��8 ا	�,��2 ر�� �� WQل ��
ز ا	�,��2 ا	46ي �� أ�+ ) وز�' ا	&
ز�	Kط

ب ���ل در�� ا	&��
ن 	��ه  ا	�,�"	 V	وذ

Kط
�3
ب  .ا	�,[?

ت �B\ ا	=0*M4ا�	وا  ��?
ا	��84، �,�2 ا	��4\، �,�2 ا�����S،  ا	4زندر�� ا	&��
ن، ��I�4 (�-+  ا	����ا	*�)�
?�� وا	����

ن، ا	4زن ا	6)�[�Q�	�2 ا,� (V	وذ 	 K� 
��
ت �,
ر�*M4ا�	ا���
6
ر�� ا	,���=�ا�
ت ا	�0
��8ا��� أ�+ در ا	��
ت ا��
;� ا	"40ل T�8  .� إ��


	4زن ٨٢إ	T  �0+�� ھ�ه ا	�����  �أ�T0 ��ر �� ;"4�+ ز�' ا	&
ز ا	-,�+ ا	*�ا(B . ٪��8م.٥٤٠
°