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The visbreaking process simulation: products amount and their properties prediction
Compurers
Pergamon
0098-1354(95)ooo73-9
THE VISBREAKING
them. Engng
Vol. 19, Suppl., pp. S205-8210.1995 Coavrieht 0 1995 Elsevier Science Ltd Printed’ in &eat Britain. All rights reserved 0098-1354/95 $9.50 + 0.00
PROCESS SIMULATION: PRODUCTS AMOUNT AND THEIR PROPERTIES PREDICTION M. DENTE, G. BOZZANO, G. BUSSANI*
Politecnico di Milan0 - Chem. Eng. Dept. “G. Natta” - P.zza L. Da Vinci, 32 - Milan0 -Italy * K.T.I. S.p.A. - Via Ripamonti, 133 - Milan0 - Italy
ABSTRACT The visbreaking process is adopted by many refineries. It consists of a liquid phase pyrolysis of atmospheric or vacuum residues with the aim of increasing the production of light fractions and simultaneously reducing the viscosity of the visbroken residues. In spite of the economical importance of this operation, the literature is lacking of scientific informations; only empirical models have been presented. Major difficulties are constituted by the huge number of components and reactions that is characterising the system and by the relatively poor level of the available data for the feedstock characterisation. Due to the complexity of the feed to the reactor also the characterisation of the products properties, besides their amount, presents considerable problems. The results coming from a mechanistic approach are here presented. They are compared with experimental data from literature, research lab tests and commercial units. Moreover they are covering different aspects like fouling in the coils, effluents amounts and properties (residues stability, sulphur and asphaltenes content, viscosity, specific gravity, Conradson carbon residue and so on). The developed model constitutes a valid support for the understanding and prediction of the complex phenomena that are occurring during the HC liquid phase pyrolysis and can find a practical and important application both for improving the visbreaking furnaces design and for monitoring and control of the V.B. operations.
KEYWORDS Visbreaking; pyrolysis; fouling; residues stability
KINETICS
ASPECTS
Some of the rules and criteria followed facing on this problem are similar to those ones successfully adopted in an extended gas-phase pyrolysis kinetic scheme. The complexity of the molecular characterisation of these systems has been resolved (Dente et al., 1993) by lumping the huge number of real components into a relatively limited number of pseudo-components. For every pseudocomponent it has been proposed a specific reaction fate taking also into account the probability of scission of the different kind of bonds. The global kinetic mechanism is characterised by initiation, P-scission, H-abstraction, substitution and recombination reactions. Due to the liquid phase state, molecular rotational movements of the C-C segments are limited so that isomerization reactions of the radicals can be practically neglected. S205
s206
European Symposium on Computer Aided Process Engineering-5
The kinetic constants (frequency factors and activation energies) of the reactions involving paraffines, aromatics, olefines and diolefines, have been derived from the equivalent ones of an hypothetical equivalent gas phase (where consolidated rules are already available, Dente et al., 1992). The equivalent constants in the liquid phase have been obtained through correction factors of the activation entropies and activation energies for the transposition into the condensed state (Benson, 1960).
REACTOR MODELLING: THE PROBLEM OF FOULING The typical visbreaking reactor is constituted by long coils (generally two) horizontally placed in a furnace; where a radiant and a convective section can be distinguished. Often two cells, with independent heating, are present. Water is sometimes injected at the coil inlet to increase the fluid velocity, thus controlling the residence time. In the latest years in many plants an adiabatic extravolume , the so called soaker, has been added after the coils. It allows longer residence times and therefore lower coil outlet temperatures. As a consequence, the reduced fouling into the coils allows an extended on stream factor for the visbreaking unit. The fouling phenomena are an important aspect since, as said before, their are dictating the reactor on stream time. Their mechanisms of fouling formation are essentially two: a catalytic one and a radicalic one. When the tubes of the coil are relatively clean, as at start-of-run condition, the reactor metallic walls play the role of an heterogeneous polyaddition catalyst. Starting from vinylaromatic molecules, polymeric material is formed (like in conventional heterogeneous catalysis for poly-olefines, poly-diolefines, poly-styrenes and so on). The radicalic mechanism becomes more and more important as the wall surface is covered, increasing with temperature along the coil. The radicals that are involved in this phase are coming from the surroundings or are provided directly from the formed polymers (in fact the bonds of these complex molecular structures are weak at the beginning of the growth before crosslinking and dehydrogenation have taken place). The last radicalic mechanism, in combination with degradation, dehydrogenation and crosslinking of the formed polymers, gives place to the formation of more and more amorphous structures; the pure radicalic mechanism cannot be easily stopped with antifoulants agents. The theoretical experience gained in the modeling of fouling phenomena in Transfer Line Exchangers (TLE) in the ethylene production plants and the experimental data, confirm this phenomenological interpretation of the fouling mechanism. In fact, it is possible to observe a fast initial growth, due to the action of walls as catalyst, that subsequently slow down toward a quasiasymptotic behaviour. Coke only partially removed during decoking operation may hide the effect of the catalytic mechanism. The evolution of the coke layer thickness, of the pressure drop and of the maximum skin coil temperature resulting from simulations with the proposed model are shown in the following figures. The developed model seems to be satisfactory for the prevision of the named variables. However better comparisons and improvements of these features of the model can be obtained through the knowledge of the complete history of the furnace (in terms of variations of feedstocks and operating conditions). In fact the last variables influence the different growth rate of the coke layer. Qualitative and quantitative agreements with some commercial units data have been encouraging.
S207
European Symposium on Computer Aided Process Engineering-5
COIL+SOAKER ? r $j 5
0.006
.
0.005
.
COIL
COIL+SOAKER lD-
0
40
60
120
160
20
6O
200
40
60
DAYS
80
100
120
140
160
TIME (DAYS)
COIL+SOAKER
COIL DAY: 5 630 610. 590 -
0.0
0.1
0.2
o.,
0.4
0.5
0.6
0.7
0.6
6.9
i! TOTAL COIL LENGTH
1.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.6
0.9
1.D
Z TOTAL COIL LENGTH
PRODUCTS PROPERTIES A rigorous visbreaking simulation model cannot neglect the prediction of products properties like viscosity, specific gravity, sulphur and asphaltenes content, Conradson Carbon Residue and residue stability. The last one is the most important so that it is necessary to spend some words on it.
The asphaltenes and their stabilitv The asphaltenes are defined like those components that are precipitated by adding a certain amount of n-heptane to a residue (IP 143). This type of determination, being not founded on molecular basis, obviously gives place to determination errors.
S208
European Symposium on Computer Aided Process Engineering-S
Asphaltenes can be figured like polycatacondensed aromatic rings (the experimental H/C ratio confirm their aromatic nature) with short pa&ink side chain, whereas still can be defined as “aromatics” the same type of components with a longer side chain. During the pyrolysis the last ones are decomposed so that the content of asphahenes in the residue increases. The final mixture, constituted by “aromatics”, “asphaltenes”, olefines, diolefines and paraffines, is a typical colloidal solution. “Asphaltenes” can join and flocculate giving place to muds; this phenomenon limits the visbreaking severity so that the prediction of residue stability can be of real help in determining the best operating conditions. By now the most commonly accepted stability index is the “peptisation value” (PV): it is determined by adding to a certain amount of residue increasing quantities of cetane (Cl,) till the beginning of asphaltenes flocculation. Cetane is used in order to simulate the addition of the worst possible fluxant cutter stock to the residue. The preferred operating values to be maintained in v&breaking operations are in the range of 1.l-l .2. The problem of PV modelling can be approached by representing the system with three macroclasses of pseudo-components: “aromatics”, “asphaltenes” and “paraffines”, (the last grouping paraffines, olefines and diolefines). The Hildebrand method for the study of mixtures stability against separation, based on the determination of the mixing free energy minima in order to find the unmixing area, is very sensitive if applied to the considered system. The mixture can be considered as formed by two phases that are compatible only under certain conditions. The first one is constituted by “aromatics” and “paraf&es”, the latter by “aromatics” and “asphaltenes”. “Aromatics” are adsorbed on “asphahenes” so that the last ones are kept hidden to the “paraffines” with whom they are incompatibles. The coverage degree can be inferred (through the molecular structure of “aromatics” and that of “asphaltenes”) together with the critical concentration of “aromatics”, “parafIines” and “asphahenes” after their precipitation starts taking place. The coverage degree is also directly related to the sulphur content in the “asphaltenes”. In fact S atoms are larger than C atoms so that a major amount of “aromatics” is needed in order to assure “asphaltenes” coverage. The repartition constant of “aromatics” is given by the ratio between the activity coefficient of adsorbed “aromatics” and that present in the maltenic phase. The last one is correlated to the Hildebrand solubility parameters that has been obtained through the analysis of some experimental data available from literature (typically a group contribution method has been specifically developed for this problem). The results obtained by adopting this phenomenological approach, when compared with experimental data, are in a very good agreement, both in the prediction of the PV of the feedstocks and of the visbroken residues at different severity. Next figure presents the comparison between experimental and simulation data: the lines are showing the experimental average error in PV determination. Experimental data are referred to industrial plants, to research lab tests (priv. comm.) and to pilot plant (Di Carlo, 1992).
EXP. PV
European Symposium on Computer Aided Process Engineering-5
S2O!J
OTHER RESULTS AND COMPARISON The next figures shows the comparison between experimental and calculated effluent yields. The experimental data have been obtained by lab tests at different residence times and f&stocks (particularly the latter were characterised by different kinematic viscosity, specific gravity and sulphur content) at the same operating temperature. The comparison is very satisfactory.
0.5
0.7
0.0
1.1
1 3 1.5
1.7
1.0
2.1 2,
EXP. GASOLINE
EXP.CAS
14
.4 .:
13
EXP. LGO
EXP. HGO
94.
.,: 80
80
’
s 82
84
86
EXP. 350f
’ 88
90 RESIDUE
, 92
’ . 94 EXP. 500+
RESIDUE
Table 1 shows the comparison between experimental data and calculated effluent yields and products properties for some commercial cases. The first two cases are related to a coil plus soaker configuration of the reactor whereas the third one is typical of the same reactor without soaker.
s210
European Symposium on Computer Aided Process Engineering-5
Table 1 I
2
3
Inlet temp. “C Outlet temp. OC Outlet pressure bar Total residence time min
326 455 12 24 (with soak.)
330 450 12 26 (with soak.)
326 468 183 9
Kin. vise. at 100 “C cSt Kin. vise. at 120 “C cSt Asphaltenes wt% CCR W% Sulphur wt% Yield wt% HrS wt% TBP (“0 Specific gravity 15”/4”gkm3 Sulphur Wt% Yield Wt% Bromine Number TBP (“C) Specific gravity 15”/4”gkm3 Kin. vise. at 50°C cSt Kin. vise. at 70°C cSt Sulphur ti% Bromine number Yield wt% TBP (“C) Specific gravity 15”/4”&m3 Kin. vise. at 50°C cSt Kin. vise. at 70 “C cSt Sulphur wt% Bromine number Yield wt% TBP (“C) Specific gravity 15”/4”gkm3 Kin. visc.at IOO’CcSt P. value Sulphur wt% Asphaltenes wt% CCR wt% Yield wt% Yield Wt% Sulphur wt% Specific gravity 15”/4”g/cm3
2070 620 10.5 18.0 3.8 1.8 0.5 QOO 0.730 0.70 6.9 65 <315 0.85 2.0 1.4 1.9 33 7.1 c390
11.9 18.9 2.0 0.4 0.730 0.75 7.0 66
17.2 25.3 1.9 0.4 0.729 0.66 6.6 56
0.86 1.9 1.4 2.0 31 7.1 -
13400 2800 17 23 3.4 1.9 0.4 Cl95 0.738 0.65 6.8 51. Q90 0.85 1.9 1.3 2.1 29 5.0 <385
0.95
0.96
0.89
6.6 4.2 2.2 22 6.6 >305 1.04 530 1.15 3.7 20 24 84.9
7.2 4.6 3.1 23 6.9 500 1.11 3.7 19 22 83.9
5.8 3.9 2.5 21 7 >285 1.05 1414 1.27 3.2 25 27 87.0
1.07 1900 1.14 3.3 22 25 86.4
-
-
-
-
Vacuum Residues Operating Conditions
FEEDSTOCK
GAS
GASOLINE
E F F L U E N T
LGO
HGG
S
TAR+HGO
(39*!5: “C)
1.06
<340 0.86
8.0 15.4 1.8 0.3 0.74 0.93 4.0 66 0.88
2.0
2.4
9.1 <395
9.2 -
0.90
0.91
0.92
6.3 4.1 2.7 20 7.7
2.1 6.1 >510 1.06 1.2 3.8 17.5 61.6 17.2 2.4 0.94
-
0.86 1.8 1.3 1.8 32 5.1 -
1680 5.7 17.7 3.47 2.0 0.3 <175 0.73 0.78 3.9
2.6 6.2 1.06 1.3 3.6 17.8 61.5 17.2 2.6 0.94
REFERENCES Al So&I, Savaya, Z.F., Mohammed, H.K. and Al-Azawi, 1.A. (1988). Thermal conversion (visbreaking) of heavy Iraqi residue. Fuel, 67, 1714-1715. Benson, S.W. (1960).The Foundations of Chemical Kinetics, McGraw Hill, N.Y. Dente, M., Pierucci, S., Ranzi, E. and Bussani, G. (1992). New improvements in modeling kinetic schemes for hydrocarbons pyrolysis reactors. Chem.Eng.Sc.. 47, No.9-11, 2629-2634. Dente, M., Bozzano, G. and Rossi M. (1993). Reactor and kinetic modelling of the visbreaking process. Proceedings of First Conf. on Chem. and Proc. Eng.,l63-172 Di Carlo, S. and Janis,B. (1992). Composition and visbreakability of petroleum residues. Chem.Eng.Sc., 47, No.91l,June-Aug.1992, 2695-2700 Zimmerman, G., Dente, M. and Van Leeuwen, C. (1990). On the mechanism of the fouling, AIChE meeting, Orlando, FL, March 18-22.
Pergamon
0098-1354(95)ooo73-9
THE VISBREAKING
them. Engng
Vol. 19, Suppl., pp. S205-8210.1995 Coavrieht 0 1995 Elsevier Science Ltd Printed’ in &eat Britain. All rights reserved 0098-1354/95 $9.50 + 0.00
PROCESS SIMULATION: PRODUCTS AMOUNT AND THEIR PROPERTIES PREDICTION M. DENTE, G. BOZZANO, G. BUSSANI*
Politecnico di Milan0 - Chem. Eng. Dept. “G. Natta” - P.zza L. Da Vinci, 32 - Milan0 -Italy * K.T.I. S.p.A. - Via Ripamonti, 133 - Milan0 - Italy
ABSTRACT The visbreaking process is adopted by many refineries. It consists of a liquid phase pyrolysis of atmospheric or vacuum residues with the aim of increasing the production of light fractions and simultaneously reducing the viscosity of the visbroken residues. In spite of the economical importance of this operation, the literature is lacking of scientific informations; only empirical models have been presented. Major difficulties are constituted by the huge number of components and reactions that is characterising the system and by the relatively poor level of the available data for the feedstock characterisation. Due to the complexity of the feed to the reactor also the characterisation of the products properties, besides their amount, presents considerable problems. The results coming from a mechanistic approach are here presented. They are compared with experimental data from literature, research lab tests and commercial units. Moreover they are covering different aspects like fouling in the coils, effluents amounts and properties (residues stability, sulphur and asphaltenes content, viscosity, specific gravity, Conradson carbon residue and so on). The developed model constitutes a valid support for the understanding and prediction of the complex phenomena that are occurring during the HC liquid phase pyrolysis and can find a practical and important application both for improving the visbreaking furnaces design and for monitoring and control of the V.B. operations.
KEYWORDS Visbreaking; pyrolysis; fouling; residues stability
KINETICS
ASPECTS
Some of the rules and criteria followed facing on this problem are similar to those ones successfully adopted in an extended gas-phase pyrolysis kinetic scheme. The complexity of the molecular characterisation of these systems has been resolved (Dente et al., 1993) by lumping the huge number of real components into a relatively limited number of pseudo-components. For every pseudocomponent it has been proposed a specific reaction fate taking also into account the probability of scission of the different kind of bonds. The global kinetic mechanism is characterised by initiation, P-scission, H-abstraction, substitution and recombination reactions. Due to the liquid phase state, molecular rotational movements of the C-C segments are limited so that isomerization reactions of the radicals can be practically neglected. S205
s206
European Symposium on Computer Aided Process Engineering-5
The kinetic constants (frequency factors and activation energies) of the reactions involving paraffines, aromatics, olefines and diolefines, have been derived from the equivalent ones of an hypothetical equivalent gas phase (where consolidated rules are already available, Dente et al., 1992). The equivalent constants in the liquid phase have been obtained through correction factors of the activation entropies and activation energies for the transposition into the condensed state (Benson, 1960).
REACTOR MODELLING: THE PROBLEM OF FOULING The typical visbreaking reactor is constituted by long coils (generally two) horizontally placed in a furnace; where a radiant and a convective section can be distinguished. Often two cells, with independent heating, are present. Water is sometimes injected at the coil inlet to increase the fluid velocity, thus controlling the residence time. In the latest years in many plants an adiabatic extravolume , the so called soaker, has been added after the coils. It allows longer residence times and therefore lower coil outlet temperatures. As a consequence, the reduced fouling into the coils allows an extended on stream factor for the visbreaking unit. The fouling phenomena are an important aspect since, as said before, their are dictating the reactor on stream time. Their mechanisms of fouling formation are essentially two: a catalytic one and a radicalic one. When the tubes of the coil are relatively clean, as at start-of-run condition, the reactor metallic walls play the role of an heterogeneous polyaddition catalyst. Starting from vinylaromatic molecules, polymeric material is formed (like in conventional heterogeneous catalysis for poly-olefines, poly-diolefines, poly-styrenes and so on). The radicalic mechanism becomes more and more important as the wall surface is covered, increasing with temperature along the coil. The radicals that are involved in this phase are coming from the surroundings or are provided directly from the formed polymers (in fact the bonds of these complex molecular structures are weak at the beginning of the growth before crosslinking and dehydrogenation have taken place). The last radicalic mechanism, in combination with degradation, dehydrogenation and crosslinking of the formed polymers, gives place to the formation of more and more amorphous structures; the pure radicalic mechanism cannot be easily stopped with antifoulants agents. The theoretical experience gained in the modeling of fouling phenomena in Transfer Line Exchangers (TLE) in the ethylene production plants and the experimental data, confirm this phenomenological interpretation of the fouling mechanism. In fact, it is possible to observe a fast initial growth, due to the action of walls as catalyst, that subsequently slow down toward a quasiasymptotic behaviour. Coke only partially removed during decoking operation may hide the effect of the catalytic mechanism. The evolution of the coke layer thickness, of the pressure drop and of the maximum skin coil temperature resulting from simulations with the proposed model are shown in the following figures. The developed model seems to be satisfactory for the prevision of the named variables. However better comparisons and improvements of these features of the model can be obtained through the knowledge of the complete history of the furnace (in terms of variations of feedstocks and operating conditions). In fact the last variables influence the different growth rate of the coke layer. Qualitative and quantitative agreements with some commercial units data have been encouraging.
S207
European Symposium on Computer Aided Process Engineering-5
COIL+SOAKER ? r $j 5
0.006
.
0.005
.
COIL
COIL+SOAKER lD-
0
40
60
120
160
20
6O
200
40
60
DAYS
80
100
120
140
160
TIME (DAYS)
COIL+SOAKER
COIL DAY: 5 630 610. 590 -
0.0
0.1
0.2
o.,
0.4
0.5
0.6
0.7
0.6
6.9
i! TOTAL COIL LENGTH
1.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.6
0.9
1.D
Z TOTAL COIL LENGTH
PRODUCTS PROPERTIES A rigorous visbreaking simulation model cannot neglect the prediction of products properties like viscosity, specific gravity, sulphur and asphaltenes content, Conradson Carbon Residue and residue stability. The last one is the most important so that it is necessary to spend some words on it.
The asphaltenes and their stabilitv The asphaltenes are defined like those components that are precipitated by adding a certain amount of n-heptane to a residue (IP 143). This type of determination, being not founded on molecular basis, obviously gives place to determination errors.
S208
European Symposium on Computer Aided Process Engineering-S
Asphaltenes can be figured like polycatacondensed aromatic rings (the experimental H/C ratio confirm their aromatic nature) with short pa&ink side chain, whereas still can be defined as “aromatics” the same type of components with a longer side chain. During the pyrolysis the last ones are decomposed so that the content of asphahenes in the residue increases. The final mixture, constituted by “aromatics”, “asphaltenes”, olefines, diolefines and paraffines, is a typical colloidal solution. “Asphaltenes” can join and flocculate giving place to muds; this phenomenon limits the visbreaking severity so that the prediction of residue stability can be of real help in determining the best operating conditions. By now the most commonly accepted stability index is the “peptisation value” (PV): it is determined by adding to a certain amount of residue increasing quantities of cetane (Cl,) till the beginning of asphaltenes flocculation. Cetane is used in order to simulate the addition of the worst possible fluxant cutter stock to the residue. The preferred operating values to be maintained in v&breaking operations are in the range of 1.l-l .2. The problem of PV modelling can be approached by representing the system with three macroclasses of pseudo-components: “aromatics”, “asphaltenes” and “paraffines”, (the last grouping paraffines, olefines and diolefines). The Hildebrand method for the study of mixtures stability against separation, based on the determination of the mixing free energy minima in order to find the unmixing area, is very sensitive if applied to the considered system. The mixture can be considered as formed by two phases that are compatible only under certain conditions. The first one is constituted by “aromatics” and “paraf&es”, the latter by “aromatics” and “asphaltenes”. “Aromatics” are adsorbed on “asphahenes” so that the last ones are kept hidden to the “paraffines” with whom they are incompatibles. The coverage degree can be inferred (through the molecular structure of “aromatics” and that of “asphaltenes”) together with the critical concentration of “aromatics”, “parafIines” and “asphahenes” after their precipitation starts taking place. The coverage degree is also directly related to the sulphur content in the “asphaltenes”. In fact S atoms are larger than C atoms so that a major amount of “aromatics” is needed in order to assure “asphaltenes” coverage. The repartition constant of “aromatics” is given by the ratio between the activity coefficient of adsorbed “aromatics” and that present in the maltenic phase. The last one is correlated to the Hildebrand solubility parameters that has been obtained through the analysis of some experimental data available from literature (typically a group contribution method has been specifically developed for this problem). The results obtained by adopting this phenomenological approach, when compared with experimental data, are in a very good agreement, both in the prediction of the PV of the feedstocks and of the visbroken residues at different severity. Next figure presents the comparison between experimental and simulation data: the lines are showing the experimental average error in PV determination. Experimental data are referred to industrial plants, to research lab tests (priv. comm.) and to pilot plant (Di Carlo, 1992).
EXP. PV
European Symposium on Computer Aided Process Engineering-5
S2O!J
OTHER RESULTS AND COMPARISON The next figures shows the comparison between experimental and calculated effluent yields. The experimental data have been obtained by lab tests at different residence times and f&stocks (particularly the latter were characterised by different kinematic viscosity, specific gravity and sulphur content) at the same operating temperature. The comparison is very satisfactory.
0.5
0.7
0.0
1.1
1 3 1.5
1.7
1.0
2.1 2,
EXP. GASOLINE
EXP.CAS
14
.4 .:
13
EXP. LGO
EXP. HGO
94.
.,: 80
80
’
s 82
84
86
EXP. 350f
’ 88
90 RESIDUE
, 92
’ . 94 EXP. 500+
RESIDUE
Table 1 shows the comparison between experimental data and calculated effluent yields and products properties for some commercial cases. The first two cases are related to a coil plus soaker configuration of the reactor whereas the third one is typical of the same reactor without soaker.
s210
European Symposium on Computer Aided Process Engineering-5
Table 1 I
2
3
Inlet temp. “C Outlet temp. OC Outlet pressure bar Total residence time min
326 455 12 24 (with soak.)
330 450 12 26 (with soak.)
326 468 183 9
Kin. vise. at 100 “C cSt Kin. vise. at 120 “C cSt Asphaltenes wt% CCR W% Sulphur wt% Yield wt% HrS wt% TBP (“0 Specific gravity 15”/4”gkm3 Sulphur Wt% Yield Wt% Bromine Number TBP (“C) Specific gravity 15”/4”gkm3 Kin. vise. at 50°C cSt Kin. vise. at 70°C cSt Sulphur ti% Bromine number Yield wt% TBP (“C) Specific gravity 15”/4”&m3 Kin. vise. at 50°C cSt Kin. vise. at 70 “C cSt Sulphur wt% Bromine number Yield wt% TBP (“C) Specific gravity 15”/4”gkm3 Kin. visc.at IOO’CcSt P. value Sulphur wt% Asphaltenes wt% CCR wt% Yield wt% Yield Wt% Sulphur wt% Specific gravity 15”/4”g/cm3
2070 620 10.5 18.0 3.8 1.8 0.5 QOO 0.730 0.70 6.9 65 <315 0.85 2.0 1.4 1.9 33 7.1 c390
11.9 18.9 2.0 0.4 0.730 0.75 7.0 66
17.2 25.3 1.9 0.4 0.729 0.66 6.6 56
0.86 1.9 1.4 2.0 31 7.1 -
13400 2800 17 23 3.4 1.9 0.4 Cl95 0.738 0.65 6.8 51. Q90 0.85 1.9 1.3 2.1 29 5.0 <385
0.95
0.96
0.89
6.6 4.2 2.2 22 6.6 >305 1.04 530 1.15 3.7 20 24 84.9
7.2 4.6 3.1 23 6.9 500 1.11 3.7 19 22 83.9
5.8 3.9 2.5 21 7 >285 1.05 1414 1.27 3.2 25 27 87.0
1.07 1900 1.14 3.3 22 25 86.4
-
-
-
-
Vacuum Residues Operating Conditions
FEEDSTOCK
GAS
GASOLINE
E F F L U E N T
LGO
HGG
S
TAR+HGO
(39*!5: “C)
1.06
<340 0.86
8.0 15.4 1.8 0.3 0.74 0.93 4.0 66 0.88
2.0
2.4
9.1 <395
9.2 -
0.90
0.91
0.92
6.3 4.1 2.7 20 7.7
2.1 6.1 >510 1.06 1.2 3.8 17.5 61.6 17.2 2.4 0.94
-
0.86 1.8 1.3 1.8 32 5.1 -
1680 5.7 17.7 3.47 2.0 0.3 <175 0.73 0.78 3.9
2.6 6.2 1.06 1.3 3.6 17.8 61.5 17.2 2.6 0.94
REFERENCES Al So&I, Savaya, Z.F., Mohammed, H.K. and Al-Azawi, 1.A. (1988). Thermal conversion (visbreaking) of heavy Iraqi residue. Fuel, 67, 1714-1715. Benson, S.W. (1960).The Foundations of Chemical Kinetics, McGraw Hill, N.Y. Dente, M., Pierucci, S., Ranzi, E. and Bussani, G. (1992). New improvements in modeling kinetic schemes for hydrocarbons pyrolysis reactors. Chem.Eng.Sc.. 47, No.9-11, 2629-2634. Dente, M., Bozzano, G. and Rossi M. (1993). Reactor and kinetic modelling of the visbreaking process. Proceedings of First Conf. on Chem. and Proc. Eng.,l63-172 Di Carlo, S. and Janis,B. (1992). Composition and visbreakability of petroleum residues. Chem.Eng.Sc., 47, No.91l,June-Aug.1992, 2695-2700 Zimmerman, G., Dente, M. and Van Leeuwen, C. (1990). On the mechanism of the fouling, AIChE meeting, Orlando, FL, March 18-22.