7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
1/24
Accepted Manuscript
Title: Kinetic Studies and Reactor Modeling of Single StepH2S Removal Using Chelated Iron Solution
Authors: A. Karimi, A. Tavassoli, B. Nasernezhad
PII: S0263-8762(09)00307-4
DOI: doi:10.1016/j.cherd.2009.11.014
Reference: CHERD 415
To appear in:
Received date: 20-5-2009Revised date: 7-11-2009
Accepted date: 21-11-2009
Please cite this article as: Karimi, A., Tavassoli, A., Nasernezhad, B., Kinetic Studies
and Reactor Modeling of Single Step H2S Removal Using Chelated Iron Solution,
Chemical Engineering Research and Design (2008), doi:10.1016/j.cherd.2009.11.014
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production processerrors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.
http://localhost/var/www/apps/conversion/tmp/scratch_7/dx.doi.org/doi:10.1016/j.cherd.2009.11.014http://localhost/var/www/apps/conversion/tmp/scratch_7/dx.doi.org/10.1016/j.cherd.2009.11.014http://localhost/var/www/apps/conversion/tmp/scratch_7/dx.doi.org/10.1016/j.cherd.2009.11.014http://localhost/var/www/apps/conversion/tmp/scratch_7/dx.doi.org/doi:10.1016/j.cherd.2009.11.0147/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
2/24
Page 1 of 23
Accepted
Manus
cript
1
Kinetic Studies and Reactor Modeling of Single Step H2S
Removal Using Chelated Iron Solution
A. Karimi
1
, A. Tavassoli
1
, B. Nasernezhad
2
1Gas Research Division, Research Institute of petroleum industry (RIPI)
[email protected] Engineering Department, Amir Kabir University
Abstract
Airlift reactor concept was used for hydrogen sulfide removal from acid gases using
chelated iron solution. Rate equations for absorption and regeneration reactions
were determined and finally, an Autosweet program was developed for design and
simulation of the reactor. Variations of the concentration profiles of the reactants
and products with time, the required time to achieve steady state conditions,
concentration profiles of two phases at steady state and volume of the reactor in
absorption and regeneration sections can be calculated based on implemented model
in this study. Comparison of theoretical and experimental results shows a good
agreement and justifies the model. Based on the model as a second stage of project,
a 1 m3 prototype reactor was designed and constructed at NIOC research institute.
Keywords: kinetics, modeling, airlift, chelated iron, hydrogen sulfide
Introduction
Liquid phase oxidation process using iron chelate catalytic solution (LOCAT) has
been employed for treatment of acid gas streams. However, the process was
identified economical for up to 850-1050 kg/hr of sulfur production, although much
larger systems have been installed [1]. Advantages of these systems include the
ability to treat both aerobic and non-aerobic gas streams, high H2S removal
anuscript
mailto:[email protected]:[email protected]:[email protected]7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
3/24
Page 2 of 23
Accepted
Manus
cript
2
efficiencies, great flexibility; essentially 100% turndown on H2S concentration in
feedstock, and quality and the production of innocuous products and byproducts.
The two most common processing schemes encountered in these systems are named
"Conventional" and "Autocirculation". The first one is employed for processing gas
streams, which are either combustible or cannot be contaminated with air. Here,
absorption and regeneration reactions occur in separate vessels. The second one is
used for processing acid gas streams (CO2 and H2S) or noncombustible streams in
which both absorption and regeneration reactions are carried out in a single vessel
according to the following equations respectively:
H2SFe2Fe2SH 232 (1)
OH2Fe2O2
1Fe2OH 32
2
2 (2)
The overall reaction is the reaction given in equation (3):
SOHO2
1
SH 222 (3)
The autocircualtion scheme of the reactor is illustrated in Fig. 1. The reactor
consists of three main zones; riser, downcomer and gas-liquid separator. In riser
both absorption and regeneration reactions take place. In the initial section of the
riser, in which the reaction of equation (1) occurs, acid gas is sparged and absorbed
into a catalytic solution. Then, the solution flows in regeneration section in which
air is sparged where the reaction of equation (2) occurs. The solution circulates due
to density difference created between riser and downcomer zones. As seen in Fig.
1, the two spargers for acid gas and air are placed in an appropriate flexible distance
to each other. The regenerated catalytic solution re-enters to the riser absorption
zone due to the presence of the natural circulation.
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
4/24
Page 3 of 23
Accepted
Manus
cript
3
In comparison with the conventional scheme, the unique feature of the
autocirculation reactor is that no pumps are required to circulate solution between
absorber and oxidizer. Therefore, these are generally less expensive units with few
operational problems related to sulfur plugging than usually reported for the other
scheme. However, due to presence of oxygen and sulfide ions, these units may
produce more byproducts.
Hydrodynamic parameters of this scheme such as gas hold up, liquid velocity,
pressure distribution and bubble diameter were determined in another work [2]. The
main objective of this paper is to determine reaction kinetic parameters for both
absorption and regeneration reactions and then presenting a model to simulate the
reactor behavior using airlift reactor concept which is commonly used for
fermentation or bio-reactions.
In fact, a little information concerning kinetic data has been revealed in the
literature. The absorption reaction between H2S and catalytic solution is fast and as
soon as H2S reaches to interface plane, the absorption reaction takes place between
two phases [3]. The method of how to measure the kinetics parameters and how to
imply an appropriate model interpreting the experimental data is very important for
determination of rate constant and the other required parameters. In addition the
literature shows a great controversy regarding kinetics parameters. The
investigations commonly confirm that the regeneration reaction can be considered
first order with respect to the oxygen concentration, [4, 5, 6] but there are different
information can be found regarding the order of reaction with respect to the chelated
iron II concentration. For example, Sada et al. reported this order equal to 0.536
[4], however, the other investigators reported it to be mostly equal one andtwo [5].
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
5/24
Page 4 of 23
Accepted
Manus
cript
4
Reviewing some papers shows that the order varies between one and two when pH
and concentration of chelated iron solution change.
Here, an experimental investigation is performed to determine rate equations for
RIPI20*, iron chelate catalytic solution (i.e. Fe-EDTA complex), and a model is
developed to predict variations of the concentration of the reactants and products
with time. The Autosweet program is also developed to estimate the time needed
to steady state conditions, concentration profile of two phases at steady state and
volume of the reactor needed to take place the absorption and regeneration reactions
within the safe zone operation and for a given condition. Experimental data obtained
from a bench scale reactor are in a good agreement with simulated reactor using the
program.
Experimental Setup
Kinetic experiments were carried out in a glass reactor illustrated in Fig. 2. The
reactor has 10 cm diameter and 20 cm height in which gas and liquid can be
contacted. Both phases are well mixed via two impellers located at two positions in
the bulk of gas and liquid on the agitator shaft. The agitator speed in all
experiments is constant and equal to 300 rpm. Six baffles, 1 cm in width, are placed
symmetrically to avoid the formation of vortex inside the reactor and make agitation
to take place completely.
Variations of iron concentration and dissolved oxygen in liquid phase are measured
and saved using an oxidation-reduction probe (ORP) and a DO electrode. Depending
Variations of iron concentration and dissolved oxygen in liquid phase are measured
and saved using an oxidation-reduction probe (ORP) and a DO electrode. Depending
on the purpose of experiment the electrodes are connected to a PentiumII personal
*RIPI20 is formulated by RIPI
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
6/24
Page 5 of 23
Accepted
Manus
cript
5
computer for data acquisition. Containers, V2, V3 and V4, are dry nitrogen,
hydrogen sulfide and air cylinders, respectively. A vacuum pump is used for
evacuation of the reactor and charging the catalytic solution from container V 6. Off
gases from the reactor can be gathered in vessel V5.
Absorption reaction kinetics
The reaction mechanism is as follows:
)L(2)aq(2)L(2)g(2 OHSHOHSH (4)
HSHSH )aq(2 (5)
HFe2SFe2HS 23 (6)
Equations (4) and (5) represent the absorption of H2S into the aqueous chelated iron
solution and its subsequent ionization, while equation (6) represents the oxidation of
the sulfide ions to elemental sulfur and the accompanying reduction of the ferric
iron to the ferrous state. The overall absorption reaction follows equation (1).
Writing the intrinsic rate equation in the power form yields:
1
3
1
2
2
2
m
Fe
n
SH1
SH
SH C.CKdt
dCr
(7)The aim here is to determine values of n1, m1 and K1. According to the following
equation, absorption rate of H2S in liquid phase is related to the gas phase
pressure[4]:
)dt
dP.(
T.R
VV.a.J
SHGLSH
2
2 (8)
The rate of absorption of H2S per unit of gas-liquid interface, SH 2J , is given as[7]:
)CC.(E.KJ SHi,SHSHLSH 2222 (9)
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
7/24
Page 6 of 23
Accepted
Manus
cript
6
Where LK the liquid-side mass-transfer cofficient, i,SH 2C the liquidside interfacial
H2S concentration and SH 2C the concentration of H2S in the liquid bulk (i.e., x
with x the distance from the gas-liquid interfac) and for fast reaction 0C SH2 . Also
the enhancement factor SH2E is the result of chemical reaction[7]. In chemically
enhanced reaction regim SH2E can be defined as [5]:
2
L
m
Fe1
SHK
C.K.DHaE
1
3
2 (10)
Since the solubility of H2S in the catalytic solution is relatively high, so it is
assumed that concentration ofH2S at interface is equal to its solubility:
He
PCC
SH*
SHi,SH
2
22(11)
C*H2S is equilibrium concentration of H2S in solution and He is Henrys law
constant. Combination of above equation results:
SHSHL
G
LSH
22
2 P.E.a.K.He.V
T.R.V
dt
dP (12)
t.E.a.K.He.V
T.R.V
P
Pln SHL
G
L
SH
0
SH
2
2
2 (13)
Substitution of equation (10) in equation (12) gives:
dt.C.K.D.a.He.VT.R.V
PdP 13
2
2 m
Fe1
G
L
SH
SH (14)
Determination ofn1: In this experiment a high concentration of chelated iron solution
about 10000 ppm is prepared. Thus, variations of the iron concentration can be
neglected. First of all, the glass reactor is evacuated and 700 cm3 of the 10000 ppm
of RIPI20 catalytic solution is charged inside the reactor. A little dry sulfur is added
on the liquid surface to avoid further contacts between gas and liquid before starting
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
8/24
Page 7 of 23
Accepted
Manus
cript
7
the experiment and data recording. Then, H2S is fed into the reactor and variations
of the gas pressure inside the reactor is recorded with time for a given condition.
Linear trend of the data in Fig. 3 indicates that the absorption reaction is first order
with respect to the hydrogen sulfide concentration.
Also plot ofSH
0
SH
2
2
P
Pln vs. time as shown in Fig. 3 turns out to be linear and its
intercept from the y-axis is zero, then according to equation (13), SH2E is
independent of SH 2P and the reaction is first order in H2S[8].
Determination of m1: During the experimental tests the pressure of the gas phase is
kept constant and high value via continuous injection of H2S in order to maintain its
concentration in excess. 700 cm3 of 2000 ppm of RIPI20 catalytic solution is
charged into the reactor and dry sulfur powder is added to the contact area inside the
reactor. Then agitator is turned on and data recording is started. Fig. 4 shows the
results of the experiment.Linear trend of the data indicates that absorption reaction
is first order as a function of the chelated iron III concentration[9].
According to equation (10), the enhancement factor for H2S is plotted respect to
concentration of chelated iron III solution in Fig. 5. The slope of the line is equal
to2
m1 [8]. This quantity is equal 0.53, which confirms that the reaction is first order
with respect to the chelated iron III concentration.
Determination of K1: In this step, variations of both reactants are measured with time
and none of them is excess. The reaction is started with a 2000 ppm of RIPI20
catalytic solution with H2S initial pressure equals to 46.7 millibar. Using equation
(14), the data are analyzed to determine rate constant and finally the rate equation
for absorption ofH2S in chelated iron solution at pH=8-10 and for T=22oC can be
derived as follows:
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
9/24
Page 8 of 23
Accepted
Manus
cript
8
)ionconcentrattime(815.16k,C.C.kdt
dCr 11abFeSHab
SH
SH 32
2
2(15)
Regeneration reaction kinetics:
Reaction mechanism is considered as follows:
)L(2)aq(2)L(2)g(2OHO
2
1OHO
2
1(16)
OH2Fe2OHFe2O2
1 32
2
)aq(2(17)
Considering power form for the intrinsic rate equation yields:
22
2
2
2
2
m
Fe
n
O2
Fe
FeC.C.K
dt
dCr (18)
Using isolation method, in each step concentration of one of the reactants is
considered to be high and variations of concentration of the other one is
investigated.
Determination of n2: The reactor is evacuated and 700ml of chelated iron II is fed
into it. Then, pure oxygen is injected to the system up to a known pressure and
variations of oxygen pressure with time is recorded. In Fig.6 variations of
2
2
O
0
O
P
PLn is plotted versus time. The straight line with correlation factor of 0.992
and slope of 0.0025 indicates that regeneration reaction is first order with respect to
the dissolved oxygen concentration[10].
Determination of m2: In this experiment, concentration of dissolved oxygen is excess
and variations of concentration of iron II with time is recorded. The gas phase with
a high flow rate is charged into the reactor through a gas sparger. Fig. 7 shows a
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
10/24
Page 9 of 23
Accepted
Manus
cript
9
linear trend for variations of2Fe
C
1, which indicates that the reaction is second order
with respect to the chelated iron II concentration[9].
According to the Fig. 8, slope of the curve
2O
2
Fe
C
Clog versus
2
2
O
Fe
C
rlog (i.e. 1.9933)
shows the order of the reaction with respect to the chelated iron II concentration.
This expresses that order of 2 is correct again[9].
Determination of K2: In this step, variations of both reactants are measured with time
and none of them is excess. Fig. 9 shows that the slope of the resultant line is
0.0185. Using this slope the rate constant can be calculated. The experiment is
repeated for different temperatures and the results are plotted in Fig. 10. Activation
energy, Arrhenius constant and rate constant for regeneration reaction can be
estimated as follow:
RT
E
o2
a
eKK (19)
s.mol/m7.381K 26o and mol/kJ159.25E a
Kinetic model
By applying mass balance equations for two elements in absorption and
regeneration sections respectively and combination of resulted intrinsic rate
equations with them, concentration profiles of the H2S and iron II are determined.
For this purpose, it is necessary that mentioned equations are coupled with
hydrodynamic model results determined in previous work. In this way, required
height for complete absorption of H2S and regeneration of reacted iron II will be
determined. Following assumptions are considered in regeneration section:
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
11/24
Page 10 of 23
Accepted
Manus
cript
10
1) Negligible changes in gas phase composition due to high flow rate of
the air injected.
2) The mass transfer of oxygen from gas to liquid phase as a rate-
limiting step.
3) Negligible axial dispersion.
Several experiments were carried out to correlate variations of volumetric mass
transfer coefficient with gas flow rate in the reactor[2,6]
Absorp t ion sect ion: An element of the absorption section is illustrated in Fig. 11.
Consideration of mass balance for gas and liquid phases around the element yields
following equations respectively [11]:
0dx.A).YY(P.a.KdYRT
PQ * SHSHgSHg 222 (20)
0dx.A).CC(a.K.EdYRT
PQ SH
*
SHLSHg 222(21)
0dx.A.r.b).1(dCQ SH1SHL 22 (22)
In which, rH2S is intrinsic rate equation of absorption reaction. In equation (21), E is
enhancement factor and in the industrial process, theoretically the relation of E
and 3FeC depends on the regime of mass transfer with reaction that occurs and
diffusion of the reactive components. E relates proportionally to 3FeC and an
istaneous reaction may well explain the results observed and can be calculated from
the following relation [5,10]:
*
SHL,SH1
FeL,Fe
22
33
C.D.b
C.D1E (23)
Here, b1 is the stochiometric coefficient of the absorption reaction.
Regeneration section: Mass balance for liquid phase around the element in
regeneration section results the following equation:
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
12/24
Page 11 of 23
Accepted
Manus
cript
11
0dx.A.r.b).1(dCQdx.A).1(dx
dCD 22
2
2 Fe2FeL2
Fe
L,Fe (24)
Assuming negligible axial dispersion, the first term will be omitted. Here, rFe2+ is
intrinsic rate equation for regeneration reaction.
2
FeO2
Fe
Fe2
2
2
2 CC.Kdt
dCr (25)
)RT
)mol
kJ(159.25
exp().smol
m(7.381K
2
6
2 (26)
Regeneration reaction is limited to the rate of mass transfer of the oxygen from gas
to liquid phase; therefore the rate of oxygen transfer per unit volume of the
dispersed phase is as below:
2
FeO2oOiOLFe 22222 CC.K])C()C[(.a.Kr (27)
In which is the effectiveness factor. The final rate equation for regeneration
reaction is:
a.K
1
C.K
1)C.(K*4
dt
dCr
L
2
Fe2
iOregFe
Fe2
2
2
2 (28)
Autosweet Program
Using determined rate equations for absorption and regeneration sections,
Autosweet program was prepared to predict overall performance of the reactor
and safe operating zone in both sections for a given condition. To solve above
equations, some hydrodynamic parameters such as gas holdup, liquid velocity,
pressure distribution, bubble diameter are required. These parameters were
investigated in simultaneous work of the author [2].
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
13/24
Page 12 of 23
Accepted
Manus
cript
12
In absorption section, the required height for complete absorption of H2S (safe
operating zone) and concentration profile of two phases at steady and unsteady state
are determined through simultaneous solution of equations (20) and (22). In
regeneration section, equations (24) and (27) are solved simultaneously to
determine concentration profile and percentage of conversion at both steady and
unsteady sates.
Simulation of reactor and comparison of results: The experimental reactor is made
from glass with dimensions given in Table 1. Table 2 shows the properties of the
catalytic solution, RIPI20, and acid gas used as feedstock. Results of the simulation
of the reactor such as concentration profile at steady state, variation of concentration
with time, variation of equilibrium concentration with air/H2S ratio and comparison
of the theoretical and experimental results are shown in Fig. 12, Figs. (13-1,13-2),
Figs. (14-1,14-2) respectively. Table 3 shows overall results of simulations and
resulting experiments.
Conclusion
1- The absorption reaction of hydrogen sulfide by chelated iron III is first order
with respect to the both reactants.
2- Regeneration reaction is first order with respect to the dissolved oxygen
concentration and is second order with respect to the Chelated iron II
concentration, when the concentration of catalytic solution varies between
1000-4000 ppm.
3- Comparison of the theoretical and experimental results shows a good
agreement and confirms the capability of the model implemented and the
Autosweet program.
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
14/24
Page 13 of 23
Accepted
Manus
cript
13
4- The results of this study were used to design a new reactor for H2S removal
at RIPI with about 1 m3 capacity and also for optimization of similar
reactors in operating units.
5- Application of such reactors forH2S removal is genuine and development of
the model is necessary for simulation of larger scale units.
Nomenclatures:
A Cross sectional area m2
a Interfacial area per unit volume of gas and liquid m2/m
3
b Stochiometric coefficient -
SH2C Concentration of hydrogen sulfide at gas bulk mol/m3
*
SH2C Concentration of hydrogen sulfide at interface mol/m3
FeC Concentration of iron in catalytic solution mol/m3
Ceq,Fe Concentration of ironat equilibrium mol/ m3
iO )C( 2 Concentration of oxygen at interface mol/m3
oO )C( 2 Initial concentration of oxygen mol/ m3
D Dispersion coefficient m2/s
E Enhancement factor -
Ea Activation energy kJ/mol
He Henrys law constant Pa.m
3
/mol
Ha Hatta number -
J Absorption rate mol/s
K Pre-exponential reaction rate constant m6/mol
2.s
K1 Absorption rate constant m3/mol.s
K2 Regeneration rate constan t m6/mol
2.s
Kg Gas phase mass transfer coefficient m/s
KL Liquid phase mass transfer coefficient m/s
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
15/24
Page 14 of 23
Accepted
Manus
cript
14
m , n Order of a reactant in reaction mol/m2.s
P Pressure Pa
Po
initial value of Pressure for any species Pa
Qg Volumetric gas flow rate m3
/s
R Gas constant 8.314 J/ mol.k
r Reaction rate mol/s
T Time s
VL Volume of liquid phase m3
VG Volume of gas phase m3
Z Distance from gas sparger m
Effectiveness factor -
Average gas holdup at cross section -
References
[1] G. Nagl, Removing hydrogen sulfide, Hydrocarbon engineering, 6 (2001) 35-38
[2] M.A. Jafari nasr, H. Bakhtiyari, A. Karimi, A. Tavasoli, Single Step H2S
Removal Using Chelated Iron Solution: Investigation of hydrodynamic parameters
in an internal loop air lift reactor, I. J. of Sci. & Tech., Trans. B, 28(B6) (2004) 643-
651.
[3] M. Abedinzadegan, M.R. Jafari Nasr, A mathematical model describing the ARI
Autocirculation reactor for low temperature conversion of H2S into sulfur,
Chem.Eng.& Technol., 17 (1994) 141-143.
[4] E. Sada, H. Kumazawa, H. Machida, Oxidation Kinetics of FeIIEDTA and FeII
NTA Chelates by Dissolved Oxygen, Ind. Eng. Res., 26 (1987) 1468-1472.
[5] H. J. Wubs, A. A. C. M. Beenackers, Kinetics of the Oxidation of Ferrous
Chelates of EDTA and HEDTA in Aqueous Solution, Ind. Eng. Chem. Res., 32
(1993) 2580-2594.
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
16/24
Page 15 of 23
Accepted
Manus
cript
15
[6] A. Karimi, A. Jebreili Jolodar, A. A. RajabPour, H. R. Bakhtiary, Mass transfer
study in AUTOCIRCULATION reactor for H2S removal from acid gas streams",
Petroleum & Coal, 49 (1) (2007) 27-33.
[7] J.F. Demmink, A. A. C. M. Beenackers, Gas desulfurization with ferric chelates
EDTA and HEDTA, new model for the oxidative absorption of hydrogen sulfide,
Ind. Eng. Chem. Res., 37 (1998) 1444-1453.
[8] H. J. Wubs, A. A. C. M. Beenackers, Kinetics of H2S Absorption into Aqueous
Ferric Solutions of EDTA and HEDTA, AIChE Journal, 40(3) (1994) 433-443.
[9] O. Levenspiel, Chemical Reaction Engineering, 2nd Edition, Wiley Eastern
University, New York, 1989.
[10] J.F. Demmink, A. A. C. M. Beenackers, Oxidation of Ferrous Nitrilotriacetic
Acid with Oxygen: A Model For Oxygen Mass Transfer Parallel to Reaction
Kinetics, Ind. Eng. Chem. Res., 36 (1997) 1989-2005.
[11] A. Gianetto, P.L. Silveston, Multiphase Chemical Reactors, Hemisphere
Publishing Corporation, 1995.
Acknowledgment
The author wish to express his appreciation to RIPI of National Iranian Oil
Company (NIOC) for the financial support of this research, project Nos:
71010109,71010112.
Address
Correspondence concerning this paper should be addressed to A. Karimi, Gas
research division, Research Institute of Petroleum Industry (RIPI), National Iranian
Oil Company (NIOC), West Blvd. Azadi Sport Complex, P. O. Box: 14665-1998,
Tehran, Iran
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
17/24
Page 16 of 23
Accepted
Manus
cript
16
Tabels and Figures:Table 1 - Experimental glass reactor dimensions
Length (m) Diameter
(m)
Riser 1.9 0.145
Downcomer 1.8 0.174
Gas-liquid separator 0.62 0.25
Table 2 - Properties of the catalytic solution, RIPI20
and acid gas used as feedstock
Property Viscosity
(Pa.s)
Density
(kg/m3)
Concentration
Liquid 1.005*10-3
1000 2000 ppm ironchelate
Gas 1.65*10-5
1.3 2 vol.% of H2S in acid gas
Table 3 - Overall simulation resultsLiquid
residencetime / s
Liquid
downcomervelocity /(m/s)
Liquid
massvelocity
/ (kg/s)
Average
gas holdup
Steady state
oxidationreduction
potential /
mV
H2S
absorptionlength / m
CFe+2 at the
end ofabsorption
zone / ppm
CFe+2 at the
end ofregeneration
zone / ppm
33.6 0.175 0.89 0.012% -101 0.03 266 69
LIQUID
STORAGE
TANK
V5
V6V1
D.O .Meter
orORP
COMPUTER
BYPASS
IBM PS / 2
Agitator
pH
electdrode
Vacuum
pump
U-tube
manometer
V4
Air
V3
H2SN2
V2
Fig.1 - Autocirculation scheme of the reactor. Fig.2 - Glass reactor for kinetic experiments.
AA
A A
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
18/24
Page 17 of 23
Accepted
Manus
cript
17
Fig.3Determination of n1
Fig.4Determination of m1
SH
SHo
2
2
P
Pln
3
30
Fe
Fe
C
Cnl
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
19/24
Page 18 of 23
Accepted
Manus
cript
18
Fig.5 - Determination of m1using eq.(10),Slopeof the line is equal to m1/2=0.5.
Fig.6-Determination of n2.
EH2S
2
2
O
o
O
P
Pnl
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
20/24
Page 19 of 23
Accepted
Manus
cript
19
Fig.7-Determination of m2 using the methodpresented by Levenspiel [9].
Fig.8-Determination of m2,Slope of thecurve is equal to reaction order [9].
2
2
O
Fe
CClog
2
2
O
Fe
C
r
log
1
3)
/
/(
1
2
m
mol
CFe
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
21/24
Page 20 of 23
Accepted
Manus
cript
20
Fig.9 - Rate constant for regenerationreaction at 25oC
Fig.10-Variation of regeneration reaction
rate constant with temperature.
2
2
O
Fe
C
Cln
ln
K
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
22/24
Page 21 of 23
Accepted
Manus
cript
21
CA
YA
x + dxx
dxdx
dYY AA
dxdx
dCC AA
dxdx
dT+TT
)gas(AeA
Y
eAC
eBC
Liquid
zB+A P2k
fAC
fBC
fAY
gQ
lQdx
dx
dCC BB
Fig.11-An element of absorption section.
Fig.12- Concentration profile along riser at steady state
Fe+
Fe3+
CFe
3+/
m
CFe
2+/
m
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
23/24
Page 22 of 23
Accepted
Manus
cript
22
Fig.13-1-Variations of CFe2+
with time at
the end of regeneration section.
Fig.13-2-Variations of CFe3+
with time at
the end of regeneration section
H2S =0.95 (cm3 / s)
AIR=66.21 (cm3 / s)
N2=46.35 (cm3 / s)
H2S =0.95 (cm3 / s)
AIR=66.21 (cm3 / s)N2=46.35 (cm
3 / s)CFe
3+/
m
CFe
2+/
m
7/30/2019 A. Karimi_Kinetic Studies and Reactor Modelingpdf
24/24
Accepted
Manus
cript
Fig.14-1-Variations of equilibrium
concentration of Fe2+ vs. Air/H2Svolume ratio at feedstock.
Fig.14-2-Variations of equilibrium
concentration of Fe3+vs. Air/H2S
volume ratio at feedstock.
N2=46.35 (cm3 / s)
H2S = 0.95 (cm3 / s)
N2=46.35 (cm / s)H2S = 0.95 (cm
3 / s)
AIR / H2S Vol. Ratio
AIR / H2S Vol. Ratio
Ceq,Fe
2+
/ppm
Ceq,Fe
3+
/ppm