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A Novel CLC Assisted Catalytic Naphtha Reforming process for Simultaneous Carbon Dioxide Capture and Hydrogen Production Enhancement Sajjad Rimaz, and Davood Iranshahi Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/ef502421k • Publication Date (Web): 02 Feb 2015 Downloaded from http://pubs.acs.org on February 9, 2015

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A Novel CLC Assisted Catalytic Naphtha Reforming process for Simultaneous Carbon Dioxide Capture and Hydrogen Production Enhancement Sajjad Rimaz, Davood Iranshahi* Department of Chemical Engineering, Amirkabir University of Technology (Tehran polytechnic), Tehran, Iran

Abstract The application of chemical looping combustion (CLC) in order to eliminate the commonly used furnace in catalytic naphtha reforming has been analyzed. A mathematical model has been proposed to evaluate the performance of naphtha reforming coupled with chemical looping combustion (NR-CLC).

NiO18-αAl2O3 particles have been used as oxygen carriers in NR-CLC.

These particles have shown very high reactivity with complete CH4 conversion due to Ni-based oxygen carriers. In NR-CLC configuration, three reactors have been applied. In the first and the second reactors, chemical looping combustion is coupled with naphtha reaction. In this new configuration, the reforming tubes have been located vertically inside the air reactor so the catalytic naphtha reforming occurs in these fixed-bed catalytic tubes. The results obtained from the model proposed for NR-CLC have been compared with the corresponding results reported in literature for conventional naphtha reforming (CNR). The values of some important parameters such as temperature, mole fraction, molecular weight, aromatic and hydrogen production rates resulted from these two configurations have been compared. The results revealed that by employing NR-CLC, the hydrogen and aromatics flow rates increases significantly. A great amount of almost pure carbon dioxide can be captured by water removal from the fuel reactor through condensation. Keywords: Naphtha reforming; Aromatic boosting; mathematical modeling, Chemical-looping combustion; CO2 Capture.

*

Corresponding author. Tel.: +98 21 64543189; Fax: +98 21 66405847. Email:[email protected]

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Introduction Catalytic naphtha reforming is a refinery process used for the production of high-octane

number gasoline, aromatics like benzene, toluene and xylenes for petrochemical industry, and hydrogen as a valuable sub product 1, 2. To improve the performance of this process, a large number of studies have been conducted. Many researchers have focused on the kinetics of catalytic naphtha reforming. Since a large number of reactions may occur in reformers, developing a detailed kinetic model that considers all the components and reactions is complicated 3. Smith 4 presented a model considering paraffins, naphthenes, aromatics and the main reactions involved. Weifeng et al.

5

developed a kinetic model including 20 lumped components and 31 reactions. A

number of kinetic models to describe the reforming process have been reported by Juarez et al. 6, Froment et al. 7, Hu and Zhu

8

and Hong jun et al. 9. Some researchers studied the

mathematical modeling of the process in order to improve the yields of aromatic and hydrogen. In this regard, Juarez et al.

10

modeled and simulated four catalytic reactors

arranged in series for naphtha reforming. Weifeng et al. 3 presented an optimization study for the whole industrial catalytic reforming process. Mazzieri et al. Tailleur et al.

13, 14

11

, Sugimoto et al12, and

investigated the coke formation and regeneration of catalyst during the

catalytic naphtha reforming process. Conventional technologies such as pre-combustion, oxy fuel combustion, calcinationscarbonation cycle 15-18 and post combustion 19-21 have been used widely to separate CO2 from combustion process

22, 23

. Among great disadvantages of conventional carbon capture and

storage (CCS) technologies are the need for a makeup solvent and recovery process restrictions in absorption (using amine solution), high operating pressure in adsorption, providing pure oxygen as gasification agent in pre-combustion and oxy-fuel methods


24-27

.

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Furthermore, these technologies are highly expensive. In this regard, chemical-looping combustion (CLC) has been revealed as an efficient and low-cost process for CO2 capture 28. Chemical-looping combustion (CLC) has been first proposed by Ritcher and Knoche 29. The process is based on the transfer of oxygen from air to the fuel by means of a solid oxygen-carrier avoiding direct contact between fuel and air

30, 31

. Figure 1 shows a general

scheme of this process. The system is typically composed of two reactors: an air and a fuel reactor. The fuel gas is usually introduced to the fuel reactor where in the metal oxide is reduced according to the following reaction: (2k + s) MeO + Ck H 2 s → (2k + s ) Me + sH 2O + kCO2

(1)

The gas stream exiting from the fuel reactor contains CO2 and H2O. Almost pure CO2 can be obtained if H2O is condensed. Then, the reduced metal oxide (Me) enters to the air reactor where in the metal is oxidized according to the following reaction: (2)

1 Me + O2 → MeO 2

It is evident that a complete conversion of MeO to Me and Me to MeO is not necessarily obtained in actual conditions 32, 33.

Figure 1 The key issue in the CLC system performance is the oxygen-carrier materials. Among the major characteristics of an appropriate oxygen-carrier are: •

No agglomeration 34.

•

Favorable thermodynamics regarding the fuel conversion to CO2 and H2O in CLC 35.

•

Negligible carbon deposition that would release CO2 in the air-reactor and reducing CO2 capture efficiency36.

•

Sufficient oxygen transport capacity 37.

•

High reacting for reduction and oxidation reactions to reduce the solid inventory in


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the reactors, and maintained during many successive redox cycles 37. Most of studies have focused on the feasibility of the utilization of oxides of metals such as Ni, Fe, Cu, Mn 38. In general, pure metal oxides do not fulfill the above characteristics and their reaction rates decreased quickly in a few cycles

39, 40

that reveals the need of using a

support. A porous support provides a higher surface area, a binder for increasing the mechanical strength and attrition resistance 41. Oxygen carrier particles and support material in CLC should be selected based on melting point, oxygen transport capacity, chemical stability, Gibbs free energy changes and equilibrium composition of reactions. Because of high melting point, high oxygen transport capacity, high reactivity with all fuel gases, no agglomeration problems, and avoidance of carbon deposition at CLC conditions, NiO supported on Al2O3 compounds is a good alternative for this purpose. 37 Coupling one endothermic reaction and an exothermic reaction was analyzed in previous publications and good results were achieved42-45. Accordingly this study aims to evaluate the performance of a novel naphtha reforming process using chemical looping reactors as heat sources. In the new configuration proposed, a furnace which is normally located before each reactor to restitute the reduction of temperature is eliminated and in the first and second reactors, chemical looping combustion is coupled with naphtha reaction. A comprehensive mathematical model is developed for NR-CLC and the consumption rate of reactants and the production rate are compared with the corresponding values obtained in a CNR. Using the new configuration, CO2 capture by chemical looping combustion is coupled with naphtha reforming. Furthermore an improvement could be found in hydrogen and aromatic production in naphtha reforming process due to coupling with chemical looping combustion, which will be discussed in details in the following sections.


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2

Process Description

2.1 Conventional naphtha reforming process (CNR) Naphtha reforming is a major process in the petroleum refineries and petrochemical industry applied to convert paraffins and naphthenes into aromatic46. Since naphtha reforming reactions are highly endothermic, temperature and consequently, reaction rate may decrease along the reactor. Therefore, in conventional systems, three or four adiabatic axial flow tubular reactors are typically used, with a furnace located before each reactor to restitute temperature drop inside the reactor. The H2/HC ratio is one of limiting parameters in the naphtha reforming process. In industrial applications, it has been recommended to keep H2/HC in the range of 4-6 47. If the H2/HC decreases, the catalysts may be subjected to a rapid deactivation due to coking. Typically, a recycle line is assisted in catalytic reformers, which returns some of the produced hydrogen to the reactor and adjusts the H2/HC in the reactors. More details on the conventional catalytic naphtha reforming units can be found in the literature

48, 49

. A set of typical operating conditions and catalyst specifications for

conventional systems is presented in Table 1.

Table 1 2.2 Naphtha reforming coupled with chemical looping combustion (NR-CLC) Figure 2 demonstrates a conceptual process diagram of NR-CLC configuration. In a NR-CLC configuration, three reactors are usually constructed and used. In the first and the second reactors, chemical looping combustion is coupled with naphtha reaction. In these two reactors, naphtha reformer characterization is similar to CNR, whereas, CLC has been used instead of furnace. The air reactor (AR) and fuel reactor (FR) are two moving-bed contactors. In this novel arrangement, the reforming tubes are located vertically inside the air reactor whereas the fuel reactor covers the AR. In NR-CLC, heat generated in the AR is transferred continuously to the FR and naphtha reforming tubes. The circulation of products and the 5 ACS Paragon Plus Environment

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direction of entrance of reactants to the reactor have been illustrated for CLC section in the first reactor (Figure 2). The design characteristics of AR and FR are based on previous experimental observations regarding NiO18-αAl2O3 oxygen carrier in the continuous CLC prototype. 28, 50, 51 This data are presented in Table 2.

Figure 2 Table 2 3

Reaction scheme and kinetic expressions

3.1 Naphtha section (Smith’s model) To investigate the kinetic of multi component naphtha mixture, a kinetic scheme is considered based on Smith’s model 4. In this model, the following four reactions are considered:

• Dehydrogenation of naphthenes to aromatics Naphthenes (CnH2n)↔Aromatics (CnH2n-6)+3H2

(1)

• Dehydrocyclization of paraffins to naphthenes Naphthenes (CnH2n)+H2↔Paraffins (CnH2n+2)

(2)

• Hydro cracking of naphthenes to lower hydrocarbons Naphthenes (CnH2n) + n/3H2→Lighter ends (C1–C5)

(3)

• Hydro cracking of paraffins to lower hydrocarbons Paraffins (CnH2n+2) + (n−3)/3H2→Lighter ends (C1–C5)

(4)

The rate equations of the above reactions are expressed as follows, respectively,

r1 = (

r2 = (

kf1 K e1 kf 2 Ke2

3

)(k e1 p n − p a ph )

(5)

)(k e 2 p n p h − p p )

(6)


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r3 = (

r4 = (

kf3 pt kf4 pt

) pn

(7)

)pp

(8)

where, the values of reaction rate constants ( k f i ), the equilibrium constants ( K ei ), the activation energies ( Ei ), and the standard heats of reactions ( ∆H 298K ) are presented in Table 3

52

. The Smith’s model has been widely used by researchers due to its simplicity and

accuracy53-55.

Table 3 3.2 Oxidation and reduction of oxygen carriers in CLC In design of a CLC process, the oxidation and reduction rate of oxygen carriers should be considered because they are directly related to the solids inventory in the AR and FR. The following exothermic oxidation reaction occurs inside AR: O2 + 2 Ni → 2 NiO

o ∆H 298 = −479.4kj.mol −1

(9)

Moreover, in FR, the endothermic reduction of Ni-based oxygen carriers with CH4 carriers is as follows: CH 4 + 4 NiO → 4 Ni + CO2 + 2 H 2O

o ∆H 298 = 156.5kj.mol −1

(10)

The following equation is applied to determine the reduction and oxidation rates of oxygen carriers for both the fuel and the air reactors. rs =

dX s 3 = (1 − X s ) 2 / 3 dt τ

(11)

Where

τ=

ρ m rg

(12)

bi kC n


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k = k0 e− E / RT

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(13)

Here, the reaction rate per unit volume of particle is proportional to the reaction rate constant. The properties and kinetic parameters for the oxidation and reduction of NiO18αAl2O3 oxygen-carriers are presented in Table 4 50 .

Table 4 4

Mathematical modeling Figure 3 shows a differential element considered along axial direction in the NR-CLC to

develop the mass and energy balance equations. The following assumptions are made in the mathematical modeling of NRT, AR and FR: •

Steady-state condition is hold (for NRT, AR and FR)

•

The catalytic packed bed is homogeneous (NRT)

•

Homogeneous gas-solid reactions occur in the moving beds (AR and FR)

•

Plug flow pattern is employed in each side of the reactors (NRT, AR and FR)

•

The reactions take place on the surface of catalyst particles (NRT)

•

The intra-pellet heat and mass diffusion in catalyst pellet is neglected (NRT)

•

The gas phase is ideal (NRT , AR and FR)

•

The heat loss from the walls to the ambient is negligible

Figure 3 The governing mass and energy balance equations with appropriate boundary conditions for NRT, AR and FR are presented in Table 5. Other equations required to determine the physical properties as well as the heat and mass transfer coefficients are summarized in Table 6 56, 57.

Table 5 8 ACS Paragon Plus Environment

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Table 6 5

Numerical solution and model validation The present model contains a set of ordinary differential equations (ODEs) resulted from

the mass and energy balances together with a set of non-linear algebraic equations of the kinetic model and the auxiliary and the hydrodynamic correlations. The finite difference method is applied to solve the ODEs. The length of each reactor is divided to 100 individual increments and the Gauss-Newton method is applied to solve the non-linear algebraic equations. This procedure is repeated for all nodes in each reactor and the values obtained from each node are used as inlet conditions for the next node. Additionally, the validity of the present model is evaluated by comparing the simulated results of CNR with a set of industrial data available under steady-state condition58. The results are summarized in Table 7. As it is seen in Table 7, a good agreement is achieved between the model results and the industrial data for CNR. Moreover, the result of model developed for NR-CLC are presented in this table for the corresponding conditions (the industrial data are not available for this configuration). The calculated results confirm the higher mole fraction of aromatics in NRCLC in comparison with that in CNR. Table 8 shows the composition of reformate and product stream of third reactor for each case in detail. The performance of NR-CLC configurations is investigated and compared with CNR performance in the next section in details.

Table 7 Table 8


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Results and Discussions

6.1 Naphtha section 6.1.1 Paraffin and naphthene The molar flow rates of reactants in CNR and NR-CLC are compared in Figure 4(a) and (b). In this figure the dimensionless length of system is defined as follow:

η=

z L

(14)

Where L is the sum of Lengths of the three considered reactors. The consumption rate of paraffin increases considerably along the system length in the coupled configuration in comparison with CNR (Figure 4(a)). The difference between profiles of molar flow rate of paraffin obtained in CNR and NR-CLC is due to the efficient heat transfer from air reactor in the coupled mode. The molar flow rate of naphthene is shown in Figure 4(b). As it is revealed from this figure, the thermal effects of coupled reactors change the equilibrium conditions and shift the reactions to consume more reactants. In order to show the differences between the results obtained from the two configuration studied, a small figure is plotted in Figure 4(b) which shows the change in molar flow rate of naphthene with the dimensionless length of the system at the end of the third reactor.

Figure 4 6.1.2 Hydrogen, aromatics and light ends Hydrogen produced in catalytic reforming has become increasingly valuable as it is used in hydroprocessing units for removal of sulfur and nitrogen as well as hydro cracking 59. Figure 5(a)-(c) shows the molar flow rates of various products obtained from the naphtha section of the coupled reactors. According to this figure, the hydrogen and aromatic production rate in NR-CLC are higher than those in CNR hence Figure 5 reveals the preference of NR-CLC configuration to the CNR configuration as a higher hydrogen and 10 ACS Paragon Plus Environment

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aromatic production rate is achieved at the end of the third reactor. As it is seen, the hydrogen and aromatic production rate in outlet of the second reactor in the coupled reactors is higher than that in outlet of the third reactor in CNR. On the other hand, as mentioned previously in Table 7, the catalyst loads of the third reactor is equal to the sum of the catalyst loads of the first and second reactors. Therefore, a great reduction in capital and operational costs (pt metal in the catalyst) can be achieved by eliminating the third reactor in NR-CLC setups. Figure 5(c) reveals the production of light ends. The latter is used as a feed stock for LPG production process.

Figure 5 6.1.3 The effect of total molar flow rate and molecular weight Figure 6(a) shows the variation of total molar flow rate of naphtha through the reactor. In this figure, change in the total flow rate relative to the inlet values is about 15.2 and 16.4% for CNR and NR-CLC, respectively. In comparison with CNR, NR-CLC produces lighter hydrocarbons like lighter ends and aromatics. Consequently, the average molecular weight is lower in NR-CLC (Figure 6(b)) which is an advantage of using NR-CLC configuration. It should be noted that in the present model, the changes of total molar flow rate, molecular weight and the physical properties such as heat capacity, viscosity, density along the axial direction in order to increase the accuracy of the predicted results.

Figure 6


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6.1.4 H2/HC molar ratio The variation of H2/HC molar ratio along the reactor length is shown in Figure 7. The H2/HC ratio increases along the system length since hydrogen is produced. Higher H2/HC molar ratio increases the catalyst lifetime and lowers the deactivation caused by coking. This is occurred especially in the third reactor where the temperature is higher. On the other hand, higher H2/HC ratio is a limiting point that shifts the dehydrogenation reaction to the reverse direction reducing the hydrogen and aromatic productions. Higher temperature in the NRCLC may reduce the negative effects of the H2/HC ratio increase.

Figure 7 6.2 CLC section As it is illustrated in Figure 2, the chemical looping mode in this novel configuration is quite different with the ordinary modes used traditionally in the previous papers

38, 60

. In the

present configuration, the fuel reactor acts as a cover for the air reactor. The air reactor provides the heat required for the reaction. Figure 8(a) shows the variations of oxygen and nitrogen mole fractions along the air reactor length. As it is seen, oxygen is consumed completely inside the both reactors. As a result, at the end of reactors where there is no oxygen, the oxidation rate of solids becomes zero. Figure 8(b) shows the variation of CO2, H2O and CH4 mole fractions in fuel reactors. The CO2 produced can be captured easily after water condensation whereas no further energy is required for the separation, because CO2 is not mixed and diluted with nitrogen. CH4 is completely consumed along the reactors; this can be due to the high reactivity of NiO-based oxygen carrier.

Figure 8


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6.3 Thermal effects Figure 9(a) shows the temperature change along the naphtha tubes for CNR and NRCLC furthermore, the variation of heat consumed in naphtha tubes and transferred between air reactor and naphtha tubes is illustrated in Figure 9(b). The heat transferred is calculated from the following equation: Q = m × PPer × Z × U × (Ta − Tn )

(15)

Where m is the number of tubes and Pper is the perimeter of one tube. Since the naphtha reforming reaction is highly endothermic, the temperature decreases remarkably in each reactor in CNR. Using a thermal heat source leads to moderate the temperature drop and increase the reaction rate. At the beginning of the first and second reactors in the NR-CLC configuration, the heat consumed is greater than that received from the tube wall. This is the reason for the temperature drop at this zone. At the end these reactors, the amount of heat received from the air reactor is higher than that consumed along the tubes. The latter results in a temperature increase in the system (Figure 9(a)). Heat consumption in the FR and heat transferred from AR to FR are depicted in Figure 10(a) also the temperature change along the system shown in Figure 10(b). The difference between these values is small, while the heat consumed is a little more than the heat transferred. So, the temperature in the fuel reactor slightly decreases. Figure 11(a) shows the variation of heat generation in the AR. Most of heat is generated at the beginning of the reactor while the generation rate decreases through the reactor length. Since the heat transferred to the fuel reactor and naphtha tubes is lower than the heat generated in air reactor, the temperature of air reactor increases continuously along the reactor length (Figure 11(b)). The temperature differences between air reactor and fuel reactor and naphtha tubes, as the driving force, increased along the reactor length. Therefore, the amount of heat transferred increases despite the decrease in heat generated in the air 13 ACS Paragon Plus Environment

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reactor.

Figure 9 Figure 10 Figure 11 The effects of naphtha flow rate and naphtha temperature on H2 production are illustrated in Figure 12(a). Furthermore, the effect of naphtha flow rate and feed temperature of air reactor is shown in Figure 12(b). By increasing temperature of naphtha feed, the H2 production is increased. The increase in the feed temperature entering the air reactor causes

an increase in heat transferred to naphtha tubes, so the molar flow rate of hydrogen is increased (Figure 12(b)). Although increasing flow rate of naphtha causes more H2 production, however, higher than a certain value, the hydrogen production is decreased due to the lack of energy required for the reaction to be occurred.

Figure 12

7

Conclusion A novel concept has been proposed for the application of CLC rather than a furnace in

the naphtha reforming process for hydrogen production and CO2 capture. NiO18-αAl2O3 particles have been used as oxygen carriers in NR-CLC. CLC consists of two inter-connected moving-bed reactors operating co-currently. Naphtha reforming occurs over the packed Ptbased catalyst in vertical tubes inside AR. Considering aromatics and hydrogen as the main products of the naphtha reforming process, the change in the production rates of these two components revealed the preference


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of the novel configuration proposed (molar flow rates of hydrogen and aromatics increased up to 1.47kmol/h and 6.22 kmol/h in comparison with CNR). The obtained results showed that, by employing CLC rather than a furnace, the production rates of H2 and aromatics were increased significantly in the outlet of the first and the second reactors in comparison with that at the outlet of the third reactor in CNR. Thus, the capital and operational costs may be reduced notably by eliminating the third reactor. Complete conversion of oxygen and methane as a result of using NiO based oxygen carrier has been achieved in the air and the fuel reactors. By employing NR-CLC instead of CNR large amounts of pure carbon dioxide can be captured (up to 457.7 kmol/h and 750.3 kmol/h from the first and the second fuel reactors, respectively). Thus, the emission of a large amount of pollutants to the atmosphere may be reduced.


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Nomenclatures a = catalyst activity, – Ac= cross-section area, m2

bi = stoichiometric coefficient, –

C = concentration, mol m–3

C j 0 = inlet concentration of component j, mol m–3 C p = specific heat capacity at constant pressure, kJ kmol–1 K–1 CT= Total concentration, molm-3

C v = specific heat capacity at constant volume, kJ kmol–1 K–1 d p = particle diameter, m D e = effective diffusivity, m2s–1 E d = activation energy of catalyst, J mol–1 E i = activation energy for ith reaction, kJ kmol–1 k eff = effective thermal conductivity, W m–1 s–1

k ci = mass transfer coefficient for component i, m h–1 k f 1 = rate constant for reaction (1), kmol h–1 kgcat–1 MPa–1 k f 2 = rate constant for reaction (2), kmol h–1 kgcat–1 MPa–2

k f 3 = rate constant for reactions (3), kmol h–1 kgcat–1 k f 4 = rate constant for reactions (4), kmol h–1 kgcat–1 K e1 = equilibrium constant, MPa3

K e 2 = equilibrium constant, MPa−1 K d = deactivation constant of the catalyst, h–1

L = reactor length, m m = number of tubes, – 16 ACS Paragon Plus Environment

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Mi= molecular weight of component i, kg kmol–1 Me=metal, –

MeO =metal oxide, – n = number of components, – Ni= molar flow rate of component i, kmol h–1 Pi= partial pressure of component i, kPa

P = total pressure, Pa

R = gas constant, kJ kmol–1 K–1 Ra=reaction rate in air reactor, mol m-3 s-1 Rf=reaction rate in fuel reactor, mol m-3 s-1

rg =grain radius, m −1 ri =rate of reaction for ith reaction, kmol kg cat h-1

rs =oxidation and reduction rate of oxygen carriers, s-1 s a = specific surface area of catalyst pellet, m2 kg–1 Ta, Tf, Tn = Temperature of air reactor, fuel reactor, and naphtha tubes, respectively (K)

u z = feed velocity, m s–1 uza= feed velocity of air reactor, m s–1 uzf= feed velocity of fuel reactor, m s–1 U=overall heat transfer coefficient between two sides of reactor, W m-2 K-1 Uj= internal energy of component j, j mol-1

z = axial coordinate, m

Greek letters

ε = void fraction of catalyst bed, – µ = viscosity of gas, kg m–1 s–1 η =dimensionless length

ρ = density of gas, kg m–3 τ i =Time required for complete conversion, s ∆H = heat of reaction, kJ kmol–1 of H2 Subscript & Superscripts A= aromatic a=air reactor side f=fuel reactor side 17 ACS Paragon Plus Environment

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H2= hydrogen i= numerator for reaction j= numerator for component N= naphthene n= tube side P= paraffin ss= steady state

Abbreviations AR=air reactor, – CCS=conventional carbon capture and storage, – CLC=chemical looping combustion, – CNR=conventional naphtha reforming, – FBP= final boiling pint, ◦C FR=fuel reactor, – IBP= initial boiling pint, ◦C LHSV= liquid hourly space velocity, h–1 NRT=naphtha reforming tube, – NR-CLC=naphtha reforming coupled with chemical looping combustion, – Pt= platinum, – TBP= true boiling point, K WHSV= weight hourly space velocity, h–1


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References 1. D’Ippolito, S. A.; Vera, C. R.; Epron, F.; Samoila, P.; Especel, C.; Marécot, P.; Gutierrez, L. B.; Pieck, C. L., Influence of tin addition by redox reaction in different media on the catalytic properties of Pt-Re/Al2O3 naphtha reforming catalysts. Applied Catalysis A: General 2009, 370, (1), 34-41. 2. Stijepovic, M. Z.; Vojvodic-Ostojic, A.; Milenkovic, I.; Linke, P., Development of a kinetic model for catalytic reforming of naphtha and parameter estimation using industrial plant data. Energy & Fuels 2009, 23, (2), 979-983. 3. HOU, W.; SU, H.; HU, Y.; Chu, J., Modeling, simulation and optimization of a whole industrial catalytic naphtha reforming process on Aspen Plus platform. Chinese Journal of Chemical Engineering 2006, 14, (5), 584-591. 4. Smith, R., Kinetic analysis of naphtha reforming with platinum catalyst. Chem. Eng. Prog 1959, 55, (6), 76-80. 5. Hou, W.; Su, H.; Hu, Y.; Chu, J., Lumped kinetics model and its on-line application to commercial catalytic naphtha reforming process. JOURNAL OF CHEMICAL INDUSTRY AND ENGINEERING-CHINA- 2006, 57, (7), 1605. 6. Ancheyta-Juárez, J.; Villafuerte-Macías, E., Kinetic modeling of naphtha catalytic reforming reactions. Energy & fuels 2000, 14, (5), 1032-1037. 7. Sotelo-Boyás, R.; Froment, G. F., Fundamental kinetic modeling of catalytic reforming. Industrial & Engineering Chemistry Research 2008, 48, (3), 1107-1119. 8. Hu, S.; Zhu, X., Molecular modeling and optimization for catalytic reforming. Chemical Engineering Communications 2004, 191, (4), 500-512. 9. Hongjun, Z.; Mingliang, S.; Huixin, W.; Zeji, L.; Hongbo, J., Modeling and simulation of moving bed reactor for catalytic naphtha reforming. Petroleum science and technology 2010, 28, (7), 667-676. 10. Ancheyta-Juarez, J.; Villafuerte-Macias, E.; Diaz-Garcia, L.; Gonzalez-Arredondo, E., Modeling and simulation of four catalytic reactors in series for naphtha reforming. Energy & fuels 2001, 15, (4), 887-893. 11. Mazzieri, V. A.; Pieck, C. L.; Vera, C. R.; Yori, J. C.; Grau, J. M., Analysis of coke deposition and study of the variables of regeneration and rejuvenation of naphtha reforming trimetallic catalysts. Catalysis Today 2008, 133, 870-878. 12.

Sugimoto, M.; Murakawa, T.; Hirano, T.; Ohashi, H., Novel regeneration method of 19 ACS Paragon Plus Environment

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Pt/KL zeolite catalyst for light naphtha reforming. Applied Catalysis A: General 1993, 95, (2), 257-268. 13. Galiasso Tailleur, R.; Davila, Y., Optimal hydrogen production through revamping a naphtha-reforming unit: catalyst deactivation. Energy & Fuels 2008, 22, (5), 2892-2901. 14. Tailleur, R. G., Cross-Flow Naphtha Reforming in Stacked-Bed Radial Reactors with Continuous Solid Circulation: Catalyst Deactivation and Solid Circulation between Reactors. Energy & Fuels 2012, 26, (11), 6938-6959. 15. Romeo, L. M.; Abanades, J. C.; Escosa, J. M.; Paño, J.; Giménez, A.; SánchezBiezma, A.; Ballesteros, J. C., Oxyfuel carbonation/calcination cycle for low cost CO2 capture in existing power plants. Energy Conversion and Management 2008, 49, (10), 28092814. 16. Shimizu, T.; Hirama, T.; Hosoda, H.; Kitano, K.; Inagaki, M.; Tejima, K., A Twin Fluid-Bed Reactor for Removal of CO2 from Combustion Processes. Chemical Engineering Research and Design 1999, 77, (1), 62-68. 17. Abanades, J. C.; Anthony, E. J.; Wang, J.; Oakey, J. E., Fluidized bed combustion systems integrating CO2 capture with CaO. Environmental science & technology 2005, 39, (8), 2861-2866. 18. Abanades, J. C.; Rubin, E. S.; Anthony, E. J., Sorbent cost and performance in CO2 capture systems. Industrial & Engineering Chemistry Research 2004, 43, (13), 3462-3466. 19. Abu-Zahra, M. R.; Schneiders, L. H.; Niederer, J. P.; Feron, P. H.; Versteeg, G. F., CO2 capture from power plants: Part I. A parametric study of the technical performance based on monoethanolamine. International Journal of Greenhouse gas control 2007, 1, (1), 37-46. 20. Aroonwilas, A.; Veawab, A., Integration of CO2 capture unit using single-and blended-amines into supercritical coal-fired power plants: Implications for emission and energy management. International Journal of Greenhouse Gas Control 2007, 1, (2), 143-150. 21. Romeo, L. M.; Espatolero, S.; Bolea, I., Designing a supercritical steam cycle to integrate the energy requirements of CO2 amine scrubbing. International Journal of Greenhouse Gas Control 2008, 2, (4), 563-570. 22. Zeman, F., Energy and material balance of CO2 capture from ambient air. Environmental science & technology 2007, 41, (21), 7558-7563. 23. Lara, Y.; Martínez, A.; Lisbona, P.; Bolea, I.; González, A.; Romeo, L. M., Using the second law of thermodynamic to improve CO2 capture systems. Energy Procedia 2011, 4, 20 ACS Paragon Plus Environment

Page 20 of 54

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

1043-1050. 24. Xiao, P.; Wilson, S.; Xiao, G.; Singh, R.; Webley, P., Novel adsorption processes for carbon dioxide capture within a IGCC process. Energy Procedia 2009, 1, (1), 631-638. 25. Scholes, C. A.; Smith, K. H.; Kentish, S. E.; Stevens, G. W., CO2 capture from precombustion processes—Strategies for membrane gas separation. International Journal of Greenhouse Gas Control 2010, 4, (5), 739-755. 26. Simpson, A. P.; Simon, A., Second law comparison of oxy-fuel combustion and postcombustion carbon dioxide separation. Energy Conversion and Management 2007, 48, (11), 3034-3045. 27. Amann, J.-M.; Kanniche, M.; Bouallou, C., Natural gas combined cycle power plant modified into an O2/CO2 cycle for CO2 capture. Energy Conversion and Management 2009, 50, (3), 510-521. 28. Abad, A.; Adánez, J.; García-Labiano, F.; de Diego, L. F.; Gayán, P.; Celaya, J., Mapping of the range of operational conditions for Cu-, Fe-, and Ni-based oxygen carriers in chemical-looping combustion. Chemical Engineering Science 2007, 62, (1), 533-549. 29. Richter, H. J.; Knoche, K. F. In Reversibility of combustion processes, ACS Symposium series, 1983; Oxford University Press: 1983; pp 71-85. 30. Chiesa, P.; Lozza, G.; Malandrino, A.; Romano, M.; Piccolo, V., Three-reactors chemical looping process for hydrogen production. International Journal of Hydrogen Energy 2008, 33, (9), 2233-2245. 31. Edrisi, A.; Mansoori, Z.; Dabir, B., Using three chemical looping reactors in ammonia production process–A novel plant configuration for a green production. International Journal of Hydrogen Energy 2014, 39, (16), 8271-8282. 32. Lyngfelt, A.; Leckner, B.; Mattisson, T., A fluidized-bed combustion process with inherent CO2 separation; application of chemical-looping combustion. Chemical Engineering Science 2001, 56, (10), 3101-3113. 33. Jerndal, E.; Mattisson, T.; Lyngfelt, A., Thermal analysis of chemical-looping combustion. Chemical Engineering Research and Design 2006, 84, (9), 795-806. 34. Cho, P.; Mattisson, T.; Lyngfelt, A., Comparison of iron-, nickel-, copper-and manganese-based oxygen carriers for chemical-looping combustion. Fuel 2004, 83, (9), 12151225. 35.

Leion, H.; Mattisson, T.; Lyngfelt, A., Use of ores and industrial products as oxygen 21 ACS Paragon Plus Environment

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

carriers in chemical-looping combustion. Energy & Fuels 2009, 23, (4), 2307-2315. 36. Cho, P.; Mattisson, T.; Lyngfelt, A., Carbon formation on nickel and iron oxidecontaining oxygen carriers for chemical-looping combustion. Industrial & Engineering Chemistry Research 2005, 44, (4), 668-676. 37. Adanez, J.; Abad, A.; Garcia-Labiano, F.; Gayan, P.; de Diego, L. F., Progress in chemical-looping combustion and reforming technologies. Progress in Energy and Combustion Science 2012, 38, (2), 215-282. 38. Kang, K.-S.; Kim, C.-H.; Bae, K.-K.; Cho, W.-C.; Kim, S.-H.; Park, C.-S., Oxygencarrier selection and thermal analysis of the chemical-looping process for hydrogen production. International Journal of Hydrogen Energy 2010, 35, (22), 12246-12254. 39. de Diego, L. F.; Garcı́a-Labiano, F.; Adánez, J.; Gayán, P.; Abad, A.; Corbella, B. M.; Marı́a Palacios, J., Development of Cu-based oxygen carriers for chemical-looping combustion. Fuel 2004, 83, (13), 1749-1757. 40. Ishida, M.; Jin, H., A novel chemical-looping combustor without NOx formation. Industrial & Engineering Chemistry Research 1996, 35, (7), 2469-2472. 41. Ishida, M.; Jin, H., A novel combustor based on chemical-looping reactions and its reaction kinetics. Journal of Chemical Engineering of Japan 1994, 27, (3), 296-301. 42. Karimi, M.; Rahimpour, M.; Rafiei, R.; Jafari, M.; Iranshahi, D.; Shariati, A., Reducing environmental problems and increasing saving energy by proposing new configuration for moving bed thermally coupled reactors. Journal of Natural Gas Science and Engineering 2014, 17, 136-150. 43. Jafari, M.; Rafiei, R.; Amiri, S.; Karimi, M.; Iranshahi, D.; Rahimpour, M. R.; Mahdiyar, H., Combining continuous catalytic regenerative naphtha reformer with thermally coupled concept for improving the process yield. International Journal of Hydrogen Energy 2013, 38, (25), 10327-10344. 44. Iranshahi, D.; Rafiei, R.; Jafari, M.; Amiri, S.; Karimi, M.; Rahimpour, M. R., Applying new kinetic and deactivation models in simulation of a novel thermally coupled reactor in continuous catalytic regenerative naphtha process. Chemical Engineering Journal 2013, 229, 153-176. 45. Amirabadi, S.; Kabiri, S.; Vakili, R.; Iranshahi, D.; Rahimpour, M. R., Differential evolution strategy for optimization of hydrogen production via coupling of methylcyclohexane dehydrogenation reaction and methanol synthesis process in a thermally coupled double membrane reactor. Industrial & Engineering Chemistry Research 2013, 52, (4), 1508-1522. 22 ACS Paragon Plus Environment

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Energy & Fuels

46. George, J. A.; Abdullah, M. A., Catalytic naphtha reforming. Marcel Dekker, New York 2004. 47. Rahimpour, M.; Vakili, R.; Pourazadi, E.; Iranshahi, D.; Paymooni, K., A novel integrated, thermally coupled fluidized bed configuration for catalytic naphtha reforming to enhance aromatic and hydrogen productions in refineries. International Journal of Hydrogen Energy 2011, 36, (4), 2979-2991. 48. Rahimpour, M. R.; Iranshahi, D.; Pourazadi, E.; Paymooni, K.; Bahmanpour, A. M., The aromatic enhancement in the axial‐flow spherical packed‐bed membrane naphtha reformers in the presence of catalyst deactivation. AIChE Journal 2011, 57, (11), 3182-3198. 49. Iranshahi, D.; Pourazadi, E.; Bahmanpour, A.; Rahimpour, M., A comparison of two different flow types on performance of a thermally coupled recuperative reactor containing naphtha reforming process and hydrogenation of nitrobenzene. International Journal of Hydrogen Energy 2011, 36, (5), 3483-3495. 50. Dueso, C.; Ortiz, M.; Abad, A.; García-Labiano, F.; de Diego, L. F.; Gayán, P.; Adánez, J., Reduction and oxidation kinetics of nickel-based oxygen-carriers for chemicallooping combustion and chemical-looping reforming. Chemical Engineering Journal 2012, 188, 142-154. 51. Adánez, J.; Dueso, C.; de Diego, L. F.; García-Labiano, F.; Gayán, P.; Abad, A., Methane combustion in a 500 Wth chemical-looping combustion system using an impregnated Ni-based oxygen carrier. Energy & Fuels 2008, 23, (1), 130-142. 52. Rase, H. F.; Holmes, J. R., Chemical reactor design for process plants. Wiley New York: 1977; Vol. 2. 53. Reforming, C. N., Antos, GA, Aitani, AM, Parera, JM, Eds. In Marcel Dekker: New York: 1995. 54. Liang, K.-m.; Guo, H.-y.; Pan, S.-w., A study on naphtha catalytic reforming reactor simulation and analysis. Journal of Zhejiang University. Science. B 2005, 6, (6), 590. 55. Bommannan, D.; Srivastava, R.; Saraf, D., Modelling of catalytic naphtha reformers. The Canadian Journal of Chemical Engineering 1989, 67, (3), 405-411. 56. Van Ness, H.; Smith, J. M.; Abbott, M. M., Introduction to chemical engineering thermodynamics. McGraw-Hill, NewYork 2001. 57. Perry, R.; Green, D.; Maloney, J., H., 1997, Perry’s Chemical Engineers’ Handbook. McGraw-Hill, 7th edition, ISBN 70498415, 2-7. 23 ACS Paragon Plus Environment

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

58. Iranshahi, D.; Rahimpour, M.; Asgari, A., A novel dynamic radial-flow, spherical-bed reactor concept for naphtha reforming in the presence of catalyst deactivation. International Journal of Hydrogen Energy 2010, 35, (12), 6261-6275. 59. Iranshahi, D.; Pourazadi, E.; Paymooni, K.; Rahimpour, M. R., A novel dynamic membrane reactor concept with radial‐flow pattern for reacting material and axial‐flow pattern for sweeping gas in catalytic naphtha reformers. AIChE Journal 2012, 58, (4), 12301247. 60. Mattisson, T.; Johansson, M.; Lyngfelt, A., The use of NiO as an oxygen carrier in chemical-looping combustion. Fuel 2006, 85, (5), 736-747.


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Energy & Fuels

Table Captions:

Table 1 − Specifications of reactors, feed, product and catalyst of CNR. parameter Numerical Value Naphtha feed stock 30.41×103 Reformate 24.66×103 H2/HC mole ratio 4.73 LHSV 1.25 Mole percent of hydrogen in recycle 69.5 0.5, 1.25, 6.29 Inner diameter, outer diameter and length of 1st reactor Inner diameter, outer diameter and length of 0.5, 1.67, 6.8 2nd reactor 0.5, 1.98, 7.13 Inner diameter, outer diameter and length of 3rd reactor Distillation fraction of naphtha feed and reformate TBP Naphtha feed (oC) IBP 106 10% 113 30% 119 50% 125 70% 133 90% 144 FBP 173 Typical properties of catalyst dp 1.2 Pt 0.3 Re 0.3 220 s a

ρB ε

unit kg/h kg/h − h-1 − m m m

Reformate (oC) 44 73 105 123 136 153 181 mm wt% wt% m2/g

0.3

kg/L

0.36

−


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Table 2 – Design characteristics of NR-CLC. AR: parameter Inlet temperature [K] Inside diameter [m] Heated length [m] Particle size [mm] Void fraction [-] Solid inventory [kg] Available cross sectional area for flow [m2] Air flow rate [mol s-1] Excess air [-] NiO circulation rate [mol s-1] Feed velocity [m s-1] FR parameter Inlet temperature [K] Inside diameter [m] Heated length [m] Particle size [mm] Particle density [kg m-3] Void fraction [-] Solid inventory [kg] Available cross sectional area for flow [m2] Gas flow rate [mol s-1] NiO circulation rate [mol s-1] Feed velocity [m s-1] NRT parameter Number of tubes Tubes diameter [mm]

First 840 2.65 6.29 4 0.52 42900 4.2

second 840 3.07 6.8 4 0.52 43800 5.2

1750 20% 600 0.2

2246 20% 780 0.2

First 840 3.75 6.29 4 2400 0.52 42900 4.2

second 840 4.25 6.8 4 2400 0.52 43800 5.2

210 600 0.2

284 780 0.2

first 51 125

second 91 125


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Energy & Fuels

Table 3 − Rate constants and heat of reactions for naphtha reforming.

k = A exp( B − E / 1.8T )

A

B

E

∆H 298 K

k f1

9.87

23.21

36350

71038.06

k f2

9.87

35.98

58550

-36953.33

k f3

1

42.97

63800

-51939.31

k f4

1

42.97

63800

-56597.54

K e1

1.04×10-3

46.15

46045

−

K e2

9.87

-7.12

8000

−


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Table 4 − Properties and Kinetic Parameters for the Oxidation and Reduction of the NiO18-Al2O3 Oxygen-carriers. Properties NiO content (wt %)

18

Apparent density (g cm-3)

2.5

BET surface area (m2 g-1)

7

Porosity (%)

43 Kinetic parameters

Chemical reaction rate

n

K0(mol1-nm3n-2s-1)

Ea( kj mol-1)

Reduction with CH4

0.2

0.2

5

Oxidation with O2

0.7

0.84

22


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Energy & Fuels

Table 5 − Mass & Energy balances for NR-CLC. NRT

Dej =ε

(14)

m ∂C j 1 ∂ 1 ∂ ( Ac1 )− ( Ac1 u z C j ) + ρb a ∑ν ij ri Ac ∂z ∂z Ac ∂z i =1

∂C j

j = 1, 2,..., n

∂t

i = 1, 2,..., m

m PPer ∂T ∂T 1 ∂ ( K eff AC1 n ) − a × ρb (∑ ∆H i ri ) − uZ CP n + m × 1 × U × (Ta − Tn ) + A C1 ∂z ∂z ∂z A C1 i =1

ε RTn

(15)

∂T ∂CT = ε × CT × CV n ∂t ∂t

AR

Dej

∂ 2C j ∂2Z

− uz

∂C j ∂Z

+ (1 − ε b )ν j R2 = ε

[(u ρC p ) s + (u ρC p ) g ]

(16)

∂C j ∂t

Pper Pper ∂Ta + (1 − ε b )ν j R∆H rex − m 1 ×U × (Ta − Tn ) − 2 ×U × (Ta − Tf ) ∂Z AC2 AC2

(17)

n n ∂C j ∂T ∂T 1 ∂ ( Keff' AC2 a ) = ε b ∑ C j CV j a + ε b ∑U j AC2 ∂Z ∂Z ∂t ∂t j =1 j =1

FR

Dej

∂ 2C j ∂2Z

− uz

∂C j ∂Z

+ (1 − ε b )ν j R3 = ε

[(u ρC p ) s + (u ρC p ) g ]

∂Tf ∂Z

(18)

∂C j ∂t

+ (1 − ε b )ν j R3∆H rex +

Pper2 AC3

×U × (Ta − Tf )

(19)

n n ∂Tf ∂Tf ∂C j 1 ∂ ( Keff' AC3 ) = ε b ∑ C j CV j + ε b ∑U j AC3 ∂Z ∂Z ∂t ∂t j =1 j =1

Boundary & initial conditions (20)

z = 0 : C j = C j 0 , T = T0

z = L:

∂C j ∂z

= 0,

(21)

∂T =0 ∂z

ss

(22)

ss

t = 0; C j = C j , T = T ss , Ts = Ts ; a = 1; Ergun equation (Pressure drop)

(23)

dP G (1 − ε ) 150(1 − ε ) µ =− ( + 1.75G ) dr ρ g cφs d pε 3 φs d p G: mass flux kg/m 2 =

& m Ac1

Catalyst deactivation (24)

E 1 1 da = − K d exp(− d ( − ))a 7 dt R T TR

TR = 770 K , Ed = 1.642 ×105 jmol −1 , K d = 5.926 ×10−5 h −1 29 ACS Paragon Plus Environment

Energy & Fuels

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Table 6 – Auxiliary correlations. Component heat capacity (25)

a + bT + cT 2 + dT −2 c3 / T c5 / T c1 + c2 [ ]2 + c4 [ ]2 sinh(c3 / T ) sinh(c5 / T )

(26)

Component viscosity

µ=

(27)

c1T c2 c c 1 + 2 + 42 T T

Heat transfer coefficient between gas phase and reactor wall

h c p ρµ

((

cp µ K

)2 / 3 ) =

0.458

εB

(

µ ρ ud p

(28)

)0.407

Overall heat transfer coefficient (29)

1 1 Ai ln( D0 / Di ) Ai 1 = + + U hi 2π LK w A0 h0


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Energy & Fuels

Table 7 − Comparison between model prediction and plant data for fresh catalyst. Reactor No.

No.

1 2 3

Inlet temperature (K) 1 777 2 777 3 775 Outlet temperature (K) Plant CNR NR-CLC

722 753 770

721.11 756.17 773.33

Inlet pressure (kPa) 3703 3537 3401

765.29 785.93 786.45

Catalyst Input feedstock distribution (Mole %) (wt %) 20 Paraffin 49.3 30 Naphthene 36.0 50 Aromatic 14.7 Aromatic in reformate (Mole %) plant CNR NR-CLC

− − 57.70

37.26 48.16 66.43


46.68 54.61 73.97

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Table 8- Third reactor outlet and Reformate compositions. Paraffin

Naphthene

Aromatic

Hydrogen

Light-end

Third reactor outlet composition (%w/w) CNR

13.75

0.696

26.63

5.10

53.82

NR-CLC

9.91

0.596

27.82

5.24

56.434

CNR

33.47

1.69

64.84

NR-CLC

25.85

1.56

72.59

Reformate composition (%w/w)


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Energy & Fuels

Figure Captions: Figure.1 A general scheme of the chemical-looping combustion system Figure.2 Conceptual process diagram for naphtha reforming coupled with chemical looping combustion (NR-CLC). Figure.3 A differential increment with length dz along the axial direction inside NR-CLC Figure.4 Variation of (a) paraffin and (b) naphthene molar flow rates along the length of the CNR and NR-CLC systems Figure.5 Variation of (a) Hydrogen, (b) aromatic, and (c) light end molar flow rates along the length of CNR and NR-CLC systems. Figure.6 Variation of (a) total molar flow rate and (b) the molecular weight of naphtha along the system length of the CNR and NR-CLC systems Figure.7 Variation of H2/HC molar flow ratio along the reactor length in the CNR and NRCLC systems Figure.8 Variation of mole fractions of various components along reactor length in the NRCLC (a) in air reactor (b) in fuel reactor Figure.9 (a) Thermal profiles of CNR and NR-CLC in naphtha tubes (b) Heat consumption in naphtha tubes and heat transferred from AR to NRT. Figure.10 (a) Heat consumption in FR and heat transferred from AR to FR (b) Temperature profile in the fuel reactor. Figure.11 (a) Heat generation in the AR and (b) Temperature profile in the air reactor. Figure.12 (a) The effects of naphtha flow rate and naphtha temperature on H2 production (b) The effects of naphtha flow rate and feed temperature of air reactor on H2 production.


Energy & Fuels

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Figure.1


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Furnace

Compressor Naphtha Feed

Air

Air Air + Ni

Air + Ni CH4

Recycle gas

Reactor 1

CH4

Reactor 2

Reactor 3

Hydrogen rich gas

LPG+Off gas

Stabilizer

Separator

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Reformate to gasoline pool

NiO NiO Heat transfer Ni

H2O+CO2

Ni

H2O+CO2 NRT

AR

Figure.2


FR

Energy & Fuels

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NTR Fz1

Page 36 of 54

AR

FR

Fz2

Fz3

Solid phase Heat transfer Gas phase Fz1+ dz

Fz2+ dz

Fz3+ dz

Figure.3


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140 Molar flow rate of paraffin(kmol/h)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

130 120 110 100 90 80

NR-CLC 140 120 100 80 60 40 CNR 00.51

70 60 50 40 0

0.2 0.4 0.6 0.8 Length of system (Dimensionless)

Figure.4 (a)


1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Molar flow rate of naphthene (kmol/h)

Energy & Fuels

Page 38 of 54

100 90 80 70 60 50

CNR NR-CLC

40 30

5 4 3 2 0.95

20 10 0 0


Figure.4 (b)


1 1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

molar flow rate of hydrogen (kmol/h)

Page 39 of 54

1550 1500 1490 1488 1486 0.95

1450 1400 1350

1

NR-CLC CNR

1300 1250 0


Figure.5 (a)


1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Molar flow rate of aromatic (kmol/h)

Energy & Fuels

Page 40 of 54

160 140 120 100 80

NR-CLC CNR 00.51

60 40 20 0


Figure.5 (b)


1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Molar flow rate of Light ends(kmol/h)

Page 41 of 54

740 715 690 665

NR-CLC 750 700 650 600 550 00.51 CNR

640 615 590 565 540 0


Figure.5 (c)


1

Energy & Fuels

2450 Total molar flow rate (kmol/h)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 42 of 54

2400 2350 2300 2250 2200 2150

CNR 2400 2200 NR-CLC 00.51

2100 2050 0


Figure.6 (a)


1

Page 43 of 54

28

Molecular weight (g/mol)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

27 NR-CLC 28 26 24 CNR 0 .51

26 25 24

23 0


Figure.6 (b)


1

Energy & Fuels

8 7.5 H 2 /HC m olar ratio

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 44 of 54

7

8675CNR NR-CLC 0.51

6.5 6 5.5 5 4.5 0


Figure.7


1

Page 45 of 54

1 0.8 Mole fraction

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

0.6 0.4

O 12 0.5 0 N02.51

0.2

0 0


Figure.8 (a)


1

Energy & Fuels

1 CH4 1 0.5 CO 2 0 00.51 H2O

0.8 Mole fraction

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 46 of 54

0.6 0.4 0.2

0 0


Figure.8 (b)


1

Page 47 of 54

790 780 770 Temperature (K)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

760 750 740

780 760 740 720CNR 0.51 NR-CLC

730 720 710 0


Figure.9 (a)


1

Energy & Fuels

6

7

x 10

6 5 Heat (w/m)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 48 of 54

transferred consumed

4 3

5

5

x 10

2 1 0 0

6 4 2 0.40.45 0.5

x 10

4 2 0 0.90.95 1


Figure.9 (b)


1

Page 49 of 54

5

3

x 10

2.5

Heat (w/m)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

2 1.5

transferred 0.5 01 consumed

1 0.5 0 0


Figure.10 (a)


1

Energy & Fuels

842 841 Temperature (K)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 50 of 54

840 839 838 837 836 835 0


Figure.10 (b)


1

Page 51 of 54

6

15

Heat (w/m)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

x 10

10

5

0 0


Figure.11 (a)


1

Energy & Fuels

920 900 Temperature (K)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 52 of 54

880 860 840

820 0


Figure.11 (b)


1

Page 53 of 54

424 422 420 418 416 414

2

H molar flow rate (mol/s)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

412 410 595 590

800 585

780 580

Feed molar flow rate (mol/s)

760 575

740

Temperature (K)

Figure.12 (a)


Energy & Fuels

424 422 420 418 416

2

H molar flow rate (mol/s)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 54 of 54

414 412 595 590

880 585

860 580

Feed molar flow rate (mol/s)

840 575 820

Temperature (K)

Figure.12 (b)


A Novel Chemical Looping Combustion (CLC ... - ACS Publications

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