irvan dahlan

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 Journal of Hazardous Mater ials 185 (2011) 1609–1613 Contents lists available at  ScienceDirect  Journal of Hazardous Materials  j ournal hom e p a g e :  www.elsevier.com/locate/jhazmat Short communication Sorption of SO 2  and NO from simulated ue gas over rice husk ash (RHA)/CaO/CeO 2  sorbent: Evaluation of deactivation kinetic parameters Irvan Dahlan a , Keat Teong Lee b , Azlina Harun Kamaruddin b , Abdul Rahman Mohamed b,a School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Pulau Pinang, Malaysia b School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Pulau Pinang, Malaysia a r t i c l e i n f o  Article history: Received 22 June 2010 Received in revised form 7 October 2010 Accepted 13 October 2010 Available online 20 October 2010 Keywords: Rice husk ash (RHA) Sorbent SO2/NO sorption Breakthroug h curves Deactivation kinetic model a b s t r a c t In this study, the kinetic parameters of rice husk ash (RHA)/CaO/CeO2 sorbent for SO2 and NO sorptions were inves tigat ed in a laboratory- scal e stainles s steelxed-be d react or. Dataexperiments were obtai ned from our previous results and additional independent experiments were carried out at different condi- tions. The initial sorption rate constant ( k 0 ) and deactivation rate constant (k d ) for SO 2 /NO sorptions were obtai ned fromthe nonli nearregressio n anal ysisof the exper iment al break throug h datausing deac - tivation kinetic model. Both the initial sorption rate constants and deactivation rate constants increased with increasing temperature, except at operating temperature of 170 C. The activation energy and fre- que ncyfactorfor theSO 2  sor pti on wer e found to be 18. 0 kJ/ moland 7.37×10 5 cm 3 /(g min) , respe ctivel y. Whereasthe activation ene rgyand freque ncyfacto r forthe NOsorpti on,wereestimatedto be 5.64 kJ/ mol and 2.19 ×10 4 cm 3 /(g min), respectively. The deactivation kinetic model was found to give a very good agreement with the experimental data of the SO2/NO sorptions. © 2010 Elsevier B.V. All rights reserved. 1. Intro ducti on Cleaning ue gases from sulfur oxides (SO  x ) and nitric oxides (NO  x ) has become an issue of great importance to governmental regulatory agencies and general public due to their negative effect towards the environment and human health. Normally SO  x  and NO  x , which consists of more than 98% of sulfur dioxide (SO 2 )  [1] andover 90–95 % of nit ricoxide(NO) [2], are gener ated main ly from the combus tion of fossilfuels in power stations as wel l as chemical plant s and meta llurg yprocesses.Attempts havebeen madeto nda suitable met hodfor theremovalof SO 2  and NO simultaneo usly.Dry sorption method is now considered to be the most attractive way to treat waste gases containing SO 2  and NO due to the drawbacks of wet sorption methods [3,4]. There are several dry-type sorbents that have been considered in the previous study for simultaneous removal of SO 2  and NO. RHA,which is produced from the burning of ri ce husk, has been chosenin thi s stu dy as a rawmaterial in theprepa rat ionof dry -type sor bent since it is availa ble abundantl y in ric e-prod uci ng countries like Malaysia. RHA also contains high amount of silica. However, RHA has low sorption capacity when used alone to remove acidic gases. There fore, this agricu ltura l waste -silic eous start ing material needs to be activated with other materials and the silica in RHA Correspond ing author. Tel.: +60 4 5996410; fax: +60 4 5941013. E-mail address: [email protected] (A.R. Mohamed). plays an important role in the formation of reactive species which is responsible for high sorption capacity [5,6]. Previously, we had reported the sorption characteristics of SO 2 and NO over rice husk ash (RHA)-based sorbent at low temper- ature [5–11].  Nevertheless, our previous reports only dealt with activity measurement related to sorbent preparation conditions and effects of reactor operating conditions. Our previous results alsoshowed thatthe highes t sorpt ion capac ity for the simu ltane ous removal of SO 2  andNO wasobtai nedusing RHA/CaO/CeO 2  sorbent. Curre ntly,the optimum prepa rativ e para meter s for this kind of sor- bent had also been reported [12].  On the other hand, the reaction between the siliceous/calcium dry-type sorbents and SO 2 /NO is very scarc ely repor ted. The reaction betwe en this silice ous/c alciu m dry-type sorbents and SO 2 /NO are very complicated due to the complex composition of the sorbent. The sorption of these pol- lutant gases (SO 2 /NO) on the sorbents is not a simple physical sorption processes, but also may be described as chemisorption or as gas–solid non-catalytic reactions. There are various kinetic models that have been employed to estimate kinetic parameters in gas–solid reaction, mainly involves single compon ent sorbent (such as CaO, Ca( OH) 2  and CaCO 3 )andit wascarriedoutmainl y at high ope rat ing temper at ure. These kin et- ics mode ls includ ed shrin king unrea cted core mode l [13], changing grain size model [14]  and random pore model  [15].  Most of these models contain large number of adjustable parameters related to the pore structure, to the product layer and pore diffusion resis- tances as well as the surface sorption rate parameters. In addition, 0304-3894/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2010.10.053

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  • 7/26/2019 irvan dahlan

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    Journal of Hazardous Materials 185 (2011) 16091613

    Contents lists available atScienceDirect

    Journal of Hazardous Materials

    j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j h a z m a t

    Short communication

    Sorption of SO2and NO from simulated flue gas over rice husk ash

    (RHA)/CaO/CeO2sorbent: Evaluation of deactivation kinetic parameters

    Irvan Dahlan a, Keat Teong Lee b, Azlina Harun Kamaruddin b, Abdul Rahman Mohamed b,

    a School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Pulau Pinang, Malaysiab School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Pulau Pinang, Malaysia

    a r t i c l e i n f o

    Article history:

    Received 22 June 2010Received in revised form 7 October 2010

    Accepted 13 October 2010

    Available online 20 October 2010

    Keywords:

    Rice husk ash (RHA)

    Sorbent

    SO2/NO sorption

    Breakthrough curves

    Deactivation kinetic model

    a b s t r a c t

    In this study, the kinetic parameters of rice husk ash (RHA)/CaO/CeO 2 sorbent for SO2 and NO sorptions

    were investigated in a laboratory-scale stainless steelfixed-bed reactor. Dataexperiments were obtained

    from our previous results and additional independent experiments were carried out at different condi-

    tions. The initial sorption rate constant (k0) and deactivation rate constant (kd) for SO2/NO sorptions

    were obtained from the nonlinearregression analysisof the experimental breakthrough datausing deac-

    tivation kinetic model. Both the initial sorption rate constants and deactivation rate constants increased

    with increasing temperature, except at operating temperature of 170 C. The activation energy and fre-

    quencyfactorfor theSO2sorption were found to be 18.0 kJ/moland 7.37105 cm3/(g min), respectively.

    Whereasthe activation energyand frequencyfactor forthe NOsorption,wereestimated to be 5.64 kJ/mol

    and 2.19104 cm3/(g min), respectively. The deactivation kinetic model was found to give a very good

    agreement with the experimental data of the SO2/NO sorptions.

    2010 Elsevier B.V. All rights reserved.

    1. Introduction

    Cleaning flue gases from sulfur oxides (SOx) and nitric oxides

    (NOx) has become an issue of great importance to governmental

    regulatory agencies and general public due to their negative effect

    towards the environment and human health. Normally SOx and

    NOx, which consists of more than 98% of sulfur dioxide (SO 2)[1]

    andover 9095% of nitricoxide(NO) [2], are generated mainly from

    the combustion of fossil fuels in power stations as well as chemical

    plants and metallurgy processes.Attempts havebeen madeto finda

    suitable methodfor theremovalof SO2and NO simultaneously.Dry

    sorption method is now considered to be the most attractive way

    to treat waste gases containing SO2 and NO due to the drawbacks

    of wet sorption methods[3,4].There are several dry-type sorbents

    that have been considered in the previous study for simultaneous

    removal of SO2and NO.RHA, which is produced from the burning of rice husk, has been

    chosenin this study as a rawmaterial in thepreparationof dry-type

    sorbent since it is available abundantly in rice-producing countries

    like Malaysia. RHA also contains high amount of silica. However,

    RHA has low sorption capacity when used alone to remove acidic

    gases. Therefore, this agricultural waste-siliceous starting material

    needs to be activated with other materials and the silica in RHA

    Corresponding author. Tel.: +60 4 5996410; fax: +60 4 5941013.

    E-mail address: [email protected](A.R. Mohamed).

    plays an important role in the formation of reactive species which

    is responsible for high sorption capacity[5,6].Previously, we had reported the sorption characteristics of SO2

    and NO over rice husk ash (RHA)-based sorbent at low temper-

    ature [511]. Nevertheless, our previous reports only dealt with

    activity measurement related to sorbent preparation conditions

    and effects of reactor operating conditions. Our previous results

    alsoshowed thatthe highest sorption capacity for the simultaneous

    removal of SO2andNO wasobtainedusing RHA/CaO/CeO2sorbent.

    Currently,the optimum preparative parameters for this kind of sor-

    bent had also been reported[12].On the other hand, the reaction

    between the siliceous/calcium dry-type sorbents and SO2/NO is

    very scarcely reported. The reaction between this siliceous/calcium

    dry-type sorbents and SO2/NO are very complicated due to the

    complex composition of the sorbent. The sorption of these pol-

    lutant gases (SO2/NO) on the sorbents is not a simple physicalsorption processes, but also may be described as chemisorption or

    as gassolid non-catalytic reactions.

    There are various kinetic models that have been employed to

    estimate kinetic parameters in gassolid reaction, mainly involves

    single component sorbent (such as CaO, Ca(OH)2and CaCO3)andit

    wascarried outmainly at high operating temperature. These kinet-

    ics models included shrinking unreacted core model [13], changing

    grain size model[14]and random pore model[15].Most of these

    models contain large number of adjustable parameters related to

    the pore structure, to the product layer and pore diffusion resis-

    tances as well as the surface sorption rate parameters. In addition,

    0304-3894/$ see front matter 2010 Elsevier B.V. All rights reserved.

    doi:10.1016/j.jhazmat.2010.10.053

    http://localhost/var/www/apps/conversion/tmp/scratch_10/dx.doi.org/10.1016/j.jhazmat.2010.10.053http://localhost/var/www/apps/conversion/tmp/scratch_10/dx.doi.org/10.1016/j.jhazmat.2010.10.053http://www.sciencedirect.com/science/journal/03043894http://www.elsevier.com/locate/jhazmatmailto:[email protected]://localhost/var/www/apps/conversion/tmp/scratch_10/dx.doi.org/10.1016/j.jhazmat.2010.10.053http://localhost/var/www/apps/conversion/tmp/scratch_10/dx.doi.org/10.1016/j.jhazmat.2010.10.053mailto:[email protected]://www.elsevier.com/locate/jhazmathttp://www.sciencedirect.com/science/journal/03043894http://localhost/var/www/apps/conversion/tmp/scratch_10/dx.doi.org/10.1016/j.jhazmat.2010.10.053
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    1610 I. Dahlan et al. / Journal of Hazardous Materials 185 (2011) 16091613

    it is complicated to incorporate them without having to perform

    lengthy computer programs. Therefore in this study, the simplified

    deactivation kinetic model was used to estimate kinetic parame-

    ters against other models. The breakthrough curves data obtained

    from our previous results (SO2and NO sorptions) [11] was fitted to

    deactivation kinetic model. In the present work,kinetic parameters

    such as deactivation rate constant, initial sorption rate constant,

    activation energy and frequency (pre-exponential) factor of the

    SO2

    an NO sorptions were estimated from the breakthrough data

    through nonlinear regression analysis. In chemical engineering,the

    rate of reaction is a prerequisite to the design and evaluation of

    fixed-bed reactor performance especially under dry-type gassolid

    reactionsorption processes.

    2. Experimental

    2.1. Preparation of sorbent

    RHA-based sorbents (RHA/CaO/CeO2) were prepared from

    rice husk ash (RHA), CaO (BDH Laboratories, England) and

    Ce(NO3)36H2O (Fluka, 98%). The raw RHA was collected directly

    without any pretreatment from Kilang Beras & Minyak Sin Guan

    Hup Sdn. Bhd., Nibong Tebal, Malaysia. Prior to use, the RHA wassievedto produce less than 200m particle size. Thechemicalcom-

    position of raw RHA was 68.0% SiO2, 2.30% K2O, 1.20% P2O5, 0.71%

    MgO, 0.59% CaO, 0.32% SO3, 0.32% Cl2O, 0.16% Al2O3, 0.40% others

    and 26.0% LOI. The preparation method was based on the optimum

    hydration conditions reported in our previous studies [12].

    2.2. Activity test

    The sorption/activity of the prepared sorbents was tested in a

    laboratory-scale stainlesssteel fixed-bed reactor (Swagelok,10 mm

    ID, 50cm length) which was vertically fitted in a tube furnace (Lin-

    berg/Blue M). The schematic diagram and details of the activity

    study is presented elsewhere [7]. The experiments were conducted

    at various reactor temperature range of 70170

    C while maintain-ing the simulated flue gas under the fixed condition of 2000 ppm

    SO2, 500 ppm NO, 10% O2, 10% RH, balance N2 with total gas flow

    rate of 150ml/min. Other operating conditions are given in our

    previous study[11].

    2.3. Kinetic parameters estimation of RHA/CaO/CeO2sorbent

    using deactivation kinetic model.

    The analysis of kinetic parameters was carried out using

    breakthrough data of single component gases of SO2 and NO,

    respectively. The deactivation kinetic parameters such as initial

    sorption rate constants (k0) and deactivation rate constants (kd)

    were calculated from breakthrough curve analysis. The outline of

    theanalysisusing deactivationkinetic modeling is given as follows.As in a typical gassolid reaction, pore structure, active surface

    area and activity per unit area of the solid reactant have significant

    effects on the reaction rate. In the deactivation model, the effects

    of all these factors are combined in an activity term (a) introduced

    into the sorption rate expression and is written in Eq. (1)[16].

    da

    dt =kdC

    man (1)

    where kd is the deactivation rate constants(min1), Cis theconcen-

    tration of the reactant gas (kmol/m3),tis the reaction time (min),

    and m and n areexponential coefficients. Assuming thatthe concen-

    tration of the reactant gas is independent along the reactor ( m = 0)

    and the deactivation of the sorbent is first-order with respect to

    the solid active site (n = 1), integration of Eq. (1) gives the following

    expression.

    a = a0 exp(kdt) (2)

    Furthermore, the following basic assumptions were made in the

    derivation of the deactivation model, such as isothermal and

    pseudo-steady state conditions, and axial dispersion in the fixed

    bedreactor andany mass transfer resistances were neglected. Con-

    sidering these assumptions, and the initial activity (a0) of the solid

    as unity, the pseudo-steady state species conservation equation forgases in the fixed bed reactor is given by Eq. (3)[1618].

    Q dC

    dW =k0Ca (3)

    where Qis thevolumetric flowrate(m3/min), Wis thesorbentmass

    (kg) and k0 is the initial sorption rate constant (m3 kg1 min1).

    Combining Eqs.(2) and (3)and solving these equations will yield

    Eq.(4)

    C

    C0=exp[k0Bexp(kdt)] (4)

    wherebyB is equal toW/Qand this kinetic model is known as the

    zeroth solution of deactivation model, which predicts the behav-

    ior of breakthrough curves for a gassolid non-catalytic reaction.

    This solution assumes a fluid phase concentration that is indepen-

    dent of deactivation process along the reactor. However, it would

    be reasonable to expect the deactivation rate to be concentration

    dependent and axial position dependent in the fixed bed reactor.

    In order to find analytical solutions of Eqs.(1) and (2)by con-

    sidering concentration and axial position dependents in the fixed

    bedreactor(m = n = 1), iterativeprocedurewas applied. The method

    used was similar to the method for the estimated solution of non-

    linear equations proposed by Dogu[19].In this procedure, Eq.(4)

    was substituted into Eq.(1) withm = n = 1 and the first estimated

    value forthe activity (a) term wasobtained byintegrating theequa-

    tion. Then, the estimated value for the activity (a) term expression

    was substituted into Eq.(3),and integration of this equation gave

    the following corrected solution for the breakthrough curve.

    C

    C0=exp

    1 exp(k0B[1 exp(kdt)])

    1 exp(kdt) exp(kdt)

    (5)

    This Eq.(5)is also known as the solution of two-parameter deac-

    tivation kinetic model. Deactivation rate constant (kd) and initial

    sorption rateconstant (k0) wasthen calculated by using a nonlinear

    regression technique.

    A commercial software, MATHEMATICA ver. 5.2 (Wolfram

    Research Inc.), was used for nonlinear regression analysis together

    with the experimental/breakthrough datato find the rate constants

    for the model. In order to obtain the best fitting results, an error

    minimization technique was also applied and included after run-

    ning the main program code of MATHEMATICA. MATHEMATICA

    software was run under Microsoft Windows XP Professional (ver.

    2002) environment.

    Based on the analysis of the experimental breakthrough data at

    different temperatures, the initial sorption rate constants (k0) can

    be obtained by fitting Eq. (5) using nonlinear regression technique.

    Then, Arrhenius equation[16]was used for the determination of

    activation energy and frequency (pre-exponential) factor for SO2and NO sorptions at different temperatures, and is given in Eq.(6).

    k0 =A exp

    Ea

    RT

    (6)

    whereA is a frequency (pre-exponential) factor, Eais the activation

    energy,R is the gas constant (8.314J/(mol K)) andTis the temper-

    ature (K).

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    I. Dahlan et al. / Journal of Hazardous Materials 185 (2011) 16091613 1611

    Table 1

    Rate parameters obtained from the breakthrough data at different temperature.

    Temp. (C) k0 (W/Q) k0(cm3 /(gmin)) kd(min1) R2

    SO2 sorption NO sorption SO2sorption NO sorption SO2 sorption NO sorption SO2sorption NO sorption

    70 4.06 10.22 1.22E+03 3.06E+03 0.12 0.11 0.987 0.989

    87 5.84 11.00 1.75E+03 3.30E+03 0.15 0.12 0.975 0.990

    100 8.57 11.45 2.57E+03 3.43E+03 0.20 0.126 0.972 0.954

    120 10.85 13.38 3.25E+03 4.01E+03 0.21 0.128 0.983 0.976

    150 13.12 14.56 3.93E+03 4.36E+03 0.23 0.130 0.991 0.964

    170 11.69 15.78 3.50E+03 4.73E+03 0.24 0.135 0.965 0.957

    3. Results and discussion

    Fig. 1a and b shows the experimental SO2and NO breakthrough

    curves obtained under various operating temperatures, respec-

    tively. The initial sorption rate constants (k0) and deactivation rate

    constants (kd) values were estimated by nonlinear fitting of Eq.(5)

    to the experimental SO2 and NO breakthrough curves at different

    temperatures. The results of rate parameters from the regression

    analysis of the dataobtained withRHA/CaO/CeO2 sorbents at differ-

    enttemperatures aregiven in Table 1. The accuracy of theproposed

    deactivation kinetic model was assessed from the coefficient of

    determination (R

    2

    ) which was found to be 0.95 or higher. Otherkind of regression results (including statistical analysis) could be

    obtained from the nonlinear regression analysis after running the

    main program code of MATHEMATICA.

    The initial sorption rate constants and deactivation rate

    constants, as expected, increased with increasing temperature

    (Table 1). However, at operating temperature of 170 C, the ini-

    tial sorption rate constant for SO2 was decreased. The decrease in

    the rate of SO2 sorption at higher temperatures might be due to

    Fig. 1. Effect of operating temperature on the (a) SO 2and (b) NO sorptions.

    water that accumulated and gas dissolving on the RHA/CaO/CeO2sorbent surface was reduced [11]. The predictions of the break-

    through curves from Eq.(5)at different temperatures using these

    rate constants are also shown in Fig. 1,whereby the deactivation

    kinetic model shows good agreement with the experimental data

    at different temperatures. As predicted for SO2 sorption at high

    temperature (170 C), the breakthrough curves shifted to shorter

    time (Fig. 1(a)). For NO sorption, the initial sorption rate con-

    stants still increasedat high temperature (170 C) andthe resulting

    breakthrough curves shifted to longer time (Fig. 1(b)). This might

    be attributed to a lesser amount of water accumulated on the

    RHA/CaO/CeO2 sorbent surface thus allowing the metal species(CeO2) present in the sorbent to become more active [11].

    Based on the data obtained in Table 1,Arrhenius equation (Eq.

    (6))was used for the estimation of activation energy (Ea) and fre-

    quency (pre-exponential) factor (A) for SO2 and NO sorptions at

    different temperatures. Fig.2(a)and(b)showsln k0 versus1/Tplots

    for SO2 and NO sorptions, respectively at different temperatures.

    The plots were found to yield a straight line indicating that the

    SO2sorption

    y = -2165.3x + 13.51

    R2= 0.9428

    7.0

    7.2

    7.4

    7.6

    7.8

    8.0

    8.2

    8.4

    8.6

    b

    a

    3.0E-032.8E-032.6E-032.4E-032.2E-032.0E-03

    1/T (K-1

    )

    ln(k

    o)

    NO sorption

    y = -678.48x + 9.9921

    R2= 0.9844

    7.9

    8.0

    8.1

    8.2

    8.3

    8.4

    8.5

    3.0E-032.8E-032.6E-032.4E-032.2E-032.0E-03

    1/T (K-1

    )

    ln(k

    o)

    Fig. 2. Arrhenius plot of sorption rate constant versus reciprocal of operating tem-

    perature for (a) SO2 and (b) NO sorptions.

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    1612 I. Dahlan et al. / Journal of Hazardous Materials 185 (2011) 16091613

    Fig. 3. Comparison between predicted and experimental breakthrough curves at

    two different experimental conditions.

    sorption rate constant obtained from deactivation kinetic model do

    follow the Arrhenius law as in Eq.(6).Accordingly, the slope of the

    plot equal to Ea/R and intercept equivalent to lnA, from which acti-

    vation energy(Ea) andfrequencyfactor (A)forSO2 andNOsorptionscan be obtained, respectively.

    The value of frequency factor (A) for SO2and NO sorptions were

    calculated to be 7.37 105 cm3/(g min) and 2.19104 cm3/gmin,

    respectively. Whereas the activationenergy (Ea) values determined

    for the SO2 and NO sorptions were 18.0 kJ/mol and 5.64kJ/mol,

    respectively. The activation energy of the SO2 sorption at low

    temperature using the RHA/CaO/CeO2 sorbent was found to be

    slightly higher as compared to sorbent prepared from coal fly

    ash/Ca(OH)2 (14.9415.47 kJ/mol)[20], activated carbon from oil

    palm shell with KOH impregnation (13.2 kJ/mol) [21] and acti-

    vated carbon from oil palm shell (12.6kJ/mol) [22]. However,

    the activation energy obtained in this study was lower than

    the SO2 sorption when Ca(OH)2 (32 kJ/mol) [23] and coal fly

    ash/CaO/CaSO4 (22.9 kJ/mol) [24] were used as the sorbent, andalso much lower than the reported value by Irabien et al. [25]

    and Renedo and Fernandez [26] using Ca(OH)2(75kJ/mol) and coal

    fly ash/Ca(OH)2/CaSO4(57.7 kJ/mol), respectively. Apart from that,

    this activation energyfor SO2sorption at lowtemperature wasalso

    found to be similar as compared to sorbents prepared from vari-

    ous type of CaCO3 (15.219.5 kJ/mol)[27].For the case of the NO

    sorption, the value of activation energy was also much lower than

    previously reported in the literature which include the sorbent pre-

    pared from V2O5/NH4Br/TiO2/SiO2 (30.1 kJ/mol)[28],V2O5Al2O3(53.56 kJ/mol)[29]and Fe-ZSM-5 (54 kJ/mol)[30].However, most

    ofthe reportedstudiesfor NOsorptionwerecarriedoutat high tem-

    perature processes. The relatively small activation energy obtained

    in this study suggested an easy sorption process of SO2and NO by

    this kind of sorbent. In other word, the sorption between SO2/NOand the reference sorbent synthesized from RHA/CaO/CeO2is eas-

    ier to occur due to the easier access of SO2and NO molecules to the

    active species in the sorbent.

    In order to verify the proposed deactivation kinetic model,

    additional independent experiments were carried out at different

    conditions using 0.5g RHA/CaO/CeO2sorbent. The first experiment

    was conducted at initial condition of 1500 ppm SO2, 1200ppmNO,

    10% O2, 60% RH, balance N2 and 150 ml/min of total flow rate at

    a reactor temperature of 80 C. While the second experiment was

    conducted at the following conditions of 1800 ppm SO2, 800ppm

    NO, 10% O2, 40% RH, balance N2 and 150 ml/min of total flow rate

    at a reactor temperature of 110 C.Fig. 3shows the experimental

    versus predicted breakthrough curves of SO2 and NO sorptions at

    two different experimental conditions. It was shown that the deac-

    SO2 sorption

    0.0

    0.1

    0.20.3

    0.4

    0.5

    0.6

    0.7

    0.8

    0.9

    1.0a

    b

    1.00.90.80.70.60.50.40.30.20.10.0

    Experimental C/Co

    PredictedC/Co

    NO sorption

    0.0

    0.1

    0.2

    0.3

    0.4

    0.5

    0.6

    0.7

    0.8

    0.9

    1.0

    1.00.90.80.70.60.50.40.30.20.10.0

    Experimental C/Co

    Pre

    dictedC/Co

    Fig. 4. Plot of all experimental C/C0vs predicted C/C0under various operating con-

    ditions for (a) SO2 and (b) NO sorptions.

    tivation kinetic model provided a very accurate description of the

    experimental data.

    For further confirmation, the breakthrough curvesdata fromour

    previous results [11] was fitted to the proposeddeactivation kinetic

    model. The comparison between predicted breakthrough curves

    (obtained with deactivation kinetic model) with the experimen-

    tal results was performed for all the SO2/NO sorption experiments

    under various operating conditions. Fig. 4(a) and (b) shows the

    comparison between the experimentalC/C0 versus predictedC/C0ofSO2 and NO sorptionsin all experiments, respectively. The results

    indicated that the proposed model prediction agrees reasonably

    well with the experimental data of the SO2/NO sorptions within

    the range of 10% experimental error.

    4. Conclusions

    The deactivation model wasapplied successfullyto describe the

    experimental breakthrough curves for the sorption of SO2

    and NO

    from simulated flue gas in a fixed-bed reactor over RHA/CaO/CeO2sorbent. Thebreakthrough data obtained forboth SO2and NO sorp-

    tions was fitted to the proposed deactivation kinetic model. Both

    the initial sorption rate constants and deactivation rate constants

    increased with increasing temperature, except at operating tem-

    perature of 170C whereby theinitialsorptionrateconstantfor SO2decreased. The breakthrough curves obtained by using the devel-

    oped deactivationkinetic model were found to fit theexperimental

    breakthrough curves very well.

    Acknowledgements

    Theauthors wish to acknowledge thefinancialsupport from the

    Ministry of Science, Technology and Innovation (MOSTI) Malaysia,

  • 7/26/2019 irvan dahlan

    5/5

    I. Dahlan et al. / Journal of Hazardous Materials 185 (2011) 16091613 1613

    Yayasan Felda andUniversiti Sains Malaysia (ShortTerm Grant A/C.

    6035278 and RU Golden Goose Project Grant A/C. 814004).

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