Thermal behavior and hydrogen production of methanol steam reforming and autothermal reforming with spiral preheating

Transcription

1 Ntionl Cheng Kung University From the SelectedWorks of Wei-Hsin Chen Mrch, 11 Therml ehvior nd hydrogen production of methnol stem reforming nd utotherml reforming with spirl preheting Wei-Hsin Chen, Ntionl Cheng Kung University Aville t:

2 interntionl journl of hydrogen energy 6 (11) 97e48 Aville t journl homepge: Therml ehvior nd hydrogen production of methnol stem reforming nd utotherml reforming with spirl preheting Wei-Hsin Chen*, Yu-Jhih Syu Deprtment of Greenergy, Ntionl University of Tinn, Tinn 7, Tiwn, ROC rticle info Article history: Received 1 Octoer 1 Received in revised form 1 Decemer 1 Accepted 1 Decemer 1 Aville online 1 Jnury 11 Keywords: Hydrogen production nd genertion Therml chrcteristics Methnol stem reforming (MSR) nd utotherml reforming (ATR) H yield Spirl preheting strct The present study ims to investigte the therml ehvior nd hydrogen production chrcteristics from methnol stem reforming (MSR) nd utotherml reforming (ATR) under the effects of Cu-Zn-sed ctlyst nd spirl preheting. Two different rection tempertures of 5 nd C re tken into ccount. Menwhile, the O/C rtio (i.e. the molr rtio etween O nd methnol) nd S/C rtio (i.e. the molr rtio etween stem nd methnol) re controlled in the rnges of e.5 nd 1e, respectively. The condition of O/C ¼ represents the rection of MSR. By monitoring the supplied power into the rector with fixed gs hourly spce velocity (GHSV) of 7, h 1, the experimentl results indicte tht n exothermic rection from ATR cn e ttined once the O/C rtio is s high s.15. Incresing O/C rtio cuses more het relesed from the rection, this results in the decrese in the frequency of supplied power, especilly t O/C ¼.5. It is noted tht the concentrtion of CO in the product gs is quite low compred to tht of CO. An increse in O/C rtio tes the concentrtion of H from the consumption of per mol methnol; however, the H yield in terms of thermodynmic nlysis is incresed. On ccount of the utiliztion of spirl preheting on the rectnts, within the investigted operting conditions the methnol conversion nd hydrogen yield were lwys higher thn 95 nd 9%, respectively. A comprison suggests tht the methnol conversion from ATR of methnol with spirl preheting is superior to those of other studies. Copyright ª 1, Hydrogen Energy Pulictions, LLC. Pulished y Elsevier Ltd. All rights reserved. 1. Introduction Recent progress in the development of fuel cells hs mde hydrogen economy ecome promising vision for prospective energy system. Typiclly, the hydrogen economy involves hydrogen production, distriution nd delivery, storge, conversion, end-use, infrstructure nd others [1]. Accordingly, it is known tht hydrogen production is the first step to estlish hydrogen economy. The sources of producing hydrogen include fossil fuels, iomss nd wter nd the production process cn e triggered y therml, nucler or renewle energy [e4]. To dte, hydrogen genertion from nturl gs through stem methne reforming (SMR) commnds the production of commercilly ffordle hydrogen [5]. Hydrogen is usully produced in lrge-scle centrlized fcilities nd t the present time it is minly consumed for mmoni (or fertilizer) synthesis nd the reking down of hevier crude oils [1,6]. While the hydrogen economy is eing developing, hydrogen storge hs een identified s significnt technologicl rrier for the pplictions of hydrogen in vehicles or trnsporttion system [7,8]. In this spect, methnol is regrded s * Corresponding uthor. Tel.: þ ; fx: þ E-mil ddress: weihsinchen@gmil.com (W.-H. Chen) /$ e see front mtter Copyright ª 1, Hydrogen Energy Pulictions, LLC. Pulished y Elsevier Ltd. All rights reserved. doi:1.116/j.ijhydene

3 98 interntionl journl of hydrogen energy 6 (11) 97e48 fesile liquid fuel for on-ord hydrogen production. Methnol is fetured y its higher hydrogen to cron rtio; it is highly miscile with wter nd its energy density is high [9].In contrst to SMR, methnol stem reforming (MSR) cn e triggered t lower tempertures (e C) nd t tmospheric pressure [1]. Therefore, MSR is simple nd efficient wy of producing hydrogen on smll scle fcilities. However, MSR is n endothermic rection in nture nd it is expressed y Rectnts inlet Glss ed Ctlyst Thermocouple Gs inlet Liquid inlet CH OH þ H O/CO þ H DH 98 ¼ 49:47 kj mol 1 (1) The endothermic rection mens tht extr energy or het is required to excite the rection of hydrogen production. This restricts the pplictions of MSR utilized on trnsporttion system. While methnol rects with stem, if some oxygen is lso trnsported into the rector, the hydrogen production process my turn the endothermic rection into the exothermic rection. Once the exothermic stte is reched, the rection of hydrogen production cn proceed utomticlly. Under such sitution, the rection is nmed s utotherml reforming (ATR) of methnol [1], lso clled oxidtive stem reforming of methnol (OSRM) [11,1]. ATR of methnol cn e cst into the following generl form [1,14]. CH OH þ ð1 ÞH O þ O /CO þ ð ÞH DH 98 ¼ 49:5 41:8 kj mol 1 () The eqution revels tht more energy will e lierted from the rection if more oxygen is fed; however, hydrogen yield is lso reduced. As mtter of fct, ATR of methnol inherently is comintion of prtil oxidtion (POX) nd stem reforming (SR) processes of methnol [15]. POX of methnol is written s CH OH þ 1 O /CO þ H DH 98 ¼ 19:kJmol 1 () The foregoing eqution is n exothermic rection. Accordingly, het lierted from POX of methnol is le to e used to drive SR, therey implementing hydrogen production utomticlly. Stinless steel mesh Flow direction Flow direction Prehet tue Fig. e Schemtics of () internl structure of rection tue nd () spirl preheter outside the rection tue. As fr s POX is concerned where the rections of hydrocrons re in n environment with insufficient oxygen, the chemicl kinetics of POX is usully descried y Arrhenius lw [16,17], implying tht higher rection temperture is conducive to fuel conversion. On the other hnd, from thermodynmic point of view, incresing rection temperture will lso fcilitte the forwrd rection of SR, s consequence of SR eing chrcterized y endothermic rection [1]. The dvntges of rectnt preheting on the performnce of chemicl rections hve een reported in some studies [18e]. As mentioned erlier, ATR of methnol is relted POX nd SR rections of methnol. Consequently, if rectnts re preheted prior to ATR of methnol, it is nticipted tht efficiency of the rection will e promoted. A review of pst literture suggests tht numer of studies hve een crried out to figure out the rection chrcteristics of ATR of methnol. Most of the ttention ws pid A D F G Tle 1 e Properties of dopted ctlyst nd ctlyst ed s well s operting conditions of stem reforming nd utotherml reforming of methnol. B M N C D L E H Fig. 1 e A schemtic of experimentl system nd procedure (A: N ; B: ir; C: controller redout; D: flow rte controller; E: gs mixer; F: feed liquid; G: pump; H: rector; I: power controller; J: recorder; K: condenser; L: drier; M: gs chromtogrphy; N: gs nlyzer). K J I Ctlyst (Sud-Chemie MDC-) Geometry of ctlyst pellet (e) Cylinder Component (wt%) CuO: 4; ZnO: 47; A1 : lnce Ctlyst size (dimeter height, mm).. BET surfce re (m g 1 ) 7 Ctlyst ed Porosity (e). Volume (cm ) 11.4 Height (cm) Operting conditions Residence time (s).5 Flow rte of feed liquid (cc min 1,5 C).4 Temperture ( C) 5 nd S/C rtio (e) 1, 1.5, O/C rtio (e),.15,.5,.5 Molr rtio etween stem nd methnol. Molr rtio etween oxygen (O ) nd methnol.

4 interntionl journl of hydrogen energy 6 (11) 97e48 99 Tle e Flow rtes of ir, O nd N in the feed gs t vrious operting tempertures nd O/C rtios (S/C [ 1.5). Temperture ( C) Volumetric flow rte of feed gs, ir þ N (cc min 1,5 C) O/C rtio Flow rte of ir (cc min 1,5 C) Flow rte of N (cc min 1,5 C) to preprtion of ctlyst [9,14,15,,4] nd the performnce of hydrogen production t vrious operting conditions [1,5e7]. However, little informtion is ville on therml ehvior of ATR of methnol. In order to clrify the therml chrcteristics of MSR nd ATR, the interest of the present study is to explore the vrition of power supply for developing the chemicl rections with the id of Cu-Zn-sed ctlyst. Specificlly, power supplied for triggering MSR nd ATR t vrious operting tempertures s well s O/C nd S/C rtios will e monitored nd compred with ech other to recognize the performnces of MSR nd ATR under the impct of the vried prmeters mentioned ove. At the sme time, to improve the performnce of hydrogen production from MSR nd ATR, the rectnts will e heted using spirl preheter prior to entering the rector.. Experimentl.1. Experimentl system nd pprtus A schemtic of the experimentl system is sketched in Fig. 1. The system cn roughly e divided into four units. These units were mde up of feeding unit, rection unit, product C O/C= O/C=.15 O/C=.5 O/C=.5 Temperture ( C) Temperture ( C) 5 4 C strt feeding O/C= O/C=.15 O/C=.5 O/C=.5 strt feeding Fig. e Temporl distriutions of () supplied energy nd power nd () rection temperture (O/C [.15, S/C [ 1.5 nd set temperture [ 5 C). Fig. 4 e Temporl distriutions of rection temperture under vrious O/C rtios t the operting tempertures of () 5 nd () C (S/C [ 1.5).

5 4 interntionl journl of hydrogen energy 6 (11) 97e48 gs tretment unit nd gs nlysis unit. The feeding unit comprised n ir nd N steel cylinders, gs mixer, two electric flow rte controllers (KD-4) nd controller redout (Brooks 585E) used for prepring the feed gs. Menwhile, n isocrtic pump (LAllince Series II Pump) ws utilized to control the flow rte of the feed liquid, which ws mixture of wter nd methnol. In the rection unit, rector, power controller nd recorder were included. Fig. 5 e Temporl distriutions of supplied power t 5 C with O/C[ (), ().15, (c).5 nd (d).5 nd t C with O/C[ (e), (f).15, (g).5 nd (h).5 (S/C [ 1.5).

6 interntionl journl of hydrogen energy 6 (11) 97e48 41 The rector hd qurtz tue ( mm i.d.) which ws enclosed y heter to trigger chemicl rections. The heter ws controlled y power controller. The internl structure of the tue, consisting of the lyers of glss ed, ctlyst pellet nd steel mesh, is demonstrted in Fig.. A K-type thermocouple ws lso instlled in the tue to detect the rection temperture in the ctlyst ed nd the mesured temperture ws used to provide reference for the power controller. The temperture nd power signls were recorded y recorder. To fcilitte ATR of methnol, the rectnts were preheted y flowing through coiled copper tue which surrounded the qurtz tue, s shown in Fig., ccomplishing the spirl preheting. The product gs tretment unit ws composed of condenser nd dryer; they were employed to remove the moisture contined in the product gs in two stges. The gs nlysis unit consisted of gs nlyzer (GA, Fuji ZRJF5Y- AERYR-YKLYYCY-A) nd gs chromtogrphy (GC, SRI 1C TCD) to mesure the volumetric concentrtions of CO, CO nd H... Experimentl procedure The experimentl procedure is lso sketched in Fig. 1. In the feeding unit, ir nd N were supplied from the two steel cylinders nd lended in the gs mixer. The volumetric flow rtes of the two gses were individully controlled y the electric flow rte controllers nd the controller redout. Menwhile, the volumetric flow rte of the liquid solution (i.e. wter nd methnol) ws controlled y the isocrtic pump. The gs mixture nd the liquid solution were simultneously sent into the spirl copper tue in co-current pttern where the flow rtes of the feed gs nd the feed liquid were djusted in ccordnce with the operting conditions. Before entering the qurtz tue, the liquid solution ws vporized nd mixed 9 CO nd CO 8 7 CO Concentrtion (%) CO O/C=, CO O/C=.15, CO O/C=.5, CO O/C=.5, CO O/C=, CO O/C=.15, CO O/C=.5, CO O/C=.5, CO H Concentrtion (%) O/C= O/C=.15 O/C=.5 O/C= Fig. 6 e Temporl distriutions of supplied energy t vrious O/C rtios under the operting tempertures of () 5 nd () C (S/C [ 1.5). Fig. 7 e Temporl gseous concentrtion distriutions of () CO nd CO nd () H under the operting conditions of C nd S/C [ 1.5.

7 4 interntionl journl of hydrogen energy 6 (11) 97e48 with the feed gs. After the rectnts flew into the qurtz tue, the mixing ws enhnced in the glss ed lyer. Then, ATR under the impct of the ctlyst ed developed in the ctlyst ed. The temperture in the ctlyst ed nd the supplied power were detected nd recorded t frequency of 1 Hz. To void dmging the sensors instlled in the gs nlyzer, the product gs pst through the condenser nd the drier sequentilly to preliminrily nd completely remove the moisture. The volumetric concentrtions of CO nd CO were detected y the GA t frequency of 1 min 1, wheres the concentrtion of H ws mesured once y the GC per min. CH 4 hs lso een detected y the GA ut ws not found in the product gs. Prior to the experiments, the GA nd the GC were clirted to ensure the experimentl qulity.. Results nd discussion nd.5, under the operting tempertures of 5 nd C re demonstrted in Fig. 4 nd, respectively. As whole, the temperture jump in the initil period of rectnt feeding is lwys oserved, regrdless of wht the O/C rtio nd the operting temperture re. The higher the O/C rtio, the higher the temperture jump, especilly for the cse of O/C ¼.5. On the other hnd, it cn e seen tht, s the O/C rtio increses, the period of temperture oscilltion hs trend to e elongted, nd it is prticulrly pronounced t O/C ¼.5. Furthermore, the temporl distriutions of supplied power t the operting tempertures of 5 nd C nd the four O/C rtios re presented in Fig. 5. Thermodynmiclly, incresing O/C rtio fcilittes the oxidtion rection of methnol; this leds to more het relesed from the chemicl rections. As result, the period of supplied power increses with incresing O/C rtio, s shown in Fig. 5. Once the O/C rtio is s high s.5, the exothermic rection ecomes so significnt In the study, three importnt prmeters ffecting the performnce of ATR of methnol re tken into ccount; they re the rection temperture, the molr rtio etween O nd methnol (i.e. the O/C rtio) nd the molr rtio etween stem nd methnol (i.e. the S/C rtio). The rection temperture, O/C rtio nd S/C rtio re in the rnges of 5e C, e1 nd 1e, respectively. Menwhile, to provide sis for the experiments, the residence time of the rectnts in the ctlyst ed is fixed t.5 s (viz. gs hourly spce velocity, GHSV ¼ 7, h 1 ) nd the flow rte of the feed liquid, the mixture of methnol nd wter, is fixed t.4 cc min 1 (5 C). To trigger ATR of methnol, Cu-Zn-sed ctlyst (Sud- Chemie MDC-) is employed. Detils of the properties of the ctlyst ed nd the operting conditions re listed in Tle 1. Temperture ( C) C S/C=1 S/C=1.5 S/C=.1. Therml ehvior of ATR of methnol strt feeding With the condition of S/C ¼ 1.5, the therml ehvior nd rection chrcteristics of the ATR of methnol t four O/C rtios of,.15,.5 nd.5 re first tken into ccount. Detiled flow rtes of ir nd N t vrious rection tempertures nd O/C rtios re listed in Tle. It should e pointed out tht the cse of O/C ¼ corresponds to the rection of MSR. Fig. displys the distriutions of supplied energy nd power into the rector t the conditions of O/C ¼.15, S/C ¼ 1.5 nd 5 C (operting temperture), wheres the temperture in the ctlyst ed is plotted in Fig.. It pproximtely tkes min for the rector to rech the temperture of 5 C. Then the rectnts re sent into the rector to elicit the ATR of methnol. It is noteworthy tht soon fter the rectnts re fed into the rector, there is notle jump in the temperture. This my e ttriuted to the sudden expnsion of the rectnt volume which cuses the liertion of het contined inside the ctlyst ed. Afterwrd, in view of the rection temperture eing higher thn the operting temperture (5 C), no power is supplied. Once the rection temperture rises to mximum vlue t min, it turns to decy. When the time is s long s 5 min, the rection temperture is lower thn 5 C nd, therefore, the power is supplied gin. Throughout the entire experimentl process, periodicl oscilltion in rection temperture is exhiited. The distriutions of rection temperture t the four O/C rtios, nmely, O/C ¼,.15,.5 Temperture ( C) C 5 4 strt feeding S/C=1 S/C=1.5 S/C= Fig. 8 e Temporl distriutions of rection temperture under vrious S/C rtios t the operting tempertures of () 5 nd () C (O/C [.5).

8 interntionl journl of hydrogen energy 6 (11) 97e48 4 tht only one pek of supplied power is exhiited (Fig. 5d nd h). Alterntively, Fig. 5 lso depicts tht the frequency of the oscilltion is somewht enlrged when the operting temperture is lifted from 5 to C, resulting from keeping higher temperture environment... Endothermic nd exothermic rections s well s gs concentrtion It hs een known tht MSR is n endothermic rection in nture, wheres ATR of methnol pertins to n exothermic rection if the O/C rtio is high to certin extent. In order to recognize the endothermic nd exothermic rections for methnol in the rector, temporl distriutions of supplied energy from the rector t vrious O/C rtios re presented in Fig. 6. Moreover, pure nitrogen with the residence time of.5 s in the ctlyst ed is lso included in the figure for comprison. In fct, the cse of trnsporting N into the rector cn e thought of s therml neutrl condition in tht no chemicl rection occurs in the rector. For oth the operting tempertures of 5 nd C, it is not surprising tht the energy consumption of MSR (i.e. O/C ¼ ) is higher thn tht of N. Fig. 9 e Temporl distriutions of supplied power t 5 C with S/C[ () 1, () 1.5 nd (c) nd t C with S/C[ (d) 1, (e) 1.5 nd (f) (S/C [ 1.5).

9 44 interntionl journl of hydrogen energy 6 (11) 97e48 Fig. 6 depicts tht the rection of methnol is close to therml neutrl condition s the operting temperture, O/C rtio nd S/C rtio re 5 C,.15 nd 1.5, respectively. When the O/C rtio is.5, the curve of supplied energy is elow tht of N, clerly reveling tht the rection of methnol is chrcterized y n exothermic rection. With the condition of O/C ¼.5, the curve further moves downwrd. This suggests tht the condition of O/C ¼.5 yields strongly exothermic rection. With ttention shifted to the operting temperture of C, Fig. 6 indictes tht the curve t O/C ¼.15 is lower thn tht of N. Moreover, the differences etween the curve of N nd the curves of O/C ¼.5 nd.5 in Fig. 6 re more significnt thn those in Fig. 6. It follows tht higher operting temperture will intensify the exothermic rection of ATR of methnol. Bsed on the ove oservtions, it is known tht, within the current opertions, when the O/C rtio is no less thn.15, ATR of methnol is fetured y n exothermic rection. Fig. 7 shows the temporl concentrtion distriutions of CO, CO nd H. Fig. 7 depicts tht the concentrtion of CO is y fr higher thn tht of CO, reveling tht the current opertions fvor CO formtion. This lso implies tht Eq. (1) nd () re fesile to elucidte MSR nd ATR without considering the formtion of CO. With regrd to H, Fig. 7 indictes tht the higher the O/C rtio, the lower the H concentrtion, s consequence of more H O generted. Once the O/C rtio is s high s.5, the concentrtion of H tes mrkedly. In consequence, from the viewpoint of hydrogen production nd utotherml rection, it is relized tht the condition of O/C ¼.15 or.5 is recommended opertion... Effect of vried S/C rtio The effect of ltered S/C rtio on MSR nd ATR is exmined in Figs. 8e11 where the O/C rtio is fixed t.5. Three S/C 1 C O nd CO 9 8 CO Concentrtion (%) CO S/C=1, CO S/C=1.5, CO S/C=, CO S/C=1, CO S/C=1.5, CO S/C=, CO H 18 Concentrtion (%) S/C=1 S/C=1.5 S/C= Fig. 1 e Temporl distriutions of supplied energy t vrious S/C rtios under the operting tempertures of () 5 nd () C (O/C [.5). Fig. 11 e Temporl gseous concentrtion distriutions of () CO nd CO nd () H under the operting conditions of C nd O/C [.5.

10 interntionl journl of hydrogen energy 6 (11) 97e48 45 Tle e Flow rtes of wter, methnol, ir nd N in the feed strem t vrious operting tempertures nd S/C rtios (O/C [.5). Temperture ( C) S/C rtio (e) Flow rte of wter (cc min 1,5 C) Flow rte of methnol (cc min 1,5 C) Flow rte of ir (cc min 1,5 C) Flow rte of N (cc min 1,5 C) S/C=1.5 rtios of 1, 1.5 nd re tken into considertion nd the flow rtes of ir nd N t vrious S/C rtios re tulted in Tle. As seen in Fig. 8, there is descent in the period of temperture oscilltion s the S/C rtio increses. In ddition, it cn e found tht the period t S/C ¼ 1 is lrger thn those t S/C ¼ 1.5 nd to certin extent. Upon inspection of the temporl distriutions of supplied power, Fig. 9 reflects tht the period of power oscilltion is lso ffected y the operting temperture to certin extent. Specificlly, t ny given S/C rtio one more pek in the oscilltion is rendered t C compred to tht t 5 C. To proceed frther into n nlysis of energy supply in the course of rection, Fig. 1 illustrtes tht, with the operting temperture of 5 C, ATR with S/C ¼ 1 sustntilly consumes less energy in contrst to those of S/C ¼ 1.5 nd. Similr to the oservtions in Fig. 6, compring Fig. 1 to suggests tht higher operting temperture will enhnce the difference etween the curve of therml neutrl condition (i.e. N ) nd the curves of vrious S/C rtios. On the other hnd, the concentrtion distriutions of CO, CO nd H shown in Fig. 11 revel tht incresing S/C rtio disdvntges the formtion of CO. This.5 5 C C.5 5 C Frequency (h -1 ) O/C O/C=.5.5 H yield (H mol / CH OH mol) Experiment Themodynmics Expertment/Themodynmics O/C C H yield (%) Frequency (h -1 ) C C H yield (H mol / CH OH mol) Experiment Themodynmics Expertment/Themodynmics H yield (%) S/C Fig. 1 e Profiles of frequency of supplied power versus () O/C rtio t S/C [ 1.5 nd () S/C rtio t O/C [ O/C Fig. 1 e Profiles of H yields versus O/C rtio t operting tempertures of () 5 nd () C (S/C [ 1.5).

11 46 interntionl journl of hydrogen energy 6 (11) 97e48 rises from the fct tht higher S/C rtio mens tht more het will e sored y stem, therey lessening the formtion of CO..4. Performnces of MSR nd ATR According to the ove oservtions of therml ehvior of MSR nd ATR, the profiles of frequency of supplied power with respect to the O/C rtio nd the S/C rtio re sketched in Fig. 1 nd, respectively. The frequency is mesured from the onset of rectnt feeding to the experimentl time of 15 min nd its unit is the reciprocl of hour (i.e. h 1 ). As whole, t S/C ¼ 1.5 the frequency hs trend to decrese with incresing O/C rtio (Fig. 1). Once the O/C rtio is s high s.5, much het is lierted from ATR so tht the frequency decys in significnt wy. It is lso noted tht higher operting temperture cuses higher frequency, resulting from more energy supplied to keep the temperture. In regrd to the influence of S/C rtio, with the condition of O/ C ¼.5 the frequency t S/C ¼ 1 is reltively lower thn those t S/C ¼ 1.5 nd (Fig. 1). As whole, the frequency is in the rnge of 1.5e.5 h 1. Susequently, the H yields t the conditions of S/C ¼ 1.5 nd O/C ¼.5 re profiled in Figs. 1 nd 14, respectively, where two different yields re presented. In Fig. 1, the experiments or thermodynmic predictions t S/C ¼ 1.5 suggest tht H production from the consumption of per mol methnol decreses s the O/C rtio rises. However, when the experimentl results re compred to the thermodynmic predictions, it is worthy of note tht the H yield pproches % t the operting temperture of C nd the O/C rtio of.5. Considering the condition of O/C ¼.5, Fig. 14 depicts tht, sed on the consumption of per mol methnol, incresing S/C rtio pushes the H yield up it. Moreover, the H yield is lwys lrger thn 91% nd the vlues t C (Fig. 14) re much higher thn those t 5 C(Fig. 14). In other words, higher temperture significntly enhnces the formtion of H from ATR of methnol. S/C=1.5 H yield (H mol / CH OH mol) C Experiment Thermodynmics Experiment/Thermodynmics H yield (%) CH OH conversion (%) C C O/C S/C O/C=.5 C H yield (H mol / CH OH mol) Experiment Thermodynmics Experiment/Thermodynmics H yield (%) CH OH conversion (%) C C S/C S/C Fig. 14 e Profiles of H yields versus S/C rtio t operting tempertures of () 5 nd () C (O/C [.5). Fig. 15 e Profiles of methnol conversion versus () O/C rtio t S/C [ 1.5 nd () S/C rtio t O/C [.5.

12 interntionl journl of hydrogen energy 6 (11) 97e48 47 Tle 4 e Summry of operting conditions nd comprison of performnce of methnol ATR. Ctlyst S/C O/C Temperture ( C) GHSV (h 1 ) H yield (%) CH OH conversion (%) Reference CuO/MnO e e 59e6 8e98 [5] Cu/ZnO e95 6 e 8e95 [] ZnOeCr O /CeO ezro 1e1.5.1e.7 5e54 e5 e 7e96 [1] ZnOeZnCr 4 /CeO ezro 1e.5e. 47e57 75e9, e 54e [9] Cu/ZnO/Al O e4 6, e e [15] ZneCreCu e4 e 4e [14] ZnOeCrO /CeO ezro /Al O 1.e.e. 8e4 e1, e 84e [4] CuO/ZnO/Al O 1e e.5 5e 7, 78e 97e This study Eventully, the profiles of methnol conversion t vrious operting conditions re provided in Fig. 15. It is pprent to find tht the conversion is lrger thn or equl to 97% within the investigted rnges of operting tempertures (5 nd C), O/C (e.5) rtio nd S/C rtio (1e). To recognize the performnce of methnol conversion from ATR of methnol under the influence of spirl preheting, the otined results in this study re compred with other studies nd detiled comprisons re summrized in Tle 4. As shown in the tle, the dopted GHSV (7, h 1 ) in this study is higher thn others; however, the otined methnol conversion (97e%) is high thn others. It is thus concluded tht the spirl preheting on the rectnts cn enhnce the performnce of ATR of methnol mrkedly. 5. From the viewpoint of hydrogen production nd utotherml rection, the condition of O/C ¼.15 or.5 long with S/C ¼ 1 is recommended opertion for hydrogen production from ATR of methnol. Acknowledgments The uthors grtefully cknowledge the finncil support of the Ntionl Science Council, Tiwn, ROC, on this study. references 4. Conclusions Methnol stem reforming (MSR) nd utotherml reforming (STR) with the ids of Cu-Zn-sed ctlyst nd spirl preheting hs een investigted. The effects of three importnt prmeters of operting temperture (5 nd C), O/C rtio (e.5) nd S/C rtio (1e) on therml ehvior nd performnce of hydrogen production hve een nlyzed where the gs hourly spce velocity (GHSV) is fixed t 7, h 1. By monitoring supplied power into the rector nd mesuring gseous concentrtions in the product gs, numer of concluding remrks re drwn elow. 1. With the investigted rnges of operting temperture nd S/C rtio, when the O/C rtio is lrger thn or equl to.15, ATR of methnol is fetured y n endothermic rection. The exothermic ehvior is prticulr significnt s the O/C rtio increses from.5 to.5.. A higher operting temperture tends to distinguish the exothermic chrcteristic of ATR of methnol from therml neutrl condition.. Incresing O/C rtio nd S/C rtio reduces the concentrtion of H in the product gs; however, in ll the tested cses the concentrtion of CO in the product gs is quite low compred to tht of CO. 4. On ccount of the utiliztion of spirl preheting on the rectnts, the methnol conversion nd hydrogen yield in this study re lwys higher thn 95 nd 9%, respectively. A comprison suggests tht the methnol conversion from ATR of methnol with spirl preheting is superior to those of other studies. [1] Bll M, Wietschel M. The future of hydrogen e opportunities nd chllenges. Interntionl Journl of Hydrogen Energy 9;4:615e7. [] Lemus RG, Durt JMM. Updted hydrogen production costs nd prities for conventionl nd renewle technologies. Interntionl Journl of Hydrogen Energy 1;5:99e6. [] Levin DB, Chhine R. Chllenges for renewle hydrogen production from iomss. Interntionl Journl of Hydrogen Energy 1;5:496e9. [4] Zhng H, Lin G, Chen J. Evlution nd clcultion on the efficiency of wter electrolysis system for hydrogen production. Interntionl Journl of Hydrogen Energy 1; 5:1851e8. [5] Chen WH, Chiu IH. Trnsient dynmic of hydrogen permetion through plldium memrne. Interntionl Journl of Hydrogen Energy 9;4:44e8. [6] Chen WH, Jheng JG. Chrcteriztion of wter gs shift rection in ssocition with cron dioxide sequestrtion. Journl of Power Sources 7;17:68e75. [7] Ross DK. Hydrogen storge: the mjor technologicl rrier to the development of hydrogen fuel cell crs. Vcuum 6; 8:184e9. [8] Ardhl CL, Rsst SD. Overview of systems considertions for on-ord chemicl hydrogen storge. Interntionl Journl of Hydrogen Energy 9;4:6676e8. [9] Liu N, Yn Z, Wng S, Zhng C, Wng S, Li D. Chrcteriztion nd performnce of ZnO-ZnCr O 4 /CeO - ZrO monolithic ctlyst for methnol uto-therml reforming process. Interntionl Journl of Hydrogen Energy 8;:164e51. [1] Chen WH, Lin BJ. Effect of microwve doule sorption on hydrogen genertion from methnol stem reforming. Interntionl Journl of Hydrogen Energy 1;5:1987e97. [11] Chn SH, Wng HM. Thermodynmic nd kinetic modeling of n utotherml methnol reforming. Journl of Power Sources 4;16:8e15.

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