I n d . E n g . Chem. Res. 1993, 32, 1-10
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KINETICS, CATALYSIS, AND REACTION ENGINEERING Improved Steam Gasification of Lignocellulosic Residues in a Fluidized Bed with Commercial Steam Reforming Catalysts Maria P. Aznar, Jos6 Corella,*?+ Jestis Delgado,t and Joaquin Lahoz Department
of
Chemical Engineering, University of Zaragoza, 50009 Zaragoza, Spain
The improved/ two-stage steam gasification of biomass or lignocellulosic residues in fluidized bed with steam reforming catalysts placed in a downstream secondary reactor has been studied. Two commercial catalysts, R-67 and RKS-1 from Topme, were used a t their incipient fluidization conditions. At 720-760 "C and space-times of only 0.10-0.20 s, with catalyst sizes under 1.0 mm and with steam/biomass ratios of 1.2-1.6, tar conversions of 99.95% were achieved in the catalytic reactor. In this process, tar and methane in the flue gas can be easily lowered below 5 mg/m3(NTP) and 0.5 vol % ,respectively, without using oxygen. The catalyst deactivation by coke from the tar cracking is the main problem of this process.
Introduction Steam gasification in fluidized beds of coals, biomass, and/or lignocellulosic or carbonaceous residues is a wellknown process for producing a valuable gas. I t can also be applied to several organic wastes like RDF or MSW for their elimination. It is an endothermic process in which oxygen is sometimes added to the gasifying gas to make the process autothermal. As oxygen is expensive and the heating value of the exit gas diminishes when oxygen is used, oxygen should thus be avoided in steam gasifiers. This can be accomplished in some processes such as the multisolid circulating fluid bed one of Battelle-Columbus (OH) or burning some of the gas produced inside the gasifier bed. The product (gas, char, tar, water-soluble organics) distribution and the gas composition (H2,CO, C02,CHI, C2,C3, ...) at the gasifier exit depend on a lot of variables such as the temperature of the gasifier bed (T,) and of the gasifier freeboard (Tf),the steam/carbonaceous residue fed ratio, the space-time in the gasifier bed (71) and in the freeboard (7f), the type, origin, moisture, ash content and particle diameter of the biomass, coal, or waste fed, the location of the feeding point to the gasifier, etc. The detailed effects of the several gasification variables can be seen in previous works of these authors (Corella et al., 1991; Herguido et al., 1992; ...) and in many books from the US and EC congresses on biomass/coal processing (e.g., Van den Aarsen et al. (1982), Anta1 (1985), Bridgwater and Kuester (1988), and Grassi et al. (1992)). Steam gasification of lignocellulosic residues and/or of biomass in fluidized beds without catalysts was extensively studied by us in previous works (Corella et al., 1988,1991; Herguido et al. (1992). With operation in 'good" gasification conditions (T,= 750-780 "C,Tf = 750-780 "C, TfilterEhambr = 500-500 "C, steam/biomass ratio = 1.0, 7 1 = 1.0 s, ...) a typical exit gas composition is 55 vol % HP, Present address: Department of Chemical Engineering, University Complutense of Madrid, 28040 Madrid, Spain. : Present address: Repsol Petrbleo, S A . Research Department, Madrid, Spain. +
20-25 V O ~o?' CO, 16-20% COZ, 4-8% CH4, 1-2070 Cp, 1-2% C3,and tars. Tar yields depend on the gasification process and temperature of the downstream vessels, ranging from 35 to 195 g/m3(NTP) (Corella et al., 1988, 1989, 1991; Herguido et al., 1992). The gas from the gasifier exit has thus a medium-heating value (10-14 MJ/m3(NTP)),and it can be burnt for obtaining steam, electricity, ... Its composition is nevertheless far from the optimum one. For instance, CHI is a poison when this gas is envisaged to be used as synthesis gas and it must be lowered below 0.5 vol %. Tar must be also eliminated for many and well-known reasons. Extensive research using catalysts has been made at the University of Zaragoza (Spain) to improve the steam gasification of biomass/cellulosic residues in a fluidized bed and to make it competitive. Two very different gasification processes have been developed: a multisolid circulating fluid bed gasification (MSCFBG) process, like the Battelle-Columbusone, and a two-stage/catalytic gasification. This paper was concern only the latter one. The first questions were the best location to place the catalyst and which type is to be used. After some years of experimentation we are now in the same way that the PNL of Battelle-Richland (WA) was when it stopped this research a few years ago. Besides using dolomites and/or limestones (tarcracking catalysts) in the same gasifier bed, we think that a second re-forming catalyst has to be placed in a secondary/catalytic/downstreamreactor. This location allows the second bed to be operated at different conditions (temperature, state of the bed, space-time, etc.) from the gasifier ones. Therefore, in this work we are going to show results from when the catalyst is placed only in this secondary reactor, having a two-stage (for the gas)/ catalytic gasification process. In other previous and also simultaneous works we have studied (1)the use of solids like dolomites/limestones/ magnesites to crack the tars present in the gas at the gasifier exit (Aznar et al., 1989b, 1991b); (2) the methanation of the exit gas (Corella et al., 1990), which did not give good enough results; and (3) the steam reforming of the methane in the exit gas (Aznar et al., 1990,1992~).Aa the use of the reforming catalysts gave good results, we
0888-588519312632-0001$04.00/0 0 1993 American Chemical Society
2 Ind. Eng. Chem. Res., Vol. 32, No. 1, 1993
continued this research. Thus, we are going to show the results obtained when commercial steam reforming catalysts are used in a downsteam or secondary catalytic reactor to eliminate not only the methane but also the C2, C3,and tars existing in the raw gas from the gasifier exit. Steam Reforming of Methane. The steam reforming of methane A H 2 9 8 = 206.1 kJ/mol CH, + H 2 0 * CO + 3H2 (1) is a well-known process carried out always in fixed bed reactors (i.e. Rostrup-Nielsen, 1984a,b) under severe diffusional limitations in the catalyst particles, with effectivness factors ( q ) in the order of 0.01-0.001. The commercial catalyst particles are bigger than 5 mm and quite soft which makes it necessary to use them in a fixed bed, though advantages of using fluidized beds for this process have been clearly identified (Elnashaie and Adris, 1989; Laguerie et al., 1991). Together with eq 1 other reactions also have to be considered, such as AHz9,= 165 kJ/mol CH, + 2H20 * CO, + 4H2 (2) CH,
+ CO, * 2CQ + 2H2
AH,,,=
247-255 kJ/mol (3)
CQ
+ H 2 0+ CO + H2
AHzg8= -41.5 kJ/mol
(4)
A t the inlet of our second bed or “reformer” there is about 20 vol % COz. Since above 913 K eq 3 is thermodynamically favored (Gadalla and Bower, 1988; Gadalla and Sommer, 1989), such reaction can also occur in this second bed. The kinetics of the steam reforming of methane and of these simultaneous reactions have been studied with many catalysts by different authors like Munster and Grabke (1981),Agnelli et al(1987), Numaguchi and Kikuchi (1988), Xu and Froment (1989a,b),Elnashaie et al. (1990), etc. It is also known that the steam reforming (Ni) catalysts here used can be simultaneously deactivated by coke, by some sulfur existing in the flue gas, and by [Ni(CO),J fopation (Corella and Monz6n, 1988). It is also known that the ash and char coming from the biomass/coal gasification have some catalytic activity of the steam reforming of methane and for the water-gas shift reactions (e.g., Chen et al. (1987) and Boronson (1989)). Previous Use of Nickel Steam Reforming Catalysts in the Steam Gasification of Biomass in Fluidized Beds. The first authors, to our knowledge, in using steam methane reforming catalysts were Tanaka et al. (1984) and Yamaguchi et al. (1986). Their interesting work with a 20 wt % Ni/A1203 catalyst had nevertheless for us several limitations: (1)they placed the catalyst in the same gasifier bed; (2) the gasification agent was not 100% steam but 13.7-45.0 vol % steam in argon; (3) the sawdust feed rate, the gasifier diameter, and the catalyst weight were too low, 0.1-0.2 g/min, 25-mm i.d., and 5-10 g, respectively; and (4) their gasification temperature when using the catalyst was not optimum (they gasified a t 600-750 OC, mainly at 700 “C). Although they found some interesting things like the activation-deactivation of the nickel catalyst during its use, their results can be clearly improved. For instance, they obtained methane yields at their catalytic gasifier exit of 2.8 vol % (too high) and COD values in the condensates of 20000 mg/L (too high, too). A similar thing can be said of the pioneering work of Rei et al. (1986, 1987). Much more important for this process has been the latest work made at the PNL of Richland, WA (Baker et
al., 1987; Baker and Mudge, 1984, 1987; Mudge et al., 1988). They used several commercial steam reforming catalysts placed in a secondary bed, after a heated porous metallic filter, downstream from the fluid bed gasifier. The equipment they used (Baker et al., 1987; Mudge et al., 1988) is nearly the same as that simultaneously developed at the University of Zaragoza (Corella et al., 1989, 1991). They found very good results: gas yields of 1.8 and 2.1 L(NTP)/(g daf), at steam/biomass ratios of 0.5 and 1.2, respectively, TQC values in the condensates of 250-3450 mg/L, catalyst lifes up to 34 h, but also CH, contents in the exit gas of 3.49 vol % (too high). They generated then a new and interesting two-stage process for biomass gasification. They also added air (air/wood ratio of 0.4) to the secondary bed to prevent coke formation and catalyst deactivation. Baker et al. (1987) also indicated that when the catalyst was fluidized, much better results, a longer catalyst life, were obtained. The U ~ , ~ / ratio U , ~ is thus a very important parameter. To know it, Delgado et al. (1991) have calculated the minimum fluidization velocity (umf)of these steam reforming catalysts with the gas coming from the gasifier at the temperatures of the second catalytic reactor. This parameter ( U ~ , ~ / U ,will ~ ) be thus known in this work. In this paper we are going to continue the work made by the PNL and to improve their results if possible. All our results should have to be related and compared with those previously found at the PNL. Very recently, in the “Thermochemical Biomass Conference” held in Interlaken (Switzerland) in May 1992, some Finnish people have presented excellent results using reforming catalysts after the biomass gasifier but without indicating the catalyst used, lacking thus those results for necessary checking possibilities.
Experimental Section Equipment. The installation used (Figure 1) is the same as that previously described by Corella et al. (1990, 1991). This process is basically a fluidized bed gasifier, a high-temperature filter, and a catalytic reactor. The gasification zone has a 6.0-cm inner diameter and 30-cm height, and it is externally heated. It is followed by another and upper zone (first conical and afterward cylindrical of 14-cm i.d. and 20-cm height). This gasifier freeboard is also externally heated and its temperature measured. The gas distributor plate of the fluid bed gasifier was made of bubble cups and was periodically cleaned in both ways, mechanically and chemically. The biomass or cellulosic residue was continuously fed by the upper part of the gasifier to the gasifier bed top. The most common biomass flow rate was 7-8 g/min (0.42 kg/h). The screwfeeder had a 3.5-cm diameter with a 2 / 3 HP engine. The downcomer pipe is 2.7 cm was continuously and externally refrigerated by five air quench flows to avoid biomass pyrolysis in it, with subsequent pipe plugging. The biomass hopper had 5-h operation capacity. Its walls had a 80° slope, and it was continuously knocked. The correct, continuous- and stationary-state feeding of the cellulosic residue at this low flow rate was perhaps the hardest and most difficult part of the experimentation. The filter chamber had a porous metallic filter of 10-pm nominal pore diameter; it was operated at about 550 “C. For the catalytic reactor we had two different vessels of 4.0- and 6.0-cm inner diameter (15- and 25-cm height, respectively) followed by a disengaging zone of 8.0- or 12.0-cm inner diameter, respectively, and 15-cm height. This diameter change allowed us to change and then U ~ , ~ / UTherefore, , ~ for a given catalyst particle size we were able to change the state of this second bed from fixed to fluidized. The temperature of this second bed, T2,was
Ind. Eng. Chem. Res., Vol. 32, No. 1, 1993 3 1. Gasifier 2. Metallic filter 3. Catalytic bed 4. Waste feeder 5 . Water pump 6. Condenser 7. Gas filter 8. Flowmeter 9. Gas sampling 10. Condensate
Air
+
Gas
Figure 1. Installation used.
always measured in its axis. The gasifying agent or fluidizing gas in the first bed (gasifier) was always steam. The pressure was atmospheric. In the gasifier bed there was always silica sand previously calcined (at 80 "C, 1 h) of -200 + 125 Fm. Pine (Pinus pinaster) sawdust has been the only cellulosic residue used in the experimentation shown in this paper. The main characteristics of this sawdust were as follows: size, -630 + 200 pm; moisture content, 8.5-11.5 wt % (oven at 105 "C); volatile matter, 74-76% dry weight; fixed carbon, 12-1370 dry weight; ash content, 0.5-1.2% dry weight (oven at 800 "C); LHV,18.0-18.4 MJ/(kg daf); C, 41-45 wt %; H, 6.3-6.7 wt %; 0,49-53 wt %; N, 0.2-0.3 wt %. The size of the sawdust was important. The above indicated size was selected to obtain a good mixture of its char with the silica sand in the bed, according to the segregation studies in these mixtures of Aznar et al. (1989a). The hydrodynamic behavior in the fluidization of biomass and wastes had also been previously and extensively studied (Aznar et al., 1992a,b). For the sizes of the sand and sawdust used here, the umfand uCfof a 20 w t 90 char-sand mixture were 5.0 and 9.2 cm/s, respectively. The superficial gas (steam) velocity at the gasifier inlet, u ~ was , ~ ,always between 15.0 and 21.0 cm/s. This steam flow rate made the steam/sawdust ratio to be around 1.0. Analysis. During each run, samples of the exit gas and of condensates were periodically (every 10-30 min) taken. That is to say, six to eight samples of exit gas and of condensates, at least, were taken in each run. They were analyzed by gas chromatography (HP 5790A) to determine the gas composition and by a TOC (total organic carbon) analyzed (Dohrmann DC-90) to know the tar/hydrocarbons formed in this process and catalyst. This number allows one to know the tar/hydrocarbon conversion (by cracking and reforming) in the catalytic reactor. In this paper we will define "tars" to be the sum of the soluble
and nonsoluble-in-water tars. With methane steam reforming catalysts the nonsoluble tar is only a small fraction of the overall tar. When a high (>98% tar conversion is achieved, all the tars formed are water soluble and they are present thus in the aqueous (condensate) phase. At the end of each run, the carbonaceous residues, that we will call chars, were carefully collected from several parts/vessels of the installation. Five at least, different carbonaceous residues can be distinguished: (i) in the gasifier bed (which usually is the 90% of the overall char, (ii) in the gasifier freeboard, stuck on the walls, (iii) in the filter chamber, dragged from the gasifier bed, (iv) on the filter surface, coming from the thermal tar cracking, and (v) in the catalyst surface (coke). The measure of the amounts of these carbonaceous residues was very timeconsuming, but it allowed us to know if the run had been "good" (with correct gasification) or had been a bad operation. High char yields in the gasser bed in its freeboard were an indication that the biomass gasification had been incorrect. In this case, in these runs, more tar is produced which affects the catalytic bed activity and life. Catalyst Used. Commercial catalysts for steam reforming of methane have been used: the Topme R-67-7H one has been the most used catalyst. It has 12-14 w t % Ni (16-18% NiO) on a Mg/A120, support, with free Mg of less than 0.5 wt % and Si02 >, 3) ~ is not possible with the actual commercial steam re-forming catalysts because they are soft (they are being designed for their use in a fixed bed), they erode easily in the fluidized bed, and a lot of fine particles (with their subsequent carry over the bed) are produced. (iv) A guard bed should be installed after the gasifier and before the catalytic bed. A bed of dolomite or even limestone, could crack there tars in the flue gas preventing them from arriving at the catalytic bed, thereby deactivating it. This new bed would produce a three-stage process, a little more complicated and expensive than the two-stage one but with a lot of possibilities for gasifying many types of solid residues and wastes. Acknowledgment This work was made under a shared contract with the
EC, DGXII, "Non-Nuclear Energy Programme", Project No. EN 3B/0103/E, and the DGICYT (Madrid) Projects No. PB88-0391 and PB91-0375. Nomenclature COD = chemical oxygen demand daf = dry, ash-free d = particle size, mm = height of the gasifier bed at t = 0, cm Ho,2= height of the catalytic/reforming bed at t = 0, cm Ktheor= equilibrium constant Kerp= ratio of the partial pressures of the products to the partial pressures of the reactants, according to the reaction stoichiometry, at the exit of the second bed
LHV = low heating value of the gas, MJ/m3(NTP) MSW = municipal solid waste Q = gas flow rate, L(NTP)/min RbF = refuse derived fuel t = time-on-stream of the catalyst, min T I = temperature of the gasifier, "C T2 = temperature of the secondary/catalytic reactor, "C Tf= temperature in the freeboard of the gasifier, OC TOC = total organic carbon = gas superficial velocity at the inlet of the gasifier, cm/s u2,0= gas superficialvelocity at the inlet of the catalytic bed, cm/s u2,s= gas superficial velocity at the exit of the catalytic bed, cm/s uc,f= minimum gas velocity at which all the bed is entirely fluidized, cm/s umf= minimum gas fluidization velocity, at reactor temperature, for the catalyst,with the gas coming from the gasifier, cm/s YG = gas yield m3(NTP)/(kg daf)
Greek Symbols & = inner diameter of the catalytic bed, mm rl = space-time of the gasifier bed, defined by Ho,l/u,,o,s i2 = space-time of the catalytic reactor, defined by Ho,2/u2,s, S
= space-time of the catalytic reactor, defined by (kg of catalyst-h)/(kg of biomass fed daf), kgh/kg Tf = space-time of the gasifier freeboard, s i2'
Literature Cited Agnelli, M. E.; Ponzi, E. N.; Yeramian, A. A. Catalytic deactivation of methane steam reforming catalysts. 2. Kinetic study. Ind. Eng. Chem. Res. 1987,26,1704-1707. Antal, M. J. In Fundamentals of thermochemical biomass conuersion; Overend, R. P., Milne, T. A., Mudge, L. K., Eds.; Elsevier Applied Science: London, 1985; pp 511-537. Aznar, M. P.; Gracia-Gorria, J. A.; Corella, J. Segregation in the fluidization of mixtures of wastes with silica sand. An. Quim. (Madrid) 1989a,85,100-108. Aznar, M. P.; Delgado, J.; Corella, J.; Lahoz, J. Steam gasification of biomass in fluidized bed with a secondary catalytic bed - 11: Tar cracking with dolomite(s) in the secondary reactor. In Pyrolysis and Gasification; Ferrero, Maniatis, Buekens, Bridgwater, Eds.; Elsevier Applied Science: London, 1989b, pp 629434. Aznar, M. P.; Corella, J.; Delgado, J.; Lahoz, J. Steam gasification of biomass in fluidized bed with a secondary catalytic bed: 1V.Use of methane steam reforming catalysts. In Biomass for Energy and Industry, 5th EC Conference, Conversion and Utilization of Biomass; Grassi, do Santos, eds.; Elsevier Applied Science: London, 1990; Vol. 2, pp 2798-2803. Aznar, M. P.; Gracia-Gorria, F. A.; Corella, J. Minimum fluidization velocities of biomass-2nd solid mixtures. Int. Chem. Eng. 1992a, 32 (l),95-102. Aznar, M. P.; Gracia-Gorria, F. A,; Corella, J. Minimum fluidization velocities of biomass-2nd solid mixtures. Int. Chem. Eng. 1992b, 32 (2), 103-113. Aznar, M. P.; Delgado, J.; Corella, J.; Lahoz, J.; AraguBs, J. L. Two-stage steam gasification of biomass in fluidized bed with downstream methane and tar steam reforming. New resulta. In 6th EC Conference on Biomass for Energy, Industry and Environment, Athens, 1991; Elsevier Applied Science: London, in press, 1992c. Aznar, M. P.; Delgado, J.; Corella, J.; Aldea, E.; Martinez, M. P. Fuel and usefuel gas by steam gasification of biomass in fluidized bed followed by a tar cracking fluidized bed of dolomite/magnesite/ limestone. In 6th EC Conference on Biomass for Energy, Industry and Enuironment, Athens, 1991;Elsevier Applied London, in press, 1992d. Baker, E. G.; Mudge, L. K. Tar removal in a hot gas desulfuration process. J. Anal, A p p l . Pyrolysis 1984,6 , 285. Baker, E. G.; Mudge, L. K. Catalytic tar conversion in coal gasification systems. Ind. Eng. Chem. Res. 1987,26, 1390-1395. Baker, E. G.; Mudge, L. K.; Brown, M. D. Steam gasification of biomass with nickel secondary catalysts. Ind. Eng. Chem. Res. 1987,26,1335-1339.
10 Ind. Eng. Chem. Res., Vol. 32, No. 1, 1993 Bernardo, C. A,; Alstrup, I.; Rostrup-Nielsen, J. R. Carbon deposition and methane steam reforming on silica-supported Ni-Cu catalysts. J. Catal. 1985,96,517-534. Boronson, M. L.; Howard, J. B.; Longwell, J. P.; Peters, W. A. Heterogeneous cracking of wood pyrolysis tars over fresh wood char surfaces. Energy Fuels 1989,3,735-740. Bridgwater, A. V., Kuester, J. L., Eds. Research in Thermochemical Biomass Conuersion; Elsevier Applied Science: London, 1988. Chen, W. J.; Sheu, F. R.; Savage, R. L. Catalytic activity of coal ash on steam methane reforming and water-gas shift reactions. Fuel Process. Technol. 1987,16,279-288. Corella, J.; Monzbn, A. Modeling of the deactivation kinetics of solid catalyst by two or more simultaneous and different causes. Ind. Eng. Chem. Res. 1988,27,369-374. Corella, J.;Herguido, J.; Alday, F. L. Pyrolysis and steam gasification of biomass in fluidized. Influence of the type and location of the biomass feeding point. In Research in Thermochemical Biomass Conversion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: London, 1988; pp 384-398. Corella, J.; Aznar, M. P.; Cebriin, N.; Iglesias, J. I.; Martinez, M. P. Steam gasification of biomass in fluidized bed with a secondary catalytic reactor.-I. Results with the secondary reactor empty and with sand. In Pyrolysis and Gasification; Ferrero, Maniatis, Buekens, Bridgewater, Eds.; Elsevier Applied Science: London, ._ 1989; pp 624-628. Corella. J.: Aznar. M. P.: Martinez. M. P.: Ielesias. J. I. Steam easification of biomass in fluidized bed w’ithY a secondary catalytic bed: 111.-Useof methanation catalysts. In Biomass for Energy and Industry, 5th EC Conference, Vol 2, Conversion and Utilization of Biomass: Grassi, do Santos, Eds.; Elsevier Applied Science: London, 1990; 2749-2754. Corella, J.; Aznar, M. P.; Delgado, J.; Aldea, E. Steam gasification of cellulosic wastes in fluidized bed with downstream vessels. Ind. Eng. Chem. Res. 1991,30, 2252-2262. Delgado, J.; Corella, J.; Aznar, M. P.; AraguBs, J. L. umf at elevated temperatures with gas from steam fluid bed gasification of biomass/coal, for dolomite, silica sand and a steam reforming catalyst. In La Fluidization-Recents Progrds en Gdnie des Procidis; Laguerie, c.,Guigon, p., Eds.; Lavoisier: Paris, 1991; Vol. 5, No. 11, pp 62-69. Duprez, V.; Miloudi, A.; Delahay, G.; Maurel, R. Selective steam reforming of aromatic hydrocarbons. V.-Steam conversion and hydroconversion of selected monoalkyl- and dialkylbenzene on Pt and Ni catalysts. J . Catal. 1986,101,56-66. Elnashaie, S. S. E. H.; Adris, A. M. A fluidized bed steam reformer for methane. In Fluidization VI; Grace, J. R., Schemilt, L. W., Bergougnou, M. A,, eds.; American Institute of Chemical Engineers: New York, 1989; pp 319-326. Elnashaie, S. S. E. H.; Adris, A. M.; Al-Ubaid, A. S.; Soliman, M. A. On the non-monotonic behaviour of methane-steam reforming kinetics. Chem. Eng. Sci. 1990,45 (2), 491-501. Gadalla, A. M.; Bower, B. The role of catalyst support on the activity of nickel for reforming methane with CO,. Chem. Eng. Sci. 1988, 43 (ll),3049-3062. Gadalla, A. M.; Sommer, M. E. Carbon dioxide reforming of methane on nickel catalysts. Chem. Eng. Sci. 1989,44 (12), 2825-2829. Grassi, G., Collina, A., Zibetta, H., Eds.; Biomass for Energy, Industry and Environment; Elsevier Applied Science: London,
1992. Herguido, J.; Corella, J.; GonzBlez-Saiz, J. Steam gasification of lignocellulosic residues in fluidized bed a t small pilot-plant scale. Effect of the type of feedstock. Ind. Eng. Chem. Res. 1992,31, 1274-1282. Laguerie, C.; Hemati, M.; El Ghezal, L. Steam reforming of methane in fluidized bed. In La Fluidization. Recents Progrds en Genie des Procides; Laguerie, C., Guigon, P., Eds.; Lavoisier: Paris, 1991; Vol 5, No. 11, pp 12G126. Mudge, L. K.; Baker, E. G.; Brown, M. D.; Wilcox, W. A. Catalytic destruction of tars in biomass-derived gases. In Research in Thermochemical Biomass Conuersion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: London, 1988; pp 1141-1155. Munster, P.; Grabke, H. J. Kinetics of the steam reforming of methane with iron-nickel alloys as catalysts. J . Catal. 1981,72, 279-287. Numaguchi, T.; Kikuchi, K. Intrinsic kinetics and simulation in a complex reaction network: steam-methane reforming. Chem. Eng. Sci. 1988,43,2295-2301. Rei, M. H.; Lin, F. S.; Su, T. P. Catalytic gasification of rice hull. 2. The steam reforming reaction. Appl. Catal. 1986,26,27-35. Rei, M. H.; Lin, F. S.; Su, T. P. Catalytic gasification of rice hull. 3. The steam reforming of carbonaceous materials. Ind. Eng. Chem. Res. 1987,26,383-386. Ridler, D. E.; Twigg, M. V. Steam reforming. In Catalyst Handbook; Twigg, M. V., Ed.; Wolfe: London, 1989; Chapter 5, pp 244-248. Rostrup-Nielsen, J. R. Catalytic steam reforming. In Catalysis Science & Technology; Anderson, J. R., Boudart, M., Eds.; Springer-Verlag: Berlin, 1984a; Vol. 5, Chapter 1. Rostrup-Nielsen, J. R. Sulfur-passivated nickel catalyst for carbonfree steam reforming of methane. J . Catal. 1984b,85, 31-43. Sacco, A., Jr.; Geurts, W. A. H.; Jablonski, S. L.; Lee, S.; Gately, R. A. Carbon deposition and filament growth on Fe, Co, and Ni foils using CH,-H,-H,O-CO-CO, mixtures. J . Catal. 1989, 119, 322-341. Tanaka, Y.; Yamaguchi, T.; Yamasaki, K.; Ueno, A.; Kotera, Y. Catalyst for steam gasification of wood to methanol synthesis gas. Ind. Eng. Chem. Prod. Res. Dev. 1984,23,225-229. Van den Aarsen; Beenackers, Van Swaaij. Thermochemical gasification in a pilot plant fluidized bed wood gasifier. Energy from Biomass I I , Berlin, 1982; Commission of European Communities: Luxembourg, 1982; pp 425-429 Energy from Biomass I I , Berlin, 1982; Commission of European Communities: Luxembourg, 1982; pp 425-429. Yamaguchi, T.; Yamasaki, K.; Yoshida, 0.; Kanal, K.; Ueno, A,; Kotera, Y. Deactivation and regeneration of catalyst for steamgasification of wood to methanol synthesis gas. Ind. Eng. Chem. Prod. Res. Deu. 1986,25,239-243. Xu, J.; Froment, G. F. Methane steam reforming, methanation and water gas shift: I. Intrinsic kinetics. AIChE J. 1989a,35 (I), 88-96. Xu, J.; Froment, G. F. Methane steam reforming: 11. Diffusional limitations and reactor simulation. AIChE J . 198913, 35 (l), 97-103.
Receiued for review September 23, 1992 Accepted October 21, 1992
