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Ind. Eng. Chem. Res. 2005, 44, 4834-4840
RESEARCH NOTES Economics of the Clean Fuel Hydrogen in a Novel Autothermal Reforming Process Zhongxiang Chen*,† and Said S. E. H. Elnashaie‡ Department of Chemical and Biological Engineering, University of British Columbia, 2216 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4, and Department of Chemical Engineering, Auburn University, Auburn, Alabama 36849-5127
The economics of pure clean fuel hydrogen produced by steam reforming of hydrocarbons in an earlier suggested novel autothermal circulating fluidized-bed membrane reformer (ACFBMR; Chen, Z.; Elnashaie, S. S. E. H. Chem. Eng. Sci. 2004, 59 (18), 3965-3979; Chen, Z.; Elnashaie, S. S. E. H. AIChE J. 2005, 51 (5), 1467-1481) is evaluated. A detailed autothermal reforming pilot plant is suggested and used for the determination of the specifications and costs of the main units/equipments. Using statistical correlations and cost factors, the total capital investment is determined. The economical analysis data show that the hydrogen production cost decreases with an increase of the plant size in the region of 100-100 000 kg of H2/day. Above this region, the effect of the plant capacity becomes insignificant. For a small pilot plant with a 100 kg of H2/day capacity, the hydrogen cost in the industrial steam methane reforming process is $9.10/ kg of H2, while using this novel autothermal technology, the costs are $2.05/kg of H2 for the methane feed and $2.22/kg of H2 for the heptane feed. The cost reductions are 77.5% and 75.6%, respectively. For a typical large industrial plant with 214 286 kg of H2/day (equivalent to 100 000 Nm3 of H2/h; Scholz, W. H. Gas Sep. Purif. 1993, 7 (3), 131-139), the reported industrial hydrogen production cost by steam methane reforming is $0.74-0.97/kg of H2, while using this autothermal technology, the hydrogen production costs are $0.66/kg of H2 from heptane and $0.50/kg of H2 from methane, respectively. The cost reductions are 10.8-32.0% and 32.4-48.5%, respectively. The comparison of hydrogen production costs over a wide range of plant sizes shows that this novel ACFBMR can be a more efficient and more economical pure hydrogen producer. Introduction Hydrogen is well recognized as the clean fuel of the future.1,2 The most important industrial process for hydrogen production is catalytic steam reforming of hydrocarbons on nickel catalysts.3,4 Recently, a novel process consisting of a circulating fluidized-bed membrane reformer and a catalyst regenerator (CFBMRR) has been suggested and demonstrated to produce pure hydrogen for fuel cells more efficiently and more flexibly.5-12 Figure 1 presents a schematic diagram of the optimized configuration for an autothermal reforming system. Chen and Elnashaie7 have described the details of this optimum autothermal reforming process in their recently published paper. In this investigation, the clean fuel hydrogen produced by steam reforming of hydrocarbons using this novel autothermal reforming process is economically evaluated. From the point of view of practical applications, a more detailed pilot plant shown in Figure 2 is being designed in order to be constructed and operated to obtain more accurate technical and economical pa-
rameters and indices. Detailed specifications of the units or equipments are summarized later in Table 5. Typically, the industrial scale of hydrogen production by steam reforming of hydrocarbons is on the order of 214 286 kg of H2/day (equivalent to 100 000 Nm3 of H2/ h).4 Thus, the range of hydrogen production capacity for economic evaluation varies from a pilot plant of 100 kg of H2/day (which can be used as a remote area housing filling station) to a large steam reforming plant of 10 000 000 kg of H2/day. The estimated hydrogen production cost is compared with the other reported data. As shown in Figure 2, this novel autothermal reforming process is arranged such that it can use naphtha, gasoline, diesel, liquid hydrocarbons, and bio-oils from biomass as the feedstock as well as the most common feedstock of natural gas (whose key component is methane). In the present investigation, we first use heptane as a model component for liquid hydrocarbons to estimate the hydrogen production cost, and then the hydrogen production cost using methane as the feedstock is also estimated. Economic Analysis Methodologies
* To whom correspondence should be addressed. E-mail:
[email protected]. † University of British Columbia. ‡ Auburn University.
Hydrogen production costs are very diverse. This is because the hydrogen production costs reported in the literature each use their own assumptions and methods.
10.1021/ie0504295 CCC: $30.25 © 2005 American Chemical Society Published on Web 05/20/2005
Ind. Eng. Chem. Res., Vol. 44, No. 13, 2005 4835
Figure 1. Optimized autothermal reforming process for efficient pure hydrogen production.
Figure 2. Detailed pilot plant for the novel optimum autothermal reformer-regenerator process.
For example, some reports use a high price of $∼6/GJ for natural gas,4,13 while others use a much lower price of $∼3/GJ.14-16 The prices are also fluctuating yearly. Therefore, to make a better estimation and comparison, the following economical analysis method is used. Annual Chemical Engineering Plant Cost Index. All of the costs/prices reported in the literature were scaled to the same basis, i.e., the year 2003 using the appropriate Annual Chemical Engineering Plant Cost Index (C&E index) in Table 1.17 Economical Analysis Parameters. For the expression of the hydrogen production cost, different units are used in the literature, for example, $/GJ, $/Nm3, or $/kg of H2. Two values of the heat of reaction for hydrogen combustion are typically used, i.e., the low heating value (LHV) and the high heating value (HHV); therefore, the reported costs are different. Unless otherwise specified, the general economical analysis parameters listed in Table 2 are used.
Table 1. Annual Chemical Engineering Plant Cost Index17 year
C&E Index
year
C&E Index
1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992
314.0 316.9 322.7 325.3 318.4 323.8 342.5 355.4 357.6 361.3 358.2
1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003
359.2 368.1 381.1 381.7 386.5 389.5 390.6 394.1 394.3 395.6 401.5
Autothermal Hydrogen Production Cost Estimation Main Process Data and Parameters. For the estimation of the hydrogen production cost by steam reforming of liquid hydrocarbons in the novel autother-
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Table 2. General Economical Analysis Parameters parameter heating values energy costs currency conversion
value
LHV of hydrogen HHV of hydrogen natural gas/methane natural gas/methane liquid hydrocarbon currency German deutsche mark (DM)
0.121 GJ/kg of H2 0.143 GJ/kg of H2 1126.13 kJ/ft3 $3.34/1000 ft3 $197.63/ton U.S. dollar equivalent 0.606
Table 3. Optimization Results for an Autothermal Reformer-Regenerator System7 feed temperature to the riser reformer (K) number of hydrogen membrane tubes number of oxygen membrane tubes steam-to-carbon feed ratio (mol/mol) reaction pressure (kPa) reactor length (m) total feed gas flow rate (kmol/h) solid fraction in the bed (v/v) efficiency of a catalyst regenerator hydrogen production per unit volume of the reformer (kg/h/m3) optimal net hydrogen yield (mol of H2/mol of heptane fed)
845.5 17 72 1.325 29.81 1.731 2.52 0.019 1.00 630.4 16.732
mal reforming process,6,7 the following process data and parameters are used: (1) Previous optimization results have shown that the autothermal process configuration shown in Figure 1 can be the best hydrogen producer with the highest hydrogen yield and minimum energy consumption. The
optimum design and operating parameters for the maximum net hydrogen yield are summarized in Table 3.7 Accordingly, for the cost estimation, Table 4 presents the detailed process data and parameters for the above optimal autothermal reforming process. (2) Service lives of properties:20 plant building and land life, ∼20 years; reformer and other main equipments: ∼12 years. (3) Operating time: 330 days a year, 24 h a day. (4) Feedstocks: heptane is used as a model component for liquid hydrocarbons.6,21,22 (5) Heat exchanger operating mode: countercurrent operation. Specifications and Prices for Main Units/Equipments. Through the process technical calculations, the final specifications for the main units/equipments are determined, as shown in Table 5. Most of the final specifications are larger than the calculated values for the sake of operation flexibility/uncertainty. The prices for these main units/equipments are obtained from the available market data or estimated from the reported prices using statistical corrections.20,23-26 Because the reported price data can be different in different years, to eliminate this kind of fluctuation, all of the prices are standardized to the year 2003 using the Annual Chemical Engineering Plant Cost Index listed in Table 1. (a) Hydrogen Production Cost for a Plant Capacity of 100 kg of H2/day. On the basis of the total cost for the main units/equipments in Table 5, we can estimate the fixed capital investment and then add the working capital to obtain the total capital investment.
Table 4. Process Information for the Optimal Autothermal Reformer-Regenerator System Riser Reformer Construction Parameters and Nickel Catalyst Properties internal diameter of the reformer tube (m)18 outside diameter of hydrogen/oxygen selective membrane tubes (m)19 total percentage of cross-sectional area occupied by membrane tubes (%) nickel catalyst particle density (kg/m3)18 mean diameter of catalyst particles (µm)19
0.0978 0.004 89 22.08 2835 186
Riser Reformer Operation Data reformer temp (K) flow rate (kmol/h)
reaction side
hydrogen membrane side oxygen membrane side
heptane methane carbon dioxide carbon monoxide hydrogen water/steam oxygen carbon solid catalyst (kg/h) hydrogen sweep gas steam oxygen from the air feed nitrogen from the air feed
inlet
outlet
845.5 0.245 0.000 0.000 0.000 0.000 2.272 0.000 0.000 329.8 0.000 8.236 0.629 2.365
742.9 0.000 0.041 1.147 0.0524 0.0146 0.0516 0.000 0.475 329.8 4.184 8.236 0.570 2.365
Catalyst Regenerator Operation Data regenerator temp (K) flow rate (kmol/h)
heptane methane carbon dioxide carbon monoxide hydrogen steam oxygen from the air feed nitrogen from the air feed carbon solid catalyst (kg/h)
inlet
outlet
742.9 0.000 0.041 1.147 0.0524 0.000 0.0516 1.166 4.388 0.475 329.8
1011.3 0.000 0.000 1.715 0.000 0.000 0.1336 0.5828 4.388 0.000 329.8
Ind. Eng. Chem. Res., Vol. 44, No. 13, 2005 4837 Table 5. Summary of the Specifications and Prices of the Main Units/Equipment unit no.
description
specification
dimension (mm)
material
power (kW)
weight (kg)
price ($)
C1 HE1 HE2 HE3 HE4 HE5 HE6 HE7 P1 P2 R1 R2 S1 S2 S3 S4 S5 S6 SP1 SP2
air compressor heat exchanger heat exchanger heat exchanger heat exchanger heat exchanger heat exchanger heat exchanger liquid hydrocarbon pump water pump membrane reformer catalyst regenerator gas hydrocarbon storage liquid hydrocarbon storage water storage desulfurization tank hydrogen production storage nitrogen-rich air storage external hydrogen separator gas-solid separator total
4.7 cfm, 450 psig evaporator (0.34 m2) shell & tube (6.42 m2) shell & tube (13.06 m2) shell & tube (1.92 m2) shell & tube (4.12 m2) shell & tube (0.22 m2) evaporator (0.62 m2) 6.2 GPH, 800 psig 6.2 GPH, 800 psig 1000 K, 30 atm 1000 K 360 ft3, 2400 psig 1100 gal 550 gal flow rate 1-10 GPM 600 gal, 60 atm 600 gal, 60 atm 1000 K, 30 atm 3-6 GPM
838 × 41 × 69
SS 304 SS 304 SS 304 SS 304 SS 304 SS 304 SS 304 SS 303 SS 303 SS SS SS SS SS SS 304 SS SS SS SS CS
1.61
54.9 2.8 53.1 108.0 15.9 34.1 1.8 5.1 20.9 20.9
1964.00 2130.00 5350.00 6335.00 4685.00 5010.00 1685.00 3065.00 855.00 855.00 22237.55 5890.92 855.00 1650.00 825.00 158.00 2750.00 2750.00 3784.25 415.00 73249.72
components
Direct Costs purchased equipment 32 purchased equipment 8 installation instrumentation (installed) 6 piping (installed) 8 electrical (installed) 4 building (including 4 services) yard improvements 2 service facilities (installed) 13 land 2 subtotal direct costs Indirect Costs engineering and 5 supervision constructive expense 9 contractor’s fee 2 contingency 5 subtotal indirect costs total fixed capital investment working capital (15% of the total capital investment) total capital investment
327 × i.d.70 1750 × i.d.70 800 × 165
0.552 0.552
3.2
5.4 2.714
Table 6. Estimation of the Capital Investment Using Plant Component Cost Factors20 assumed % of the total fixed capital investment
330 × 350 × 203 330 × 350 × 203 1750 × i.d. 70 3500 × i.d. 70
cost ($)
ratioed % of the total fixed capital investment
73249.72 18312.43
32.0 8.0
13734.32 18312.43 9156.22 9156.22
6.0 8.0 4.0 4.0
4578.11 29757.70 4578.11 180835.25
2.0 13.0 2.0 79.0
11445.27
5.0
20601.48 4578.11 11445.27 48070.13 228905.38
9.0 2.0 5.0 21.0 100.0
40395.07 269300.44
For the estimation of the capital investment, the method of process plant component cost factors presented by Peters and Timmerhaus20 is used. The detailed cost factors and the cost estimation for the capital investment are summarized in Table 6. Thus, for steam reforming of liquid hydrocarbons using this novel autothermal reformer-regenerator process, the estimated cost for purchasing the main units/equipments is $73 249.72. Including the costs such as those for installation, land, fittings, piping, control, services, instrument, and other fees, the total fixed capital investment is $228 905.38. Assumed the working capital is 15% of the total capital investment,20 the total capital investment is estimated at $269 300.44. For the hydrogen production cost estimation, we need the operating cost, which can be estimated from the unit
consumptions of the raw materials, utilities, and operating labor. The following prices are used for the operating cost estimation, which are already converted to the price for the year 2003 using the Annual Chemical Engineering Plant Cost Index in Table 1. Liquid hydrocarbon: Notice that in this investigation heptane is just used as a model component for higher/ liquid hydrocarbons, for example, naphtha, oil, even gasoline, diesel, or bio-oils. The price for liquid hydrocarbon or heptane can be estimated using the available current prices of naphtha, diesel, gasoline, or bio-oils. The price of naphtha in the international market is about $204-250/ton27,28 or $148-188/ton.29 The price of diesel is $217-256/ton.29 The price of fuel oil using Peters and Timmerhaus’s data20 is $132-186/ton. Again, all of the prices are already converted to the prices for the year 2003. Therefore, taking the average price for those petroleum products, we determine that the average price for liquid hydrocarbons is about $197.63/ton. Electricity: $0.0466/kW‚h.30 Process water (city water): $0.275/ton.20 Cooling water (tower): $0.0475/ton.20 Steam (100 psig): $5.82/ton.20 Note again that, although the prices reported by Peters and Timmerhaus are based on the year 1990, the prices listed above are already converted to the year 2003 using the Annual Chemical Engineering Plant Cost Index listed in Table 1. Labor: $30 600/year/person, for a chemical operator; the reported U.S. national total compensation is $30 517/ year/person.31 Usually, for small pilot plants, “we can assume that the reformers would operate unattended except for necessary maintenance and emergency repairs. The process control computer would on a routine basis electronically transfer operating data to a central monitoring station that has responsibility for multiple reformers”.32 Therefore, we assume that one person is needed to work in a central monitoring station, which is responsible for three pilot plants: one person for one shift, three shifts a day. On the basis of the total capital investment and unit consumptions of raw materials, utilities, and labor, the hydrogen production cost is estimated. As shown in Table 7, for a pilot plant with a capacity of 100 kg of H2/day, the total hydrogen production cost is about
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Table 7. Hydrogen Production Cost in a Pilot Plant with a Capacity of 100 kg of H2/day
Table 8. Hydrogen Production Cost in a Large Plant with a Capacity of 1 000 000 kg of H2/day
Captial Investiment
Captial Investiment
description
cost ($)
cost ($/kg of H2)
total capital investment
269 300.44
0.6801
description
cost ($)
cost ($/kg of H2)
total capital investment
67645212.12
0.0171
Operating Cost
raw materials liquid hydrocarbon process water subtotal
utilities electricity (kWh/kg) steam (byproduct) cooling water subtotal
labor subtotal total hydrogen production cost
Operating Cost
unit consumption (kg/kg of H2)
unit price ($/kg)
cost ($/kg of H2)
raw materials
2.9883 4.9909
0.197 63 0.000 275
0.5906 0.0014 0.5920
liquid hydrocarbon process water subtotal
unit consumption (kg/kg of H2)
unit price ($/kg)
cost ($/kg of H2)
utilities
0.6514 -0.900 0.900
0.046 6 0.005 82 0.000 05
0.0304 -0.0052 0.0000 0.0252
electricity (kWh/kg) steam (byproduct) cooling water subtotal
unit consumption (people/plant)
cost ($/people/year)
cost ($/kg of H2)
1.00
30 600.00
0.9273 0.9273 2.2244
$2.224/kg of H2. For the same hydrogen production capacity, the reported hydrogen production cost by steam reforming of methane in a traditional fixed-bed steam reformer is about $9.094/kg of H2.33 The hydrogen production cost reduction is about 75.54% for a small pilot plant. (b) Hydrogen Production Cost for an Industrial Plant Scale with a Capacity of 1 000 000 kg of H2/ day. As mentioned earlier, the typical industrial plant for hydrogen production by steam reforming of hydrocarbons is in on the order of 100 000 Nm3 of H2/h (or equivalent to 214 286 kg of H2/day). Thus, in this section the hydrogen production cost estimation is performed for a large industrial-scale plant with a capacity of 1 000 000 kg of H2/day. For the same autothermal reformer-regenerator process, the total capital investment can be simply estimated using the “six-tenth factor rule” for the 1 000 000 kg of H2/day hydrogen production plant.20 Thus, the total capital investment is about $269300.44(1000000/100)0.6 ) $67645212.12. For the large industrial hydrogen production plant, the unit consumptions for the raw materials and utilities are the same as those for the small pilot plant, while the operating labor is estimated using statistical correlation. One of the most important methods of estimating labor requirements as a function of the plant capacity is based on the addition of the various principal processing steps on the flow sheets.20,34 For this novel autothermal reformer-regenerator system, the principal process steps can be classified into raw material feed, heat transfer, reaction, separation, and product collection. Thus, the autothermal hydrogen production plant is considered to require five principal process steps. From the statistical data reported by Peters and Timmerhaus,20 for a large industrial plant capacity of 1 000 000 kg of H2/day, the highly automated process plant requires about 59 employee hours/day/processing
unit consumption (kg/kg of H2)
unit price ($/kg)
cost ($/kg of H2)
2.9883 4.9909
0.197 63 0.000 275
0.5906 0.0014 0.5920
unit consumption (kg/kg of H2)
unit price ($/kg)
cost ($/kg of H2)
0.6514 -0.900 0.900
0.0466 0.005 82 0.000 05
0.0304 -0.0052 0.0000 0.0252
unit consumption cost cost (people/year/plant) ($/people/year) ($/kg of H2) labor subtotal total hydrogen production cost
52.00
30600.00
0.0048 0.0048 0.6390
step; thus, for 330 days of annual operation, the operating labor hours required is
59 employee hours/day/processing step × 5 steps × 330 days/year ) 97350 employee hours/year Because the total working hours of one employee in a year is 330/7 × 40 ) 1885.71 h, the required number of operators/workers is 51.63. Thus, 52 working labors are needed. Table 8 shows that the total hydrogen production cost is $0.639/kg of H2 for a large plant with a capacity of 1 000 000 kg of H2/day. For the same plant capacity, the reported hydrogen production cost is about $0.749-0.796/kg of H2 by steam reforming of methane in a traditional fixed-bed steam reformer.14,33 The cost reduction is about 14.69-19.72%. For a good comparison between these two technologies, an important thing we have to mention here is the use of different feedstocks; i.e., liquid/higher hydrocarbon is used in our novel autothermal reformer-regenerator process, while methane/natural gas is used in industrial steam methane reforming. Usually, higher/liquid hydrocarbons are not suitable for steam reforming in classical fixed-bed steam reformers because of the excessive carbon formation. For those higher/liquid hydrocarbon feedstocks, the typical industrial process for hydrogen production is the partial oxidation of hydrocarbons. Scholz4 reported that the hydrogen production cost using partial oxidation of heavy oil/liquid hydrocarbon is about $1.534/kg of H2. Thus, using this novel autothermal reformer-regenerator process, the hydrogen cost reduction is about 58.34% for the same higher/liquid hydrocarbon feed. Hydrogen Production Economical Comparison As demonstrated above, during the hydrogen cost estimation and comparison with the reported data, liquid/higher hydrocarbon is used in our novel auto-
Ind. Eng. Chem. Res., Vol. 44, No. 13, 2005 4839
Figure 3. Comparison of hydrogen costs.
thermal reformer-regenerator process, while methane/ natural gas is used in industrial steam methane reforming. Because the price of the hydrocarbon feedstock significantly affects the final cost of hydrogen,16 in order to provide a satisfactory comparison of the hydrogen cost between the literature data using classical fixed-bed steam methane reforming (SMR-literature) and the estimated data using this novel autothermal circulating fluidized-bed membrane reformer-regenerator process for higher/liquid hydrocarbons (SHR-ACFBMRR), we also estimated the hydrogen production cost by steam methane reforming in this autothermal process (SMRACFBMRR). For the cost estimation of steam methane reforming in this autothermal process, the investigation data presented by Prasad et al.35 is used to calculate the unit consumption of methane, which is about 125.76 Nft3/kg of H2, while the other unit consumptions and the total capital investment are assumed to be the same as those for steam reforming of heptane. Figure 3 shows the hydrogen production costs by steam reforming using two process technologies and two kinds of hydrocarbon feedstocks. The data points in Figure 3 present the reported hydrogen production costs in industrial fixedbed steam reformers from different literatures.4,16,33,36 The first, top, dashed line presents the trend of the hydrogen production cost for the fixed-bed steam methane reforming technology. The lower two curves present the hydrogen production costs for steam heptane reforming and steam methane reforming using this autothermal reformer-regenerator process. Figure 3 shows that the hydrogen production cost decreases with an increase of the plant size in the region of 100-100 000 kg of H2/day. Above this region, the effect of the plant capacity becomes insignificant. The hydrogen production costs using this autothermal reformer-regenerator process are lower than those of the reported literature data and its trend. When the plant capacity is small, for example, in the range of 100-1000 kg of H2/day, the hydrogen production costs in industrial fixed-bed steam reformers are much higher. For example, with the same capacity of 100 kg of H2/day, the hydrogen cost in the industrial steam methane reforming process is around $9.10/kg of H2, while the hydrogen costs are $2.054/kg of H2 for the methane feed and $2.224/kg of H2 for the heptane feed in this novel autothermal reformerregenerator system. The cost reductions are 77.43% for methane and 75.56% for heptane, respectively. Therefore, using this novel autothermal reforming process, the hydrogen production cost can be significantly reduced for a wide range of feedstocks such as natural gas, liquid hydrocarbon, naphtha, even bio-oils, etc. When the plant capacity is larger than 100 000 kg of
H2/day, the decrease of the hydrogen production cost with increases of the plant size becomes much smaller (almost constant). This may explain the phenomenon that most reported hydrogen plant capacities are on the order of 100 000 Nm3/h (or 214 286 kg of H2/day). As shown in Figure 3, the hydrogen production cost using this novel autothermal circulating fluidized-bed membrane reformer-catalyst regenerator process is lower than that using the current industrial fixed-bed steam methane reforming process. If methane is used as the feedstock, the hydrogen production cost is much lower. For example, at a typical industrial plant capacity of 100 000 Nm3 of H2/h (equivalent to 214 286 kg of H2/ day), the reported hydrogen production cost in the industrial fixed beds by steam methane reforming is about $0.739-0.966/kg of H2, while using this autothermal process, the hydrogen production costs are $0.664/ kg of H2 for steam heptane reforming and $0.501/kg of H2 for steam methane reforming. The cost reductions are 10.15-31.26% for steam reforming of liquid/higher hydrocarbons and 32.21-48.14% for steam methane reforming. Because the steam methane reforming process is the largest and the most economical process for industrial hydrogen production,4 the lower hydrogen production cost obtained from this autothermal reformer-regenerator process shows its potential advantages for future practical applications. Conclusions The economics of hydrogen production by steam reforming of hydrocarbons in the novel ACFBMR is evaluated. The results show that the hydrogen production cost decreases from a cost of $2.224/kg of H2 by steam heptane reforming (or $2.054/kg of H2 by steam methane reforming) for a small pilot plant of 100 kg of H2/day to a much lower cost of $0.625/kg of H2 (or $0.454/kg of H2 by steam methane reforming) for a very large plant of 10 000 000 kg of H2/day. The comparison of the economics of hydrogen production shows that the hydrogen production cost using this novel autothermal reformer-regenerator process is lower than the cost reported by the most economical steam methane reforming in industrial fixed-bed reformers, suggesting this ACFBMR can be a more efficient and more economical pure hydrogen producer. Acknowledgment This work was financially supported by Auburn University (Grant 2-12085). Literature Cited (1) Pehr, K.; Sauermann, P.; Traeger, O.; Bracha, M. Liquid hydrogen for motor vehiclessthe world’s first public LH2 filling station. Int. J. Hydrogen Energy 2001, 26, 777-782. (2) Goltsov, V. A.; Nejat Veziroglu, T. A Step on the Road to Hydrogen Civilization. Int. J. Hydrogen Energy 27 2002, 7-8, 719-723. (3) Twigg, M. V. Catalyst Handbook, 2nd ed.; Wolfe Publishing Ltd.: London, England, 1989; pp 225-282. (4) Scholz, W. H. Processes for Industrial Production of Hydrogen and Associated Environmental Effects. Gas Sep. Purif. 1993, 7, 131-139. (5) Chen, Z.; Elnashaie, S. S. E. H. Efficient Production of Hydrogen from Higher Hydrocarbons using Novel Membrane Reformer. Proceedings of the 14th World Hydrogen Energy Conference, Montreal, Canada, 2002. (6) Chen, Z.; Elnashaie, S. S. E. H. Steady-State Modeling and Bifurcation Behavior of Circulating Fluidized Bed Membrane
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Received for review April 8, 2005 Accepted May 12, 2005 IE0504295
