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Low cost compact onsite hydrogen generation
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 4 ) 1 e1 1
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Low cost compact onsite hydrogen generation G.T. Yeh a, Y.L. Kao a, S.Y. Yang a, M.H. Rei a,*, Y.Y. Yan b, P.C. Lee b a b
GreenHydrotec Inc., No.3-1, 2F, Kweishang, Tao-Yuan, 33382, Taiwan Toplus Energy Corp, Taiwan
article info
abstract
Article history:
High cost and lack of convenient supply infrastructure for hydrogen is believed to the
Received 29 April 2014
major hurdle to the commercialization of hydrogen energy. Low cost compact onsite
Received in revised form
hydrogen generator is developed to produce three purity levels of hydrogen for use with
13 August 2014
high temperature polymer electrolyte membrane (HTPEM) or low temperature polymer
Accepted 28 August 2014
electrolyte membrane (LTPEM) fuel cell. The small modular reformer has process efficient
Available online xxx
higher or equal to large scale central production plant without the penalty of expensive distribution cost. The cost of hydrogen from primary reformate hydrogen to high purity
Keywords:
hydrogen ranges from $3.16/kg to $5.84/kg and the corresponding power cost from FC
Low cost hydrogen generation
system is $0.352 to $0.408/KWh. The hydrogen costs are much lower than one can obtain
Low-CO H2 fuel for fuel cell
from an industrial gas company with central supply system and expensive cost in distri-
Steam reformers of methanol or
bution. These direct power costs without depreciation cost are comparable or lower than
natural gas
the comparable size of diesel power cost.
5 KW-FC power system
Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Introduction The intensification of natural catastrophes such as Katrina hurricane in New Orleans in 2005 or earth quake and tsunami in northeastern Japan in 2009 has prompted greater surge in the development of fuel cell (FC) for vehicle, uninterrupted power supply (UPS) for telecommunication transmitters and combined heat and power supply to residential houses. In the transportation sector, in line with the anticipated introduction of FCEV by Toyota and Honda in 2015, the numbers of hydrogen filling stations are being increased in Japan from 208 in 2013 to 308 planned in 2015, in US from 70 in 2015 to 170 planned in 2017 and in Germany for 50 more in 2015 and US DOE study [1e3]. One also sees rapid UPS-FC system in the market growth, 54% between 2010 and 2011 [4]. On the CHP-FC
(combined heat and power-fuel cell) section the Japanese CHP grew at 20% after Fukushima nuclear crisis [5] and the overall, the stationary FC market value is expected to grow from $1.4 billion in 2013 to $14.3 billion in 2020 and the 24,500 units sold in 2012 is expanded to 1,127,560 units in 2018 with an average annual growth rate of 7.7% [6]. In contrary to this intensified activities in the FC development, high cost and the lack of well-located supply logistic of hydrogen fuel has been the most critical factor stalling off the commercialization of the fuel cell and only becomes interested in the literature [3,7,8]. The market cost of hydrogen is dominated by the 40e75% distribution cost in the compressing, shipping and storage from a large central plant to the various users. The production cost itself is influenced by the scale of production and the choice of process feed. A large central production plant may enjoy lower production cost by
* Corresponding author. E-mail address: [email protected] (M.H. Rei). URL: http://www.toplus-e.com.tw, http://www.toplus-e.com.tw http://dx.doi.org/10.1016/j.ijhydene.2014.08.140 0360-3199/Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Yeh GT, et al., Low cost compact onsite hydrogen generation, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/j.ijhydene.2014.08.140
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Fig. 1 e Two sets of 4.5 KW FC system modules in Chips Casting Plant.
the lower depreciation and overhead but is to be burden with vast amount of expenses in the distribution and the storage cost of large volume of high pressure hydrogen in the station in road side or in shopping mall. The distributed supply mode, on the other, will use smaller production plant onsite and supply with lower pressure to the operation site without major storage facility; this eliminates the compression, shipping and storage cost without high pressure hydrogen storage. The improvement of production efficiency in small production facility is desirable to provide additional cost saving to the lower distribution cost in the distributed supply mode. We present here our effort and the result of improving the production efficiency of the small scale onsite hydrogen generator to allow lower production cost and safer supply of hydrogen to the users even in the crowded urban site without the concern of the shipping and storage of large volume of high pressure hydrogen in the busy urban area. The cost of hydrogen has been targeted at $2.0-4.0(2007 $) per GGE by US Department of Energy (DOE) for 2015 [9]. To this target, we report here our onsite compact methanol hydrogen generator for the production of primary reformate hydrogen (75%H2), of LoCO hydrogen fuel with 2e4 ppm CO and of 99.995 þ %hydrogen; these different graded hydrogen (H2) has been used as the fuel for fuel cell power generation without difficulty.
Experimental
chips-casting.com) for power and hot water washing of the de-waxed casting molds (Fig. 1). This was a government sponsored FC-DEMO program with online monitored by the government agency. When surplus hydrogen from FC stuck was recovered as fuel in the reformer, each reformer consumed 3.780 kg/h of methanol and RO water of 2.97 kg/h to produce 7.5CMh of hydrogen in the primary reformate; the primary reformate had a composition of 75%H2, 24%CO2 and 1.0%CO. For heating up the reactor for hydrogen production, 0.192 kg/h or 1.200 kg/ h of methanol fuel was used with or without the recovery of vent hydrogen from FC stack, respectively; this corresponds to a process efficiency of 102.3% or 81.6%, respectively. The crude hydrogen was further purified with 900 L/h of air for selective oxidation with a proprietary oxidation catalyst of Co modified Pt/Alumina at 110e120OC to obtain a net 7.5 CMh of LoCOH2 fuel. The reformer took 20 min to reach 250 C reaction temperature and another 10 min to yield stable LoCO H2 fuel with 2e5 ppm of CO. The power efficiency of the FC sacks was 0.8 KWh per 1000 L of hydrogen in the LoCO H2. Throughout this program between Feb 20, 2011 and May, 2011, the total methanol consumption, power output and hot water (25e80 C) were 14,400 kg, 14,765 KWh and 543.6 Ton, respectively, in an accumulated operation hours of 1791 h. The typical IeV curve and power output are shown in Figs. 2 and 3. Throughout the program, the thermal efficiency was 18.5% for power output and a total efficiency of 58.6% including hot water generation. Based on the report of Taiwan Power company, there was 536 gm CO2 emission per KWh of
9 KW fuel cell CHP system in a casting plant for power and hot water A 9 KW fuel cell system was composed of two 7.5 M3/hr (CMh) methanol reformers and two water cooled 4.5 KW FC stack (Toplus Energy Corp., http://toplus-e.com.tw); the hydrogen from the reformer was further purified by selective oxidation of CO (DeCO) with air to 2e4 ppm (70%H2) for direct utilization by FC stack for the power generation. Design and fabrication of this methanol steam reformer for the production of LoCO hydrogen (LoCOH2) fuel for fuel cell power generation has been reported [10]. The power from the fuel cell system and the vent hydrogen were used for a hot water heater in a precision casting plant (Chips Investment Casting Inc., www.
Fig. 2 e IeV curve of power output from 5 KW FC system with methanol reformer.
Please cite this article in press as: Yeh GT, et al., Low cost compact onsite hydrogen generation, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/j.ijhydene.2014.08.140
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Fig. 3 e Time on stream of power output from 5 KW FC system with methanol reformer.
power generation and a 41.64% thermal efficiency; this leads to a 38.8%CO2 reduction in the power generation of 14,765 KWh (1791 h) during the testing period of 1791 h.
5 KW fuel cell CHP system with a natural gas or LPG steam reformers of 8M3/h 5 KW FC CHP system is constituted with a prior-sulfur (<2 ppm) removing reactor, a natural gas (NG) steam reformer (also used for LPG), heat exchanger and CO-purifier with high temperature and low temperature water gas shift reactors followed by two stages DeCO reaction with Comodified Pt/geAl2O3 catalyst (0.8 kg) for CO reducing from 0.6e1.0% to 2e4 ppm. Two stages sulfur removal reactors, DS1 and DS-2 with commercial catalysts of DP-90 (4.1 L) and DP45 (0.9 L) of BASF were used for sulfur removal at room temperature with VHSV ¼ 500h1 and 2300 h1, respectively. The steam reforming reformer was filled with 2.4 kg of combustion catalyst (OXD, a hBN promoted Pt/geAL2O3, or PBN) and 2.8 kg of SRR catalyst (Ce and Ru modified NiO/geAl2O3). The
Fig. 4 e Reactor assembly of the steam reforming of natural gas or LPG.
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Fig. 5 e Block diagram the natural gas (or LPG) steam reforming reaction.
assembly of this NG/LPG reformer system is shown in Figs. 4 and 5. The NG/LPG reformer had multiple columns for preheating and steam reforming in two copper blocks similar to previously reported methanol reformer design; the reactor blocks were inserted into a stainless steel tube (180 mmOD 400 mmL) as the shield; the two copper blocks are for feed pre-heating, PHT, (160 mmOD 100 mmL) and steam reforming reaction,SRR, (160 mmOD 250 mmL). This gives a total reformer volume of 10.184 L (or 1.36L/CMH2) excluding heat exchanger and WGSR (water gas shift reaction). There were four catalytic heating tubes (28 mmID 500 mmL) filled with OXD catalyst at the center section surrounded by multiple columns filled with SRR catalyst in the SRR block (Fig. 6); the reaction temperature was maintained at 730e770OC for reaction as shown in Fig. 7. In addition to the above PHT block for the final stage preheating to 750 C, two additional pre-heaters were used for the first and the second stage preheating of the reactants (NG or LPG and RO water in a 3.5 ratio of H2O/C). As shown in Fig. 3, the 2nd stage HEX was an aluminum block of 250 250 150 mm with multiple columns for heat exchanging of feeds mixture with the hot vent gas streams of two OXD vent streams and the SRR product stream before undergoing water gas shift reaction (WGSR). The crude reformate was set for two staged WGSR to reduce CO; the high temperature (350e450 C) WGSR was 350e450 C while the low temperature reactor was 230e280 C to reduce CO from 13% to 0.8e0.9%. The first stage pre-heater was a tube and shell type heat exchanger with fuels (NG fuel and air) in the tube side while the exit streams of the HEX-2 in the shell side as the heating sources at about 100 C.
Fig. 6 e Cross section of the PHT and SRR blocks.
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condition running for 487.5 days (11,700 h) and has maintained steady state for both hydrogen and CO concentration as shown in Fig. 11.
5 CMh high purity hydrogen generator
Fig. 7 e Steady temperature in NG reformer with catalytic heating.
To start up the reforming reaction, methanol was used as the fuel for the cold start to bring up catalytic bed for the initial period of the reaction, the recovered hydrogen mixture from the fuel cell vent was then used to continue heating up the reactor system. Alternatively, an electric heater is used for the initial heating till 350 C; then natural gas is used either from the supply line or from the recovered natural gas of the fuel cell vent. As shown in Fig. 8, it takes about 44e45 min to reach the stable reaction temperature of 730e750 C. The temperature in PHT, SRR and HEX was found to be 792, 753 and 289 C, respectively; in the SRR section, the temperature distribution from the inlet, 5 cm, 15 cm and 25 cm upward was 729, 750 and 742 C, respectively. Table 1 lists the result of reformate after HTWGS, LTWGS, DeCO1 and DeCO2 processes. This reformer is connected with a 5 KW fuel cell system by Toplus Energy to generate 5 KW power with waste heat being recovered for 400 L/h hot water at 70 C. The thermal efficiency of this steam reformer is 74.8% with NG and 74.6% with LPG and overall efficiency of 30.2% for power and 65.4% including hot water. The IeV curve of the power output is shown in Fig. 9. The assembly and photo of the complete set is shown in Fig. 10.
Life test of hydrogen generator A 2.0 CMh hydrogen generator [10], weighting 19 kg (125 Lit) is used for this long term stability test; the reformer is heated up with 120 gm of PBN combustion catalyst [11] by 330 g/h of methanol fuel and 3000 L/h of air. 960 g/h of methanol feed (H2O/C ¼ 1.4 mol) was fed for the generation of hydrogen in the SRR section containing 800 gm of CuOZnOAl2O3 catalyst. The methanol/water feed was turn down in the evening while the reactor was kept at 260 C continuously since 11/13/2012. Up to now (03.16.2014), it has been kept under reaction
Fig. 8 e SRR temperature change during start up.
This hydrogen generator was composed of a 7.5 CMh methanol reformer and a 5 CMh PSA purifier. The performance of the reformer has been described previously [2]. The PSA was supplied from Beijing GH2 Power (http://www.gh2power.cn). At 260 C and 0.68 MPa, the reformer provided 7.0 CMh of hydrogen in the primary reformate with 75%H2, 24%CO2 and 1.2%CO composition from 4.8 kg/h of methanol in feed (H2O/ C ¼ 1.5) for SRR and 1.43 kg/h of methanol fuel for heating before vent hydrogen from PSA was recovered as the fuel; 5.04 CMh of pure hydrogen were obtained with a pressure of 0.13 MPa and purity of over 99.99997e99.999996%H2 with CO2: 31e110 ppb; CO: 1e26 ppb and TCH:<2e10 ppb by two professional analytical services. The reformer and PSA were housed in a steel plate box of 1040 mm 840 mm 2240 mmH (Fig. 12); the waste hydrogen from PSA was incinerated at this moment and would be used for boiler heating in a 20 KW CHP system for another FC-DEMO program.
Testing results of a 20 KW CHP/FC system in Taiwan A 20 KW CHP/FC system was installed for lighting and swimming pool of the gymnasium complex of National Taiwan University of Science and Technology (NTUST, http:// www.ntust.edu.tw) in Taiwan (Fig. 13); four 4.8 CMh hydrogen generators and four 5 KW FC systems are used to form this 20 KW CHP/FC system. Each hydrogen generator module is composed of a 4.8 CMh PSA unit and a 7.5 CMh methanol reformer with output pressure at 0.68 MPa; the unit has a weight of 400 kg and a total volume of 1,957 L or 407.7 L/CMh. The power and hot water of the FC system was supplied by 4 sets of 5 KW FC system which was composed of 4e5 CMh high purity hydrogen generators described above and 4-sets of 5 KW FC system utilizing high purity hydrogen fuel. Fig. 14 shows a simplified layout of the setting. The material balance of the system is shown in Fig. 15 indicating a 23% thermal efficiency based on the methanol consumption for the power generation, 27 or 50% for the hot water generation with an overall thermal efficiency of 50.2% or 73.2% if waste heat from the FC cell is recovered. This FC cell generates a net 20 KWh of power output from the 17.5 CMh hydrogen input with a power conversion of 38.2% from hydrogen; however, the cell stack does not have waste heat recovery from its power conversion resulting in lower thermal efficiency on the waste heat recovery. Fig. 16 shows the actual power output in response to the power demand of the gymnasium. Nevertheless, this CHP/ FC power system does provide an 18% cost saving and a 29% CO2 reduction from the reduction of electricity and natural gas consumption. With the average methanol price at $360 MT, the power cost is calculated to be $0.366/KWh or lower if equipment costs are reduced in mass production scale, say 20 MW system.
Please cite this article in press as: Yeh GT, et al., Low cost compact onsite hydrogen generation, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/j.ijhydene.2014.08.140
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Table 1 e The results of steam reforming reaction of NG/LPG at 720 C. Feed
NG LPG
VHSV, hr1
6000 4500 6000 4500
Feed, M3/hr
2.26 1.69 0.85 0.63
Fuel, M3/hr
1.21 0.90 0.43 0.33
Composition (%), dry gas H2
CO, ppm
CO2
CH4
70.12 70.31 70.43 70.78
2.6 2.2 2.7 2.1
18.13 18.77 18.25 18.60
0.47 0.39 0.40 0.33
Results and discussion Unique features in the methanol reformers The design of our compact high efficient reformer has been reported before. The uniqueness of this design is the provision of the proper surface area from the multiple columns in PHT (preheater) and SRR sections and allowance of the sufficient solid mass of reformer medium between the channels to ensure sufficient mass for the required heat transfer from the OXD to PHT and SRR sections as described elsewhere [11]. The heat transfer from the catalytic heater relies upon thermal conductance through the reformer medium; therefore, sufficient mass of the medium is to ensure effective heat transfer and storage in the reformer block. This storage of thermal energy in the reformer block enables it to play as a secondary origin for the heat transfer to the individual column of the feed preheating and the steam reforming reaction. As a result, the highly efficient heat transfer in the reactor mass lead to a high overall heat transfer coefficient with an Uvalue in the range of 200e250 W.M-K; it also brings about easy scale up of the reactor because the reactor block plays as a second heat source for the heat transfer to the catalyst beds and avoid the long distance heat transfer in a larger reactor. In comparison, an open fire heater generally requires a well controlled gas flow in the multiple burners and a spacious volume for convection and radiation to reach an even distribution of reaction temperature. The methanol reformers in various capacities have been used in the previous hydrogen generation for HTPEM and LTPEM with LoCO hydrogen fuel and for a 50 CMH onsite industrial plant containing a PSA purifier to 99.995e99.9995% purity of hydrogen as shown in Table 2. Finally, this unique design of having balanced reactor mass and surface area of catalyst columns in the reformer enables us
XCH4 %
H2, CMh
Therm. efficy., %
97.34 97.81 97.80 98.12
8.09 6.00 8.05 6.00
75.2 75.1 75.1 75.6
to fabricate various sized methanol reformers for hydrogen supply units from 2 CMh to 50 CMh for use in 1 KW to 10 KW fuel cell power systems of HTPEM and LTPEM as well as for steel plant with 99.995% purity; we also fabricate onboard methanol reformers of 1.5e8 CMh for use in hydrogen enhanced combustion (HEC) to boost engine efficiency in fuel consumption and in abatement of pollution in exhaust stream [4].
New design of natural gas steam reformer with a catalytic heater The use of reactor mass as a heat conduit for heat transfer is adapted in the newly fabricated 8 CMH NG (also for LPG) reformer. Because of high reaction temperature, the reactor media for heat transfer is made of copper in column-type blocks inside a stainless steel tube. Two copper blocks containing multiple columns for catalysts are used for PHT and for SRR at 720e750 C; both of these two blocks are enclosed in a stainless steel pipe which functions as protection material and also slows down heat loss from the higher temperature inside. Because of much higher requirement of the reaction heat for the NG reforming at 750 C, 192.36 KJ of NG vs. 59.12 kJ for methanol at 250 C, two external heat exchangers made of aluminum alloy and an internal copper PHT are used. The copper PHT block is placed upstream to the SRR block to allow sufficient preheating of the reactants mixture; both PHT and SRR blocks are heated by 4-heating tubes with fuel being preheated in the two external HEX. The catalyst in SRR is a Ce and Ru metal oxides modified nickel catalyst filled up in the multiple columns for the steam reforming of NG or LPG. Methanol or NG as heating fuel is introduced with air in the PHT inlet, SRR is heated by the hot feeds stream from PHT section. The heating gases from the 4-heating tubes are vented out into an aluminum block heat exchanger, HEX-1, akin to the previously published structure; the vent gas of this HEX1 is used to heat up fuel mixture in another HEX-2 before they entered into OXD sections.
Hydrogen purity and its usages
Fig. 9 e Typical IeV curve of 5 KW FC power output using LoCO H2 fuel from NG.
The hydrogen in the primary reformate from either methanol or NG SRR contain 75%e78% of H2, 0.9e1.2%CO and the balance amount of CO2; this type of hydrogen has been successfully used for HTPEM with 3 KW output in 2008 and for HEC in several internal combustion engine tests to upgrade engine efficiency. The hydrogen is further purified by selective oxidation of CO with our proprietary catalyst in two stages oxidation with air at 110e130 C to bring down CO content to 2e5 ppm; the resultant LoCO hydrogen fuel, 70%H2, 2e5 ppm CO and balance amount of CO2 and N2 was directly used for
Please cite this article in press as: Yeh GT, et al., Low cost compact onsite hydrogen generation, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/j.ijhydene.2014.08.140
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Fig. 10 e Assembly and photo of a 5 KW FC power system with a NG reformer of 8 CMH.
Fig. 11 e Life time test for a 2 CMH methanol reformer.
power generation of 5 KW and 9 KW with LTPEM in two FCDEMO programs in 2009 and 2011. At this low level of CO, its poisonous effect on MEA of FC appears to be negligible and yield stable power output [12]. We have compared the power output from LoCO H2 fuel with that of power output using an independent blended 75%H2, 0 ppm of CO and 25%CO2; they are practically identical. The power outputs from these FC systems using a MEA of Pt/Re catalyst system [13] are steady as shown in Figs. 2, 3 and 9. In order to provide high purity hydrogen in the industrial hydrogen market, the primary reformate was purified with PSA to 99.9999 þ %; two cases have been undertaken. One was the assembly of seven 10 CMh methanol reformers with a PSA
purifier for an onsite plant of 50 CMh H2 for the surface treatment of stainless steel wire in Wenchow, China. A new one is developed for the another FC-DEMO program with a 20 KW CHP type power system with LTPEM and hot water supply to a warm water swimming pool of National Taiwan Technology University in Apr of 2014 (Fig. 12); the electricity of this system is used to light the gymnasium while the waste hydrogen from the PSA purifier is burned to provide hot water for the swimming pool. The heat recovery of the cell stack is not installed; as a result, the overall thermal efficiency of this system is regrettably lower. The high purity of hydrogen fuel allows the fuel cell stack to convert into 1.36 KWh per CMh of hydrogen fuel (45.3%); however, it becomes 1.14 KWh/CMh of
Fig. 12 e A 5 CMh high purity hydrogen generator. Please cite this article in press as: Yeh GT, et al., Low cost compact onsite hydrogen generation, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/j.ijhydene.2014.08.140
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Fig. 13 e Photo of 20 KW CHP/FC system in Taiwan.
Fig. 14 e A simplified layout of the 20 KW CHP/FC power system in Taiwan.
hydrogen fuel after internal power consumption of BOP in the hydrogen generator and cell stack resulting in a net power efficiency of only 38.2%. The hydrogen purity of the hydrogen generators is unexpectedly high and can be used for process hydrogen in high technology industries such as semiconductor or photovoltaic industry.
The cost of hydrogen by methanol and by natural gas The cost of hydrogen depends tightly with the choice and the cost of the raw material of the process. In Taiwan and in S.E.
Asia using liquefied NG (LNG) the LNG price is around $15-18/ MMBTU while methanol price follows international price of about $330 to $520/MT in 2012e2014Q2 with an average price of around $360 MT between 2012 and 2014 and falls down to $330 in 2014Q2. If we adapt an average methanol price of $360/ MT and $0.638/CMNG (equivalent to $17/MMBTU), the price of hydrogen in various qualities with a 5 CMh unit is shown in Table 3. The hydrogen cost from methanol is about 86% of that from LNG; this is brought about by a relatively lower temperature and simpler processing condition and can be even
Fig. 15 e Material balance of the 20 KW CHP/FC power system in Taiwan. Please cite this article in press as: Yeh GT, et al., Low cost compact onsite hydrogen generation, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/j.ijhydene.2014.08.140
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Fig. 16 e Power output of 20 KW CHP/FC power system in Taiwan.
lower if methanol price prior to Nov, 2013 to Feb, 2014 surge is used. Even at these hydrogen prices of $4.66 kg at 2014 $ value shown in Table 3, it is lower than those expected from the SRR of NG onsite ($4e5 kg) or offsite ($6e8 kg) in the literatures [14,15], and also much lower than power cost of wind ($8e10/ kg) and solar (via electrolysis, $10e12/kg). Our $4.66 kg is lower than or about the target price of the DOE of US, $2.0e$4.0 (in 2007$) [1]. The relative cost of methanol and NG based hydrogen will be reversed in areas where NG cost is only $4 to $9/MMBTU; the cost of LoCOH2 and 5NH2 in those area would become $0.14($1.12/GGE) and $0.20($1.86/GGE) at $4.0/ MMBTU, respectively. The capital cost of hydrogen generators using methanol is only 45%e75% of those using NG depending on the hydrogen purity. The lower cost for methanol reactor is attributed to higher purity of methanol, simpler process steps and the lower reaction temperature 250 C vs. 750 C demanding more expensive reactor materials, copper and stainless steel vs. aluminum.
The cost of hydrogen by distributed vs. central supply system It clearly shows that hydrogen from distributed onsite production is much lower in cost than one can obtain from hydrogen produced in a central plant and distributed by cylinder bundle or by long tube trailer and accordingly their power cost in a fuel cell system. It is often quoted that a big scale central production plant of hydrogen will be more efficient and much cheaper in production cost [16]; however, with these 5e10 CMh modular system presented here, their efficiency is already at 83e87%, it is higher or equal to a large plant can have [8]. Next the depreciation factor in large plant may have advantage over small scale plant; however, the system presented here is also has fairly reasonably low sharing of depreciation in the total cost. The compression, shipping and storage have always been the major factor of hydrogen price, 45% and 70e75%, respectively, in Taiwan and in the costal part of China. As economy develops, the shipping and storage cost is not necessarily going down unless the costly liquefied hydrogen system is to be enacted. As a result a central supply system of hydrogen will be difficult to become more competitive than a high
efficient distributed supply system. Besides the high cost, the central production distributed by long tube trailer may be too high in supply volume and too bulky in space demand (70 m2 plus drive way) for a road-side hydrogen station or for hydrogen supply to a UPS of a cell phone transmitter in the urban area. Furthermore, the distributed hydrogen supply is a modular setup, the production capacity can easily grow with the market demand without wasting to much investment up front and thus reduces the risk of investment in the early stage of hydrogen energy. Next we notice that the hydrogen made with methanol is much cheaper in the production cost and in its capital expenditure. This phenomena prevails when natural gas is relatively expensive in the area where it is imported by LNG; when LNG is the source of methane, it costs at about US$1517/MMBTU for importation in eastern Asia and an additional $1-2/MMBTU for the storage, gasification and piping to the user while methanol at $360/MT is equivalent to $16.6/ MMBTU in energy content with a much lower distribution cost to be added to the user. Moreover, the production of hydrogen from methanol is much more efficient, lower cost and lower capital demand than it is from using NG as the raw material, Therefore, in contrast to N. America where NG is only $4.0-4.5/ MMBTU, in LNG importing area such as Taiwan, Korea and Japan, methanol will be a better choice as the raw material for producing hydrogen than is from NG, particularly in small to medium scale.
The potential market of using these compact hydrogen generators On the choice of hydrogen fuel for FC power system, if it is a HTPEM, the hydrogen from primary reformate from SRR of methanol will be the best choice as the hydrogen fuel in cost and in process simplicity and in the compact reactor space. For LTPEM, either LoCOH2 or high purity hydrogen from the SRR of methanol can be used depending on how much weight consideration is to be placed on the initial investment, the space or volume of the facility and the start-up time. It takes about 30 min for the LoCOH2 to get ready for the stabilization of CO content and power generation but it will requires about 1 h for the methanol reformer-PSA system to get ready for the hydrogen to reach to H2 with CO <1 ppm and the power generation. The advantage of having higher power efficiency (1.36 KWh/CMh or 45.3%) by using high purity hydrogen fuel would be lost if power efficiency with LoCOH2 fuel can be upgrade to 1 KW per 1 CM of hydrogen fuel. In the past two years, we have worked together with six FC system companies in Taiwan, their power efficiency ranged from 0.7(23.3%) to 1.1(36.7%)KW/CMH2 output; the power cost will drops from $0.501/KWh to $0.417/KWh at 1.1 KW/CMH2. Therefore, there is room for the improvement of power efficiency with LoCOH2 fuel; this will be a good topic for the researcher in this field. Natural gas as the raw material can be competitive against methanol only when NG is shipped by pipeline instead of by liquefaction to LNG. As shown in Table 3, with respect to the raw material of hydrogen fuel of SOFC, the hydrogen in primary reformate from SRR of methanol will be a better choice than from NG as it is common in areas where the cost of NG is much lower than
Please cite this article in press as: Yeh GT, et al., Low cost compact onsite hydrogen generation, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/j.ijhydene.2014.08.140
Type
H2, SM3/hr CO, HiCO, LoCO Application Reformer Size, mm Reformer weight, kg
GHM-2CMh
GHM-5CMh
2 5 1.2% in reformate, 2e4 ppm in LoCO H2 HTPEM, LTPEM 340 170 200H 240 210 600H 11 63
GHM-7.5CMh
7.5
300 420 700H 75
GHM-50CMh
50 1.2%/in reformate, <1 ppm in 5NH2 HT/LTPEM & Ind. H2 300 420 800H 100
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Table 2 e Various hydrogen generators with basic methanol steam reformers.
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Table 3 e The cost of hydrogen with different purity with methanol ($360/MT) or natural gas ($17/MMBTU) as the feed by the 5 CMh hydrogen generator. 75%H2a
Items c
LoCOH2b
Raw material
MeOH
Capital, US$ Feed/CMH2d, kg or CM/CMH2d Fuel/CMH2, kg or CM/CMH2 H2O/CMH2, kg/CMH2 Elec.,KWh/CMh Dir. Cost, $/CMH2 Indir. coste, $/CMH2 Total cost, $/CMH2 Cost industrial H2, $/kgH2 $/kg or $/GGEf Dir elec. Costg, $/KWh Indir. elec.Costh, $/KWh Total elec. Cost, $/KWh
7500 16,500 10,500 0.48 0.263 0.51 0.14 0.14 0.16 0.32 1.48 0.4 0.04 0.06 0.08 0.227 0.251 0.253 0.030 0.071 0.041 0.257 0.322 0.294 11.20 (by long tube trailer), 18.70 (by cylinder bundle) 2.88 3.61 3.29 0.321 0.402 0.368 0.115 0.115 0.115 0.436 0.517 0.483
a b c d e f g h
NG
MeOH
5NH2 NG
MeOH
NG
19,500 0.28 0.15 1.58 0.12 0.274 0.084 0.358
21,700 0.685 0.19 0.49 0.12 0.331 0.086 0.416
28,900 0.376 0.18 2.12 0.18 0.417 0.125 0.542
4.01 0.447 0.115 0.555
4.66 0.347 0.115 0.462
6.07 0.434 0.115 0.549
75%H2 means hydrogen from primary reformate. LoCO H2 from 70%H2 and 2e4 ppm CO. MeOH stands for methanol. kg or CM of methanol or NG, respectively per CM of H2. Based on 7-yr depreciation and 3% maintenance of capital. 1 kg H2 ¼ 11.2 CMH2. Power efficiency of 1 CMh hydrogen of generates net 0.8 KWh of power by 75% H2 or LoCOH2 and1.2 KW of power by 4NH2. Based on 7-yr depreciation and 3% maintenance of capital cost of $26,700 for a 5 KW FC unit.
in LNG area, the advantage of using hydrogen from SRR of methanol comes not only in the hydrogen cost but also in the simplicity of process from the cleaner feed (sulfur cleaning), the low reaction temperature (250 vs. 800 C) and more significantly, in the lower energy requirement of methanol SRR than that of SRR of NG (2790 vs. 6760 KJ/CMH2). With methanol SRR based SOFC, the high conversion temperature and the energy content from the stack can be effectively passed on for the endothermic process of methanol SRR with surplus heat for other heat recovery. This is more so in the case of small to medium sized SOFC where not only cost advantage can be realized but also the compactness to allow the penetration of SOFC into CHP power supply system of average household or building. The partial testing results of the 20 KW CHP/FC system in Taiwan shows that it can have a power cost of $0.366/KWh if methanol is valued at $360 MT; this power cost can be reduced further if more rigorous recovery of waste heat from FC-stack is installed (about 23% more heat recovery) and it is in a larger system, say 20 MW, through lowering of capital investment (around 40% reduction). With an accumulated active operation time of 250 h up to Aug 5th (9am to 6pm active supply of power and hot water and 6pm to 9am in standby status at 200e230 C), it has demonstrated a capability of weather-proof stability (2-hurricans invasions) flexibility of power adjustment and the relative economic advantage in comparison with Diesel power system in the off-island of Taiwan, if not with the main grid system in the main island of Taiwan. Such a FC power system in the off-island or remote area where a sophisticated power grid system is expensive to install will not only provide saving in the power cost and stability in the power supply but also will provide additional advantage in the hot water supply for household usage or for the desalination of brine water or as a supplemental power stabilizer to wind or
solar power whose power supply is subjected to weather interference.
Conclusion Low cost compact reformers have been successfully developed to produce stable and durable hydrogen fuel for fuel cell power generation. These onsite hydrogen generators are highly efficient in producing low cost hydrogen at the user site eliminating the expensive distribution cost and avoiding storage of large volume high pressure hydrogen; the product hydrogen can be used as direct fuel for HTPEM or purified as LoCO H2 fuel or as high purity hydrogen for LTPAEM or for industrial hydrogen utilities. The LoCOH2 can be used as a direct fuel for LTPEM system provided that the catalyst in MEA is modified with Pt/Re to resist potential CO poisonous effect. A FC system using LoCOH2 fuel provides a compact and low capital cost option as compared with that using high purity hydrogen. These low cost hydrogen form the compact onsite reformers can help overcome the hurdle of hydrogen supply to the hydrogen stations or UPS station in the urban area. Their cost of hydrogen and power can be obtained at $2.73/GGE and $0.35e0.40/KWh with methanol at $360/MT ($16.6/MMBTU). Using$16.6MMBTU for both methanol and NG, the hydrogen and power from using methanol as the starting material is lower than from NG as the starting material; this is critical in the LNG import area for the proper selection of raw material to produce hydrogen. The 20 KW CHP/FC power system in Taiwan demonstrates that FC power can have a stable power supply capability of flexibility, weather-proof and low cost in comparison with Diesel power and can be a supplemental power to the
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conventional renewable power of wind and solar energy. In the early stage it can be developed as a competitive distributed power system in the off-island or remote area where central power grid is not well developed.
references
[1] Fuel Cell Today. The propagation of hydrogen stations. Fuel Cell Today Apr. 10, 2013. http://www.fuelcelltoday.com. [2] US DOE. DOE issues request for information on fuel cells for continuous on-board recharging for battery electric lightduty vehicles. Jul 2, 2014. http://www.hydrogen.energy.gov/ cf/news_detail.cfm/news_id¼21564. [3] Braun Peter. Daimler gets hyped on hydrogen. Digit Trends Oct. 2, 2013. http://www.digitaltrends.com/cars/daimlergoes-big-on-h2-plans-to-bring-400-hydrogen-filing-stationsto-german-in-the-next-decade/. [4] Ind, Econom. Knowledge Res. Center, (IEK), Taiwan, Mar 2012. http://ieknet.iek.org.tw A monthly publication of IEK Res. Ceter of ITRI, Taiwan. [5] Shimizu Seita. CHP market & policy movement in Japan. Jpn Gas Assoc Feb 2013. [6] Nikkei BP Cleantech Institute. Handbook of world smart house building. Oct 24, 2013. [7] Blencoe Greg. Cost of hydrogen from different source. Hydrogen Car Revolut Blog Nov. 9, 2009. http://www. h2carblog.com/?p¼461.
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[8] Fuel Cell Technology Office. Hydrogen production in multiyear. Res Dev Demo 2012. http://energy.gov/eere/fuelcells/. [9] US DOE. Progress report for the DOE hydrogen and fuel cells program. Chapter III-3. December 2013. DOE/GO-1020134260. [10] Wang Harvey HF, Chen SC, Yang SY, Yeh GT, Rei MH. Design of compact methanol reformer for hydrogen with low CO for the fuel cell power generation. Int J Hydrogen Energy 2012;37:7487e96. [11] Tsai Yihsiu, Wang Harvey HF, Yeh Guan-Ting, Rei MH. hBoron nitride as a promoter for reactive and stable combustion catalyst. [submitted for publication]. [12] Bhatia KK, Wang C-Y. Transient carbon monoxide poisoning of polymer electrolyte fuel cell operating on diluted hydrogen feed. Electrochem Acta 2004;49:2333e41. [13] Wang Deli, Subban Chinmayee V, Wang Hongsen, Rus Eric, ~ a Hector D. Highly stable and CODiSalvo Francis J, Abrun tolerant Pt/Ti0.7W0.3O2 electrocatalyst for proton exchange membrane fuel cells. J Am Chem Soc 2010;132:10218e20. [14] The National Academies. The hydrogen economy. Washington, D.C. USA: The National Academies Press; 2004 [Chapter 4], http://www.nap.edu. [15] Ramsden T, Steward D, Zuboy J. Analyzing the levelized cost of centralized and distributed hydrogen production using the H2A production model, version 2. Technical Report, NREL/ TP-560-46267. September 2009. [16] IEA Energy Technology Essentials. Hydrogen production and distribution. www.iea.org/Textbase/techno/essentials.htm.
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Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/locate/he
Low cost compact onsite hydrogen generation G.T. Yeh a, Y.L. Kao a, S.Y. Yang a, M.H. Rei a,*, Y.Y. Yan b, P.C. Lee b a b
GreenHydrotec Inc., No.3-1, 2F, Kweishang, Tao-Yuan, 33382, Taiwan Toplus Energy Corp, Taiwan
article info
abstract
Article history:
High cost and lack of convenient supply infrastructure for hydrogen is believed to the
Received 29 April 2014
major hurdle to the commercialization of hydrogen energy. Low cost compact onsite
Received in revised form
hydrogen generator is developed to produce three purity levels of hydrogen for use with
13 August 2014
high temperature polymer electrolyte membrane (HTPEM) or low temperature polymer
Accepted 28 August 2014
electrolyte membrane (LTPEM) fuel cell. The small modular reformer has process efficient
Available online xxx
higher or equal to large scale central production plant without the penalty of expensive distribution cost. The cost of hydrogen from primary reformate hydrogen to high purity
Keywords:
hydrogen ranges from $3.16/kg to $5.84/kg and the corresponding power cost from FC
Low cost hydrogen generation
system is $0.352 to $0.408/KWh. The hydrogen costs are much lower than one can obtain
Low-CO H2 fuel for fuel cell
from an industrial gas company with central supply system and expensive cost in distri-
Steam reformers of methanol or
bution. These direct power costs without depreciation cost are comparable or lower than
natural gas
the comparable size of diesel power cost.
5 KW-FC power system
Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Introduction The intensification of natural catastrophes such as Katrina hurricane in New Orleans in 2005 or earth quake and tsunami in northeastern Japan in 2009 has prompted greater surge in the development of fuel cell (FC) for vehicle, uninterrupted power supply (UPS) for telecommunication transmitters and combined heat and power supply to residential houses. In the transportation sector, in line with the anticipated introduction of FCEV by Toyota and Honda in 2015, the numbers of hydrogen filling stations are being increased in Japan from 208 in 2013 to 308 planned in 2015, in US from 70 in 2015 to 170 planned in 2017 and in Germany for 50 more in 2015 and US DOE study [1e3]. One also sees rapid UPS-FC system in the market growth, 54% between 2010 and 2011 [4]. On the CHP-FC
(combined heat and power-fuel cell) section the Japanese CHP grew at 20% after Fukushima nuclear crisis [5] and the overall, the stationary FC market value is expected to grow from $1.4 billion in 2013 to $14.3 billion in 2020 and the 24,500 units sold in 2012 is expanded to 1,127,560 units in 2018 with an average annual growth rate of 7.7% [6]. In contrary to this intensified activities in the FC development, high cost and the lack of well-located supply logistic of hydrogen fuel has been the most critical factor stalling off the commercialization of the fuel cell and only becomes interested in the literature [3,7,8]. The market cost of hydrogen is dominated by the 40e75% distribution cost in the compressing, shipping and storage from a large central plant to the various users. The production cost itself is influenced by the scale of production and the choice of process feed. A large central production plant may enjoy lower production cost by
* Corresponding author. E-mail address: [email protected] (M.H. Rei). URL: http://www.toplus-e.com.tw, http://www.toplus-e.com.tw http://dx.doi.org/10.1016/j.ijhydene.2014.08.140 0360-3199/Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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Fig. 1 e Two sets of 4.5 KW FC system modules in Chips Casting Plant.
the lower depreciation and overhead but is to be burden with vast amount of expenses in the distribution and the storage cost of large volume of high pressure hydrogen in the station in road side or in shopping mall. The distributed supply mode, on the other, will use smaller production plant onsite and supply with lower pressure to the operation site without major storage facility; this eliminates the compression, shipping and storage cost without high pressure hydrogen storage. The improvement of production efficiency in small production facility is desirable to provide additional cost saving to the lower distribution cost in the distributed supply mode. We present here our effort and the result of improving the production efficiency of the small scale onsite hydrogen generator to allow lower production cost and safer supply of hydrogen to the users even in the crowded urban site without the concern of the shipping and storage of large volume of high pressure hydrogen in the busy urban area. The cost of hydrogen has been targeted at $2.0-4.0(2007 $) per GGE by US Department of Energy (DOE) for 2015 [9]. To this target, we report here our onsite compact methanol hydrogen generator for the production of primary reformate hydrogen (75%H2), of LoCO hydrogen fuel with 2e4 ppm CO and of 99.995 þ %hydrogen; these different graded hydrogen (H2) has been used as the fuel for fuel cell power generation without difficulty.
Experimental
chips-casting.com) for power and hot water washing of the de-waxed casting molds (Fig. 1). This was a government sponsored FC-DEMO program with online monitored by the government agency. When surplus hydrogen from FC stuck was recovered as fuel in the reformer, each reformer consumed 3.780 kg/h of methanol and RO water of 2.97 kg/h to produce 7.5CMh of hydrogen in the primary reformate; the primary reformate had a composition of 75%H2, 24%CO2 and 1.0%CO. For heating up the reactor for hydrogen production, 0.192 kg/h or 1.200 kg/ h of methanol fuel was used with or without the recovery of vent hydrogen from FC stack, respectively; this corresponds to a process efficiency of 102.3% or 81.6%, respectively. The crude hydrogen was further purified with 900 L/h of air for selective oxidation with a proprietary oxidation catalyst of Co modified Pt/Alumina at 110e120OC to obtain a net 7.5 CMh of LoCOH2 fuel. The reformer took 20 min to reach 250 C reaction temperature and another 10 min to yield stable LoCO H2 fuel with 2e5 ppm of CO. The power efficiency of the FC sacks was 0.8 KWh per 1000 L of hydrogen in the LoCO H2. Throughout this program between Feb 20, 2011 and May, 2011, the total methanol consumption, power output and hot water (25e80 C) were 14,400 kg, 14,765 KWh and 543.6 Ton, respectively, in an accumulated operation hours of 1791 h. The typical IeV curve and power output are shown in Figs. 2 and 3. Throughout the program, the thermal efficiency was 18.5% for power output and a total efficiency of 58.6% including hot water generation. Based on the report of Taiwan Power company, there was 536 gm CO2 emission per KWh of
9 KW fuel cell CHP system in a casting plant for power and hot water A 9 KW fuel cell system was composed of two 7.5 M3/hr (CMh) methanol reformers and two water cooled 4.5 KW FC stack (Toplus Energy Corp., http://toplus-e.com.tw); the hydrogen from the reformer was further purified by selective oxidation of CO (DeCO) with air to 2e4 ppm (70%H2) for direct utilization by FC stack for the power generation. Design and fabrication of this methanol steam reformer for the production of LoCO hydrogen (LoCOH2) fuel for fuel cell power generation has been reported [10]. The power from the fuel cell system and the vent hydrogen were used for a hot water heater in a precision casting plant (Chips Investment Casting Inc., www.
Fig. 2 e IeV curve of power output from 5 KW FC system with methanol reformer.
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Fig. 3 e Time on stream of power output from 5 KW FC system with methanol reformer.
power generation and a 41.64% thermal efficiency; this leads to a 38.8%CO2 reduction in the power generation of 14,765 KWh (1791 h) during the testing period of 1791 h.
5 KW fuel cell CHP system with a natural gas or LPG steam reformers of 8M3/h 5 KW FC CHP system is constituted with a prior-sulfur (<2 ppm) removing reactor, a natural gas (NG) steam reformer (also used for LPG), heat exchanger and CO-purifier with high temperature and low temperature water gas shift reactors followed by two stages DeCO reaction with Comodified Pt/geAl2O3 catalyst (0.8 kg) for CO reducing from 0.6e1.0% to 2e4 ppm. Two stages sulfur removal reactors, DS1 and DS-2 with commercial catalysts of DP-90 (4.1 L) and DP45 (0.9 L) of BASF were used for sulfur removal at room temperature with VHSV ¼ 500h1 and 2300 h1, respectively. The steam reforming reformer was filled with 2.4 kg of combustion catalyst (OXD, a hBN promoted Pt/geAL2O3, or PBN) and 2.8 kg of SRR catalyst (Ce and Ru modified NiO/geAl2O3). The
Fig. 4 e Reactor assembly of the steam reforming of natural gas or LPG.
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Fig. 5 e Block diagram the natural gas (or LPG) steam reforming reaction.
assembly of this NG/LPG reformer system is shown in Figs. 4 and 5. The NG/LPG reformer had multiple columns for preheating and steam reforming in two copper blocks similar to previously reported methanol reformer design; the reactor blocks were inserted into a stainless steel tube (180 mmOD 400 mmL) as the shield; the two copper blocks are for feed pre-heating, PHT, (160 mmOD 100 mmL) and steam reforming reaction,SRR, (160 mmOD 250 mmL). This gives a total reformer volume of 10.184 L (or 1.36L/CMH2) excluding heat exchanger and WGSR (water gas shift reaction). There were four catalytic heating tubes (28 mmID 500 mmL) filled with OXD catalyst at the center section surrounded by multiple columns filled with SRR catalyst in the SRR block (Fig. 6); the reaction temperature was maintained at 730e770OC for reaction as shown in Fig. 7. In addition to the above PHT block for the final stage preheating to 750 C, two additional pre-heaters were used for the first and the second stage preheating of the reactants (NG or LPG and RO water in a 3.5 ratio of H2O/C). As shown in Fig. 3, the 2nd stage HEX was an aluminum block of 250 250 150 mm with multiple columns for heat exchanging of feeds mixture with the hot vent gas streams of two OXD vent streams and the SRR product stream before undergoing water gas shift reaction (WGSR). The crude reformate was set for two staged WGSR to reduce CO; the high temperature (350e450 C) WGSR was 350e450 C while the low temperature reactor was 230e280 C to reduce CO from 13% to 0.8e0.9%. The first stage pre-heater was a tube and shell type heat exchanger with fuels (NG fuel and air) in the tube side while the exit streams of the HEX-2 in the shell side as the heating sources at about 100 C.
Fig. 6 e Cross section of the PHT and SRR blocks.
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condition running for 487.5 days (11,700 h) and has maintained steady state for both hydrogen and CO concentration as shown in Fig. 11.
5 CMh high purity hydrogen generator
Fig. 7 e Steady temperature in NG reformer with catalytic heating.
To start up the reforming reaction, methanol was used as the fuel for the cold start to bring up catalytic bed for the initial period of the reaction, the recovered hydrogen mixture from the fuel cell vent was then used to continue heating up the reactor system. Alternatively, an electric heater is used for the initial heating till 350 C; then natural gas is used either from the supply line or from the recovered natural gas of the fuel cell vent. As shown in Fig. 8, it takes about 44e45 min to reach the stable reaction temperature of 730e750 C. The temperature in PHT, SRR and HEX was found to be 792, 753 and 289 C, respectively; in the SRR section, the temperature distribution from the inlet, 5 cm, 15 cm and 25 cm upward was 729, 750 and 742 C, respectively. Table 1 lists the result of reformate after HTWGS, LTWGS, DeCO1 and DeCO2 processes. This reformer is connected with a 5 KW fuel cell system by Toplus Energy to generate 5 KW power with waste heat being recovered for 400 L/h hot water at 70 C. The thermal efficiency of this steam reformer is 74.8% with NG and 74.6% with LPG and overall efficiency of 30.2% for power and 65.4% including hot water. The IeV curve of the power output is shown in Fig. 9. The assembly and photo of the complete set is shown in Fig. 10.
Life test of hydrogen generator A 2.0 CMh hydrogen generator [10], weighting 19 kg (125 Lit) is used for this long term stability test; the reformer is heated up with 120 gm of PBN combustion catalyst [11] by 330 g/h of methanol fuel and 3000 L/h of air. 960 g/h of methanol feed (H2O/C ¼ 1.4 mol) was fed for the generation of hydrogen in the SRR section containing 800 gm of CuOZnOAl2O3 catalyst. The methanol/water feed was turn down in the evening while the reactor was kept at 260 C continuously since 11/13/2012. Up to now (03.16.2014), it has been kept under reaction
Fig. 8 e SRR temperature change during start up.
This hydrogen generator was composed of a 7.5 CMh methanol reformer and a 5 CMh PSA purifier. The performance of the reformer has been described previously [2]. The PSA was supplied from Beijing GH2 Power (http://www.gh2power.cn). At 260 C and 0.68 MPa, the reformer provided 7.0 CMh of hydrogen in the primary reformate with 75%H2, 24%CO2 and 1.2%CO composition from 4.8 kg/h of methanol in feed (H2O/ C ¼ 1.5) for SRR and 1.43 kg/h of methanol fuel for heating before vent hydrogen from PSA was recovered as the fuel; 5.04 CMh of pure hydrogen were obtained with a pressure of 0.13 MPa and purity of over 99.99997e99.999996%H2 with CO2: 31e110 ppb; CO: 1e26 ppb and TCH:<2e10 ppb by two professional analytical services. The reformer and PSA were housed in a steel plate box of 1040 mm 840 mm 2240 mmH (Fig. 12); the waste hydrogen from PSA was incinerated at this moment and would be used for boiler heating in a 20 KW CHP system for another FC-DEMO program.
Testing results of a 20 KW CHP/FC system in Taiwan A 20 KW CHP/FC system was installed for lighting and swimming pool of the gymnasium complex of National Taiwan University of Science and Technology (NTUST, http:// www.ntust.edu.tw) in Taiwan (Fig. 13); four 4.8 CMh hydrogen generators and four 5 KW FC systems are used to form this 20 KW CHP/FC system. Each hydrogen generator module is composed of a 4.8 CMh PSA unit and a 7.5 CMh methanol reformer with output pressure at 0.68 MPa; the unit has a weight of 400 kg and a total volume of 1,957 L or 407.7 L/CMh. The power and hot water of the FC system was supplied by 4 sets of 5 KW FC system which was composed of 4e5 CMh high purity hydrogen generators described above and 4-sets of 5 KW FC system utilizing high purity hydrogen fuel. Fig. 14 shows a simplified layout of the setting. The material balance of the system is shown in Fig. 15 indicating a 23% thermal efficiency based on the methanol consumption for the power generation, 27 or 50% for the hot water generation with an overall thermal efficiency of 50.2% or 73.2% if waste heat from the FC cell is recovered. This FC cell generates a net 20 KWh of power output from the 17.5 CMh hydrogen input with a power conversion of 38.2% from hydrogen; however, the cell stack does not have waste heat recovery from its power conversion resulting in lower thermal efficiency on the waste heat recovery. Fig. 16 shows the actual power output in response to the power demand of the gymnasium. Nevertheless, this CHP/ FC power system does provide an 18% cost saving and a 29% CO2 reduction from the reduction of electricity and natural gas consumption. With the average methanol price at $360 MT, the power cost is calculated to be $0.366/KWh or lower if equipment costs are reduced in mass production scale, say 20 MW system.
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Table 1 e The results of steam reforming reaction of NG/LPG at 720 C. Feed
NG LPG
VHSV, hr1
6000 4500 6000 4500
Feed, M3/hr
2.26 1.69 0.85 0.63
Fuel, M3/hr
1.21 0.90 0.43 0.33
Composition (%), dry gas H2
CO, ppm
CO2
CH4
70.12 70.31 70.43 70.78
2.6 2.2 2.7 2.1
18.13 18.77 18.25 18.60
0.47 0.39 0.40 0.33
Results and discussion Unique features in the methanol reformers The design of our compact high efficient reformer has been reported before. The uniqueness of this design is the provision of the proper surface area from the multiple columns in PHT (preheater) and SRR sections and allowance of the sufficient solid mass of reformer medium between the channels to ensure sufficient mass for the required heat transfer from the OXD to PHT and SRR sections as described elsewhere [11]. The heat transfer from the catalytic heater relies upon thermal conductance through the reformer medium; therefore, sufficient mass of the medium is to ensure effective heat transfer and storage in the reformer block. This storage of thermal energy in the reformer block enables it to play as a secondary origin for the heat transfer to the individual column of the feed preheating and the steam reforming reaction. As a result, the highly efficient heat transfer in the reactor mass lead to a high overall heat transfer coefficient with an Uvalue in the range of 200e250 W.M-K; it also brings about easy scale up of the reactor because the reactor block plays as a second heat source for the heat transfer to the catalyst beds and avoid the long distance heat transfer in a larger reactor. In comparison, an open fire heater generally requires a well controlled gas flow in the multiple burners and a spacious volume for convection and radiation to reach an even distribution of reaction temperature. The methanol reformers in various capacities have been used in the previous hydrogen generation for HTPEM and LTPEM with LoCO hydrogen fuel and for a 50 CMH onsite industrial plant containing a PSA purifier to 99.995e99.9995% purity of hydrogen as shown in Table 2. Finally, this unique design of having balanced reactor mass and surface area of catalyst columns in the reformer enables us
XCH4 %
H2, CMh
Therm. efficy., %
97.34 97.81 97.80 98.12
8.09 6.00 8.05 6.00
75.2 75.1 75.1 75.6
to fabricate various sized methanol reformers for hydrogen supply units from 2 CMh to 50 CMh for use in 1 KW to 10 KW fuel cell power systems of HTPEM and LTPEM as well as for steel plant with 99.995% purity; we also fabricate onboard methanol reformers of 1.5e8 CMh for use in hydrogen enhanced combustion (HEC) to boost engine efficiency in fuel consumption and in abatement of pollution in exhaust stream [4].
New design of natural gas steam reformer with a catalytic heater The use of reactor mass as a heat conduit for heat transfer is adapted in the newly fabricated 8 CMH NG (also for LPG) reformer. Because of high reaction temperature, the reactor media for heat transfer is made of copper in column-type blocks inside a stainless steel tube. Two copper blocks containing multiple columns for catalysts are used for PHT and for SRR at 720e750 C; both of these two blocks are enclosed in a stainless steel pipe which functions as protection material and also slows down heat loss from the higher temperature inside. Because of much higher requirement of the reaction heat for the NG reforming at 750 C, 192.36 KJ of NG vs. 59.12 kJ for methanol at 250 C, two external heat exchangers made of aluminum alloy and an internal copper PHT are used. The copper PHT block is placed upstream to the SRR block to allow sufficient preheating of the reactants mixture; both PHT and SRR blocks are heated by 4-heating tubes with fuel being preheated in the two external HEX. The catalyst in SRR is a Ce and Ru metal oxides modified nickel catalyst filled up in the multiple columns for the steam reforming of NG or LPG. Methanol or NG as heating fuel is introduced with air in the PHT inlet, SRR is heated by the hot feeds stream from PHT section. The heating gases from the 4-heating tubes are vented out into an aluminum block heat exchanger, HEX-1, akin to the previously published structure; the vent gas of this HEX1 is used to heat up fuel mixture in another HEX-2 before they entered into OXD sections.
Hydrogen purity and its usages
Fig. 9 e Typical IeV curve of 5 KW FC power output using LoCO H2 fuel from NG.
The hydrogen in the primary reformate from either methanol or NG SRR contain 75%e78% of H2, 0.9e1.2%CO and the balance amount of CO2; this type of hydrogen has been successfully used for HTPEM with 3 KW output in 2008 and for HEC in several internal combustion engine tests to upgrade engine efficiency. The hydrogen is further purified by selective oxidation of CO with our proprietary catalyst in two stages oxidation with air at 110e130 C to bring down CO content to 2e5 ppm; the resultant LoCO hydrogen fuel, 70%H2, 2e5 ppm CO and balance amount of CO2 and N2 was directly used for
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Fig. 10 e Assembly and photo of a 5 KW FC power system with a NG reformer of 8 CMH.
Fig. 11 e Life time test for a 2 CMH methanol reformer.
power generation of 5 KW and 9 KW with LTPEM in two FCDEMO programs in 2009 and 2011. At this low level of CO, its poisonous effect on MEA of FC appears to be negligible and yield stable power output [12]. We have compared the power output from LoCO H2 fuel with that of power output using an independent blended 75%H2, 0 ppm of CO and 25%CO2; they are practically identical. The power outputs from these FC systems using a MEA of Pt/Re catalyst system [13] are steady as shown in Figs. 2, 3 and 9. In order to provide high purity hydrogen in the industrial hydrogen market, the primary reformate was purified with PSA to 99.9999 þ %; two cases have been undertaken. One was the assembly of seven 10 CMh methanol reformers with a PSA
purifier for an onsite plant of 50 CMh H2 for the surface treatment of stainless steel wire in Wenchow, China. A new one is developed for the another FC-DEMO program with a 20 KW CHP type power system with LTPEM and hot water supply to a warm water swimming pool of National Taiwan Technology University in Apr of 2014 (Fig. 12); the electricity of this system is used to light the gymnasium while the waste hydrogen from the PSA purifier is burned to provide hot water for the swimming pool. The heat recovery of the cell stack is not installed; as a result, the overall thermal efficiency of this system is regrettably lower. The high purity of hydrogen fuel allows the fuel cell stack to convert into 1.36 KWh per CMh of hydrogen fuel (45.3%); however, it becomes 1.14 KWh/CMh of
Fig. 12 e A 5 CMh high purity hydrogen generator. Please cite this article in press as: Yeh GT, et al., Low cost compact onsite hydrogen generation, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/j.ijhydene.2014.08.140
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Fig. 13 e Photo of 20 KW CHP/FC system in Taiwan.
Fig. 14 e A simplified layout of the 20 KW CHP/FC power system in Taiwan.
hydrogen fuel after internal power consumption of BOP in the hydrogen generator and cell stack resulting in a net power efficiency of only 38.2%. The hydrogen purity of the hydrogen generators is unexpectedly high and can be used for process hydrogen in high technology industries such as semiconductor or photovoltaic industry.
The cost of hydrogen by methanol and by natural gas The cost of hydrogen depends tightly with the choice and the cost of the raw material of the process. In Taiwan and in S.E.
Asia using liquefied NG (LNG) the LNG price is around $15-18/ MMBTU while methanol price follows international price of about $330 to $520/MT in 2012e2014Q2 with an average price of around $360 MT between 2012 and 2014 and falls down to $330 in 2014Q2. If we adapt an average methanol price of $360/ MT and $0.638/CMNG (equivalent to $17/MMBTU), the price of hydrogen in various qualities with a 5 CMh unit is shown in Table 3. The hydrogen cost from methanol is about 86% of that from LNG; this is brought about by a relatively lower temperature and simpler processing condition and can be even
Fig. 15 e Material balance of the 20 KW CHP/FC power system in Taiwan. Please cite this article in press as: Yeh GT, et al., Low cost compact onsite hydrogen generation, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/j.ijhydene.2014.08.140
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Fig. 16 e Power output of 20 KW CHP/FC power system in Taiwan.
lower if methanol price prior to Nov, 2013 to Feb, 2014 surge is used. Even at these hydrogen prices of $4.66 kg at 2014 $ value shown in Table 3, it is lower than those expected from the SRR of NG onsite ($4e5 kg) or offsite ($6e8 kg) in the literatures [14,15], and also much lower than power cost of wind ($8e10/ kg) and solar (via electrolysis, $10e12/kg). Our $4.66 kg is lower than or about the target price of the DOE of US, $2.0e$4.0 (in 2007$) [1]. The relative cost of methanol and NG based hydrogen will be reversed in areas where NG cost is only $4 to $9/MMBTU; the cost of LoCOH2 and 5NH2 in those area would become $0.14($1.12/GGE) and $0.20($1.86/GGE) at $4.0/ MMBTU, respectively. The capital cost of hydrogen generators using methanol is only 45%e75% of those using NG depending on the hydrogen purity. The lower cost for methanol reactor is attributed to higher purity of methanol, simpler process steps and the lower reaction temperature 250 C vs. 750 C demanding more expensive reactor materials, copper and stainless steel vs. aluminum.
The cost of hydrogen by distributed vs. central supply system It clearly shows that hydrogen from distributed onsite production is much lower in cost than one can obtain from hydrogen produced in a central plant and distributed by cylinder bundle or by long tube trailer and accordingly their power cost in a fuel cell system. It is often quoted that a big scale central production plant of hydrogen will be more efficient and much cheaper in production cost [16]; however, with these 5e10 CMh modular system presented here, their efficiency is already at 83e87%, it is higher or equal to a large plant can have [8]. Next the depreciation factor in large plant may have advantage over small scale plant; however, the system presented here is also has fairly reasonably low sharing of depreciation in the total cost. The compression, shipping and storage have always been the major factor of hydrogen price, 45% and 70e75%, respectively, in Taiwan and in the costal part of China. As economy develops, the shipping and storage cost is not necessarily going down unless the costly liquefied hydrogen system is to be enacted. As a result a central supply system of hydrogen will be difficult to become more competitive than a high
efficient distributed supply system. Besides the high cost, the central production distributed by long tube trailer may be too high in supply volume and too bulky in space demand (70 m2 plus drive way) for a road-side hydrogen station or for hydrogen supply to a UPS of a cell phone transmitter in the urban area. Furthermore, the distributed hydrogen supply is a modular setup, the production capacity can easily grow with the market demand without wasting to much investment up front and thus reduces the risk of investment in the early stage of hydrogen energy. Next we notice that the hydrogen made with methanol is much cheaper in the production cost and in its capital expenditure. This phenomena prevails when natural gas is relatively expensive in the area where it is imported by LNG; when LNG is the source of methane, it costs at about US$1517/MMBTU for importation in eastern Asia and an additional $1-2/MMBTU for the storage, gasification and piping to the user while methanol at $360/MT is equivalent to $16.6/ MMBTU in energy content with a much lower distribution cost to be added to the user. Moreover, the production of hydrogen from methanol is much more efficient, lower cost and lower capital demand than it is from using NG as the raw material, Therefore, in contrast to N. America where NG is only $4.0-4.5/ MMBTU, in LNG importing area such as Taiwan, Korea and Japan, methanol will be a better choice as the raw material for producing hydrogen than is from NG, particularly in small to medium scale.
The potential market of using these compact hydrogen generators On the choice of hydrogen fuel for FC power system, if it is a HTPEM, the hydrogen from primary reformate from SRR of methanol will be the best choice as the hydrogen fuel in cost and in process simplicity and in the compact reactor space. For LTPEM, either LoCOH2 or high purity hydrogen from the SRR of methanol can be used depending on how much weight consideration is to be placed on the initial investment, the space or volume of the facility and the start-up time. It takes about 30 min for the LoCOH2 to get ready for the stabilization of CO content and power generation but it will requires about 1 h for the methanol reformer-PSA system to get ready for the hydrogen to reach to H2 with CO <1 ppm and the power generation. The advantage of having higher power efficiency (1.36 KWh/CMh or 45.3%) by using high purity hydrogen fuel would be lost if power efficiency with LoCOH2 fuel can be upgrade to 1 KW per 1 CM of hydrogen fuel. In the past two years, we have worked together with six FC system companies in Taiwan, their power efficiency ranged from 0.7(23.3%) to 1.1(36.7%)KW/CMH2 output; the power cost will drops from $0.501/KWh to $0.417/KWh at 1.1 KW/CMH2. Therefore, there is room for the improvement of power efficiency with LoCOH2 fuel; this will be a good topic for the researcher in this field. Natural gas as the raw material can be competitive against methanol only when NG is shipped by pipeline instead of by liquefaction to LNG. As shown in Table 3, with respect to the raw material of hydrogen fuel of SOFC, the hydrogen in primary reformate from SRR of methanol will be a better choice than from NG as it is common in areas where the cost of NG is much lower than
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Type
H2, SM3/hr CO, HiCO, LoCO Application Reformer Size, mm Reformer weight, kg
GHM-2CMh
GHM-5CMh
2 5 1.2% in reformate, 2e4 ppm in LoCO H2 HTPEM, LTPEM 340 170 200H 240 210 600H 11 63
GHM-7.5CMh
7.5
300 420 700H 75
GHM-50CMh
50 1.2%/in reformate, <1 ppm in 5NH2 HT/LTPEM & Ind. H2 300 420 800H 100
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Table 2 e Various hydrogen generators with basic methanol steam reformers.
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Table 3 e The cost of hydrogen with different purity with methanol ($360/MT) or natural gas ($17/MMBTU) as the feed by the 5 CMh hydrogen generator. 75%H2a
Items c
LoCOH2b
Raw material
MeOH
Capital, US$ Feed/CMH2d, kg or CM/CMH2d Fuel/CMH2, kg or CM/CMH2 H2O/CMH2, kg/CMH2 Elec.,KWh/CMh Dir. Cost, $/CMH2 Indir. coste, $/CMH2 Total cost, $/CMH2 Cost industrial H2, $/kgH2 $/kg or $/GGEf Dir elec. Costg, $/KWh Indir. elec.Costh, $/KWh Total elec. Cost, $/KWh
7500 16,500 10,500 0.48 0.263 0.51 0.14 0.14 0.16 0.32 1.48 0.4 0.04 0.06 0.08 0.227 0.251 0.253 0.030 0.071 0.041 0.257 0.322 0.294 11.20 (by long tube trailer), 18.70 (by cylinder bundle) 2.88 3.61 3.29 0.321 0.402 0.368 0.115 0.115 0.115 0.436 0.517 0.483
a b c d e f g h
NG
MeOH
5NH2 NG
MeOH
NG
19,500 0.28 0.15 1.58 0.12 0.274 0.084 0.358
21,700 0.685 0.19 0.49 0.12 0.331 0.086 0.416
28,900 0.376 0.18 2.12 0.18 0.417 0.125 0.542
4.01 0.447 0.115 0.555
4.66 0.347 0.115 0.462
6.07 0.434 0.115 0.549
75%H2 means hydrogen from primary reformate. LoCO H2 from 70%H2 and 2e4 ppm CO. MeOH stands for methanol. kg or CM of methanol or NG, respectively per CM of H2. Based on 7-yr depreciation and 3% maintenance of capital. 1 kg H2 ¼ 11.2 CMH2. Power efficiency of 1 CMh hydrogen of generates net 0.8 KWh of power by 75% H2 or LoCOH2 and1.2 KW of power by 4NH2. Based on 7-yr depreciation and 3% maintenance of capital cost of $26,700 for a 5 KW FC unit.
in LNG area, the advantage of using hydrogen from SRR of methanol comes not only in the hydrogen cost but also in the simplicity of process from the cleaner feed (sulfur cleaning), the low reaction temperature (250 vs. 800 C) and more significantly, in the lower energy requirement of methanol SRR than that of SRR of NG (2790 vs. 6760 KJ/CMH2). With methanol SRR based SOFC, the high conversion temperature and the energy content from the stack can be effectively passed on for the endothermic process of methanol SRR with surplus heat for other heat recovery. This is more so in the case of small to medium sized SOFC where not only cost advantage can be realized but also the compactness to allow the penetration of SOFC into CHP power supply system of average household or building. The partial testing results of the 20 KW CHP/FC system in Taiwan shows that it can have a power cost of $0.366/KWh if methanol is valued at $360 MT; this power cost can be reduced further if more rigorous recovery of waste heat from FC-stack is installed (about 23% more heat recovery) and it is in a larger system, say 20 MW, through lowering of capital investment (around 40% reduction). With an accumulated active operation time of 250 h up to Aug 5th (9am to 6pm active supply of power and hot water and 6pm to 9am in standby status at 200e230 C), it has demonstrated a capability of weather-proof stability (2-hurricans invasions) flexibility of power adjustment and the relative economic advantage in comparison with Diesel power system in the off-island of Taiwan, if not with the main grid system in the main island of Taiwan. Such a FC power system in the off-island or remote area where a sophisticated power grid system is expensive to install will not only provide saving in the power cost and stability in the power supply but also will provide additional advantage in the hot water supply for household usage or for the desalination of brine water or as a supplemental power stabilizer to wind or
solar power whose power supply is subjected to weather interference.
Conclusion Low cost compact reformers have been successfully developed to produce stable and durable hydrogen fuel for fuel cell power generation. These onsite hydrogen generators are highly efficient in producing low cost hydrogen at the user site eliminating the expensive distribution cost and avoiding storage of large volume high pressure hydrogen; the product hydrogen can be used as direct fuel for HTPEM or purified as LoCO H2 fuel or as high purity hydrogen for LTPAEM or for industrial hydrogen utilities. The LoCOH2 can be used as a direct fuel for LTPEM system provided that the catalyst in MEA is modified with Pt/Re to resist potential CO poisonous effect. A FC system using LoCOH2 fuel provides a compact and low capital cost option as compared with that using high purity hydrogen. These low cost hydrogen form the compact onsite reformers can help overcome the hurdle of hydrogen supply to the hydrogen stations or UPS station in the urban area. Their cost of hydrogen and power can be obtained at $2.73/GGE and $0.35e0.40/KWh with methanol at $360/MT ($16.6/MMBTU). Using$16.6MMBTU for both methanol and NG, the hydrogen and power from using methanol as the starting material is lower than from NG as the starting material; this is critical in the LNG import area for the proper selection of raw material to produce hydrogen. The 20 KW CHP/FC power system in Taiwan demonstrates that FC power can have a stable power supply capability of flexibility, weather-proof and low cost in comparison with Diesel power and can be a supplemental power to the
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conventional renewable power of wind and solar energy. In the early stage it can be developed as a competitive distributed power system in the off-island or remote area where central power grid is not well developed.
references
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[8] Fuel Cell Technology Office. Hydrogen production in multiyear. Res Dev Demo 2012. http://energy.gov/eere/fuelcells/. [9] US DOE. Progress report for the DOE hydrogen and fuel cells program. Chapter III-3. December 2013. DOE/GO-1020134260. [10] Wang Harvey HF, Chen SC, Yang SY, Yeh GT, Rei MH. Design of compact methanol reformer for hydrogen with low CO for the fuel cell power generation. Int J Hydrogen Energy 2012;37:7487e96. [11] Tsai Yihsiu, Wang Harvey HF, Yeh Guan-Ting, Rei MH. hBoron nitride as a promoter for reactive and stable combustion catalyst. [submitted for publication]. [12] Bhatia KK, Wang C-Y. Transient carbon monoxide poisoning of polymer electrolyte fuel cell operating on diluted hydrogen feed. Electrochem Acta 2004;49:2333e41. [13] Wang Deli, Subban Chinmayee V, Wang Hongsen, Rus Eric, ~ a Hector D. Highly stable and CODiSalvo Francis J, Abrun tolerant Pt/Ti0.7W0.3O2 electrocatalyst for proton exchange membrane fuel cells. J Am Chem Soc 2010;132:10218e20. [14] The National Academies. The hydrogen economy. Washington, D.C. USA: The National Academies Press; 2004 [Chapter 4], http://www.nap.edu. [15] Ramsden T, Steward D, Zuboy J. Analyzing the levelized cost of centralized and distributed hydrogen production using the H2A production model, version 2. Technical Report, NREL/ TP-560-46267. September 2009. [16] IEA Energy Technology Essentials. Hydrogen production and distribution. www.iea.org/Textbase/techno/essentials.htm.
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