The total hydrogen produced by the DFC300 and Water Gas Shift (WGS) reactor is estimated to be 138.72 kg/day.
2. Current Scenario and Future Prospect
A major part of the current hydrogen market includes ammonia synthesis, methanol synthesis, and petroleum refining. Praxair, the major controller of the hydrogen market in North America, boasts application in all the above mentioned areas as well as fueling aircrafts, welding application, food-oil hydrogenation, manufacturing sorbitol, and semiconductor production.
Hydrogen is used in fuel cells to produce power for both residential and vehicular applications. In addition giant corporations such as Walmart, Google, Microsoft® all have installed some sort of fuel cells to power their buildings within the past five years which would require a regular supply of hydrogen. On the other hand Honda, Nissan, and Mercedez have declared huge improvements in their Fuel Cell Electric Vehicle’s (FCEV). The FCEV market has a tremendous potential for growth until the year 2050 and display a sustained demand thereafter, based on a S-curve reported by National Academy of Sciences in 2004 .
Hydrogen storage and distribution has been one of the major bottle-neck for this technology. Based on a recent DOE report, it has been identified that hydrogen distribution through hydrogen fueling station is determined to be the most suitable application for the required rate of hydrogen [2, 3]. The various modes of storage (compressed, liquefied, and cryogenic ) and transport (tube trucks, rail, and pipelines) have been extensively researched. Hydrogen production rates and distance to be transported are major factors that figure the transportation cost [1-3].
The hydrogen generated by the DFC 300 is strategically between the current fueling capacity of most HFS’s ranges from 12 – 20 kg / day and the calculated optimum capacity at 100 – 200 kg / day. A fueling station with this capacity is estimated to fuel around 3000 Fuel Cell Vehicles. For small scale hydrogen production less than 500 kg / day and distances less than 200 miles, the ideal mode of transportation was via tube trucks which can carry hydrogen upto 558 kg at a medium compression of 250 bar for a single delivery [3, 4].
Currently the only hydrogen fueling station in Ohio is in Ohio State University (OSU) campus, at 930 Kinnear Road at Columbus Ohio. The demand for hydrogen and fueling capacity of this station is met by Praxair hydrogen generation facility at Whiting, Indiana about 350 miles from the station, which is twice the distance for efficiently transporting compressed hydrogen. Hence with the hydrogen produced from the DFC-300 is proposed to supplement the hydrogen fueling station at OSU.
3. Process Description
The application process and its specifications are described in Figure 1 and Table 1 respectively.
Figure 1. Process flow diagram for hydrogen exhaust from DFC300 post purification
Table 1. Equipment costs and specifications
Hydrogen at a flow rate of 5.78 kg/ hr is allowed to enter a buffer tank to stabilize the flow rate. A two stage diaphragm compressor rated at is used to compress the hydrogen from 1 bar to 350 bar. The hydrogen flow-rate required by the compressor is maintained at 5.8 kg / hr .
|Figure 2. Two stage hydrogen compressor as sold by PDC .|
Gaseous hydrogen will be compressed to 5000 psi (350 bar) using a two-stage compressor, including an initial booster compressor as shown in Figure 2. In addition to the low compression cost at 5000 psi (350 bar), hydrogen behaves as an ideal gas and can be conveniently be transported by trucks.
Tubular trailer trucks from Praxair would be scheduled to pick up 555 kg of hydrogen from the facility every 4 days as these trucks are designed to carry a useable loading capacity of 558 kg of hydrogen at 250 bar as shown in Table 8 . Therefore the storage capacity at the production site was designed to store additional 3 days’ worth of hydrogen, an additional 33%. The hydrogen was stored at 350 bar in Type IV composite tanks as shown in figure .
Figure 3. Schematic of Hydrogen Tanks Purchased from Quantum Technologies
Major suppliers of hydrogen storage tanks in the U.S. are Structural Composites Inc., Quantum Technologies, Dynetek and Lincon Composites. The hydrogen storage tanks will be purchased from Quantum Technologies as they were able to meet custom design specifications.
The equipment and operating costs were calculated by HDSAM version V 2.0 . This software has come to be a standard for estimating and optimizing the cost of storing and delivering hydrogen for different scenarios. The capital costs and specifications for the equipment are shown in Table 1. The cost of hydrogen is reported to be sold at 9.60 $ kg-1 based on the cost of compression, storage, and distribution, bringing in a revenue of 486074.90 $ year-1, assuming 365 days of operation.
Compressed GH2 Trucks
|Tube Water Volume (m3)||8.5|
|Tube maximum pressure (atm)||250|
|Tube minimum pressure (atm)||15|
|Tube operating temperature (degrees C)||25|
|H2 Capacity (kg)/ tube||173.7|
|Number of Tubes/ trailer||4|
|H2 Trailer Capacity (kg)||695|
|Truck Yearly Availability (%)||98%|
|Total truck Capital cost ($)||570,000|
|Cab Cost ($)||75,000|
Table 2. Assumptions for Tube trailer tractor.
 M. Mintz, J. Gillette, A. Elgowainy, M. Paster, M. Ringer, D. Brown, J. Li, Trb, Hydrogen delivery scenario analysis model for hydrogen distribution options, in: Energy and Environmental Concerns 2006: Including 2006 Thomas B. Deen Distinguished Lecture, Natl Acad Sci, Washington, 2006, pp. 114-120.
 T.Q. Hua, R.K. Ahluwalia, J.K. Peng, M. Kromer, S. Lasher, K. McKenney, K. Law, J. Sinha, Int. J. Hydrog. Energy, 36 (2011) 3037-3049.
 M. Mintz, A. Elgowainy, M. Gardiner, Transp. Res. Record, (2009) 46-54.
 V. Mohan, A. Shah, J.W. Sheffield, K.B. Martin, Int. J. Hydrog. Energy, 37 (2012) 1214-1219.