Development of a Hydrogen Vaporizing and Cryogenic Air Separation System in WE-NET Program

Y. WATANABE*1, A. MIYAMOTO*2, H. TANIGUCHI*3 and T. TSUKAGOSHI*4
*1 Kobe Steel, Ltd., Nissei Higobashi Bldg., 6-14, 1-Chome, Edobori, Nishi-Ku, Osaka-Shi, Osaka 550-0002 Japan, (Fax.) +81-6-444-7685 (e-mail) yuki.watanabe@engnet. kobelco. co.jp
*2 Daido Hoxan Inc., 6-40, Chikko Shinmachi 2-cho, Sakai-Shi, Osaka 592-8331 Japan (Fax.) +81-722-44-8414 (e-mail) miyamoto-ats@spk1.dhi.co.jp
*3 Hokkaido Gakuen University, Nishi 11-Chome, Minami 26-Jo, Chuo-Ku, Sapporo-Shi, Hokkaido 064-0926 Japan, (Fax.)+ 81-11-551-2951
*4 Japan Power Engineering and Inspection Corporation, Business Court Shin-Urayasu Bldg., 9-2, Mihama 1-Chome, Urayasu-Shi, Chiba 279-0011 Japan, (Fax.) +81-47-380-855, (e-mail) net.japeic@pep.ne. jp

KEYWORDS: Liquid Hydrogen, Cryogenic Air Separation, Hydrogen Combustion Turbine, Para-ortho Hydrogen, Brazed Aluminum Heat Exchanger, WE-NET

INTRODUCTION

The hydrogen vaporizing and cryogenic air separation system for the 500MW hydrogen combustion turbine power generation plant is being developed in the World Energy Net Work (WE-NET) Program under a contract with New Energy and Industrial Technology Development Organization (NEDO) since 1993.

EXPERIMENTAL

1. Explanation of the whole flow Fig. 1 is the whole flow diagram showing that both hydrogen and oxygen are supplied to two 500MW plants, in which the supply amount of hydrogen and oxygen to the plants are 21.2 ton/h and 169 ton/h respectively. Each supply pressure is rather high, i.e., 6MPa. Oxygen Producing Units apply a cryogenic air separation method, by which oxygen and hydrogen are supplied to each of the plants from the two same-scale oxygen producing units. The oxygen amount produced per one unit is 84.5 ton/h (59,000 Nm3/h). When the Oxygen Producing Unit is shutdown due to some trouble of the plant, liquid hydrogen and liquid oxygen are gasified with evaporators and then supplied to the 500MW plant.

Fig. 1 Flow Diagram of Hydrogen-Oxygen Supply System

2. Explanation of Process for the Oxygen Process

Fig. 2 shows an Air Separation Unit using cold energy of LH2, of which process can decrease power primary unit cost largely. LH2 is supplied at 6MPa in pressure from outside the system and the cold energy of LH2 is utilized to produce LN2 for reflux at the top of the distillation column as the first stage and to cool feed air by various heat exchangers. Different cold energy generated when shifting with Para/Ortho conversion cat-alyst of H2 is also utilized. So it is a process that uses LH2 cryogenic thermal energy in the extremely low temperature range to the full. This process saves power consumption by compressing feed air at low temperature and compensates the generated compression heat of the feed air with the cold energy of LH2. Oxygen is taken out of a distillation column as liquid and the re-moved oxygen is pressurized to 6MPa by liquefied gas pump(s) and then recovered the cryogenic thermal energy.

Fig. 2 Process Diagram of ASU

3. The System Recovering the Cold Energy of LH2

Fig.3 is a system to recover the cold energy of liquid hydrogen and to condense top gas (=nitrogen) from the distillation column. The condensers shown in the figure are Brazed Aluminum Heat Exchangers, which enable easy heat exchange of multi fluids at low temperature. At Condenser 2, vaporized hydrogen is used to prevent the solidification of the top gas by liquid hydrogen. The system is applied for a patent.

Fig.3 Hydrogen Cold Energy Recovery and Top Gas Condenser System

CONCLUSION

The conceptual design of the hydrogen vaporizing and cryogenic oxygen production system in WE-NET Program is completed and the specifications of the equipment are studied. The power consumption of the system is reduced to 0.285KW/Nm3O2 by using the cold energy of hydrogen. The pilot plant test is required to prove the system in future.

REFERENCES

1. M. Murase, R&D Plans for WE-NET (World Energy Network) IHCE '95
2. NEDO, JAPEIC 1997 WE-NET SUBTASK REPORT (NEDO-WE-NET 9784)
3. T. Tsukagoshi, K. Mouri, T. Hisamatsu and M. Watanabe, Research and Development of Hydrogen Combustion Turbine System in World Energy Network Project in Japan, 12th World Hydrogen Energy Conference, Argentina, June 1998.