II-9. Instrumentation

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Experiment on hydrogen removal apparatus for helium supply andrecovery system
M. Nakamura,∗1 T. Dantsuka,∗1 and H. Okuno∗1
In the past, the liquid-helium supply and recovery
system of the Wako campus have suﬀered severe damages from hydrogen impurities in the system.1) To remove this hydrogen from the recovered helium gas, wedeveloped hydrogen removal methods utilized for oursystem. We found that the silver-zeolite “Ag400” madeby “Molecular Products Inc.” can be used as the adsorbent, and the applicability of Ag400 for hydrogen
removal was conﬁrmed.2) At that time, we did not install the hydrogen removal apparatus earnestly in oursystem. However, a new liquid-helium supply system
was constructed and operated from 2017 because of
the deterioration of the old system.3) In this system,
the newly established hydrogen removal apparatus wasinstalled beforehand. In this study, we examined theamount of hydrogen that can be adsorbed by Ag400,
which had not been minutely evaluated until now.
The experimental setup consists of a hydrogen tank,a pressure gauge, a buﬀer tank, three switch valves, areaction tank, a data logger, and a vacuum pump. The
volume of the buﬀer tank is approximately 550 cc, andthat of the reaction cylinder is approximately 18 cc.
These parts are connected as shown in Fig. 1.
The experiment is performed by the following threesteps. i) Approximately 20 g of Ag400 is ﬁlled in thereaction cylinder. Valve 1 is closed and the whole setup
are evacuated. ii) Valve 2 is closed, the valve 1 is released and hydrogen gas is ﬁlled to the buﬀer tank;its pressure reaches 0.4 MPaG. iii) Valves 1 and 3 areclosed and valve 2 is released. Hydrogen gas is supplied to the reaction cylinder and adsorption begins.
The change of the pressure of the buﬀer tank is monitored by the pressure gauge and recorded by the datalogger.

Fig. 2. Change of hydrogen pressure in the buﬀer tank.

The result of this experiment is shown in Fig. 2.
From this ﬁgure, it can be observed that the hydrogen pressure in the buﬀer tank reduced rapidly from0.4 MPaG to 0.34 MPaG in approximately 30 min after the start of the adsorption reaction. After 12 h, thepressure slowly reduced to 0.32 MPaG. Finally, the hydrogen pressure reduced to approximately 0.31 MPaG
and settled at the equilibrium state. This result showsthat 20 g of Ag400 can adsorb approximately 500 scc
of hydrogen gas throughout the experimental process.
We use approximately 4 kg of Ag400 in the hydrogen
removal apparatus in the liquid helium supply and recovery system. Hence, approximately 0.10 Nm3 of hydrogen impurity gas can be removed by this apparatus.
Usually, the concentration of hydrogen contained in recovered helium gas ranges from 0.05 ppm to 1.5 ppm
in our system. Therefore, supposing that the recovered
helium gas contains 0.1 ppm of hydrogen, our apparatus can purify approximately 1000,000 Nm3 of recovered helium gas. However, the total volumes of liquid
helium supplied in one year in Wako campus were from
180,000 L to 200,000 L.3) When all this liquid helium isvaporized, approximately 135,000 Nm3 to 150,000 Nm3of helium gas is generated. In this case, we will evaluate that 4 kg of Ag400 can be used approximately 6–7
years for hydrogen removal.
In the next steps, we will evaluate other characteristics of hydrogen removal apparatus containing Ag400.
References

1) K. Ikegami et al., RIKEN Accel. Prog. Rep. 38, 286 (2005).
2) M. Nakamura et al., RIKEN Accel. Prog. Rep. 41, 111(2008).
3) T. Dantsuka et al., RIKEN Accel. Prog. Rep. 53, 221(2019).

Fig. 1. Experimental setup.
∗1

RIKEN Nishina Center- 118 -1