316
Water for Energy and Fuel Production
construction materials, (2) inexpensive chemical agents, (3) minimal solids handling,
and (4) reactions going to completion with few side reactions. It is well suited for energy
supplied by the nuclear reactor. The important five steps in Cu–Cl cycle are as follows
[91,104,107]:
Step 1: HCl production step
2CuCl 2 (s) + H 2 O(g) → CuO* CuCl 2 (s) + 2HCl(g)
400°C
(11.45)
Step 2: Oxygen production step
1
CuO* CuCl 2 (s) → 2CuCl(l) + O
2
2 (g)
500°C
(11.46)
Step 3: Electrochemical process
2CuCl(s) → 2CuCl(aq) → CuCl 2 (aq) + Cu(s)
Ambient
(11.47)
Step 4: Flash drying
CuCl 2 (aq) → CuCl 2 (s)
> 100°C
(11.48)
Step 5: Hydrogen production
2Cu(s) + 2HCl(g) → 2CuCl(l) + H 2 (g)
430 − 475°C
(11.49)
This cycle is unusual in that it contains five chemical steps, although efforts have
been made to reduce the number of chemical steps. Just like S–I cycle, Cu–Cl cycle
has a significant potential due to lower temperature requirements. The literature has
shown that the cost of hydrogen production by Cu–Cl cycle is better than electrolysis
method at higher hydrogen production capacity (>30 tons per day) [91,104,107].
11.4.1.10 Copper–sulfate Cycle
The copper/sulfate cycle involves two major steps: (1) hydrogen production from the
reaction of water, SO 2 (g), and CuO(s) at room temperature and (2) the thermal decomposition of the products of the first step to form oxygen and to regenerate reagents for
the first step [91,97–103]. The first step is performed electrolytically and the second
step appears to be possible at a temperature of around 850°C. More complex versions
of the copper/sulfate cycle called H-5 and H-7 involve four and six reactions. Law
et al. [97–105] have given a very detailed accounting of this thermochemical cycle.
Brown et al. [90] examined efficiency of more than 100 thermocycles that can use
high-temperature heat from advanced nuclear power stations. A basic requirement
was the ability to deliver heat to the process interface heat exchanger at temperatures up to 900°C. They also developed a set of requirements and criteria considering design, safety, operational, economic, and development issues. Helium-cooled
nuclear reactor was chosen to interface with the thermochemical cycles. The best
two-, three-, and four-step cycles with the greatest commercial potential identified
from their analysis are illustrated in Table 11.1 [92,140]. They also concluded that
Water for Energy and Fuel Production
construction materials, (2) inexpensive chemical agents, (3) minimal solids handling,
and (4) reactions going to completion with few side reactions. It is well suited for energy
supplied by the nuclear reactor. The important five steps in Cu–Cl cycle are as follows
[91,104,107]:
Step 1: HCl production step
2CuCl 2 (s) + H 2 O(g) → CuO* CuCl 2 (s) + 2HCl(g)
400°C
(11.45)
Step 2: Oxygen production step
1
CuO* CuCl 2 (s) → 2CuCl(l) + O
2
2 (g)
500°C
(11.46)
Step 3: Electrochemical process
2CuCl(s) → 2CuCl(aq) → CuCl 2 (aq) + Cu(s)
Ambient
(11.47)
Step 4: Flash drying
CuCl 2 (aq) → CuCl 2 (s)
> 100°C
(11.48)
Step 5: Hydrogen production
2Cu(s) + 2HCl(g) → 2CuCl(l) + H 2 (g)
430 − 475°C
(11.49)
This cycle is unusual in that it contains five chemical steps, although efforts have
been made to reduce the number of chemical steps. Just like S–I cycle, Cu–Cl cycle
has a significant potential due to lower temperature requirements. The literature has
shown that the cost of hydrogen production by Cu–Cl cycle is better than electrolysis
method at higher hydrogen production capacity (>30 tons per day) [91,104,107].
11.4.1.10 Copper–sulfate Cycle
The copper/sulfate cycle involves two major steps: (1) hydrogen production from the
reaction of water, SO 2 (g), and CuO(s) at room temperature and (2) the thermal decomposition of the products of the first step to form oxygen and to regenerate reagents for
the first step [91,97–103]. The first step is performed electrolytically and the second
step appears to be possible at a temperature of around 850°C. More complex versions
of the copper/sulfate cycle called H-5 and H-7 involve four and six reactions. Law
et al. [97–105] have given a very detailed accounting of this thermochemical cycle.
Brown et al. [90] examined efficiency of more than 100 thermocycles that can use
high-temperature heat from advanced nuclear power stations. A basic requirement
was the ability to deliver heat to the process interface heat exchanger at temperatures up to 900°C. They also developed a set of requirements and criteria considering design, safety, operational, economic, and development issues. Helium-cooled
nuclear reactor was chosen to interface with the thermochemical cycles. The best
two-, three-, and four-step cycles with the greatest commercial potential identified
from their analysis are illustrated in Table 11.1 [92,140]. They also concluded that