| Summary: | 碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 98 === This work aims at investigating the performance of a modified metal hydride (MH) reactor for hydrogen absorption and desorption. The main difference between the previous the present (modified) reactor is that another hydrogen pathway is installed inside the reactor. As such, the hydrogen gas can flow into or out of the reactor via two inlets/exits, one at the front and the other one at rear. Aside from this, the designs of the previous and the present reactors are essentially the same. Both are heated by air.
First, the Mg2Ni powder, which has been activated and tested before, was taken out of the previous reactor. Only 3.2 kg of Mg2Ni powder, about two thirds of the original quantity, can be recovered since part of the alloy powder is attached to the inner wall of the reactor. Then the modified reactor filled with 3.2 kg of Mg2Ni powder was tested and it was found that the hydrogen absorption/desorption rates increase significantly. Specifically, the rates of absorption and desorption are 30 minutes and 100 minutes faster than the previous reactor, respectively.
Next, Mg90Ni10+5%Zn alloy powder was poured into the modified reactor. Owing to high malleability, the Mg90Ni10+5%Zn alloy is hard to pulverize. The alloy powder after sifting looks like tiny pins. The reactor can be filled with 1.5 kg of the Mg90Ni10+5%Zn alloy powder only due to low density and high porosity of the MH bed. Activation was performed for 6 cycles, the hydrogen gas absorbed can reach 31 to 33 moles (4.0 to 4.25 wt %), corresponding to 60 % of the theoretical value (52.9 moles, 6.64 wt %) approximately. The experimental data agree well with the PCI results.
Absorption/desorption experiments were then conducted. The results indicate that it takes 60 minutes to reach a maximum value (32 moles) for hydrogen absorption and 30 to 40 minutes to reach 80 to 90 % of the maximum value at charging pressures of 26 and 36 bars, and heating temperatures of 300 and 350℃. As for hydrogen desorption, it takes 30 minutes to discharge 80 to 90 % of the hydrogen absorbed and 50 minutes to discharge the hydrogen completely. This study points out the need for using dual inlets/exits for a long MH reactor.
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