Double-walled reformer tubes using high-temperature thermal storage of molten-salt/MgO composite for solar cavity-type reformer

摘要

Composite materials with alkali carbonate and magnesia have been examined for high-temperature thermal storage in solar tubular reformers. The concept of a double-walled reactor tube involves packing a molten-salt/ceramic composite material into the annular region between internal catalyst tube and exterior solar-absorber wall. In this paper, the shape and interior structure of the reactor tube are newly designed for use in solar cavity-type reformers using straight reactor tubes. Na_2CO_3, K_2CO_3, and Li_2CO_3 composite materials with magnesia were tested as thermal storage media for CO_2 reforming of methane during cooling mode of the reactor tube at a laboratory scale. The efficiency of Na_2CO_3/MgO composite with various MgO contents was also estimated. Composite materials of Na_2CO_3 80-90 wt% and MgO 20-10 wt% were successfully delayed the cooling of the catalyst bed and sustained methane conversion at >90%. A solar cavity-type reformer consisting of multiple straight reactor tubes is expected to enable stable operation of the solar reforming process under fluctuating solar insolation during cloud passage.