To enable a catalyst to be exchanged not by cutting a weld zone without complicating the structure of a body upper part plenum.
In a steam reformer having a reaction tube outer pipe 11 arranged to make the axial line vertical and having an opened upper part and a closed lower part in a vessel which is provided with a detachable upper cap 3 at the upper part and the inside of which is partitioned into the body upper part plenum, a body center part plenum and a body lower part plenum with an upper tube plate 6 and a lower tube plate 15, a reaction tube inner pipe 12 internally mounted coaxially to the reaction tube outer pipe 11 and a catalyst 13 filled between the inner circumferential surface of the reaction tube and the outer circumferential surface of the reaction tube inner pipe, the reaction tube outer pipe 11 is extended to the upper tube plate 16 and is opened to the body upper part plenum 18 and the reaction tube inner pipe 12 penetrates through the reaction tube outer pipe 11 below the upper tube plate 6 and is opened to the body center part plenum 17.
KODAMA YUTAKA
KARASUTANI HISASHI
