NOVELTY - The container has filling sections (62,63) that are arranged at upper and lower sides along flow direction of source gas. Source gas circulated from bottom and interlayer of filling sections is separated by a partition plate (64). The condition of impurity and use status of an absorber unit are detected by a detection unit that is arranged between the filling sections. The absorber unit inside the downstream filling section is moved to inner side of the upstream filling section by removing the partition plate, after performing the operation for preset period.    USE - Fixed bed reaction container of absorber for removing impurity from source gas used during manufacture of fuel gas for use in fuel cell (all claimed). Can also be used during manufacture of fuel gas for gas engine.    ADVANTAGE - The usage ratio of the absorber can be increased while suppressing the wastage and replacement of absorber components, based on level of purity at the exit side of the fixed bed reaction container.    DETAILED DESCRIPTION - The impregnated charcoal and copper are used by copper absorber that absorbs mercury by absorbing salt produced by a chemical reaction with mercury. Halide or sulfide is absorbed by a halide absorber. Gasified fossil fuel, biomass and waste material are used as source gas. Fuel gas is purified after absorbing impurity, for using as fuel gas of high-temperature fuel cell. An INDEPENDENT CLAIM is included for filling method of absorber, which involves matching the flow-rate conditions of simulation gas with flow-rate conditions of source gas while filling several layers independent along flow direction of source gas. The length of layer of flow direction of source gas at the downstream side is preset with respect to the length of layer of flow direction of simulation gas, after absorption of impurity.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view illustrating the structure of fixed bed reaction container.    Gas extraction unit (51)    Gas-analysis unit (52)    Outlet gas extraction unit (53)    Filling sections (62,63)    Partition plate (64)