Off-gas cleaning apparatus and filter exchanging method

A blocking plate is disposed for closing a lower opening of a filter case upon suspending a filter together with the filter case by a crane or the like. Further, a containing plate for fillers and is secured to the filter case and disposed in a falling region of the fillers. Thus, if the fillers in the filter case fall, they remain on the filter bottom plate and the blocking plate or the containing plate and are not leaked out of the casing. Further, annular protrusions are disposed to the secured face of the filter bottom plate or the packing for surrounding the opening, while recesses corresponding to the protrusions are formed to the other securing surface, so as to improve the sealing function. In addition, the opening/closing cap of the filter container is made as a closed flange and clamped with nuts and bolts, which reduces failures and make the maintenance easier as compared with hydraulic devices. (T.M.)