An apparatus and a method for cleaning a stream. The apparatus having at least one hot filtration device, which includes a filter vessel and at least one filter candle located inside the filter vessel, an inlet of medium in an upper part of the filter vessel for supplying the medium including particles to the filter vessel, an outlet of the medium in the bottom part for discharged the medium from the filter vessel, a moving bed including the medium which is arranged in the vessel so that the filter candle is inside the moving bed, at least one feed inlet for supplying the stream to the filter vessel, and at least one gas outlet for supplying a purified gas out from the filter vessel.