A device for removing slag from a coal gasification or synthesis gas production process and a slag water bath is enclosed by the reaction vessel The slag is discharged by means of a lock-type transfer vessel arranged located downstream of the slag bath. A vessel includes an upper and a lower cylindrical section, the upper cylindrical section having a diameter larger than that of the lower cylindrical section and both sections are connected by a tapered section which preferably is conical in shape, the angle of the cone being similar to that of the angle of repose of the slag. A process for removing slag from a coal gasification reactor the process including a discharge of slag from the coal gasification reactor to a transfer vessel which precludes formation of slag incrustations in the transfer vessel is also defined.