Cyclone separator having water-steam cooled walls

A cyclone separator comprising an inner cylinder, an outer cylinder extending around said inner cylinder in a coaxial relationship to define an annular chamber between the two cylinders, said outer cylinder comprising a plurality of tubes extending vertically and circumferentially in a parallel relationship for at least a portion of their lengths, a first ring header connected to the upper ends of said tubes and a second ring header connected to the lower ends of said tubes for circulating a cooling fluid through said outer cylinder, means for directing gases containing solid particles through said annular chamber for separating the solid particles form said gases by centrifugal forces, the separated gases exiting through said inner cylinder and the separated solids falling to the bottom of said outer cylinder for disposal or recycle, the upper end portions of said tubes being bent radially inwardly towards said inner cylinder and radially outwardly to form a roof for said annular chamber, and means for passing water or steam or a steam and water mixture through said ring headers and said tubes to cool said outer cylinder.