Abstract: A roll-type electrical precipitator comprising a housing having gas inlet and outlet means, and strip-like corona discharge and collecting electrodes. The electrodes are wound as spirals about mandrels and have their end portions shaped so as to form an Archimedean spiral having a pitch equal to two electrode spacings. The electrodes are wound about a common axis, their mandrels are displaced with respect to each other by 180.degree., and the turns of one of the electrodes alternates in cross-section with the turns of the other electrode. Each of the electrodes is provided with holes for spacers to be passed through and fixed to the adjacent turns of the other electrodes so as to form a rigid connection between the turns of each of the electrodes.

Abstract: A roof in which beams-headers rest on a roof ring and carry loop-shaped tubes suspended from and coupled with the said beams-headers which are running transversely to the framework tubes. Welded edgewisely to the top generatrices of the tubes are metal straps with bricks placed at least in one layer in rows therebetween. The brick end portions rest on the adjacent tubes, so that the brick in each row are disposed with a clearance sufficient to enable thermal expansion of the brick both vertically and horizontally when heated.