A gas cyclone, because of its simple design, robustness, cost efficiency and low maintenance requirements is still a preferred choice of dust separation. Due to constantly increasing requirements responding to environmental awareness, the classic gas cyclone has lost some market share as an end of pipe solution chosen for filter and scrubber technologies. Nevertheless, in closed process loops the gas cyclone is still without competition. The last significant improvements in gas cyclone technology were made between the 1950s and 1970s. These improvements were based on the theoretical models of W. Barth and E. Muschelknautz. Since that time scientists have made optimisation work by using computer modelling methods still based on the same theory of W. Barth and E. Muschelknautz. In a departure from the classic cyclone geometry this doctorate thesis describes a new gas cyclone, which is defined by a coarse and a fine dust separation zone. In addition new methods are described to keep the boundary layer flow along the vortex finder largely free of dust. In comparison to a classic cyclone this gas cyclone, characterised by a centre pipe in the axis of the cyclone, a slim and rectangular gas entrance port and a shortened cone, is providing significant improvements in performance with respect to dust separation efficiency, accuracy of cut point and pressure loss.