In process plants like e.g. coal gasification plants, highly dust containing and dust laden gases are generated with pressures of e.g. 100-350 bar and temperatures in the range of e.g. 750.degree.. These gases are expanded via valves and released into collecting containers for further use e.g. as process gas for boiler firing or as synthesis gas for chemical processes.
Valves are known provided with a parabolic valve body which cooperates with a valve seat in the shape of a screen and whose lift is adjustable to regulate the flow rate of the gas through the valve. It has been shown in practice, however, that due to erosion, the dust particles contained in the gas and accelerated to considerable velocities cause considerable damages of the closing elements and control elements of such a valve and partly also of the pipe wall. A further drawback of such valves resides in that the dust particles deposit and sinter on the valve body.