Abstract: The waste materials are gasified in a circulating fluidized bed in a gasification reactor, which is supplied with oxygen-containing gas. A gas-solids mixture is withdrawn from the upper region of the gasification reactor and is fed to a separator. Dust-laden gas and separated solids are separately withdrawn from the separator and the separated solids are recycled at least in part to the lower region of the gasification reactor. Temperatures in the range from 700.degree. to 1000.degree. C. are maintained in the gasification reactor. The dust-laden gas which is withdrawn from the separator has a heating value of about 3000 to 6000 kJ/sm.sup.3 and is fed to a combustion chamber and is combusted therein at temperatures from 1200.degree. to 1900.degree. C. Liquid slag is withdrawn from the combustion chamber.

Abstract: A process for producing cement, including preheating a mixture of ground raw materials (raw meal) in a preheating cyclone to form a preheated raw meal, calcining the preheated raw meal in a calciner to form a calcined raw meal, burning the calcined raw meal in a rotary kiln with the aid of a high-grade fuel to form a cement clinker, cooling the cement clinker in a rotary kiln and grinding the cooled cement clinker. The process is characterized by replacing 50 to 70% of the high-grade fuel with a low-grade fuel, gasifying the low-grade fuel in a fluidized bed to form a resulting fuel gas, supplying a first portion of the resulting fuel gas to a main burner of the rotary kiln, a second portion of the resulting fuel gas to the exhaust gas stream from the rotary kiln and a third portion of the resulting fuel gas to the calciner.

Abstract: A control spear serves to close and to controllably open a valve passage in a passage for conducting a dust-containing gas at temperatures of about 400.degree. to 1200.degree. C. The control spear comprises a shaft and a frustoconical head which cooperates with the valve passage. The shaft is movably mounted on the head and is preferably resiliently biased against the shaft.

Abstract: In a housing having an inlet opening and an outlet opening, the shut-off mechanism has a rotary plug for interrupting the flow of flowable material through the housing. Via the rotary plug the outlet opening is gas-tightly sealed and a flow of material through the inlet opening is prevented. The rotary plug is provided with a sealing member, which is rotatable about an axis which is approximately at right angles to the axis of rotation of the rotary plug. The sealing member cooperates with the valve seat, which is associated with the outlet opening. A compression spring extends between the sealing member and the rotary plug and is laterally spaced from the axis of rotation of the sealing member. Upon a movement of the rotary plug the compression spring will impart a certain rotation of the sealing member without a need for a drive.