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: For a decrease of NO.sub.x content in the exhaust gases from cement-burning kilns by an addition of ammonia and/or ammonia-containing substances to hot exhaust gases, the exhaust gases are desulfurized at a temperature from 50.degree. to 100.degree. C. in a dry or semidry process by a mixture of raw cement powder and calcium hydroxide, and the mixed solids which have been removed the exhaust gas in a dry state in the desulfurizing stage are returned to the exhaust gas stream when it is at a temperature from 850.degree. to 1,000.degree. C.

Abstract: A separator for collecting solid particles from a gas stream by centrifugal force comprises a vertical cylindrical housing having a coaxial top gas discharge pipe, a lower gas supply line extending coaxially into the housing, and a solids outlet which is laterally disposed in the lower portion of the housing. That separator has its gas supply line closed at its upper end and merging into at least one duct by which a vertically rising gas stream is deflected into a substantially horizontal direction that is tangential to the gas supply line.