Method and device for removing mercury during the production of cement clinker

A method for separating mercury from exhaust gases during production of cement clinker, which comprises the steps of:

• feeding in raw materials, required for producing the cement clinker, into a pre-heating stage against a direction of flow of the exhaust gases according to a counter flow principle, and the mercury bonded in the raw materials is vaporized due to a heating of the raw materials in the pre-heating stage;
• firing the raw material in a rotary kiln;
• using the exhaust gases conducted in a main flow for at least partially mill drying the raw materials in at least one raw mix mill;
• dedusting the exhaust gases in at least one filter stage before the exhaust gases escape into atmosphere;
• feeding dust separated in the at least one filter stage into the pre-heating stage at least partially together with a milled raw material;
• forming a circuit for the mercury in the exhaust gases between the pre-heating stage and the raw mix mill or the at least one filter stage;
• and
• branching off from the main flow of the exhaust gases a sub-flow of 1 to 30 per cent by volume of the exhaust gases having a temperature of at least 300° C., and the exhaust gases of the sub-flow are first dedusted and then the mercury contained therein is separated.

A device for separating mercury from exhaust gases during a production of cement clinker, the device comprising:

• a pre-heating stage;
• a feed point for raw materials required for producing the cement clinker against a direction of the exhaust gases according to a counter flow principle in said pre-heating stage;
• a rotary kiln for firing the raw materials;
• at least one filter stage for dedusting the exhaust gases conducted in a main flow before the exhaust gases escape into atmosphere;
• at least one raw mix mill for at least partially mill drying the raw materials;
• and
• a circuit for removing the mercury in the exhaust gases disposed between said pre-heating stage and said raw mix mill or said at least one filter stage, a sub-flow of 1 to 30 per cent by volume of the exhaust gases being branched off in a region of the main flow of the exhaust gases where the exhaust gases have a temperature of at least 300° C., said circuit having at least one separator for dedusting the exhaust gases of the sub-flow and thereafter at least one stage for separating the mercury from the exhaust gases of the sub-flow.