Patent ID: 7384263

Claim:
Method of burning lumps of material, in particular limestone, in a regenerative shaft kiln ( 3 ) with at least two kiln shafts ( 1 , 2 ) interconnected by an overflow line ( 19 ), in which shafts the material to be burned passes through an upper pre-heating zone ( 8 ), a central burning zone ( 18 ) and a lower cooling zone ( 14 ), whereby combustion air is supplied in the area of the pre-heating zone ( 8 ), cooling air is supplied to the cooling zone ( 14 ) and the supply of combustion gas having a low calorific value of less than 7.5 Mega joules (MJ) per m 3 alternates periodically to each of the shafts ( 1 , 2 ) through ( 9 , 25 ), characterized in that that the combustion gas is pre-heated in heat exchange with process gas of the burning process.