Method of burning calcined and uncalcined pulverous raw material and rotary kiln plant therefor

摘要

A method is disclosed for heat treating a preheated pulverous raw material containing at least a portion of lime to produce a partial calcination prior to passing the raw material down through an inclined rotary kiln for further heat treatment. Partial calcining is accomplished by introducing into at least one end of a rotary kiln an amount of fuel sufficient for preheating, at least partially calcining, and substantially completely sintering the raw material, at least part of the fuel being introduced into the lower material outlet end portion of the kiln. An amount of oxygen containing gas sufficient for substantial combustion of the fuel introduced into the kiln is introduced into the lower end portion of the kiln, and preheated raw material is introduced into the mouth of the kiln in such a manner that the material is entrained in gases exiting from the kiln mouth. The gas and entrained material exiting from the kiln are directed into a calcination chamber communicating with the upper material inlet end portion of the kiln such that the material is at least partially calcined by the contact with the kiln exit gases. The material is thereafter separated from the kiln exit gases and reintroduced into the upper end of the kiln in a manner which permits it to pass through the kiln for further heat treatment while avoiding entrainment in the kiln exit gases. A rotary kiln plant for practicing the method is also disclosed which provides for at least partial calcining of the material initially introduced into the kiln and thereafter reintroducing the partially calcined material in such a manner as to promote passage down through the kiln for further heat treatment.