Process and installation for the heat treatment of fine-grained charges

摘要

Process for heat treating finely ground material comprises:(a) preheating the material in a multistage preheating zone (1) using hot gases; (b) further heating the preheated material in a calcination zone (4) provided with additional fuel and containing hot waste gases passed through a combustion zone (2) and further calcining; (c) finish annealing the calcined material in the combustion zone and then cooling in a cooling zone (3). Heated spent air from the cooling zone is fed into the calcination zone as tertiary air and a partial zone is operated as reaction chamber (6) which is charged with preheated material from the second lowest preheated stage and in which a reducing atmosphere is maintained to reduce the nitrogen oxide content in the waste gases of the combustion zone. The novelty is that the preheated material from the second lowest preheated stage (1b) is fed into the lower region (6a) of the reaction chamber (6), whilst the preheated material from the third lowest preheated stage (1c) is divided into two partial amounts, from which a first amount is added to the second lowest preheated stage and a second amount to the upper final region (6b) of the reaction chamber (6). Tertiary air is fed to the lower region (6a) of the reaction chamber (6). An apparatus used to carry out the process is also claimed.