ES419352A1 - Process of heat-treating magnetite iron ore involving heat recuperation from cooling of the product - Google Patents

Abstract

Procedure for preparing separate hard granules from finely divided magnetite iron ore in which the raw granules of finely divided ore are subjected to a thermal hardening treatment consisting of forming a layer of granules on a moving grate and transporting the layer of granules successively through at least some drying and precalcining zones, shaking the granules in a rotary kiln in which a fuel is burned, and then transporting the granules through a refrigerator including at least a first and second cooling zones in series, passing air through the granules in the first cooling zone to form a preheated stream of oxidizing gases, and then passing said gas stream counter-current with respect to the movement of the granules through the oven so that it flows through the granule layer in the areas precalcining and drying of the mobile grill; characterized by the stages consisting of: A. Burning a certain amount of fuel in a certain amount of preheating oxidizing gas circulating through the furnace to obtain a predetermined amount of oxidizing gas with a temperature of 1,149 to 1,343ºC (2,100 to 2,450ºF), providing said hot gases, according to the speed at which the granules travel through the precalcination zone and through the rotary kiln, from 60 to 80% oxidation of the magnetite in hematite, in the precalcination zone and from 2 to 10% of additional oxidation of the magnetite in hematite, in the furnace, leaving the furnace to penetrate into the refrigerator 62 to 90% of oxidized granules at the temperature of approximately 1,316ºC (2,400ºF), B. move the granules through the first cooling zone, C. ensure air circulation in the first cooling zone with a sufficient flow rate to continue the oxidation of the magnetite remaining in the granules, without fully performing it, D. ensuring air circulation in the second cooling zone to substantially complete the oxidation of the magnetite remaining in the granules to transform it into hematite, and also to ensure a certain degree of cooling of the granules with corresponding heating of the air and of the combustion gases passing through the second cooling zone, and E. pass hot air and flue gases from the second cooling zone through the raw granule layer on the moving grate, before the granules pass through the precalcination zone, to recover and return to the process the heat released from the granules by the final oxidation of the hematite magnetite in the granules located in the second cooling zone. (Machine-translation by Google Translate, not legally binding)