Combustion behavior of granulated coke breeze in iron ore sintering

摘要

This paper investigated the combustion behavior of coke breeze granulated with other raw materials for iron ore sintering in a broad temperature range up to 1350 degrees C in air and sintering flue gas atmosphere, based on the exploration of the physiochemical characteristics of the coke breeze granules in industry. It was shown that after granulation the -0.25 mm coke breeze particles adhered to nuclei constituted by other sintering raw materials or served as a component of granules composed of mixed fine particles with homogeneous composition. Conversely, +0.5 mm coke breeze particles acted as nuclei to which fine particles of other materials adhered. The coke breeze particles with size of 0.25-0.5 mm, on the other hand, had dual roles as either adhering fines or nuclei. According to the combustion tests of typical granules consisted of -0.25 or 2-3 mm coke breeze particles, the structure and size of the granules as well as atmosphere strongly affected the combustion behavior of coke breeze. The adhering fines on the surface of coke breeze caused a decrease in its combustion rate in air (e.g., up to 26% at 950 degrees C and 1050 degrees C). Compared with the adhering fines, the sintering flue gas atmosphere played a more pronounced role in reducing the combustion rate. In this atmosphere, the combustion rate was in close association with the reaction between coke breeze and iron oxide in adjacent iron ore particles. The granules composed of -0.25 mm mixed particles could exhibit lower reduction reaction temperature (approximately a 100 degrees C difference) and stronger reduction reaction intensity than those consisted of coarse coke breeze in the size of 2-3 mm, leading to a higher heat loss. Minimizing the addition of -0.25 mm coke breeze, maintaining the highest combustion temperature at around 1300 degrees C, and keeping relatively high oxygen content in atmosphere are expected to promote combustion efficiency of coke breeze and thus energy utilization in iron ore sintering. (C) 2018 Elsevier B.V. All rights reserved.