Analysis of combustion efficiency in a pelletizing furnace

Abstract The objective of this research is to assess how much the improvement in the combustion reaction efficiency can reduce fuel consumption, maintaining the same thermal energy rate provided by the reaction in a pelletizing furnace. The furnace for pelletizing iron ore is a complex thermal machine, in terms of energy balance. It contains recirculation fan gases and constant variations in the process, and the variation of a single process variable can influence numerous changes in operating conditions. This study demonstrated how the main variables related to combustion in the burning zone influence fuel consumption (natural gas) from the furnace of the Usina de Pelotização de Fábrica (owned by VALE S/A), without changing process conditions that affect production quality. Variables were analyzed regarding the velocity and pressure of the fuel in the burners, the temperature of the combustion air and reactant gases, the conversion rate and the stoichiometric air/fuel ratio of the reaction. For the analysis, actual data of the furnace in operation was used, and for the simulation of chemical reactions, the software Gaseq® was used. The study showed that the adjustment of combustion reaction stoichiometry provides a reduction of 9.25% in fuel consumption, representing a savings of US$ 2.6 million per year for the company.

摘要 本研究旨在评估：在维持球团炉（pelletizing furnace）内反应所提供的热能速率保持不变的前提下，燃烧反应效率的提升可在多大程度上降低燃料消耗。铁矿石球团炉属于能量平衡（energy balance）维度下的复杂热工设备，其配备烟气再循环系统，且生产过程始终存在波动，单个工艺变量的变化即可引发诸多运行工况的改变。本研究阐明了VALE S/A旗下Usina de Pelotização de Fábrica厂的炉体燃烧区相关主要变量，在不改变影响产品质量的工艺条件的前提下，对炉体燃料（天然气，natural gas）消耗的影响机制。研究针对燃烧器内燃料的流速与压力、助燃空气与反应气体的温度、反应转化率以及化学计量空燃比（stoichiometric air/fuel ratio）等变量展开分析。本次分析采用该炉体的实际运行数据，并借助Gaseq®软件开展化学反应模拟。研究结果显示，调整燃烧反应的化学计量比可使燃料消耗降低9.25%，每年可为该公司节省约260万美元的成本。