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 Pelotizacao de Fabrica (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.
Highlights
Pelletizing is the process of compression molding of a material in the form of pellets
This study suggests the analysis of the combustion mechanism in the burning zone, more precisely scrutinizing the energy imparted by the combustion reaction, and how this energy can be rationalized to obtain lower fuel consumption
As some data is not possible to collect with the furnace in operation, some of these variables were analyzed qualitatively, and proposals have been made for their changes, aimed at reducing fuel consumption
Summary
Pelletizing is the process of compression molding of a material in the form of pellets. A wide variety of different materials can pass through such a process, including chemical compounds, iron ore, animal feed, among others. In the case of iron ore, pelletizing in ultrafine particles occurs through heat treatment. This ultra-fine fraction (less than 0.15 mm) is found this way in nature or created in the beneficiation process. The pelletizing produces spherical agglomerates of sizes in the 8 to 18 mm range, with appropriate characteristics to feed reduction units, such as blast furnaces. The plant under study has an annual budget of production in the range of 4 million tons of iron ore pellets
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