Mechanical Engineering, Semnan University
The present study carefully examined entropy generation during wustite pellet reduction to sponge iron. The finite volume method was used to solve the governing equations. The grain model was used to simulate the reaction rate. The reactant gases including carbon monoxide and hydrogen were converted to water and carbon dioxide after wustite reduction. Entropy is generated by heat transfer, mass transfer and chemical reactions. The rate of entropy generation is studied over a period of 150 minutes. Based on the governing equations, the share of each process in the generation of entropy was calculated. The effects of gas ratio, porosity, and tortuosity and grain diameter of wustite pellet on entropy generation were investigated. The porosity was changed from 0.2 to 0.5, tortuosity from 1 to 4, grain diameter from 7 to 20 mm and the ratio of reducing gas from 0.5 to 2. According to the results maximum value of entropy generation nearly occurs during first 20 minutes of the reduction process. It is shown that the heat transfer had the highest contribution to entropy generation. The results also indicates porosity and gas ratio are inversely proportional to the rate of entropy generation while tortuosity and grain diameter are directly proportional to entropy generation rate.