IJE TRANSACTIONS B: Applications Vol. 31, No. 8 (August 2018) 1274-1282    Article in Press

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A. Zare Ghadi, M. S. Valipour and M. Biglari
( Received: July 28, 2017 – Accepted in Revised Form: January 23, 2018 )

Abstract    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.


Keywords    Wustite Pellet, Entropy Generation, Mathematical Model, Grain Model


چکیده    در کار حاضر تولید آنتروپی در طول فرایند احیای گندله وستیتی به آهن اسفنجی مورد مطالعه قرار گرفته است. روش حجم محدود برای حل معادلات حاکم استفاده شده است. مدل دانه‏ای برای شبیه‏سازی نرخ واکنش مورد استفاده قرار گرفته است. پس از اتمام فرایند احیای وستیت گازهای احیا شامل مونوکسیدکربن و هیدروژن به آب و دی کسیدکربن تبدیل می‏شوند. آنتروپی از طریق انتقال حرارت، انتقال جرم و واکنش‏های شیمیایی تولید می‏شود. نرخ تولید آنتروپی در طول زمان 150 دقیقه بررسی می‏شود. بر اساس معادلات حاکم، سهم هر فرایند در تولید آنتروپی محاسبه شده است. تاثیرات نسبت گاز، تورچیاسیتی و قطر دانه وستیتی بر روی تولید آنتروپی بررسی شده است. تخلخل در بازه 2/0 تا 5/0، تورچیاسیتی در بازه 1 تا 4، قطر ذرات در بازه 7 تا 20 میلیمتر و نسبت گاز در بازه 5/0 تا 2 متغیر است. بر طبق نتایج بیشینه مقدار تولید آنتروپی تقریبا در 20 دقیقه ابتدایی رخ می‏دهد. مشاهده شده است که انتقال حرارت بیشترین سهم در تولید آنتروپی را دارد. همچنین نتایج نشان می‏دهند، تخلخل و نسبت گاز رابطه عکس با نرخ تولید آنتروپی دارد در حالیکه تورچیاسیتی و قطر دانه با نرخ تولید آنتروپی رابطه مستقیم دارد.


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