Pore structure evolution during the coke graphitization process in a blast furnace
- PDF / 792,997 Bytes
- 8 Pages / 592.8 x 841.98 pts Page_size
- 24 Downloads / 215 Views
Pore structure evolution during the coke graphitization process in a blast furnace Hao-bin Zhu 1), Wen-long Zhan 1), Zhi-jun He 1), Ying-chang Yu 2), Qing-hai Pang 1), and Jun-hong Zhang 1) 1) School of Materials and Metallurgy, University of Science and Technology Liaoning, Anshan 114051, China 2) Ansteel Engineering Technology Corporation Limited, Anshan 114021, China (Received: 3 September 2019; revised: 8 October 2019; accepted: 10 October 2019)
Abstract: Pore structure is an important factor influencing coke strength, while the property of coke is essential to maintaining gas and liquid permeability in a blast furnace. Therefore, an in-depth understanding of the pore structure evolution during the graphitization process can reveal the coke size degradation behavior during its descent in a blast furnace. Coke graphitization was simulated at different heating temperatures from 1100 to 1600°C at intervals of 100°C. The quantitative evaluation of the coke pore structure with different graphitization degree was determined by vacuum drainage method and nitrogen adsorption method. Results show that the adsorption and desorption curves of graphitized coke have intersection points, and the two curves did not coincide, instead forming a “hysteresis loop.” Based on the hysteresis loop analysis, the porous structure of the graphitized coke mostly appeared in the shape of a “hair follicle.” Furthermore, with an increase in heating temperature, the apparent porosity, specific surface area, total pore volume, and amount of micropores showed good correlation and can divided into three stages: 1100–1200, 1200–1400, and 1400–1600°C. When the temperature was less than 1400°C, ash migration from the inner part mainly led to changes in the coke pore structure. When the temperature was greater than 1400°C, the pore structure evolution was mainly affected by the coke graphitization degree. The results of scanning electron microscopy, energy dispersive spectrometry, and ash content analyses also confirmed that the migration of the internal ash to the surface of the matrix during the graphitization process up to 1400°C contributed to these changes. Keywords: coke; blast furnace; graphitization; pore structure; ash migration
1. Introduction Coke is the main carrier of energy flow in the iron making process, ensuring the reduction and melting of iron-bearing materials [1]. In a blast furnace (BF) hearth, coke is the only material that remains in solid state, thus the pore structure provides an important passage for slag and iron dripping and gas flow rising above in the hearth. Pores of coke are formed from the precipitation of volatile gases during the coking process. The different states of gas evolution form macroscopic open and closed pores [2–4]. The pore size division has not yet to be standardized. The relationship between coke strength and pore structure has been intensively studied. Jin and Fu [5] believed that as the porosity increases, the solution loss reaction of coke tends to
Data Loading...
