Study on Properties of Cold‐Bonded Briquettes Prepared from Return Fines of Sinter

Abstract

Return fines of sinter (return fines) are used to prepare cold‐bonded briquettes (CBBs). The reduction disintegration index (RDI) of RDI+3.15 and compressive strength after RDI experiment of CBB are higher than that of the sinter. For microscopic morphologies after RDI experiment, cracks initiate in the area of the return fines but do not propagate through the whole matrix of CBB. The reduction index (RI) of CBB is lower than that of the sinter; conversely, the compressive strength of CBB after RI experiment is higher than that of the sinter. For phase composition after RI experiment, there are phases of metallic iron, wüstite, and silicate in the periphery part, whereas there are calcium ferrite, wüstite, and silicate in the core part. The reduction behavior of CBB can be improved by decreasing the volume of CBB and adding coke in the CBB. The return fines are bonded by the compound binder in two ways: forming a mutually interlaced reticular structure and a dense and acicular solid connecting bridge. For the phase change of the compound binder with temperature, the total content of bredigite is above 63% at 300 to 1100 °C; moreover, the phases of melilite, Ca2(Al, Fe)2O5, and Ca(Al, Fe)2O4 appear respectively at different temperatures as new bonding phases.

Reduction Kinetics of Cold‐Bonded Briquette Prepared from Return Fines of Sinter with Carbon Monoxide and Coke

“…CBBC comprised 84 wt% of return fines, 7 wt% of compound binder, and 9 wt% of nut coke. According to our previous studies, the amount of binder and coke nut added was set at 7% and 9%, respectively, to ensure that the cold‐bonded briquette's strength and reducibility satisfy the demands of a blast furnace [ 1 ] . The nut coke was ground to a fineness of less than 0.5 mm to ensure it is entirely utilized.…”

“…Return fines of sinter is now being utilized in blast furnaces straight after cold briquetting, a novel method of return fines utilization. [ 1–4 ] This technique can prevent return fines from being repeatedly sintered at high temperatures. On the one hand, it can lower the amount of energy used by the sinter plant, and on the other, it can increase the output of the sintering process.…”

“…Our previous study found that the reducibility of cold‐bonded briquette prepared from return fines was lower than that of sinter due to its large particle size, and adding coke can significantly increase reducibility. [ 1 ] Therefore, in this article, there are two different types of samples involved in the reduction mechanism investigation, one is the cold‐bonded briquette without coke (CBB) and the second one is the cold‐bonded briquette with coke (CBBC). First, the reduction degree and reduction velocity index (RVI) are analyzed.…”

“…Cold‐bonded briquette prepared from return fines has successfully substituted 5–10% of the sinter in a 2800 m 3 blast furnace in Gansu Province, China. [ 1,4 ] However, the lack of knowledge regarding the cold‐bonded briquette prepared from return fines’ reduction kinetics in the blast furnace prevents further advancements in the cold‐bonded briquette prepared from return fines’ utilization ratio.…”

Metallurgical Properties of Vacuum Extrusion Iron‐Rich Dust Briquette and Its Effects on Blast Furnace Soft Melting Zone

“…In addition, some studies have explored the possibility of dust briquette recycling in converters and rotary hearth furnaces. [12,18] Through a review of previous literature, it is found that the current research on dust briquette mainly focuses on all-dust briquette, that is, both carbon reducing agents and iron oxides generated during the production of iron and steel. Furthermore, research has predominantly centered on investigating the reduction behavior of individual briquette in blast furnaces, briquette there is limited research on the impact of dust briquette on the softening-melting zone of blast furnaces.…”