Technical research on low-temperature and low-carbon preparation of iron-bearing burdens from typical iron concentrates

Significant carbon emission reduction pressure is imposed on the pre-ironmaking processes at the present stage, and a high carbon reduction potential is possessed by the cold-bonded briquetting process. In response to the dual-carbon goals of the iron and steel industry, the effects of forming moisture, forming linear pressure and iron concentrate type on the green briquette strength and consolidated briquette strength of cold-bonded briquettes are systematically investigated with four typical types of iron concentrates adopted. The evolution laws of microscopic pore structures are characterized via SEM-EDS and mercury intrusion porosimetry, and the influencing mechanisms of cold-state strength are clarified. Within the research scope, the performance of cold-bonded briquettes is obviously improved by reducing forming moisture and increasing forming linear pressure, and the optimal forming moisture and forming linear pressure are determined as 4.5% and 9.80 kN/mm, respectively. The mechanical interlocking force between particles are weakened by the increase of forming moisture, so that the strengths of green briquettes and consolidated briquettes are decreased synchronously. With increasing forming line pressure, particle rearrangement is promoted, the contact area between particles is increased, and the interparticle bonding bridges are strengthened, thereby improving the strength of cold-bonded briquettes. Opposite effects on the strength in the forming stage and consolidation stage are exerted by the particle size of iron concentrates. Higher green briquette strength and lower consolidated briquette strength are obtained with finer average particle size of iron concentrates. Under optimized forming and consolidation parameters, cold-bonded briquettes prepared from four kinds of iron concentrates are enabled to reach the dropping strength of green briquettes no less than 4 times/(0.5 m·P), consolidated briquette strength no less than 2 500 N/P and tumbler strength no less than 85%. All prepared briquettes are qualified to meet the cold-state strength requirements of blast furnace burden, and favorable engineering application prospects are presented.