Preparation of high-strength biochar composite briquette for blast furnace ironmaking

Abstract

In this research, using iron-oxide fines (average size: 2.5 μm) and biochar fines (average size: 50.0 μm), the biochar composite briquette (BCB) for blast furnace (BF) application was prepared by cold briquetting followed by heat treatment. The preparing conditions were optimized regarding its cold crushing strength. Anti-pulverization capability, reaction development, and structure evolution of the optimally-designed BCB under simulated BF conditions were then examined. Results of optimizing BCB preparation conditions showed that a heating temperature of 1073 K was optimal for preparing the BCB. The optimally-designed BCB contained 11.10 wt.% carbon, 72.21 wt.% Fe3O4, 11.25 wt.% FeO, and 0.77 wt.% Fe, 6.44 wt.% gangue, and had a cold crushing strength of 1800 N/briquette. Results of BCB behavior under simulated BF conditions showed that the cold crushing strength after partial reaction of the BCB ranged from 1500 N/briquette to 5500 N/briquette and its maximum volume shrinkage degree was 0.45. The high anti-pulverization capability of the BCB was supported by the slag matrix or the iron network. Under the simulated BF conditions, the BCB underwent five stages of reduction by atmosphere, partial self-reduction and reduction by atmosphere, full self-reduction, partial self-reduction and gasification by atmosphere, and gasification by atmosphere. It is inferred from the experimental findings that, by charging the BCB in BF, an increase of top gas utilization efficiency could be realized, and a favorable influence on lowering the temperature level of the thermal reserve zone could be obtained.

Numerical Simulation of Charging Biochar Composite Briquette to Blast Furnace

“…The difficulty in using BCB in BF is its poor strength under the BF environment. 17) The authors of current study 18) proposed to prepare BCB using cold briquette followed by heat treatment. Under the simulated BF conditions, the cold crushing strength of BCB after partial reaction was from 1 500 N/briquette to 5 500 N/briquette, indicating the BCB is permittable for application as a BF burden.…”

“…These studies showed that, Under the BF conditions, the BCB underwent five stages of reduction by BF gas, partial self-reduction and reduction by BF gas, full self-reduction, partial self-reduction and gasification by BF gas, and gasification by BF gas. 18,19) To evaluate the coke saving level by BCB charging and to optimize the conditions of BF operation, it is important to understand BCB reaction in actual BF and its influence on the BF in-furnace state. Owing to the high-pressure, high-temperature, and hazardous environment in BF, it is impossible to measure directly the required information in BF.…”