Preparation of Formed Coke for Blast Furnace Using Kraft Lignin as a Binder

Abstract

In the steel industry, the development of a coke production technology that uses low-grade coal is desired. Decarbonization by the use of plant biomass is also an important option. A candidate is formed coke, which is produced by forming non-coking coal using a binder, followed by carbonization. Kraft lignin, by-product in pulp and paper mills is a potential binder because it is an aromatic polymer dissolved from wood. In this study, thermal coal powder was blended with softwood kraft lignin powder at ratios from 0 to 20% and was briquetted by cold-pressing or hot-pressing. Then, the briquette was carbonized at 1 000°C to produce formed coke. To verify whether the formed coke has sufficient strength for use in blast furnace, the product was subject to indirect tensile test. The tensile strength of the carbonized formed coke increased with increasing lignin content; however, a formed coke exceeding the target tensile strength of 5 MPa could not be obtained by cold forming. The briquetting temperature was the determinant strengthening factor of the formed coke. Formed coke produced by hot-pressing at temperatures higher than 150°C with 10% lignin at a pressing pressure of 150 MPa successfully attained the target strength. The tensile strength of the formed coke did not always correspond to the density of the corresponding coke, indicating that carbonized products originating from lignin play a role in strongly binding coal particles. Softwood kraft lignin seems a good binding material for low-grade coal to produce formed coke with high strength.

Effect of Biocarbon Addition on Metallurgical Properties of Mill Scale-Based Auger Pressing Briquettes

“…However, the share of substitutable coal has been 2-10%. In their recent article, Nonaka et al 7) used kraft lignin as a binder in coke and found that the tensile strength of coke reached a maximum at 10% lignin content. From a metallurgical perspective, the main concerns are the lower CSR value (coke strength after reduction) and higher CRI value (coke reactivity index).…”

Determination of the Degree of Sodic Modification of Bentonite Using Response Surface Analysis

“…Numerous studies have demonstrated that replacing or partially replacing bentonite with organic binders is feasible. However, due to their high cost and thermal instability, they are not widely utilized [8][9][10][11] . The use of low-cost solid waste as binder raw materials is also a research hotspot.…”