Hot-press briquetting of carbon-rich coal gasification residues using a corn-based biomass binder: mechanical strength, gasification reactivity, and binding mechanism

Abstract

Coal gasification fine slag (CGFS) exhibits poor briquetting characteristics and cannot be directly reused in furnaces. To facilitate the beneficial reuse of this byproduct, we systematically investigate using carbon-rich residue (CR), a CGFS product, coupled with a corn stalk-based biomass binder and hot-pressing to produce briquetted carbon-rich residue (BCR). The effects of the briquetting conditions and shape on the mechanical strength and gasification reactivity of the BCR were investigated. The optimal briquetting parameters were identified as an alkali-urea-treated biomass binder content of 25%, a hot-pressing temperature of 175 °C, and a pressure of 7.5 MPa. Under these conditions, the drop strength of all BCR samples exceeded 99.7%. The BCR sample with a height-to-diameter ratio of 0.8 exhibited the best mechanical strength, with a compressive strength of 620.8 N, which is more than double the industrial standard of 300 N. Moreover, the gasification reactivity and carbon conversion rates were superior to those of raw CR. Mechanistic analysis indicated that lignin and amide components generated during binder preparation act as active viscous precursors. During hot-pressing, the lignin softened and coated the CR particles, and the hydrogen bond network was reconstructed at the molecular level to enhance interfacial bonding. Additionally, the amide components bonded tightly with the CR particles, further strengthening interfacial bonding and forming a dense BCR structure. This study provides a technical reference for the synergistic beneficial reuse of CGFS and biomass solid wastes.

Graphical abstract

Keywords

corn stalk binder / coal gasification fine slag / hot press briquetting / compressive strength / gasification reactivity

References

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