Formation of Metallurgical Coke within Minutes through Coal Densification and Microwave Energy

Abstract

This paper shows how feedstock densification gives rise to a step change in the time required to create a metallurgical grade coke using microwave energy. Five densified coking and noncoking coals were heated in a multi-mode microwave 2450 MHz cavity for varying treatment times (2-20 minutes) with a fixed power input (6 kW). Proximate analysis, intrinsic reactivity, coke reactivity, dielectric properties, and petrographic analysis of the coals and microwave produced lump cokes were compared to a commercial lump coke. Densifying the sample prior to microwave treatment enabled a dramatic acceleration of the coking process when combined with targeted high microwave energy densities. It was possible to form fused coke lump structures with only 2 minutes of microwave heating compared to 16-24 hours via conventional coking. Anisotropic coke morphologies (lenticular and circular) were formed from non-coking coal that are not possible with conventional coking and increasing treatment time improved overall coke reflectance. Three of the coals produced coke with equivalent coke reactivity index values of 20-30, which are in the acceptable range for blast furnaces. The study demonstrated that via this process, non-coking coals could potentially be used to produce high quality cokes, potentially expanding the raw material options for metallurgical coke production.

Upgrading of Low-Grade Colombian Coals via Low-Cost and Sustainable Calcium Nitrate Dense Media Separation

“…To explore this potential further, washed Valle coal would need to be characterized for its coking potential and tested in pilotscale coking ovens. In addition, novel coking methods, such as microwave technology, 45 have demonstrated that noncoking coals can be coked rapidly, which may facilitate low-grade coking coal to be used in blends to produce high-quality cokes.…”

“…44 Another consideration is how the coals behave on the stoker furnace bed. Coking coals swell during combustion, 45 while lump thermal coals generally do not. 46 The swelling of lump coal is different from that of small particles of coal.…”

Quantifying the Structural Transitions of Chinese Coal to Coal-Derived Natural Graphite by XRD, Raman Spectroscopy, and HRTEM Image Analyses

“…Carbonaceous materials typically include both graphitizing and nongraphitizing carbons. , Lignite and subbituminous ranks typically belong to nongraphitizing carbon (although thermoplasticity can be induced by microwave heating for some subbituminous samples), and some bituminous and anthracite coals are typically graphitizable to some degree. Anthracite is highly aromatic and can be well-aligned facilitating graphitization .…”

Numerical Simulation of Coal Briquetting Process Using Discrete Element Method

“…27) Given the importance of coal briquetting in the ironmaking process, several reports have been published on how the briquetting conditions, such as the compression pressure and the particle diameter affect the strength of the briquette and the coke. [28][29][30][31][32][33] However, those studies were conducted on a trial-and-error basis, while theoretical studies on the briquetting process are few. In recent years, numerical simulation has been used to investigate the behavior of powder materials.…”