Study on interaction and mechanisms of direct coal liquefaction residue and gas coal in coal blending during coking

Abstract

Crucible cokes were prepared by blending direct coal liquefaction residue (DCLR) with five bituminous coals (JM, FM, 1/3JM, QM, SM). The cold strength and thermal strength of cokes were analyzed. Coal petrology was used to guide and optimize coal blending for coking which was aimed at finding out the mechanism of DCLR and QM partially replacing coking coal (FM or JM) during coking. Results showed that QM and DCLR could partially replace FM or JM when the ratio of high caking coal was under 70%, and the DCLR ratio cannot exceed 6% to guarantee the coke strength. Based on blending scheme JT20, partially replacing JM with DCLR and QM (termed as DCLR-QM-JM system), the optimal DCLR ratio was 3% as M13 increased by 1.20%, M3 declined by 1.21% and CSR* increased by 0.79%. Partially replacing FM with DCLR and QM (termed as DCLR-QM-FM system), the optimal DCLR ratio was 2% as M13 increased by 2.14%, M3 declined by 2.13% and CSR* increased by 1.97%. There existed obvious interactions between raw materials in coal blending and the function mechanism of DCLR and QM could be concluded as follows: With the addition of DCLR, temperature range of the interaction between metaplast and gas in coking system extended to the low temperature region by 50 °C. The continuous gas driving force provided by QM drove much metaplast into the pores of coal particles and bound them to more inert components, which led to decreasing reaction surface and increasing thermal strength of coke.