Abstract: In order to make the properties of the coal briquette specimens(CBS) been closer to that of the raw coal specimens(RCS), and to improve the consistency between the relevant physical simulation test and the actual engineering, uniaxial compression mechanical properties, seepage characteristics and microstructure of the secondary carbonized hot-pressed CBS are tested and analyzed by changing the temperature conditions, and effects of temperature on the mechanical properties and microstructure of the briquette are also investigated. The results show that: (1) With the increase of carbonization temperature, an increase followed by a decrease is observed in the uniaxial compressive strength of secondary carbonized hot-pressed CBS. When the carbonization temperature is 300℃, its uniaxial compressive strength is close to that of RCS. (2) Under triaxial compression, the permeability of the hot-pressed CBS firstly decreases and then increases with the increase of axial compression, and the initial permeability shows an increasing trend with the increase of carbonization temperature. (3) The characteristic peak positions of the secondary carbonized hot-pressed CBS and RCS in the FT-IR organic functional group test are basically consistent. However, the corresponding characteristic peak strength is different, and the functional group response of the infrared spectrum of the secondary carbonized hot-pressed CBS at 300℃ and 450℃ is the closest to that of the RCS. (4) Compared with the RCS, the secondary carbonized hot-pressed CBS has a more uniform pore size distribution with a small proportion of micropore and small specific surface area. Moreover, as the carbonization temperature increases, the average pore size and specific surface area of the secondary hot-pressed CBS firstly decrease and then increase. Additionally, the pore size and specific surface area are relatively the smallest when the carbonization temperature is 300℃. The research results can provide references for the optimization of forming conditions of secondary carbonized hot-pressed CBS and the study of mechanical properties of secondary carbonized briquette.

Key words: coal briquette specimen, secondary carbonization, carbonization temperature, mechanical properties, seepage characteristics