Effect of temperature on adsorption characteristics and pore structure of secondary carbonized briquette

The secondary charred coal specimens were prepared at the charring temperatures of 250,300,350 and 400 ℃ using the self-developed secondary charred hot-pressed coal briquette specimens(CBS) forming test equipment,and were tested and analyzed by scanning electron microscope,nuclear magnetic resonance,specific surface and pore size analyzer to study the effects of charring temperature on the adsorption characteristics,pore development and microstructure of CBS The results showed that：with the increase of charring temperature,the moisture of CBS gradually decreased,the ash and fixed carbon content gradually increased,the volatile matter first increased and then decreased,and the density first increased and then decreased; the CBS formed gelatinous substances and uniformly distributed on the surface of coal particles during the pyrolysis process,and solidified to fill the interstices of pulverized coal particles,and with the further increase of temperature,the surface of CBS changed from smooth and complete lamellar structure to fragmented The percentage of small pores in raw coal specimens(RCS) is the largest,and the percentage of small pores in the secondary charred coal tends to increase and then decrease with the increase of temperature,and the percentage of medium and large pores tends to decrease and then increase; both the CBS and the RCS at 300 ℃ are mainly adsorption pores,and the connectivity between pores is poor,and the CBS is mainly percolation pores and relatively less adsorption pores after the temperature continues to increase. The isothermal adsorption lines of the RCS and the CBS under different charring temperature conditions conformed to the type IV isothermal adsorption line.The specific surface area distribution of each pore section of the RCS and the CBS is relatively uniform,with a unimodal distribution. The specific surface area of the CBS showed a trend of increasing and then decreasing with the increase of charring temperature,the average pore size showed a trend of decreasing and then increasing,and the maximum adsorption capacity showed a trend of increasing and then decreasing.