Fuel Processing Technology, Vol.151, 40-49, 2016
Effects of atmospheric gas on pyrolysis characteristics of briquetted lignite and surface properties of semi-char
The physicochemical properties of semi-char produced by the pyrolysis of binder cold-briquetted lignite (BCBL) in a fixed bed reactor at 600 degrees C under different atmospheres of CO, CO2, CH4, H-2, and N-2 were investigated comprehensively. Using the N-2 BET method, the specific surface area of the different semi-chars were in the range of 1.71-2.53 (m(2) g(-1)), the pore volume and average pore diameter of the CO semi-char were lowest, and the N-2 semi-char values were highest. In contrast, the Dubinin CO2 method at 0 degrees C gave specific surface areas of semi chars in the range 165-192 (m(2) g(-1)). The CO, N-2 and CH4 semi-chars had the largest diameter, and the H-2 semi-char had the lowest diameter. The TGA test indicates the ignition temperature of BCBL was lower than different semi-chars. The FTIR spectra of BCBL and different semi-chars revealed that the removal rate of the oxygen-containing functional groups showed the highest efficiency under CO atmosphere, thus representing that CO could help to cleave the ether bond. The C1s, O1s, N1s, and S2p spectra of semi-chars under different atmospheres were analyzed by XPS. Raman analysis was also conducted to study the degree of structural orderliness in different semi-chars, which has great significance to the compressive mechanical strength of it. The semi char produced in an atmosphere of CO2 showed a more condensed crystalline structure and lowest compressive mechanical strength among all the semi-chars. (C) 2016 Elsevier B.V. All rights reserved.
Keywords:Briquetted lignite;Low temperature pyrolysis;Semi-char;Ignition temperature;Pyrolysis atmosphere