Effect of pressure on the structure and reactivity of demineralized coal during O2/H2O thermal conversion process

Abstract Pressure can strongly affect the thermal conversion characteristics of coal. This work used a pressurized horizontal furnace to study the pyrolysis (Ar) and O2/H2O (10 vol%/25 vol%) thermal conversion characteristics of demineralized coal under different pressure (0.1–1.5 MPa) and at 1000 °C. The changes of carbon conversion, pore structure, carbon skeleton structure, and surface functional group structure of different pressure pyrolysis char and its combustion residual char were obtained by using N2 adsorption, Raman and X-ray Photoelectron Spectroscopy (XPS) test methods. A micro fluidized bed reaction analyzer was then used to test the reactivity of the char to explore the influence of pressure. Pressure can increase the yield of pyrolysis char from 64.81% to 68.78% and promote the conversion of char in O2/H2O conditions from 27.78% to 78.58%. For the pore structure of char, pressure and O2/H2O atmosphere have a positive promotion effect, and have a similar effect on the degree of graphitization and the relative content of C–C and C–H bonds. Largest BET area of char is 234.72 m2/g at 1.5 MPa of pyrolysis and 793.43 m2/g at 1.0 MPa of O2/H2O combustion, respectively. For the reactivity of char prepared in O2/H2O combustion, the pore structure is dominant compared to chemical structure.