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

Pressure can strongly affect the thermal conversion characteristics of coal. This work used a pressurized horizontal furnace to study the pyrolysis (Ar) and O-2/H2O (10 vol%/25 vol%) thermal conversion characteristics of demineralized coal under different pressure (0.1-1.5 MPa) and at 1000 degrees 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 N-2 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 O-2/H2O conditions from 27.78% to 78.58%. For the pore structure of char, pressure and O-2/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 m(2)/g at 1.5 MPa of pyrolysis and 793.43 m(2)/g at 1.0 MPa of O-2/H2O combustion, respectively. For the reactivity of char prepared in O-2/H2O combustion, the pore structure is dominant compared to chemical structure. (C) 2021 Elsevier Ltd. All rights reserved.