Study on the pyrolysis behavior of coal-water slurry and coal-oil-water slurry

In this work, different concentrations of coal-water slurry and coal-oil-water slurry were prepared and pyrolyzed at various temperatures of 800–1000 °C. The chemical characteristics and combustion reactivities of chars and the formation mechanism of main gas components of CO, CO2, CH4, and H2 were investigated. With the water content of the coal-water slurry increasing, the formation of CO and CH4 were hindered, while CO2 and H2 were promoted. For the coal-oil-water slurry, oil promoted CH4 and H2 production but inhibited CO and CO2. Moreover, the variation of the nitrogen-containing pyrolytic gas during pyrolysis was studied for various concentrations of coal-water and coal-oil-water slurries at different temperatures. The relative content of HCN and NH3 gradually increased with the increase of pyrolysis temperature and water content. For coal-oil-water slurry, the waste lubricating oil promoted the formation of HCN and NH3, with the relative content of HCN being much higher than that of NH3. To study the mechanism of nitrogen migration during pyrolysis, Lammps was used to simulate pyrolytic behavior of pyrrole and pyridine under N2 and steam atmospheres. The increase in temperature promoted the decomposition of pyrrole and pyridine, thereby promoting the production of HCN and NH3. Finally, the properties and the combustion reactivities of the chars were analyzed. The water and oil content in the coal-water slurry increased the structural ordering degree of chars but decreased the combustion reactivities.