Migration pattern of chlorine during co-pyrolysis for herb residue and coal

Taking coal and herb residue as the main research object, the thermal analysis law of inorganic chlorine in the mixture of coal and herb residue was studied by dual-temperature tube furnace, Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) analysis. Results showed that comparing the distribution of chlorine in solid, liquid as well as gases produced during pyrolysis, it could be seen that when the pyrolysis temperature and the sample percentage changed, the distribution of chlorine in the solid and gas phases varied greatly, but the change in the liquid phase was little. Their ranges of chlorine variation were 23.35%, 6.05% and 17.29% in solid, liquid and gas phase from 300 °C to 900 °C at the herb residue addition of 50 wt%. The ranges were 30.83%, 2.43% and 33.26% about the additive quantity of herb residue from 10 wt% to 90 wt% at the pyrolysis temperature of 500 °C. When the addition of the herb residue was 0–70 wt%, the content of chlorine in the coke increased with the increasing herb residue. When the addition of the herb residue reached 70 wt%, it reached the maximum, which was 0.0806%. There was synergism between herb residue and coal. The content of chlorine in semi-coke (or coke) decreased with the increasing temperature at 300–900 °C. The major materials of the coke for herb residue and coal at 500 °C consisted of SiO2, KCl and CaCO3 by EDS and XRD. It provides a method for harmless co-utilization of coal and herb residue.