Influence of moisture and feedstock form on the pyrolysis behaviors, pyrolytic gas production, and residues micro-structure evolutions of an industrial sludge from a steel production enterprise

To raise the knowledge on the pyrolysis of sludge obtained from a steel production enterprise, the pyrolysis tests were carried out under different conditions, such as sludge forms, temperatures, initial weights, heating rates, and moisture contents. With the initial weight increasing, the TG and DTG curves almost superposed with each other at the first two stages, while delayed after that. As the heating rate went from 10 to 40 °C/min, the comprehensive devolatilization index D obviously increased from 1.17 × 10⁻⁷ to 15.93 × 10⁻⁵%²/(°C³ min²). The kinetic analysis results indicated that the activation energies increased with the pyrolysis proceeding. The natural dehydration rate of the wet sludge block would reach maximum as certain pore canals and crannies formed on the surface. The pyrolysis tests of SS in a horizontal tube furnace showed that the product yields, and contents and LHV of pyrolytic gases were affected by the sludge forms, temperature, and moisture contents. The moisture in the sludge could act as the in-situ gasification agent, promoted the conversion of organics in the SS, and increased the H₂ yield. Micro-structure analysis showed that the surface of the residues would be brighter as the moisture and pyrolysis temperature increased.