RESUMO
Pyrolysis holds immense potential for clean treatment of pulp and paper mill sludge (PPMS), enabling efficient energy and chemical recovery. However, current understanding of PPMS pyrolysis kinetics and product characteristics remains incomplete. This study conducted detailed modeling of pyrolysis kinetics for two typical PPMSs from a wastepaper pulp and paper mill, namely, deinking sludge (PPMS-DS) and sewage sludge (PPMS-SS), and analyzed comprehensively pyrolysis products. The results show that apparent activation energy of PPMS-DS (169.25-226.82 kJ/mol) and PPMS-SS (189.29-411.21 kJ/mol) pyrolysis undergoes significant change, with numerous parallel reactions present. A distributed activation energy model with dual logistic distributions proves to be suitable for modeling thermal decomposition kinetics of both PPMS-DS and PPMS-SS, with coefficient of determination >0.999 and relative root mean square error <1.99 %. High temperature promotes decomposition of solid organic materials in PPMS, and maximum tar yield for both PPMS-DS (53.90 wt%, daf) and PPMS-SS (56.48 wt%, daf) is achieved at around 500 °C. Higher levels of styrene (24.45 % for PPMS-DS and 14.71 % for PPMS-SS) and ethylbenzene (8.61 % for PPMS-DS and 8.33 % for PPMS-SS) are detected in tar and could be used as chemicals. This work shows great potential to propel development of PPMS pyrolysis technology, enabling green and sustainable production in pulp and paper industry.
RESUMO
In this study, a hydrogen fuel jet-stabilized combustor is proposed, the combustion flow characteristics are numerically investigated under the conditions of three equivalence ratios (1, 0.37, and 0.22), and the effects of hydrogen flow rate assignment on the combustion flow are also analyzed. The results show that it is easier for the multijet scheme to form a full and stable vortex structure pair in the recirculation zone under lean conditions than the single-jet scheme, and it has a uniform reaction rate to form larger combustion zones, which makes it easier to achieve flame stabilization. The combustion efficiency of two fuel jet schemes is less than 65% when the equivalence ratio is 1, and complete combustion can be achieved under lean conditions; however, the outlet temperature distribution factor (OTDF) is basically the same. For the multijet scheme with an equivalence ratio of 0.22, as the flow rate assigned to the central jet decreases, a stable and full vortex pair is formed in the recirculation zone, and a high-temperature region can be formed under each working condition, but its area decreases with the central jet flow rate. The combustion efficiency in the recirculation zone increases first and then decreases as the central jet flow decreases, and the OTDF decreases with it.
