Bayu Prabowo

Metal nickel nanoparticles in situ generated in rice husk char for catalytic reformation of tar and syngas from biomass pyrolytic gasification

This paper aims to propose a novel catalytic pyrolytic gasification technology for the in situ conversion of tar and syngas, accompanied by the silica-based nickel nanoparticles generated in situ and the highly dispersed rice husk char (RHC), namely RHC Ni. Partially oxidized nickel oxides (i.e., NiO) in the carbon matrix of biochar can be carbothermally reduced to metallic nickel (Ni0) nanoparticles by reducing gases (e.g., CO) or carbon atoms during biomass pyrolysis. Moreover, due to its strong reducibility, the addition of sodium borohydride (NaBH4) can significantly promote the generation of Ni0 by the reduction of NiO, improving the biochars catalytic activity. An ultra-low tar yield can be achieved by pyrolysis of RH Ni and RH Ni–B at 750 °C, in terms of the high tar conversion efficiencies of 96.9% and 98.6%, respectively, compared with the pyrolysis of raw RH. It is noteworthy that the condensable tar could be catalytically reformed into the small molecules of non-condensable tar or gases, which contributes to improving the syngas fuel characteristics in the favor of power generation systems, corresponding to the lower heating value (LHV) of syngas increasing from 10.25 to 11.32 MJ m−3. In addition, the increase of the polymolecular Ni0 was most possibly caused by the disproportionation reaction and strong reducibility of NaBH4. In addition, the produced RHC Ni showed a good performance for the catalytic conversion of tar (conversion efficiency, 96.5%) through co-pyrolysis with biomass. After deactivation, the waste RHC Ni might be easily regenerated via thermal treatment or directly catalytically gasified into the applicable syngas, accompanied by the production of the silica-based nickel nanoparticles.

Combustion characteristics and kinetics study of hydrothermally treated paper sludge by thermogravimetric analysis

The hydrothermal treatment has been utilized to improve solid fuel property of paper sludge. In this study, an investigation on combustion characteristics of the hydrothermally treated paper sludge was performed. The paper sludge was treated at the temperature range of 180–240°C under pressurized conditions with a holding time of 30 minutes by a lab-scale apparatus. After that, the optimized temperature (197°C at 1.9 MPa) was conducted to treat the paper sludge in a pilot plant with the same holding time. The combustion behavior of the products and the reference materials, including cellulose, hemicellulose, and lignin, were studied by the thermogravimetric analysis. The major decomposition of paper sludge was devoted to cellulose. The ignition temperature was originally low around 257–271°C. The burnout temperature was approximately 679–695°C. From the two-stage kinetics study, the activation energy of the treated paper sludge was lower than the original material in range of 113–147 kJ/mol.