Two stage co-pyrolysis improvement to produce synthetic oil and gas simultaneously from mixed municipal solid waste using natural dolomite-based catalyst

Abstract

Among the two pyrolysis methods, the two-stage type gives better results than the single-stage in converting mixed municipal solid waste (MMSW) into synthetic oil (O-Synthec) and gaseous products (G-Synthec). However, the double energy supply for the heating process in the first and second reactors needs to be considered in terms of efficiency. Therefore to complete the research of two-stage pyrolysis, this study improvised a two-stage co-pyrolysis process supported by a Long Fixed-Bed Catalytic Insert (LFCi) attached to the inner wall of the reactor. In the test, 500 g of MMSW with 8 components was fed into a reactor with LFCi containing a dolomite natural catalyst. The co-pyrolysis process was carried out at a temperature variation of 400–550 °C, and the best results obtained were used as a reference for variations in reaction time from 120 to 210 min. Based on the physical and chemical properties, the co-pyrolysis O-synthec and G-synthec products were subjected to Gas Chromatography Mass Spectrometry (GCMS) analysis and American Society for Testing and Material (ASTM) standard to physical properties test. The results were compared with those of one-stage pyrolysis, direct catalytic and without catalyst. Based on the results, the presence of LFCi in the reactor had a significant effect in increasing the mass yield of O-Synthec at 550 °C with a residence time of 150 min. An increase of 20,14% and decrease 16.77% of O-Synthec and G-Synthec respectively were achieved compared to the uncatalyzed, although the presence of 15.5% peak area oxygenated fractions and 3.0% peak area acid needs to be considered as it impacts the calorific value. The dominant aromatic compound indicates that O-Synthec has similarities with conventional gasoline fuel. Meanwhile, the non-condensable gas (G-Synthec) produced contains a concentration of hydrocarbon compounds in the distribution of C1–C12, which is dominant with tripropylaluminum, formic acid and butenes. The high content of formic acid and tripropylaluminum compounds in G-Synthec must be considered because they are very corrosive and hazardous to the environment.