Research paperCatalytic conversion of residual fine char recovered by aqueous scrubbing of syngas from urban biomass gasification

- Char containing scrubbed tars was produced from the urban biomass gasification.
- Oxidation of tars and biochar was enhanced by the matrix metals of char.
- Addition of biochar ash led to CO/CO2 molar ratios higher than 1.
- Adding Fe improved the rate; heat liberated but decreased the CO/CO2 molar ratio.
- Adding BM (Ca-phosphate) also increased rate and improved the CO/CO2 molar ratio.

Conversion of carbon contained in the solid residues (tars + biochar) derived from urban biomass gasification named herein TC would allow enhancing the yield of carbon species (CO/CO2) in synthetic gas. For this purpose, three low cost materials have been tested as possible catalysts: iron species (reduced Fe), bone meal (BM), and ashes (ash) recovered from biochar complete oxidation. The parametric study used the following as variables: air GHSV, onset of reaction temperature, reaction time to optimize CO/CO2 molar ratio and tar content in the produced gas. Results showed an autocatalytic effect of biochar leading to the catalytic conversion of approximately 78% of tars by the native metals contained in TC. The catalytic effect was further enhanced by adding Fe, BM, and extra ash. Addition of Fe catalyst resulted in significant heat generation (temperature increase of ca. 500 °C) and a twofold decrease in reaction time to consume all the carbon. Use of ash and BM as catalysts exhibit heat generation comparable to Fe, along with an improved reaction time, complete tars conversion and a CO/CO2 molar ratio to above 1.3 in the produced gas.