Syngas production from biogas in a polygeneration process: Simultaneous partial oxidation and dry reforming in a piston engine

Abstract

This work experimentally investigates the fuel-rich combustion of CH4/CO2/O2 mixtures in a piston engine. The focus of the experiments is to determine suitable operating parameters in terms of stable engine operation, syngas production, CO2 conversion, and avoiding soot emissions. In particular, the spark timing, CO2 intake mole fraction, equivalence ratio, and compression ratio were varied. Results show stable spark-ignition operation over a wide range of the investigated parameters at a compression ratio of 10. Acceptable operation could be achieved within the spark timing limits of -38° to 10 °CA after top dead center, 7 to 27% CO2 in the inlet and equivalence ratios from 2 to 2.5. A maximum H2 yield of 62% could be achieved at an equivalence ratio of 1.9 and a CO2 intake mole fraction of 4% at a compression ratio of 4.5. Spark time advancing from -10 to -38 °CA enhanced the dry reforming reaction and increased the hydrogen yield per methane from 38 to 45%. A significant influence of compression ratio on the amount of soot in the product gas was observed, showing that higher compression ratios increase soot formation.