Soot and char formation in the gasification of pig manure in a drop tube reactor

Biomass gasification offers a significant potential to close the loop of agriculture and many other activities that produce biomass residues. Pig manure, a residue produced in farms, has a huge pollutant potential due to its high production and chemical characteristics. It is necessary to take some control measures to decrease it, being pig manure gasification an interesting option. The present work studies the impact of the gasification temperature and atmosphere on the syngas composition (CO, H-2, CH4 and CO2) and formation of soot and char in the gasification of pig manure in a drop tube furnace. The temperature varied between 900 and 1200 degrees C, and the gasification atmospheres included mixtures of O-2/N-2, O-2/CO2/N-2 and O-2/H2O/N-2. The results revealed that i) the syngas H-2/CO ratio and its low heating value increase as the gasification temperature increases regardless of the gasification atmosphere; ii) the addition of H2O to the O-2/N-2 gasification atmosphere augments significantly the syngas H-2/CO ratio, but does not enhance its low heating value, while the addition of CO2 increases slightly the H-2/CO ratio, but significantly the heating value, iii) for the present reactor, the optimum operating conditions for the gasification of the pig manure in terms of syngas heating value and yield are a gasification temperature of 1200 degrees C and a gasification atmosphere composed of a mixture of O-2/CO2/N-2; and iv) soot yields increase as the temperature increases when gasification occurs in the O-2/N-2 and O-2/CO2/N-2 environments, remaining almost constant in the O-2/H2O/N-2 environment.