Release of Sulfur and Chlorine Gas Species during Combustion and Pyrolysis of Walnut Shells in an Entrained Flow Reactor

The release behavior of sulfur and chlorine compounds into the gas phase of walnut shell particles (WNS) is studied with an entrained flow reactor. Experiments are carried out in nitrogen (N2), carbon dioxide (CO2) atmosphere and under air and oxy-fuel conditions at different temperatures (T = 1000-1300 degrees C) and stoichiometries (lambda = 0.8-1.1). A total of 98.7% of fuel-bound sulfur volatilizes as sulfur dioxide (SO2), carbonyl sulfide (COS) and hydrogen sulfide (H2S) in the gas phase in N-2 atmosphere at 1000 degrees C. As hydrogen chloride (HCl), 37.0% of the chlorine is released at this temperature. In CO2 atmosphere, a similar total release of sulfur and chlorine is observed (1000 degrees C). With each temperature increment, the release of SO2, H2S and HCl in the gas phase decreases (N-2 and CO2 atmosphere). SO2 forms the major sulfur component in both atmospheres. In CO2 atmosphere, higher concentrations of COS were detected than in N-2 atmosphere. Air and oxy-fuel combustion conditions show significantly lower SO2, COS and HCl concentrations as in N-2 and CO2 atmosphere. No H2S is detected in the gas phase during any of the combustion trials.

Automated summary

The release behavior of sulfur and chlorine compounds from walnut shell particles was investigated using an entrained flow reactor. The experiments were conducted under different atmospheres and conditions. The results showed that the majority of fuel-bound sulfur volatilizes as sulfur dioxide, carbonyl sulfide, and hydrogen sulfide in nitrogen atmosphere at 1000 degrees C. Hydrogen chloride is released as HCl at a lower percentage. Similar results were observed in carbon dioxide atmosphere. The release of sulfur and chlorine decreases with increasing temperatures in both atmospheres.