Effect of different concentrations of O2 under inert and CO2 atmospheres on the swine manure combustion process

- The study of the oxy-combustion of manure was carried out.
- Two different atmospheres were evaluated in this work: Ar/O2 and CO2/O2.
- The kinetics of the process were computed by the Kissinger-Akahira-Sunose method.
- The gaseous products released during the process were evaluated by TGA-MS.

The oxy-fuel combustion of swine manure has been evaluated by thermogravimetric-mass spectrometric analysis. Manure samples showed a two-stage decomposition profile. The first stage is related to devolatilization of the sample and the second stage involved oxidation of the char formed in situ. Replacement of the inert carrier gas by CO2 did not seem to affect the first stage. However, this change in carrier gas delayed the oxidation of the samples during the second stage. This finding is mainly attributed to the slower transfer of thermal energy to the fuels in CO2/O2 atmospheres. The increase in the oxygen partial pressure in the reaction medium had a marked effect on the oxidation stage by shifting the process to lower temperatures (from 514 to 478 °C and from 525 to 475 °C for Ar/O2 and CO2/O2, respectively). The kinetics of the process were evaluated by the integral iso-conversional method of Kissinger-Akahira-Sunose (KAS). The two aforementioned stages were clearly identified as two regions of apparent activation energy were obtained. A similar profile was found for the gaseous products released in the process in both atmospheres, as evidenced by a distribution with two emission peaks, which is consistent with the two combustion regions. However, the formation of light products such as H2, CO and CH4 was favored on using high proportions of CO2 (∼80 vol.%).

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