Analysis of emissions and combustion of typical biofuels generated in the agroindustry sector of Rio Grande do Sul State – Brazil: Bio75, syngas and blends

The importance of developing new alternative sources of energy meets the needs of some industrial sectors, such as rice processing. In Brazil, especially in the state of Rio Grande do Sul, the demand for electric and thermal energy is considerable since the state has more than 50 industries installed in this food sector. On the other hand, throughout the benefit of the rice grain, high amounts of husk are generated, with a capacity to produce synthesis gas. In addition, the treatment of the effluents generated during parboiling is rich in organic matter, which can generate high volumes of biogas through anaerobic treatment. The mixture of these gases can be applied in a spark ignition engines (SI), taking advantage of the bioenergy potential of the rice industries in Brazil. In addition to a renewable source of locally available energy, emissions of polluting gases can also be reduced. Accordingly, in this work, it was used the spark-ignition engine test operating with typical biogas and syngas compositions generated in the rice industries and their mixture, named Bio75 (included 75% of methane by vol.), syngas (with composition by vol. H₂ = 18.5%, CO = 26.5% CH₄ = 1.8%, CO₂ = 12.5%, N₂ = 40.7%), Blend 1 (included 15% of Bio75 and 85% of Syngas), Blend 2 (included 50% of Bio75 and 50% of Syngas), respectively. An important result that could be observed was that for both biogas and biogas-syngas mixture fuel the increase in excess ratio (λ) value from 1 to 1.25 leads to lower CO and NO_x emissions as well as an increase in indicated efficiency. Using fuel mix, even at low concentration, such as 15% by vol., Bio75 provided e_dv increase of 6.5% in the Blend 1. When the content of Bio75 in the mixture reach 50% (Blend 2) the increase of e_dv exceeds 14.5%.