Abstract This study aims to assess methane (CH4) and carbon dioxide (CO2) concentrations in the ventilation systems of two coal mines (A and B) in the Santa Catarina coal deposit in southern Brazil (Paraná Basin, Bonito Formation), and estimate their greenhouse gas (GHG) emissions. The highest CH4 levels (1.8%) were recorded in strong methane emanation areas in mine A, below the lower explosive limit (5%). The IPCC-recommended methods significantly overestimated the methane emission (up to 80%) when compared to the experimental data measured for each mine. Application of an alternative method made it possible to estimate direct CO2 emissions, indicating that CO2 accounted for 22 to 77% of total GHG emissions. Carbon dioxide emissions are generally not included in GHG emission inventories, indicating that the coal industry underestimates the contribution of this gas. As such, it is recommended that the methodology used for these calculations be revised and that specific emission factors be applied for each mine. In order to improve the accuracy of inventories, more sampling needs to be carried out in all operational and abandoned mines.

We evaluated solid-state sensors (MOS) manufactured using nanostructured tin oxide (SnO2) obtained by different synthesis methods for selectivity, response and repeatability at different operating temperatures and methane concentrations. In addition, Zeolite 13X pellets were placed in front of the sensors to improve CH4 selectivity in the presence of CO2. The palladium doped sensor (1.4% w/w) showed the highest sensitivity at 80 ºC (83%) and shorter response times (16 s), whereas non-doped sensors exhibited the best sensitivity (78%) and response times (14 s) for those with smaller particle size (8 nm). Zeolite 13X pellets proved to be efficient at making the sensor more selective for CH4 in the presence of CO2.

Este trabalho apresenta correlações obtidas entre propriedades mecânicas, densidade e o estado de deterioração de postes de eucalipto novos e retirados de serviço. O estado de deterioração foi determinado por inspeções em campo de postes da rede de distribuição de energia elétrica no sul do Brasil. Postes em diferentes estados de deterioração foram retirados da rede para os ensaios de flexão estática e medidas de densidade. Os testes mecânicos indicaram que os valores médios da resistência a flexão e da rigidez decrescem com o estado de deterioração do eucalipto. Entretanto, verificou-se uma grande variação nessas medidas com diferentes classes de deterioração apresentando resistência mecânica residual similar. Esse comportamento pode ser explicado pela influência da densidade da madeira nas correlações entre propriedades mecânicas e o estado de deterioração dos postes. Madeiras menos densas podem apresentar baixa resistência mecânica residual mesmo sem apresentar sinais de deterioração. O estudo da caracterização da madeira de eucalipto indicou que o estado de deterioração avaliado pela inspeção em campo, por si só não é um bom indicativo para prever a durabilidade das estruturas de madeiras, fazendo-se necessária uma análise preliminar da densidade da mesma.

This paper presents the correlations obtained among mechanical properties, density and deterioration status of new eucalyptus poles and those removed from service. The deterioration status was determined in the field in sections of poles of the distribution of electric energy in southern Brazil. Poles in various status of deterioration were removed from the network for static bending tests and density measurements. The mechanical tests indicated that the average values of bending strength and stiffness decline with the deteriorating state of eucalyptus. However, there was a large variation in these measures with different classes of deterioration presenting similar residual mechanical strength. This behavior can be explained by the influence of wood density on the correlations between mechanical properties and the state of deterioration of the poles. Less dense woods can have residual mechanical strength low even without present signs of deterioration. The study of the characterization of eucalyptus wood indicated that the state of deterioration measured by field inspection alone is not a good indicator for predicting the durability of wood structures, making necessary a preliminary analysis of the density.