Nitrogen Uptake on Coal Char at Ambient Temperature and the Effect of the Uptake on Ultimate Analysis

Abstract

The exposure of Taiheiyo and Blair Athol coal chars to air at ambient temperature led to the adsorption of an appreciable amount of N 2 on the coal chars. Some of N 2 thus adsorbed still remained on the chars even after purging the chars with He gas flow. The amount of remaining N 2 was determined by the subsequent temperature-programmed desorption experiment, and it was found that the remaining N 2 accounted for a substantial portion of nitrogen content determined by ultimate analysis using an instrumental analyzer for each coal char. In other words, the amount of nitrogen determined by an instrumental analyzer is overestimated. Accordingly, to obtain the correct nitrogen analysis value, it is necessary to remove such adsorbed N 2 . Evacuation of coal chars at 423 K for 5 h prior to the analysis is enough for this purpose.

Formation of HNCO, HCN, and NH3 from the pyrolysis of bark and nitrogen-containing model compounds

“…However, nitrogen gas from air has been found to adsorb on chars derived from coal [13] and phenol formaldehyde resin [14] as well as on other carbon-rich solids such as molecular sieving carbon and activated carbon fiber [14]. The adsorbed nitrogen contributes to the total nitrogen content measured by instrumental analyzers based on combustion of the solid samples [13,14].…”

“…The adsorbed nitrogen contributes to the total nitrogen content measured by instrumental analyzers based on combustion of the solid samples [13,14]. This is why this method can give overestimated nitrogen concentrations [13,14]. Nitrogen gas is expected to adsorb on biomass chars as well, and due to the low nitrogen concentrations in biomass such adsorbed nitrogen can contribute significantly to the analyzed concentrations.…”

Evolution of Inherent Oxygen in Solid Fuels during Pyrolysis

“…Nitrogen and sulfur occupy minor composition in solid, but their oxides are defined as environmental poisons. Transformation of nitrogen and sulfur during thermal conversions has been investigated in the literature. − Trace elements, such as alkali and alkaline earth metals, which usually form in salt, can affect the quantity and quality of pyrolysis products. − Many researchers focused on the environmental impact of heavy metal in solid. , …”