Article révisé par les pairs
| Résumé : | The sulphur distribution among the char, oil and gas obtained after hydropyrolysis of a high-sulphur (4.3 wt%) and high-calcite (7.3 wt%) coal has been investigated. The chars were examined by scanning electron microscopy coupled with an energy dispersion analyser and by X-ray diffraction. The proportion of the combustible and non-combustible sulphur in the char has been determined. Hydrogen pressure promotes reaction with sulphur but the sulphur content of the chars increases from 3 to 4.5 wt% when the temperature is increased from 616 to 845 °C. This increase in sulphur is a consequence of the reaction between hydrogen sulphide, produced during hydropyrolysis of coal, with the alkaline-earth mineral matter to produce alkaline-earth sulphide. The SEM and X-ray diffraction images show that in the char formed at 780 °C the sulphur, calcium and magnesium are localized in the same compounds. This is not the case when hydropyrolysis is performed at lower temperature. Combustion of the chars produces only <0.6 S02 MJ-1 compared to 2.2 g S02 MJ-1 for untreated coal. X-ray diffraction has shown that the sulphur in the char is oxidized and fixed in the ashes mainly as CaS04 and also some as MgS04. Although sulphur remains partly in the chars after hydropyrolysis, 75% of it is non-combustible. The hydropyrolysis of a high-sulphur coal containing calcite, produces a char which may be used as a clean fuel. © 1982. |
