Synergetic effects in the co-pyrolysis of coal and petroleum residues:: influences of coal mineral matter and petroleum residue mass ratio

The influence of coal and mineral matter nature, and the coal/petroleum residue weight ratio, on the synergetic effects observed when coal and petroleum residues are copyrolysed has been studied. Two coals (Samca, a subbituminous one, Figaredo, a bituminous one, and a demineralised Samca coal) and three-coal/petroleum residue ratio (70/30, 50/50 and 40/60) have been used. Pyrolysis runs were carried out at analytical scale, by pyrolysis-gas chromatography in a pyroprobe 1000 CDS at 900 degrees C and at atmospheric pressure. Synergetic effect on the yield of the main pyrolysis products has been evaluated and discussed with attention focused on valuable feedstock petrochemical products such as light olefines and light aromatic compounds. It is concluded that the intensity of the synergetic effects depends on the coal nature. In the Samca coal with petroleum residue mixtures, the increase in petroleum residue ratio promotes the production of light olefins, disfavouring the production of aromatic compounds. In contrast, for the Figaredo coal, petroleum residue ratio has not a significant influence on the synergetic effects. Coal mineral matter seems to play a negative effect on synergetic effects since an increasing of synergetic effect in light olefins and BTX has been observed after demineralisation of the Samca coal. However, this effect could be attributed to both, the removing of the mineral matter and the changes produced in the porous structure of coal by the acid treatment. (C) 2000 Elsevier Science B.V. All rights reserved.