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The pyrolysis of a sludge produced in the waste water treatment plant of an oil refinery was studied in a pilot plant reactor provided with a system for condensation of semivolatile matter. The study comprises experiments at 350, 400, 470 and 530 °C in nitrogen atmosphere. Analysis of all the products obtained (gases, liquids and chars) are presented, with a thermogravimetric study of the char produced and analysis of main components of the liquid. In the temperature range studied, the composition of the gas fraction does not appreciably vary. In the liquids, the light hidrocarbon yield increases with increasing temperature, whereas the aromatic compounds diminish. The decomposition of the solid fraction has been analysed, finding a material that reacts rapidly with oxygen regardless of the conditions it is formed. TEP-6686 project funded by the Operational Program FEDER and FSE of Andalusia 2007-2013. Ministry of Education and Science (Spain): CTQ2008-05520. Valencian Community Government (Spain): PROMETEO/2009/043 and ACOMP2011/224.

Thermogravimetric analysis (heating rates between 5 and 15 K/min up to 873 K) has been carried out in air of chars, generated from the pyrolysis of wood and wood impregnated with (NH 4 ) 2 HPO 4 and (NH 4 ) 2 SO 4 (5%, dry wood basis) which are widely used as flame retardants. Salts significantly alter the char reactivity, but a mechanism consisting of three parallel reactions always provides a good description of the measurements. The estimated activation energy and reaction order of the most important combustion reaction, which causes the release of about 71–80% of the volatile matter, are nearly the same for untreated and (NH 4 ) 2 SO 4 impregnated samples (about 190–200 kJ/mol and 0.86). A lower activation energy (about 150 kJ/mol) and a higher reaction order (1.35) are obtained for (NH 4 ) 2 HPO 4 treatments. Scanning electronic microscope (SEM) images show significant modifications in the morphological structure of both wood and char as a consequence of salt impregnation.

The increasing environmental concern caused by the use of fossil fuels and the concomitant need for improved combustion efficiency is leading to the development of new coal cleaning and utilisation processes. However, the benefits achieved by the removal of most mineral matter from coal either by physical or chemical methods can be annulled if poor coal combustibility characteristics are attained. In this work a high volatile bituminous coal with 6% ash content was subjected to chemical demineralisation via hydrofluoric and nitric acid leaching, the ash content of the clean coal was reduced to 0.3%. The original and treated coals were devolatilised in a drop tube furnace and the structure and morphology of the resultant chars was analysed by optical and scanning electron microscopies. The reactivity characteristics of the chars were studied by isothermal combustion tests in air at different temperatures in a thermogravimetric system. Comparison of the combustion behaviour and pollutant emissions of both coals was conducted in a drop tube furnace operating at 1000 °C. The results of this work indicate that the char obtained from the chemically treated coal presents very different structure, morphology and reactivity behaviour than the char from the original coal. The changes induced by the chemical treatment increased the combustion efficiency determined in the drop tube furnace, in fact higher burnout levels were obtained for the demineralised coal., Work carried out with a financial grant from the European Coal and Steel Community (Project 7220-EA-017).