Browsing by Author "Stevens, Lee"
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- Co-liquefaction of wastes and coal mixtures to produce added value liquid compoundsPublication . Pinto, Filomena; Costa, Paula; Paradela, Filipe; Silva, Pedro; Meredith, Will; Stevens, Lee; Snape, ColinABSTRACT: Nowadays there is an increasing need to find alternative fuels to reduce the dependency on imported ones and to decrease the negative environmental impact of wastes accumulation. Plastics are an important components of urban biowaste, thus their conversion into liquid fuels, in mixtures with other solid fuels still remains an important research goal. After the large experience obtained from coal gasification, it was found that co-liquefaction of coal and wastes may be a good solution to produce liquid fuels and raw materials for several industries. Co-liquefaction of coal blended with biomass gave unfavourable results, but co-liquefaction of coal mixed with PE (polyethylene) wastes led to encouraging results. The results obtained showed that the rise of PE content in coal blends led to an increase in liquid yield. As the main objective was the formation of liquid products, the mixture of coal with 50 wt% of PE was selected, as substantial total liquid yields were obtained, while using significant coal content. This blend was used to study the effect of initial hydrogen pressure, reaction temperature and time on products yields, using Response Surface Methodology (RSM) approach. Liquid yields were most affected by reaction temperature and pressure. The rise of temperature decreased liquid yields, while pressure had a positive effect, but the interaction between these two parameters showed a negative influence. Theoretical equations were used to calculate total and direct liquids yield (%daf). Total liquids are the sum of the liquids directly recovered from the autoclave (direct liquids) and the liquids extracted from the solid product. Both the theoretical model and the experimental results showed that the highest total liquids yields were obtained at 380 ºC, 1.4 MPa and 90 minutes.
- Direct primary brown coal liquefaction via non-catalytic and catalytic co-processing with model, waste and petroleum-derived hydrogen donorsPublication . Fratczak, Jakub; Herrador, José M. Hidalgo; Lederer, Jaromír; Stevens, Lee; Uguna, Clement; Snape, Colin; Fuente, José L. Gómez de la; Andel, Lukás; Svoboda, Petr; Pinto, FilomenaABSTRACT: Direct coal liquefaction (DCL) seems to be a suitable way to convert low rank coals into liquid fuels, especially when problematic wastes are used together with this feedstock. It is also a solution to become energy independent for many countries which have significant coal resources and limited access to crude oil. The aim of this research was to investigate DCL process by the co-processing of brown coal with model-, petroleum- and waste-derived solvents. The brown coal with and without W, Fe and Mo metals supported on its surface was tested. Thirteen DCL tests with added hydrogen pressure were carried out in the autoclave. These tests were classified in two groups. First group covered reactions using model and petroleum-derived solvents (tetralin, 1-methylnaphthalene, light cycle oil (LCO), hydrotreated LCO, C9+ fraction and decalin) with non-impregnated brown coal. Then, LCO was chosen as solvent for carrying out three tests using the metals supported on coal. Finally, waste tires pyrolysis oil was used as a waste-derived solvent for other three tests with molybdenum supported on coal. For tests using LCO, the total amount of direct liquid and n-heptane soluble products was 20 wt% higher using metal covered brown coal in comparison to unmodified one. The test with the brown coal impregnated by 1% of molybdenum resulted in the best efficiency, thus this type of coal was chosen as a catalytic feedstock for the tests with waste tires pyrolysis oil.