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Gasification is a thermochemical process devoted to the production of syngas, starting from a solid fuel such as coal, biomass, or refuse-derived fuel (RDF). The gasification efficiency and the chemical composition of the produced syngas are strongly affected by the feedstock and the operating conditions of the process. Besides the direct use as a fuel for power generation, downstream applications of syngas for chemical production demand specific H2/CO ratios, as extensively reported in the literature. For this reason, in the present work, a comprehensive mechanistic approach is applied to the description of the coal gasification process, highlighting the sensitivity of key operating parameters on syngas quality. The solution of this multi-scale, multi-phase, and multi-component problem requires careful attention to the kinetics in the solid and the gas phase as well as the heterogeneous gas-solid reactions. The kinetic model is validated with experimental data obtained in updraft gasifiers (including the Sotacarbo pilot gasification plant), and the catalytic effects of ash on the reactivity of low-rank coals are also addressed and quantified. © 2015 American Chemical Society.

The combined production of dimethylether (DME) and electrical energy in Integrated Gasification Combined Cycle (IGCC) power plants is a very attractive option for exploiting the world's huge coal reserves achieving high efficiency and low pollutant emissions, as well as for enhancing the flexibility and economic performance of coal gasification plants. Besides being used for power generation in combined cycle plants, the clean synthesis gas produced by coal gasification processes can also be used as raw material for producing hydrogen, methanol, DME, and other chemicals. In particular, recent studies show the growing interest of DME as a new clean fuel for diesel engines, gas turbines, fuel cells, and household uses. This article concerns an energy and economic assessment of two different IGCC power plants integrated with a once-through DME synthesis process. In particular, the study has been carried out by examining two different solutions for the gasification process: one based on a dry-fed and the other on a slurry-fed entrained-flow gasifier. The energy assessment has shown that the DME production in IGCC power plants leads to a DME/coal energy conversion of ∼31—32 per cent and an electrical/coal energy conversion of ∼22—25 per cent. Overall, the solution based on the dry-fed gasifier exhibits the best exergy performance (50.8 versus 52.7 per cent). Finally, the economic analysis reveals DME production costs (6—6.5$/GJ) comparable with other premium fuels such as natural gas, liquefied petroleum gases, and so on.

With the aim to support the experimental tests in a gasification pilot plant, the thermal decomposition of coal, biomass and their mixtures has been carried out through a thermogravimetric analysis (TGA) and a simplified kinetic analysis. The TGA of pure fuels indicates the low reactivity of South African coal and the relatively high reactivity of Sardinian Sulcis coal during pyrolysis. Among the tested fuels, biomass (stone pine wood chips) is the most reactive one. These results fully confirm those obtained during the experimental tests in the gasification pilot plant. As for the fuel blends, the analysis shows that the synergic effects between the considered coals and biomass are negligible when they are co-pyrolyzed. The results of the analysis confirm that TGA could be very useful to generally predict the gasification performance and to optimize the experimental campaigns in pilot-scale gasification plants.

It is well known that coal gasification plants allows to produce a clean synthesis gas which can be used as a fuel in IGCC power plants and as a raw material in order to produce hydrogen, methanol, dimethylether (DME) and other chemicals. Recent studies show the growing interest of DME as a new clean fuel for diesel engines, gas turbines, fuel cells and household uses. In this paper, a comparative performance analysis of two different IGCC power plants integrated with a DME synthesis process has been carried out. In particular two different coal gasification processes (a dry-feed and a slurry-feed entrained-flow gasifiers) and the advanced liquid phase DME (LPDME™) synthesis process have been considered. The analysis has been carried out in order to evaluate the influence of the operating parameters of the DME synthesis section (pressure and purge gas recycle ratio) on both DME production and net power output. The performance assessment has shown that, according to both gasification process and DME synthesis parameters, the produced DME accounts for about 40–46% of the coal chemical energy, whereas the net power output of the IGCC-DS plant accounts for about 13–19%. Moreover, the performance assessment also has shown that the IGCC-DS power plants based on the slurry-feed gasification processes lead to an higher DME production and a corresponding lower power output with respect to the solutions based on the dryfeed gasifiers.Copyright © 2004 by ASME