Biomass fuels represent a renewable energy source, they are CO 2 neutral fuels, and their use reduces the consumption of fossil fuels and limits the emissions of SO x , NO x , and heavy metals. They are used in pyrolysis, gasification, combustion, and co-combustion. The devolatilization is a fundamental mechanism in all these processes, especially for high volatile matter fuels. In this work, the devolatilization of biomass fuels (of different origin, properties, and composition) and biomass components is studied coupling thermogravimetric (TG) analysis with infrared spectroscopy. The characteristic temperatures are determined for the main devolatilization steps and compared for all fuels. A bituminous coal and a paper sludge are also studied for comparison. Light gases released (CO, CO 2 , H 2 O, CH 4 , CH 3 OH, HCOOH) are detected, whereas more complex organic (hydrocarbon and oxygenated) compounds are grouped because of the large variety of volatile species released in a narrow range of temperature. The weight loss of biomass fuels is related to their chemical composition (i.e., considering the devolatilization behavior of cellulose, hemicellulose (xylan), and lignin in the same operating conditions). The aim of the work is to apply a summative law for the TG results (validated in previous experimental and literature works) to obtain the chemical composition of biomass fuels and to validate and extend a summative law for the FTIR profiles of volatile species released. Calculated values obtained using this method are in good agreement with the experimental results. Therefore, the validation of this correlation allows the prediction of the devolatilization of biomass fuels considering the initial chemical composition. This is useful for practical applications, plant designing, handling, and modeling.

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Coal gasification is a versatile process to convert a solid fuel in syngas, which can be further converted and separated in hydrogen, which is a valuable and environmentally acceptable energy carrier. Different technologies (fixed beds, fluidized beds, entrained flow reactors) are used, operating under different conditions of temperature, pressure, and residence time. Process studies should be performed for defining the best plant configurations and operating conditions. Although "gasification models" can be found in the literature simulating equilibrium reactors, a more detailed approach is required for process analysis and optimization procedures. In this work, a gasifier model is developed by using AspenPlus as a tool to be implemented in a comprehensive process model for the production of hydrogen via coal gasification. It is developed as a multizonal model by interconnecting each step of gasification (preheating, devolatilization, combustion, gasification, quench) according to the reactor configuration, that is an entrained flow reactor. The model removes the hypothesis of equilibrium by introducing the kinetics of all steps and solves the heat balance by relating the gasification temperature to the operating conditions. The model allows to predict the syngas composition as well as quantify the heat recovery (for calculating the plant efficiency), "byproducts", and residual char. Finally, in view of future works, the development of a "gasifier model" instead of a "gasification model" will allow different reactor configurations to be compared. © 2009 American Chemical Society

Fundamental information can be obtained by comparing the behavior of different classes of solid fuels (low-and high-volatile matter coals, biomass fuels, residues, wastes, and plastics) in oxidizing and inert thermogravimetric runs. Different mechanisms can be recognized and attributed to devolatilization, char oxidation, and direct oxidation. The direct oxidation of the fuel can be favored with respect to the traditional devolatilization/char oxidation scheme depending on the conditions used and the characteristics of the fuel. Oxygen enhances the thermal devolatilization of the fuel and the reactivity of the produced char. The reactivity of all fuels are quantified by defining characteristic temperatures of each mechanism and providing kinetics for all steps. Also, the effect of the operating conditions are evaluated. Results obtained in this work represent a significant set of data on very different solid fuels, useful for modeling purposes, for practical system handling (grate furnaces or fixed-bed combustors, operating in conditions similar to this study), for safety of fuel stockpiles, and for investigations on ignition and char reactivity.