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Sewage sludge from wastewater treatment facilities needs to be treated before it can be disposed of. While it is typically processed through an anaerobic digestion process, sludge can also be a good feedstock for alternative fuel production. High-temperature steam gasification is a process that decomposes organic materials into synthesis gas (syngas) with a high hydrogen concentration. In this study, a lab-scale steam gasification system which converts sewage sludge into valuable syngas was developed and experimentally evaluated. This study specifically focuses on investigating the chemical kinetics of syngas generation and feedstock decomposition in a batch process. The syngas generation rates and concentrations of syngas constituents were measured, and changes in carbon balance during gasification were tracked with respect to time, which shows how reaction rates vary over time. It was found that variations in steam flow rates modified the gasification reactions both thermodynamically and hydrodynamically. The gasification processes were fitted into logistics curves to understand the effects of different steam flow rates. The results indicate that the chemical reaction velocity can be controlled to achieve optimum operating conditions, which potentially can reduce both processing time and steam consumption while maximizing the syngas yield. This study would contribute more to the complete understanding of the sewage sludge gasification processes and the kinetics of the gasification chemical reactions. [ABSTRACT FROM AUTHOR]

A steam gasification processes is an energy conversion pathway through which organic materials are converted to useful energy. In spite of the high energy content in organic waste materials, they have been mostly disposed of in landfills, which causes harmful environmental issues such as methane emissions and ground water pollution and contaminations. In this sense, organic solid waste materials are regarded as alternative resources for conversion to useful energy in the steam gasification process. In this study, three types of waste materials - municipal solid waste (MSW), used tires and sewage sludge - were used to generate syngas through the gasification process in a 1000 °C steam atmosphere. The syngas generation rates and its chemical compositions were measured and evaluated over time to determine the characteristics and dynamics of the gasification process. Also, carbon conversion, and mass and energy balances are presented which demonstrates the feasibility of steam gasification as a waste conversion pathway. The results show that the syngas contains high concentrations of H2, around 41-55% by volume. The syngas generation rate was found to depend on the carbon content in the feedstock regardless of the types of input materials. Comparing to the hydrogen production from water splitting that requires extremely high temperatures at around 1500 °C, hydrogen production by steam gasification of organic materials can be regarded as equally effective but requires lower system temperatures. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The main objective of this study is to investigate the characteristics of woody biomass conversion to syngas using a steam allothermal gasification process. The entering steam maintained at 877 °C and 1000 °C, respectively was used as the gasifying agent. A lab scale apparatus was built to perform the gasification experiment and the produced syngas was accurately analyzed using gas chromatography. The results clearly indicate that the syngas from steam gasification contains relatively higher H 2 concentrations, and the heating values of the syngas reach 9–10 MJ/m 3 . A thermodynamic equilibrium thermochemical model that accounts for the deposition of solid carbon as a function of the entering steam temperature and the steam to biomass molar ratio was developed. The model was successfully verified by experimental results. Based on the results of model, an optimal range of the steam to biomass molar ratio is recommended. [ABSTRACT FROM AUTHOR]

A mathematical model that describes a trailer scale biomass steam gasification system coupled with a solar collector heat source and a micro gas turbine is reported in this paper. This combined heat and power system is set to a prescribed output of 20 kW e and several system conditions have been optimized in a parametric study to minimize resource consumption rates. Biomass feeding rates under optimal conditions were found to range between 23 and 63 kg/h depending on the types of feedstock and other parameters. Water consumption is reduced through a condensation and recirculation process that is part of a heat recovery unit. Also, solar energy requirements have been reduced by means of a recuperator that extracts heat out of the combustion products. The overall system performance has been evaluated by a utilization factor which was found to range between 30% and 43%. The system has been compared to a baseline case of an air breathing gasification system of a similar scale. It was found that steam gasification produces the syngas with heating values over twice as high as those obtained by air gasification. Steam gasification also led to a 25% and 50% reduction in emission rates of contaminants like CO 2 and nitrogen oxides respectively relative to the baseline case. [ABSTRACT FROM AUTHOR]