Steam gasification of sewage sludge for synthesis processes

The paper presents measurement results of a gasification test run. Municipal sewage sludge from a digestion tower is gasified in an advanced dual fluidized bed reactor system. Steam is used as gasification agent and an olivine-limestone mixture as bed material. The fuel analysis shows a very high ash content and a low heating value of the dried sewage sludge. In addition, a significant amount of nitrogen in the fuel is present, leading to a high ammonia content in the product gas.Sintering effects caused by the high ash content do not occur. Thus, a gasification process without limitation is achieved. The fuel input is located in the lower gasification reactor operating as bubbling fluidized bed, whereas the upper gasification reactor is designed as a column of turbulent fluidized zones for tar cracking. The results show an efficient in-situ tar reduction. With a look on the product gas composition a comparatively high carbon dioxide and a low carbon monoxide content is surprising. It is obvious that an iron oxide reduction of the initial fuel ash occur in the gasification reactor. In addition, it is assumed that the significant iron content in the fuel ash also leads to a transport of oxygen from the combustion reactor to the gasification reactor. Thus, carbon monoxide and hydrogen are oxidized in the gasification reactor by the circulating iron-rich ash particles (chemical looping effect).FFG - Österr. Forschungsförderungs- gesellschaft mbH4351

Syngas for biorefineries from thermochemical gasification of lignocellulosic fuels and residues—5 years’ experience with an advanced dual fluidized bed gasifier design

In many processes proposed for biorefineries, recycling procedures, and industrial or agricultural production processes, residue is generated which could be further transformed by thermochemical conversion via gasification. The technology of dual fluidized bed steam gasification is capable of producing a valuable product gas out of such residue. The generated nitrogen-free product gas can be used for heat and power production and is suitable for separating gases (e.g. hydrogen). However, if the product gas is cleaned, its use as syngas is more beneficial for manufacturing renewable chemical substances, like synthetic natural gas, methanol, Fischer–Tropsch liquids, or mixed alcohols. This paper presents the results of experimental research from gasification test runs of different biogenic fuels, carried out with an advanced 100 kW pilot plant over the last 5 years at TU Wien. The focus is to provide an overview of measured results validated by mass and energy balances and to present key calculated performance indicating key figures of the test runs. In this way, the influence of various operational parameters and the composition of the product gas are evaluated. The presented results form the basis for the proper design of suitable gas-cleaning equipment. Subsequently, the clean syngas is available for several synthesis applications in future biorefineries.Austrian Climate and Energy Fund (ReGas4Industry

The impact of gasification temperature on the process characteristics of sorption enhanced reforming of biomass

Especially carbon-intensive industries are interested in a decarbonization of their processes. A technology, which can contribute to a significant reduction of the carbon footprint, is the so-called sorption enhanced reforming process. The sorption enhanced reforming process uses a dual fluidized bed reactor system with limestone as a bed material for the thermochemical conversion of biomass into a valuable nitrogen-free product gas. This product gas can be used for further synthesis processes like methanation. The dependency of the product gas composition on the gasification temperature is already a well-known fact. Nevertheless, detailed investigations and models of the effect on elemental balances (especially carbon) of the process are missing in the literature and are presented in this work. Therefore, previously published data from different pilot plants is summarized and is discussed on a mass balance. Based on this information, investigations on the product gas equilibrium composition are presented and conclusions are drawn: it can be shown that the sorption enhanced reforming process can be divided into two sub-processes, namely “carbonation dominated sorption enhanced reforming” and “water-gas shift dominated sorption enhanced reforming.” The sub-process carbonation dominated SER is characterized by a high deviation from the water-gas shift equilibrium and a nearly constant CO content in the product gas over gasification temperature (< 700 °C). The sub-process water-gas shift dominated SER can be identified by a steep increase of the CO content in the product gas over temperature and nearly equilibrium state of the water-gas shift reaction (700–760 °C).Austrian Climate and Energy Fun

Dual fluidized bed biomass gasification: Temperature variation using pure CO2 as gasification agent

In many industrial processes, the climate-damaging gas CO2 is produced as undesired by-product. The dual fluidized bed biomass gasification technology offers the opportunity to solve this problem by using the produced CO2 within the process as gasification agent. Therefore, a 100 kW pilot plant at TU Wien was used to investigate the use of CO2 as gasification agent by converting softwood as fuel and olivine as bed material into a product gas. A temperature variation from 740 to 840°C was conducted to investigate the change of the main product gas components over the gasification temperature. With increasing temperature, CO and H2 increased and CO2 decreased. Additionally, another parameter variation was conducted, where the typically used gasification agent steam was substituted stepwise by CO2. Thereby, the amount of CO and CO2 increased and the content of H2decreased. These trends resulted in a declining H2/CO ratio and a decreasing lower heating value when CO2 was increased as gasification agent.European Union’s Horizon 202073821

Layer Formation on K-feldspar in Fluidized Bed Combustion and Gasification with bark and chicken manure

The final publication is available via https://doi.org/10.1016/j.biombioe.2019.05.020.The layer formation on bed materials in fluidized bed applications is an often-studied phenomenon where most work has focused on combustion but some studies on gasification exists, and direct comparisons of layer formation in combustion and gasification have been performed occasionally. The present work provides a thorough comparison of layer formation during combustion and gasification with K-feldspar as bed material using different feedstocks, namely Ca-rich bark; Ca- and P-rich chicken manure; and an admixture of chicken manure with bark. The feedstocks are tested in a 5 kW bubbling fluidized bed combustor and a 100 kWth dual fluidized bed steam gasifier. A reference bed material sample from the industrial biomass combined heat and power plant (CHP) in Senden is used as example for the gasification of bark-rich logging residues. The formed bed particle layers on the bed material surface are characterised using combined scanning electron microscopy and energy-dispersive X-ray spectroscopy; area mappings and line scans are carried out for all samples. The obtained data shows no essential influence of operational mode on the layer formation process. During the combustion and gasification of Ca-rich feedstocks a layer rich in Ca formed while K is diffusing out of the layer. The use of Ca- and P-rich feedstocks inhibited the diffusion of K and a layer rich in Ca and also P formed. The addition of P to the feedstock by chicken manure therefore changed the underlying layer formation processes.FORMAS MobilityBioenergy2020

Continuous hydrodeoxygenation of liquid phase pyrolysis oil with biogenous hydrogen enriched synthesis gas for fuel production

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