Freisetzung anorganischer Spezies bei der thermochemischen Umwandlung biogener Festbrennstoffe

The thermochemical use of solid biomass will be important for the energy production in the future. If possible, all types of biomass, e.g. wood and residues of cereal production should be used. Integrated Gasification Combined Cycle (IGCC) seems to be a promising concept with efficiencies > 55%, in which the product gas can be used for electrical power generation and heat production or for the production of synthesis gas. High amounts of alkali, sulphur, and chlorine compounds in the flue gas can be problematic. These pollutants can cause slagging and fouling in the boiler, catalyst deactivation or high temperature corrosion of iron materials and nickel-base alloys. In order to develop technical measures to reduce the amount of alkalis, sulphur and chlorine in the flue gas, an increased understanding of the release behaviour of these pollutants during thermochemical conversion of biomass is necessary. In the present work, the influence of fuel composition, temperature, and oxygen/fuel ratio on the release of trace elements during combustion and gasification of woody and herbaceous biomass was investigated. Therefore experiments were performed in a tube furnace and in a lab scale fluidized bed reactor. The experiments were supplemented by thermodynamic equilibrium calculations and a thermochemical model of the Värnamo gasifier. The fuel ashes were investigated chemically, by XRD, STA, and Knudsen Effusion Mass Spectrometry (KEMS). Molecular Beam Mass Spectrometry (MBMS) was used for the semi-quantitative analysis of the hot flue gas. This work provides important insights into the influence of fuel composition, ash phases, temperature, and oxygen/fuel ratio on the release of inorganic pollutants

Release of Inorganic Trace Elements During Gasification of Wood, Straw and Miscanthus

The release of alkali metals, chlorine, sulphur and heavy metals during gasification of four different types of biomass was investigated. The samples were two types of wood (clean and waste wood), miscanthus, and straw. Experiments were conducted in two different setups; in a tube furnace which could be considered as batch experiments, and in an atmospheric lab scale fluidised bed reactor with continuous fuel feed. Molecular beam mass spectrometry was used for on-line analysis of the hot gas. The experimental results reveal that the release of inorganic species like HCl, KCl and H2S is strongly dependent on other inorganic constituents in the samples, e.g. Si and Ca. In general, the release from herbaceous biomass is much higher than from woody biomass. With the exception of zinc released from miscanthus at temperatures above 900 degrees C, no heavy metals could be detected. The measurements were accompanied by equilibrium calculations using FactSage 5.5 and the FACT database which are in relatively good agreement with the experimental results. (C) 2011 Elsevier Ltd. All rights reserved