Air-Blown Entrained Flow Gasification of Biocoal: Gasification Kinetics and Char Behavior

Abstract

Air-blown entrained flow gasification of biomass has the potential of overcoming tar-related problems that occur in fixed bed or fluidized bed gasifiers. For designing entrained flow reactors (EFR), specific information on the gasification behavior of the fuel is required. Therefore, experiments with biocoal from the hydrothermal carbonization of different feedstock (beech, biogenic residuals, municipal waste, and green waste) are performed under EFR conditions and compared to lignite. Pyrolysis chars from biocoals and lignite are obtained in EFR at 900−1300 °C for a reactivity analysis. Intrinsic reaction rates of the char reactions with CO 2 , H 2 O and O 2 are measured in a thermogravimetric analyzer. Compared to lignite, chars from biocoal are less reactive due to smaller surface areas and less catalytic ash constituents. Char samples from gasification with varying air-tofuel equivalence ratios, λ, and residence times are sampled from an autothermal gasifier and from a laboratory-scale EFR at 900− 1300 °C. Carbon and overall conversions are determined by means of the ash-tracer method. The evolution of particle size, surface area, and density of the chars with increasing conversion is measured, and simple model approaches are applied to describe the observed behavior. The results show that fuel properties and gasification conditions significantly influence the prevailing reaction regimes and require particular consideration.

Study on Char-Ash-Slag-Liquid Transition and Its Effect on Char Reactivity

“…As an efficient and clean coal conversion technology, low-rank coal gasification has attracted increasing attention. − It is widely used in many fields such as chemical synthesis and gas production. Entrained flow gasification is considered as the most advanced gasification technology due to its flexible adaptability of gasification feedstock. − Its typical feature is the formation of liquid slag . The ash phase was changed due to the ash melting under such a high temperature, and consequently, it influenced the gasification reactivity.…”

Morphological Evolution of a Single Char Particle with a Low Ash Fusion Temperature during the Whole Gasification Process

“…The synthesis gas is the main material for producing chemicals and fuels for integrated gasification combined cycle (IGCC) power generation . Entrained-flow gasifier is operated with slag tap; thus, the transition of char slag not only affects the carbon conversion but the flow properties of molten slag. , While the carbon conversion efficiencies of gasifiers for high-ash-content coals are distinctly decreased, the residual carbon in slag is high . This demonstrated that, at high operating temperatures, the inorganic melt phase engulfs the organic portion, rendering the organic component unreactive.…”