Investigation of the Formation of Coherent Ash Residues during Fluidized Bed Gasification of Wheat Straw Lignin

Abstract

Thermal conversion of ash-rich fuels in fluidized bed systems is often associated with extensive operation problems caused by the high amount of reactive inorganics. This paper investigates the behavior of wheat straw lignin—a potential renewable fuel for dual fluidized bed gasification. The formation of coherent ash residues and its impact on the operation performance has been investigated and was supported by thermochemical equilibrium calculations in FactSage 7.3. The formation of those ash residues, and their subsequent accumulation on the surface of the fluidized bed, causes temperature and pressure fluctuations, which negatively influence the steady-state operation of the fluidized bed process. This paper presents a detailed characterization of the coherent ash residues, which consists mostly of silica and partially molten alkali silicates. Furthermore, the paper gives insights into the formation of these ash residues, dependent on the fuel pretreatment (pelletizing) of the wheat straw lignin, which increases their stability compared to the utilization of non-pelletized fuel.

Comparative life cycle assessment of first‐ and second‐generation bio‐isobutene as a drop‐in substitute for fossil isobutene

“…Concerning by‐product utilization and the approaches to account for in LCA, scenario 7 applies an energy allocation approach based on the lower heating value of IBN (44.8 MJ/kg) 36 and lignin (19.5 MJ/kg dry ) 37 . This resulted in an allocation factor of 38% for IBN and 62% for the by‐product lignin.…”

“…Concerning by-product utilization and the approaches to account for in LCA, scenario 7 applies an energy allocation approach based on the lower heating value of IBN (44.8 MJ/ kg) 36 and lignin (19.5 MJ/kg dry ). 37 This resulted in an allocation factor of 38% for IBN and 62% for the by-product lignin. In scenario 8, it is assumed that all lignin is used for energy production purposes outside the IBN production system and electricity and thermal energy are substituted for natural gas elsewhere.…”