Bed Particle Layer Formation and Characteristics of Ilmenite Bed Particles Utilized in Fluidized Bed Combustion of Chicken Litter

TL;DR

This study examines how ilmenite bed particles form layers during the combustion of chicken litter, a phosphorus-rich biomass, in a fluidized bed system.

Contribution

The study reveals the unique layer formation on ilmenite bed particles when burning P-rich chicken litter, which differs from previous findings on woody biomass.

Findings

The initial layer formation is driven by Ca-rich particles reacting with the bed particles.

An outer layer of Ca, P, Mg, and K forms uniformly over the bed particle surface over time.

Fe migration from ilmenite is limited due to the uniform outer layer formed by the P-rich fuel.

Abstract

Despite extensive research on the bed particle layer
formation
and characteristics of ilmenite bed particles in fluidized bed combustion
and gasification of woody biomass (characterized by high Ca and K
content), a significant knowledge gap exists when P-rich fuels are
used. Chicken litter, as a P-rich biomass, presents a promising alternative
biomass for energy conversion processes. Therefore, this study aims
to investigate the bed particle layer formation and characteristics
of ilmenite bed particles during fluidized bed combustion of chicken
litter. The bed particle layer formation process and characteristics
for ilmenite bed particles utilized in a 5 kWth bubbling
fluidized bed combustion of chicken litter were studied in this work.
Bed samples were taken after 4, 8, 12, and 16 h from the start-up
and were analyzed via SEM/EDS. The findings highlighted that the initial
stage of bed particle layer formation is similar to what was observed
in fluidized bed combustion of woody biomass and is driven by the
reaction of fuel-derived Ca-rich particles with the bed particle,
leading to the formation of the inner layer. As time progresses, the
deposition of fuel-derived bed ash, containing mainly Ca, P, Mg, and
K, forms an outer layer that uniformly covers the entire bed particle
surface, irrespective of the bed particle’s surface morphologies.
Additionally, the outward migration of Fe from ilmenite bed particles
is significantly constrained when utilizing chicken litter, a Ca-
and P-rich fuel, due to the formation of a bed particle layer that
uniformly covers the bed particle surface.

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