In this paper, the
effect of temperature, adsorption bed height,
and initial mercury concentration under oxy-fuel combustion on mercury
adsorption by 1% NH
4
Cl-modified biomass char was studied.
Modification enriched the pore structure of biomass char and increased
the number of surface functional groups. Higher temperature would
lead to the destruction of van der Waals and reduce the adsorption
efficiency, while the change of adsorption bed height had no obvious
effect. Adsorption thermodynamics shows that the mercury removal process
is a spontaneous exothermic process. The increase of initial mercury
concentration would increase the driving force of mercury diffusion
to the surface and improve the adsorption capacity. Meanwhile, three
kinetic models including the intraparticle diffusion model, pseudo-first-order
model, and pseudo-second-order model were applied to explore the internal
mechanism of mercury adsorption by biomass char. The results showed
that the pseudo-first-order model and pseudo-second-order model could
accurately describe the adsorption process, which meant that the progress
of external mass transfer played an important role in the adsorption
of mercury while chemical adsorption should not be ignored. The intraparticle
diffusion model indicated that internal diffusion was not the only
step to control the entire adsorption process and did not have an
inhibition on mercury removal. Higher initial mercury concentration
would promote the external mass transfer progress and chemical adsorption
progress. In addition, higher temperature inhibited the external mass
transfer, which was not conducive to the adsorption of mercury.