Wet Pre-treatment Methods in Macroelements Recovery from Fly Ash Combined with Acid Leaching

abstrakt

angličtina

Fly ash (FA), as a mass-produced secondary material (coal combustion product) since the middle of the last century, reached up to 30–40 % to be recycled and reused. One of the most auspicious applications of FA in the following decades possibly appears to be a raw material base – the source of macro- and microelements. This paper summarizes wet types of FA pre-treating techniques to obtain the maximum leachability of macro- elements, such as Al, Fe and Ti in the process of acid leaching. FA pre-treatment or chemical activation is the single key to increase the efficiency of separated elements. In this research, the wet experiment was based on FA pre-leaching in hydrochloric acid solution (1–5 wt. %). Both high-temperature (HTFA) and fluidized-bed fly and bottom ash (FFA. FBA) were the aims of the study. In the case of FBA and FFA, this reaction led to lower the total alkaline content, esp. reactive calcium oxide, as a result of flue gas desulphurization. The lower free lime content brings a positive effect, while the leachability of Al and Fe increased 2–4 times. Secondary, the grain surface after deposition in HCl solution changed by the meaning of the creation of new pores, as observed via SEM. Based on experimental data, taking into account the economic ratio and the increase in performance, the use of dilute (1 wt. %) HCl in a molar excess of 30 % to free CaO with a deposition time of 10–30 min at room temperature and constant stirring appears to be the most suitable conditions. On the other hand, in the case of HTFA samples which contain only a small amount of total alkaline content, it is much more advantageous to use more concentrated solutions so that the glass-covered surface of the particles is disturbed and the extraction medium can penetrate the resulting defects and dissolve selected elements. To conclude, it can be evaluated that the extraction efficiency in the case of FFA and FBA increased 2–4 times, thus achieving a total leachability of up to 85 % of iron and more than 50 % of aluminum in a single-phase extraction into sulfuric acid at room temperature. In the two-stage extraction, the leachability reached up to 95 % Fe and 92 % Al.

fly ash, fly ash utilization, macroelements recovery, acid leaching

MARKO, M.; OPRAVIL, T.; ŠOUKAL, F.; POŘÍZKA, J.

27. 11. 2020

Vysoké učení technické v Brně, Fakulta chemická, Purkyňova 464/118, 612 00 Brno

Brno

978-80-214-5920-0

Studentská odborná konference - CHEMIE JE ŽIVOT - sborník abstraktů

první

100

101

1

https://www.fch.vut.cz/vav/konference/sok/vystupy/sbornik-abstrakty-konference-2020-pdf-p198641