Reducing the environmental impact of firing agricultural residues through Si-Al based additives

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cs

In light of the gradual transition toward sustainable and green economy, the valorization of various agricultural residues has been drawing more attention. The leftover products from agricultural processing can be easily turned into a CO2-neutral biofuel. The subsequent deployment of nutrient-rich ash as fertilizer helps to keep a closed cycle of minerals and promote circular economy. This practice, however, comes with its drawbacks: excessive particulate matter (PM) emissions being among the most alarming. The present study investigates the possibility of using Si-Al based additives to reduce PM emissions from firing sunflower husks, a commonly used biofuel. The tests have been conducted on a 25kW automatic pellet boiler with a bottom-feed retort burner. The initial results showed that when firing raw sunflower pellets, the PM emissions reached as high as 622 mg/m3. Most of the PM emissions can be attributed to KCl and K2SO4. It was shown before that aluminosilicates form refractory phases with potassium and hence inhibit its release to flue gas. The raw sunflower pellets have thus been enhanced with kaolin at ratios of 2.5%, 5% and 7.5% and a gradual decrease down to 85 mg/m3 was observed. No technical obstacles or secondary emissions were observed for any of the tested ratios. As such, the maximal kaolin addition should only be limited by the requirements of the particular appliance.

inorganic additives; agricultural residues; combustion; particulate matter

2025-12-05