Heidi S. Nygård Associate professor alongside PhD student Sepideh Niazi

The paper has been published

The first scientific, peer-reviewed article from ABC-Salt was published by the NMBU team in August 2020 – Hydrolysis of eutectic compositions in the ZnCl2:KCl:NaCl ternary system and effect of adding ZnO (Journal of Molecular Liquids). 

The published work is related to Task 3.2 – Molten salt selection in WP3 – primary liquefaction. 

The work is part of the PhD work of Sepideh Niazi, supervised by associate professor Heidi S. Nygård and co-supervised by professor Espen Olsen.

What were the findings?

The first technical step of the value chain in ABC-Salt is liquefaction of biomass in molten salts. 

An originality of this concept is to perform the liquefaction step at mild conditions (~200°C, atmospheric pressure), and it is therefore essential that the selected salt(s) have low melting points. 

The objective of Task 3.2 is to identify and characterize suitable molten salts.

During the initial screening of molten salts, ZnCl2:KCl:NaCl was found to be the most promising candidate for ABC-Salt. This ternary mixture is non-toxic, non-flammable, has a relatively low melting point and is stable at even higher temperatures compared to other ternary mixtures.

In the publication, Niazi has investigated the properties of four different compositions of ZnCl2:KCl:NaCl (Salt #1: 60:20:20 mol%, Salt #2: 59.5:21.9:18.6 mol%, Salt #3: 52.9:33.7:13.4 mol%, Salt #4: 44.3:41.9:13.8 mol%).

Experiments have been performed to measure melting points, thermal stability (TGA studies) and hydrolysis. Hydrolysis could be an issue if the salt is in contact with water, because this can lead to the formation of undesired gases like HCl. 

In total, Salt #4 seems to have the most promising properties relevant for thermochemical conversion of biomass. It has a relatively low melting point (~205 °C), the highest thermal stability (~0.2% mass loss at 500 °C) and exhibit the least tendency to form HCl during hydrolysis experiments. In order to avoid HCl formation completely, it is advised to keep the reaction temperatures below 400 °C and/or add ZnO as a hydrolysis inhibitor.

You can view the full paper by clicking this link.

PhD student Sepideh Niazi working hard in the lab