Preliminary Comparative Characterization of Low-Rank Lignite Powders Based on Physicochemical Properties and Particle Size

Low-rank lignites remain potential feedstocks for hydrogen production through steam gasification, although their high moisture and ash contents impose considerable energy and operational constraints. This study compared three lignite samples from different mining sources using ultimate analysis, moisture and ash determination, bomb calorimetry, and particle size analysis. Three monthly samples from each source were analysed, and the results are expressed as mean ± standard deviation on an as-received basis. All lignites contained approximately 42 wt.% moisture and 20–23 wt.% ash. Sample 2 exhibited the most favourable combination of properties, with the highest carbon (22.07 ± 0.49 wt.%) and hydrogen (2.47 ± 0.03 wt.%) contents, the lowest ash content (20.05 ± 0.98 wt.%), and the highest measured heating value (8.01 ± 0.16 MJ kg−1). It also had a lower reported fraction retained on the 0.20 mm sieve than Sample 1. Sample 3 showed the lowest moisture content (41.77 ± 0.25 wt.%) and intermediate overall characteristics. The resulting suitability ranking was Sample 2 > Sample 3 > Sample 1. This ranking provides a preliminary basis for selecting lignites for subsequent gasification experiments and should not be interpreted as direct evidence of hydrogen yield or process efficiency.