Kinetic analysis and volatile-char interactions during fast pyrolysis of high-ash Indian coals for enhanced energy recovery

• Fast pyrolysis of five high-ash coals via CDS Pyroprobe–GC–TCD analysis. • Higher temperature/time boosted volatile–char interactions and gas yields. • Low H 2 from suppressed aromatic condensation and selective bond breakage. • Light hydrocarbons from oxygenated char surface reactions predominated. • Similar kinetics in all coals with narrow activation energy ranges. This study investigates the fast pyrolysis behavior and devolatilization kinetics of five high-ash Indian coals using a CDS Pyroprobe 5200 coupled with GC-TCD for real-time gas analysis. Experiments were performed at 600–900 °C and residence times of 2 and 10 s to simulate conditions relevant to entrained flow gasifiers and pulverized coal combustion. Increasing pyrolysis temperature and residence time intensified volatile-char interactions, accelerating char decomposition and elevating overall gas yields (±5 % experimental uncertainty). Hydrogen signals were weak and could not be reliably quantified due to TCD detection limitations with helium carrier gas, though observations suggest suppressed formation potentially related to limited aromatic ring condensation, while gas evolution is largely controlled by cleavage of aliphatic carbon structures (sp 3 and sp 2 -sp 3 hybridized). CO and CO 2 were produced through reactions of oxygenated char, whereas light hydrocarbons (CH 4 , C 2 H 4 , C 2 H 6 ) originated from aliphatic chain breakdown. Kinetic evaluation revealed consistent apparent activation energies across all coal types (150–180 kJ/mol, ±8% variation), indicating uniform pyrolytic behavior despite compositional variations. Mass balance calculations show >95 % material recovery, validating the experimental approach. These findings provide new mechanistic into fast pyrolysis of high-ash coals and deliver essential kinetic parameters for optimizing of thermochemical conversion processes. They also highlight the potential for efficient energy recovery from low-grade coal resources under rapid thermal decomposition conditions.