Mechanochemically Activated Lignin as an Effective Binder for High-Performance Composite Fuel Briquettes

The study investigates the production of composite fuel briquettes by incorporating mechanochemically activated hydrolysis lignin as a binder to improve the properties of mixtures containing coal fines and wood residues. Experimental work included the preparation of raw materials through fine grinding, mechanical activation, and blending in various proportions, followed by hydraulic pressing and drying. Thermogravimetric analysis revealed that adding 15% lignin increased the activation energy of decomposition from 134–145 kJ/mol to 190–200 kJ/mol, with a maximum of 248 kJ/mol under the 98% conversion. Calorimetric tests demonstrated that the higher lignin content enhanced the calorific value from 20.6 MJ/kg to 23.2 MJ/kg. Microstructural examinations using scanning electron microscopy and microtomography confirmed a significant reduction of total porosity from 61% to about 9%, resulting in denser and more uniform briquette structures. Compression strength more than doubled, reaching 950–1020 N, and moisture sorption after 30 days was limited to 2.1%. These results validate the effectiveness of mechanochemical activation of lignin for producing high-strength, energy-dense, and moisture-resistant fuel briquettes from carbonaceous waste materials.