Preparation and proportion optimization of composite binder for coal briquette in industrial silicon smelting

To solve the shortage of lump coal and poor adaptability of binders for briquetting in industrial silicon smelting, a dedicated binder was developed for Jilangde fine coal. The mechanical properties and thermal decomposition behavior of binders were tested, and their action mechanisms were analyzed by FTIR and SEM. The composite formulation was optimized using a simplex centroid mixture design, and the economic feasibility was evaluated. The results show that organic polymer binders construct a bonding network through hydrogen bonding, ionic bonding, molecular chain entanglement, and film-forming effects, among which polyvinyl alcohol exhibits superior mechanical properties. None of the binders altered the main pyrolysis peak temperature of coal, demonstrating compatibility with the requirements of industrial silicon smelting. The ternary composite formulation was optimized using the simplex centroid design method, yielding the optimal ratio of sodium humate: polyacrylamide: polyvinyl alcohol = 5:1:4. At an addition level of 2%, the composite binder achieved a compressive strength of 7.288 MPa and a shatter resistance of 98.634%, with a cost of only 101.9 CNY per ton of fine coal briquetting. This study provides a novel and economical binder solution for fine coal briquetting in industrial silicon smelting.