Consistency in fibre distributions at constant tensile index despite variations in production rate and plate gap in high-consistency refining

Abstract This study explores the effects of adjusting production rate and plate gaps on fibre distributions and handsheet properties in a double disc (DD) refiner, and examines how these factors influence pulp characteristics and energy use. Experimental results indicate that elevating production rates can reduce specific energy demands at a given tensile index (TI). Beyond individual properties, chi-squared tests were used to compare full fibre property distributions. These analyses demonstrated that pulps with equal TI are statistically indistinguishable across operating conditions, whereas pulps with different TI exhibit clear distributional differences. Overall, findings suggest that improved energy efficiency observed at higher production rates is primarily due to more effective refining mechanisms, rather than differences in the resulting fibre distributions. Further research is needed to clarify the complex interplay between production rate, specific energy, fibre properties, and handsheet properties, particularly the role of fibrillation in TI development.