Optimization of thermochemical pyrolysis performance of distillers’ grains in a heat-storage rotary bed: A pilot study

Pyrolysis of distillers’ grains was innovatively investigated to establish a multi-objective optimization framework, identifying the optimal pyrolysis time, in a 2.8 t/h pilot-scale regenerative rotary-bed reactor under fixed temperature profiles (700–900 ℃) and an inert nitrogen atmosphere. Three residence-time scenarios (60, 70, 80 min) were systematically evaluated to balance product yields, char quality, gas composition and energy input. The findings indicated that extending residence time decreased solid yield by 3%–6%, increased gas yield by 5%–10%, and reduced char volatile matter from 12.7% to 7.3%, while its calorific value declined from 4435 to 4107 kcal/kg. Remarkably, the combustible gas fraction (H₂, CO, CH₄, C_nH_m) exhibited a non-linear trend (71.7%–77.7%), and the specific energy consumption rose from 3.0 to 3.7 GJ/t. Conclusively, a multi-criteria assessment incorporating product distribution, char properties, gas heating value, and energy demand identified 70 min as the industrially optimal residence time, delivering maximal product value with the lowest energy penalty (3.2 GJ/t). The findings establish critical engineering parameters for large-scale pyrolysis of distillery waste through advanced rotary-bed pyrolysis technology, supporting sustainable waste management and circular bioeconomic development.