Comprehensive analysis of industrial-scale heating plants based on different biomass slow pyrolysis technologies: Product property, energy balance, and ecological impact

Slow pyrolysis poly-generation technology for rural heating using agroforest residues has reached the stage of industrial demonstration application in China. Comprehensive assessment of technical characteristics and technical adaptability is essential as further industrialization development requires related plants to be sustainable and replicable. In this study, three typical technical processes and application models are discussed; namely, poly-generation for syngas and char using a rotary kiln (SCRK), poly-generation for syngas and char using a vertical kiln (SCVK), and poly-generation for hot water and char using a chain grate furnace (HCCF). The technical characteristics, adaptability to raw materials, product property, energy balance, and ecological impact were systematically analyzed by an empirical analysis based on industrial-scale project data. The SCRK was advantageous in terms of product quality and yield of char; the low heating value (LHV) of syngas exceeded 17.3 MJ/m(3), which was approximately thrice that of the other two technical processes. The energy conversion efficiency of the SCVK was 76.8%, that is, approximately 4.0-5.7 percentage points higher than that of the HCCF and SCRK. The emergy sustainability indices of SCRK, SCVK, and HCCF, as ecological indicators, were 31.2, 21.4, and 24.5, respectively. The above results indicate that the heating plants based on biomass slow pyrolysis have promising application prospects. The technology promotion path was discussed by matching production situations, market demands, and technical characteristics based on a technical evaluation radar chart. Some targeted suggestions were proposed for the industrial application of different biomass slow pyrolysis poly-generation technologies. This study provides a reference for industrialization development of biomass slow pyrolysis technologies for rural heating.