Mechanical stability and combustion characteristics of hydrochar/lignite blend pellets

In the present study, hydrochar/lignite pellets were prepared and their fuel qualities including tensile strength, combustion characteristics and ash-related problems were investigated. The results showed that addition of hydrochar to lignite increased tensile strengths of lignite pellets, especially when the hydrochar fraction exceeded 50% in the blends. The main binding forces within hydrochar/lignite pellets were similar to those of hydrochar pellets; the lignite particles were merely interlocked within the matrix of the hydrochar structure. Obvious interactions were observed between hydrochar and lignite during blend pellet combustion and as a result, enhanced thermal efficiency and decreased air pollutant emissions were expected during hydrochar/lignite pellet combustion compared to lignite pellet combustion. The ash from hydrochar/lignite pellets had similar chemical composition to that from lignite pellets, indicating that the utilization and disposal of blend pellet ash would be similar to lignite pellet ash. Furthermore, hydrochar addition to lignite decreased slagging inclination of blended pellets. Based upon calculated slagging index (SI) values, ash from hydrochar/lignite blend pellets was within a low slagging inclination range when the hydrochar fraction in the blend pellets was higher than 50%.