The market for residential pellet burning equipments is well developed in some European countries like Germany, Austria and Italy and rapidly expanding in others. As a consequence the pellet production has also grown, although a large fraction is destined for industrial applications such as coal co-combustion. Due to the existence of chemical elements such as Na, K and Si, the pellet combustion can lead to agglomerated ashes on the grate of the burner causing problems for its proper operation.

The present work aimed to study the influence of temperature and air flows in the ash agglomeration at the grate. For this purpose, it was assembled an experimental setup that, in a brief, description consists of: i) boiler, whose burner allows the regulation of the primary and secondary air flow, ii) variable flow exhaust gases extraction system, iii) controllable feeding system, iv) heat dissipation system, v) data acquisition and control system, vi) exhaust gases analysis system.

The results indicate an increased formation of agglomerated ash with increasing of temperature. In addition, they also suggest the influence of excess air and primary air fraction in that formation, and the existence of an optimum working condition for high excess air and a primary air fraction of around 30%. The application of swirl in the secondary air improves both the flame stability and enables an efficient combustion into regions where the ash agglomeration is reduced. Moreover, they also show that there are other factors that influence the ash agglomeration, mostly related to the changing of the chemical elements ratio due to vaporization of the more volatile species.

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