Investigation on formation mechanisms of ash and deposit from cotton stalk vibrating grate boiler combustion based on their characteristics

The formation mechanisms of ash and deposit from cotton stalk (CS) water-cooled vibrating grate boiler combustion were explored according to their characteristics. Measurements of the ash fusion characteristics indicate the sintering temperatures under an oxidizing atmosphere (O2/CO2, 3:7, volume ratio) decrease in the order fly ash (Fcs) > bottom ash (Bcs) > deposit on the super-heater (Dcs) > CS ash; while four characteristic fusion temperature all increase in the order Bcs < Fcs < Dcs < CS ash. This results from the basic/acid ratio differences in their ash-compositions. Potassium feldspar and anorthite were found in Fcs; the sulfates (from chlorination and vulcanization of K or Ca during combustion) presented in Dcs was closely related to deposit formation; and calcium silicate and gehlenite were found in Bcs. The Fcs was composed of small prismatic particles with molten surface. In the Dcs, only the small spherical particles attached to aggregates were molten, whereas the Bcs contained mostly molten particles. Formation mechanisms of ash and deposit were deduced from the perspective of ash-formed elemental migration and transformation transform during CS combustion. And the layer-structure forming process of Dcs was also deduced.

Automated summary

This study explored the formation mechanisms of ash and deposit from cotton stalk water-cooled vibrating grate boiler combustion based on their characteristics. The measurement results showed that the fusion temperatures of different components of ash were influenced by the basic/acid ratio in their ash composition. Specific mineral components were also identified in the ash and deposit formation.