Ash deposition and inorganic element transformation during zhundong coal combustion

In this paper, the Zhundong coal combustion experiments were carried out in a drop tube furnace, and the ash was collected at the buttom of reacter by a non-cooled probe. The fine particles were also collected from the gas by sampling device which composed of dekati low pressure impactor and a water-cooled probe with N₂ dilution. The ashes and fine particles was analyzed by SEM and EDS to obtain the ash deposition and fine particles formation characteristic. Furthermore, the transformation and the effect on slagging of Na, Ca and S were studied. The results indicated that the Na and Ca can be divided into two types. A part of Na and Ca which bounded with Si and Al, would not vaporize during combustion; on the contrary, the others will release into gas and then react with S to form gaseous Na₂SO₄ and CaSO₄. These gaseous sodium and calcium sulfates can be separate into two portion. The first part condensated on the ash particle surface, the remainders form to aerosol which agglomerated with each other and then adhere on ash particles or discharge from stack.