Study of Alkali Emission and Control with Firing a High Alkali Coal

Abstract

In this study, the sodium emission and control with firing a high alkali coal was investigated in a high-temperature muffle furnace. Kaolin was chosen as an additive tested to clarify its sodium capture mechanism and assess its capture performance. The influence of some firing-related factors such as kaolin dosage, temperature and particle sizes of both kaolin and coal on sodium release and sodium capture performance of kaolin was also studied. It was found that more sodium was released when the combustion temperature rose or fine fuel particles were combusted. Kaolin could efficiently capture sodium species to form high-melting sodium alminosilicates, primarily nepheline or carnegieite. Increasing kaolin dosage led to the promoted sodium retention. However, the promotion was not that pronounced in high kaolin dosages. High temperature had a negative effect on sodium capture by kaolin, which could be ascribed to the increasing sodium emission with temperature. Fine kaolin particles exhibited a good sodium Downloaded by [Stockholm University Library] at 21:55 11 August 2015A c c e p t e d M a n u s c r i p t 2 capture performance. Coal particle size had little impact on the interactions between kaolin and sodium species. More than 80 % of the total sodium was retained in ash by kaolin when firing coal (30 µm) with 3 µm kaolin addition in the dosage of 6 wt. % at 1100 °C.

Ash deposition behavior of a high-alkali coal in circulating fluidized bed combustion at different bed temperatures and the effect of kaolin

“…These Na aluminosilicates were generated by the absorption reactions between kaolin and volatilized Na, thus resulting in a remarkably decreased amount of vaporized Na in the flue gas. 21 The compacted slags in the furnace were mainly induced by the condensation of Na 2 SO 4 , while the inner layer on the convection-heating surface was related to fine particles rich in Na 2 SO 4 ; therefore, they were effectively suppressed by kaolin. Additionally, mullite (Al 6 Si 2 O 13 ) appeared in the fly ash after the addition of kaolin, possibly generated from the phase transformation reaction during the heating of kaolin.…”

Online-CPD-Coupled Large-Eddy Simulation of Pulverized-Coal Pyrolysis in a Hot Turbulent Nitrogen Jet

“…As a major energy source, coal has been widely utilized in power plants using the pulverized-coal combustion (PCC) technology (Cheng et al, 2015;Hashimoto et al, 2012;Liu and He, 2015;Ströhle et al, 2014;Xu et al, 2015;Zhao and Haworth, 2014). On the other hand, coal is the most polluting fossil fuel.…”