Dust and flue gas chemistry during rapid changes in the operation of black liquor recovery boilers: Part 2 - Dust composition

This is the second of three papers concerning dust and flue gas chemistry of two kraft recovery boilers during rapid changes in boiler dynamics. This paper presents the results of the changes in fume composition, especially the behavior of potassium and chloride during the tests. The purpose of these studies was to shed new light on the formation and composition of fume during rapid changes in boiler operation. In these dynamic tests the dust composition (sodium, potassium, and chloride) behaved mainly in the similar way in both boilers. About 6%-9% of the input sodium was released in fume in these tests. Some 11%-15% of input potassium and 25%-35% of input chloride were found in fume. The release of sodium from the char bed surface during the total interruption of black liquor flow was about 300 mg Na/s per m(2) of floor area in both boilers. The composition of size fractionated dust samples (Na, K, Cl, SO4, CO3) analyzed either with IC and ICP-MS or SEM/EDXA showed equal trends as the operating conditions of the boilers were changed. Application: This work adds insights on the topic of dust composition in kraft recovery boilers.