Abstract
Separation of coal ash into magnetic and non-magnetic fractions facilitates their utilization when processed separately. Due to desulphurization additives added to coal during the fluidised-bed combustion, non-magnetic fractions often contain elevated CaO levels (while magnetic concentrates are typically rich in Fe2O3). Both CaO and Fe2O3 are known for their ability to bind As during the combustion, whose distribution is a crucial parameter in terms of proper utilization of these fractions. Therefore, the study deals with the As partitioning within magnetic and non-magnetic fractions of fluidized-bed coal combustion ashes. Two different (successive) procedures of dry magnetic separation were used to separate each ash into strongly magnetic, less magnetic, and a non-magnetic fraction. Due to their optimal utilization, the concentrations of As and other target elements in these fractions were evaluated and compared. Magnetic concentrates from the first separation step (in vibrofluidized state) contained 60–70% Fe2O3, magnetic concentrates separated manually out of the residues after the first separation contained 26–41% Fe2O3, and the non-magnetic residues contained 2.4–3.5% Fe2O3. Arsenic levels were the highest in the non-magnetic residues and gradually decreased with the increasing Fe2O3 content in the magnetic fractions. The dominant As association in the studied samples was to CaO (r = +0.909) and with SO3 (r = +0.906) whereas its joint occurrence with Fe2O3 was improbable (r = −0.834).
Highlights
Coal has long been a reliable energy source and currently, it is intensively studied as the source of critical elements, such as REE and Y [1,2]; Ge and Ga [3,4,5]; Li [6]; Nb [5,7]; U, Se, and Re [6]; or Ta, Zr, and Hf [7]
During coal combustion, minor and trace elements are redistributed among bottom ash (BA) or slag, fly ash (FA), and emissions
The shares of As in bottom ash, fly ash, and emissions vary considerably depending on the total ash distribution, combustion temperature, amount and type of desulphurization additive, overall composition of the ashes, and flue gas and type of the particulate control device
Summary
Coal has long been a reliable energy source and currently, it is intensively studied as the source of critical elements, such as REE and Y [1,2]; Ge and Ga [3,4,5]; Li [6]; Nb [5,7]; U, Se, and Re [6]; or Ta, Zr, and Hf [7]. Due to the presence of minor and trace elements, it can be responsible for serious pollution problems [8,9,10,11]. During coal combustion, minor and trace elements are redistributed among bottom ash (BA) or slag, fly ash (FA), and emissions. Redistribution among these coal combustion products is determined by the operational conditions [12,13], coal characteristics [14,15], co-combustion of coal with wastes [16,17,18], or addition of desulphurization additives [19,20]. Since As is quite volatile, its share in emissions is not generally negligible
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
