Simultaneous SO₂/NO Removal Performance Of Carbide Slag Pellets In A Fluidized Bed Reactor

Emissions standards for coal-fired power stations around the world are becoming increasingly stringent.It is worth developing an effective method for efficient and simultaneous removal of SO2 and NO with a low-cost and simplified system.This paper proposes a novel simultaneous SO2/NO removal system by co-pelletization of carbide slag and carbonaceous material using extrusion-spheronization method,which seems promising in the industrial application.Carbide slag pellets fabricated by bagasse templating using extrusion-spheronization are proposed to simultaneously remove SO2/NO from flue gas.The effects of the reaction temperature,O2 concentration,mass ratio of bagasse to carbide slag and particle size on the simultaneous SO2/NO removal performance of carbide slag pellets were investigated in a bubbling fluidized bed reactor.CaO in the carbide slag pellets has a significant promotion effect on NO reduction by CO.SO2 and NO are completely removed by the carbide slag pellets at 825-875 ?.With an increase in the mass of bagasse in the pellets,the duration for the complete NO removal becomes longer and the porosity of the pellets appears higher.The higher mass ratio of bagasse to carbide slag leads to a larger surface area and pore volume of the pellets during SO2/NO removal process but results in a slight decrease in the attrition resistance.Coal is more abundant and easier to use than biomass.This paper chooses coal char as the carbonaceous material and co-pelletization with carbide slag to simultaneously remove SO2/NO from flue gas.Experimental results illustrate that compared with biomass char,the content of fixed carbon in coal char is more than that in biomass char resulting in a longer duration in NO removal and a higher NO removal efficiency.The durations of ?NO over 95%for CS-CC pellets are 325 s which is 1.6 times and 1.9 times higher than that for CS-BC pellets CS-PC pellets,respectively.CaO has a catalytic effect on NO reduction by coal char.The carbide slag pellets combined with coal char and carbide slag have a better performance on SO2/NO removal.Moreover,with an increase of the initial NO and SO2 concentration,?NO and?SO2 of carbide slag pellets can also reach to 100%which indicates that the carbide slag pellets has a superior capacity to remove NO and SO2.The phenomenon of attrition and fragment are inevitable when using the carbide slag pellets in fluidized bed.To enhance the mechanical strength of carbide slag pellets.the addition of supporter is proposed.The effects of the addition of supporters on the simultaneous SO2/NO removal performance of carbide slag pellets are investigated in a bubbling fluidized bed reactor.It shows that the addition of high alumina cement has little influence on simultaneous SO2/NO removal,however,the carbide slag pellets doped with porous Al2O3 sphere powder exhibit a poor NO removal property.The addition of supporters can significantly enhance the mechanical strength of carbide slag pellets.The effect of high alumina cement is more remarkable in cold state,while the porous Al2O3 powder works better in hot state.To maintain the relatively high NO/SO2 removal efficiency and high mechanical strength,it is recommended that the amount of porous Al2O3 sphere powder should be controlled at 5%.