Reduction of silica in coke with ash of increased basicity

A Thermodynamic Study of Silicon Containing Gas around a Blast Furnace Raceway

“…The effect of total gas pressure on the equilibrium amount of silicon in the gas phase expressed as percent of silicon in the system that is found in the gas phase. As can be seen in reaction (6), silicon from the decrease of SiC partly goes to the gas and partly to formation of (Al 2 O 3 )(CaO) 2 (SiO 2 ). The total effect is that the calculated equilibrium amount of silicon in the gas phase increases.…”

“…Silicon monoxide is usually assumed to form from coke ash and ash from injectants as a result of any of the following reactions [5][6][7][8]10,12,13,[15][16][17]19,20,[22][23][24] : SiO 2 (in ash)ϩCO (g)ϭSiO (g)ϩCO 2 Usually reaction (2) is given as the dominating reaction 5,6,12,13,[15][16][17]20,[22][23][24] Some sources also give reaction (1) as the dominating reaction. 7,8,10) The difference between reactions (1) and (2) is Boudouard's reaction: C (graphite, coke or coal powder)ϩCO 2 (g)ϭ2CO (g)... (5) If reaction (1) occurs, the CO 2 gas formed will react with carbon (from coke or injectants) according to reaction (3) resulting in the net reaction (2).…”

“…This SiC can further react according to reaction (3) or (4), forming SiO gas. 6,17,19) It is important to point out that coal powder is injected through the tuyeres without prior heating, and to a great extent is burnt inside the raceway. When the coal powder has been burnt off, unburned char and ash will remain.…”

“…12 it can be seen that several phase transformations occur between different carbon activities. Between the carbon activities 0.6 and 0.7, (Al 2 O 3 ) 6 9. The effect of carbon activity on the equilibrium amount of silicon in the gas phase expressed as percent of silicon in the system that is found in the gas phase.…”

Comparison of calculated equilibrium and operation data for blast furnace with focus on silicon

“…Usually the formation of SiO and SiS gas in the raceway and the surroundings of the raceway, followed by reduction of the silicon containing gases to dissolved silicon in metal droplets, is seen as the main route to 'siliconisation' of hot metal. 1,2 Several factors have been identified that are believed to influence the silicon content. For example, an increased temperature in the raceway results in more SiO gas formation and a higher silicon content in the hot metal.…”