Kinetics of Aqueous Leaching and Carbonization of Steelmaking Slag

Abstract

Sequestration of carbon dioxide by steelmaking slag was studied in an atmospheric three-phase system containing industrial slag particles, water, and CO 2 gas. Batch-type reactors were used to measure the rate of aqueous alkaline leaching and slag particle carbonization independently. Four sizes of slag particles were tested for the Ca leaching rate in deionized water at a constant 7.5 pH in an argon atmosphere and for carbonate conversion with CO 2 bubbled through an aqueous suspension. Conversion data (fraction of Ca leached or converted to carbonate) were evaluated to determine the rate-limiting step based on the shrinking core model. For Ca leaching, the chemical reaction is the controlling mechanism during the initial period of time, which then switches to diffusion through the developed porous layer as the rate-limiting step. Carbonate conversion proceeded much slower than leaching conversion and was found to be limited by diffusion through the product calcium carbonate layer. The calculated value of diffusivity was found to be 5 · 10 -9 cm 2 /s, which decreased by an order of magnitude with increasing carbonization conversion as a result of changing density of the product layer. The experimental data fit the shrinking core model well after correction for the particle specific surface area.

CO2 Capture by Accelerated Carbonation of Alkaline Wastes: A Review on Its Principles and Applications

“…Temperature also had a significant effect but only during the first 3 hours of the dissolution reaction according to the results by Lekakh et al (2008). An investigation reported by Tai et al (2006) also suggested that reaction temperature and solution composition should be the most important factors in the carbonation test.…”

“…The rate and extent of calcium leaching in steelmaking slag was found to be inversely related to particle size and pH, and increased with increasing temperature, pressure, and surface area (Iizuka et al, 2004;Tai et al, 2006;Costa et al, 2007;Gerdemann et al, 2007;Lekakh et al, 2008;Teir, 2008;De Windt et al, 2011). Based on a report by Alexander et al (2005), the effects of increased reaction temperature from 25°C to 50°C provided a 70% improvement on dissolution of the primary phase.…”

“…(18) and (19) (Uibu et al, 2009b;De Windt et al, 2011) However, CaO and MgO are rarely present in pure form in steelmaking slag. The alkalinemetal oxides are primary locked into the silicate, aluminate or ferrite phase (Lekakh et al, 2008). …”

“…Eloneva et al (2012) also suggested that a particle size preferably of ~100 μm, or no more than 500 μm, was found to be optimal based on the kinetics studies of calcium leaching. In addition, over 90% and less than 40% of calcium species dissolved in 24 hours were observed from 45-75 and 150-250 μm sized ladle slag, respectively (Lekakh et al, 2008). The power consumption for grinding (crushing) can be calculated with Bond's equation as shown in Eq.…”

Effect of Basic Oxygen Furnace Slag used as Structural Filling Materials on the Subsurface Environment

“…기존 연구에서는 알칼리 용출수가 수계 내 화학적 산소 요구량(Chemical Oxygen Demand, COD), Mayes et al, 2006Mayes et al, , 2008 (Peek and Volk, 1985). 전반적으로 전로제강슬래그의 영향을 받은 토양 내 오염우려물질 함량은 대체적으로 유의한 큰 변화는 없었 (Lekakh et al, 2008). …”