Pyro processing cement kiln bypass dust: Enhancing clinker phase formation

Abstract

The valorisation of cement kiln bypass dust (CBPD) is explored for sustainable production of cementitious clinker phases. CBPD can replace the calcareous component in cement manufacture and allow for a reduction in CO 2 emissions as the calcium component in CBPD is mostly decarbonised. CBPD was heated with/out the addition of alumina or silica at temperatures of 900 -1100°C to produce clinker phases. Belite and mayenite formed at temperatures as low as 900°C, while alite formation was achieved at 1200°C, which is significantly lower than is conventional (~1450°C). Alite is thermodynamically stable only above 1250°C; thus, the reduced temperature is potentially owing to the presence of chloride found in the CBPD (as KCl) which was also eventually simultaneously removed through pyro processing at 1100 -1200°C. The investigation also confirmed that the formation of belite is enhanced in the presence of molten KCl.

Producing cement clinker assemblages in the system: CaO-SiO2-Al2O3-SO3-CaCl2-MgO

“…As an example, the XRD pattern of AY7 is provided in Figure 8, where the characteristic peak of alite is observable at 14.9° 2θ. Alite is thermodynamically stable at 1250°C [52] but only practically forms at temperatures >1400°C [53], mineralisation by the presence of CaF2 has been reported to reduce its formation temperature [54,55], and similar mechanism may have occurred with chloride ions, as reported by Odler and Abdul-Maula [56] and Hanein et al [16]; a lowtemperature (around 1200°C) formation of C3S was also observed by Chen et al [57] using CaCl2 and CaSO4 as mineralizers for a more sustainable PC production. could not be co-produced, also suggesting their incompatibility under the assessed processing conditions.…”

“…As shown in Table 1, significant amounts of chloride and MgO are included in alinite cements; thus, this clinker phase is a good candidate in the CaO-SiO2-Al2O3-SO3-CaCl2-MgO system. The presence of chloride salt may also enhance the clinkering reactions by acting as a molten flux [13][14][15][16].…”

Manufacture of potassium chloride from cement kiln bypass dust: An industrial implementation case for transforming waste into valuable resources

“…For decades, considerable efforts have been devoted to the environmentally-safe disposal and effective resource utilization of bypass dust [ [12] , [13] , [14] , [15] , [16] , [17] ]. Currently, the bypass dust is typically used as a blending material for cement or mortar in the production of hollow blocks, cement masonry, plastering mortar, and pavement bricks [ 14 , 15 ].…”

Recycling of Cement Industry Waste for Alkali-Activated Materials Production

“…In the cold end of a clinker kiln, dust is released (called aspiration dust), and its composition is similar to that of the initial raw mixture [ 36 ]. Clinker dust is generated in the last hot zone of the kiln, in the cooling sections, and in the clinker conveyor gallery [ 37 ]. It has been established that the production of each kilogram of clinker accounts for up to 7.5 m 3 of exhaust gases, with a dust content of up to 70 g/m 3 [ 38 ].…”