Chemical characteristics of dust from cement kilns

gospodarka surowcami mineralnymi – mineral resources management 2019    Volume 35    Issue 2    Pages 87–102 DOI: 10.24425/gsm.2019.128524 Alicja Uliasz-Bocheńczyk1 Chemical characteristics of dust from cement kilns Introduction The cement industry is a significant emitter of mineral dusts (Duszak et al. 2015), while the main sources of dust emissions in the cement production process are: rotary kilns, raw mills, clinker coolers, and cement mills (Best... 2013). Cement dust and by-pass cement dust are classified as wastes from group 10 – Wastes from thermal processes, subgroups 10 and 13 − wastes from the manufacture of cement, lime and plaster and articles and products made from them. Cement kiln dust (CKD) is categorized as waste in the European Waste Catalogue under 10 13 06 − particulates and dust (except 10 13 12 and 10 13 13) (Nicholls et al. 2007), while Cement By-pass Dust (BPD) under 10 13 13 – solid wastes from gas treatment other than those mentioned in 10 13 12 (Whiteley et al. 2015). Thanks to the activities of the cement industry, the emission was significantly reduced from 5 kg/t of cement to 0.131 kg per one ton of produced cement (http://www.polskicement. pl/emisje-83). The use of modern de-dusting equipment has resulted in a reduction of dust emissions, and thus an increase in the amount of waste to be managed (Duszak et al. 2015).  Corresponding Author: Alicja Uliasz-Bocheńczyk; e-mail: 1 AGH University of Science and Technology, Faculty of Mining and Geoengineering, Kraków, Poland; ORCID iD: 0000-0002-0977-9028; e-mail: © 2019. The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution-ShareAlike International License (CC BY-SA 4.0, http://creativecommons.org/licenses/by-sa/4.0/), which permits use, distribution, and reproduction in any medium, provided that the Article is properly cited. 88 Uliasz-Bocheńczyk 2019 / Gospodarka Surowcami Mineralnymi – Mineral Resources Management 35(2), 87–102 Dust from cement kilns is waste that can primarily be used in the cement manufacturing process (a closed-cycle process) (Bulletin… 2012–2018; Osmanovic et al. 2018) (Table 1). The amounts of CKD and BPD waste used in the cement production process in the years 2011–2014 have been reduced and it was only in 2015 that they increased (Table 1). Table 1. The use of CKD and BPD dust in the cement industry in Poland, Mg (Bulletin… 2012−2018) Tabela 1. Wykorzystanie pyłów CKD i BPD w przemyśle cementowym w Polsce, Mg Year The amount used 2011 24,817.2 2012 12,938.0 2013 11,343.0 2014 9,015.0 2015 13,978.1 However, due to the high content of chlorides (7.5–21.9%) (Jøns et al. 2008; Lanzerstorfer 2016), dusts from cement kilns may not always be used in the cement production process, as this could lead to excessive chloride concentrations in cement (Heikal et al. 2002). Dust from cement kilns can be used as an additive to improve the geotechnical properties of poor soils (Miller and Azad 2000; Sreekrishnavilasam et al. 2000, 2007; Al-Homidy et al. 2017; Rimal et al. 2019), and their suitability for soil stabilization depends on the content of free lime (Sreekrishnavilasam et al. 2007). The analysis carried out by Miller and Azad (Miller and Azad 2000) has shown that the addition of CKD increases the compressive strength significantly after 7–14 days after compaction. The increase of the compressive strength of soils with the addition of dust was also found by Sreekrishnavilasam et al. (Sreekrishnavilasam et al. 2000). Salahudeen et al. (Salahudeen et al. 2014) have found the usefulness of CKD to improve the soil properties during the construction of roads; however, it should be noted that this does not apply to the dusts with high ignition losses, which confirms the obtained results (Sreekrishnavilasam et al. 2007). It was also suggested to use dusts from cement kilns to reduce Zn content in soils (Moon et al. 2010). Another direction is the production of bricks, in which they can replace up to 50% of the raw material (El-Attar et al. 2017; Ahmed et al 2018). Dusts from cement kilns can also be used to remove lead (Salem and Velayi 2012), magnesium, iron, and nickel ions from wastewater (Salem et al. 2015). In addition, due to the Uliasz-Bocheńczyk 2019 / Gospodarka Surowcami Mineralnymi – Mineral Resources Management 35(2), 87–102 89 content of calcium oxide (CaO), they can replace lime in neutralizing acid mine drainage (ARD) (Mackie et al. 2010). Mackie and Walsh (Mackie and Walsh 2015) proposed the use of dust from cement kilns for the purification of acid mine water. The production of concretes and mortars (Maslehuddin et al. 2008; Kunal et al. 2012; Najim et al 2014) has been postulated as a potential cement kiln dust recovery system for many years. Studies have shown that mortars and concrete mixes with 5–10% CKD have similar compression, bending, and tensile strength compared to the control mixture (Maslehuddin et al. 2008; Kunal et al. 2012; Najim et al 2014). Cement kiln dust is a waste of variable composition, which makes it a difficult material to recover; this particularly applies to dust with high chlorine and sulfate concentrations (Siddique 2008). For this reason, there are ongoing efforts aimed at developing new recovery technologies. The paper presents the results of the analysis on the chemical composition, phase composition, and leaching of pollutants (considered as one of the basic properties affecting the choice of waste recovery method) of the three dusts from cement kilns. 1. The materials used for testing Three dusts (Figs. 1−3) from dry cement kilns were used in the tests: cement by-pass dust − BPD 1, cement by-pass dust − BPD 2, cement kiln dust − CKD 1. CKD is a gray to brown fine powder of a relatively uniform grain size – particle size (Kunal et al. 2012), which is confirmed by photographs of the analyzed waste (Fig. 1). 2. Research methodology Chemical composition The analysis of cement dust included the determination of the elemental composition using a MobiLab X5000 X-ray spectrometer. Phase composition XRD measurements were made using a Philips X’Pert Pro MPD diffractometer. DTA (Differential thermal analysis) measurements and TG (Thermogravimetry) were carried out using a Netzsch STA 449F3 Jupiter thermal analyzer. Leaching The content of chlorides in the leachates was determined argentometrically, by means of the Volhard method (back titration). The content of sulfates (VI) was determined by weight. 90 Uliasz-Bocheńczyk 2019 / Gospodarka Surowcami Mineralnymi – Mineral Resources Management 35(2), 87–102 Fig. 1. The analyzed dusts Rys. 1. Analizowane pyły The content of heavy metals: As, Co, Cd, Cr, Cu, Hg, Ni, Pb, Mn, and Ti was determined by inductively coupled plasma mass spectrometry (ICP MS). The content of Ba, Zn, P, K, Na, and Sr was determined by means of Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). 3. Research r (...truncated)