587545

research-article2015

WMR0010.1177/0734242X15587545Waste Management & ResearchHartmann et al.

Original Article

Possibilities of municipal solid waste incinerator fly ash utilisation

Waste Management & Research 2015, Vol. 33(8) 740­–747 © The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0734242X15587545 wmr.sagepub.com

Silvie Hartmann1, Lukáš Koval’1, Hana Škrobánková2, Dalibor Matýsek3, Franz Winter4 and Amon Purgar4

Abstract Properties of the waste treatment residual fly ash generated from municipal solid waste incinerator fly ash were investigated in this study. Six different mortar blends with the addition of the municipal solid waste incinerator fly ash were evaluated. The Portland cement replacement levels of the municipal solid waste incinerator fly ash used were 25%, 30% and 50%. Both, raw and washed municipal solid waste incinerator fly ash samples were examined. According to the mineralogical composition measurements, a 22.6% increase in the pozzolanic/hydraulic properties was observed for the washed municipal solid waste incinerator fly ash sample. The maximum replacement level of 25% for the washed municipal solid waste incinerator fly ash in mortar blends was established in order to preserve the compressive strength properties. Moreover, the leaching characteristics of the crushed mortar blend was analysed in order to examine the immobilisation of its hazardous contents. Keywords Municipal solid waste incinerator fly ash, pozzolanic/hydraulic properties, mortar, Portland cement, compressive strength, biotoxicity, leaching properties

Introduction Incineration of municipal solid waste has many advantages, including a complete disinfection, considerable reduction in volume (up to 90%) and energy recovery (waste to energy system). This method, however, is not a final solution to the municipal solid waste problem, as it generates bottom and fly ashes that must be disposed of (Liu et al., 2009). The finer fraction especially, collected from the flue gas and referred to as fly ash, poses more serious environmental problems (Shi and Kan, 2009). Fly ash consists of fine particles that contain significant amounts of leachable toxic elements like arsenic, cadmium, chromium, copper, nickel, lead, zinc, chloride salts and sulphates (Ito et al., 2008; Keppert et al., 2012; Nowak et al., 2013; Park and Heo, 2002). In addition, highly toxic organic substances, organic pollutants such as dioxins polychlorinated dibenzo-p-dioxins (PCDD), furans polychlorinated dibenzofurans (PCDF) and polyaromatic hydrocarbons (PAHs) are also present, making the utilisation of fly ash even more problematic (Saikia et al., 2007). For this reason, fly ash residues from incinerators usually do not meet the criteria for recycling as secondary construction materials nor for landfilling, and their pre-treatment is necessary (Aguiar del Toro et al., 2009). Solidification/stabilisation (S/S) processes involve the addition of binding agents (such as cement, etc.) into municipal solid waste incinerator (MSWI) fly ash to effectively fix the heavy metals. Furthermore, MSWI fly ash can be used as a Portland cement replacement (Wenshi et al., 2009). Moreover MSWI fly

ash utilisation offers some environmental advantages, such as the reduction of waste, the protection and saving of natural nonrenewable resources and low or zero-costs for raw materials (Cyr et al., 2012). The primary utilisation of fly ash after treatment is production of construction materials (Mangialardi, 2003; Nishigaki, 2000; Schreurs et al., 2000); i.e. fly ashes can be used as raw materials in the cement manufacturing process (Chen et al., 2009; Wu et al., 2011). This process, however, requires fly ash pre-treatment. The high levels of chlorides are harmful, not only during the recycling process, but also during the application of products obtained from the raw materials. Therefore, the elimination of chlorides from MSWI fly ash is necessary prior to recycling or 1ENET

– Energy Units for Utilization of Non-Traditional Energy Sources, VŠB – Technical University of Ostrava, Ostrava, Czech Republic 2Institute of Environmental Engineering, VŠB – Technical University of Ostrava, Ostrava, Czech Republic 3Institute of Geological Engineering, VŠB – Technical University of Ostrava, Ostrava, Czech Republic 4Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria Corresponding author: Silvie Hartmann, ENET – Energy Units for Utilization of NonTraditional Energy Sources, VŠB – Technical University of Ostrava, 17 Listopadu 15/2172, 708 33 Ostrava-Poruba, Czech Republic. Email: [email protected]

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Hartmann et al. reuses (Chen et al., 2012). Chloride compounds like halite and sylvite (NaCl, KCl) are easily released in leaching tests and can cause a major problem during the clinkers production, as well as a serious corrosion in the cement kiln (Pan et al., 2008). The removal of chlorides can be achieved by several treatment methods, such as washing with water and/or acids (Aguiar del Toro et al., 2009; Chen et al., 2012; Sabbas et al., 2003). Some researchers have shown the pozzolanic/hydraulic activity of the MSWI fly ash (Putero et al., 2013; Rukzon and Chindaprasirt, 2008), which makes it a viable option for the production of cement-based materials. Acceptable replacement levels are strongly dependent on the characteristics of the fly ash, mainly its pozzolanic activity and the possible reaction between alkalis and MSWI fly ash according to ASTM C618-94a. According to Ioannou et al. (2014), the maximum replacement level for the Portland cement by washed fly ash required to preserve the compressive strength properties is 20%. The study focused on possibilities of MSWI fly ash treatment taking into account the hazardous properties and on stabilisation of the MSWI fly ash in cement-based material for applications where the risk for human health is minimised. The aim of this work was to evaluate the possible replacement of the Portland cement by the washed MSWI fly ash, on the basis of the chemical and mineralogical composition, biotoxicity of the MSWI fly ash samples and functional properties of the mortar samples.

Materials and methods Materials and preparation The MSWI fly ash was collected from a MSWI plant located in the Czech Republic (CZ). The composition of the municipal waste burned in the incineration plants was as follows: 30 wt% biogenic waste, 20 wt% paper, 10 wt% plastics, 10 wt% inert waste, 7 wt% compounds, 4 wt% wood, 3 wt% textiles and 3 wt% metals, and 13 wt% others. In addition, the municipal solid waste contained 0.75 wt% of Cl-. A combustion technology grate furnace is used, followed by the heat transfer zone and flue gas cleaning system. The flue gas cleaning system is accomplished as follows: bag house filters, wet scrubbers and selective catalytic reduction. The raw fly ash taken from the flue gas cleaning system was homogenised. The MSWI fly ash used for experiments appeared as a fine light grey-coloured powder with a specific weight of 2.42 g cm-3. Six different mortar blends were prepared by mixing the Portland cement CEM I 52,5R (TOP CEMENT, Cement Hranice) (prepared according to the EN 197-1 Standards European (2011)) with quartz sand with particle sizes between 0.4 and 0.8 mm (prepared in accordance with EN 196-1 Standards European (2005a)). The mortar blends were prepared primarily from the washed and raw MSWI fly ash samples. A control mortar blend (denoted as A control) was prepared with Portland cement, type CEM I 52,5R according to EN 450-1 Standards European (2005b) water/cement ratio of 0.5 and 1350 ±5 g of the quartz sand. To evaluate the effect of MSWI fly ash on the mortar properties, two mortar blends with

washed MSWI fly ash contents of 30, 50 wt% were prepared. These blends are denoted as A 30 and A 50. The influence of salts on the mortar was investigated using a blend with 30 wt% replacement of the Portland cement with the raw MSWI fly ash and denoted as A raw. The compressive strength of the cement mortars was compared using the 20 MPa Concrete screed CZ420 (WEBER Saint Gobain) prepared according to the EN 13813 Standards European (2002). The particle size

Possibilities of municipal solid waste incinerator fly ash utilisation.

Properties of the waste treatment residual fly ash generated from municipal solid waste incinerator fly ash were investigated in this study. Six diffe...
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