Utilización de las escorias de incineración de RSU para el incremento del poder calorífico del biogás generado por digestión anaerobia de la FORSU

La utilización de las escorias provenientes de la incineración de residuos sólidos urbanos (RSU) para absorber CO2 y H2S del biogás obtenido por digestión anaerobia de la Fracción Orgánica de los RSU (FORSU) tiene un doble beneficio. Por un lado la optimización energética al incrementar el poder calorífico del gas y por otro la estabilización de las escorias para una posterior reutilización. Tanto la FORSU como las escorias forman parte de la gestión integral de los RSU en los denominados ECOPARC. Por tanto, la aplicación de un residuo sobre otro permite cerrar el ciclo completo en cuanto a su generación, estabilización, optimización y reutilización se refiere

APC fly ash recycling: development of a granular material from laboratory to a pilot scale

The aim of this article is to present the research carried out over a 10 year period to develop an environmentally safe method for recycling Air Pollution Control (APC) residues. The initial studies aimed to formulate a mixture of Weathered Bottom Ash (WBA), APC residues and Portland Cement (PC) to be used as a sub-base in road constructions. Mechanical performance was subsequently enhanced by preparing a mortar prior to mixing it with WBA in order to obtain a granular material. After testing different formulations, the optimum mortar consisted of 50% APC residues and 50% PC. The evaluation was carried out based on the concentration release of the heavy metals and metalloids included in the Catalan legislation for revalorization of residues. After the applicability of the granular material was successfully demonstrated at laboratory scale from an environmental and mechanical point of view, a pilot scale plant was designed in order to assess its performance in a real scenario during four month. Thus, three roads were built: two containing 100% granular material and a third containing 100% WBA. The results showed that the immobilisation of all toxic species from APC residues is accomplished by the pozzolanic effect of the cement. The WBA, APC, and PC proportions show to be the most appropriate for compliance with regard to environmental and mechanics requirements

Aggregate material formulated with MSWI bottom ash and APC fly ash for use as secondary building material

The main goal of this paper is to obtain a granular material formulated with Municipal Solid Waste Incinerarion (MSWI) bottom ash (BA) and air pollution control (APC) ash to be used as secondary building material. Previously, an optimum concrete mixture using both MSWI residues as aggregates was formulated. A compromise between the environmental behaviour and the economy of the process was considered. Unconfined compressive strength and abrasion resistance values were measured in order to evaluate the mechanical properties. From these results, the granular mixture was not suited for certain applications owing to the high BA/APC content and low cement percentages used to reduce the costs of the final product. Nevertheless, the leaching test performed showed that the concentrations of all heavy metals were below the limits established by the current Catalan legislation for their reutilization. Therefore, the material studied might be mainly used in embankments, where high mechanical properties are not needed and environmental safety is assured

MSWI bottom ash for thermal energy storage: An innovative and sustainable approach for its reutilization

The management of Municipal Solid Waste (MSW) is a very important issue that must be dealt by the perspective of the 3 Rs (Reuse, reduce, recycle. MSW incineration bottom ash (BA) accounts for 85-95% of the total solids that remained after incineration. Finding suitable alternatives for its revalorization is very attractive, especially in terms of environmental sustainability. Thermal energy storage (TES) is a complementary technology of renewable energy. The aim of this study is to evaluate the thermophysical properties of weathered BA (WBA) in order to find suitable alternatives for its valorisation. Several samples of WBA were collected from a waste-to-energy facility located in Tarragona (Spain). This facility sieved to different size fractions. Each size fraction was characterized with respect its physicochemical properties and the energy density (ren) was calculated. The results obtained showed that this residue is a suitable alternative candidate material for TES as it presents an energy density of 1461.2 kJ m 3 K 1 for the 1-2 mm fraction. In addition, the low cost of this type of residue (0.6V per t) and its high production rate per year makes it an attractive and sustainable alternative for TES

Low-grade magnesium oxide by-products for environmental solutions: characterization and geochemical performance

The reutilization of the by-products from the calcination of natural magnesite for environmental solutions is conditioned by the availability of MgO, CaO and other compounds. In order to overcome their great heterogeneity, an exhaustive chemical and physical characterization is necessary in order to assess their potential applications. In this study, the acid neutralization capacity (ANC) test was used to categorize three types of by-products (LG-MgO, LG-D and LG-F), which mainly differed according to source ore and processing conditions. The experimental data concerning the leaching of Mg2 +, Ca2 +, Fe2 + and SO42 − was corroborated with geochemical predictions using the modelling software Visual MINTEQ. Likewise, the main solubility-controlling mineral phases were also identified. According to the results, there is a buffer capacity within the pH 8 10 range, mainly dominated by the neutralization of MgO/Mg(OH)2, equilibrium with a small contribution from the carbonate content at lower pH values. The release of sulphates showed a non-pH dependency attributed to the solubility of CaSO4 and elemental sulphur present in petcoke. For dust materials, leaching of Fe was minimal above pH 6 owing to the insoluble nature of the Fe2O3/Fe3O4 pair. Accordingly, the by-products labeled as LG-D and LG-F are better suited for stabilizing solid wastes or wastewater that are acid while LG-MgO is more appropriate for alkaline residues such as contaminated soils. In both cases, a suitable pH range in which pH-dependent heavy metals and metalloids show minimum solubility can be obtained. The use of these by-products guarantees an environmentally friendly alkali reservoir for the long-term stabilization of heavy metals and metalloids at a very competitive price as a substitute for the widely used lim

Use of weathered and fresh bottom ash mix layers as a subbase in road constructions: environmental behavior enhancement by means of a retaining barrier

The presence of neoformed cement-like phases during the weathering of non-stabilized freshly quenched bottom ash favours the development of a bound pavement material with improved mechanical properties. Use of weathered and freshly quenched bottom ash mix layers placed one over the other allowed the retention of leached heavy metals and metalloids by means of a reactive percolation barrier. The addition of 50% of weathered bottom ash to the total subbase content diminished the release of toxic species to below environmental regulatory limits. The mechanisms of retention and the different processes and factors responsible of leaching strongly depended on the contaminant under concern as well as on the chemical and physical factors. Thus, the immediate reuse of freshly quenched bottom ash as a subbase material in road constructions is possible, as both the mechanical properties and long-term leachability are enhanced

Material characterization of the MSWI bottom ash as a function of particle size. Effects of glass recycling over time

Differences during the last 15 years in materials' composition in Municipal Solid Waste Incineration (MSWI) regarding bottom ash (BA) were assessed as a function of particle size (>16, 8 - 16, 4 - 8, 2 - 4, 1 - 2 and 0 - 1 mm). After sieving, fractions greater than 2 mm were carefully washed in order to separate fine particles adhering to bigger particles. The characterization took into account five types of materials: glass (primary and secondary), ceramics (natural and synthetic), non-ferrous metals, ferrous metals and unburned organic matter. The evaluation was performed through a visual (> 2 mm) and chemical (0 - 2 mm) classification. Results showed that total weight of glass in the particles over 16 mm has decreased with respect to 1999. Moreover, the content of glass (primary and secondary) in BA was estimated to be 60.8 wt%, with 26.4 wt% corresponding to primary glass in > 2 mm size fractions. Unlike 1999, in which glass was the predominant material, ceramics are currently the major phase in bottom ash (BA) coarse fractions. As for the metals, respect to 1999, results showed a slight increase in all size fractions. The greatest content (> 22 wt%) of ferromagnetic was observed for the 2 - 4 mm size fraction while the non-ferrous type was almost non-existent in particles over 16 mm, remaining below 10 wt% for the rest fractions. In the finest fractions (< 2 mm), about 60 to 95 % of non-ferrous metals corresponded to metallic aluminium. The results from the chemical characterization also indicated that the finest fractions contributed significantly to the total heavy metals content, especially for Pb, Zn, Cu, Mn and Ti

Magnesium phosphate cement formulated with low grade magnesium oxide with controlled porosity and low thermal conductivity as a function of admixture

Magnesium phosphate cement (MPC) formulated with low-grade magnesium oxide (LG-MgO) can be better considered as sustainable MPC (sust-MPC). Among other properties, sust-MPC could be used as building material for constructive elements because of its acoustic and thermal insulation properties. Porosity and thermal conductivity are two important parameters that have a significant influence on thermal insulation properties. In this regard, this work aimed to obtain a highly porous sust-MPC with enhanced properties for thermal insulation. To this end the percentage of porosity as a function of both the amount of set-retarding admixture and the kneading water needed was assessed using a statistical design of experiments (DoE) approach. Additionally, thermal conductivity was also evaluated with respect these two factors. Last but not least, an optimized dosage was sought in order to maximize the percentage of porosity while achieving the lowest thermal conductivity. According to the results obtained, the statistical method successfully predicted the effects of variables on the final properties. Hence, a model that explains the overall behaviour of the system was successfully attained. The obtained model predicts the porosity and the thermal conductivity of sust-MPC by means of the mixture dosage. Consequently, the present work demonstrates that it is possible to control the porosity in order to diminish thermal conductivity. Keywords Insulation; building material; design of experiments; MPC; porosity; thermal conductivit

Thermogravimetric study of a phase change slurry: effect of variable conditions

Microcapsules containing Phase Change Materials (MPCM) are widely used for passive systems in energy storage. When MPCM are mixed with a carrier fluid, Phase Change Slurries (Ks) are used for heat transfer fluids in active systems or heat transport systems. The thermal behavior of PCS can be measured as dry or wet basis, resulting in important differences in weight losses. This study explores the optimum conditions for analyzing the thermal behavior of dried PCS by thermogravimetric analysis (TGA) varying the parameter conditions for obtaining peak temperature and heat flow (latent heat). The factors that were taken into account were the atmosphere of study (air and nitrogen) and the heating rate (0.5, 1, 5, and 10 degrees C.min(-1)). The best conditions to determine peak temperature are at 1 degrees C.min(-1) and in N-2 atmosphere, whereas the decomposition fusion/latent heat of the sample is improved g higher heating velocities towards 10 degrees C.min(-1). (C) 2016 Elsevier Ltd. All rights reserved