Comparison of Microencapsulated Phase Change Materials Prepared at Laboratory Containing the Same Core and Different Shell Material

Microencapsulated Phase Change Materials (MPCM) are widely used in active and passive systems for thermal energy storage. To evaluate the strength of a proper shell/PCM system, comparisons were performed between laboratory-prepared MPCM samples produced by in situ polymerization with a phase change temperature of 50 degrees C and a particle size of around 1-2 mu m with tetracosane as PCM, and polystyrene (PS) and poly (methyl methacrylate) (PMMA) as shells. Evaluation of mechanical performance was performed for different samples by means of Atomic Force Microscopy (AFM) at different temperatures (23 degrees C and 60 degrees C) and with different encapsulation ratios (1:3 and 1:1, shell:core) in order to compare their properties with the PCM below and above its phase change. Evaluations of the Effective Young's modulus (E) and deformation properties were performed for both types of MPCM. For an encapsulation mass ratio of 1:3, PS has better mechanical properties because, when increasing the temperature, the E decreases less than with PMMA. In the comparison between PS/tetracosane systems with different encapsulation mass ratios (1:3 and 1:1), E values were higher for the 1:3 encapsulation mass ratio at both temperatures under study. This means that, in terms of mechanical and thermal properties, the best combination core/shell/encapsulation mass ratio is PS/tetracosane/1:3

Alkali activated binders based on municipal solid waste Incineration bottom ash

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Life Cycle Assessment of Alkali Activated Cement compared to Ordinary Portland Cement

Approximately 8% of the global emissions of CO2 are originated by the cement industry, which consumes on average between 4 to 6 GJ per ton of cement. Ordinary Portland Cement (OPC) is the most used cement for construction purposes. Every year, around 4 billion tonnes (Gt) of OPC are manufactured. For each kg of OPC produced, 0.81 kg of CO2 is generated. Therefore, seeking cements with more environmentally friendly manufacturing process, economically viable, and socially relevant is necessary. One of the most promising materials are the Alkali-Activated Cements (AAC), where its components are an aluminosilicate precursor and alkaline activators. The precursor used in this study is Weathered Bottom Ash (WBA), a waste obtained from the Municipal Solid Waste Incineration (MSWI). On the other hand, the alkaline activators are sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The name of the AAC developed is Sustainable-AAC (Sust-AAC). This project is focused on searching for new materials that could reduce the use of OPC as a building material. To be able to assess the associated environmental impacts, a comparison between AAC and OPC (CEM I) through a Life Cycle Assessment (LCA) following the standards ISO 14040:2006 and ISO 14044:2006 is performed. The LCA methodology allows identification and quantification of relevant inputs and outputs of the system, thus, evaluating the potential environmental impacts associated. The system boundary of this project is cradle-to-gate and the functional unit of the assessment is 1 ton of commercial cement. The OPC inventory is carried out through the values obtained in GaBi Software and the Sust-AAC inventory is made from the previous studies performed in the DIOPMA research group, on a laboratory scale. The results show that the OPC has higher impact on global warming, energy consumption, water consumption, and mineral extraction categories compared to Sust-AAC. In OPC manufacturing, the kiln stage is the most energy intensive stage (by the chemical reaction and by the fossil fuel requirement) and therefore, has the most significant environmental impact in terms of CO2 emissions and energy consumption. In contrast, the highest environmental impacts on the Sust-AAC are due to the production of Na2SiO3. The main reason for the energysaving is because Sust-AAC production does not need a kiln with high temperatures. In addition, the use of waste as raw material promotes a circular economy and, at the same time, reduces the extraction of natural resources. Then, the environmental performance in the Sust-AAC is promising compared to OPC. Sust-AAC is suitable to be used as lightweight material and as insulation material for thermal insulating applications. This application can contribute to realising operational energy savings and performance benefits

Geopolymers based on the valorization of Municipal Solid Waste Incineration residues

he proper management of Municipal Solid Waste (MSW) has become one of the main environmental commitments for developed countries due to the uncontrolled growth of waste caused by the consumption patterns of modern societies. Nowadays, municipal solid waste incineration (MSWI) is one of the most feasible solutions and it is estimated to increase in Europe where the accessibility of landfill is restricted. Bottom ash (BA) is the most significant by-product from MSWI as it accounts for 85-95 % of the solid product resulting from combustion, which is classified as a non-hazardous residue that can be revalorized as a secondary aggregate in road sub-base, bulk lightweight filler in construction. In this way, revalorization of weathered BA (WBA) for the production of geopolymers may be a good alternative to common reuse as secondary aggregate material; however, the chemical process to obtain these materials involves several challenges that could disturb the stability of the material, mainly from the environmental point of view. Accordingly, it is necessary that geopolymers are able to stabilize heavy metals contained in the WBA in order to be classified as non-hazardous materials. In this regard, the SiO2/Al2O3 ratio plays an important role for the encapsulation of heavy metals and other toxic elements. The aim of this research is to formulate geopolymers starting from the 0-2 mm particle size fraction of WBA, as a unique raw material used as aluminumsilicate precursor. Likewise, leaching tests of the geopolymers formulated were performed to assess their environmental impact. The findings show that it is possible to formulate geopolymers using 100 % WBA as precursor, although more investigations are needed to sustain that geopolymer obtained can be considered as non-hazardous materials

Sustainable magnesium phosphate micromortars formulated with PAVAL® alumina by-product as micro-aggregate

Magnesium phosphate cement (MPC) is an attractive alternative to Portland cement (PC) since it can also be obtained using by-products and wastes as raw materials. This research uses low-grade MgO (LG-MgO) as a magnesium source to obtain MPC, reducing CO2 emissions related to MPC production. The obtained binder can be referred to as 'sustainable MPC' (sust-MPC). Moreover, this investigation incorporates a by-product obtained in the aluminium recycling process, named PAVAL® (PV). The addition of PV (5, 17.5, and 35 wt.%) and water to solid (W/S) ratio (0.23, 0.25, 0.28, and 0.31) were studied in terms of mechanical and fresh properties, leaching behaviour, and microstructure to evaluate the degree of PV inclusion in the K-struvite matrix. The addition of PV into sust-MPC improves the mechanical behaviour of the micromortars, indicating a good inclusion of PV. The mechanical and fresh behaviour of the formulations, and BSEM-EDS analysis revealed the potential chemical interaction between Al and K-struvite matrix. The addition of 17.5 wt.% of PV with a W/S of 0.25 showed the best mechanical performance (∼40 MPa of compressive strength at 28 days of curing). The amount of PV should be lower than 17.5 wt.% to classify it as non-hazardous material at the end-of-life

Legal situation and current practice of waste incineration bottom ash utilisation in Europe

Almost 500 municipal solid waste incineration plants in the EU, Norway, and Switzerland generate about 17.6 Mt/a of incinerator bottom ash (IBA). IBA contains minerals and metals. Metals are mostly separated and sold to the scrap market and minerals are either disposed of in landfills or utilised in the construction sector. Since there is no uniform regulation for IBA utilisation at EU level, countries developed own rules with varying requirements for utilisation. As a result from a cooperation network between European experts an up-to-date overview of documents regulating IBA utilisation is presented. Furthermore, this work highlights the different requirements that have to be considered. Overall, 51 different parameters for the total content and 36 different parameters for the emission by leaching are defined. An analysis of the defined parameter reveals that leaching parameters are significantly more to be considered compared to total content parameters. In order to assess the leaching behaviour nine different leaching tests, including batch tests, up-flow percolation tests and one diffusion test (monolithic materials) are in place. A further discussion of leaching parameters showed that certain countries took over limit values initially defined for landfills for inert waste and adopted them for IBA utilisation. The overall utilisation rate of IBA in construction works is approximately 54 wt.%. It is revealed that the rate of utilisation does not necessarily depend on how well regulated IBA utilisation is, but rather seems to be a result of political commitment for IBA recycling and economically interesting circumstances

Parametric investigations to enhance thermal performance of paraffin through a novel geometrical configuration of shell and tube latent thermal storage system

This paper presents a two-dimensional finite element computational model which investigates thermal behaviour of a novel geometrical configuration of shell and tube based latent heat storage (LHS) system. Commercial grade paraffin is used as a phase change material (PCM) with water is employed as a heat transfer fluid (HTF). In this numerical analysis, the parametric investigations are conducted to identify the enhancement in melting rate and thermal storage capacity. The parametric investigations are comprised of number and orientation of tube passes in the shell, longitudinal fins length and thickness, materials for shell, tube and fins, and inlet temperature of HTF. Numerical analysis revealed that the melting rate is significantly enhanced by increasing the number of tube passes from 9 to 21. In 21 passes configuration, conduction heat transfer is the dominant and effective mode of heat transfer. The length of fins has profound impact on melting rate as compared to fins thickness. Also, the reduction in thermal storage capacity due to an increase in fins length is minimal to that of increase in fins thickness. The influence of several materials for shell, tube and fins are examined. Due to higher thermal conductivity, the melting rate for copper and aluminium is significantly higher than steel AISI 4340, cast iron, tin and nickel. Similarly, the thermal storage capacity and melting rate of LHS system is increased by a fraction of 18.06 % and 68.8 % as the inlet temperature of HTF is increased from 323.15 K to 343.15 K, respectively. This study presents an insight into how to augment the thermal behaviour of paraffin based LHS system and ultimately, these findings inform novel design solutions for wide-ranging practical utilisation in both domestic and commercial heat storage applications

Experimental and numerical investigations of nano-additives enhanced paraffin in a shell-and-tube heat exchanger: a comparative study

The impact of metal oxides, metal nitrides and carbon allotropes based nano-additives on thermal conductivity and thermal storage performance of paraffin based latent heat storage (LHS) system is experimentally and numerically investigated. Aluminium oxide (Al2O3), aluminium nitride (AlN) and graphene nano-platelets (GnP) based nano-PCM samples are prepared with ultrasonic emulsification technique. Thermal performance enhancements of nano-PCM samples are investigated by conducting a series of charging and discharging experiments in shell-and-tube heat exchanger at various operating conditions. Moreover, a numerical model is developed to account for an impact of varying operating temperature, nano-additives particle size and volume fraction on the effective thermal conductivity and dynamic viscosity of nano-PCM. The numerical model is simulated to investigate the influence of effective thermal conductivity and dynamic viscosity on heat transfer and temperature distribution, phase transition rate and total enthalpy of the system. It is noticed that the charging rates for Al2O3, AlN and GnP based nano-PCM samples are significantly enhanced by 28.01%, 36.47% and 44.57% as compared to pure paraffin, respectively. Likewise, the discharging rates are augmented by 14.63%, 34.95% and 41.46%, respectively. However, the addition of nano-additives compromises the overall thermal storage capacity and augments the effective dynamic viscosity which has adverse impact on natural convection. Therefore, an optimum volume fraction of nano-additives is determined by conducting experimental examinations on Al2O3 based nano-PCM samples with volume fraction of 1%, 3% and 5%, at varied operating conditions. It is observed that by increasing volume fraction from 1% to 3%, the charging and discharging rates are significantly enhanced. However, an insignificant enhancement is noticed with further increase in volume fraction from 3% to 5%. Therefore, the optimum volume fraction of 3% is established. Furthermore, GnP based nano-PCM samples have demonstrated higher potential for thermal performance enhancement of LHS system and respective utilisation in practical applications

Preparation and exhaustive characterization of paraffin or palmitic acid microcapsules as novel phase change material

WOS: 000350191000030In this study, two different types of Phase Change Materials (PCM) suitable for Thermal Energy Storage (TES) applications were used as a core material in a microencapsulation process. The wall material for these microencapsulated PCM (MPCM) was Poly(styrene-co-ethylacrylate) (PScEA). Microcapsules were prepared using an emulsion co-polymerization technique. The prepared MPCM were characterized as follows: morphology, shape and size were analyzed by Scanning Electron Microscopy (SEM) and Particle Size Distribution (PSD). Besides, Fourier Transformed Infrared spectroscopy (FT-IR) was used to perform the chemical characterization of the shell microcapsules. Moreover, thermophysical properties were analyzed by Differential Scanning Calorimetry (DSC) for the two PCM in usage (paraffin 42-44 and palmitic acid) meanwhile the thermal stability was evaluated by Thermogravimetrical Analysis (TGA). Mechanical characterization of the prepared microcapsules was performed by using the Atomic Force Microscopy (AFM) as indentor. Experiments were performed at two different temperatures 25 degrees C and 70 degrees C, and two parameters were evaluated: the Young's modulus on a punctual area and the vertical force required to plastically deform the MPCM. At the light of the results, it can be considered that these synthesized MPCM were successfully prepared being able to be used in a TES system. (C) 2014 Elsevier Ltd. All rights reserved.Spanish government [ENE2011-28269-C03-02]; European Union's Seventh Framework Programme (FP7) [PIRSES-GA-2013-610692]; Scientific & Technical Research Council of Turkey (TUBITAK) [TUBITAK 111M614]The work is partially funded by the Spanish government (ENE2011-28269-C03-02). The authors would like to thank the Catalan Government for the quality accreditation given to their research group DIOPMA (2014 SGR 1543). The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no PIRSES-GA-2013-610692 (INNOSTORAGE). Also, preparation of microcapsules funded by The Scientific & Technical Research Council of Turkey (TUBITAK) (The Project Code: TUBITAK 111M614)