Structural response of a compliant pipe-in-pipe under frictionless and frictional conditions of the seabed.

Pipe-in-Pipe (PIP) technology has been studied significantly owing to its superior performance in deep-water and high-pressure high temperature fields than conventional single pipe. The PIP system has excellent track record of mitigating flow assurance problems from subsea wells through maintenance of the fluid's temperature in the pipe. It has also been applied in marine environment where conventional single pipe cannot perform. However, owing to complex interaction and contact within the PIP system and seabed, the mechanism of load transfer and the stresses that developed due to pressure, temperature and combined loading has not been fully understood and quantified. Therefore, this study examined the effect of pressure, temperature and the combined loading on PIP systems for flat seabed subsea pipeline. Simulations are performed to examined frictional and frictionless conditions of the flat seabed on PIP system and individual results of inner pipe, insulation material and outer pipe are presented for each analysis. The analytical calculations are carried-out for determining the operating stresses in each component of the PIP system in view of its significance for the overall structural behaviour of the system and validation of the numerical model. The impact response of the inner pipe, insulation and the outer pipe based on pressure, temperature and the combination of both (pressure and temperature) and the resulting stress on each component of the PIP system are investigated and the result presented. Furthermore, results of axial, radial and hoop stresses for the individual loading condition and with coupled analysis corresponding to each simulation (Frictional and Frictionless seabed conditions) are found to be closely similar with percentage difference less than 5 except for the von Mises stress which give 5.3%. This interesting finding revealed that the friction force does not affect structural integrity of the PIP system compared to conventional - single pipeline assuming all other parameters remains constant. Moreover, the presence of the outer pipe and the insulation material enhanced the performance of the inner pipe. The numerical simulation predicts closely the impact response for pipe-in-pipe composite specimens under individual and combined loading conditions. Therefore, the results obtained will serve as a reference guide for designing, construction and operating PIP system in the future to develop unconventional challenging energy resources like High Pressure High Temperature fields

Grinding Behavior and Potential Beneficiation Options of Bauxite Ores

This laboratory study investigates selective grinding and beneficiation options for a Greek bauxite ore. First, a series of batch grinding tests were carried out in order to investigate the grinding behavior of the ore and the effect of the material filling volume (fc) on the distribution of aluminium- and iron-containing phases. Then, the ground ore was subjected to magnetic separation either as received or after reduction roasting in order to further explore potential beneficiation options. The results showed that grinding of the ore exhibits non-first order behavior, while the breakage rate varies with grinding time. Additionally, Al2O3 tends to concentrate in the coarser than 0.300 mm product fraction, while fc 10% and 2 min of grinding time are considered optimum conditions for good distribution of Al2O3 and Fe2O3. When different product fractions were subjected to magnetic separation, it was seen that the non-magnetic product obtained from the 0.300–1.18 mm fraction was more rich in Al2O3. In this fraction, the Al2O3 content increased from 58 wt% in the feed to 67.9 wt%, whereas the Fe2O3 content decreased from 22.4 wt% in the feed to 13.5 wt%. When the ore was subjected to a two-step treatment, involving reduction roasting followed by magnetic separation, the Fe2O3 grade decreased from 20.8 to 5.1 wt%, but in this case the recovery was very low

CO₂ Sequestration Using Fly Ash from Lignite Power Plants

Carbon dioxide sequestration by calcium- or magnesium-containing minerals has been recognized as a promising processing route for the permanent and safe storage of carbon dioxide. In this study, the wet carbonation of lignite fly ash containing approximately 39 wt.% of total calcium oxide was attempted in an autoclave at pressure 1–15 bar, temperature 25–150 °C, liquid to solid ratio equal to 10 L/kg and retention time 24 h. Carbon content in treated fly ash was increased due to carbonation from 1.76% to 4.84–6.15% with the maximum value obtained at temperature 100 °C and pressure 15 bar. The analytical techniques applied confirmed the elimination of free lime and the formation of CaCO3. Based on the carbon content in untreated and treated samples it is estimated that under the optimum conditions 212,57 kg CO2 are sequestered in 1 tn of fly ash

Factors Affecting Alkali Activation of Laterite Acid Leaching Residues

In this experimental study, the alkali activation of acid leaching residues using a mixture of sodium hydroxide (NaOH) and alkaline sodium silicate solution (Na2SiO3) as activators is investigated. The residues were also calcined at 800 and 1000 °C for 2 h or mixed with metakaolin (MK) in order to increase their reactivity. The effect of several parameters, namely the H2O/Na2O and SiO2/Na2O ratios present in the activating solution, the pre–curing time (4–24 h), the curing temperature (40–80 °C), the curing time (24 or 48 h), and the ageing period (7–28 days) on the properties of the produced alkali activated materials (AAMs), including compressive strength, porosity, water absorption, and density, was explored. Analytical techniques, namely X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and elemental mapping analysis were used for the identification of the morphology and structure of the final products. The experimental results show that the laterite acid leaching residues cannot be alkali activated in an unaltered state, and the compressive strength of the produced AAMs barely reaches 1.4 MPa, while the mixing of the residues with 10 wt% metakaolin results in noticeably higher compressive strength (41 MPa). Moreover, the calcination of residues at 800 and 1000 °C has practically no beneficial effect on alkali activation. Alkali activated materials produced under the optimum synthesis conditions were subjected to high temperature firing for 2 h and immersed in distilled water or acidic solution (1 mol L−1 HCl) for 7 and 30 days in order to assess their structural integrity under different environmental conditions. This study explores the potential of alkali activation of laterite leaching residues amended with the addition of metakaolin for the production of AAMS that can be used as binders or in several construction applications in order to enable their valorization and also improve the environmental sustainability of the metallurgical sector

Grinding Kinetics of Slag and Effect of Final Particle Size on the Compressive Strength of Alkali Activated Materials

This study aims to model grinding of a Polish ferronickel slag and evaluate the particle size distributions (PSDs) of the products obtained after different grinding times. Then, selected products were alkali activated in order to investigate the effect of particle size on the compressive strength of the produced alkali activated materials (AAMs). Other parameters affecting alkali activation, i.e., temperature, curing, and ageing time were also examined. Among the different mathematical models used to simulate the particle size distribution, Rosin–Rammler (RR) was found to be the most suitable. When piecewise regression analysis was applied to experimental data it was found that the particle size distribution of the slag products exhibits multifractal character. In addition, grinding of slag exhibits non-first-order behavior and the reduction rate of each size is time dependent. The grinding rate and consequently the grinding efficiency increases when the particle size increases, but drops sharply near zero after prolonged grinding periods. Regarding alkali activation, it is deduced that among the parameters studied, particle size (and the respective specific surface area) of the raw slag product and curing temperature have the most noticeable impact on the compressive strength of the produced AAMs

Valorization Potential of Polish Laterite Leaching Residues through Alkali Activation

In this study, the valorization potential of Polish laterite leaching residues through alkali activation with the use of NaOH and Na2SiO3 solutions as activators was investigated. The effect of the main factors, namely the H2O/Na2O molar ratio in the activating solution, the curing temperature, and the ageing period on the main properties of the produced alkali activated materials (AAMs) was assessed. The experimental results showed that AAMs with sufficient compressive strength were only produced when the laterite leaching residues were mixed with significant quantities of metakaolin; thus, when the mass ratio of laterite leaching residues and metakaolin was 0.50, after curing at 40 °C for 24 h and ageing for 7 days, the produced AAMs acquired compressive strength that slightly exceeded 25 MPa. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy (SEM–EDS) analysis were used for the characterization of the raw materials and selected AAMs. Furthermore, the structural integrity of the specimens was investigated after immersion in distilled water and acidic solution (1 mol L−1 HCl), or after firing at higher temperatures. Finally, the toxicity of the produced AAMs was assessed with the use of standard leaching tests

Adsorption of Scandium and Neodymium on Biochar Derived after Low-Temperature Pyrolysis of Sawdust

The objective of this study was to investigate the adsorption of two rare earth elements (REEs), namely scandium (Sc) and neodymium (Nd), on biochar produced after low temperature pyrolysis (350 °C) of wood sawdust. The biochar was characterized with the use of several analytical techniques, namely X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric (TG) analysis, while the pH at point of zero charge (pHPZC) was also determined. The experimental conditions were: absorbent concentration 1–10 g·L−1, REE concentration in solution 20 mg·L−1, contact time for equilibrium 24 h, temperature 25 °C and stirring speed 350 rpm. The efficiency of biochar was compared to that of a commercial activated carbon. Geochemical modelling was carried out to determine speciation of Nd and Sc species in aqueous solutions using PHREEQC-3 equipped with the llnl database. The experimental results indicated the potential of low temperature produced biochar, even though inferior to that of activated carbon, to adsorb efficiently both REEs. The equilibrium adsorption data were very well fitted into the Freundlich isotherm model, while kinetic data suggested that the removal of both REEs follows the pseudo-second order kinetic reaction. Finally, the most probable adsorption mechanisms are discussed

Valorization Potential of Polish Laterite Leaching Residues through Alkali Activation

In this study, the valorization potential of Polish laterite leaching residues through alkali activation with the use of NaOH and Na2SiO3 solutions as activators was investigated. The effect of the main factors, namely the H2O/Na2O molar ratio in the activating solution, the curing temperature, and the ageing period on the main properties of the produced alkali activated materials (AAMs) was assessed. The experimental results showed that AAMs with sufficient compressive strength were only produced when the laterite leaching residues were mixed with significant quantities of metakaolin; thus, when the mass ratio of laterite leaching residues and metakaolin was 0.50, after curing at 40 °C for 24 h and ageing for 7 days, the produced AAMs acquired compressive strength that slightly exceeded 25 MPa. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy (SEM–EDS) analysis were used for the characterization of the raw materials and selected AAMs. Furthermore, the structural integrity of the specimens was investigated after immersion in distilled water and acidic solution (1 mol L−1 HCl), or after firing at higher temperatures. Finally, the toxicity of the produced AAMs was assessed with the use of standard leaching tests

Factors Affecting Alkali Activation of Laterite Acid Leaching Residues

In this experimental study, the alkali activation of acid leaching residues using a mixture of sodium hydroxide (NaOH) and alkaline sodium silicate solution (Na2SiO3) as activators is investigated. The residues were also calcined at 800 and 1000 °C for 2 h or mixed with metakaolin (MK) in order to increase their reactivity. The effect of several parameters, namely the H2O/Na2O and SiO2/Na2O ratios present in the activating solution, the pre–curing time (4–24 h), the curing temperature (40–80 °C), the curing time (24 or 48 h), and the ageing period (7–28 days) on the properties of the produced alkali activated materials (AAMs), including compressive strength, porosity, water absorption, and density, was explored. Analytical techniques, namely X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and elemental mapping analysis were used for the identification of the morphology and structure of the final products. The experimental results show that the laterite acid leaching residues cannot be alkali activated in an unaltered state, and the compressive strength of the produced AAMs barely reaches 1.4 MPa, while the mixing of the residues with 10 wt% metakaolin results in noticeably higher compressive strength (41 MPa). Moreover, the calcination of residues at 800 and 1000 °C has practically no beneficial effect on alkali activation. Alkali activated materials produced under the optimum synthesis conditions were subjected to high temperature firing for 2 h and immersed in distilled water or acidic solution (1 mol L−1 HCl) for 7 and 30 days in order to assess their structural integrity under different environmental conditions. This study explores the potential of alkali activation of laterite leaching residues amended with the addition of metakaolin for the production of AAMS that can be used as binders or in several construction applications in order to enable their valorization and also improve the environmental sustainability of the metallurgical sector

Energy flow analysis in agriculture; the case of irrigated pistachio production in Greece

Summarization: Pistachios (Pistacia vera L.) are among the most energy intensive crops. Therefore, in this study an energy flow analysis was performed to evaluate energy performance of irrigated pistachio production in Greece and identify the most energy consuming phases. Detailed data from on-site surveys were collected from 36 pistachio orchards located in Aegina island during the period 2012–2016. Results showed that the total input energy used for irrigated pistachio production was 41.9 GJ ha−1, whereas the ratios of energy use efficiency and energy productivity were estimated as 70% and 0.06 kg MJ−1, respectively. Nutrient management, irrigation and use of machinery for agricultural operations were the most critical inputs for pistachio production in terms of energy consumption. Additionally, results of econometric analysis indicated that among exogenous inputs analysed in terms of energy performance, fertilizers and machinery had statistically significant positive effects and contributed most to increased yield of pistachios. Based on the overall results of this study, several opportunities for improving energy efficiency and conservation can be identified, including reduction or/and efficient application of chemical fertilizers, water savings, proper use of agricultural machinery, reuse of crop residues for compost production and shifting from fossil fuels to renewable sources of energy.Presented on: Sustainable Energy Technologies and Assessment