Catalytic oxidative hydrothermal treatment of palm oil mill effluent over CuO/Al2O3 and Ce-CuO/Al2O3 catalysts

This study aspires to investigate the performance of novel non-oxidative and oxidative subcritical hydrothermal treatments (NOHT and OHT, respectively), followed by catalytic oxidative hydrothermal treatment (COHT) of palm oil mill effluent (POME). Hydrothermal reaction is commonly used in wet biomass treatment, but it had never been used in POME treatment before this research was conducted. The high reaction temperature and time of hydrothermal process and catalyst activity in an aqueous environment are problems to be addressed. Hence, the objectives of this research are to investigate the performance of hydrothermal reactions and catalytic reactions as well as to propose the reaction mechanisms. The experiments of OHT and NOHT were conducted using 500 mL POME of initial COD and BOD5 at 52200 mg/L and 18020 mg/L, respectively, at different temperatures (493-533 K) and reaction times (2-8 h). Meanwhile, the experiments of COHT were performed using a similar working volume of POME over two types of catalysts, i.e., CuO/Al2O3 and Ce-CuO/Al2O3, at loadings of 0.2, 1.0, and 2.0 mg/ml at 533 K for 8 h. The dominant component of fresh POME, i.e., n-hexadecanoic acid, gradually reduced in the liquid products of NOHT and OHT in reactions with elevated temperatures. Carboxyl compounds reduced while phenolic components increased as reaction temperature increased over NOHT. The gaseous products of NOHT contained carbon dioxide (CO2), carbon monoxide (CO), hydrogen gas (H2), and C3-C6 hydrocarbons. Traces of methane gas (CH4) were only found at 533 K due to subcritical hydrothermal gasification at low temperatures. The decolourisations of POME in NOHT and OHT were 7.02% and 54.10% respectively at 533 K and 8 h, indicating the notable performance of OHT in decolourising POME. At 533 K and 8 h, NOHT achieved the highest reductions of chemical oxygen demand (COD) and five-day biochemical oxygen demand (BOD5) at 61.4% and 68.0%. However, the OHT reaction resulted in better removals of COD and BOD5, recording 81% and 87% respectively, with the pH of the liquid product approaching 6.5 from the initial value of 3.5 at the same reaction temperature and time. Notwithstanding, COHT of POME achieved more remarkable performance than the non-catalytic reactions. At a loading of 2.0 mg/ml catalyst in COHT, Ce-CuO/Al2O3 recorded 86.1% COD and 94.7% BOD5 removals at 533 K and 8 h, where its performance was slightly better than CuO/Al2O3 (79.4% COD and 93.8% BOD5 removals). The increase of catalysts loading after 1.0 mg/ml did not contribute any significant difference in degrading the pollutants of POME, suggesting the adequacy of using 1.0 mg/ml catalysts viewing from the technical and economic aspects. The reusability test of spent Ce-CuO/Al2O3 catalysts showed insignificant leaching of Cu and Al elements, and the reductions of COD and BOD5 were as high as 75.4% and 85.2% respectively, indicating no significant deactivation of catalysts up to three reaction cycles. In the derivation of kinetic rate law, a second-order kinetic conformed well to experimental data of COHT with correlation coefficients greater than 0.90 and an error of less than 5% between the estimated and experimental findings. For the mechanism studies, POME in NOHT decomposed into water-soluble compounds, followed by deoxygenation (dehydration and decarboxylation) in producing hydrochar with lower oxygen content and higher aromatic compounds in the liquid product. On the other hand, the reaction mechanism was dominated by the free radicals’ reaction in COHT. The experimental findings have successfully revealed the potential of this novel POME treatment method in substituting the conventional treatment process. This novel study could act as a foundation for the scalability and commercialisation of hydrothermal processes in POME treatment in the future

Hydrothermal Treatment of Palm Oil Mill Effluent (POME) under Oxidative and Non-oxidative Conditions

The performances of oxidative (OHT) and non-oxidative (NOHT) subcritical hydrothermal treatments of palm oil mill effluent (POME) were investigated. The experiments were performed in a pressurised 500 mL-autoclave at different temperature (493 K – 533 K) and reaction time (2 h – 8 h). At 533 K and 8 h, the OHT reaction showed the highest removals of 5-day biochemical oxygen demand (BOD5) and chemical oxygen demand (COD), recording 87.30% and 71.23% respectively, with the pH of liquid product attained 6.5 from an initial value of 3.5. The reduction of COD and BOD5 in NOHT was lower than that in OHT, which were 61.43% and 68.02%, respectively. The mechanism of OHT reaction was via the free radical's pathway. In contrast, the organic compounds originally present in POME degraded into water-soluble products, accompanied by deoxygenation that consisted of decarboxylation and dehydration during the NOHT

Experimental evaluation and empirical modelling of palm oil mill effluent steam reforming

The current work describes a novel application of steam reforming process to treat palm oilmill effluent (POME), whilst co-generating H2-rich syngas from the treatment itself. The effects of reaction temperature, partial pressure of POME and gas-hourly-space-velocity (GHSV) were determined. High crystallinity 20 wt%Ni/80 wt%Al2O3 catalyst with smooth surface was prepared via impregnation method. Baseline runs revealed that the prepared catalyst was highly effective in destructing organic compounds, with a two-fold enhancement observed in the presence of 20 wt% Ni/80 wt%Al2O3 catalyst, despite its low specific surface area (2.09 m2 g−1). In addition, both the temperature and partial pressure of POME abet the COD reduction. Consequently, the highest COD reduction of 99.7% was achieved, with a final COD level of 73 ± 5 ppm from 27,500 ppm, at GHSV of 40,000 mL/h.gcat and partial pressure of POME equivalent to 95 kPa at 1173 K. In terms of gaseous products, H2 was found to be the major component, with selectivity ranged 51.0%–70.9%, followed by CO2(17.7%–34.1%), CO (7.7%–18.4%) and some CH4 (0.6%–3.3%). Furthermore, quadratic models with high R2-values were developed

A new approach to the study of the ground-state properties of 2D Ising spin glass

A new approach known as flat histogram method is used to study the +/-J Ising spin glass in two dimensions. Temperature dependence of the energy, the entropy, and other physical quantities can be easily calculated and we give the results for the zero-temperature limit. For the ground-state energy and entropy of an infinite system size, we estimate e0 = -1.4007 +/- 0.0085 and s0 = 0.0709 +/- 0.006, respectively. Both of them agree well with previous calculations. The time to find the ground-states as well as the tunneling times of the algorithm are also reported and compared with other methods.Comment: 11 pages, 4 figure

Adaptive OCR coordination in distribution system with distributed energy resources contribution

More and more distributed energy resources (DERs) are being added to the medium-voltage (MV) or low-voltage (LV) radial distribution networks (RDNs). These distributed power sources will cause the redistribution of power flow and fault current, bringing new challenges to the coordination of power system protection. An adaptive protection coordination strategy is proposed in this paper. It will trace the connectivity of the system structure to determine the set of relay numbers as a tracking path. According to the topology of the system structure, the tracking path can be divided into two categories: the main feeder path and the branch path. The time multiplier setting (TMS) of each relay can be used to evaluate the operation time of the over-current relay (OCR), and the operation time of the relay can be used to evaluate the fitness of the TMS setting combination. Furthermore, the relay protection coordination problem can be modeled to minimize the accumulated summation of all primary and backup relay operation time (OT) subject to the coordination time interval (CTI) limitation. A modified particle swarm optimization (MPSO) algorithm with adaptive self-cognition and society operation scheme (ASSOS) was proposed and utilized to determine TMS for each relay on the tracking path. A 16-bus test MV system with distributed generators (DGs) will be applied to test the adaptive protection coordination approach proposed in this paper. The results show that the proposed MPSO algorithm reduces the overall OT and relieves the impact on protection coordination settings after DG joins the system. The paper also tests and compares the proposed MPSO with other metaheuristic intelligence-based random search algorithms to prove that MPSO possesses with increased efficiency and performance

LSST Science Book, Version 2.0

A survey that can cover the sky in optical bands over wide fields to faint magnitudes with a fast cadence will enable many of the exciting science opportunities of the next decade. The Large Synoptic Survey Telescope (LSST) will have an effective aperture of 6.7 meters and an imaging camera with field of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over 20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a total point-source depth of r~27.5. The LSST Science Book describes the basic parameters of the LSST hardware, software, and observing plans. The book discusses educational and outreach opportunities, then goes on to describe a broad range of science that LSST will revolutionize: mapping the inner and outer Solar System, stellar populations in the Milky Way and nearby galaxies, the structure of the Milky Way disk and halo and other objects in the Local Volume, transient and variable objects both at low and high redshift, and the properties of normal and active galaxies at low and high redshift. It then turns to far-field cosmological topics, exploring properties of supernovae to z~1, strong and weak lensing, the large-scale distribution of galaxies and baryon oscillations, and how these different probes may be combined to constrain cosmological models and the physics of dark energy.Comment: 596 pages. Also available at full resolution at http://www.lsst.org/lsst/sciboo

Effects of Tillage and Nitrogen Fertilizers on CH4 and CO2 Emissions and Soil Organic Carbon in Paddy Fields of Central China

Quantifying carbon (C) sequestration in paddy soils is necessary to help better understand the effect of agricultural practices on the C cycle. The objective of the present study was to assess the effects of tillage practices [conventional tillage (CT) and no-tillage (NT)] and the application of nitrogen (N) fertilizer (0 and 210 kg N ha−1) on fluxes of CH4 and CO2, and soil organic C (SOC) sequestration during the 2009 and 2010 rice growing seasons in central China. Application of N fertilizer significantly increased CH4 emissions by 13%–66% and SOC by 21%–94% irrespective of soil sampling depths, but had no effect on CO2 emissions in either year. Tillage significantly affected CH4 and CO2 emissions, where NT significantly decreased CH4 emissions by 10%–36% but increased CO2 emissions by 22%–40% in both years. The effects of tillage on the SOC varied with the depth of soil sampling. NT significantly increased the SOC by 7%–48% in the 0–5 cm layer compared with CT. However, there was no significant difference in the SOC between NT and CT across the entire 0–20 cm layer. Hence, our results suggest that the potential of SOC sequestration in NT paddy fields may be overestimated in central China if only surface soil samples are considered

Global Vascular Guidelines on the Management of Chronic Limb-Threatening Ischemia

Chronic limb-threatening ischemia (CLTI)is associated with mortality, amputation, and impaired quality of life. These Global Vascular Guidelines (GVG)are focused on definition, evaluation, and management of CLTI with the goals of improving evidence-based care and highlighting critical research needs. The term CLTI is preferred over critical limb ischemia, as the latter implies threshold values of impaired perfusion rather than a continuum. CLTI is a clinical syndrome defined by the presence of peripheral artery disease (PAD)in combination with rest pain, gangrene, or a lower limb ulceration >2 weeks duration. Venous, traumatic, embolic, and nonatherosclerotic etiologies are excluded. All patients with suspected CLTI should be referred urgently to a vascular specialist. Accurately staging the severity of limb threat is fundamental, and the Society for Vascular Surgery Threatened Limb Classification system, based on grading of Wounds, Ischemia, and foot Infection (WIfI)is endorsed. Objective hemodynamic testing, including toe pressures as the preferred measure, is required to assess CLTI. Evidence-based revascularization (EBR)hinges on three independent axes: Patient risk, Limb severity, and ANatomic complexity (PLAN). Average-risk and high-risk patients are defined by estimated procedural and 2-year all-cause mortality. The GVG proposes a new Global Anatomic Staging System (GLASS), which involves defining a preferred target artery path (TAP)and then estimating limb-based patency (LBP), resulting in three stages of complexity for intervention. The optimal revascularization strategy is also influenced by the availability of autogenous vein for open bypass surgery. Recommendations for EBR are based on best available data, pending level 1 evidence from ongoing trials. Vein bypass may be preferred for average-risk patients with advanced limb threat and high complexity disease, while those with less complex anatomy, intermediate severity limb threat, or high patient risk may be favored for endovascular intervention. All patients with CLTI should be afforded best medical therapy including the use of antithrombotic, lipid-lowering, antihypertensive, and glycemic control agents, as well as counseling on smoking cessation, diet, exercise, and preventive foot care. Following EBR, long-term limb surveillance is advised. The effectiveness of nonrevascularization therapies (eg, spinal stimulation, pneumatic compression, prostanoids, and hyperbaric oxygen)has not been established. Regenerative medicine approaches (eg, cell, gene therapies)for CLTI should be restricted to rigorously conducted randomizsed clinical trials. The GVG promotes standardization of study designs and end points for clinical trials in CLTI. The importance of multidisciplinary teams and centers of excellence for amputation prevention is stressed as a key health system initiative. © 2019 Society for Vascular Surgery and European Society for Vascular Surger