RELATIONSHIP BETWEEN GEOCHEMICAL CHARACTERISTICS OF THE LATE PLEISTOCENE-HOLOCENE SEDIMENTS AND GROUND WATER QUALITY IN THE SOUTHERN AREA OF HANOI

Joint Research on Environmental Science and Technology for the Eart

INTEGRATED ASSESSMENT OF RISK LEVEL CAUSED BY HAZARDS IN THE COASTAL ZONE OF VIETNAM (CASES STUDY : CAM RANH-PHAN RI COASTAL ZONE)

Joint Research on Environmental Science and Technology for the Eart

INFLUENCES OF SOME HUMAN ACTIVITIES ON THE COASTAL ENVIRONMENT OF THAI BINH PROVINCE, VIETNAM

Joint Research on Environmental Science and Technology for the Eart

The application of equilibrium optimizer for solving modern economic load dispatch problem considering renewable energies and multiple-fuel thermal units

This study presents a modern version of the economic load dispatch (MELD) problem with the contribution of renewable energies and conventional energy, including wind, solar and thermal power plants. In the study, reduction of electricity generation cost is the first priority, while the use of multiple fuels in the thermal power plant is considered in addition to the consideration of all constraints of power plants. Two meta-heuristic algorithms, one conventional and one recently published, including Particle swarm optimization (PSO) and Equilibrium optimizer (EO), are applied to determine the optimal solutions for MELD. A power system with ten thermal power plants using multiple fossil fuels, one wind power plant, and three solar power plants is utilized to evaluate the performance of both PSO and EO. Unlike other previous studies, this paper considers the MELD problem with the change of load demands over one day with 24 periods as a real power system. In addition, the power generated by both wind and solar power plants varies at each period. The results obtained by applying the two algorithms indicate that EO is completely superior to PSO, and the solutions found by EO can satisfy all constraints. Particularly in Case 1 with different load demand values, EO achieves better total electricity production cost (TEGC) than PSO by 0.75%, 0.87%, 0.13%, and 0.45% for the loads of 2400 MW, 2500 MW, 2600 MW and 2700 MW. Moreover, EO also provides a faster response capability over PSO through the four subcases although EO and PSO are run by the same selection of control parameters. In Case 2, the high efficiency provided by EO is still maintained, though the scale of the considered problem has been substantially enlarged. Specifically, EO can save $51.2 compared to PSO for the minimum TEGC. The savings cost is equal to 0.33% for the whole schedule of 24 hours. With these results, EO is acknowledged as a favourable search method for dealing with the MELD problem. Besides, this study also points out the difference in performance between a modern meta-heuristic algorithm (EO) and the classical one (PSO). The modern metaheuristic algorithm with special structure is highly valuable for complicated problem as MELD

Temperature and concentration dependence of ammonium migration in bentonite-clay mixtures: A case study in Hanoi, Vietnam

Groundwater in southern Hanoi, Vietnam has been recently detected to possess high concentration of ammonium ion (NH4+). Otherwise, one of the abundant sources of NH4+ comes from municipal solid waste landfills. Bentonite-clay mixtures (BCMs) widely utilized as landfill bottom barriers in various countries, but limited in Vietnam should perform well to isolate NH4+ from groundwater. This study is to evaluate combined effects of temperature and initial ammonium concentration on adsorption, diffusion, and permeability through mixtures of indigenous clay with 0 %, 5 %, 10 %, 15 % bentonite. The results indicated more effective NH4+ adsorption capacity for low initial concentration than high initial concentration in all temperatures (20, 35, and 50 °C). The temperature dependency showed an increase in adsorption coefficient from 20 °C to 35 °C and a decrease in the range of 35 °C and 50 °C. Whereas diffusion coefficient and hydraulic conductivity for all cases keep increasing gradually in both temperature ranges. The reasonable mass of bentonite content of 15 % should be added into local clay for landfill bottom liners in such conditions of elevated temperature at 50 °C and interaction of ammonium solution 1000 mg/L. The micro-structures via SEM images of these materials provided the proofs of both improvement of hydraulic barrier properties for indigenous clay owing to bentonite presence and NH4+ effects on their micro-structures

Are Social Preferences Stable over Time? Are Social Preferences Stable over Time?

Abstract We use a combination of two natural experiments and one field experiment tomeasur

Studies on Red Mud Material to Use for Combustion of Vietnam Pulverized Coal

The catalytic effect of red mud on Vietnam anthracite’s combustion characteristics was investigated. The mineralogical composition of the red mud includes CaCO3, Fe2O3, FeO(OH), FeTiO3, and Al(OH)3. This red mud is rich in Na, Ca, Al, Fe, and Ti. The combustion characteristics were analyzed by the thermogravimetry method. The combustion effectiveness was assessed by thermogravimetric analysis. The results were derived from a combination of several parameters, such as the ignition temperature, the burnout efficiency, and the amount of heat release. The combustion characteristics of pulverized coal were improved by the introduction of red mud, and the greatest catalytic performance was achieved when the content reached 6%. With the optimal addition, the ignition temperature of anthracite was reduced by 12 °C, and the burnout efficiencies were increased by 2.59% compared to raw anthracite. The amount of heat released by anthracite was increased to 6.93 kJ/g by adding red mud

Separation of thorium and uranium from xenotime leach solutions by solvent extraction using primary and tertiary amines

This study addressed the development of a continuous countercurrent extraction-scrubbing-stripping technique using a mixture of primary and tertiary amines as an effective extractant for both thorium (Th) and uranium (U) to simultaneously separate them from the leach solutions of xenotime concentrate from the Yen Phu mine (Vietnam). Systematic studies determined the optimum parameters of the separation, including the optimum concentrations of the mixture of the primary amine (N1923) and tertiary amine (tri-n-octyl amine), the optimum acidity (pH) of the feed liquor (Yen Phu xenotime leachate), the optimum contact time between phases for extraction, scrubbing and stripping processes, and the most suitable stripping reagent mixture. Using the optimum parameters, the optimum stage number and phase volumetric ratio for extraction, scrubbing, and stripping processes were calculated using the calculus method based on the law of matter conservation. The flow rates of both phases for extraction, scrubbing, and stripping were determined from the results of these studies and calculations. To optimize the separation of uranium and thorium from the Yen Phu xenotime leachate, countercurrent simulations of extraction, scrubbing and stripping were done in a series of mixer-settler units. The results indicated that the selective separation of Th and U with almost no loss of rare earths (REs) and a minimal contamination of iron were obtained. The continuous countercurrent extraction-scrubbing-stripping technique shows potential applications in the commercial separation of Th and U from RE leachate after tests using a sequence of mixer-settler units on a pilot scale

Optimization of sulfuric acid leaching of a Vietnamese rare earth concentrate

The modeling of Yen Phu (Vietnam) xenotime concentrate leaching by sulfuric acid was studied for the purpose of optimizing the process. The response surface methodology (RSM) based on a central composite face-centered (CCF) design was empirically used to model the interactive effect of the independent variables, namely leaching temperatures of 250–450 °C, acid/concentrate (acid/conc.) mass ratios of 0.8–1.8, and leaching times of 2–6 h, on the dependent response, namely the leaching yield. And a CCF model for the leaching of the concentrate was proposed that exhibited good consistency with the experimental data. The shrinking core models for spherical particles of constant size based on the Arrhenius equation were empirically used to study the kinetics of the leaching. The activation energies calculated from the kinetic models for the chemical reaction and diffusion rate stages have the same value of 17.3 kJ·mol−1, which fitted well to a mixed control model of the chemical reaction followed by a diffusion stage at leaching temperatures in the range of 473–593 K. The kinetic studies of the leaching indicated that the leaching percent rate (or leaching yield) is controlled by the leaching temperature. The optimization of the leaching process was estimated by analyzing the contributions of the coefficients of the CCF model to the leaching yield. The results indicated that the effect of leaching temperature on leaching yield is the strongest; it is five times higher than that of the acid/conc. Mass ratio and four times higher than that of the leaching time. The effects of acid/concentration mass ratio and leaching time on leaching yield are insignificant. In addition, the optimum data for leaching are as follows: the leaching temperature, acid/conc. Mass ratio, and leaching time are 320 °C, 1.3, and 4 h, respectively. The proposed CCF model and kinetic study suggested that the optimization of the Yen Phu xenotime concentrate leaching is controlled by the leaching temperature; and the CCF model can potentially be applied in the commercial operation of Yen Phu xenotime concentrate leaching after pilot tests on 50 kg dry concentrate per batch