Review of Study on Development Low Carbon Industry

Through collecting and arranging research findings in recent years, connotation, necessity, power mechanism, support system and foreign experience and implications of low carbon industry are reviewed and discussed. It is believed that future study should continue to follow up foreign latest research findings. In addition, it should attach importance and strengthen study on economic performance, system and technical management of low carbon industry

The Spatiotemporal Variations and Potential Causes of Water Quality of Headwaters of Dongjiang River, Southeastern China

Due to the steep slope and short concentration time of flow in mountainous areas, the water environment of headwaters is easily disturbed by human activities. The spatial-temporal variation of the water environment is a key issue for the implementation of river restoration. This study aims to explore the spatial-temporal characteristics of water quality and its pollution sources of the headwaters of the Dongjiang River. Water quality monitoring data over the past 6 years were collected and analyzed using principal component analysis, equal standard pollution load, and multivariate statistical analysis. The results show that the water quality presents significant spatial heterogeneity, where the water quality in the middle and lower reaches is poor. The concentrations of ammonia nitrogen and total phosphorus in the middle and lower reaches were 18.3 and 9.5 times higher than those in the upper reaches, respectively. The water quality has tended to improve recently because of ecological compensation and environmental management. Correlation analysis shows that there were significant positive relationships among major pollutants. Critical source areas were identified, which implies that the most polluted area is located in the middle reaches. Studies have also shown that the water pollution mainly comes from livestock and poultry breeding, industrial sewage discharge, and cultivated land. Controlling the scale of construction land and adjusting the industrial structure is one of the main measures for eradicating water environment problems in headwaters in mountainous areas

Voltage-Sensorless Natural Frame Control for Single-Phase CHB Converter under Distorted Grid Conditions

In this paper, a control scheme combining grid voltage sensorless control and natural frame control (NFC) has been proposed for single-phase cascaded H-bridge converter (CHB) under distorted grid conditions. Firstly, the virtual flux (VF) signal is estimated by a modified virtual flux estimator (VFE). Then the VF-based NFC is derived, using the estimated sinusoidal VF signal to generate the unit vectors for synchronization, which enables the omitting of the coordinate transformation, current quadrature signal generation, and phase-locked loop (PLL). Aiming at the problem that grid harmonic interference is not well considered in the conventional NFC and conventional voltage sensorless control, a current controller with enhanced harmonic-rejection ability is proposed in this paper. As a result, better steady-state performance and rapid transient response are achieved. The effectiveness of the proposed method has been verified on a prototype of the single-phase 3-cell CHB converter

The Removal of Pb2+ from Aqueous Solution by Using Navel Orange Peel Biochar Supported Graphene Oxide: Characteristics, Response Surface Methodology, and Mechanism

The value-added utilization of waste resources to synthesize functional materials is important to achieve the environmentally sustainable development. In this paper, the biochar supported graphene oxide (BGO) materials were prepared by using navel orange peel and natural graphite. The optimal adsorption parameters were analyzed by response surface methodology under the conditions of solution pH, adsorbent dosage, and rotating speed. The adsorption isotherm and kinetic model fitting experiments were carried out according to the optimal adsorption parameters, and the mechanism of BGO adsorption of Pb2+ was explained using Scanning Electron Microscope (SEM-EDS), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). Compared with virgin biochar, the adsorption capacity of Pb2+ on biochar supported graphene oxide was significantly increased. The results of response surface methodology optimization design showed that the order of influence on adsorption of Pb2+ was solution pH > adsorbent dosage > rotating speed. The optimal conditions were as follows: solution pH was 4.97, rotating speed was 172.97 rpm, and adsorbent dosage was 0.086 g. In the adsorption–desorption experiment, the desorption efficiency ranged from 54.3 to 63.3%. The process of Pb2+ adsorption by BGO is spontaneous and endothermic, mainly through electrostatic interaction and surface complexation. It is a heterogeneous adsorption process with heterogeneous surface, including surface adsorption, external liquid film diffusion, and intra-particle diffusion

Effect of N-carboxybutyl chitosan on the flotation separation of apatite from dolomite

With high-grade apatite resources exhausted and economic development, enhancing the apatite quality from calcium gangue such as dolomite has a great significance for production. However, it is difficult to separate apatite from dolomite effectively due to the similar surface properties. In this study, the N-carboxybutyl chitosan ($CBC$) was tested as a potential selective depressant to separate apatite from dolomite in the sodium oleate ($NaOL$). Flotation results of single mineral and artificially mixed mineral confirmed the selective depression effect of CBC. The depression mechanism of $CBC$ was investigated using wettability analysis, Fourier Transform Infrared ($FTIR$), and X-ray Photoelectron Spectroscopy ($XPS$) analyses. The results indicated that the $CBC$ adsorption quantity and intensity on the dolomite surface more than that on the apatite surface, which was due to $CBC$ absorbed on apatite surface by hydrogen bonding, while absorbed on dolomite surface mainly through chemical chelating between $Ca$ on the mineral surface and -COO- on the depressant. These adsorption differences led to the flotation separation of the two minerals

Indirect Current Control Method Based on Reference Current Compensation of an LCL-Type Grid-Connected Inverter

NPC (neutral point clamped converter) is widely used in medium- and high-voltage grid connection because of its small power devices, simple overall structure, and easy control. This paper presents an improved indirect current control strategy for an LCL-type NPC. Firstly, the reference current is compensated to suppress the resonant peak of the LCL filter and improve the tracking accuracy of the output current. Then, with the relationship between state variables, the control structure is optimized by introducing the non-PLL control method, so that the sensors are reduced to only two sets. Finally, the traditional differential operator is improved to compensate the calculation delay in digital control. The experimental results show that the amplitude of thee grid-connected current is consistent with the reference value, the phase deviation is reduced from 7° to about 1°, and the transient response time is shortened to 1/3 of that of the traditional method

Indirect Current Control Method Based on Reference Current Compensation of an LCL-Type Grid-Connected Inverter

NPC (neutral point clamped converter) is widely used in medium- and high-voltage grid connection because of its small power devices, simple overall structure, and easy control. This paper presents an improved indirect current control strategy for an LCL-type NPC. Firstly, the reference current is compensated to suppress the resonant peak of the LCL filter and improve the tracking accuracy of the output current. Then, with the relationship between state variables, the control structure is optimized by introducing the non-PLL control method, so that the sensors are reduced to only two sets. Finally, the traditional differential operator is improved to compensate the calculation delay in digital control. The experimental results show that the amplitude of thee grid-connected current is consistent with the reference value, the phase deviation is reduced from 7° to about 1°, and the transient response time is shortened to 1/3 of that of the traditional method

Effects of heavy rare earth element (yttrium) on partial-nitritation process, bacterial activity and structure of responsible microbial communities

Yttrium (Y(III)) is mined commercially for industrial purposes due to its excellent physical properties. However, the effects of Y(III) in mining-wastewater on the performance of partial-nitritation process and ammonia-oxidizing bacteria (AOB) have not been explored. To elucidate Y(III) effects on biological mechanisms, kinetics was conducted to establish a correlation between Y(III) dosage and specific-oxygen-uptake-rate (SOUR). The mechanism(s) demonstrated by bacterial population to resist against toxic effects from Y(III) dose was also investigated using scanning electron microscopy-(SEM), energy-dispersive X-ray spectroscopy-(EDS), confocal laser scanning microscopy-(CLSM)，Fourier transform infrared-(FTIR) spectroscopy, and 2-dimensional correlation infrared-(2DCOS-IR) approach. The study revealed a strong correlation between ammonium oxidation rate (AOR) and Y(III) dosage. AOR promotion was more pronounced when Y(III) concentration was ≤20 mg/L (maximum AOR of 12.39 mgN/L/h, at 5 mg/L), whereas inhibition when Y(III) in influent was >20 mg/L (minimum AOR of 7.34 mgN/L/h, at 500 mg/L). Aiba model demonstrated high-performance (R2 = 0.962) when Y(III) concentration ranged 0–20 mg/L, whereas linear model fitted well (R2 of 0.984) to experimental data when Y(III) dose ranged 20–500 mg/L. The maximum change in SOUR (Vmax), half-rate constant (Km), and inhibition constant (Ki) reached 1.04 d−1, 20.12 mg/L, and 4.87 mg/L, respectively, an indication that dosage of Y(III) could affect the partial-nitritation process. SEM-EDS showed that the content of extracellular polymeric substances (EPS) increased along with increasing Y(III) dosage. When 20 mg/L of Y(III) was dosed, the fraction of Y(III) within the surface elemental composition of the sludge increased gradually whereas that of calcium decreased. To further comprehend the EPS production, CLSM results further revealed β-polysaccharide as the dominant component in the EPS. FTIR/2DCOD-IR showed that the chelation of polyguluronic sections within β-polysaccharide, together with hydrazine might be the main pathways of cell resistance, but β- glucan, may have caused the hormesis.</p

Highly efficient potassium fertilizer production by using a gemini surfactant

Herein, we report that a gemini surfactant can efficiently separate KCl from NaCl by froth flotation to produce potassium fertilizer (KCl). For achieving the obviously superior flotation performance (KCl recovery increased by 14.51%), the dosage of the gemini surfactant should be three times less than that of the conventional monomeric surfactant. Its unique properties, such as double active centers to mineral surfaces, double hydrophobic groups, and stronger surface tension reducing ability, make it a superior flotation collector for separation of KCl from NaCl in potassium fertilizer production