Hongxiang Xu

Study on Size and Density Distribution in Fine Coal Flotation

Mineral composition, size fraction, and density distributions of a fine coal sample were used to determine its floatability and quality characteristics. Flotation rate tests were conducted using different agitation speeds of flotation machines. The results showed that the ash of clean coal product increased gradually with increasing agitation speed and the floatability of coal became poor. The higher the agitation speed, the faster the flotation rate was. For coarse size coal with higher density, the recovery was low. For the same size particle and density, the higher the agitation speed, the higher the recovery. The relationship between energy (E) and recovery (ϵ) were estimated through the cubic expression. The model parameters were calculated using software MATLAB7.0. The experimental data of various size fractions showed that the fitting of the model was very good.

Separation of Oil from Wastewater by Coal Adsorption-Column Flotation

In order to improve the separation efficiency of fine oil droplets from oily wastewater, a new process utilizing coal adsorption and column flotation has been developed. In this work, anthracite from Jincheng, China was used as an adsorbent for oil removal from wastewater. The effects of adsorption time, coal particle size distribution, the value of pH, and the oil concentration in wastewater on the adsorption capacity of anthracite were investigated by static experiments. A novel device named a cyclone-static microbubble flotation column was developed for the separation of oily wastewater, which combines the conventional hydrocyclone with a conventional flotation column. Coal adsorption-column flotation tests were carried out and scaled-up from a lab-scale (1 m3/day), to a pilot scale (30 m3/day), and to a full-scale (2000 m3/day) unit. Different operating parameters, such as coal dosage, feed rate, circulation pressure, and gas flow rate were studied. In full-scale tests of 2000 m3/day, oil removal of 97.70% with the treated effluent containing an oil concentration of 23.39 mg/L was obtained.

Study of Oil Removal Kinetics using Cyclone-Static Microbubble Flotation Column

The cyclonic-static microbubble flotation column (FCSMC) has dual effects including the cyclonic separation and airflotation separation with advantages in the oily wastewater treatment field such as the small lower limit of the effective separation size, short separation time, large handling capacity, and low operating cost, especially the polymer-flooding oily wastewater treatment aspect. In this paper, the cyclonic separation function mechanism of the FCSMC was investigated. In addition, several operating parameters which impact oil removal efficiency and kinetics constants such as circulating pressure, the superficial gas velocity and the frother consumption were also investigated. The mathematical model relationship between the separation kinetics constants and the factors including circulating pressure, gas superficial velocity, and the average bubble diameter was established. Based on the strength by steps, the physical separation model of the cyclonic-static microbubble was also established.

A comparison of desorption process of Chinese and Australian lignites by dynamic vapour sorption

ABSTRACT Modified BET model and Do and Do (D.D.) model were chosen to interpret the desorption process of water on hard and soft lignites. The organic and inorganic hydrophilic sites were determined by X-ray photoelectron spectroscopy and X-Ray fluorescence spectroscopy. From the modified BET model, only a small part of hydrophilic sites (HSs) acted as effective primary sites due to space restraint, intramolecular hydrogen bond and maybe more than one hydrophilic site connecting with one water molecule. From the D.D. model, the total adsorption sites (St) of Loy Yang lignite (LY) is 18.7 mmol/g, which is higher than that of Shengli (SL) 17.0 mmol/g in spite of lower primary sites, and the saturation concentration of water (qus) in the micropore of LY is 33.7 mmol/g, which is much higher than that of SL (12.5 mmol/g). So the high moisture-holding capacity of LY is mainly determined by the high St and qus, and not the primary sites. The size of water clusters entering the micropores is 7 for SL and 6 for LY, which is related to relative location of HS. When dewatered, the higher total sites density and smaller water cluster size of LY both implied higher dewatering energy.

Gas holdup in cyclone-static micro-bubble flotation column

ABSTRACT The present work has been carried out to investigate the effect of process variables on gas holdup and develop an empirical equation and a neural network model for online process control of the gas holdup based on the operating variables. In this study, the effect of process variables (nozzle diameter, circulation pressure, aeration rate, and frother dosage) on gas holdup in a cyclone-static micro-bubble flotation column of an air/oily wastewater system was investigated. Gas holdup was estimated using a pressure difference method and an empirical equation was proposed to predict gas holdup. A general regression neural network (GRNN) model was also introduced to predict gas holdup for the cyclone-static micro-bubble flotation column. The predictions from the empirical equation and the GRNN are in good agreement with the experiment data for gas holdup, while the GRNN provides higher accuracy and stability compared with that of the empirical equation.

Oil removing efficiency in oil–water separation flotation column

AbstractAn oil–water separation flotation column with a unique structure was used in oil–water separation fields. The oil–water separation flotation column contains the cyclonic separation and airflotation separation with advantages in the oily sewage treatment field such as low effective separation size, short separation time, large handling capacity, and low operating cost, especially in polymer-flooding-drive oily sewage treatment aspect. In this paper, the oil removal efficiencies of the cyclonic and airflotation sections of the oil–water separation flotation column were investigated. In addition, several operating parameters which impact separation such as feeding speed, aeration rate, circulating pressure, underflow split ratio, frother consumption were also investigated. The optimum operating parameters determined for the oil–water separation flotation column were a feeding speed of 1.50 m3 h−1, an aeration rate of 2.50 m3 h−1, and a circulating pressure of 0.28 MPa. A bottom flow diversion ratio o...

Improving Coal Flotation by Classified Conditioning

ABSTRACT How to improve coal flotation performance has been examined with a focus on the effect of particle size on flotation conditioning. A coking coal sample collected from the flotation feed of a coal preparation plant located in Lu’an, Shanxi province of China was investigated. The characters including mineral composition, size fraction, density fraction, and contact angle were analyzed. Classified and unclassified conditioning tests were carried out using different size fractions. The relationship between flotation indices (combustible recovery and flotation efficiency) and conditions (particle size, collector dosage, and conditioning stirring speed) was investigated. The results showed that the optimum conditions for different size fractions were different. The collector dosage and the conditioning stirring speed increased with the decrease of particle size. Meanwhile, the collision frequency between fine coal and diesel particles was much higher than the coarse particles, resulting most of the flotation agents adsorbed by fine particles, though the kinetic energy of coarse particles was higher. So a classified conditioning process was proposed. By conditioning optimizing, the flotation performance of classified conditioning was significantly improved compared with unclassified conditioning, especially for the +0.125 mm fractions.

Study on the Flotation Behavior of Fine Coal in the Cyclonic-Separation Process

ABSTRACT Fine-mineral separation has been a difficult problem in the mineral-processing field. A new cyclonic-flotation system was designed to solve the fine-mineral-recovery problem. Its design and operation are different from those of other cyclonic-flotation columns. In this study for the new cyclonic column, optimal reagent dosages, solid concentration, and aeration rate were determined. Many factors influence the operation of column flotation; however, in this study, mainly the effect of the circulation rate on the flotation behavior of the wide and narrow particle-size ranges of coal was investigated. The chosen circulation rates were 0.895, 1.044, 1.210, 1.369, 1.461, 1.578, 1.653, and 1.752 m/s. The wide particle size refers to a value of less than 0.5 mm. The narrow particle-size ranges refer to values from −250 to +75 μm, −75 to +45 μm, −45 μm, and +250 μm. The results showed that the combustible recovery of the narrow-size particles increased first and then decreased with the increasing circulation rate. The combustible recovery order of the narrow-size ranges in the same flotation time was as follows: −250 to +75 μm > −75 to +45 μm > −45 μm > +250 μm.

The effect of bubble size on oil-water separation efficiency for a novel oil-water separation column

Abstract Bubble size is a key factor in froth flotation for oil-water separation. In this paper, the bubble size which impacts on oil removal efficiency for a novel oil-water separation column was researched systematically. The bubble size distribution was researched by using the photographic method and Matlab software. In addition, several operating parameters which impact on the bubble size were investigated, including circulating pressure, aeration rate, and the foaming agent. Based on the results of experimental data and image analysis, the frother consumption and aeration rate has important influence on the bubble size. The bubble size can be controlled by adjusting the operation conditions including the circulating pressure, aeration rate, and the frother consumption. The optimum operating conditions for the oil-water separation column were determined. Furthermore, the mathematical model of oil removal efficiency for the oil-water separation column was established.

Removal of quinoline using various particle sizes anthracite: adsorption kinetics and adsorption isotherms

This work provided an adsorption method of the removal of quinoline by using anthracite of various particle sizes. The characteristics of the adsorbents were analyzed by Camsizer XT for particle size analysis, FT-IR for functional groups, X-ray diffusion for mineralogical composition, BrunauerEmmett-Teller for specific surface area and Barrett-Joyner-Halenda for pore size distribution. The average particle size of AC1-AC4 were 0.0342 mm, 0.1015 mm, 0.2103 mm and 0.3815 mm, respectively. The specific surface of the AC1-AC4 were 3.5 m2·g-1, 1.5 m2·g-1, 0.7 m2·g-1 and 0.1 m2·g-1 respectively. The adsorption capacity present a linear increase with the specific surface area increasing. To reveal the process of the adsorption, the adsorption kinetics and isotherms were performed. The kinetics data were analyzed by pseudo-first-order, pseudo-second-order and intra-particle diffusion equation using linearized correlation coefficient. Pseudo-second-order was found to best represent the kinetics data, which indicated that the adsorption of quinoline onto anthracite belongs to chemisorption. The equilibrium isotherms data were analyzed by Langmuir model and Freundlich model, the results indicated that the Freundlich model fit well for all the adsorption processes, which showed that the adsorption of quinoline onto anthracite belongs to endothermic reaction.