Comparison of coal separation characteristics based on different separating approaches in dry coal beneficiation flowsheet

The separation characteristic of raw coal from Luoyang mining area, China, was investigated by applying a dry coal beneficiation flowsheet with the dense medium gas-solid fluidized bed as main separating equipment. The experimental and simulation results indicate that the dense medium gas-solid fluidized bed can provide uniform distribution and stable fluctuation of bed densities at various heights. Two types of different separating approaches were compared using the dry coal beneficiation flowsheet. Compared with obtaining cleaning coal in the first stage of the flowsheet, a higher yield of the cleaning coal and better separation efficiency can be achieved when discharging gangue in the first stage. Finally, the results indicate that 64.86% pure cleaning coal with an ash content of 11.77% and 13.53% middlings were obtained, and 21.61% gangue was removed in two successive separation stages with the probable errors of 0.05 and 0.07 g/cm3, respectively.

Experimental investigation on separation characteristics of axial cyclone separator

Axial cyclone separator has been widely applied in chemical production as an efficient gas-liquid separation device.In this study,a new axial cyclone separator with integrated swirler and exhaust pipe is designed to achieve the development goal of compact structure for advanced engine,and the distribution characteristics of swirling flow patterns as well as the variation in separation characteristics are investigated under slug flow pattern.Based on flow visualizations and fluctuation characteristics of pressure signals,three typical flow patterns,namely,slug flow,swirling intermittent flow,and swirling annular flow,in the horizontal swirling separation flow are characterized.It is investigated how the inlet conditions affect the separation characteristic parameters.The separation purity and extreme points of the air separation efficiency are independent of the inlet liquid flow rate.The separation pressure drop is quadratically related to the inlet air flow rate.Based on the drift-flux model and other methods,the prediction methods for the air separation efficiency and pressure drop are proposed,and the prediction accuracy is within±20%,which may provide instructions for the practical application of axial cyclone separator.

Thermal stability and separation characteristics of anti-sticking layers of Pt/Cr films for the hot slumping technique

The thermal stability and separation characteristics of anti-sticking layers of Pt/Cr films are studied in this paper. Several types of adhesion layers were investigated： 10.0 nm Pt, 1.5 nm Cr ＋ 50.0 nm Pt, 2.5 nm Cr ＋ 50.0 nm Pt and 3.5 nm Cr ＋ 50.0 nm Pt fabricated using direct current magnetron sputtering. The variation of layer thickness, roughness, crystallization and surface topography of Pt/Cr films were analyzed by grazing incidence X-ray reflectometry, large angle X-ray diffraction and optical profiler before and after heating. 2.5 nm Cr ＋ 50.0 nm Pt film exhibits the best thermal stability and separation characteristics according to the heating and hot slumping experiments. The film was also applied as an anti-sticking layer to optimize the maximum temperature of the hot slumping technique.

Separate critical condition for ultrasonic vibration assisted grinding

Separate characteristic of the tangential ultrasonic vibration assisted grinding (TUAG) machining is analyzed based on TUAG process, and a critical speed formula is given to correctly set the machining parameters to insure the separate characteristics of TUAG process. The critical speed is not only related to the ultrasonic vibration amplitude and frequency, but also to the grinding wheel velocity and the cutting point space, and the grinding force can be decreased during the TUAG process with separability. Grinding force experiments are conducted, and the experimental results are in good agreement with the theoretical results.

A Stochastic Extension of Macroscopic Stability Criterion of Nonequilibrium Steady State in Chemical Reaction Systems Governed by Master Equation

By means of both the separation of the perturbation in accordance with characteristic parnmeters and the Kramers Moyal-expansion of the master equation, it is shown that the time derivative of the partial excess quantity of stochastic entropy due to the deviation from the most probable path is related to the responsibility of a system to the external macroscopic perturbations. This evolution rate of the partial excess stochastic entropy is equivalent to the partlal excess stochastic entropy production, as well as the stochastic excess entropy production rate based on the stochastic potential npproach. It appears also as an eqivalent quantity of the Gibbs excess entropy production for the Polsson distribution. The macroscopic stability of chemical reaction systems is dominnted by this new stochastic quantity when the local equilibrium thermodynamics is broken down .

Development of a static test apparatus for evaluating the performance of three PM2.5 separators commonly used in China

PM2.5 separator directly affects the accuracy of PM2.5 sampling.The specification testing and evaluation for PM2.5 separator is particularly important,especially under China’s wide variation of terrain and climate.In this study,first a static test apparatus based on polydisperse aerosol was established and calibrated to evaluate the performance of the PM2.5 separators.A uniform mixing chamber was developed to make particles mix completely.The aerosol concentration relative standard deviations of three test points at the same horizontal chamber position were less than 0.57%,and the particle size distribution obeyed logarithmic normal distribution with an R2 of 0.996.The flow rate deviation between the measurement and the set point flow rate agreed to within±1.0%in the range of-40 to 50℃.Secondly,the separation,flow and loading characteristics of three cyclone separators(VSCC-A,SCC-A and SCC112)were evaluated using this system.The results showed that the 50%cutoff sizes(D50)of the three cyclones were 2.48,2.47 and 2.44μm when worked at the manufacturer’s recommended flow rates,respectively.The geometric standard deviation(GSD)of the capture efficiency of VSCCA was 1.23,showed a slightly sharper than SCC-A(GSD=1.27),while the SCC112 did not meet the relevant indicator(GSD=1.2±0.1)with a GSD=1.44.The flow rate and loading test had a great effect on D50,while the GSD remained almost the same as before.In addition,the maintenance frequency under different air pollution conditions of the cyclones was summarized according to the loading test.

SIMULATION MODEL OF TECHNOLOGICAL MINERAL DRESSING PROCESSES

The authors worked out a simulation model of technological mineral dressing processes,in which two simulations of technological mineral dressing processes methods are used:transformed structural graph method and method of separation characteristics.The first method makes it possible to simulate technological mineral dressing processes at the design stage in conditions of feedstock,equipment and control information shortage.The second method is an effective instrument for operating plant simulation at the reengineering stage.Productivity and economic efficiency evaluations of the mineral dressing plant are appended to the model.