The Chinese Journal of Process Engineering

Direct Retrieval of Residence Time Distribution from the Simulated Flow Field in Continuous Flow Reactors

Mao Zai-sha YANG Chao FENG Xin

Chin. J. Process Eng.. 2017, 17(1): 1-10. DOI: 10.12034/j.issn.1009-606X.216256

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Residence time distribution (RTD) is a smart concept in chemical reaction engineering, and has been playing an important role in diagnosis and optimization of chemical reactors. RTD is conventionally determined by experiment by using a tracer to track the motion of reacting fluids. Currently the numerical simulation of RTD also follows the same route. In this work, the numerical method of retrieving RTD directly from the simulated flow field is proposed in view that the RTD itself is the intrinsic property of the fluid flow in a reactor. RTD can be determined by following the streamlines of all entering fluid particles, or by accumulating the residence time increment within all control volumes that a fluid particle traverses in a random way. A numerical case of a radial flow reactor is presented to demonstrate the equivalence of these two methods.

Wavelet Analysis of Dynamic Pressure in Vortex Quick Separation System with Annular Pre-stripper

LI Zhi LI Meng ZHANG Bo-feng LU Chun-xi

. 2017, 17(1): 11-20. DOI: 10.12034/j.issn.1009-606X.216252

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An experiment was performed to measure the axial pressure fluctuation of the vortex quick separation system with annular pre-stripper. In order to give suggestions to the operation stability of actual industrial device through analyzing the pressure fluctuation characteristics and mechanism. As is shown in the experimental results, the axial pressure fluctuations have great similarity in the shape of the curves. The strength of the fluctuation increased with ejection gas velocity and the particulate mass flow rate increasing. Through the wavelet analysis, the frequency range of this device is approximately 1.5~12.5 Hz with a period of 7~10 s. It is found that there is an enormous pressure fluctuation above the quick separator and a vortex zone is found there. The circumferential pressure pulsations are basically the same, and the radial r/R=0.4~0.7 has a bigger vortex zone and the pressure fluctuation intensity is lower. As for industrial device operating stability, it is suggested that the injection gas velocity of the quick separation head is in the range of 18~24 m/s and the riser particle mass flow rate is more than 90 kg/(m2?s), the device can run stability.

Numerical Simulation of Solid Particle Distribution and Suspension Characteristics in High Concentration Stirred Tank

SHENG Yong LIU Yao-ting HAN Li-hui LIU Qing

. 2017, 17(1): 21-28. DOI: 10.12034/j.issn.1009-606X.216273

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Solid-liquid suspension characteristics of stirred tank with solid holdup 9.2% was simulated by Euler-Euler two fluid model. The simulation and prediction results of two kinds of modified drag coefficient models were compared. Distribution of solid holdup and the suspension uniformity were investigated. The results showed that there were some dense deposition in the bottom of tank when the rotational speed was lower than 600 r/min. As the rotational speed increased from 400 r/min to 1100 r/min, the accumulation height decreased from 0.16 to 0, the deposition area contracted and disappeared at last. Under the action of centrifugal force, the solid particles in the circulating flow moved toward far-vortex direction. Solid holdup at the center of vortex was lower, so the suspension uniformity was drastically reduced. The two-phase flow could be divided into upper and lower circulation regions at the height of z/H=1/3. The distribution of particles was affected by the confluence of circulating flow, and the solid phase was dispersed with the flow field in the radial direction. Suspension uniformity tends to be stable at 0.5~0.7 with the increase of the height. As the rotational speed increased from 400 r/min to 1100 r/min, the value of σ in the upper circulation regions decreased by 37.2%.

Numerical Simulation of Oil?Water Separation Characteristics in Tee Tube

HU Kun AI Zhi-jiu FU Bi-wei LI Jie LI Zhen-bei

. 2017, 17(1): 29-34. DOI: 10.12034/j.issn.1009-606X.216194

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The flow field of oil?Water in tee tube by using mixture multiphase model was studied, in addition to study the separation efficiency of tee tube response to the ratio of oil at inlet，the split ratio at outlet, the velocity of inlet, the length of branch tube and the length of main tube. The result show that: oil gathered and separated at the intersection of branch tube and main tube. The reason of oil gathered at main tube was caused by the gravity, and at branch tube, oil gathered phenomenon was mainly due to the centrifugal separation caused by the density difference between oil and water. Oil content at main entrance significant influence on separation efficiency of tee tube, and separation efficiency reduced with the increase of inlet oil content, so tee tube separator suit for separating the oil-water which has low oil content. Study result shows the efficiency would be increased when increased the split ratio, that means that can improve the separation efficiency by mounting throttle at outlet of main tube. The separation efficiency is not sensitive to the length of branch tube and outlet of main tube, so it can be only in accordance with the requirements of the manufacturing and installation in tee tube design process.

Performance of Sieve Runde Tray

YANG Song-quan CHU Ya-zhi CAO Wan-wan LIU Yan WANG Ling

. 2017, 17(1): 35-40. DOI: 10.12034/j.issn.1009-606X.216221

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The hydrodynamic performance of sieve runde tray with opening ratio of 15%, 25%, 35% was studied with water-air system as medium. The results showed that the pressure drop and the gas holdup of sieve runde tray decreases with the increase of the opening ratio. The flooding velocity and operating flexibility increases with the increase of the opening ratio. Dry pressure drop, total pressure drop and gas holdup of sieve runde type with the opening ratio of 35% were lower than that with opening ratio of 15% and 25%, and operating flexibility is greater than that with opening ratio 15% and 25% .

CFD Simulation of Gas Phase Flow Field in a Rotating Zigzag Bed

ZHANG Bin LI Yu-min WANG Hong-jun

. 2017, 17(1): 41-46. DOI: 10.12034/j.issn.1009-606X.216243

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The gas phase flow field and gas pressure in a rotating zigzag bed were simulated with computational fluid dynamics (CFD). The effects of rotational speed and gas flow rate on the inner and outer of the rotor velocity distribution and gas pressure was studied and analyzed. The model was validated by experimental results. The results show that the averaged relative error between experiments and calculation is less than 9%. Gases from outside into the rotor, the rotor speed obvious changes have taken place. Tangential velocity of total speed by 76.1%~76.1%, axial velocity and radial velocity is very small. As the gas flow rate and rotating speed increases, the tangential velocity increase obviously. Gas flow inside of the rotor, there is a low pressure value and a high pressure value in the near rotation baffle, there is a large and a small vortex, a counterclockwise, a clockwise. In their border, gas flow more severe and the gas outlet close to the shaft, also gas existing reflux, but speed is smaller.

Mass Transfer Performance of Layered Packing Cross-flow Rotating Packed Bed

GAO Ya-jie YUAN Zhi-guo LIU You-zhi LIU Hui-jun DU Jie LIANG Peng-fei

. 2017, 17(1): 47-51. DOI: 10.12034/j.issn.1009-606X.216234

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In order to verify the intensification effect of LPC?RPB (Layered Packing Cross-flow Rotating Packed Bed) on gas-side mass transfer, optimize the device structure and improve the mass transfer efficiency, the gas-film limited system of the absorption process of SO2 by NaOH solution was applied in this work. The influence of high gravity factor β, empty bed gas velocity u and liquid spray density q on volumetric gas-phase mass transfer coefficients (kyae) and the intensification effect were investigated. The results indicated that the kyae values increased with the increase of β, u and q. Under the conditions of β=55, u=1.53 m/s and q=3 m3/(m2?h), kyae can reach 28 s?1, which is 10~75 times higher than the spray column and 1.4~2.2 times than the traditional cross-flow rotating packed bed. Besides, with the characteristics of milder operating conditions, simpler structure and lower energy consumption compared to SP?RPB (Split Packing Rotating Packed Bed), LPC?RPB showed a good performance of effectively intensifying the gas-film controlled mass transfer process.

Flow, Suspension and Mixing Characteristics of Eccentric Stirring

BI Hua-fei ZHOU Kun HUANG Xiong-bin

. 2017, 17(1): 52-57. DOI: 10.12034/j.issn.1009-606X.216244

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The relationship of eccentricity ratio with the vortex motion trajectory, the depth of the vortex, the uniform drop-down velocity and the mixing time of CBY impeller were investigated. The experiments were carried out in a flat bottomed cylindrical stirred tank with the diameter 476 mm. The results showed that vortex center do linear motion and arc motion when eccentricity ratio before and after 0.45. The trajectory of the vortex center satisfies a certain law. The depth of the vortex is affected by the eccentricity ratio much more than rotational speed and material viscosity. In this experimental condition, the effect of eccentricity is 1.9 times of the speed to the drop rate of liquid level and 4.4 times of material viscosity. Vortex depth reduces as the eccentricity ratio increases. It satisfies certain linear rule. The uniform drop-down velocity of polyvinyl chloride with the diameter 4 mm increases first and then decreases as the eccentricity ratio increases. The eccentricity ratio at minimum inflection point is 0.4~0.5. The best eccentricity speed increased by 20.3% when the liquid level rises from 1.0T to 0.6T (T is diameter of stirred tank). Stirring power consumption is increased. Adding a single baffle will change the liquid flow field in the tank and make the vortex disappear. But in the same adding material position, the mixing time of full baffle is shorter than that no baffle 66.9%. The mixing effect was obviously enhanced.

Flow Uniform of Mini-channel Heat Sink with Different Structures

LU Jin-li ZHAO Wei CHI Bang-jie HAN Ya-fang QIAN Fu-ping

. 2017, 17(1): 58-63. DOI: 10.12034/j.issn.1009-606X.216247

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Numerical simulation is conducted using pure water as medium to investigate the flow distribution and convective heat transfer characteristic in parallel mini-channel heat sink. The effect of inlet and outlet arrangements, header structure and aspect ratio of channel on flow distribution and heat transfer are analyzed. The results showed that the flow uniformity of heat sink with I-type and rectangular header structure is better than other structures, and has the minimum standard deviation of mass flow rate (SI=0.071). For the same hydraulic diameter, the aspect ratio of channel has a little effect on average temperature of heat surface, whereas it has a significant effect on heat transfer coefficient, and the convective heat transfer coefficient improve 23.9% when the aspect ratio changed from 1 to 5. Base on field synergy principle, the synergy angle between the velocity and temperature field decrease with the increasing of aspect ratio, it suggest that heat transfer is enhanced.

PIV Experiment on Flow Filed of Spinning Disc Reactor

GUO Jia-xin ZHANG Qiao-ling LIU You-zhi CHANG Jun-bo

. 2017, 17(1): 64-68. DOI: 10.12034/j.issn.1009-606X.216254

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Particle image velocimetry (PIV) was applied to a spinning disc reactor, the instantaneous velocity distributions of flow filed on the spinning disc were obtained, and the effect of rotational speed and flow rate had been discussed. The experimental results revealed that the instantaneous velocity is firstly decreased and then increased from center to edge of the disc. The velocity field on disc center is controlled by flow rate, relative radial velocity increases with increasing flow rate. The velocity field on disc edge is controlled by rotational speeds, relative circumferential velocity increases with increasing rotational speeds. In the range of experimental conditions, critical radius (Rc) is about 50 mm, disc radius should be larger than Rc, appropriately.

Leaching of Rare Earth and Impurities in Phosphorite Ore by Acid

JIN Hui-xin ZHENG Xiao-qian YANG Song WU Bao-zhen

. 2017, 17(1): 69-74. DOI: 10.12034/j.issn.1009-606X.216237

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The leaching law of rare earth and impurities in the process of decomposition of phosphate ore containing rare earth by mixtures of sulfuric and phosphoric acids was studied. The results showed that leaching rates of rare earth oxides in Zhijin phosphate ore and Fanshan phosphate ore are 62.73% and 52.84%, respectively, under the conditions of concentration of phosphoric acid of 8.6 mol/L, 3 h leaching time, excessive coefficient of sulfuric acid of 1.00, temperature at 80℃, liquid?solid ratio at 6:1 L/g. Within a certain range, the leaching rates of rare earth in two phosphate ores increase with the increasing of time and liquid?solid ratio. The leaching rate both increase at first and then decrease with the increasing of temperature and excessive coefficient of sulfuric acid. The leaching rates of the main components (Y2O3, La2O3, CeO2 and Nd2O3) in light rare earth decrease with the increasing of atomic number. Although ores are different, the law of rare earth leached out to the phosphoric solution is the same.

Recovery of Nickel(II) and Cobalt(II) from Simulated Multi-metal Wastewater by Simutaneous Extraction with Synergistic Mixture

ZHANG De-Jun ZHU Shan LI Ji-yuan HU Hui-ping Liu Shi-jun Shi-junLIU

. 2017, 17(1): 75-83. DOI: 10.12034/j.issn.1009-606X.216250

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A synergistic mixture containing LIX 63 and Versatic 10 with/without TBP was used to simultaneously extract and recover nickel(II) and cobalt(II) from manganese(II), magnesium(II) and calcium(II) in simulated multi-metal wastewater. Stripping kinetics of nickel(II) were improved by adding TBP to the synergistic mixture system containing LIX 63 and Versatic 10. The effects of extraction and stripping conditions on the nickel(II) and cobalt(II) extraction and the removal ratios of impurities were investigated. The results show that when concentrations of LIX 63, Versatic 10 and TBP were correspondingly 0.6, 0.4 and 0.8 mol/L, the respective synergistic extraction coefficient of nickel(II) and cobalt(II) reach to a maximum value of 33.29 and 8.23, and approximately 90% nickel(II) was stripped within 30 min. It is recommended that the metal extraction should be carried out at 40±0.5℃ with equilibrium pH of 4.5, A/O ratio of 1:1 and saponification ratio of 40%. The loaded organic solution was stripped with 1 mol/L H2SO4 solution. Based on the McCabe–Thiele diagrams, through three counter-current extraction stages at an A/O ratio of 1:1, over 98.6% nickel(II) and 99.9% cobalt(II) were correspondingly extracted. Through three counter-current stripping stages at an A/O ratio of 1:10, the loaded strip liquor contained 88.12 g/L nickel(II), 4.52 g/L cobalt(II), 1.21 g/L manganese(II), 0.27 g/L magnesium(II) and below 0.2 mg/L calcium(II).

Separation of V2O5 and Cr(VI) from Vanadium Slag Leaching Solution by Ion Exchange Resin

YANG Ya-ling YAN Wen-bin GAO Feng

Chin. J. Process Eng.. 2017, 17(1): 84-91. DOI: 10.12034/j.issn.1009-606X.216217

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Five ion-exchange resin was tested for adsorption of vanadium and chromium, and their adsorption capacities and adsorption rates towards vanadium and chromium were compared. Some effecting factors such as pH value, contact time, temperature and initial concentration of vanadium on separating chromium and vanadium by anion resin were investigated. The results showed that the SQ-20A resin has strong adsorption capacity for vanadium while has weak adsorption capacity for chromium, the maximum separation factor have reached 251.23 on the conditions of pH=9.0 and temperature 298 K. The adsorption of vanadium on the SQ-20A resin was an endothermic process, and the adsorption isotherm fitted to the Langmuir and Frendlich models simultaneously. The adsorption kinetics follwed the Pseudo-second-order model, and the adsorption rate was mainly controlled by particle diffusion. The static adsorption experiments showed that the SQ-20A resin has good selective adsorption capacity for vanadium, which could meet the demands of separating chromium and vanadium.

Removal of Low Concentration Dust from Gas by Wet Dust Collection Technology under High Gravity

WANG Tan QI Gui-sheng LIU You-zhi SONG Bin WU Xiao-li ZHENG Qi

. 2017, 17(1): 92-96. DOI: 10.12034/j.issn.1009-606X.216229

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Effect of high gravity factor, gas flow rate, and liquid flow rate on dust removal efficiency of a rotating packed bed (RPB) was investigated at dust concentration as low as 200 mg/m3, in which coal-fired fly ash and RPB were used as experimental dust and dust removal equipment, respectively. The grade collection efficiency of the RPB was carried out and the concentration range of dust that removed effeciently by RPB was explored at dust concentration lower than 200 mg/m3. Results show that, at conditions that high gravity factor of 163, gas flow rate of 400 m3/h, and liquid flow rate of 0.5 m3/h, dust removal efficiency is as high as 93.18% for a 200 mg/m3 inlet dust concentration. Grade collection efficiency curves show that the cut size of a RPB is about 0.08 μm, dust removal efficiency for particle size of 2.5 μm is approximately 95%?99.75%. Dust removal efficiency is 81.25% with inlet dust concentration of 30 mg/m3.

Hydrogen Peroxide Presoak/Steam Explosion Degumming Process and Performance of Kenaf Fibers

Yan SONG LI Xian-bo JIANG Wei

. 2017, 17(1): 97-102. DOI: 10.12034/j.issn.1009-606X.216218

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In order to improve the dispersion of kenaf fibers, hydrogen peroxide (H2O2) presoak combined with steam explosion degumming was carried out. The experiment of microstructure characterization, chemical composition analysis, and crystallinity were analyzed. The single factor experiment results showed that the optimal H2O2 presoak/steam explosion conditions are as follows: concentration of H2O2 in 0.6 mol/L, presoak time in 1 h, steam pressure of 1.2 MPa, and steam pressure maintaining time of 60 s. Optimized fiber fineness can reach 180 with the breaking tenacity of 5.28 cN/dtex. It is approximately double compared with kenaf fiber treated by distilled water/steam explosion. It can be found that steam explosion presoaked with H2O2 can remove the non-cellulosic materials like hemicellulose and lignin effectively, make the fiber surface clean and smooth, and increase its crystallization index without destroying the crystal type of kenaf cellulose.

Ammonia?Nitrogen Adsorption Process and Characteristic of Compound Modification Zeolite Granules

YANG Bing-fei LEI Jian-du DONG Ying-bo WANG Liang

. 2017, 17(1): 103-109. DOI: 10.12034/j.issn.1009-606X.216158

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Ammonia-nitrogen adsorption process and characteristic were studied on the compound modification zeolite granules, which were made by zeolite power and modified by NaOH solution, NaCl solution and roasting successively before granulation, and with the size of Φ1.50 mm×2.50 mm. Isothermal equilibrium adsorption, adsorption kinetics characteristic，adsorption rate control steps and adsorption thermodynamics were main investigated in different conditions respectively. The results showed when PH value was equal to 7.00 and adsorption temperature was 298 K, ammonia-nitrogen adsorption process of the zeolite granules conform to Langmuir adsorption isotherm, the fitted equation was y=0.0084x+0.2857 and the correlation coefficient (R2) was 0.9936. Pseudo?second order reaction kinetics equation can describe the adsorption kinetics characteristics and the fitted equation was y=0.3401x+8.9684 and the correlation coefficient (R2) was 0.9993. Beside, the ammonia-nitrogen adsorption process was mainly controlled by film diffusion (y=0.0172x, R2=0.9809) in whole process and controlled by which and intra-particle diffusion process (y=0.0869x+1.4917, R2=0.9798) in 60 min later together. In addition, adsorption thermodynamics showed that ammonia?nitrogen adsorption process of the zeolite granules belong to spontaneous process, adsorption rate quicken with temperature rising. The adsorption process also belong to endothermic process, adsorption capacity increase with temperature rising. Entropy effect was the main driver of the adsorption process.

Evaluation and Optimization of Oxygen Enriched Combustion Characteristics of Blended Coals by Response Surface Methodology

ZHAO Rong YANG Shu-ping QING Shan WANG Ming-yue LIANG Mei-ling GUI Zhao

. 2017, 17(1): 110-118. DOI: 10.12034/j.issn.1009-606X.216249

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The essay studies on the combustion of blended samples of Xiaolongtan lignite (X), Fuyuan bituminous coal (F) of and Zhaotong lignite (Z) and their combustion characteristics were analyzed by comparing the results of thermogravimetric experiments with different oxygen concentrations and heating rates. The oxygen concentration, heating rate and mass ratio of mixture coal were optimized by applying the optimization software of response surface Design-Expert 8.0.6. The results showed that the temperature of coal ignition and burnout decreased and the combustion time was shorted when oxygen was enriched. When the concentration of oxygen reached the point of 30%(?) the variation of combustion characteristic parameters was minim, so the oxygen concentration in practical application should be controlled around 30%. The activation energy was higher at the later period of pulverized coal combustion, and the activation energy and the pre-exponential factor was increased with the increase of oxygen concentration. Besides, when heating rate grew, the temperature of coal ignition and burnout temperature increased, the burning time was prolonged, while the stability and combustibility was worse. It showed that the coal combustibility improved with the increase of oxygen concentration. The value range of each factor was designed in Criteria of Design-Expert 8.0.6. Set the combustible index and the combustion characteristic index the maximum value and set burnout temperature and investment cost the minimum value, when the mass ratio of Xiaolongtan lignite:Zhaotong lignite:Fuyuan bituminous coal was 100:55.07:1, the four evaluating indicators were relatively optimum, combustibility index was 43.56×10?7, combustion characteristic index was 4.27×10?10, burnout temperature was 680.01℃, cost was 252.49 ￥/t.

Electrochemical Behavior of Cr(II) Ion in NaCl?KCl Melt at W Electrode

Liu Wei XIAO Sai-jun WANG Zhen

. 2017, 17(1): 119-122. DOI: 10.12034/j.issn.1009-606X.216264

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The cathodic behavior of Cr(II) ion at W electrode in NaCl?KCl molten salts at a temperature of 710℃ was investigated by cyclic voltammetry, square wave voltammetry, chronopotentiometry. The results indicates that the reduction process of Cr(II) to Cr at W electrode was a one step process: Cr2++2e?=Cr. The reduction of Cr(II) is a quasi-reversible process controlled by diffusion mass transfer. The diffusion coefficients of Cr(II) calculated by the data of cyclic voltammetry and chronopotentiometry, is 1.27?10?5 and 2.24?10?5 cm2/s, respectively. Potentiostatic electrolysis performed on the W electrode proved the feasibility of electrodepositing metallic chromium in the molten NaCl?KCl?CrCl2 system.

Decomposition Kinetics of Ammonium Bicarbonate and Its Dissolution Property in Weak Alkaline Solution

LIU Wei ZHANG Yan LIU Wen-li

Chin. J. Process Eng.. 2017, 17(1): 123-129. DOI: 10.12034/j.issn.1009-606X.216270

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Formaldehyde titration method was used to study the terminal decomposition process of the product of the ammonia method. The concentration variation of main ions was measured when the ammonium bicarbonate solution with initial concentration from 3.0%~7.9% decomposed at 323~363 K. Besides that the determination of the solubility for ammonium bicarbonate in the NH4HCO3?Na2CO3?H2O system from 288 to 313 K was carried by a dynamic method. The results show that the concentration of HCO3? ion falls sharply within the first 30 min and then decreases slowly. The decomposition rate of ammonium bicarbonate solution grows as the temperature rises, at the same temperature the higher the concentration of ammonium bicarbonate solution is, the shorter equilibrium time will be needed. Decomposition process of ammonium bicarbonate solution can be described by the Lageren equation after calculated; It has also been discovered that the solubility of NH4HCO3 increased with the rising of temperature, and increased firstly and then decreased gradually with increasing the concentration of Na2CO3 solution at the same temperature. With a peaked value at Na2CO3 concentration was 0.1 mol/kg when the equilibrium phase changed from NH4HCO3 to NaHCO3 in this aqueous system.

Optimizing Removal of Simulated Wastewater Using CPAM Combined with PAC by Response Surface Methodology

MA Jiang-ya SHI Jun YANG Zhi-cheng FU Xue FU Kun SUN Yong-jun ZHANG Yuan-lin

Chin. J. Process Eng.. 2017, 17(1): 130-137. DOI: 10.12034/j.issn.1009-606X.216251

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A type of cationic polyacrylamide (CPAM) prepared in laboratory combined with polyaluminum chloride (PAC) was applied in flocculation of simulated kaolin wastewater. The Box?Behnken mathematical relational model between transmittance and affecting factors was established, and the conditions of flocculation performance were optimized. The optimum flocculation conditions were determined as follows: PAC dosage of 38.39 mg/L, CPAM dosage of 1.09 mg/L, rapid mixing time of 9 min and pH of 5.18. Under these optimized conditions, the transmittance of processed water arrived at 99%. The results confirmed that, compared with separately application, flocculation through CPAM combined with PAC in low dosage can be effectively. Simultaneously, dense flocs were generated in flocculation, which have a strong ability to resist shear and fast sedimentation speed.

The Process of High Efficiency Dealkalization and Ore Blending in Ironmaking of the Extracted Vanadium Residue

LI Lan-jie ZHAO Bei-bei WANG Hai-xu BAI Rui-guo CHEN Dong-hui

. 2017, 17(1): 138-143. DOI: 10.12034/j.issn.1009-606X.216215

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The rule of removing alkali from the extracted vanadium residue was investigated under atmospheric pressure and constant temperature water bath through single factor experiment, and the parameters and the route of the ore blending and sintering process of the extracted vanadium residue after removal of alkali were determined. The experimental results showed that adding CaO in alkaline system, sodalited and cancrinite in the extracted vanadium residue is no longer stable solid phase, two Na+ was replaced by Ca2+ to produce a more insoluble calcium garnet phase, so that Na+ dissolved into the solution. Under the additive amount of NaOH was 20% of the extracted vanadium residue and the excess coefficient of CaO was 2, the content of Na2O in the extracted vanadium residue was decreased to 0.9%. Using the extracted vanadium residue after removal of alkali replaced of low vanadium high grade iron concentrate powder for ore blending and iron making, the added amount was about 20 kg/t, and the amount had no influence on the sintering parameters. And the sinter indexes of finished product were improved obviously after adding residue thanking for the low grade of SiO2 in the vanadium-titanium ore of Chengsteel Group Co., Ltd., and the drum index also improved by 0.6%.

Effect of Alloying and Rare Earth Modification on Thermal Conductivity and Wear Resistance of Austenitic Medium Manganese Steel

CHEN Shao-chun LIN Xin-qiang ZHU Kang-zheng LU Yue-mei YE Rong-hua LIN Yang LIN Xiao-ying

. 2017, 17(1): 144-150. DOI: 10.12034/j.issn.1009-606X.216220

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Aimed at the problems of the austenitic manganese steel, such as the thermal conductivity is poor, the heat is not easy to export and the workpiece is easy to heat deformation, which leads to the processing precision is difficult to guarantee, and the cutting speed cannot be improved, we study the effects of Cr, Mo and rare earth alloy elements on thermal conductivity and wear resistance of the austenitic manganese steel herein. The results showed that the thermal conductivity can be enhanced of 19.6%, the wearing rate is reduced by 54.5%, and crystal grain is improved from grade 3 to 5 comparing austenitic medium manganese steel to the traditional high manganese, when the Cr content is about 1%(?), the content of Mo is about 2%(?), and 0.15%(?) of the rare earth is added.

Study on the Activity and Microstructure of Lime

HAO Su-ju REN Qian-qian ZHANG Yu-zhu JIANG Wu-feng HAO Hua-qiang BO He DONG Jian-jun

. 2017, 17(1): 151-155. DOI: 10.12034/j.issn.1009-606X.216216

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The micro structure on the grain size, specific surface area and the pore structure of lime were analyzed by means of the field emission SEM and automatic pressure mercury, revealing the influence of calcination time, temperature and pressure on the activity of lime, determining the relationship between microstructure of lime and lime activity. The results showed that lime activity increases firstly and then decreases with the increasing of specific surface area, average pore diameter and pore volume of lime. When specific surface area is 2.0 m2/g around, the average pore size is about 850 nm, the hole volume is about 0.58 mL/g, the activity of lime is highest.

Design and Application of the Recovery System of Waste Heat from Flue Gas by New Radial Eccentric Heat Pipe

ZHANG Hai-song ZHAN Hong-ren LI Xiao-tang HAN Ying BI Shi-hui XIE Guo-wei

. 2017, 17(1): 156-161. DOI: 10.12034/j.issn.1009-606X.216222

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According to the problems of the reovery system of waste heat from flue gas, a waste boiler with a radial eccentric heat pipe as the heat transfer unit is designed, which is applicable to poor working conditions containing acid gas, dust and others. The radial eccentric heat pipe technology and heat exchanger are expounded and analyzed, and key points of radial eccentric heat pipe waste heat boiler technology are analyzed in the design conluding safety length ratio of the radial eccentric is derived. In practical engineering, the radial eccentric heat pipe waste heat boiler is investigated. The results show that the eccentric radial heat pipe waste heat boiler has higher performance and the waste heat recovery efficiency is up to 92.5%. Also low temperature corrosion is avoided, no evidence impacting on normal production has been found during the past three years. More over, the expected service life of heat transfer tube can reach to five years.

Affecting Factors and Optimal Operation Conditions of Improved Carrousel Oxidation Ditch for Nitrogen Removal

GAO Jian-ping HUANG Jian-feng ZHANG Liang， CAI Shi-jun

. 2017, 17(1): 162-169. DOI: 10.12034/j.issn.1009-606X.216223

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One problem of improved carrousel oxidation ditch of a sewage plant is the lower total nitrogen removal rate. Two solutions are put forward after analyzing the factors such as dissolved oxygen, C/N, sludge retention time, sludge return ratio and temperature. The results showed that power output of aerator is adjusted in accordance with the change of dissolved oxygen concentration monitoring in the corresponding site, which can also reduce energy consumption of the system. C/N of the anoxic zone is increased by adding one site of influent in anoxic zone. After reconstruction, the COD, BOD5 and NH4+?N of effluent are stable, and the total nitrogen removal rate is significantly increased from 56.25% to 68.80%.

Three-dimensional Microstructure Reconstruction of Pleated Air Filter Media and Simulation of Its Performance in Dust Filtration Stage

XU Jin-rui QIAN Fu-Ping LU Jin-li HAN Yun-long

. 2017, 17(1): 170-177. DOI: 10.12034/j.issn.1009-606X.216190

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Three-dimensional random model of the pleated air filter media was built based on the actual melt blown fiber, and its microstructure was established considering a series of parameters, including pleated angle, layer, diameter, number of fibers, curvature, and so on, which had dynamic control of the pleated air filter media. The established model was basically similar to the actual electron microscope image of filter media. On this basis, the filtration characteristic of the pleated air filter media in the dust filtration stage was simulated using CFD?DEM coupling method, and the simulation results were compared with the relevant empirical correlations. The results show that the error between the simulation results and the empirical correlations is less than 10%, which indicates that the calculation based on CFD?DEM coupling method was feasible. In the dust filtration stage, the pressure drop increases nonlinearly with the increasing number of deposition particles at the same inlet gas velocity. The increased pressure drop increases with the increase of filtration time under different inlet velocities, the maximum increased pressure drop (0.214 Pa) appears at 0.6 m/s of the inlet gas velocity and the minimal increased pressure drop (0.133 Pa) appears at 0.4 m/s of the inlet gas velocity. The phenomenon of the particles’ deposition and agglomeration is obvious when the filtration time, T is 3.216 ms, and this phenomenon is more apparent in the penetrated region of fibers, which also indicates that the arrangement of fibers have significant influence on the deposition of particles.

Establishment and Validation of Multi-objective Optimization Model of Blast Furnace

CHE Xiao-rui ZHANG Zong-wang ZHANG Hong-bo

. 2017, 17(1): 178-182. DOI: 10.12034/j.issn.1009-606X.216267

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Blast furnace iron-making optimization model is based on material balance and heat balance of the iron-making process. An optimized mathematical mode, whose objective function were the energy consumption and cost, is established using the method of linear programming. Optimization variables and constraints were determined according to the objective function and the characteristics of the blast furnace process. The optimized results were obtained by designing programs with Lingo software, and the multi-objective optimization was obtained by single objective optimization. The superiority of the model was verified by comparing the calculated data with the actual production data. The optimization model, together with the Origin software, was used to analyze the impact of factors such as the coke rate, blast temperature, injection quantity of coke oven gas on energy consumption and cost. At the meantime, some methods to reduce energy consumption were introduced. The results showed that model is optimized to reduce energy consumption by 24.1 kg/t and cost saved selections 42.7 ￥/t compared with the blast furnace production data, according to the standard coal gauge. Hence, there are several measures to reduce energy consumption and cost savings for the blast furnace: to reduce coke rate, improve the coal injection ratio, increase the amount of coke oven gas injection, enrich the oxygen and improve hot blast temperature.

The pH Regulation Strategy for boosting Production of ?-Ketoglutaric Acid by Yarrowia lipolytica

Zhang Hai-lin FANG Fang LIU Song ZENG Wei-zhu ZHOU Jing-wen CHEN Jian,

Chin. J. Process Eng.. 2017, 17(1): 183-187. DOI: 10.12034/j.issn.1009-606X.216241

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To promote the production of ?-ketoglutaric acid (?-KG) by Yarrowia lipolytica WSH-Z06 with glycerol as the carbon source, the effects of pH on cell growth and ?-KG production were compared, and a strategy of controlling biomass by pH regulation with analysis of kinetic characteristics was established. Furthermore, the effect of biomass concentration on ?-KG production was compared. The results showed that the pH value was maintained at 6.0 at beginning of fermentation, and decreased naturally to 3.0 after the biomass concentration reached up to 10 g/L, then maintained till the end of fermentation. Using this strategy, the maximum ?-KG production reached up to 54.0 g/L, the production and productivity were 19.3% and 17.8% higher than the corresponding values of control group, respectively.

Optimizing Preparation of Modified Na-Montmorillonite Based on Uniform Design and Multivariate Nonlinear Regression

ZHANG Hao LIU Xiu-yu ZONG Zhi-fang

. 2017, 17(1): 188-192. DOI: 10.12034/j.issn.1009-606X.216259

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Modified Na-montmorillonite was prepared with cetyl trimethyl ammonium bromide (CTAB) as modifier. The effect of deionized water amount, CTAB amount, stirring speed, mixing temperature and drop in time on modified Na-montmorillonite interlamellar spacing was studied by uniform design and multivariate nonlinear regression. Composition, structure and microstructure of modified Na-montmorillonite were characterized. The results showed that compatibility of modified Na-montmorillonite increased, interlamellar spacing increased significantly. Primary and secondary sequence of factors on modified Na-montmorillonite interlamellar spacing is CTAB amount>mixing temperature>stirring speed>deionized water amount>drop in time. The optimization pconditions of modified Na-montmorillonite is deionized water amount 358 g, CTAB amount 0.47 g, stirring speed 2853 r/min, mixing temperature 75.6℃ and drop in time 128 min.

Research Advances in Pyrolysis Processes and Catalysts of Waste Tires

SHUAI Kun YAN Yu-yuan CUI Xiao-long HAN Rui-xuan LI Shuang

. 2017, 17(1): 193-200. DOI: 10.12034/j.issn.1009-606X.216178

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Recent advances in the pyrolysis processes and catalysts of waste tires, including the reaction of conditions (temperature, pressure, carrier gas and particle size), catalysts and reactors were discussed and summarized. The operating conditions and the type of reactors directly influence the distribution of pyrolysis products, however, due to the balance between thermodynamics and kinetics as well as heat transfer, mass transfer consideration, it is difficult to obtain desired products only by tuning the operating conditions. Fabrication of the structure and composition of catalysts offers an effective way to improve the yield and quality of target products, promoting high value-added products (monocylic aromatics, cyclohexane and etc.), reducing sulfur in the pyrolytic oil. The problem of separation and coking of catalysts hinders the progress of waste tires pyrolysis, and most of current research were operated in micro or small-scale reactors, therefore deep exploration of the reaction mechanism and molecular structure of waste tires still need to be studied in detail. The design and fabrication of efficient, sulfur-resistant catalysts and large scale pyrolysis reactor were proposed to be the main subject of future research.

Research Advances in Organic Phase Change Materials for Technology of Thermal Enhancement

ZHANG Tian-chi YU Hai-yun MAO Ai-qin ZHENG Cui-hong DING Pei-pei XIAO De-wei ZHANG Hao

. 2017, 17(1): 201-208. DOI: 10.12034/j.issn.1009-606X.216225

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Organic phase change materials is an important branch of phase change materials. Its main drawback is lower thermal conductivity. It has greatly restricted the application. The general method is using the composite method to enhance the thermal conductivity of the system, such as the addition of nanoparticles, micro-encapsulation, porous matrix adsorption, etc. In this review, the technique, process, raw materials, mechanism and existing problems of organic phase change materials are presented, and the future research and development direction are prospected.

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