Influence of Na2 CO3 as Additive on Direct Reduction of Boron-bearing Magnetite Concentrate

Boron-bearing magnetite concentrate is typically characterized by low grade of iron and boron (wTFe=51%-54%,wB2 O3=6%-8%),as well as the close intergrowth of ascharite phase and magnetite phase.A promising technology was proposed to separate iron and boron by coupling the direct reduction of iron oxides and Na activation of boron minerals together.The influence of Na2 CO3 as additive on the direct reduction of boron-bearing magnetite was studied by chemical analysis,kinetic analysis,XRD analysis and SEM analysis.The results showed that the ad-dition of Na2 CO3 not only activated boron minerals,but also reduced the activation energy of the reaction and pro-moted the reduction of iron oxides.Besides,the addition of Na2 CO3 changed the composition and melting point of non-ferrous phase,and then promoted the growth and aggregation of iron grains,which was conducive to the subse-quent magnetic separation.Thus,the coupling of the two processes is advantageous.     

An apparatus and a method for determining the slip resistance of shoes and floors by simulation of human foot motions

An apparatus to measure the coefficient of kinetic friction (μ_k) between the shoe sole and the underfoot surface was constructed, and a method including criteria to evaluate the risk of slipping during walking was developed. The apparatus is a prototype stationary step simulator capable of simulating the movements of a human foot and the forces applied to the underfoot surface during an actual slip, and the drainage capability of the contact surface between the shoe sole and the flooring when different lubricants or contaminants are used.

The apparatus consists of a movable artificial foot controlled by a computer with the aid of three hydraulic cylinders. The frictional force (F_μ), the normal force (F_N) and their ratio (μ_k = F_μ/F_N) are measured with a two-way force platform when the foot slides along its surface. Two separate gait patterns, heel-slide (μ_k1) and sole-slide (μ_k2) gait pattern, are used for the evaluations. The method classifies studied shoe, lubricant and underfoot surface combinations into five slip resistance classes according to the measured μ_k1 The slip resistance assessments are specified with some complementary safety criteria, e.g., the ratio μ_k1/ μ_k2 The reliability of the developed measurement method was assessed in an international comparison test. According to available results discussed in this paper, our method seems to be valid and the slip resistance measurements seem to be repeatable.     

Evaluation of Adsorption Characteristics of Malachite Green onto Almond Shell (Prunus dulcis)

The potential usage of almond shell (P. dulcis), which is an agricultural waste product, in the removal of malachite green from aqueous solutions was evaluated with respect to various experimental parameters including contact time, initial malachite green concentration, temperature, adsorbent concentration, etc. The adsorption kinetics of malachite green fitted well the pseudo-second-order kinetic model. The monolayer adsorption capacity of almond shell was found to be 29.0 mg g^?1. The adsorption of malachite green onto almond shell increased with raising the temperature. From the experimental results, almond shell could be employed as a low cost and easily available adsorbent for removal of malachite green in wastewater treatment process.     

A new kinetic model for Ni(II) ion flotation based on gene expression programming

ABSTRACT

The Ni(II) ion flotation kinetics with sodium dodecylsulfate as collector was studied with the aim of developing new models to predict the flotation rate constant (k) of Ni(II) ions and water removal during the process of Ni(II) ion flotation. In this regard, the most influential parameters on Ni(II) ion flotation efficiency including the ratio of collector concentration on the Ni(II) ion concentration, impeller speed, activity coefficient, and pH were used to develop predictive models. The results show that the proposed gene expression programming models can be used to predict the flotation rate constant of Ni(II) ions and water removal.     

Design of Synchronous Drive Mechanism of Opposed-Piston Hydraulic-Output Engine

In order to improve the thermal power conversion capacity of the internal combustion engine,combined with existing opposed-piston two-stroke engine(OP2S) and hydraulic free piston engine (HFPE),the integral structure for a new type of opposed-piston hydraulic-output (OPHO) engine has been designed,an operating principle has been introduced,the composition of its synchronous drive mechanism has been carefully analyzed,and a mathematical model has been built.In addition,the kinematics models of both the mechanism and the conventional crank-link mechanism have been established by utilizing MATLAB,and the movement rules of the pivotal moving components have been obtained.According to the simulation results,the piston movement of this new type of opposed-piston hydraulic-output engine reveals a prominent asymmetry compared to the conventional crank-link engine.Under a fixed engine revolving speed,the compression time of the opposedpiston hydraulic-output engine is shortened while the expanding time is lengthened,thus the gas turbulence intensity is strengthened around the top dead center (TDC) position.Meanwhile,the piston obtains a longer isometric process compared to conventional engines,which could be benefitial to enhance the combustion efficiency.     

CO2 gasification characteristics of nascent pyrolyzed particles from coals and oil shale

In this work, the co‐pyrolysis characteristics of oil shale with two typical coals, bitumite and lignite, and the co‐gasification characteristics of the mixture pyrolyzed fuels were studied via thermo‐gravimetric analysis. The individual fuels and mixture fuels were first pyrolysis in N₂ atmosphere to specified temperature (450, 550, and 620 °C) at the heating rate of 20, 30 and 40 °C/min, respectively, and then maintained at the given temperature for 20 min before converted to CO₂ ambient to conduct the CO₂ gasification tests. The kinetic behavior and effects of both fuel types and pyrolysis temperature were investigated. The shoulder peak at around 550 °C observed in the derivative of weight loss derivative thermogravimetry analysis (DTG) curve during the pyrolysis of oil shale has confirmed the existence of specific reactions of oil shale at around 550 °C that leads to a sharp trough in the differential curves of co‐pyrolysis with coals and the unusual change in activation energies of gasification. In isothermal pyrolysis stage, oil shale lost its vast majority of organic matters at the temperature lower than 550 °C. The escape of pyrolysis gas and liquids in the coals is much harder than that in oil shale. The interaction between oil shale and bitumite was too weak to discriminate both in the pyrolysis and CO₂ gasification process. The variation of the particle surface structure caused by the releasing of volatile gases is strongly affected by the reaction rate and temperature. Quick volatile decomposition and gas releasing lead to the increase of surface area, decrease of the average pore diameter as well as the uniformization of the pore structure, while the higher temperature results in the blockade and merging of fine pores. The two factors lead to the greatest mass loss rate in the pyrolyzed particles obtained at 550 °C in temperature programmed CO₂ gasification stage. Two model‐free methods, Friedman method and Flynn–Wall–Ozawa method, were used to extract kinetic parameters from the experimentally determined pyrolyzed fuel conversions. The volatile contend has a significant influence on the fixed carbon conversion during the partially pyrolyzed particles' CO₂ gasification. In this study, significant interactions existed in co‐thermal utilization, both pyrolysis and CO₂ gasification, of oil shale and lignite. It is therefore surmised that co‐gasification of pyrolyzed lignite and oil shale may represent a feasible, practical route to high‐efficiency utilization of these fuels. Copyright © 2017 John Wiley & Sons, Ltd.     

Weight loss of frozen bread dough under isothermal and fluctuating temperature storage conditions

Evaporative weight loss from food leads to both loss of saleable weight and quality deterioration so it need to be minimized. The effect of isothermal and fluctuating conditions on frozen dough weight loss was measured and compared with kinetic, physical and artificial neural network (ANN) models. Frozen dough samples were regularly weighed during storage for up to 112 days in loose-fitting plastic bags. The storage temperatures were in the range of −8 to −25 °C with fluctuations of ±0.1 °C (isothermal), ±1, ±3 or ±5 °C about the mean. For each combination of temperature and fluctuation amplitude, the rate of dough weight loss was constant. The rate of weight loss at constant temperature was nearly proportional to water vapour pressure consistent with standard theories for evaporative weight loss from packaged foods but was also accurately fitted by Arrhenius kinetics. Weight loss increased with amplitude of temperature fluctuations. The increase could not be fully explained by either the physic model based on water vapour pressure differences or the kinetic model alone. An ANN model with six neurons in the input layer, six neurons in hidden layers and one neuron in the output layer, achieved a good fit between experimental and predicted data for all trials. However, the ANN model may not be accurate for product, packaging and storage systems different to that studied.     

Catalytic combustion kinetics of isopropanol over novel porous microfibrous‐structured ZSM‐5 coating/PSSF catalyst

Porous thin‐sheet cobalt–copper–manganese mixed oxides modified microfibrous‐structured ZSM‐5 coating/PSSF catalysts were developed by the papermaking/sintering process, secondary growth process, and incipient wetness impregnating method. Paper‐like sintered stainless steel fibers (PSSF) support with sinter‐locked three‐dimensional networks was built by the papermaking/sintering process, and ZSM‐5 coatings were fabricated on the surface of stainless steel fibers by the secondary growth process. Catalytic combustion performances of isopropanol at different concentrations over the microfibrous‐structured Co–Cu–Mn (1:1:1)/ZSM‐5 coating/PSSF catalysts were measured to obtain kinetics data. The catalytic combustion kinetics was investigated using power–rate law model and Mars–Van Krevelen model. It was found that the Mars–Van Krevelen model provided fairly good fits to the kinetic data. The catalytic combustion reaction occurred by interaction between isopropanol molecule and oxygen‐rich centers of modified microfibrous‐structured ZSM‐5 coating/PSSF catalyst. The reaction activation energies for the reduction and oxidation steps are 60.3 and 57.19 kJ/mol, respectively. © 2014 American Institute of Chemical Engineers AIChE J, 61: 620–630, 2015     

A systematic methodology for kinetic modeling of chemical reactions applied to n‐hexane hydroisomerization

Kinetic modeling provides chemical engineers with a unique opportunity to better understand reaction kinetics in general and the underlying chemistry in particular. How to systematically approach a modeling assignment in chemical reaction kinetics is typically less clear, especially for novices in the field. The proposed modeling methodology pursues an adequate compromise between statistical significance and physical meaning of the kinetic model and the corresponding parameters and typically results in models of an appropriate complexity. It comprises the following activities: (1) data analysis, aiming at qualitative information on the reaction mechanism and corresponding rate equations, (2) model regression to quantify this information via optimal parameter values, and (3) validation of the statistical significance and physical meaning of the parameter estimates. This methodology is successfully applied to n‐hexane hydroisomerization on a bifunctional catalyst. © 2014 American Institute of Chemical Engineers AIChE J, 61: 880–892, 2015