Strengthening pelletization of manganese ore fines containing high combined water by high pressure roll grinding and optimized temperature elevation system

Pelletization is one of useful processes for the agglomeration of iron ore or concentrates. However, manganese ore fines are mainly agglomerated by sintering due to its high combined water which adversely affects the roasting performance of pellets. In this work, high pressure roll grinding(HPRG) process and optimization of temperature elevation system were investigated to improve the strength of fired manganese ore pellets. It is shown that the manganese ore possesses good ballability after being pretreated by HPRG twice, and good green balls were produced under the conditions of blending 2.0% bentonite in the feed, balling for 7 min at 16.00% moisture. High quality roasted pellets with the compressive strength of 2711 N per pellet were manufactured through preheating at 1050 °C for 10 min and firing at 1335 °C for 15 min by controlling the cracks formation. The fired manganese pellets keep the strength by the solid interconnection of recrystallized pyrolusite grains and the binding of manganite liquid phase which filled the pores and clearance among minerals. The product pellets contain high Mn grade and low impurities, and can be used to smelt ferromanganese, which provides a possible way to use imported manganese ore fines containing high combined water to produce high value ferromanganese.

Preparation of ZrB_2-SiC Powders via Carbothermal Reduction of Zircon and Prediction of Product Composition by Back-Propagation Artificial Neural Network

Phase pure ZrB_2-SiC composite powders were prepared after 1 450℃/3 h via carbothermal reduction route,by using ZrSiO_4,B_2O_3 and carbon as the raw materials.The influences of firing temperature as well as the type and amount of additive on the phase composition of final products were detailedly investigated.The results indicated that the onset formation temperature of ZrB_2-SiC was reduced to 1 400℃by the present conditions,and oxide additive(including CoSO_4·7H_2O,Y_2O_3 and TiO_2)was effective in enhancing the decomposition of raw ZrSiO_4,therefore accelerating the synthesis of ZrB_2-SiC.Moreover,microstructural observation showed that the as-prepared ZrB_2 and SiC respectively had well-defined hexagonal columnar and fibrous morphology.Furthermore,the methodology of back-propagation artificial neural networks(BP-ANNs)was adopted to establish a model for predicting the reaction extent(e g,the content of ZrB_2-SiC in final product)in terms of various processing conditions.The results predicted by the as-established BP-ANNs model matched well with that of testing experiment(with a mean square error in 10^(-3) degree),verifying good effectiveness of the proposed strategy.

Composition Optimization of Nb-Ti Microalloyed High Strength Steel

Four Nb-Ti microalloyed steels were refined and rolled to study the composition optimization of Nb-Ti microalloyed steels. The effects of Nb and Ti on the microstructures, precipitates and properties of Nb-Ti microalloyed steel were investigated. The results showed that an increase in Ti content resulted in the appearance of many fine precipitates leading to a strong precipitation strengthening effect. Hence, the yield strength increased. Besides, the increased strength by the combined increase of Nb and Ti was similar to that observed for the increase in Ti content alone. This increase in strength was attributed widely to the increase in the Ti content alone rather than Nb. Moreover, the increase in Nb content beyond 0.036 wt% exerted no significant effect on the strength of Ti-Nb microalloyed steels, in which more Ti could be added to further improve the strength of steels.

The Effects of Cooling Mode on the Properties of Ti–Nb Microalloyed High-strength Hot-rolled Steels

The industrial trials of two cooling modes, i e, water cooling in forepart + air cooling in later part (WAC) and air cooling in forepart + water cooling in later part (AWC), were carried out for a Ti- Nb microalloyed steel. The average cooling rates and coiling temperature were the same for two modes. The continuous cooling transformation (CCT) curve of the tested steel was drawn. The effects of the cooling mode on the microstructure, precipitates, and properties of the steels were investigated. Results show that the strength of the steel in the WAC mode is significantly larger than that in the AWC mode, mainly because the smaller the grain size, the more and finer the grain precipitates. Therefore, when the average cooling rate is constant, the fast cooling in the forepart is an effective method to increase the strength of steels. However, the increase in the strength is accompanied by the decrease in toughness, so that the toughness of the steel should be considered when changing the cooling mode.

Research and Application of Wear Resistant Refractories for Cooling Zone of Large Scale Coke Dry Quenching Ovens

In order to prolong the service life of the cooling zone of large scale coke dry quenching ovens,six kinds possible refractories for the cooling zone of large scale coke dry quenching ovens: SiC containing brick A,SiC containing brick B,mullite-andalusite brick,spinel containing brick,zirconia containing brick,corundum-mullite brick and grade B mullite brick,were analyzed in properties. It is found that the cooling zone lining adopting SiC containing bricks or mullite-andalusite bricks has much longer service life. Based on this,a new type of wear resistant brick was developed. The brick has a compressive strength of 135 MPa,a wear loss of 2. 10cm^3(only a quarter of that of the grade B mullite brick),and a higher bulk density than the grade B mullite brick. The application of the brick in a 140t·h^(-1)coke dry quenching oven showed that it performed better than the grade B mullite brick. The cooling zone adopting the new bricks has a lower coke discharging temperature,which is beneficial to the enhancement of heat recovery efficiency and steam power generation.

Treatment of Reused Comprehensive Wastewater in Iron and Steel Industry With Electrosorption Technology

Electrosorption technology was used to treat the reused comprehensive wastewater from iron and steel industry.A problem of relatively high conductivity of wastewater which greatly affects the reuse was examined,and industrial test was conducted for the reused water advanced deionization and purification in a comprehensive wastewater treatment plant of WISCO [Wuhan Iron and Steel(Group)Corporation].The results of the on-site industrial test showed a satisfactory treatment performance for the reused water even at a flow rate of 1000 L/h in a standard 500 L/h unit.The average conductivity decreased by about 70%,from 580-780 μS/cm to 100-350 μS/cm.The average removal efficiency of Cl-and Ca2+ was about 75% and 68%,respectively,and CODCr of the treated water was also reduced in some degree while the pH value was almost unchanged.The energy consumption was as low as 0.6 kWh/t,which was remarkably superior to the conventional technologies.Therefore,it is entirely feasible that the novel electrosorption technology can be used in enhanced desalination and purification treatment of reused comprehensive wastewater in iron and steel industry.

Effects of inclusions on microstructure and properties of heat-affected-zone for low-carbon steels

The characteristics of inclusions in two types of low-carbon steels by different deoxidization methods have been investigated by using the welding thermal simulation,the optical microscopy and scanning electron microscopy.In addition,the effects of inclusions on microstructure and properties of heat-affected-zone were studied.The nucleation and growth of intragranular acicular ferrite was observed in situ by the laser scanning confocal microscopy.The distribution of Mn element near the inclusion was also analyzed by the auger electron spectroscopy.The results showed that the inclusions in Al killed steel are mainly aluminum oxides,manganese sulfide and titanium nitrides,and that the inclusions in Ti killed steel are mainly titanium oxide,manganese sulfide complex inclusion and single manganese sulfide.The auger electron spectroscopy showed that there is an Mn-depleted zone near the interface of TiO x /MnS complex inclusion in the size of 1-3 m.It could be the effective nucleus of intragranular acicular ferrite which could divide the prior austenite grains,inhibit the growth of low-temperature microstruc-ture,and refine the final microstructure,so as to improve the toughness of heat-affected-zone significantly.

Optimization of Culture Components for Laccase Activity from Pleurotus Ostreatus P40 Using Response Surface Methodology

High enzymatic activity is required for laccase applications.Central composite design(CCD)-based response surface methodology(RSM)can effectively increase the enzymatic activity of Pleurotus ostreatus P40 in liquid substrate fermentation.Initial screening of the nutritional components was performed using a Plackett-Burman design.The variables,namely,bran,bagasse,Tween 80,and yeast extract,were found to have statistically significant effects on laccase activity.These variables were further optimized using CCD-based RSM.Optimal concentrations for the maximum laccase activity were 8.144 2 g/L bran,50 g/L bagasse,0.424 1 mL/L Tween 80,and 2.832 5 g/L yeast extract.Under optimized conditions,the maximum measured laccase activity reached 96 480 U/L,which was close to the predicted value(104 830 U/L)by RSM.Therefore,RSM can be used to optimize culture components for laccase activity from Pleurotus ostreatus P40.

Oily Wastewater Treatment by Porous Ceramics Mediums with Surface Lipophilic Modification

Aiming at the treatment of difficult-to-handle oily wastewater, the ceramics filter mediums made from the iron and steel plant sludge were adopted to surface lipophilic modification so as to remove oil efficiently. The hydrolysis technique by FTIR and conductivity test indicated that under acid conditions hydrogen silicon oil did not hydrolyze but release hydrogen by chemical reaction under alkaline conditions. The results of the experiments including contact angle measurement, FTIR analysis, and SEM analysis illustrate that a layer of lipophile coating indeed exists evenly on the surface of filter mediums after modification. Furthermore, the hydrogen-containing silicone oil was combined through dehydration of Si-H bond with the-OH on the surface of ceramic filter medium.

Influence of Nb Content on Microstructure and Mechanical Properties of a 7%Ni Steel

The influence of Nb content on the microstructure and cryogenic mechanical properties of a 7%Ni steel was investigated within the Nb content range from 0 to 0.05%.The microstructure was characterized by optical microscope,scanning electron microscope,transmission electron microscopy and X-ray diffraction,and the low-temperature mechanical property tests were conducted.The Nb addition can effectively refine the prior austenite grains and microstructure of the steel.Fine niobium precipitates with a diameter of about 10–50 nm were observed.They tend to be spherical and locate mainly in the vicinity of grain boundaries.Although there are considerable amounts of reversed austenite forming at grain boundaries in the specimen containing the highest Nb content,no Nb element was detected in such reversed austenite,which implies that Nb element did not affect the formation of the reversed austenite directly.Mechanical test results suggest that the strength of the 7%Ni steel is not simply in relation to the prior austenite grain size,but also depends on the amount of reversed austenite.On the other hand,the grain refinement,enhanced with increasing Nb content,has a good effect on cryogenic toughness.

Effect of Mn Content on Microstructure and Cryogenic Mechanical Properties of a 7%Ni Steel

The effect of Mn content on the microstructure and cryogenic mechanical properties of a 7% Ni steel was investigated within the Mn content range from 0.13% to 0.36%. The microstructure of the steel as determined by optical microscopy,scanning electron microscopy, transmission electron microscopy, electron backscattering diffraction and X-ray diffraction was presented, and the low-temperature mechanical properties were given. The size of prior austenite grain did not change a lot as Mn content increased. Film-like reversed austenite, having high stability, was found mainly in the specimens with lower Mn content; however, in the specimen with the highest Mn content, the role of Mn was not obvious in stabilizing reversed austenite. Besides, with increasing Mn content, the amount of reversed austenite at grain boundaries gradually decreased. The variable Mn content had a significant effect on cryogenic toughness, but not apparent on cryogenic tensile strength or yield strength. An excellent combination of cryogenic tensile and impact properties was obtained when Mn content of steel was 0.13%.

Simple lattice Boltzmann approach for turbulent buoyant flow simulation

In the present work,a simple large eddy simulation(LES)-based lattice Boltzmann model(LBM)is developed for thermal turbulence research.This model is validated by some benchmark tests.The numerical results demonstrate the good performance of the present model for turbulent buoyant flow simulation.

Downregulation effects of beta-elemene on the levels of plasma endotoxin,serum TNF-alpha,and hepatic CD14 expression in rats with liver fibrosis

It has been demonstrated thatβ-elemene could protect against carbon tetrachloride(CCl_(4))-induced liver fibrosis in our laboratory work,and the aim of this paper is to reveal the protective mechanisms ofβ-elemene.The hepatic fibrosis experimental model was induced by the hypodermical injection of CCl_(4) in Wistar male rats.β-elemene was intraperitoneally administered into rats for 8 weeks(0.1 mL/100 g bodyweight per day),and plasma endotoxin content was assayed by biochemistry.The serum TNF-αlevel was detected using radioactive immunity.CD14 expression in rat livers was measured by immunohistochemistry and Western blot.The results showed thatβ-elemene can downregulate the levels of plasma endotoxins,serum TNF-α,and hepatic CD14 expression in rats with liver fibrosis.β-elemene plays an important role in downregulating the lipopolysaccharide signal transduction pathway,a significant pathway in hepatic fibrosis development.

Formation of Inclusion in Ti–Al Killed Low C–Mn Steel

The formation of inclusion in Ti–Al complex deoxidized C–Mn steel was investigated. When Al content in steel is very low([Al]=0.0005%), for 0.003%<[Ti]<0.007%, the inclusion is the Al2O3–SiO2–MnO–TiOx composite inclusion; for [Ti]≥0.009%, the inclusion is TiOx in the steel. When [Ti]=0.005%, [Al]<0.001%, the inclusion is the Al2O3–SiO2–MnO–TiOx composite inclusion; while [Al]>0.006%, inclusions would be pure Al2O3. The experimental results agree with the thermodynamics conclusions.

Swelling Behaviors and Pervaporation Properties of CA/PAN Composite Membranes for Separation of Caprolactam/Water Mixtures

The composite membranes with cellulose acetate(CA) as the separating layer material and polyacrylonitrile(PAN) as the supporting layer material were prepared for separating caprolactam(CPL) from CPL/water mixtures by pervaporation technique.The swelling experiments were carried out to investigate the effects of swelling time and CPL concentration on the degree of swelling.The results showed that the CA membrane reached swelling equilibrium within 24 h,and the degree of swelling first slightly decreased then increased with the increase of CPL concentration in the feed under the experimental conditions.Respectively comparing flux with permeance,and separation factor with selectivity,we found out that the separation performance of the CA/PAN composite membrane is more strongly dependent on its hydrophilic/hydrophobic nature as well as on the effects of operating parameters,such as feed composition concentration and feed temperature.

Reliability design optimization of composite structures based on PSO together with FEA

The present work aims to develop a method for reliability-based optimum design of composite structures. A procedure combining particle swarm optimization (PSO) and finite element analysis (FEA) has been proposed. Numerical examples for the reliability design optimization (RDO) of a laminate and a composite cylindrical shell are worked out to demonstrate the effectiveness of the method. Then a design for composite pressure vessels is studied. The advantages and necessity of RDO over the conventional equi-strength design are addressed. Examples show that the proposed method has good stability and is efficient in dealing with the probabilistic optimal design of composite structures. It may serve as an effective tool to optimize other complicated structures with uncertainties.

New Integrated Processes for Treating Cold-Rolling Mill Emulsion Wastewater

Two new integrated processes, gas-energy-management (GEM)—electrochemical catalytic oxidation (ECO)—membrane bioreactor (MBR) and ultrafiltration (UF)—ECO—MBR, in industrial-scale test for treating cold-rolling mill emulsion wastewater with water quantity of 200 L/h to 3000 L/h were studied. The former was put forward firstly and the latter was applied initially in this field. The operation conditions and mechanisms of each module in the integrated processes were analyzed and the influences of operational parameters of two processes on chemical oxygen demand (CODCr) removal efficiency were comparatively investigated. The test results showed that the ultimate water quality from the two processes after treatment could meet the requirement for reuse.However, the quality of effluent treated by GEM—ECO—MBR was more stable than that of UF—ECO—MBR.

N_2O decomposition over K/Na-promoted Mg/Zn–Ce–cobalt mixed oxides catalysts

Three groups of cobalt mixed oxide catalysts(Mg/Zn–Co, Mg/Zn–Ce–C, K/Na–Mg/Zn–Ce–Co)were prepared by sol–gel or impregnation methods. The synergistic effects of transition metal, rare earth metal and alkali metal on cobalt mixed catalysts for nitrous oxide(N2O)decomposing to N2 and O2were investigated. The experimental results revealed that the catalytic activity for N2 O decomposition was promoted as Co2+was replaced partially by Zn2+/Mg2+, moreover, the characterization analysis by XRD and XPS showed that Zn2+/Mg2+replaced Co2+successfully into the spinel structure of Co3O4 and promoted significantly the catalytic activity. Especially, the addition of CeO2 and K2O/Na2O decreased the binding energy and resulted in an increase in the density of the electron cloud around Co and an improvement of the catalytic activity. Of the investigated cobalt mixed catalysts, the best catalytic activity was shown by 2% K–Zn0.5–Ce0.05–Co catalyst.