烧结机尾单辊破碎机部件结构的改进

1 前言我厂24m^2星轮摆架式烧结机的机尾单辊破碎机原设计的保护帽是安装在篦板上,由两端卡板压住。由于锤头咬住大块热烧结矿向下旋转,在重负荷、高温条件作用下,锤头和保护帽的磨损严重。

Reaction mechanisms of low-grade molybdenum concentrate during calcification roasting process

The effects of Ca-based additives on roasting properties of low-grade molybdenum concentrate were studied. The resultsshow that calcium-based additives can react with molybdenum concentrate to form CaSO4 and CaMoO4. The initial oxidationtemperature of MoS2 is 450℃, while the formation of CaMoO4 and CaSO4 occurs above 500℃. The whole calcification reactionsare nearly completed between 600 and 650℃. However, raising the temperature further helps for the formation of CaMoO4 but isdisadvantageous to sulfur fixing rate and molybdenum retention rate. Calcification efficiency of Ca-based additives follows theorder： Ca（OH）2〉CaO〉CaCO3. With increasing the dosage of Ca（OH）2, the molybdenum retention rate and sulfur-fixing rate rise, butexcessive dosages would consume more acid during leaching process. The appropriate mass ratio of Ca（OH）2 to molybdenumconcentrate is 1：1. When roasted at 650 ℃ for 90 min, the molybdenum retention rate and the sulfur-fixing rate of low-grademolybdenum concentrate reach 100% and 92.92%, respectively, and the dissolution rate of molybdenum achieves 99.12% withcalcines being leached by sulphuric acid.

篦板体耐磨耐热堆焊焊条的研制与应用

针对篦板体的工况条件,研制了DL-2型耐磨耐热堆焊焊条,并对该焊条堆焊合金的耐磨性、高温性能和工艺性能进行了检测与分析。实际生产应用表明:该焊条的各项性能指标达到设计要求。

Mineralogical characterization and leaching behavior of Nigerian ilmenite ore

The characterization and H2SO4 leaching behavior of a Nigerian ilmenite ore following mechanical activation and alkali roasting were investigated. The effects of NaOH/ore ratio, H2SO4 concentration, leaching and roasting temperature on the Ti recovery from the milled ore were examined. The results show that mechanical activation significantly enhances the dissolution of ilmenite ore. Under the leaching conditions of 90 °C, 60% （v/v） H2SO4 and 4 h, about 72% Ti extraction was obtained from a milled ore roasted at 850 °C with 60% NaOH. X-ray diffraction （XRD） phase analysis of the roasted mass, water treated residue and leach residue supports the reaction mechanism and experimental results.

Features and mechanisms of self-sintering of molybdenite during oxidative roasting

Roasting experiments were carried out with pure reagents as raw materials.The self-sintering behaviors of molybdenite(MoS_(2))during oxidation were investigated by thermodynamic calculation,XRD,SEM-EDS and high-temperature in situ analysis.The results indicate that the desulfurization efficiency of MoS_(2) pellet decreases with the increase of roasting temperature from 600 to 700℃,owing to the expansion of sintered area.At the very beginning of roasting,sintered layer can be rapidly formed and cover the pellet surface on the windward side,and meanwhile,MoO_(2)and Mo_(4)O_(11) intensively appear and constitute the sintered layer together with MoO_(3).Moreover,it is proven that MoO_(3)-rich products containing low-valence molybdenum oxides have low melting points,thus easy to be melted during the occurrence of exothermic reaction between MoS_(2) and O_(2),which leads to the sintering of materials.

Vanadium recovery from Na_(2)SO_(4)-added V-Ti magnetite concentrate via grate-kiln process

Pilot experiments on Na;SO;-roasting of V-Ti magnetite(VTM) concentrate pellets were performed to activate vanadium with simulated grate-kiln machines. Combined with thermodynamic calculation, X-ray diffraction(XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy(SEM-EDS), and inductively coupled plasma-atomic emission spectrometry(ICP-AES) analyses, process parameters of pellet making were optimized, and the enhancement of vanadium oxidation and conversion was realized. The results show that, in balling stage, adding Na;SO;can promote the thermal decrepitation resistance of green pellets;in the drying stage, higher wind temperature can improve the dispersion of sodium salt in pellets;in preheating stage, using O;-rich hot gas can promote more thorough oxidation of vanadium;in roasting stage, the effect of vanadium conversion to sodium vanadate is better when the liquid amount is 15.5%-22.5%. Based on the above measures, the vanadium conversion rate achieved in the roasted pellets is 85.6%, proving the feasibility of vanadium recovery using an existing pellet production line.

Rod-like Bi_(4)O_(5)I_(2)/Bi_(4)O_(5)Br_(2) step-scheme heterostructure with oxygen vacancies synthesized by calcining the solid solution containing organic group

To improve separation efficiency of the photogenerated electron-hole pairs,constructing a heterojunction is considered to be a promising strategy.However,the fabrication of heterojunction via a facile route to achieve a substantial improvement in photocatalytic performance is still challenging.In this work,a well-designed nanosheet-based rodlike step-scheme(S-scheme)heterojunction Bi_(4)O_(5)I_(2)/Bi_(4)O_(5)Br_(2) with rich oxygen vacancies(OVs)(Bi_(4)O_(5)I_(2)/Bi_(4)O_(5)Br_(2)-OV)was easily synthesized by calcining BiOAc0.6Br0.2I0.2(Ac-=CH3 COO-)precursor.The as-prepared Bi4O5I2/Bi4O5Br2-OV exhibited excellent visible light photocatalytic performance towards antibiotic tetracycline(TC)and dye rhodamine B(Rh B)degradation and removal rate reached 90.2% and 97.0%within 120 min,respectively,which was higher than those of Bi4O5I2-OV(56.8% and 71.8%),Bi4O5Br2-OV(47.4%and 68.4%),solid solution BiOAc0.6Br0.2I0.2(67.0% and 84.0%)and Bi_(4)O_(5)I_(2)/Bi_(4)O_(5)Br_(2) with poor oxygen vacancies(Bi4O5I2/Bi4O5Br2-P)(30.6%and 40.4%).Owing to the release of heat and generation of reducing carbon during calcining the precursor with Ac-,it could not only reduce the generation temperature of Bi-rich bismuth oxyhalides,which thus decreased particle size and increased surface areas,but also introduce surface OVs,which could trap photoelectrons and inhibit the recombination of carriers.In addition,the calcination of single solid solution precursor benefited to the formation of well-alloyed interfaces with larger contact areas between 2D/2D nanosheet-like materials,which facilitates charge carriers transfer at the interfaces.The Bi4O5I2/Bi4O5Br2-OV also shows the desirable removal rate for TC and Rh B in actual wastewater or in the presence of some electrolytes.This study provides an effective and simple strategy for designing OVs modified Bi-rich oxyhalides heterojunctions.

Reaction mechanism of roasting Zn_2SiO_4 using NaOH

The reaction kinetics of roasting zinc silicate using NaOH was investigated.The orthogonal test was employed to optimize the reaction conditions and the optimized reaction conditions were as follows:molar ratio of NaOH to Zn2SiO4 of 16:1,reaction temperature of 550°C,and reaction time of 2.5 h.In order to ascertain the phases transformation and reaction processes of zinc oxide and silica,the XRD phase analysis was used to analyze the phases of these specimens roasted at different temperatures.The final phases of the specimen roasted at 600°C were Na2ZnO2,Na4SiO4,Na2ZnSiO4 and NaOH.The reaction kinetic equation of roasting was determined by the shrinking unreacted core model.Aiming to investigate the reaction mechanism,two control models of reaction rate were applied:chemical reaction at the particle surface and diffusion through the product layer.The results indicated that the diffusion through the product layer model described the reaction process well.The apparent activation energy of the roasting was 19.77 kJ/mol.

Digestion mechanism and crystal simulation of roasted low-grade high-sulfur bauxite

Low-grade high-sulfur bauxite was pretreated via suspension roasting and muffle furnace roasting to remove sulfur and enhance digestion properties.The results show that sulfur can be efficiently removed,and the alumina digestion properties are significantly improved after suspension roasting.Under optimal conditions(t=70 min,T=280°C,w(CaO)=8%and Nk=245 g/L),the digestion ratios are 94.45%and 92.08%for the suspension-roasted and muffle-roasted ore,respectively,and the apparent activation energies are 63.26 and 64.24 kJ/mol,respectively.Two crystal models were established by Materials Studio based on the XRD patterns.The DFT simulation shows that the existing Al—O bands after suspension roasting can improve alumina digestion.The(104)and(113)planes of Al2O3 after suspension roasting are found to combine with NaOH more easily than those of Al2O3 treated in a muffle furnace.

A novel method to produce potassium chromate from carbon ferrochrome

The oxidizing roasting of carbon ferrochrome in the presence of potassium carbonate and air was investigated. The effects of reaction temperature, reaction time, ratio of alkali-to-ore were studied, together with a discussion of the thermodynamics and macro kinetics. It is observed that the reaction temperature and reaction time have significant influence on the roasting reaction. The reaction mechanism changes greatly as the temperature varies. A two-stage roasting process is favorable for the roasting reaction, and a recovery ratio of 96.51% is obtained through this two-stage roasting method. The chromium residue yielded from this method is quite little, only one third of the product. Moreover, the component of Fe in the residue is as high as 54.28%. Therefore, it can be easily recovered to produce sponge iron, realizing zero-emission of chromium residue.

Desulfurization of Petroleum Coke by Calcination in Ammonia Atmosphere below 1000℃

The desulfurization efficiency and mechanism of the calcination of petroleum coke in ammonia atmosphere at lower than 1000 ℃ were investigated through a series of conditional experiments and comparison with other gases such as H_2. The topics of efficiency and reaction mechanism are usually discussed through investigation by means of the Fourier transform infrared spectroscopy(FT-IR), the Brunauer-Emmett-Teller(BET) technique, and the thermogravimetry coupled with the mass spectrometry(TG-MS). Results showed that in addition to H_2, ammonia not only could retain a high desulfurization rate but could also reduce coke loss during the desulfurization process of petroleum coke. The best desulfurization conditions covered a petroleum coke particle size of less than 0.1 mm, a calcination temperature of 800 ℃ in ammonia atmosphere with a flow rate of 10 L/h, and a heating duration of more than 120 min. Ammonia decomposition, H_2 generation, decline in the activation energy of the carbon–sulfur bonds, and petroleum coke with a largest specific surface area at 800 ℃ are the key goals of desulfurization studied thereby. As proved by TG-MS analysis, given a large quantity of H_2, ammonia can be decomposed at the same temperature to completely come into contact with the sulfur species in petroleum coke to generate H_2S.

Swelling behavior of hot preheated pellets in reduction roasting process

One kind of facile coal-based direct reduction process is using hot preheated pellets for reduction in grate kiln. In this work, effects of reduction parameters on swelling index of hot preheated pellets were investigated by photographic technique under isothermal conditions. Experimental results show that swelling index of pellets is firstly increased then gradually decreased with increasing reduction time, while that is found to be an obvious decrease from 175 % to 30% with the variation of temperature from 900℃ to 1100℃. Results of XRD combined with SEM reveal that swelling behavior of pellets is decided by structure of newly formed metal iron grains. The formation and growth of fibers iron grains promote the increase in volume. Low temperature and low CO content are favored to the formation and orientated growth of metal iron grains in the one step process.