Tungsten powder was prepared from yellow tungsten oxide by stepwise reduction.The effects of hydrogen flow rate and system inlet-to-outlet gas flow rate ratio on the properties and compact strength of tungsten powder were systematically studied.The results show that with the increase of hydrogen flow rate,the particle size of tungsten powder is refined,but the change of its compact strength is small.When the hydrogen flow rate is 250 L/min,the particle size of tungsten powder is 3.30μm,and the compact strength is 4.1 MPa.When the hydrogen flow rate increases to 800 L/min,the particle size of tungsten powder is 2.72μm,and the compact strength is 4.2 MPa.At the same time,the system inlet-to-outlet gas flow rate ratio significantly affects the compact strength of tungsten powder.When the system inlet-to-outlet gas flow rate ratio is 1∶1,the particle size of tungsten powder is 2.76μm and the compact strength is 1.6 MPa.When the system inlet-to-outlet gas flow rate ratio is increased to 1∶0.9,the particle size of tungsten powder rises to 3.06μm and the compact strength is increased to 4.4 MPa.

Ultra-coarse grained cemented carbides have attracted much attention because of its unique microstructure characteristics in the field of cemented carbide,showing good impact resistance,wear resistance,thermal fatigue resistance,and other advantages,and have great development potential in rock drilling,stamping die,and hot rolling.This paper summarizes the characteristics and the toughening mechanism of the ultra-coarse grained cemented carbides,and introduces the current preparation of coarse-grained WC raw powders and ultra-coarse grained cemented carbides,as well as the exploration situation of the strengthening method of the ultra-coarse grained cemented carbides.Finally,some thoughts about the development trend of the ultra-coarse grained cemented carbides are put forward.

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By using the method of bisulfate and tungsten ore roasting,arsenic in tungsten ore could be converted into volatile arsenide and absorbed by the alkaline solution,fundamentally changing the easy-dispersion trend of arsenic in the tungsten smelting system and greatly reducing the formation of the arsenic-containing hazardous waste in tungsten smelting.Simultaneously,the tungsten ore is roasted into MnSO₄,Fe₂(SO₄)3+WO₃or CaSO₄+WO₃products,and the next step is to separate tungsten and impurities in the roasted products effectively to obtain relatively pure tungsten compounds.In general,MnSO₄and Fe₂(SO₄)3could be effectively dissolved by cheap sulfuric acid,but whether CaSO₄and WO₃could be dissolved in the same way is unknown.Based on this,the dissolution behavior of CaSO₄-WO₃system in sulfuric acid was systematically studied in this paper.The results show that in the sulfuric acid system,the solubility of CaSO₄is significantly greater than that of WO₃,and their solubility difference varies little with the concentration of sulfuric acid but greatly with temperature.The effective separation of CaSO₄and WO₃can be achieved by controlling certain acidity and temperature.

A method of removing magnesium from mother liquor in the production of water-washed ammonium dimolybdate is proposed,meaning that the magnesium content is reduced by adding ammonium phosphate to the mother liquor to form magnesium ammonium phosphate precipitation.In the experiment,by optimizing the process parameters such as the concentration of Mg²⁺and PO₄^3-in mother liquor,reaction temperature,solution pH and reaction time,the content of magnesium and phosphorus in ammonium dimolybdate products reached the standard.And the method has been successfully applied to the production practice.The study provides an innovative magnesium removal process with simple operation and no impact on the production line for the water-washed ammonium dimolybdate production line.

The molybdenum content in some molybdenum ore in Fujian is only 0.09%,and most molybdenum exists in molybdenites while a small amount of molybdenum exists in the form of molybdenum oxide ore.The gangue minerals mainly consist of easy-sliming silicate minerals and the flotation activity of the molybdenum ore is low,showing that it is the typical refractory molybdenum ore with high mud content and low grade.A novel surface promoter MCS was introduced to effectively enhance the surface activity of the molybdenum ore,thereby improving the molybdenum flotation recovery.The appropriate grinding fineness,MCS dosage,water glass dosage and collector CM dosage for the flotation were determined through condition experiments.The results show that by using the flotation machine,molybdenum concentrates with a Mo grade of 45.75%and Mo recovery of 82.18%can be obtained after one roughing,three scavenging and seven cleaning,but this process is lengthy and the production and operation costs are high.Through the combined flotation column-flotation machine process,the qualified molybdenum concentrates are gained with a Mo grade of 46.01%and Mo recovery of 87.81%after four cleaning.Therefore,it is re-commended as the principle process for the recovery of molybdenum from the molybdenum ore.

The direct saponification of rare earth extraction organic phase with calcium hydroxide powder was studied.The experimental results show that the saponification values of P507 organic phase and naphthenic acid organic phase are 0.55 mol/L and 0.72 mol/L,respectively, with clear appearance and good fluidity through the process of direct saponification by using calcium hydroxide powder.When the calcium saponified organic phase is subject to extraction reaction with rare earth chloride feed liquid, the separation time of P507 organic phase is 40 s with the rare earth load of 0.19 mol/L,and the separation time of naphthenic acid organic phase is 180 s with the rare earth load of 0.19 mol/L.Based on the test data, a centra-lized calcium hydroxide powder direct saponification technology was developed.After years of industrial operation, the results show that calcium hydroxide powder directly saponifies the P507 organic phase and the naphthenic acid organic phase with good fluidity, fast phase separation, little impact on product quality, and no long-term adverse effects on the organic phase.And the saponification cost is only 16.5% of that of liquid alkali.Since the saponifier is a powder, there is no need for emulsion and the saponification reaction with the organic phase directly occurs.Compared with the saponification of liquid alkali, the wastewater greatly reduces and the environmental benefits are quite good.

China is rich in vanadium resources.Vanadium metal is widely used in steel, national defense, aviation and other fields because of its excellent performance.At present, vanadium metal is mainly prepared by metallothermic reduction, followed by refining to obtain high-purity vanadium metal.In this paper, several typical methods of the preparation and refining of crude vanadium are analyzed and summarized, and it is pointed out that the development direction of vanadium preparation is high yield, low cost, low energy consumption, and short process in the future.

Accelerating the extraction of germanium resource from coal fly ash can not only alleviate the contradiction between the shortage of germanium resource and its increasing demand but also broaden the ways of high-value utilization of coal fly ash and improve the added value of products.By reviewing the development status of germanium enrichment and recovery technology from coal fly ash in recent years,the merits and demerits of various methods are analyzed and relevant suggestions are given on the efficient utilization of germanium in coal fly ash.