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Changsha, China

Wang X.,Central South University | Wang X.,Changsha Syno Therm Co. | Chen B.,Central South University | Xiao W.,Shanghai China Electrical Green Technology Group | Peng H.,Changsha Syno Therm Co.
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2010

Vanadium nitride was synthesized by the microwave heating process with V2O5 (or ammonium metavanadate) as starting materials and carbon black as reductant in N2 atmosphere. The effects of the ratio of the carbon black to V2O5, nitridation temperature, nitridation time, N2 flux and the mixture pressure on the nitrogen content of the product were investigated when the reduction time was 60 min and the highest reduction temperature 933 K. Results show that the product of vanadium nitride has 12.6% nitrogen, 79.2% vanadium and 4.6% carbon and its density is 4.5 g/cm3, when the mixture pressure is 20 MPa, the ratio of carbon to V2O5 35%, nitridation time 120 min, nitridation temperature 1723 K and N2 flux 2 L/min. XRD patterns detect the product is pure vanadium nitride. Compared with the conventional resistance furnace heating method, the microwave heating process can shorten the time of reaction and cooling, save the energy, simplify the process and reduce the cost. Copyright © 2010, Northwest Institute for Nonferrous Metal Research. Pubished by Elsevier BV. All right reserved.

Yi L.-Y.,Central South University | Huang Z.-C.,Central South University | Peng H.,Changsha Syno Therm Co. | Jiang T.,Central South University
Advanced Materials Research | Year: 2011

In this paper, the direct reduction of iron ore pellets was carried out by simulating the typical gas composition in coal gasification process, Midrex and Hyl III process, the influence of gas composition and temperature on reduction was studied. Results show that the proportion of H2 increasing is helpful to improve the reduction rate, while when H2/CO>1.6, changes of H2 content will have very little influence on it. Appropriate reduction temperature is about 950°C, higher temperature(1000°C) may unfavorably slowed the reduction rate. From the kinetics analysis at 950°C and 1000°C, when H2/CO=0.4 the prophase of reduction course (∼90%) is likely controlled by interfacial chemical reaction mechanism and in the later controlled by gaseous diffusion mechanisms. However, when H2/CO>0.4 the whole reduction course is likely controlled by interfacial chemical reaction mechanism. The reaction rate constant (k) and effective diffusion coefficient (De) at 950°C are both better than those at 1000°C. Research also shows that the coal-water slurry gasification based on Texaco furnace is more suitable for iron ore direct reduction than other coal gasification processes. © (2011) Trans Tech Publications, Switzerland.

Huang Z.-C.,Central South University | Wu K.,Central South University | Hu B.,Central South University | Peng H.,Changsha Syno Therm Co. | Jiang T.,Central South University
Journal of Iron and Steel Research International | Year: 2012

The microwave heating characteristics of the mixture with oxidized pellet and coal was studied, and the non-isothermal reduction dynamics is discussed. The results show that, the slow-heating stage of the temperature rising process can be segmented into two heating temperature curves approximately that have good linear relationship. They can be seen as temperature programming. In the first stage, between 827 and 1073 K, the reaction mechanism obeys diffusion controlled model. In the second stage, between 1093 and 1323 K, the reaction mechanism also obeys diffusion controlled model. The apparent activation energies are found to be 75.13 kJ/mol for the first stage and 53.17 kJ/mol for the second stage. That is lower than the apparent activation energy under conventional heating. The microstructure of the reduced pellets shows that microwave can improve the kinetics of the reduction. Microwave has anxo-action to the reaction obviously. © 2012 Central Iron and Steel Research Institute.

Hu B.,Central South University | Huang Z.-C.,Central South University | Jiang T.,Central South University | Peng H.,Changsha Syno Therm Co.
Kang T'ieh/Iron and Steel (Peking) | Year: 2012

Traditional heating for direct reduction had a low thermal efficiency and "cold center", even the large amount of waste heat and gas emissions, which made the long time, high energy consumption and heavy pollution for reduction of oxidized pellets. The major advantages of using microwaves in the experiment were rapid heat transfer, volumetric and selective heating and pollution-free environment, in addition, iron concentrate oxidized pellets and anthracite had a strong microwave absorbency, on the basis, a new coal based direct reduction technology on iron concentrate oxidized pellets was developed in microwave shaft furnace. The results show that iron concentrate oxidized pellets coal based direct reduction by microwave heating in 1050°C at 65min, can obtain 95.25% the metallization rate, and has 1718.88 N/a compressive strength. Compared with conventional heating, the time of microwave heating reduction roasting can shorten 27.78%, and compressive strength nearly doubled increase, even has little waste heat and gas emission.

Chen Y.,Changzhou University | Zhu Y.,Changzhou University | Zhu Y.,Changsha Syno Therm Co. | Peng H.,Changzhou University | And 3 more authors.
Surface and Coatings Technology | Year: 2014

Zn/Fe and Zn/Fe-P liquid-solid diffusion couples were annealed at 450. °C to investigate the effect of phosphorus in steel on the growth kinetics of Fe-Zn intermetallic compounds in diffusion zone. The results show that phosphorus in steel can delay or suppress the growth of G{cyrillic};; phase and promote the growth of ⊗; phase. The higher the content of phosphorus in steel is, the faster the growth of the ⊗; phase is. The growth kinetics of the total layer of Fe-Zn intermediate phases in Zn/Fe-0.123. wt.%P diffusion couple is the same as that in Zn/Fe diffusion couple. But the growth behavior of Fe-Zn intermediate phases in Zn/Fe-0.340. wt.%P diffusion couple differs remarkably from that in Zn/Fe diffusion couple. The diffusion path model is introduced to explain this phenomenon. © 2013 Elsevier B.V.

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