Changsha Syno Therm Co.

Changsha, China

Changsha Syno Therm Co.

Changsha, China
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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 Ltd. | 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 SYNOTHERM 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.


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.


Hu B.,Central South University | Huang Z.-C.,Central South University | Jiang T.,Central South University | Peng H.,Changsha Syno Therm Co.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2011

The structure change and temperature rising behavior of oxidized pellet by microwave heating under the condition of nitrogen protection were studied. The result shows that oxidized pellet's microwave heating process can be divided into three stages: slow heating, fast heating and slower heating. The change of the electromagnetic properties of pellets which makes the pellet have different rate of temperature rising in microwave field is caused by temperature and structure change. The cold pellets at different end point temperatures by microwave heating have a large change in the internal structure but a little change about electromagnetic properties after ground granulated and then briquetting. The strength and porosity of oxidized pellet increase firstly and decrease afterwards in the whole process of microwave heating. The observation of scanning electron microscopy shows that, there appear cracks and breakdown in particles at first, and then the particles were recrystallize with rising temperature in microwave filed. All of these make the structure of pellets change.


Huang Z.-C.,Central South University | Yi L.-Y.,Central South University | Peng H.,Changsha Syno Therm Co. | Jiang T.,Central South University
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2012

Effects of roast temperature on the properties of oxide pellets, such as compressive strength, porosity, Fe 3O 4 content and microstructure, were studied. And the effects of roast temperature on the gas-based direct reduction course were also researched. The results show that compressive strength of the pellets increases with the increase of roast temperature, however, the porosity and Fe 3O 4 content decrease obviously. The reduction rate of pellets roasted at 1200°C is faster, than that roasted at 1150°C and 1250°C, and the reduction rate of pellets roasted at 1100°C is the slowest of all samples. From the kinetics analysis, the whole reduction processes of pellets roasted at 1100, 1150 and 1200°C are controlled by interfacial chemical reaction mechanism. But for the pellets roasted at 1250°C, the prophase and anaphase are determined by interfacial chemical reaction mechanism and gaseous diffusion mechanism, respectively.


Hu B.,Central South University | Huang Z.-C.,Central South University | Wu K.,Central South University | Lv L.-L.,Central South University | Peng H.,Changsha SYNO THERM Co.
TMS Annual Meeting | Year: 2010

It is difficult to obtain ideal indexes of limonite ore by traditional physical processes. In this investigation, the limonite with TFe of 48.92% is studied. The experimental results show the conventional heating requires a long reduction time, easily leads to cold center and over reduction, and even forms fayalite. Magnetic roasting-separation of limonite by microwave heating under the conditions of output power l.Okw at 35min achieves the concentrate of iron content 61.15% and recovery of 88.35% while the concentrate of iron content 60.55% and recovery of 74.06% is obtained under the optimal conditions for 60min at 800→ following conventional heating. The whole pellet is heated simultaneously, which gives priority to heat coal particles and iron minerals, and accelerates the transformation of limonite into magnetite. Meanwhile, gangue minerals remain lower temperature due to their weak microwave absorbing capacity, and thus it greatly restrains the formation of fayalite. Limonite, a typical low-grade iron ore, has characteristics of low grade (37%∼55%), complex components and difficult for beneficiation [1, 2]. Liu Wei-qiang had obtained concentrate grade 51.38%Fe and 55.07%Fe employed respectively by low and high intensity magnetic separation and gravitation-flocculation followed high intensity magnetic separation on a limonite in Yunnan [3]. Huang Wan-fu had also achieved the grade of iron concentrate 53.39% by an integrated technique of both wet high-intensity magnetic separation and vibration high gradient magnetic separation based on a limonite [4]. Hu Ding-bao studied the process of high intensity magnetic separation-reverse flotation and reduction roasting-separation on a limonite, which concluded that the iron concentrate grade could respectively reach 56.01% and 60.40% [5]. The above results indicated that, it is difficult to improve the iron grade only by physical separation methods, but it could greatly improve the grade of TFe by magnetic roasting-separation process. However, there is still no mature technology for mass production due to the complexity of ore itself, which leads to difficult recycle, high energy consumption and less profit. Zhang Han-quan did some researches on reduction roasting-magnetic separation in resistance furnace for a refractory hematite-limonite mix. The results had shown that it could raise the grade of iron concentrate to 60.00% and recovery 93.27%, but it is hard to get a higher grade of iron concentrate because of difficult separation from the fine grain size and tight connection of silica and iron oxides [6]. Li Guang-tao adopted reduction roasting-low intensity magnetic separation-reverse flotation process on a high phosphorus hematite limonite, and finally claimed that the iron grade and recovery is 60.92% and 72.74% respectively [7]. M.A.Youssef studied magnetic roasting-separating process on a monolitic limonite, using H2 and CO as reductant, with the optimal product iron grade and recovery is respectively 59.60% and 90.00% [8]. Christoph Feilmayr made a detailed study about reduction of limonite in the roasting process in fluidized bed and material change behavior, and found that limonite has faster reduction speed than other types, and thus put forward that the phase-boundary reaction is the rate determining step in reduction process [9]. In this experiment, it compares the differences between resistance furnace heating magnetic roasting and microwave heating magnetic roasting of coal-containing limonite pellets, and draws the main attention to the latter.


Hu B.,Central South University | Huang Z.-C.,Central South University | Jiang T.,Central South University | Peng H.,Changsha SYNO THERM Co.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2012

To study the coal-based direct reduction behavior and temperature rising characteristics of oxidized pellets in microwave shaft furnace, this experiment first prepared several groups iron oxide pellets at different reduction degree by control roasting time in condition of gaseous reducing agent from iron concentrate pellets, then based on structure and properties of iron oxide pellets at different reduction degree, a serials of research about temperature rising characteristics and reduction behavior of them were done in microwave field. The electromagnetic properties results show that the rate of temperature rising of iron oxide powder in microwave field from higher to lower rate is: Fe 3O 4, Fe 2O 3, Fe, FeO. The reduction results and mineralogical structure of pellets after microwave heating show that Fe 2O 3 has longer reduction time and several changes of physical phase, and makes the rate of reduction reaction mismatching with temperature and reduction atmosphere; Fe 3O 4 has a rapid heating rate and loose structure which is helpful to reduction, but while ferrous oxide appears in the pellet, the rate of reduction decreases because the porosity reduced and temperature rising rate slowed. When reduction degree reaches 66.90%, the pellet surface metallization has a developed porosity and stronger electromagnetic wave absorbency which has a fast reduction when gasification reaction is carried out effectively.


Huang Z.-C.,Central South University | Wang H.,Central South University | Hu B.,Central South University | Peng H.,Changsha SYNO THERM Co. | Xia G.-B.,Changsha SYNO THERM Co.
TMS Annual Meeting | Year: 2011

The temperature rising characteristics and reaction of the reduction of iron oxide pellets with anthracite fines were studied using a MW-L0316V microwave oven and Leica-DM-RXP polarizing microscope. The results show that iron oxide pellets and anthracite fines have good microwave absorbing properties, and high temperature and reducing atmosphere in a relatively short time for reduction of iron oxide pellets can be achieved. The reduction reaction, which follows the unreacted core model, is rapid and the metallization increases from 13.41% to 56.57% as the reduction end point temperature increases from 850°C to 950°C. The iron is formed, fine grain crystals of iron are transferred and the contraction of metal phase occurs firstly at the surface of pellets, which hinders the reduction reaction at the center of pellets. The rate of reduction reaction increases slowly as the reduction end point temperature increases from 950°C to 1050°C.

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