颗粒表面金属铁析出规律的热力学研究

doi:10.11949/0438-1157.20190931

摘要/Abstract

摘要：

从热力学角度出发，揭示了还原条件对高温气基还原过程中颗粒表面铁析出行为的影响规律，提出了通过改变还原气氛调控铁析出形貌的操控方法。研究表明在CO中混入H₂可以加快铁晶粒的生长速率，同时增加还原初期矿粉表面的铁形核数量，导致矿粉表面新生成的金属铁由晶须状转变为致密状。随着CO-CO₂中CO₂含量的升高，矿粉表面新生成的金属铁会由“锋利”的晶须状转变为“仙人掌状”，并且表面铁的分布密度会变小。随着还原温度的降低，矿粉表面铁晶须的强度会变弱。

关键词: 铁析出规律, 热力学, 形貌调控, 还原, 颗粒物料

Abstract:

The influence of reduction conditions on the morphology of newly formed metallic iron during high temperature gas-based reduction of iron ore are studied from the standpoint of thermodynamic analysis, and the solutions for controlling iron morphology through regulation of reduction conditions are proposed. Experimental results showed that addition of H₂ in CO could not only accelerate the growth rate of iron grains, but also increase the amounts of iron nuclei, resulting in the transformation of fibrous iron into dense one, addition of CO₂ in CO could transform the“sharp-pointed”iron whiskers into“cactus-like”ones, decrease of reduction temperature could lower the strength of fibrous iron.

Key words: precipitation behavior of iron, thermodynamics, regulation of iron morphology, reduction, granular materials

中图分类号:

TQ 021.2

杜占. 颗粒表面金属铁析出规律的热力学研究[J]. 化工学报, 2019, 70(11): 4143-4152.

Zhan DU. Thermodynamic studies on behavior of newly formed metallic iron on surface of particles[J]. CIESC Journal, 2019, 70(11): 4143-4152.

图/表 14

表1 智利精粉的化学组成

Table 1 Chemical composition of Chilean iron ore

Composition	Content /%(mass)
TFe	61.13
FeO	25.43
CaO	0.83
MgO	4.32
Al₂O₃	0.84
SiO₂	6.02
TiO₂	0.11

图1 智利精粉的表面形貌

Fig.1 Surface morphology of Chilean iron ore

图2 流化还原系统装置

Fig.2 Experimental apparatus used for fluidized bed reduction1—gas cylinder; 2—shutoff valve; 3—mass flowmeter; 4—fluidized bed; 5—electric resistance furnace; 6—thermocouple; 7—temperature controller; 8—pressure sensor; 9—computer

图3 800℃下铁矿粉在不同比例CO-H2中还原时的金属化率曲线

Fig.3 Metallization curves of iron ore fines as a function of time in CO-H2 mixtures at 800℃

图4 800℃下矿粉在不同比例CO-H2中还原后的表面铁析出形貌（金属化率约为22%）

Fig.4 Surface morphology of as-reduced samples in CO-H2 mixtures at 800℃(metallization degree is about 22%)

图5 纯H2和纯CO中铁矿粉还原初期的剖面图（金属化率约为5%）

Fig.5 Cross sectional views of as-reduced samples in H2 and CO during initial reduction period(metallization degree is about 5%)

图6 纯H2和纯CO中还原时金属铁的析出机理

Fig.6 Conceptual diagram for precipitation mechanism of iron in H2 and CO

图7 铁矿粉在800℃下H2/(H2+CO)=30%(vol)中预还原5 min，然后再在纯CO中还原至金属化率为22%左右时的表面形貌

Fig.7 Surface morphology of as-reduced sample by pre-reduction in H2/(H2+CO)=30%(vol) for 5 min, metallization degree is about 22%

图8 800℃下铁矿粉在不同比例CO-CO2中还原时的金属化率曲线

Fig.8 Metallization curves of iron ore fines as a function of time in CO-CO2 mixtures at 800℃

表2 800℃下不同比例CO-CO2中的热力学驱动力

Table 2 Thermodynamic driving forces in CO-CO2 mixtures at 800℃

CO₂ /(CO+CO₂)/%(vol)	ΔG/ (kJ/mol)
10	-33.8
20	-18.3
30	-8.7
CO_{2 Fe/oxide eq}=41.1%(vol)	0

图9 800℃下矿粉在不同比例CO-CO2中还原后的铁析出形貌(金属化率约为15%)

Fig.9 Surface morphology of as-reduced samples in CO-CO2 mixtures at 800℃(metallization degree is about 15%)

图10 纯CO中铁矿粉在不同温度下还原时的金属化率曲线

Fig.10 Metallization curves of iron ore fines as a function of time in CO at different temperatures

图11 矿粉在纯CO中不同温度下还原后的铁析出形貌（金属化率约为20%）

Fig.11 Surface morphology of as-reduced samples in CO at different temperatures(metallization degree is about 20%)

图12 铁氧化物在CO-CO2中还原时的热力学分析

Fig.12 Thermodynamic analyses of reduction of iron oxides in CO

参考文献 33

1	GransdenJ F, SheasbyJ S. Sticking of iron ore during reduction by hydrogen in a fluidized bed[J]. Can. Metall. Quart., 1974, 13(4): 649-657.
2	HayashiS, SayamaS, IguchiY. Relation between sulfur pressure and sticking of fine iron ores in fluidized bed reduction[J]. ISIJ Int., 1990, 30(9): 722-730.
3	HayashiS, IguchiY. Factors affecting the sticking of fine iron ores during fluidized bed reduction[J]. ISIJ Int., 1992, 32(9): 962-971.
4	HayashiS, SawaiS, IguchiY. Influence of coating oxide and sulfur pressure on sticking during fluidized bed reduction of iron ores[J]. ISIJ Int., 1993, 33(10): 1078-1087.
5	ManzooriA R, AgarwalP K. Agglomeration and defluidization under simulated circulating fluidized-bed combustion conditions[J]. Fuel, 1994, 73(4): 563-568.
6	MikamiT, KamiyaH, HorioM. The mechanism of defluidization of iron particles in a fluidized bed[J]. Powder Technol., 1996, 89: 231-238.
7	SevilleJ P K, Silomon-PflugH, KnightP C. Modeling of sintering in high temperature gas fluidization[J]. Powder Technol., 1998, 97: 160-169.
8	KomatinaM, GudenauH W. The sticking problem during direct reduction of fine iron ore in fluidized bed[J]. Metalurgija, 2004, 10(204): 309-328.
9	LinC, PengT, WangW. Effect of particle size distribution on agglomeration/defluidization during fluidized bed combustion[J]. Powder Technol., 2011, 207: 290-295.
10	ShaoJ, GuoZ, TangH. Influence of temperature on sticking behavior of iron powder in fluidized bed[J]. ISIJ Int., 2011, 51(8): 1290-1295.
11	ZhongY, WangZ, GuoZ, et al. Defluidization behavior of iron powders at elevated temperature: influence of fluidizing gas and particle adhesion[J]. Powder Technol., 2012, 230: 225-231.
12	ZhuQ, WuR, LiH. Direct reduction of hematite powders in a fluidized bed reactor[J]. Particuology, 2013, 11(3): 294-300.
13	ZhongY, WangZ, GuoZ, TangQ. Prediction of defluidization behavior of iron powder in a fluidized bed at elevated temperatures: theoretical model and experimental verification[J]. Powder Technol., 2013, 249: 175-180.
14	LeiC, ZhuQ, LiH. Experimental and theoretical study on the fluidization behaviors of iron powder at high temperature[J]. Chem. Eng. Sci., 2014, 118: 59-69.
15	SinghM, BjörkmanB. Effect of processing parameters on the swelling behavior of cement-bonded briquettes[J]. ISIJ Int., 2004, 44(1): 59-68.
16	BarustanM I A, JungS M. Morphology of iron and agglomeration behavior during reduction of iron oxide fines[J]. Metals and Materials International, 2019, 25(4): 1083-1097.
17	SchillerM. Die Mikromorphologie der eisenphase als fogle der reduktion von eisenoxiden [D]. Germany: RWTH Aachen, 1987.
18	WangH, SohnH. Effects of reducing gas on swelling and iron whisker formation during the reduction of iron oxide compact[J]. Steel Res. Int., 2012, 83(9): 903-909.
19	邵剑华, 郭占成, 唐惠庆. 流态化还原铁精粉黏结过程试验研究[J]. 钢铁, 2011, 46(2): 7-11.
	ShaoJ H, GuoZ C, TangH Q. Experimental study on sticking process during reduction of iron ore concentrate fines in fluidized bed[J]. Iron & Steel, 2011, 46(2): 7-11.
20	邵剑华, 郭占成, 唐惠庆. 还原气氛对流态化还原铁矿粉黏结失流的影响[J]. 北京科技大学学报, 2013, 35(3): 273-281.
	ShaoJ H, GuoZ C, TangH Q. Influence of reducing atmosphere on the sticking during reduction of iron ore fines in a fluidized bed[J]. J. Univ. Sci. Technol. B., 2013, 35(3): 273-281.
21	WangH, SohnH. Effects of firing and reduction conditions on swelling and iron whisker formation during the reduction of iron oxide compact[J]. ISIJ Int., 2011, 51(6): 906-912.
22	WangH, SohnH. Effect of CaO and SiO₂ on swelling and iron whisker formation during reduction of iron oxide compact[J]. Ironmaking Steelmaking, 2011, 38(6): 447-452.
23	WagnerC. Mechanism of the reduction of oxides and sulphides to metals[J]. J. Metal., 1952, 4(2): 214-216.
24	NicolleR, RistA. Mechanism of whisker growth in the reduction of wustite[J]. Metall. Mater. Trans. B, 1979, 10(3): 429-438.
25	ZhangT, LeiC, ZhuQ. Reduction of fine iron ore via a two-step fluidized bed direct reduction process[J]. Powder Technol., 2014, 254: 1-11.
26	黄希祜. 钢铁冶金原理[M]. 北京: 冶金工业出版社, 2013.
	HuangX G. Principle of Iron and Steel Metallurgy[M]. Beijing: Metallurgical Industry Press, 2013.
27	LuW K. Mechanism of abnormal swelling during the reduction of iron ore pellets[J]. Scand. J. Metall., 1974, 3(2): 49-55.
28	YamashitaT, NakadaT, NagataK. In-situ observation of Fe_0.94O reduction at high temperature with the use of optical microscopy[J]. Metall. Mater. Trans. B, 2007, 38(2): 185-191.
29	程传煊. 表面物理化学[M]. 北京: 科学技术文献出版社, 1995.
	ChengC X. Physical Chemistry of Surfaces[M]. Beijing: Science and Technology Literature Publishing House, 1995.
30	El-GeassyA A, NasrM I, HessienM M. Effect of reducing gas on the volume change during reduction of iron oxide compacts[J]. ISIJ Int., 1996, 36(6): 640-649.
31	MatthewS P, HayesP C. Microstructural changes occurring during the gaseous reduction of magnetite[J]. Metall. Mater. Trans. B, 1990, 21(1): 153-172.
32	BrennerS S. Growth and properties of “whiskers”[J]. Science, 1958, 128(3324): 569-575.
33	KanekoT. Growth rate of iron whiskers[J]. J. Cryst. Growth, 1978, 44(1): 14-22.

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