钢渣中磷酸盐的选择性富集与分离

发布时间：2018-04-25 08:50

本文选题：炼钢炉渣 + 离子与分子共存理论　；参考：《北京科技大学》2017年博士论文

【摘要】：随着钢渣大量堆积以及磷矿资源的匮乏,如何实现钢渣循环利用和高品位磷资源的回收成为众多冶金企业关注焦点之一。本论文针对钢渣中磷的组成及赋存特点,提出采用选择性富集与相分离的方法来分离钢渣中磷酸盐的思路,阐明了钢渣中磷酸盐的结晶行为,揭示了其选择性富集、选择性结晶长大、及相分离过程中的影响因素。选择性富集与分离的学术思想,不仅能够充分利用钢渣显热,而且能够实现钢渣中磷酸盐及富铁相的分离,基本实现了钢渣的高效回收利用。木论文采用离子与分子共存理论(IMCT),开发出计算CaO-SiO_2-FeO-Fe_2O_3-P_2O_5五元渣系中结构单元或离子对的质量作用浓度N_i的热力学模型,即IMCT-N_i模型,并且.定义了评价钢渣中磷酸盐富集行为的富集可能性N_(_(ci-cj))和富集程度R_(ci-cj)两个参数,研究了五元渣系中磷酸盐的富集行为,并且通过设计的实验,验证了不同碱度范围的钢渣中磷酸盐的富集机理。五元渣系在1773 K时可生成3CaO·P_2O_5(C_3P),其易与2CaO·SiO_2(C_2S)结合,在合适的冷却制度下,生成2CaO·SiO_2-3CaO·P_2O_5 (C_2S-C_3P)固溶体；高碱度(2.0B3.5)条件下定义的N_(C_2S-C_3P)或R_(C_2S-C_3P)与炉渣二元碱度或(%FetO)/(%CaO)呈非对称抛物线关系；当碱度为2.5,(%Fe_tO)/(%CaO)为0.955时,定义的N_(C_2S-C_3P)或R_(C_2S-C_3P)达到最大具体数值,其中RC_2S-C_3P约为85%。低碱度(1.0B2.0)五元渣系中随着碱度逐步增高,渣中磷酸盐富集相C_2S-C_3P中P_2O_5的质量百分数(%P_2O_5)呈现一种倒“V”型变化。当碱度为1.3时,渣中磷酸盐富集相中(%P_2O_5)达到最大约为30%。通过理论计算和实验检测相结合的方式, 研究了CaO-SiO_2-FeO-Fe_2O_3-Al_2O_3-P_2O_5六元渣系和CaO-SiO_2-MgO-FeO-Fe_2O_3-MnO-Al_2O_3-P_2O_5元渣系中磷酸盐富集行为,获得了多元渣系在冷却过程中磷酸盐达到最优的炉渣成分,阐明了多元炼钢渣系中决定磷酸盐富集的关键性因素是渣中游离C_2S (f-C_2S)的生成量。多元炼钢渣系中Al_2O_3组元和炉渣中C_2S结合生成钙铝黄长石C_2AS相,可降低炼钢炉渣中游离C_2S(f-C_2S)相的量,进而间接影响炼钢炉渣中磷酸盐富集相nC_2S-C_3P内(%P_2O_5)含量。因此,六元炼钢炉渣获得较好磷酸盐富集程度,炉渣二元碱度B和Al_2O_3含量需要满足(%Al_2O_3)=-27.70+21.62B的耦合关系,此时磷酸盐富集相中(%P_2O_5)约达到30.0%；八元炼钢炉渣四元碱度Q为1.23时,磷酸盐富集率较高,磷酸盐富集相中(%P_2O_5)可达24.23%。在前期热力学研究的基础上,对不同渣系中磷酸盐的结晶动力学进行了研究。采用Image-Pro-Plus(IPP)图像分析软件,统计计算出了不同温度制度(取出温度、保温时间、冷却速率)下,上述五元和八元炼钢渣系中磷酸盐富集相的析晶而积,建立了磷酸盐富集相的平均结晶分数与温度之间的关系：计算得到了炉渣在冷却过程中磷酸盐析出的结晶参数;通过不同速率常数k(T),获得了不同模型的表观活化能E_i。五元渣系中磷酸盐在结晶过程中的Avrami常数n值平均为0.472,八元渣系的Avrami常数n值平均为0.442;两个渣系的磷酸盐结晶机理基本一致：均为扩散反应控速,生成棒状一维结构,且形核速率随时间下降。五元渣系磷酸盐富磷相结晶过程中,Van't Hoff速率常数Ink的表达式Innk=53.80+11163.69/T-7.49InT-0.005T,表观活化能E=-278.52 KJ/mol八元渣系磷酸盐富磷相结晶过程中,Van't Hoff速率常数Ink的表达式：Ink=40.5+7966.67/T-5.67InT-0.004T,表观活化能E=-189.84K.J/mol。通过调整炼钢炉渣成分及合适冷却制度,得到了大颗粒尺寸的磷酸盐富集相,采用磁选技术对其进行了分离的初步研究。当控制磁选条件为：炉渣破碎粒度200目以上,磁选强度为3.0 KOe时,五元炼钢炉渣中磷组分的磁选率为74%,铁组分的磁选率为69%；八元炼钢炉渣中磷组分的磁选率为69.84%,铁组分的磁选率为67.74%。
[Abstract]:With the accumulation of steel slag and the shortage of phosphate mineral resources, how to recycle steel slag and recycle high grade phosphorus resources has become one of the focus of attention of many metallurgical enterprises. In this paper, the idea of separating phosphate in steel slag by selective enrichment and phase separation is proposed in view of the composition and occurrence characteristics of phosphorus in steel slag. The crystallization behavior of phosphate in steel slag reveals its selective enrichment, selective crystallization and growth, and the influencing factors in the process of phase separation. The academic thought of selective enrichment and separation can not only make full use of the explicit heat of steel slag, but also realize the separation of phosphate and iron rich phase in steel slag, and basically realize the efficient recovery of steel slag. Using the theory of coexistence of ions and molecules (IMCT), the paper developed a thermodynamic model for calculating the mass action concentration N_i of the structural unit or ion pair in the CaO-SiO_2-FeO-Fe_2O_3-P_2O_5 five element slag system, that is, the IMCT-N_i model, and defined the enrichment possibility N_ (ci-cj) and the enrichment degree R_ (ci-) for the evaluation of phosphate enrichment in steel slag. CJ) two parameters, the enrichment behavior of phosphate in the five element slag system was studied, and the enrichment mechanism of phosphate in steel slag with different alkalinity range was verified by the design experiment. The five element slag system can produce 3CaO P_2O_5 (C_3P) at 1773 K, which is easy to combine with 2CaO SiO_2 (C_2S) and generates 2CaO SiO_2-3CaO. P_2O_ under the appropriate cooling system. 5 (C_2S-C_3P) solid solution; the N_ (C_2S-C_3P) or R_ (C_2S-C_3P) defined under the condition of high alkalinity (2.0B3.5) has an asymmetrical parabolic relationship with the two yuan alkalinity or (%FetO) / (%CaO) of the slag; when the alkalinity is 2.5, (%Fe_tO) / (%CaO) 0.955, the definition of N_ (C_2S-C_3P) or the maximum specific value is reached, of which it is about low alkalinity. (1.0B2.0) with the increase of alkalinity in the five element slag system, the mass percentage (%P_2O_5) of P_2O_5 in the phosphate enriched phase C_2S-C_3P in the slag presents an inverted "V" type. When the alkalinity is 1.3, the maximum of the phosphate enriched phase in the slag (%P_2O_5) is approximately 30%. through the combination of theoretical calculation and experimental detection, and CaO-SiO_2- has been studied. The enrichment behavior of phosphate in the FeO-Fe_2O_3-Al_2O_3-P_2O_5 six element slag system and the CaO-SiO_2-MgO-FeO-Fe_2O_3-MnO-Al_2O_3-P_2O_5 element slag system has been obtained, and the optimum slag composition is obtained during the cooling process of the multiple slag system. The key factor for determining the phosphate concentration in the multiple steelmaking slag system is the birth of the free C_2S (f-C_2S) in the slag. The amount of Al_2O_3 component in the slag system of multiple steelmaking slag and C_2S in slag to produce calcium aluminum feldspar C_2AS phase can reduce the amount of free C_2S (f-C_2S) phase in the slag of steelmaking, and then indirectly affect the content of nC_2S-C_3P (%P_2O_5) in the phosphate enrichment phase of the steelmaking slag. Therefore, the slag of six yuan smelting steel furnace slag is enriched with good phosphate, and the slag is two yuan base. The content of B and Al_2O_3 needs to meet the coupling relationship of (%Al_2O_3) =-27.70+21.62B, at this time, the phosphate enrichment phase (%P_2O_5) is about 30%, and when the four yuan alkalinity Q of the eight element steelmaking slag is 1.23, the phosphate enrichment rate is higher, and the phosphate enriched phase (%P_2O_5) can reach 24.23%. on the basis of the previous thermodynamic study, and phosphate in different slag systems Image-Pro-Plus (IPP) image analysis software was used to calculate the crystallization of the phosphate enriched phase in the five and eight yuan steelmaking slag system, and the correlation between the average crystalline fraction of the phosphate enriched phase and the temperature was established. The crystallization parameters of the phosphoric acid salting out of the slag during the cooling process are calculated. Through the different rate constants K (T), the n value of the Avrami constant n in the crystallization process of the apparent activation energy E_i. of different models is 0.472, the average Avrami constant of the slag system is eight, and the average of the n value of the slag system is 0.442, and the two phosphates in the slag system. The crystal mechanism is basically the same as the diffusion reaction control speed, forming a rod like one-dimensional structure and decreasing the nucleation rate with time. The expression Innk=53.80+11163.69/T-7.49InT-0.005T of Van't Hoff rate constant Ink during the crystallization of phosphate rich phase of the five element slag system, the crystallization process of the apparent activation energy E= -278.52 KJ/mol in phosphate rich phosphorous phase The expression of Van't Hoff rate constant Ink: Ink=40.5+7966.67/T-5.67InT-0.004T, apparent activation energy E=-189.84K.J/mol. by adjusting the composition of steelmaking slag and suitable cooling system, a large particle size phosphate enriched phase was obtained, and a preliminary study of separation was carried out by magnetic separation technology. When the grain size is more than 200 mesh and the magnetic separation strength is 3 KOe, the magnetic separation rate of the phosphorus component in the slag of five yuan steelmaking is 74%, the magnetic separation rate of the iron component is 69%, the magnetic separation rate of the phosphorus component in the eight yuan steelmaking slag is 69.84%, and the magnetic separation rate of the iron component is 67.74%..

【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X757;O652.6

【参考文献】