磷石膏在低浓度硫酸中的溶解及相态变化

湿法磷酸生产过程副产大量磷石膏,因其含有较多杂质而无法直接利用,目前可采用硫酸酸浸处理提高磷石膏品质。为弄清酸浸过程中石膏的溶解性能和结晶形态的变化,本文探讨了在0～80 ℃、0～30%的硫酸浓度条件下,磷石膏在硫酸溶液中的溶解度大小、结晶形貌、物相组成及结晶水含量的变化情况。实验结果表明,磷石膏在硫酸溶液中的溶解度随温度升高而升高,在80 ℃时达最大;随浓度升高呈先升后降的变化,在硫酸浓度为10%时溶解度最大。硫酸浓度小于10%时,磷石膏中二水硫酸钙溶解,但无新相生成,其形貌变化不大;硫酸浓度大于10%时,二水硫酸钙溶解,同时再结晶转化成无水硫酸钙,最终导致磷石膏形貌和相态发生了改变,溶解度随硫酸浓度升高而降低。     

磷精矿脱除湿法稀磷酸中硫酸根的实验研究

二水法湿法磷酸中常含有一定量硫酸根杂质,硫酸根的存在不仅降低了磷酸品质,而且增加了磷酸对硫酸的消耗。采用磷精矿为脱硫剂,研究了脱硫剂用量、反应时间、反应温度对湿法磷酸中硫酸根脱除的影响,并测算了二水硫酸钙在湿法磷酸中的溶度积。结果表明：固液质量比为5%的磷精矿粉可有效地脱除稀磷酸中的硫酸根,反应温度建议不超过70 ℃,反应2 h即可。此外,在稀磷酸中测算硫酸钙的溶度积为2×10^-2~3×10^-2。该研究对湿法磷酸生产过程中在降低硫酸根含量并提高湿法磷酸品质方面具有一定的指导意义。     

Continuous precipitation of calcium sulfate dihydrate from waste sulfuric acid and lime

Precipitation of calcium sulfate dihydrate, gypsum, from (i) a pure sulfuric acid/lime suspension and (ii) a waste sulfuric acid/lime suspension in a continuous pilot plant in the temperature range from 40 °C to 80 °C was studied. It was observed that in the case of waste sulfuric acid with a high content of Mg²⁺ and Fe²⁺ ions, several hours after the beginning of the precipitation, partial dissolution of the product and modification of the crystals from needle‐ and plate‐like to agglomerated structures occurred. It is suggested that the secondary changes occur due to the increased concentration of Mg²⁺ and Fe²⁺ ions in the reactor. Below 60 °C, and above 70 °C plate‐like and needle‐like single crystals respectively were formed. The mean size (d₅₀) of the crystals was found to increase with increasing temperature and decrease with the initial concentration of lime. Gypsum produced between 70 °C and 80 °C is suitable for further processing for construction plaster. In a precipitation process with pure sulfuric acid only single perfect needle‐like crystals occurred. Copyright © 2005 Society of Chemical Industry     

盐酸法粗磷酸中氯化钙的去除研究现状

磷酸是一种重要的化工原料,其用途十分广泛。使用传统硫酸法会产生大量磷石膏,磷石膏在利用方面缺乏较为完整成熟的技术,磷石膏利用率较低,容易造成环境污染,给企业带来成本压力。并且硫酸法对磷矿品位有一定要求,相比之下盐酸法具有其独特优势。盐酸法粗磷酸中主要成分是磷酸和氯化钙,氯化钙的去除技术和综合利用是影响盐酸法大规模工业应用的关键所在。介绍了萃取法、三聚氰胺法、离子交换法、液膜法去除氯化钙技术以及氯化钙废液的综合利用现状,针对盐酸法工艺存在的问题提出了建议。指出经济、高效地去除盐酸法粗磷酸中的氯化钙以及对其有效利用是盐酸法湿法磷酸工艺推广应用的关键。     

正辛醇+煤油混合溶剂萃取净化湿法磷酸工艺研究

选用新型高效萃取体系正辛醇+煤油混合溶剂,研究了正辛醇+煤油混合溶剂在萃取净化湿法磷酸过程中萃取温度和相比（萃取剂与磷酸的体积比）与磷酸萃取率和杂质分离系数之间的关系, 考察了硫酸和铁两种杂质对磷酸萃取率和分配比的影响。实验表明: 随着相比提高, 磷酸萃取率上升, 各杂质分离系数提高。提高萃取温度和增加铁含量会使磷酸萃取率和分配比呈减小趋势,硫酸的存在有利于磷酸萃取。通过对正辛醇+煤油体系萃取湿法磷酸系统性的基础工艺研究,以期为设计工业化应用路线提供理论和技术支持。     

Intensification of the Sulfuric Acid Alkylation Process with Trifluoroacetic Acid

H₂SO₄ alkylation of isobutane and butene is one of the primary commercial processes used to produce alkylates. This work presents a technology for the intensification of sulfuric acid alkylation with the addition of trifluoroacetic acid (TFA). The addition of TFA increased the solubility of isobutane in H₂SO₄, decreased its viscosity, and adjusted the acidity of H₂SO₄. With the addition of TFA, the selectivity of C8 was dramatically improved from 36.8 to 95.7%. The TFA content, stirring speed, reaction temperature, volume ratio of acid to hydrocarbon (H/C), molar ratio of isobutane to 2-butene (I/O), reaction time, and reuse of H₂SO₄/TFA were also investigated in this work. Compared with the conventional process, the new technology provided a considerably higher quality alkylation with considerably lower energy consumption. © 2018 American Institute of Chemical Engineers AIChE J, 65: 113–119, 2019     

湿法磷酸体系磷石膏结晶过程与机理研究

湿法磷酸生产过程中硫酸钙结晶制约着磷石膏的品质,良好的硫酸钙结晶不仅能提高磷收率,还有利于磷石膏资源化利用。针对硫酸钙结晶调控问题,系统考察了在添加正辛醇条件下硫酸钙物相形貌随反应时间的变化规律,综合研究了磷石膏晶体结构变化和生长规律。结果表明,反应时间为7 h时磷石膏内残余总磷为0.36%,其中水溶性磷为0.18%,磷收率达到98.79%;磷石膏以（002）为主要晶面生长,结晶过程分为磷矿酸解、硫酸钙晶体颗粒长大、晶体破碎与二次结晶3个阶段,均匀的二水硫酸钙板条状结晶有助于提高磷石膏洗滤性能和洗涤效果。通过磷石膏结晶调控和变化过程研究,为湿法磷酸生产工艺参数选择和硫酸钙结晶过程调控提供参考和基础支撑。     

Characterization of fluorine-, aluminum-, silicon-, and phosphorus-containing complexes in wet-process phosphoric acid using nuclear magnetic resonance spectroscopy

Wet-process phosphoric acid is one product of the reaction between phosphate rock and sulfuric acid. The limiting step in this process occurs when the acid is filtered from the reaction slurry, which also contains calcium sulfate (gypsum). The acid-soluble impurities present in the phosphate rock (e.g., fluorine, silicon, and aluminum) form complexes in wet-process acid which can alter the optimum size and habit of gypsum crystals, thereby reducing the filtration rates. Fluorine-containing complexes are strongly suspected of being potent modifiers of the crystal habit of gypsum. However, the identities of the complexes responsible for the habit modification have not been established. The identities of the complexes formed in phosphoric acid (28% P₂O₅) containing additions of fluorine (HF and H₂SiF₆) and aluminum [Al(NO₃)₃ · 9H₂O or AlF₃ · 9H₂O] were established in this study by using fluorine-19 (¹⁹F) and phosphorus-31 (³¹P) nuclear magnetic resonance (NMR) spectroscopies. Peaks due to aluminum fluoride, fluorosilicate, and fluoroaluminum phosphate complexes were observed in the NMR spectra recorded from these solutions. In addition, the¹⁹F and³¹P NMR spectra of wet-process acids were recorded. These spectra contained peaks assigned to the hexafluorosilicate ion (major species), along with aluminum fluoride and fluoroaluminum phosphate complexes (minor species).     

盐酸法磷酸萃取相的洗涤和磷酸反萃取过程初探

研究了从以磷酸三丁酯（TBP）为主的萃取相中反萃取磷酸的过程,考察了一步法流程（以硫酸溶液通过沉淀反应去除磷酸萃取有机相中氯化钙的同时反萃取磷酸）以及二步法流程（先以硫酸沉淀反应去除氯化钙,后用去离子水反萃取磷酸）所得的反萃磷酸的净化效果。结果表明,采用一步法时,反萃取磷酸的品质受到硫酸钙溶解平衡的影响,钙含量较高;而采用二步法时,反萃磷酸中氯化钙的质量分数可降低至0.002 7%以下,n（磷酸）/n（钙离子）提升了65倍以上,但有机相中磷酸的洗损为20%左右;利用聚焦光反射测量技术（FBRM）对洗涤过程中硫酸钙在有机相中的结晶过程进行了在线监测,通过扫描电镜（SEM）和X射线衍射（XRD）等手段对副产硫酸钙的晶体形貌和物相组成进行了分析,结果表明实验条件下洗涤10 min时,体系中的Ca²⁺生成半水石膏（CaSO₄·0.5H₂O）。计算表明,该盐酸法磷酸工艺洗涤过程中副产石膏值（以二水硫酸钙计）仅为二水硫酸法的8.7%,显著降低了湿法磷酸过程中的石膏处理量。     

Purification of Wet‐Process Phosphoric Acid by Hydrogen Peroxide Oxidation,Activated Carbon Adsorption and Electrooxidation

In this work, three technologies are studied for the purification of phosphoric acid produced by the wet process: chemical oxidation with hydrogen peroxide, adsorption onto activated carbon, and electrochemical oxidation by boron‐doped diamond anodes. The treatment of wet‐process phosphoric acid by chemical oxidation with H₂O₂ as oxidizing agent can remove 75 % of the initial TOC as maximum, indicating that this wet‐process phosphoric acid contains an important amount of organics that cannot be oxidized by hydrogen peroxide under the operation conditions used. High temperatures and hydrogen peroxide/TOC ratios close to 150 g H₂O₂/g TOC allow obtaining the best chemical oxidation results. The adsorption onto activated carbon can remove between 40 and 60 % of the initial TOC as maximum. Adsorption times of 2 hours and activated carbon/WPA ratios close to 12 g AC/Kg WTP assure both steady state and maximum adsorption of organics. The electrochemical process is the only technique by which complete mineralization of WPA organics can be achieved. Operating at 60 mA cm^–2 and at room temperature, high current efficiencies are achieved which only seem to decrease by mass transport limitations.     

Production of phosphoric acid with low content of impurities

The present work is to study the possibility for controlled distribution of the impurities when they are decomposed by sulphuric acid to wet phosphoric acid and phosphogypsum, as well as generating technological conditions for production of clean wet phosphoric acid and its derivatives - phosphoric fertilizers, food phosphates and other phosphoric products.A coefficient of distribution D_A is introduced as a general criterion for elements dispersion. The study includes relationships between the weight ratio sulphuric acid/natural phosphate and D_A; the period of decomposition and D_A; the particle's size content of the natural phosphate and D_A. The obtained experimental data and relationships about the influence of the above discussed technological parameters on dispersion of more than 23 elements allow for control of that process in wet phosphoric acid and phosphogypsum by selecting specific technological conditions. Thus, depending on the requirements of acid's consumers and procedures for secondary processing of phosphogypsum to end-products, a selective decomposition of the natural phosphates to phosphoric acid and phosphogypsum can be carried out with content of the impurities in those products varying in narrow limits.     

缓释阻垢剂在磷酸浓缩中的应用

二水湿法磷酸在浓缩过程中由于含有少量的金属离子和硫酸根、氟硅酸根离子,容易在换热器内形成稳定的物质沉积在设备管道内壁,造成系统堵塞,给系统生产带来严重影响。因此拟通过添加缓释阻垢剂来抑制结垢的形成,从浓缩系统试验来看效果比较明显,具有极大的应用和推广价值。     

浅析磷酸输送管道清洗

随着磷化工的发展,湿法磷酸在磷酸生产工业中的地位日趋重要。在磷复肥生产过程中,由于磷酸含有一定量的杂质,经常出现管线堵塞而影响生产,需对管线进行清理,一般情况均用稀硫酸溶液对管线进行清洗。利用湿法磷酸半水法和二水法工艺原理的不同,用浓磷酸和稀磷酸间歇输送的方法,具有一定的可行性。     

二水硫酸钙结晶过程研究进展

目前世界上的磷酸工业都以湿法为主,而湿法磷酸生产的关键技术是硫酸钙的结晶.结晶的质量会影响到整个的生产工艺.本文综述了二水硫酸钙结晶过程的最新研究进展,从各个角度介绍了外部条件对硫酸钙结晶的影响,以达到对二水硫酸钙结晶的各种技术有一种比较客观综合的理解和认识,最后对未来二水硫酸钙结晶过程的研究方向作了探讨.     

Purification process of phosphoric acid by vertical zone‐melting technique

The efficiency of vertical zone‐melting technique as a function of molten‐zone length, number of zone passes, molten‐zone velocity and phosphoric acid concentration on the purification process of phosphoric acid is studied. The results showed that adopting a relatively long molten‐zone length in the initial passes to effect a rapid movement of impurities and a short molten‐zone length in the later passes to obtain greater purification; additional zone‐passes cannot be made as impurities redistribution approaches limiting distribution; for stirring mechanism is not adopted in the present study and as diffusion is the only mixing process, slow molten‐zone velocity 3–6 mm h^?1 is better; the purification efficiency increases with phosphoric acid concentration, and 94–99.8% concentration of phosphoric acid is better. © 2012 Canadian Society for Chemical Engineering     

钙芒硝石膏深度提纯工艺的研究

钙芒硝石膏是工业上采用溶浸法生产元明粉的副产尾矿,与脱硫石膏和磷石膏等工业副产石膏相比其杂质含量高、纯度低、利用价值低。采用酸浸-重结晶工艺对钙芒硝石膏进行提纯,通过酸浸去除钙芒硝石膏中的酸溶性杂质,并将二水硫酸钙（DH）脱水转化为无水硫酸钙（AH）,然后控制水化条件,使AH水化为大尺寸的DH晶体,并与小尺寸的酸不溶性杂质分离开来,得到高纯度的二水石膏。研究了硫酸浓度、水化激发剂、液固质量比、反应时间等对石膏提纯的影响。研究结果表明：常压下,在硫酸酸洗液质量分数为35%、反应温度为80 ℃、石膏与硫酸溶液固液质量比为1∶5、酸洗时间为2 h时能有效去除钙芒硝石膏中的酸溶性杂质;在水化硫酸质量分数为5%、硫酸钾质量分数为1.74%、反应温度为25 ℃、固液质量比为1∶6、陈化时间为18 h时能有效去除钙芒硝石膏中酸不溶性杂质,提纯后的石膏纯度可达97%以上。     

硫酸钠生产氟硅酸钠的废水回收技术

硫酸钠法生产氟硅酸钠废水中含有大量的钠离子、硅胶固形物和叫（H2SO4）3％～5％的硫酸．氟硅酸钠废水综合回收利用技术采用沉降分离固形物,上层清液加热后用于二水物湿法磷酸过滤系统,然后返回萃取槽,回收其中的硫酸。该项技术回收硫酸和节约处理氟硅酸钠废水费用达1348万元．折每吨P2O5节约成本22.42元。     

Parametric study on the production of phosphoric acid by the dihydrate process

In this work a computer program has been developed to simulate a three-CSTR pilot plant leaching process of phosphate rock with sulfuric acid for the production of phosphoric acid and precipitation of calcium sulfate dihydrate as a byproduct. The simulation model has been examined with real experimental data obtained from the Jordan Phosphate Mines Company (JPMC), a phosphoric acid pilot plant at Rusaifa, Jordan. The predicted results are in very good agreement with the experimental data with a relative absolute error of less than 3.5%.A parametric study has been made to find the optimum operating conditions of the pilot plant for a given phosphate rock feed flow rate, chemical composition, and particle size distribution. The effect of varying reactor(s) temperature, sulfuric acid feed rate, agitator–impeller speed, ratio of slurry recycle to feed rate, and ratio of return acid to feed rate have been investigated. A reactor temperature of 80°C, slurry recycle to feed ratio of 80, and return acid to feed ratio of 2.5 have been found to give best results. The optimum conditions for sulfuric acid feed rate and agitator speed are determined only from power limitations and economics of the plant itself.     

Synthesis,Structure and Electrical Properties of Mo‐doped CeO2–Materials for SOFCs

In this paper, we report the synthesis, structure and electrical conductivity of Mo‐doped compounds with a nominal chemical formula of Ce_1–xMo_xO_2+δ (x = 0.05, 0.07, 0.1) (CMO). The formation of fluorite‐like structure with a small amount of Ce₈Mo₁₂O₄₉ impurity (JCPDS Card No. 31‐0330) was confirmed using a powder X‐ray diffraction (PXRD). The fluoride‐type structure was retained under wet H₂ and CH₄ atmospheres at 700 and 800 °C, while diffraction peaks due to metal Mo were observed in dry H₂ under the same condition. AC impedance measurements showed that the total conductivity increases with increasing Mo content in CMO, and among the investigated samples, Ce_0.9Mo_0.1O_2+δ exhibited the highest electrical conductivity with a value of 2.8 × 10^–4 and 5.08 × 10^–2 S cm^–1 at 550 °C in air and wet H₂, respectively. The electrical conductivity was found to be nearly the same, especially at high temperatures, in air, O₂ and N₂. Chemical compatibility of Ce_0.9Mo_0.1O_2+δ with 10 mol‐% Y₂O₃ stabilised ZrO₂ (YSZ) and Ce_0.9Gd_0.1O_1.95 (CGO) oxide ion electrolytes in wet H₂ was evaluated at 800–1,000 °C, using PXRD and EDX analyses. PXRD showed that CMO was found to react with YSZ electrolyte at 1,000 °C. The area specific polarisation resistance (ASPR) of Ce_0.9Mo_0.1O_2+δ on YSZ was found to be 8.58 ohm cm² at 800 °C in wet H₂.     

Copper and cadmium extraction from highly concentrated phosphoric acid solutions using calcium alginate gels enclosing bis(2,4,4‐trimethylpentyl)thiophosphinic acid

The availability of alginate gels enclosing Cyanex 302 [bis(2,4,4‐trimethylpentyl)thiophosphinic acid] for the uptake of cadmium and copper from highly concentrated solutions of industrial phosphoric acid wet process phosphoric acid (WPA)] was studied. For this purpose, beads of alginate gels enclosing microdrops of kerosene solutions of the industrial extractant Cyanex 302 at different concentrations were prepared. The experimental procedure gives rise to a composite bead in which alginate is the continuous phase and the organic extractant forms the discrete homogeneously distributed phase within the bead. The equilibrium in this three‐phase system (phosphoric acid–extractant solution–alginate gel) was modelled in terms of the corresponding distribution factors, the main chemical reactions and their equilibrium constants. Retention isotherms of both metal ions were obtained experimentally at four concentrations (1.0, 2.5, 5.0 and 7.5 mol L^?1) of pure phosphoric acid. High metal removal efficiency, due to liquid–liquid extraction processes, was observed even in the most acidic conditions. High values of the extraction constants were estimated, with the distribution coefficients between aqueous and alginate phase being near unity. Finally, the results obtained with industrial WPA are in close agreement with those predicted by the physicochemical model developed in synthetic media. Copyright © 2006 Society of Chemical Industry