Production of dicalcium phosphate by treatment of phosphate rock concentrate with nitric acid

This paper presents results laboratory experiments to test a new process for manufacture of dicalcium phosphate. The process is based on the nitric acidulation of phosphate rock concentrate, followed by neutralization of the extract liquor with calcium carbonate. The precipitated dicalcium phosphate is then separated from calcium nitrate solution by filtration. The dicalcium phosphate thus obtained contains 44–47% total P₂O₅ and can be used as fertilizer or, with an additional low pH filtration step, as animal feed supplement.     

Technological characterization of Anitapolis (Brazil) phosphate rock as feedstock for fused magnesium phosphate production

Fused magnesium phosphate seems to be a technical solution for some problems faced by the Brazilian industry of phosphate fertilizers, namely: high P₂O₅ losses in the fines of the beneficiation processes; high level of phosphorus fixation for water soluble fertilizers; Brazilian high dependency on sulfur for conventional phosphate fertilizers. The technological characterization of phosphate concentrate of Anitapolis, regarding the production of fused magnesium phosphate was thus carried out.The variables studied were MgO/SiO₂ ratio, fusion temperature and cooling rate. The products obtained in the tests were analyzed for P₂O₅ citric acid solubility and fluorine content. As expected, fast cooling showed the best results. MgO/SiO₂ molar ratio showed weak influence on the solubilization of P₂O₅ when fast cooling was used. Fluorine removal was low for all samples. This indicates that the product is not suitable for animal feed. The Anitapolis rock concentrate showed to be an excellent feedstock for production of fused magnesium phosphate.     

矿粉脱氟法生产饲料级磷酸氢钙工艺探讨

利用磷精矿粉脱氟法生产饲料级磷酸氢钙,介绍其脱氟原理、生产工艺流程,按脱氟净化生产净化磷酸,萃取过滤生产粗磷酸,石灰乳中和过滤生产饲钙,分别说明其工艺控制指标,并与两段中和法对比,说明该方法生产饲钙的特点是P2O5回收率高,磷矿、硫酸、石灰乳消耗低。     

Production of high-quality liquid fertilizers from wet-process acid via urea phosphate

A pilot-plant process is described that purifies wet-process phosphoric acid for the production of a high-quality urea-ammonium polyphosphate base solution. An intermediate product, crystalline urea phosphate, is produced from urea and merchant-grade (54% P₂O₅) wet-process phosphoric acid. The urea phosphate crystals contain only about 15 to 20% of the objectionable impurities (iron, aluminum, and magnesium) originally contained in the feed wet-process acid. The urea phosphate crystals are pyrolyzed, converting orthophosphate to polyphosphate with very little energy consumption. The resulting melt is dissolved and neutralized with ammonia to produce 14-29-0 liquid product of high polyphosphate content.     

Production of pure phosphoric acid from El-Sebaeya low-grade phosphate ore

The extraction of phosphoric acid by tributyl phosphate (TBP) in kerosene from hydrochloric acid leach liquor of El-Sebaeya low-grade phosphate ore was carried out. The influence of various factors affecting the leaching process such as particle size, reaction time, acid concentration, liquid/solid mass ratio, reaction temperature and stirring speed were thoroughly studied to estimate the favor phosphate ore dissolution in relation to impurity. Thereafter, the effects controlling the extraction step, including shaking time, solvent concentration, aqueous/organic phase ratio, and reaction temperature, have been studied in terms of the maximum P₂O₅ extraction efficiency and the minimum impurities extraction efficiency. The obtained loaded organic solvent was subjected to the stripping stage using double-distilled water. The outlet stripping liquor was concentrated by evaporation up to 62% P₂O₅.     

磷精矿杂质指数与磷铵总养分的关系

讨论磷精矿中主要杂质进入产品酸的状况,简要介绍黄麦岭磷酸、磷铵工艺,并以黄麦岭磷精矿及工艺、产品质量数据为基础,总结出磷精矿杂质指数与磷铵总养分的关系;浓磷酸密度与磷铵总养分的关系,可为磷酸、磷铵工艺及产品质量控制提供预测。     

Evaluation of problematic indigenous phosphate deposits for phosphoric acid manufacture

To examine the possible utilization of indigenous phosphate reserves, bench scale studies were under-taken to assess their suitability for phosphoric acid manufacture.It was found out that in spite of few problems, the Silicious phosphate reserves of 2–3 million tons could be utilized for phosphoric acid manufacture, because low sulphuric acid consumption 2.52 ton acid/ton P₂O₅ and better P₂O₅ recovery yield (94.71) was achieved. The dolomitic phosphate reserves of 4–5 million tons (having 5–6% MgO) remained problematic, giving low P₂O₅ recovery yield (89.25) and higher sulphuric acid consumption 4.08 tons acid/ton P₂O₅.Product acid from the dolomitic reserves upon concentration became paste like at 36–38% P₂O₅ and therefore, these indigenous dolomitic phosphate reserves could not be utilized for the production of phosphoric acid.     

TVA pilot-plant phosphate flotation conditioning study

TVA conducted an extensive test program in its 1,000-pound-per-hour phosphate beneficiation pilot plant to study the effects of major variables in the conditioning step prior to phosphate flotation. Florida rock fine flotation feeds of 14 and 18 bone phosphate of lime (BPL) from the Bone Valley formation were tested.During Phase I for each flotation feed, a full factorial design was used for the test series to evaluate the effects of agitation, retention time, and solids content on P₂O₅ recovery and product grade. In Phase II, a qualitative test study was completed of several additional variables including agitator flow direction, slurry feed position, use of baffles or no baffles, fuel oil to fatty acid ratio, and reagent dosage. The results of both test series were statistically analyzed and compared with those obtained from batch, laboratory-scale flotation tests of pilot plant conditioned samples. From the pilot-scale results, a mathematical model was developed relating product grade and P₂O₅ recovery to the major process variables.     

A new route for the beneficiation of low grade calcareous phosphate rocks

The bulk of the world's phosphate reserves is located in sedimentary horizons that contain appreciable amounts of carbonate. During beneficiation of phosphate rocks, huge amounts of oversize phosphate rocks are rejected from crushers. This reject also mostly contains low tricalcium phosphate content and high carbonate content. In this work, various experiments have been carried out to reduce the carbonate content by leaching the ground phosphate rock with dilute formic acid solution in order to get marketable and industrially acceptable phosphate grades. By using this technique, the effect of formic acid concentration, reaction time, process temperature and liquid/solid ratio (vol./wt. basis) have been studied. It was found that upon treatment of the ground rock with formic acid, the P₂O₅ percent can be raised by up to 29% corresponding to a reduction of about 69% in the calcium carbonate content of the samples, depending on the reaction conditions as well as nature and size of the raw phosphate particles used for analysis.     

Process for recovery of phosphorus and aluminum compounds from Maranhão aluminum phosphate rock

This paper presents a study on an alkaline wet-process for the solubilization of aluminum phosphate ore from the state of Maranhão, Brazil. By processing a sample from Trauíra Island containing 27% P₂O₅ and 29% Al₂O₃, extraction efficiencies of about 70% for P₂O₅ and 94% for Al₂O₃ could be achieved. Phosphorus was recovered as sodium phosphate and calcium phosphate while aluminum was recovered as sodium aluminate solution by-product.     

Patent abstracts

Chrysotile asbestos (Grade 7RF66) sorbs phosphate ion from aqueous solution of phosphoric acid, basic disodium phosphate, ammonium dibasic phosphate, sodium pyrophosphate, or sodium tripolyphosphate. The amount sorbed varies from 0·2 to 2·5% P₂O₅. The fiber treated with ammonium dibasic phosphate has appreciably low toxicity that is comparable to chrysophosphate obtained by the reaction of chrysotile asbestos with POCl₃ gas, provided the latter is washed thoroughly with water to remove watersoluble ingredients.     

磷酸高效分解磷矿实验研究

为改进湿法磷酸生产工艺,提高副产石膏的品质,减少湿法磷酸固体副产物磷石膏堆存产生的经济和环保压力,进行了磷酸分解磷矿制磷酸的实验研究。采用贵州某磷矿为主要原料,研究了湿法磷酸预分解磷矿的反应条件。通过单因素实验确定了湿法磷酸分解磷矿最优反应条件：反应温度为75 ℃,磷酸与磷矿的质量比（液固比）为9,反应时间为3 h,磷酸质量分数为30%（以五氧化二磷计）。在此条件下,磷矿的分解率为98.62%。     

酸热烧结法制备饲料级脱氟磷酸钙的研究

以四川清平磷矿为原料,用酸热烧结法制备饲料级脱氟磷酸钙,研究了磷矿脱氟的主要影响因素。实验结果表明：磷酸配比、烧结温度以及烧结时间对脱氟反应有显著影响,而磷酸浓度对脱氟反应的影响不明显。实验得出的最佳工艺条件为：磷酸配比控制在27％～30％,烧结温度1180-1230℃,烧结时间120min,磷酸w（P2O5）45％左右。在此条件下可制得质量合格的饲料级脱氟磷酸钙产品。     

Nitric acid acidulation of phosphate rock and pyrolysis of acidulate to produce phosphatic and nitrogen fertilizers

A modified method for producing a range of dicalcium phosphate containing phosphatic fertilizers and aqueous calcium nitrate is discussed. The process consists of reacting phosphate rock with nitric acid followed by pyrolysis of the resulting acidulate to produce dicalcium phosphate (CaHPO₄) and to liberate approximately one-half of the initially consumed nitric acid. Recycling of the liberated nitric acid allows production of available phosphate at approximately one-half the acid equivalents consumption normally utilized in wet-process acid production. The calcium nitrate by-product is separated from the phosphatic component of the pyrolyzate by dissolution in water followed by filtration. The initial HNO₃ : CaO acidulation ratio governs the available P₂O₅ content of the phosphatic fertilizer, which may be as high as 47%. The aqueous calcium nitrate stream may be processed to produce a variety of solid or fluid nitrogen fertilizer products. No throwaway by-products (other than possibly siliceous gangue) are produced. Estimates are given for raw materials needed and energy cost.     

工业磷酸分解磷矿影响因素及副产物性质研究

为改进湿法磷酸生产工艺,提高副产磷石膏的品质,减少湿法磷酸固体副产物堆存产生的经济和环境压力,进行了工业磷酸分解磷矿制磷酸的实验,同时对固体副产物的性质进行了分析。工业磷酸分解磷矿制磷酸的工艺分为两步：第一步,工业磷酸与磷矿反应,得到磷酸二氢钙溶液和酸不溶渣;第二步,浓硫酸与磷酸二氢钙溶液反应,得到磷酸溶液和高纯石膏。采用单因素实验考察了酸比（工业磷酸用量与理论磷酸用量的物质的量的比值）、磷矿粒度、反应温度和反应时间对磷矿中磷浸出率的影响。得到磷矿酸解适宜工艺条件：酸比为6.8,磨矿细度为小于0.074 mm粒级占60%,反应温度为50 ℃,反应时间为2.5 h。在此条件下,磷矿中磷的浸出率可达87.69%。磷矿酸解制磷酸产生的固体副产物中石膏占35.32%（质量分数）、酸不溶渣占64.68%（质量分数）。制备的高纯石膏的纯度为95.80%,工业利用价值较高,有利于提高湿法磷酸固体副产物的利用率。     

Nitric acid treated phosphate fertilizer from Eppawala apatite in Sri Lanka

A method is described for the production of phosphate fertilizer from a high quality fraction of the apatite ore at Eppawala in Sri Lanka.Apatite is acidulated with nitric acid (70%) at approximately the stoichiometric level needed to generate dicalcium phosphate. The reaction product when mixed with ground ammonium sulphate yields a dry nonhydroscopic solid containing almost all phosphorus in the available form (i.e. ~ 80% water soluble and ~ 90%, 2% citric acid soluble). The product can be stored in polythene or gunny bags. Reversion is negligible, as demonstrated by a decrease in water soluble P₂O₅ of less than 1% after 6 months' storage.     

尼日利亚某中品位磷矿二水法制磷酸实验研究

磷矿湿法加工制取磷酸新装置建设需要根据磷矿性质（化学组成、物相等）的不同进行独立设计,通过在实验室模拟湿法磷酸工业化流程（反应、结晶、过滤）,得到特定磷矿下的制酸工艺参数,可以减少工业化装置试验成本。根据业主委托,采用传统二水法磷矿制酸工艺对尼日利亚某中品位磷矿进行了实验室制酸模拟实验,利用单因素法研究了湿法磷酸工艺主要控制参数包括游离三氧化硫浓度、磷酸浓度、停留时间、温度和料浆液固比对磷矿制酸工艺的影响,得到最适宜的工艺条件：游离三氧化硫质量浓度为25~30 g/L,磷酸纯度（以五氧化二磷质量分数计）为22%~23%,停留时间为4 h,反应温度为75~78 ℃,料浆液固质量比为2.5∶1。在上述条件下,磷矿中五氧化二磷转化率≥93%,五氧化二磷回收率约为90%,料浆的过滤强度（以五氧化二磷计）为8.1 t/（d·m²）。后期跟踪发现,实验室制酸模拟装置得到的实验结果与后期工业化试验结果基本一致。     

Single superphosphate manufacture from Kakul phosphate rock

Single superphosphate of 20% available P₂O₅ is being manufactured at Lyallpur Chemicals & Fertilizers Ltd., Faisalabad, using Jordan phosphate rock of 70–72 BPL with P₂O₅:Acid weight ratio of 1:1.79.Kakul phosphate rock (average P₂O₅ 28%, 61.18% BPL) is siliceous, therefore hard and slowly reactive. Laboratory as well as plant trials with 200 BSS mesh fine rock and 1:1.71 P₂O₅/acid weight ratio formed thinner slurries in the mixer as compared to Jordan rock slurry and could be hardly retained in the Den, necessitating further processing compared to Jordan rock. Provision for a suitable mixing and Denning system is needed to handle the thinner slurry in all eventualities during plant scale production of SSP.Furthermore, 100 mesh BSS Kakul rock naturally gives a thinner slurry in the mixer than 200 mesh BSS Kakul rock having a greater tendency towards flowing out of the den without processing, therefore similarly necessitating other special arrangements in the mixer and Den as the usual baffle plate and reverse paddles in the mixer would not much improve the situation.     

The potential of Hazara phosphates for phosphoric acid manufacture

The phosphate reserves in Pakistan are small. The largest ore body (Lagarban area) of Hazara Administrative Division located in the North East of the country has 3.25 (measured) and 6.71 (inferred) million tons phosphates rock of silicious and dolomitic nature with 25.8% average P₂O₅ contents besides high impurities of R₂O₃ (3.3%) and MgO (up to 6%).The deposits are not beneficiable by dry and wet screening due to significant phosphate losses which take place. Phosphate flotation recoveries are also low. Heavy intensity magnetic separation removes iron after the removal of dust from classified fraction. Acid leaching is efficient for removing MgO (up to 84%) with low P₂O₅ losses. However, removal of iron and MgO by these methods is not considered feasible on economic grounds.Laboratories and pilot plant processing trials showed that phosphoric acid of 23–25% P₂O₅ can be manufactured from Lagarban rock. As most of the impurities of the rock Fe₂O₃, Al₂O₃, MgO and part of SiO₂ are washed down during processing the resulting product acid is of poor quality with high viscosity.Triplephosphates prepared from this acid are hygroscopic and have low P₂O₅ availability (86%).To overcome the problem of these objectionable impurities in the product acid, removal of these impurities during the processing of phosphoric acid is required, i.e. aggolomeration with gypsum crystals-Pembrook pocess, Occidental process.     

湿热磷化工耦合绿色生产饲料磷酸盐技术

介绍了以磷矿、湿法磷酸和黄磷尾气耦合生产饲料级磷酸二氢钙（MCP）、磷酸一二钙（MDCP）、磷酸氢钙（DCP）和磷酸三钙（DFP）以及专用的磷酸一二三钙（MDTCP）等饲料磷酸盐的绿色可持续发展的生产方法。该方法经济地利用了磷矿中的钙资源,节约了传统方法生产饲料磷酸盐需要开采原生石灰石的资源;同时,不仅经济地开拓了黄磷尾气的利用途径、消灭了“天灯”、节约了能源,又将生产饲料磷酸盐的磷矿中的氟资源全部回收;创新耦合生产带来了磷矿中的磷、钙、氟的全资源利用。