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WO2024201513A1 - Production de phosphates au moyen d'une roche de phosphate - Google Patents

Production de phosphates au moyen d'une roche de phosphate Download PDF

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Publication number
WO2024201513A1
WO2024201513A1 PCT/IN2024/050316 IN2024050316W WO2024201513A1 WO 2024201513 A1 WO2024201513 A1 WO 2024201513A1 IN 2024050316 W IN2024050316 W IN 2024050316W WO 2024201513 A1 WO2024201513 A1 WO 2024201513A1
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phosphate
solution
dcp
calcium
source
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Visweswara Rao Abburi
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/32—Phosphates of magnesium, calcium, strontium, or barium
    • C01B25/324—Preparation from a reaction solution obtained by acidifying with an acid other than orthophosphoric acid
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/32—Phosphates of magnesium, calcium, strontium, or barium
    • C01B25/322—Preparation by neutralisation of orthophosphoric acid

Definitions

  • the present disclosure relates to a process for the production of clean phosphate products.
  • Phosphate is a finite source in the universe and a building block for other compounds. Phosphate products are used to provide phosphorus nutriment to the soil and sustain agricultural yields or for cattle.
  • phosphate It takes hundreds of millions of years for phosphate to form in the earth.
  • the chemical and physical characteristics of phosphate ore can vary widely depending on the geological history of the ore.
  • Most of the ores of phosphate contain phosphate in the form of apatite, and in a variety of compositions such as fluorapatite, hydroxyapatite, Francolite, etc. where phosphorus is under the form of tricalcium phosphate Ca3(PC>4)2
  • Phosphates are relatively abundant on the earth however the economically available resource tends to decline over the last decades with a decrease of the P2O5 concentration in the ore and concomitant increase in the level of impurities.
  • apatite ore also had to be processed through beneficiation to recover P2O5 in an enriched form and limit the impurities to meet the requirement for downstream processing and products quality.
  • the beneficiated ore is generally referred as concentrate.
  • Phosphate concentrates generally contains 28-35%, and plants are generally designed to process a specific quality and grade of concentrate.
  • the exports contain concentrates with about 30%, and anything less than this, is designated to be of low grade.
  • Phosphate rocks by their existence, contain large number of impurities such as silica, calcium carbonate in addition to the calcium bound with primary apatite, Fe, Al, F, Mg and a host of other impurities such as Cd, and radioactive elements.
  • Silica is a dead load and inert and does not cause process related problems to a large extent but has other implications such as requirement of larger machinery, higher throughputs in all systems, wear out etc. Excessive silica causes lower availability of P2O5, causing the grad to be lower, but does not cause problems associated with impurities.
  • Presence of calcium generally as a carbonate, results in larger machinery, higher acid consumption, foaming, and other related problems.
  • Iron is invariably present in the ores and is removed to some extent during the beneficiation process.
  • the iron present in the feed concentrate is almost entirely present in the acid phase during the processing. This impurity affects the quality of the acid being produced.
  • Aluminum is another impurity that affects the quality of the acid when present in the phosphate being used, as a substantial quantity of aluminum enters the acid phase. Fluorine is also present, invariably in almost all phosphates. However, it is distributed between the acid and gypsum, and is substantially recovered during the concentration of the acid, and also from the emissions.
  • Magnesium is yet another impurity that must be removed prior to the use of the phosphate in the production of the acid, as it is difficult to remove it subsequently.
  • the purity of the resource depends on the presence of the aforementioned elements, namely, Fe, Al and Mg. These elements exist in the form of oxides, namely, Fe2C>3, AI2O3 which are collectively referred to as R2O3, and have a major impact on the purity of the acid.
  • Another ratio called Minor Element Ratio, (MER) is also used, which is defined as a ratio of (R2O3 + MgO)/P2O5. It is recommended to use phosphate rock with MER ⁇ 10-12% for the production of ammonium phosphate fertilizers, or more precisely, to limit the MER in the acid to 8% for diammonium phosphate (DAP) production, 10% for monoammonium phosphate (MAP) and slightly above for superphosphates.
  • DAP diammonium phosphate
  • MAP monoammonium phosphate
  • the beneficiation is done to control the presence of R2O3 in beneficiated ore which is the major reason for rendering a vast P2O5 resource emerging out
  • aspects of the disclosure may include an economical process for the recovery of phosphate products, and especially high grade phosphate products from phosphate sources such as reject material containing high levels of R2O3 or high MER, and conserve valuable phosphate resources.
  • phosphate products include high grade phosphate (HGP), mono calcium phosphate (MCP), dicalcium phosphate (DCP), mono dicalcium phosphate (MDCP), double superphosphate (DSP), triple superphosphate (TSP), and nitro phosphates.
  • Another aspect of the disclosure is to provide a process for the production of phosphate products either as a solid or as phosphoric acid with MER or R2O3/P2O5 less than 8%.
  • Another aspect of the disclosure is to provide a process for the production of high grade phosphate products, that have low fluorine content.
  • Yet another aspect of the disclosure is to provide an integrated process for the production of high grade phosphate products.
  • Still yet another aspect of the disclosure is to provide a process for the production of high grade phosphate products, wherein the purity is independent of the concentration of the phosphate solution.
  • a further aspect of the disclosure is to provide a process for the production of high grade phosphate products, that can utilize vast resources of phosphate-containing waste or low-grade phosphate sources.
  • Yet another aspect of the disclosure is to provide a process for the production of high grade phosphate products that can be utilized for the production of valuable end products such as fertilizers, feed additives, downstream products, etc.
  • Figure 1 shows the flow chart of the steps involved in the process of the present disclosure
  • Figure 2 shows the MER values of solutions of the sample prepared in Example 5 in accordance with the examples of the present disclosure
  • Figure 3 shows the MER values under different conditions of the sample prepared in Example 6 in accordance with the examples of the present disclosure.
  • Figure 4 shows the percentage of P2O5 losses observed in the sample prepared in Example 7 in accordance with the examples of the present disclosure.
  • aspects of the present disclosure may provide, among other things, a process for the production of high grade phosphate products from a phosphate source such as phosphate rock or low grade mine slimes or rejects.
  • said process may comprise treatment of a phosphate source, with dilute sulfuric acid or sulfuric acid along with water or recycled solution in a continuous reactor, wherein the solution comprises calcium ion, so as to restrict unacceptable levels of impurities from entering into the solution, recovering the solution (A) in adequate strength to directly use as phosphoric acid solution, or recover further by filtration, and treat the solution thus obtained with a source of calcium so as to precipitate out calcium phosphate that is rich in phosphate and low on impurities.
  • Said process of the present disclosure also comprises purification of the solution (A) to produce a solution of higher purity by adding a source of calcium, and precipitating impurities along with fluoride salts and some phosphates which are recycled to the first step involving the reaction of rock phosphate with dilute sulfuric acid.
  • DCP feed grade dicalcium phosphate
  • Said process of the present disclosure also comprises acidulation of the feed grade dicalcium phosphate (DCP) with sulfuric acid for production of pure fluorine-free phosphoric acid and gypsum, which are separated, followed by mixing the solution with dicalcium phosphate to produce feed grade mono calcium phosphate (MCP).
  • DCP dicalcium phosphate
  • MCP mono calcium phosphate
  • One or more examples of the present disclosure provide a simple process for the production of high grade phosphate products from phosphate rock.
  • the various terminologies and aspects generally used or used in the present disclosure in particular are presented here for clarity.
  • R2O3 is the sum of the oxides of iron, aluminum, and magnesium in the form of their respective oxides Fe2C>3 and AI2O3.
  • MER is the ratio of sum of the oxides stated above to the P2O5 content in any product or source. The MER is considered to be acceptable if it is lower than 8%.
  • a source of phosphate is considered to be low grade if it contains less than 26% of P2O5. It must be understood that this definition of low grade is dynamic as the reserves of high grades above 32% are depleted.
  • a pure product of calcium phosphate can be a solution of phosphate of a concentration of upto 24%, or a solid HGP is precipitated out of the solution through neutralization, which in turn is used to produce several other products such as DSP, TSP, phosphoric acid, or nitro phosphate. Further purification of the pure calcium phosphate obtained in the solution may be used to produce DCP, wherein impurities are precipitated out first, followed by precipitation of high purity DCP feed grade from the filtered solution.
  • the obtained solution comprises HGP and calcium phosphate that are of high purity with MER of less than 8%, and DCP containing a ratio of P to F of more than 180 or more than 250.
  • the acid required to produce phosphoric acid though a dihydrate wet process phosphoric acid production route is 1.78 times the calcium source content.
  • the process comprises production of a phosphate solution with low impurities, from which HGP can be precipitated or can be further purified to produce DCP.
  • Said high grade phosphate (HGP) can be used for the preparation of phosphate products such as double super phosphate (DSP), triple super phosphate (TSP), and nitro phosphates.
  • DSP double super phosphate
  • TSP triple super phosphate
  • nitro phosphates Said DCP can be further processed and filtered to obtain feed grade DCP, which can further be treated to obtain mono calcium phosphate or mono dicalcium phosphate (MDCP).
  • the process for the recovery of high grade phosphate products from a phosphate source comprises of (a) reacting a phosphate source with sulfuric acid under controlled conditions to obtain first a slurry comprising impurities and solution of phosphate containing a MER of 0.5% to 8%; (b) filtering the slurry obtained in (a) to separate high grade phosphoric acid solution (A) comprising 1% to 24% P2O5 and MER of 0.5% to 8%, and filter cake; and (c) neutralizing the phosphate solution (A) with a source of calcium to obtain highgrade phosphate (HGP) with MER 0.5% to 8%, and feed grade dicalcium phosphate (DCP) with MER 0.5% to 8%.
  • HGP highgrade phosphate
  • DCP dicalcium phosphate
  • High-grade phosphate (HGP) with MER 0.5% to 8% is obtained by neutralizing the phosphate solution (A) to a pH of 4.5 to 6.5 with a source of calcium.
  • Feed grade dicalcium phosphate (DCP) is obtained by neutralizing the phosphate solution (A) to a pH of 2.2 to 3.4 with a source of calcium, defluorinating to obtain a solution of dicalcium phosphate dihydrate (DCP DH) and a cake comprising impurities including fluorides, aluminum phosphate, and iron phosphate, neutralizing the solution of dicalcium phosphate to a pH of 5.5 to 6 to precipitate out DCP, and filtering the precipitated DCP.
  • DCP dicalcium phosphate
  • HGP obtained in step (c) is treated with 20-40% sulfuric acid to obtain double super phosphate (DSP), or treated with 25-40% phosphoric acid to produce triple super phosphate (TSP).
  • DCP obtained in step (c) is treated with sulfuric acid to obtain high grade phosphoric acid (B) comprising less than 0.06% of fluoride content.
  • the phosphoric acid solution (B) is treated with DCP to obtain mono calcium phosphate (MCP) or mono dicalcium phosphate (MDCP).
  • the production of high grade phosphate comprises treating phosphate resource with sulfuric acid under controlled conditions of temperature, degree of acidulation, and any aid added per unit of phosphate source, wherein the R2O3/P2O5 in said solution is reduced to as low as 0.5 to 8%.
  • said slurry is filtered, and the solution is subjected to further treatment.
  • Said solution may contain 2.5% to 24% P2O5, preferably 2.5% to 12% P2O5, more preferably 4% to 6%, and MER of 0.5% to 8%, and this solution itself could be a value-added product.
  • the dilution does not affect downstream recovery or result in any effluent.
  • Said solution may subsequently be neutralized with a calcium source, to precipitate out high grade phosphate (HGP) with MER 0.5% to 8%.
  • dicalcium phosphate is produced from the phosphoric acid solution (A), wherein said solution contains high fluorine content which is to be removed to render the solution suitable to obtain an acceptable Feed grade DCP.
  • the feed grade product should have a P/F of more than 180, preferably 250-300.
  • the pH of the solution is raised to 2.2 to 3.4 and defluorinated to obtain a solution of DCP with MER 0.5% to 8%, and precipitates out fluorides predominantly as calcium fluoride along with other phosphates such as iron phosphate, aluminum phosphate, and calcium phosphate.
  • feed grade mono calcium phosphate MCP - anhydrous and mono hydrate
  • MDCP mono dicalcium phosphate
  • DCP produced is acidulated with sulfuric acid in a conventional phosphoric acid producing reactor while permitting retention of calcium in the solution instead of using additional sulfuric acid. This saves on sulfuric acid, and improves the product quality.
  • phosphoric acid is pure enough to produce MCP.
  • Said high grade phosphoric acid solution comprising less than 0.006% of fluoride content is further treated with feed grade DCP to obtain mono calcium phosphate (MCP) or mono dicalcium phosphate (MDCP).
  • MCP mono calcium phosphate
  • MDCP mono dicalcium phosphate
  • an appropriate amount of acid can be used by maintaining sufficient calcium and PO 4 .
  • concentration of the acid used is increased to 40% to 52%, and then pugged in a suitable machine with dry DCP.
  • double super phosphate is prepared from HGP obtained in accordance with the one or more examples of the present disclosure. While single super phosphates comprisel6 to 19% P2O5, it is possible to produce a much higher grade super phosphate using HGP obtained in accordance with the one or more examples of the present disclosure. Said HGP is treated with sulfuric acid with a dilution of 20% to 40%, and a wet material is obtained. Unlike single super phosphate, the wet material dries fast and cures well in a short period. This can be directly granulated in the wet condition to obtain double super phosphate (DSP) of high grade.
  • DSP double super phosphate
  • triple super phosphate is prepared from HGP obtained in accordance with the one or more examples of the present disclosure.
  • This process is similar to that of the preparation of DSP from HGP of the present disclosure.
  • the phosphoric acid with a dilution of 25% to 40% is used to treat HGP.
  • the acid required is 15% to 25% lower compared to traditional TSP process which uses rock phosphate as the solid input.
  • rock phosphate the mol ratio of Ca:PO4is 3:2
  • HGP the mol ratio of Ca:PO4 is 1: 1.
  • much less calcium has to be converted to mono calcium phosphate in the production of TSP in accordance with the one or more examples of the present disclosure.
  • nitro phosphates are prepared from HGP obtained in accordance with the one or more examples of the present disclosure. Said HGP can also be treated with nitric acid to obtain nitro phosphates.
  • high calcium content with respect to P2O5 gives a product that is low in phosphate, as the ratio of Cao/PO4 is generally in excess of 1.6, and goes upto 2 for certain phosphates.
  • the use of HGP gives an excellent product as the Cao/PO4 is quite low. Said process offers the benefits of requirement of less nitric acid, and production of a higher grade product.
  • the process for the production of high-purity phosphate products comprises feeding into a reactor 10, a phosphate source such as low-grade phosphate source, reject material, ores, ore rejects, slime or any other source of phosphate of mineral origin.
  • a phosphate source such as low-grade phosphate source, reject material, ores, ore rejects, slime or any other source of phosphate of mineral origin.
  • Said process in accordance with the one or more examples of the present disclosure may be carried out in one or a plurality of reactors, say 8 reactors, preferably 4 reactors, which may comprise single compartment or multiple compartments, with each compartment or reactor being equipped with an agitator.
  • Said phosphate source can be either low grade or low grade with impurities containing high MER of upto or more than 30%, and P2O5 of 5% or more.
  • Said reactor 10 is continuously fed with proportionate quantity of sulfuric acid, through stream 102.
  • the proportionate quantity is the pre-determined acid per unit weight of rock phosphate which is decided through an optimization test.
  • the percentage of acid with respect to rock feed ranges between 70% and 95% acidulation.
  • the size of said reactor 10 and agitation system is based on optimized residence time arrived at during optimization testing.
  • the slurry obtained above is overflown to a filter 11 , either directly or through a filtration tank, not shown in the figure.
  • the filtrate is the phosphoric acid solution containing a MER of 0.1 - 8%, and 6 to 12% P2O5, preferably 6 to 24%.
  • the filter cake of gypsum obtained from filter 11 is subjected to washing so as to recover as much phosphate as possible.
  • the solution obtained from said washing can be mixed with the primary filtrate taken in tank 12, or recycled by reintroducing it into said reactor 10 if higher concentration of filtrate solution from filter 11 is desired.
  • the solution obtained in tank 12 is the first filtrate, and the product is obtained in a single reaction using a single acid. During said reaction, no effort has been made to heat the slurry, and the temperature (measured at overflow) of the slurry is generally maintained as close to the fixed temperature ranging between 20 °C to 60 °C.
  • said solution in tank 12 could be considered as a product by itself predominantly as a phosphate comprising phosphoric acid of a concentration of upto 24%.
  • the solution from said tank 12 is then subjected to neutralization with a source of calcium, such as but not limited to calcium carbonate, powder of mineral carbonate, precipitated calcium oxide, calcium hydroxide, hydrated lime, or combinations thereof, from stream 104, preferably in the form of a slurry with a consistency of a solid of 2 to 6 times of diluent, which could be water or any of the final effluent solutions obtained in the process such as a stream from any of the filters, namely, filters 14 or 19.
  • a source of calcium such as but not limited to calcium carbonate, powder of mineral carbonate, precipitated calcium oxide, calcium hydroxide, hydrated lime, or combinations thereof.
  • HGP cake which is a calcium phosphate product, possessing a definite purity of MER less than 8%.
  • the fluoride content of said product HGP is normally high and has very low P/F value.
  • the solution from the process from the clean phosphate storage 17 is further processed in a neutralizer 18, wherein the solution from the storage 17 and source of calcium from tank 13, neutralize the pH to 2.2 to 3.4 and defluorinated to obtain a slurry of dicalcium phosphate dihydrate (DCP DH) and a solution or effluent containing traces of P2O5.
  • DCP DH dicalcium phosphate dihydrate
  • the above filtration is carried out in filter 19, and DCP DH is separated out.
  • DCP DH is separated out.
  • obtained product is dried for use as feed grade DCP from stream 106, and comprises phosphorous of not less than 18%, and a P/F value of more than 180 to 200.
  • the dried DCP obtained from stream 107 can be directly used as the final product - DCP feed grade.
  • DCP obtained as slurry can further be used for the production of high grade mono calcium phosphate by first producing a fluoride-free phosphoric acid.
  • Said DCP slurry is introduced continuously into reactor 20, either from stream 106 or directly as a wet cake, and it can also be continuously fed with concentrated sulfuric acid in a ratio of 1.02 mole of H2SO4 calculated on the basis of 100% for every mol of DCP estimated on dry basis.
  • Said reactor 20 is operated by recycling wash obtained from filter 21, preferably a vacuum filter but not limited to using a vacuum filter, or any form of apparatus for solid liquid separation.
  • Said reactor 20 is equipped with a suitable agitator, and the reactor slurry is maintained at a temperature range of 75°C to 85 °C, and comprising a solid content not exceeding 30% by weight on slurry weight basis, preferably not exceeding 25% or 20%.
  • This consistency of the slurry is maintained by recycling all the wash water obtained through filtration from filter 21, and if required, from wash collection tank 50.
  • the cake obtained from filter 21 is gypsum of high purity and a dihydrate form which can be used to produce valuable downstream products such as Plaster of Paris, from stream 201.
  • the phosphoric acid obtained from filter 21 is stored in tank 22, which has a P/F of more than 200, and approximately 30-32% P2Os.
  • the phosphoric acid obtained therein is mixed with DCP from stream 106 along with phosphoric acid from tank 22 in an apparatus such as a paddle mill.
  • Pug mill, ribbon blender, or such other equipment 23 is used for thorough mixing so as to produce a wet or semi-solid product of calcium phosphate, which can be mono calcium phosphate, mono dicalcium phosphate, or a product comprising a ratio of MCP to DCP.
  • a dryer 24 to produce a product that can be acceptable in the market.
  • the acid from tank 22 can be further concentrated by methods known in the prior art or used in the industry, such as a concentrator of phosphoric acid, and an acid of 48% can be used to obtain a final product of MCP, MCP-DCP, or MDCP that is fairly dry, which could be crushed and bagged for dispatch.
  • HGP cake can also be recycled and subjected to further processing in a DSP mixer 30 or TSP mixer 40, to obtain phosphate products.
  • the HGP obtained in stream 105 is admitted into a paddle type mixer which is generally used in the production of super phosphates along with sulfuric acid of concentration between 20% and 40%, and mixed in a mixer 30.
  • the wet product obtained is granulated in a granulator 31 , to produce granular double super phosphate (DSP) comprising high P2O5 compared to single super phosphate.
  • DSP granular double super phosphate
  • HGP obtained through the process of the present disclosure is treated with merchant grade phosphoric acid obtained through stream 301 into a mixer 40, and the obtained wet product is granulated in a granulator41, producing a high-quality triple super phosphate (TSP).
  • TSP triple super phosphate
  • the primary advantage of the process of the present disclosure in accordance with the various examples to produce DSP and TSP from HGP, is that the process needs less quantity of the acids as Cao/PO4 of the input HGP is less than 1, or about 0.8 to 1.
  • the HGP obtained through the process of the present disclosure can also be used as feedstock for the manufacture of high-quality nitro phosphates, by treating HGPwith adequate quantity of nitric acid in required concentration as per known industry techniques.
  • HGP can be used for the production of high-quality merchant grade phosphoric acid using less amount of sulfuric acid compared to phosphate rock concentrate, as Cao/PO4 ratio is much less compared to the commercially available phosphate rock concentrate.
  • One of the novel features of the process is that the intermediate cake obtained in the defluorinator from filter 16 can be put to multiple uses to produce valuable byproducts such as hydrogen fluoride, by treating the product obtained in filter 16 with sulfuric acid. While gaseous HF can be collected, the solid residue contains valuable phosphate that can be recycled by reintroduction into the process, or into products such as TSP, DSP, etc., or mixed with HGP
  • the acid used in the process in accordance with one or more examples of the present disclosure is 1.06 to 1.78 times of the calcium source content, and the temperature is maintained in the range of 20 - 60 °C, so as to ensure control of R2O3 and the MER to a range of 0.5% to 8%.
  • reactors used in this disclosure comprise suitable agitator units, pumps, and other apparatus required to complete such unit operations.
  • the reactor system can be a single reactor or a plurality of reactors, say 8 reactors, preferably 4 reactors, of any shape such as circular, elliptical or rectangular cross-section, with single compartment or multiple compartments in the rector or reactors, such reactors operating in series or parallel.
  • the advantages achieved by the present disclosure hitherto not possible by any of the processes in the prior art, include recovery of valuable phosphates from sources containing high MER, minimal losses even during defluorination step for the production of DCP by utilizing the intermediate byproduct to even recover fluorine and also due to reuse of the impure filtered cake, operation of the reactors at temperatures such that there are negligible fluorine emissions, use of only one acid during the process, absence of generation of liquid effluents, and high cost-effectiveness of material of construction (MOC) of equipment as operation temperatures are very low.
  • MOC material of construction
  • the source of phosphate is low-grade impure phosphate source comprising MER higher than 8%, and generally upto 30% or above.
  • the typical analysis is reported below in Table 1. Table 1
  • a reaction between phosphate and sulfuric acid was carried out in a manner as conducted in Example 1, and a phosphate solution was obtained. Said solution was treated with lime to achieve a pH of 2.85. The solids produced were separated, and the solution was then neutralized with lime to a pH of 6.2.DCP was precipitated out which comprised 0.092% fluorine and 39.2% P2O5, with fluorine well within acceptable limits.
  • DSP Double super phosphate
  • TSP Triple super phosphate
  • DCP obtained in EXAMPLE 2 was treated with 27 gms of sulfuric acid per 100 gms of DCP on dry basis and the sulfuric acid was diluted to 34%.
  • the resultant product showed 29.5% water soluble P2O5, 31% neutral ammonium citrate soluble P2O5, and 2.2% free acid P2O5, thereby indicating a high grade double super phosphate (DSP).
  • DCP obtained in EXAMPLE 2 was treated with 47 gms of phosphoric acid calculated based on 100% P2O5 solution of 45% concentration, thoroughly mixed, and allowed to cure.
  • the product obtained after 48 hours comprised 54.6% total P2O5, 48.4% water soluble P2O5, and 2.8% free acid phosphoric acid. This indicates the high-quality Triple super phosphate (TSP) that can be obtained through this process.
  • TSP Triple super phosphate
  • Phosphate from Sample 2 of Table I was treated with an acidulation of 60%, 70%, 80%, and 90%, with addition of 400 gms of water per 100 gms of rock phosphate used, and the MER of the solutions were measured, and presented in Figure 2.
  • MER is dependent on the degree of acidulation.
  • Example 5 The cake obtained from Example 5 was subjected to assessment of recovery efficacy with respect to sulfuric acid used. This was done by assessing the residual insoluble P2O5 after thorough washing to remove soluble P2O5, estimating the losses based on the weight of the input rock, the content of P2O5 in said rock, the dry weight of the cake, and corresponding P2O5 values. The percent losses of P2O5 are presented in Figure 4 which shows the recovery efficiency of P2O5 with respect to the acid used.
  • EXAMPLE 8 Concentration of P2O5 was increased by repeated recycling of the solution obtained from Example 7 back into the reactor, and the MER of the solutions obtained under different concentrations are shown in Table 2. This indicates that the MER is more or less stable, and is not influenced by either recycling or the alteration in the concentration, as long as the other parameters, namely, sulfuric acid and temperature of reaction, are maintained the same.
  • MER is dependent on critical parameters such as degree of acidulation, temperature and residence time. While it is possible to produce a product with acceptable MER by using more amount of acid and lower temperature, or higher temperature and less amount of acid, P2O5 losses are observed.
  • the process of the present disclosure presents a unique method to optimize parameters based on the local conditions. For instance, when the source phosphate is of near zero value and the acid is expensive, compromise can be made on the recovery of P2O5 while using reduced amount of acid.
  • the present disclosure provides a process for the recovery of high grade phosphate products from a phosphate source comprising reacting a phosphate source with sulfuric acid under controlled conditions to obtain a high-grade phosphate (HGP) solution, filtering the slurry obtained from the reaction to separate the phosphoric acid solution (A) and filter cake, neutralizing said phosphate solution (A) to a pH of 4.5 to 6.5 to obtain high-grade phosphate (HGP) with MER of 0.5% to 8%.
  • a calcium source may be used to obtain said high-grade phosphate (HGP) cake.
  • the concentration of the sulfuric acid used in the reaction is in the range of 70% to 95%.
  • Said HGP can be treated with sulfuric acid diluted to 20%-40% to obtain a wet material which is granulated to obtain high grade double super phosphate (DSP).
  • Said HGP can be treated with 25%- 40% phosphoric acid to obtain triple super phosphate (TSP).
  • the initially obtained phosphate solution (A) may be subjected to neutralization with a source of calcium to a pH of 2.2 to 3.4, and defluorinated to obtain a solution of DCP DH which is further subjected to neutralization to a pH of 5.5 to 6, to precipitate feed grade dicalcium phosphate which is filtered and dried.
  • Said feed grade dicalcium phosphate can be subjected to further processing to obtain a product with desired characteristics.
  • Said filter cake is subjected to filtration to remove impurities such as fluorides such as calcium fluoride, and phosphates such as calcium phosphate, aluminum phosphate, and iron phosphate, and said product acid solution comprises 1 % to 24% P2O5.
  • Said product acid solution is neutralized to precipitate dicalcium phosphate (DCP) possessing a minor element ratio (MER) of 0.5% to 8%, and a P/F ratio of 180 to 300.
  • DCP dicalcium phosphate
  • MER minor element ratio
  • the feed grade DCP obtained from the reaction of the phosphate source with sulfuric acid is utilized for the production of various phosphate-based products such as mono calcium phosphate (MCP), dicalcium phosphate (DCP), and mono dicalcium phosphate (MDCP).
  • the feed grade DCP obtained through the process of the present disclosure comprises not less than 18% phosphorous and a P/F value of more than 180, preferably upto 300.
  • the filter cake is reintroduced along with the initially obtained phosphoric acid solution and calcium source, passed through a mixer and dried to obtain mono calcium phosphate (MCP) with a minor element ratio (MER) of less than 8%.
  • MCP mono calcium phosphate
  • MER minor element ratio
  • above obtained DCP can be fed to a mixer, and dried to obtain mono calcium phosphate (MCP) with MER of less than 8%.
  • DCP can be acidulated with sulfuric acid, MCP obtained from phosphoric acid is combined, and the amount of acid is adjusted by increasing the concentration to 40% to 52% to obtain mono dicalcium phosphate (MDCP).
  • MDCP mono dicalcium phosphate
  • the amount of the sulfuric acid used is in the range of 1.06 to 1.78 times the calcium source content, and the temperature is maintained in the range of 20 to 60
  • the process of the present disclosure has the merits of controlling the distribution of R2O3 when the ore source contains high MER, i.e., more than 8%, and upto more than 30% MER; it is a continuous process with residence time that could be as low as 5 minutes or even lower which depends on other factors such as reactor shape, speed of the agitation etc. ; no requirement of any acid other than sulfuric acid; no limitation on the concentration of the available acid and strength of solution of phosphate that could be produced, the only limitation being the physical limitation of recycling large acid quantities while using low grade resource. For instance, while using a low-grade resource of say 8%, enormous recycling has to be done to obtain 20% P2O5 acid.
  • reaction temperature there is no limitation on the lower side of the reaction temperature, but not freezing conditions, and it is preferable to avoid temperatures in excess of 60 °C. Additionally, there is no limitation on the ratio of Ca to PO4 while alleviating the need for the use of any source of calcium irrespective of the amount of CaO and PO4 being present. The step involving the recycling of phosphate solution containing P2O5 has no impact on the process thereby eliminating the need for any other ion from any other acid source to produce pure phosphates having low MER.
  • the process of the present disclosure provides a simple method that can be easily adopted for the production of pure phosphate products either in solution form in sufficient strength for downstream use, or in solid form for use for downstream processing, or as finished products that can be readily sold.
  • This disclosure alleviates the complex process of estimating acid requirement or need for multiple acids thereby simplifying the estimation of the required amount of the acid and temperature for said process.
  • the present disclosure also provides the possibility of optimizing the conditions for optimal economic gain, generates no effluent stream, does not introduce any additional undesirable acid streams into the process, operates at low temperatures, reduced construction costs due to low operation or reaction temperatures, and relatively much fewer gaseous emissions.
  • the process of the present disclosure offers multiple possibilities without restrictions, and ensures production of phosphates, both as liquids and solids, with MER of less than 8% consistently, possibility of recycling solutions thereby minimizing P2O5 losses, and use in a wide range of applications.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Fertilizers (AREA)

Abstract

La présente invention concerne un procédé simple pour la production de phosphates de haute pureté à valeur ajoutée à partir de sources de phosphate de qualité inférieure de sources de phosphate. Ledit procédé comprend le traitement de la source de phosphate avec de l'acide sulfurique dans un réacteur continu, la filtration de la suspension obtenue, le lavage du gâteau filtré pour une collecte supplémentaire de P2O5, suivi du traitement de la solution obtenue avec une source d'oxyde de calcium de façon à précipiter un phosphate de calcium riche en phosphate, et de faibles impuretés. Ceci peut être converti en produits à valeur ajoutée tels que du superphosphate double en le soumettant à un traitement ultérieur en aval par acidulation avec de l'acide sulfurique, un superphosphate triple de haute qualité par traitement avec de l'acide phosphorique de qualité commerciale, en tant qu'alimentation pour la fabrication d'acide phosphorique de qualité commerciale. La solution riche en phosphate ainsi obtenue présente un MER inférieur à 8%, et une concentration en P2O5 allant jusqu'à 24%.
PCT/IN2024/050316 2023-03-29 2024-03-26 Production de phosphates au moyen d'une roche de phosphate Pending WO2024201513A1 (fr)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005087661A1 (fr) * 2004-03-16 2005-09-22 Abburi Visweswara Rao Procede cyclique permettant de produire en continu du phosphate de bicalcium
WO2009016641A1 (fr) * 2007-07-31 2009-02-05 Visweswara Rao Abburi Procédé de fabrication en continu de super phosphate de qualité élevée à l'aide d'une roche phosphatée de faible qualité

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005087661A1 (fr) * 2004-03-16 2005-09-22 Abburi Visweswara Rao Procede cyclique permettant de produire en continu du phosphate de bicalcium
WO2009016641A1 (fr) * 2007-07-31 2009-02-05 Visweswara Rao Abburi Procédé de fabrication en continu de super phosphate de qualité élevée à l'aide d'une roche phosphatée de faible qualité

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