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EP-4739624-A1 - PROCESS FOR PRODUCING A PHOSPHATE CONTAINING PRODUCT FROM A PHOSPHATE SOURCE BY DIGESTION WITH SULPHURIC ACID

EP4739624A1EP 4739624 A1EP4739624 A1EP 4739624A1EP-4739624-A1

Abstract

The present invention concerns a process for producing a phosphate containing product from a phosphate source (P0), the process comprising the following steps: feeding a reactor with a raw material (PC1) comprising at least 10 wt.% P 2 O 5 , and at least 0.7 wt.% CaO, in a digestion step (D1), adding to the raw material (PC1) a digestion liquor (L) comprising H 2 SO 4 to yield a digested suspension (PC2), in a separation step (S1), separating the digested suspension (PC2) into an aqueous phosphate rich solution (P1) a calcium rich first solid cake (C1). Characterized in that, the digestion liquor (L) is added to the at least one raw material (PC1) in amounts such that 0.80 < SO 4 / Ca < 1.7.

Inventors

  • HUMBLET, Gauthier
  • Ninane, Léon

Assignees

  • Prayon

Dates

Publication Date
20260513
Application Date
20240702

Claims (14)

  1. 1. A process for producing a phosphate containing product from a phosphate source (PO), the process comprising: • feeding one or more reactors with at least one raw material (PC1) issued from the phosphate source (PO), the at least one raw material comprising a phosphorus required amount expressed in equivalent P2O5 amounts (= wt.% P2O5) of at least 10 wt.% P2O5, and a required calcium amount expressed in equivalent CaO amounts (= wt.% CaO) of at least 0.7 wt.% CaO, • in a digestion step (D1), adding to the at least one raw material (PC1) in the reactor a digestion liquor (L) for digesting the at least one raw material (PC1) and yielding a digested suspension (PC2), wherein the digestion liquor (L) is an aqueous solution of sulphuric acid (H2SO4) and optionally of one or more mineral acids (HX), wherein a ratio (H+(SA) I H+(L)) x 100% of a mole content of H + issued from the sulphuric acid (= H + (SA)) to a total mole content of H + ions in the digestion liquor (L) (= H + (L)) is comprised between 50 and 100%, • in a separation step (S1), separating the digested suspension (PC2) into, on the one hand, an aqueous phosphate rich solution (P1) comprising phosphate ions and, on the other hand, a first solid phase (C1) containing calcium sulphate and impurities. Characterized in that, the phosphate source (P0) is characterized by a Minor Element Ratio, (MER = (%AhO3 + %MgO + %Fe2Os) / %P2O5), representative of an amount of selected impurities present in the phosphate source (P0), which is equal to at least 0.051 (i.e., MER > 0.051), wherein (%AhO3, %MgO, %Fe2C>3, and %P2C>5 refer to the weight % of the corresponding oxides in the phosphate source (P0)). and in that the digestion liquor (L) is added to the at least one raw material (PC1) in amounts such that a molar ratio (SO4 1 Ca) of the total amount of sulphate ions (SO4) in the digestion liquor (L) to a total amount of Ca atoms (= Ca) present in both digestion liquor (L) and at least one raw material (PC1) is more than 0.80 and is less than 1 .7 (i.e., 0.80 < SO4 / Ca < 1 .7), and is preferably comprised between 0.85 and 0.99 (i.e., 0.85 < SO4 / Ca < 0.99), or between 1 .0 and 1 .6.
  2. 2. Process according to claim 1 , wherein the solid phosphate source (P0) either: • contains calcium in an amount of at least the required calcium amount and thus forms the at least one raw material (PC1) (i.e., PC1 = P0), or • contains less than the required calcium amount, and the at least one raw material (PC1) is formed in a raw material formation step (M0) by addition of a calcium compound (CO) to the phosphate source (P0) to form the at least one raw material (PC1) with the required amounts of calcium (i.e., PC1 c P0 + CO), wherein the calcium compound is chosen among: o calcium oxide, lime derivatives including quick lime, slaked lime, pulverized lime, lime milk, finely ground limestone o calcium carbonate, o calcium phosphates salts (mono di-; tri-), o kaolin, o calcium hydroxide, o calcium sulphate, o calcium fluoride, e a second phosphate source (P02) containing calcium, o recirculated fraction of digested suspension (PC2) or of aqueous phosphate rich solution (P1), o phosphoric acid, or o a mixture thereof.
  3. 3. Process according to claim 1 or 2, wherein the phosphate source (PO) is chosen among one or more of the following origins: • phosphate ores, • beneficiation residues including one or more of phosphate tailing and phosphate slimes, • phosphate salts, • ashes, preferably ashes from one or more of incinerated sewage sludge, bones, manure, • black mass. and wherein the phosphate source (PO) is used alone or admixed with a second phosphate source (P02) of different origin than the phosphate source, wherein the admixing occurs either in the reactor or prior to feeding the phosphate source (PO) into the reactor.
  4. 4. Process according to any one of the preceding claims, wherein the phosphate source (PO) is characterized by the Minor Element Ratio (MER) is equal to at least 0.060 (i.e., MER > 0.060), and is preferably comprised between 0.100 and 1.500 (i.e., 0.100 < MER < 1.500), preferably between 0.140 and 1.500 (i.e., 0.14 < MER < 1.500), preferably between 0.200 and 1.400 preferably between 0.400 and 1.000; preferably between 0.500 and 0.900.
  5. 5. Process according to any one of the preceding claims, wherein the at least one raw material (PC1) comprises phosphorus expressed as P2O5 equivalent in amounts comprised between 10 and 50 wt.% P2O5, preferably between 12 and 45 wt.% P2O5, more preferably between 14 and 40 wt.% P2O5, more preferably between 15 and 38 wt.% P2O5, more preferably between 18 and 35 wt.% P2O5, more preferably between 19 and 30 wt.% P2O5, more preferably between 20 and 27.5 wt.% P2O5, more preferably between 22.5 and 25 wt.% P2O5.
  6. 6. Process according to any one of the preceding claims, wherein a portion of the digested suspension (PC2) and / or a portion of the aqueous phosphate rich solution (P1) is recirculated into the digestion step (D1) as a component of the digestion liquor or as a calcium source, wherein each of the portion of the digested suspension (PC2) and I or of the portion of the aqueous phosphate rich solution (P1) being recirculated is preferably comprised between 1 and 50%, more preferably between 5 and 30%, most preferably between 10 and 20% of the total flow of the corresponding digested suspension (PC2) and I or aqueous phosphate rich solution (P1), respectively.
  7. 7. Process according to any one of the preceding claims, wherein the digestion step (D1) occurs at a temperature lower than 100°C, preferably lower than 90°C, preferably lower than 80°C, more preferably between 25°C and 75°C; more preferably between 30°C and 72°C; more preferably between 60°C and 71 °C; preferably the temperature is 65°C.
  8. 8. Process according to any one of the preceding claims, wherein the digestion step (D1) has a duration lower than 180 min, preferably lower than 90 min, more preferably lower than 60 min, more preferably lower than 50 min or of 45 min + 5 min, , and wherein the duration is preferably at least 5 min, more preferably at least 10 min.
  9. 9. Process according to any one of the preceding claims, wherein a combined concentration of the sulphuric acid and the one or more mineral acids in the digestion liquor (L) is comprised between 3 wt.% and 30 wt.%, preferably between 4 and 25 wt.%; preferably between 5 and 20 wt.%, more preferably between 6 and 15 wt.%; most preferably between 7 and 12 wt.% or is equal to 7 + 2 wt.%.
  10. 10. Process according to any one of the preceding claims, wherein the ratio (H+(SA) I H+(L)) x 100% of the mole content of H + issued from the sulphuric acid (= H + (SA)) to the total amount of H + ions in the digestion liquor (L) (= H + (L)) is comprised between 70 and 99%, preferably between 80 and 98%, more preferably between 85% and 97%, preferably between 90% and 95%. preferably between
  11. 11 . Process according to any one of the preceding claims, wherein the MER of the phosphate source (P0) is lower than 0.250 and wherein in the digestion step (D1), the molar ratio (SC / Ca) is at least 0.810 and less than 0.990; preferably comprised between 0.850 and 0.980; more preferably comprised between 0.890 and 0.950; and is more preferably 0.900.
  12. 12. Process according to any one of the preceding claims 1 to 10, wherein the MER of the phosphate source (P0) is at least 0.250 and wherein in the digestion (D1) step, the molar ratio (SC / Ca) is comprised between 1 .05 and 1 .5; preferably comprised between 1.10 and 1 .20, preferably comprised between 1.15 and 1.17.
  13. 13. Process according to any one of claims 1 to 12, wherein the aqueous phosphate rich solution (P1) is neutralized in a neutralizing step (N1) to form dicalcium phosphate (DCP), wherein the neutralisation step (N1) is performed in presence of a source of calcium (B1) to reach a pH preferably comprised between 3 and 6, wherein the source of calcium (B1) is chosen among, • lime derivatives including quick lime, slaked lime, pulverized lime, lime milk, • calcium carbonate or finely ground limestone, calcium hydroxide, calcium phosphate, or a mixture thereof.
  14. 14. Process according to claim 12 or 13, wherein the DCP is further processed to produce, • a fertilizer, preferably of type monoammonium phosphate (MAP), diammonium phosphate (DAP), Ammonium-Potassium Phosphate fertilizer (NPK fertilizer), • animal feed, • food grade products, • merchant grade or purified phosphoric acid or technical grade phosphoric acid.

Description

PROCESS FOR PRODUCING A PHOSPHATE CONTAINING PRODUCT FROM A PHOSPHATE SOURCE BY DIGESTION WITH SULPHURIC ACID FIELD OF THE INVENTION [0001] The present invention relates to a process for producing a phosphate containing product from a phosphate source (P0) by digestion with in particular sulphuric acid. The phosphate source can comprise phosphate ores or ashes from different origins, industrial or municipal. The present invention enhances extraction from phosphates source having high values of MER (= (%AI2O3 + %MgO + %Fe2O3) I %P2O5). BACKGROUND OF THE INVENTION [0002] Phosphate sources can be issued from ore, typically containing apatite. Because of a combination of reduction of reserves of high P2Os contents ores and of limited accessibility for geo-political reasons, phosphate producers have to work with ores of lower quality (such as beneficiation residues). Circular economy pushes industries to (re-) use resources which were previously used. In this context, ashes from the incineration can be an interesting alternative phosphate source. The ashes can be ashes from the incineration of sewage, animal bones, and the like. These phosphate sources comprise numerous other components which need be separated to reach the levels of purity required by the corresponding end applications. To this purpose, raw material issued from the phosphate source can be digested in a first step in a digestion liquor to solubilize the phosphate ions and maintain as many other components as possible insoluble. This digestion step is often followed by a separation step, to separate a solid residue mainly composed of insoluble components from a liquid filtrate containing the dissolved phosphates. The selection of the conditions used in this first step, including the composition of the digestion liquor, the duration of the digestion, the temperature, the pH, etc., is often a trade-off between ensuring that a substantial amount of the phosphates present in the raw material is indeed solubilized and present in the liquid filtrate after separation, and preventing as many other components as possible from solubilizing too and thus remaining in the filtrate, unseparated from the phosphates. If the digestion is too weak, phosphates can be retained in the raw material in the insoluble form and if, on the other hand, digestion is too strong, many impurities will be dissolved too and entrained with the phosphates in the liquid filtrate. [0003] Most ores and many ashes comprise certain amounts of CaO and I or sulphates (SO42 ). Undesired calcium can be precipitated as calcium sulphates (= CaSO4.nH2O) by addition of sulphuric acid (= H2SC>4). Digesting the raw material with sulphuric acid in dihydrate I hemi-hydrate process mode can, however, be detrimental to the efficacy of the process, because of co-precipitation of calcium phosphates. In particular, addition of sulphuric acid introduces sulphate ions (SO42 ) which need be eliminated and may require in some cases addition of Ca2+ ions to precipitate calcium sulphates (CaSC .nFW) with different degrees of hydration (i.e., n = 0 to 2). If calcium sulphates co-precipitate with substantial amounts of P2O5 and I or if P2O5 is entrapped in calcium sulphate crystals the recovery in phosphorus is decreased accordingly, as it cannot easily be dissociated after co-precipitation or entrapment. Moreover, the dihydrate-reaction of phosphate rock (e.g., Cas(PO4)2) with sulphuric acid (H2SO4) yields more calcium sulphates than phosphoric acid, i.e., more side products than end-products. [0004] Digesting raw material with sulphuric acid may also lead to the formation of hemihydrate or anhydride calcium sulphate. Calcium sulphate hemihydrate (= CaSC .^FW) is prompt to rehydrate and set to form dihydrate plaster (= CaSO4.2H2O) which can block the production line, generating extra costs either by stopping the production for the time required to unclog and clean the equipment or by including spare pieces of equipment to switch the production through the spare pieces. Anhydride (= CaSC ) is difficult to filter, thus hindering the separation of liquid from solid phases. [0005] Because of the decreasing access to high quality ores for the extract phosphates, ores of lower quality, i.e., comprising more other components, which must thus be separated in later steps. The Minor Element Ratio, (MER = (%AbO3 + %MgO + %Fe2C>3) I %P2C>5), is a ratio known in the art which is representative of the total amount of selected impurities (viz., Al, Mg, Fe) expressed as their oxides equivalent relative to the amount of total phosphorus expressed as P2O5 equivalent present in the phosphate source. It is generally more difficult to extract a high proportion of phosphates present in a phosphate source having a high value of the MER than in a phosphate source having a lower value of MER. [0006] EP4201880 addresses relatively pure sources of phosphates, with a MER of 0.046. WO2019030403 proposes to digest a phosphate source conta