WO1995035257A1 - Procede de purification de l'acide phosphorique - Google Patents

Procede de purification de l'acide phosphorique Download PDF

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Publication number
WO1995035257A1
WO1995035257A1 PCT/FI1995/000354 FI9500354W WO9535257A1 WO 1995035257 A1 WO1995035257 A1 WO 1995035257A1 FI 9500354 W FI9500354 W FI 9500354W WO 9535257 A1 WO9535257 A1 WO 9535257A1
Authority
WO
WIPO (PCT)
Prior art keywords
acid
phosphoric acid
process according
impurities
concentrated
Prior art date
Application number
PCT/FI1995/000354
Other languages
English (en)
Inventor
Anders Weckman
Original Assignee
Kemira Chemicals Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kemira Chemicals Oy filed Critical Kemira Chemicals Oy
Priority to AU27401/95A priority Critical patent/AU2740195A/en
Priority to SK1616-96A priority patent/SK161696A3/sk
Priority to EP95922550A priority patent/EP0768985A1/fr
Priority to PL95318219A priority patent/PL318219A1/xx
Priority to RO96-02409A priority patent/RO114886B1/ro
Priority to RU96124067A priority patent/RU2139240C1/ru
Publication of WO1995035257A1 publication Critical patent/WO1995035257A1/fr
Priority to BG101023A priority patent/BG101023A/xx
Priority to NO965470A priority patent/NO965470L/no

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Classifications

    • 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
    • C01B25/18—Phosphoric acid
    • C01B25/234—Purification; Stabilisation; Concentration
    • C01B25/2343—Concentration concomitant with purification, e.g. elimination of fluorine

Definitions

  • This invention relates to a process for removing impurities from phosphoric acid prepared by the wet process.
  • Phosphoric acid can be prepared by the wet process by reacting a mineral acid, most commonly sulfuric acid, with a calcium phosphate concentrate, whereupon a dilute phosphoric acid, containing approx. 30 % P 2 0 5 , and a calcium sulfate precipitate are formed- After filtration, the acid contains many kinds of anionic impurities, such as sulfate and fluorine compounds, and cationic impurities, the most important of which are iron, aluminum, magnesium and calcium, and organic impurities.
  • anionic impurities such as sulfate and fluorine compounds
  • cationic impurities the most important of which are iron, aluminum, magnesium and calcium, and organic impurities.
  • the quantity and type of the impurities depend above all on the raw phosphate used as the raw material.
  • the dilute acid is concentrated by evaporation to a concentra ⁇ tion of 50-70 % P 2 0 5 , whereby volatile impurities, such as fluorine compounds, are mostly separated together with the evaporating water vapor, but the concentrations of other im ⁇ purities are increased.
  • US patent specification 4 248 843 discloses a process for the purification of phosphoric acid wherein the magnesium ions present as an impurity are pre ⁇ cipitated as a pyrophosphate. The process has a disadvantage in a high viscosity at higher concentrations, complicating the crystallization of the pyrophosphate and the separation of the crystals.
  • the crystallizing magnesium pyrophosphate is not biologically active, and therefore it as such has no utility purpose; the compound requires hydrolysis in order to be usable as a fertilizer or in animal feeds.
  • An object of the present invention is indeed to produce very pure phosphoric acid at economical cost.
  • a further object of the invention is to cause the metal ions present as impurities to precipitate as compounds which are usable in industry.
  • the impurities present in phosphoric acid can be precipitated as compounds which crystallize within even lower concentration ranges of phosphoric acid than in state-of-the-art processes. It has additionally been observed that, if the initial acid used in the process does not contain impurities which are re ⁇ lodged as hazardous, such as cadmium, the process offers an additional advantage. Namely, the waste compound formed as an impurity can be utilized as a useful raw material in industry. Thus, the impurity compounds separated by the present process will not become environmental hazards.
  • a process has been pro ⁇ vided for the removal of bivalent metal ion impurities from a wet-process phosphoric acid.
  • a phosphoric acid of a fertilizer grade or filter acid grade is concentrated by heating to a P 2 0 5 concentration of 58-68 %.
  • the bivalent metal ions which are present as impurities are caused to crystallize as a compound M 2+ (H 2 P ⁇ 4 ) 2 ' -H 3 P ⁇ 4 , wherein the metal ions are present as M 2+ , and the number n of associated phosphoric acid molecules is 2- 5.
  • the initial acid used may be a we -process phosphoric acid the P 2 0 5 content of which may be approx. 20-60 %, typically 30 % P 2 C> 5 or 50 % P 2 0 5 .
  • the sulfate content of such a phosphoric acid typically varies within 2-4 % S0 4 .
  • Wet-process phosphoric acid contains a variety of anionic, cationic and organic impurities, the concentrations of which vary depending on the origin of the phosphate concentrate from which the acid was prepared.
  • the process according to the invention it is possible to lower the cationic metal ion concentrations in phosphoric acid almost completely, or at least to an acceptable level.
  • concentrations of, for example, the following metal ions have been lowered: Mg, Fe, Ca, Mn, Zn, Cd, Co, Cu, Pb, and Ni.
  • the formed crystalline compound is neither magnesium pyrophosphate nor anhydrous monomagnesium phosphate.
  • the crystals are washed with ethanol, some of the phosphoric acid dissolves, and Mg(H 2 P0 4 ) 2 and Fe(H 2 P0 4 ) 2 -2H 2 0 were identified as the compounds in an X-ray diffraction spectrum.
  • the crystallized metal compound crystals can be separated from the phosphoric acid by methods known per se. such as centrifugation, pressure filtration, vacuum filtration, or sedimentation.
  • the removal of the sulfate is not indispensable.
  • the sulfate can, for example, be removed directly from the phos ⁇ phoric acid by precipitation as gypsum by means of a calcium salt. It has, however, been observed that a lowering of the sulfate concentration enables lower temperatures to be used in the acid concentration step than without a lowering of the sulfate concentration.
  • the process also enables the waste compound crystallized out from phosphoric acid to be used as a raw material in industry.
  • Magnesium phosphate crystallized out from a phosphoric acid prepared from a crude phosphate which has a low heavy metal content can be used, for example, in animal feeds and as a raw material for the fertilizer industry.
  • concentrations of detrimental ions (F, As, Al and Cr) in the crystals are reduced and the concentrations of useful trace elements (Fe, Mn, Zn and Cu) increase in proportion to the concentrations of the feed acid.
  • a fertilizer-grade phosphoric acid (Siilinjarvi) was con ⁇ centrated (150 °C, 65 mm Hg) to 67.5 % P 2 0 5 .
  • the feed acid contained 2.76 % S0 4 .
  • seed was added at a rate of 2 % of the mass of the concentrated acid.
  • the crystals were separated in a centrifuge, and the compound was ascertained by means of an X- ray diffraction spectrum.
  • the quality of the feed and product acids are presented in Table 1.
  • a fertilizer-grade phosphoric acid (Siilinjarvi) in which the sulfate level had been lowered (0.8 % S0 4 ) was concentrated to 64.2 % P 2 0 5 . Seeds (1 %) were added at 95 °C, and the acid was cooled in five hours to 50 °C.
  • the feed acid contained 1.5 % Mg and the product acid contained 0.6 % Mg.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Fertilizers (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)

Abstract

L'invention concerne un procédé de purification d'un acide phosphorique impur préparé par voie humide. L'acide à purifier est concentré par chauffage à 58 - 68 % de P2O5. Les impuretés sont éliminées de l'acide par cristallisation sous la forme d'un composé M2+(H2PO4)2.n.H3PO4, où M2+ est un ion métallique bivalent contaminant et n se situe entre 2 et 5.
PCT/FI1995/000354 1994-06-20 1995-06-19 Procede de purification de l'acide phosphorique WO1995035257A1 (fr)

Priority Applications (8)

Application Number Priority Date Filing Date Title
AU27401/95A AU2740195A (en) 1994-06-20 1995-06-19 Process for the purification of phosphoric acid
SK1616-96A SK161696A3 (en) 1994-06-20 1995-06-19 Process for the purification of phosphoric acid
EP95922550A EP0768985A1 (fr) 1994-06-20 1995-06-19 Procede de purification de l'acide phosphorique
PL95318219A PL318219A1 (en) 1994-06-20 1995-06-19 Phosphoric acid purifying method
RO96-02409A RO114886B1 (ro) 1994-06-20 1995-06-19 Procedeu pentru purificarea acidului fosforic
RU96124067A RU2139240C1 (ru) 1994-06-20 1995-06-19 Способ очистки фосфорной кислоты
BG101023A BG101023A (en) 1994-06-20 1996-12-03 Process for the purification of phosphohoric acid
NO965470A NO965470L (no) 1994-06-20 1996-12-19 Fremgangsmåte for rensing av fosforsyre

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI942947 1994-06-20
FI942947A FI95905C (fi) 1994-06-20 1994-06-20 Fosforihapon puhdistusmenetelmä

Publications (1)

Publication Number Publication Date
WO1995035257A1 true WO1995035257A1 (fr) 1995-12-28

Family

ID=8540956

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1995/000354 WO1995035257A1 (fr) 1994-06-20 1995-06-19 Procede de purification de l'acide phosphorique

Country Status (12)

Country Link
EP (1) EP0768985A1 (fr)
AU (1) AU2740195A (fr)
BG (1) BG101023A (fr)
CZ (1) CZ365596A3 (fr)
FI (1) FI95905C (fr)
HU (1) HUT76719A (fr)
NO (1) NO965470L (fr)
PL (1) PL318219A1 (fr)
RO (1) RO114886B1 (fr)
RU (1) RU2139240C1 (fr)
SK (1) SK161696A3 (fr)
WO (1) WO1995035257A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100454101B1 (ko) * 2002-03-15 2004-10-26 한국화학연구원 인산의 정제방법과 그 장치
KR100542969B1 (ko) * 2005-03-18 2006-01-20 (주) 광진화학 공정폐액으로부터 고순도의 인산을 연속적으로 정제하는방법

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1166102A (en) * 1965-10-04 1969-10-08 Struthers Scientific Int Corp Phosphoric acid process

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1166102A (en) * 1965-10-04 1969-10-08 Struthers Scientific Int Corp Phosphoric acid process

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100454101B1 (ko) * 2002-03-15 2004-10-26 한국화학연구원 인산의 정제방법과 그 장치
KR100542969B1 (ko) * 2005-03-18 2006-01-20 (주) 광진화학 공정폐액으로부터 고순도의 인산을 연속적으로 정제하는방법

Also Published As

Publication number Publication date
NO965470D0 (no) 1996-12-19
FI942947A0 (fi) 1994-06-20
BG101023A (en) 1997-08-29
PL318219A1 (en) 1997-05-26
HUT76719A (en) 1997-10-28
FI95905B (fi) 1995-12-29
HU9603513D0 (en) 1997-02-28
AU2740195A (en) 1996-01-15
CZ365596A3 (en) 1997-05-14
EP0768985A1 (fr) 1997-04-23
RO114886B1 (ro) 1999-08-30
SK161696A3 (en) 1997-07-09
FI95905C (fi) 1996-04-10
RU2139240C1 (ru) 1999-10-10
NO965470L (no) 1996-12-19

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