EP0011516B1 - Procédé pour la récupération de l'uranium contenu dans des composés phosphatés - Google Patents

Procédé pour la récupération de l'uranium contenu dans des composés phosphatés Download PDF

Info

Publication number
EP0011516B1
EP0011516B1 EP79400627A EP79400627A EP0011516B1 EP 0011516 B1 EP0011516 B1 EP 0011516B1 EP 79400627 A EP79400627 A EP 79400627A EP 79400627 A EP79400627 A EP 79400627A EP 0011516 B1 EP0011516 B1 EP 0011516B1
Authority
EP
European Patent Office
Prior art keywords
process according
organic phase
dialkyl
uranium
acid
Prior art date
Legal status (The legal status 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 status listed.)
Expired
Application number
EP79400627A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0011516A1 (fr
Inventor
Jean-Michel Demarthe
Serge Solar
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
COMPAGNIE FRANCAISE DE MOTKA
Original Assignee
FRANCAISE DE MOTKA Cie
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 FRANCAISE DE MOTKA Cie filed Critical FRANCAISE DE MOTKA Cie
Priority to AT79400627T priority Critical patent/ATE4794T1/de
Publication of EP0011516A1 publication Critical patent/EP0011516A1/fr
Application granted granted Critical
Publication of EP0011516B1 publication Critical patent/EP0011516B1/fr
Expired legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
    • C22B60/02—Obtaining thorium, uranium, or other actinides
    • C22B60/0204—Obtaining thorium, uranium, or other actinides obtaining uranium
    • C22B60/0217—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes
    • C22B60/0252—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries
    • C22B60/026—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries liquid-liquid extraction with or without dissolution in organic solvents

Definitions

  • the present invention relates to a process for the recovery of uranium contained in solid phosphate compounds or in solution. More particularly, it relates to a uranium recovery process present in an organic phase in the form of a salt of pyrophosphoric di e st st.
  • the first step in this transformation is acid leaching, usually sulfuric, which converts tricalcium phosphate to phosphoric acid and insoluble calcium sulfate. This leaching also releases various metals, such as uranium, thorium, vanadium and rare earth metals, which have been trapped in the phosphate deposits over the ages.
  • the concentration of these metals in phosphate ores is very low. Thus, for uranium, it is generally between 0.005 and 0.02%. Although these grades are low, and due to the high market value and strategic nature, and efforts have been made for a quarter of a century to recover the uranium contained in the acid leaching solutions of phosphate minerals.
  • pyrophosphates hydrolyze quickly, forcing to frequently renew - .phase organic liquid-liquid extraction and seriously hampers the process of the operating costs.
  • uranium-pyrophosphate complex is so stable that a very powerful reagent is required to re-extract the uranium.
  • one of the aims of the present invention is to provide a new process for the recovery of uranium present in phosphate compounds by means of an organic phase containing a pyrophosphoric dialkyl acid, process in which the consumption in this the latter is greatly reduced compared to known methods.
  • Another object of the invention is to provide a process for the re-extraction of uranium present in an organic phase which contains a diester of pyrophosphoric acid, this process avoiding the use of hydrofluoric acid.
  • An additional object of the invention is to provide a new process for recovering uranium contained in phosphate solutions which allows easy operations of liquid-solid and liquid-liquid separation of the salts obtained and which reduces the impregnation of the latter by compounds of pyrophosphoric dialkyl acid.
  • the alcohol chains of the pyrophosphoric dialkyl acid specified above may be straight or branched.
  • alcohols capable of being esterified to give dialkyl pyrophosphates having one or more ether functions there may be mentioned the alcohols obtained by condensation of a heavy alcohol as defined below, with an alkene oxide, such as l ethylene or propylene oxide.
  • alkene oxide such as l ethylene or propylene oxide.
  • heteroalkyl radical comprises from 4 to 20 carbon atoms and, preferably, from 6 to 12 carbon atoms.
  • diester of pyrophosphoric acid it is possible, in particular, to use dicaproyl pyrophosphoric acid, or dioctyl pyrophosphate which, subsequently, will sometimes be designated by its acronym: "OPPA" (octyl pyrophosphoric acid).
  • condensation which leads to the pyrophosphates used in the process according to the present invention it can be carried out according to the method described in the patent of the United States. US-A 2,947,774.
  • the organic phase contains two to five moles of solubilizing agent per mole of dialkyl pyrophosphoric acid.
  • One of the preferred solubilizers is octanol-2.
  • the pressure at which the invention is carried out is preferably atmospheric pressure for reasons of simplicity.
  • the temperature must not be higher than 50 ° C, failing which the pyrophosphoric dialkoyl acid hydrolyzes very quickly.
  • Room temperature is therefore preferably chosen, that is to say from 15 to 30 ° C.
  • the concentration of pyrophosphoric dialkoyl acid in the organic phase is preferably between 1 and 10% by weight, the rest of this phase being constituted by a diluent chosen from those which are well known to specialists in the subject such as kerosene and dodecane.
  • the organic phase specified above can be loaded with uranium, either by bringing it into contact with an acid uranium phosphate solution whose pH is less than or equal to 2 and preferably less than or equal to 1, or by solid-liquid extraction d 'a uranium phosphate compound, for example a phosphate ore.
  • the gaseous ammonia added to the aqueous phase during step a) must be in an amount at least equal to the amount necessary to transform the excess dialkyl pyrophosphoric acid into its double ammonium salt.
  • the excess ammonia does not remain in the organic phase and is released into the atmosphere. To save this expensive reagent, it is therefore necessary to limit the quantity of ammonia introduced.
  • a satisfactory implementation consists in choosing as quantity of ammonia added during step a) two to five moles of ammonia per mole of pyrophosphoric dialkyl acid.
  • step aj is advantageously between half an hour and two hours and preferably close to one hour.
  • Step b) can be carried out by filtration, cycloning or centrifugation.
  • the present invention is based in part on the discovery that the colloidal and / or viscous nature of the precipitates obtained during the re-extraction of uranium was due to the presence of excess pyrophosphoric dialkoyl acid, that is to say not linked to a uranium atom in the organic phase.
  • steps a) and b) therefore to eliminate excess dialkyl pyrophosphoric acid in the organic phase and to recover it in solid form.
  • This pyrophosphoric dialkyl acid in the form of an ammonium salt, is not subjected to the re-extraction stage and can be directly recycled to the stage of treatment of the phosphate compounds in order to extract the uranium therefrom.
  • a significant part of the pyrophosphoric dialkyl acid is not confronted with conditions suitable for facilitating its hydrolysis.
  • steps a) and b) allow substantial savings in reagent, even if the subsequent steps for re-extracting uranium facilitate the hydrolysis of dialkyl pyrophosphoric acid.
  • steps a) and b) in the process described above for re-extraction from hydrofluoric acid therefore allows substantial savings in reagents.
  • the process for the recovery of uranium contained in phosphate solutions described in French patent application FR.A 7725899 filed by the Applicant comprises a step a) of bringing the starting uranium phosphate solution into contact with an organic phase containing a pyrophosphoric acid diester and a step b) of bringing the organic phase charged with uranium obtained in step a) above into contact with an alkaline solution. Between these two steps, it is easy to insert the two steps a) and b) of the method according to the present invention.
  • oxidizing agent use may be made of chlorine, hypochlorites, chlorates and, more generally, all oxidizing agents whose apparent normal potential is greater than 300 millivolts relative to the electrode at l 'hydrogen. It should be noted however that it is preferable to use hydrogen peroxide, persulfates, as well as all the bodies generating hydrogen peroxide on contact with water such as, for example, oxylith.
  • the pH obtained after the addition of ammonia is made between 8 and 10, and preferably between 9 and 10.
  • the quantity of ammonia added in step d) is equal to a value of between one and four moles per gram of phosphorus initially contained in the aqueous and solid phases resulting from stage c), the concentration of the ammonia used being advantageously between 1 and 4 N, and preferably between 1.5 and 2.5 N.
  • step d) preferably lasts half an hour to two hours. During this treatment, the oxidation of uranium IV to uranium VI continues if it was not complete after step c). An oxidizing agent as defined above can be added during this step.
  • the method further comprises the following step: e) the liquid and solid phases present in the reaction mixture obtained after step d) are separated from one another.
  • This step e) can be carried out by filtration, cycloning or, preferably, centrifugation.
  • the strong mineral acid used can be any of the strong mineral acids existing with the exception of those whose redox potential is sufficient to react with dialkyl pyrophosphoric acid and to oxidize it. .
  • the use of nitric acid should therefore be avoided.
  • the preferred strong mineral acid is phosphoric acid.
  • the organic phase used in step j) has a composition identical to that resulting from step c) or else is a fraction of the latter.
  • the organic phase having re-extracted the pyrophosphoric dialkyl acid in step j) is advantageously recycled to step a).
  • the solubilizing agents must be liposoluble compounds which have electronic doublets capable of giving hydrogen bonds with the diesters of pyrophosphoric acid.
  • trialkyl phosphates such as, for example, tributyl phosphate, which will sometimes be designated subsequently by means of its English acronym "TBP" (tributyl phosphate)
  • trialkylphosphine oxides such as, for example, trioctylphosphine oxide, and heavy alcohols.
  • these agents should preferably be in a ratio of at least 0.5 mole per mole of pyrophosphoric dialkyl acid.
  • an additional aim of the present invention is to provide a process which promotes the extraction of uranium over that of iron.
  • Another object of the present invention is to provide a process which allows the complete exhaustion of the uranium present in the phosphate solutions.
  • dialkyl pyrophosphoric acid at such concentration levels does not present any difficulties when bringing a phosphate solution into contact with the organic phase and which if contacting is carried out with a ratio between the organic phase and the aqueous phase (O / A) of between 1 and 1 / 50th, no problem of emulsion appears.
  • O / A ratio of less than 1 / 50th and greater than 1 / 200th
  • it is possible to avoid the emulsion problems by carrying out the extraction at a temperature higher than 30 ° C and preferably between 35 and 45 ° C.
  • emulsion problems only arise when the phosphate solution has been poorly reduced.
  • This implementation is based on the fact that surprisingly the ratio between the extracted uranium and the extracted iron increases significantly with the concentration of pyrophosphoric dialkyl acid in the organic phase and that, unlike previous theoretical studies, the ratio between the uranium extracted and the concentration of di-octyl pyrophosphoric acid increases with the latter. This contradiction is difficult to explain but could be due to the fact that iron is present in high proportion in the phosphate solutions treated by the applicant while there was none in previous theoretical studies.
  • solubilizing and stabilizing agents gradually facilitates the dissolution of the dialkyl pyrophosphoric acid.
  • one of the advantages of using a high concentration of pyrophosphoric dialkyl acid is to allow either to reduce the constraints relating to the reduction of the solution, or to completely exhaust a uraniferous solution of phosphoric acid at 30%. with relatively few extraction stages.
  • Examples 1 to 5 are divided into two parts.
  • the first part does not have the invention as an object and serves only as an element of comparison to the second part which exemplifies the invention proper.
  • Example 3.1 The operating conditions are identical to that of Example 3.1., But 100 ml of water is replaced by 100 ml of ammonia.
  • the precipitate consists largely of OPPA ammonium salts which are soluble in water and dilute ammonia.
  • the organic phase is divided into four equal volumes which will be subjected to a second re-extraction under different conditions.
  • the amount of hydrogen peroxide and water used varies according to the tests.
  • aqueous phases obtained are cloudy and more particularly that of test 4 which is milky.
  • test 4 which is milky.
  • all the precipitates remain at the interface of the organic and aqueous phases.
  • the precipitate is in the centrifugation pellet, but traces of precipitate trapped in a gelatinous layer at the interface of the organic and aqueous phases were nevertheless observed.
  • the balance shown in the table has been reduced to a flow of 1 m 3 .
  • the initial organic phase has the same composition as that of Example 2 (3% OPPA, 3% octanol, 94% kerosene).
  • This example shows in particular that the percentage of OPPA which is selectively precipitated in the form of ammonium salt by the injection of gaseous ammonium is 54.2%.
  • step c) causes 98.1% of the uranium contained in the starting organic phase to precipitate.
  • the uranium is recovered in the form of a "yellow-cake" with a yield of the order of 94%.
  • the following nonlimiting examples relate to the selective extraction of uranium with respect to iron.
  • the uranium and iron content of the solution is indicated in each of the examples.
  • the contacts are carried out as follows: the aqueous phase and the organic phase are introduced into a separatory funnel, the two phases are vigorously agitated for one minute. The phases are then decanted for 15 minutes then they are separated and aliquots of each phase are assayed.
  • the table "depletion of the aqueous phase” relates to the extraction of an aqueous phase brought into successive contacts with several fresh organic phases while the table “enrichment of the organic phase” corresponds to the enrichment of a organic phase by successive contact with fresh aqueous phases.
  • the O / A ratio is always 1/50
  • the diluent is kerosene
  • this example clearly shows that it is possible to completely extract the uranium present in phosphoric acid at 30%, even when the ferric iron of the latter is not reduced to the ferrous state, in using a highly concentrated organic phase containing dialkyl pyrophosphoric acid.
  • the high concentration of pyrophosphoric acid can cause difficulties during re-extraction.

Landscapes

  • Engineering & Computer Science (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Manufacturing & Machinery (AREA)
  • Environmental & Geological Engineering (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)
EP79400627A 1978-09-08 1979-09-07 Procédé pour la récupération de l'uranium contenu dans des composés phosphatés Expired EP0011516B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT79400627T ATE4794T1 (de) 1978-09-08 1979-09-07 Verfahren zum wiedergewinnen von in phosphatverbindungen enthaltenem uran.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7825815 1978-09-08
FR7825815A FR2435444A1 (fr) 1978-09-08 1978-09-08 Procede pour la recuperation de l'uranium contenu dans des composes phosphates

Publications (2)

Publication Number Publication Date
EP0011516A1 EP0011516A1 (fr) 1980-05-28
EP0011516B1 true EP0011516B1 (fr) 1983-09-28

Family

ID=9212434

Family Applications (1)

Application Number Title Priority Date Filing Date
EP79400627A Expired EP0011516B1 (fr) 1978-09-08 1979-09-07 Procédé pour la récupération de l'uranium contenu dans des composés phosphatés

Country Status (4)

Country Link
EP (1) EP0011516B1 (enrdf_load_stackoverflow)
AT (1) ATE4794T1 (enrdf_load_stackoverflow)
DE (1) DE2966225D1 (enrdf_load_stackoverflow)
FR (1) FR2435444A1 (enrdf_load_stackoverflow)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4652431A (en) * 1981-02-26 1987-03-24 Prodeco, Inc. Process for recovering uranium using an alkyl pyrophosphoric acid and alkaline stripping solution
US4652432A (en) * 1981-02-26 1987-03-24 Prodeco, Inc. Process for recovering uranium using an alkyl pyrophosphoric acid and alkaline stripping solution
US4490336A (en) * 1981-05-27 1984-12-25 Prodeco, Inc. Process for stripping uranium from an alkyl pyrophosphoric acid
FR2531697B1 (fr) * 1982-08-12 1985-06-28 Pechiney Ugine Kuhlmann Uran Procede de valorisation de l'uranium et des terres rares contenus dans de l'uf4 impur provenant de l'extraction de l'uranium de l'acide phosphorique
DE3311245A1 (de) * 1983-03-28 1984-10-04 Chemische Fabrik Budenheim Rudolf A. Oetker, 6501 Budenheim Verfahren zur abtrennung von uran aus phosphorsaeuren

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2830872A (en) * 1952-10-03 1958-04-15 Robert F Mccullough Recovery of uranium values from phosphate rock
US2866680A (en) * 1955-03-02 1958-12-30 Ray S Long Alkyl pyrophosphate metal solvent extractants and process
US2883123A (en) * 1955-08-11 1959-04-21 Joseph C Finnigan Safety apparatus for use on a motor vehicle

Also Published As

Publication number Publication date
FR2435444B1 (enrdf_load_stackoverflow) 1981-01-16
EP0011516A1 (fr) 1980-05-28
FR2435444A1 (fr) 1980-04-04
DE2966225D1 (en) 1983-11-03
ATE4794T1 (de) 1983-10-15

Similar Documents

Publication Publication Date Title
FR2459837A1 (fr) Procede pour la recuperation d'uranium a partir d'acide phosphorique obtenu par voie humide
EP0388250B1 (fr) Procédé de traitement de minerais de terres rares
EP0418125A1 (fr) Procédé de traitement de minerais contenant des terres rares
FR2515630A1 (fr) Procede d'extraction et de separation de l'uranium, du thorium et des terres rares par traitement de solutions aqueuses de chlorures de ces elements
CN102753711B (zh) 用于从天然铀浓缩物中纯化铀的方法
WO2020067856A1 (fr) Procede de purification et de concentration des terres rares a partir du phosphogypse
EP0167414A1 (fr) Procédé d'extraction sélective du germanium
EP0030487B1 (fr) Procédé de purification d'un acide phosphorique de voie humide
EP0011516B1 (fr) Procédé pour la récupération de l'uranium contenu dans des composés phosphatés
EP0386205B1 (fr) PROCEDE PERFECTIONNE D'OBTENTION DE COMPOSES DE Ta ET(OU) Nb EXEMPTS D'IMPURETES A PARTIR DE MATERIAUX CONTENANT CES METAUX
US4311676A (en) Process for the recovery of uranium contained in phosphated compounds
EP0026132A1 (fr) Procédé permettant la récupération globale de l'uranium, des terres rares, du thorium et de l'yttrium contenus dans une solution acide
US9932654B2 (en) Extraction of uranium from wet-process phosphoric acid
CA1181239A (en) Simultaneous oxidation and extraction of vanadium from wet-process phosphoric acid
FR2539549A1 (fr) Procede de recuperation globale de l'uranium, de l'yttrium, du thorium et des terres rares contenus dans une phase organique
FR2495126A1 (fr) Procede d'extraction par solvant de l'acide phosphorique
CA1209808A (fr) Procede d'extraction de l'uranium des acides phosphoriques par les acides alkylpyrophosphoriques
US3449074A (en) Process for removing titanium and vanadium from phosphoric acid
EP0053054B1 (fr) Procédé de récupération de l'uranium (VI) présent dans des solutions d'acide phosphorique
CA1136423A (fr) Procede de recuperation de l'uranium d'un acide phosphorique impur
EP0210934B1 (fr) Procédé de séparation de terres rares et de l'uranium d'un concentré de tétrafluorure d'uranium et de leur valorisation
EP0009849B1 (en) A process for the purification of phosphoric acid
FR2678644A1 (fr) Procede de recuperation globale du thorium et des terres rares en milieu nitrate.
EP0239501B1 (fr) Procédé de séparation du fer à partir d'une solution organique contenant de l'uranium
FR2465687A1 (fr) Procede de recuperation globale de l'uranium, des terres rares, du thorium et de l'yttrium contenus dans une solution acide

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): AT BE CH DE FR GB IT LU NL SE

17P Request for examination filed

Effective date: 19800711

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Designated state(s): AT BE CH DE FR GB IT LU NL SE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19830928

Ref country code: IT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.

Effective date: 19830928

REF Corresponds to:

Ref document number: 4794

Country of ref document: AT

Date of ref document: 19831015

Kind code of ref document: T

REF Corresponds to:

Ref document number: 2966225

Country of ref document: DE

Date of ref document: 19831103

REG Reference to a national code

Ref country code: CH

Ref legal event code: PFA

Free format text: COMPAGNIE FRANCAISE DE MOKTA

RAP2 Party data changed (patent owner data changed or rights of a patent transferred)

Owner name: COMPAGNIE FRANCAISE DE MOTKA

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CH

Payment date: 19840814

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19840906

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19840928

Year of fee payment: 6

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LU

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19840930

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: BE

Payment date: 19840930

Year of fee payment: 6

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: AT

Payment date: 19850927

Year of fee payment: 7

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19850930

Year of fee payment: 7

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: AT

Effective date: 19860907

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: CH

Effective date: 19860930

Ref country code: BE

Effective date: 19860930

BERE Be: lapsed

Owner name: CIE FRANCAISE DE MOTKA

Effective date: 19860930

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19870401

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19870527

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19870602

GBPC Gb: european patent ceased through non-payment of renewal fee
REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19881118