BOPI 03 BR/2023 REPERTOIRE NUMERIQUE 44 A drill string comprising: an elongate hollow main length section (101); a male spigot portion ( 108) provided at the second end ( 106) having an externally threaded section (107) and a non-threaded shank (109) positioned axially intermediate the main length section (101) and the threaded section (107); the shank (109) having a transition section (206) positioned adjacent the main length section (101) or a radially projecting shoulder (110) at the second end (106), the transition section (206); wherein the cross-sectional shape profile of the outer surface of the transition section (206) in the plane of the longitudinal axis (204) comprises a segment of an ellipse having semi-major axis (a); a semi-minor axis (b) wherein the ratio of the semi-major to semi-minor axes (a:b) is within the range 2b˂a˂8b. Figure 4 Consulter le mémoire (11) 20879 (51) C22B 3/06 (2018.01); C22B 3/22 (2018.01); C22B 3/44 (2018.01); C22B 59/00 (2018.01); C22B 60/02 (2018.01) (21) 1202200363 - PCT/EP2021/055557 (22) 05/03/2021 (30) EP n° 20161399.9 du 06/03/2020 (54) Method for selective separation of thorium and cerium from a solid concentrate comprising same and one or more further rare earth metals and acidic rare earth solution thereof. (72) RODAHL, Fredrik (NO); JØRGENSEN, Tom R. (NO) et SPORSTØL, Sigve (NO) (73) 1-YARA INTERNATIONAL ASA, Drammensveien 131 0277, OSLO (NO) et 2-REETEC AS, Karenslyst Allé 9C, OSLO 0278 (NO) (74) AFRIC'INTEL CONSULTING, Essos, Immeuble MAH NDONG Véronique, 2è étage, B.P. 8451, YAOUNDE (CM). (57) The present disclosure relates to a method for separating thorium and cerium from a solid concentrate comprising compounds of thorium, cerium and one or more further rare earth metals, obtainable by increasing to pH 1.8 the pH of an aqueous composition comprising from 6 to 21 weight% nitric acid, from 25 to 33 weight% phosphoric acid, from 3.5 to 5 weight% calcium, and amounts of thorium, cerium and one or more further rare earth metals, the weight% being relative to the total weight of the aqueous composition, and subsequently precipitating and separating the solid concentrate comprising the compounds of thorium and cerium. The method comprises the steps of a) contacting the solid concentrate with an acid such as to achieve a
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