(19)

(11)

EP 0 463 050 A1

(12)

(43) Date of publication: 02.01.1992 Bulletin 1992/01 (21) Application number: 90904884.0 (22) Date of filing: 16.03.1990

(51) International Patent Classification (IPC):  C01B 31/ 36( . ) (86) International application number: PCT/GB1990/000395 (87) International publication number: WO 1990/010595 (20.09.1990 Gazette 1990/22)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB IT LI LU NL SE (30) Priority: 16.03.1989 GB 19890006044 (71) Applicant: DAVY RESEARCH AND DEVELOPMENT LIMITED Stockton-on-Tees, Cleveland TS18 3HA (GB)	(72) Inventors: NADEN, David 47 Scalby Grove Cleveland TS19 7RP (GB) BAGHA, Shahin Cleveland TS23 3SX (GB) (74) Representative: Eyles, Christopher Thomas  W.P. THOMPSON & CO. Celcon House 289-293 High Holborn London WC1V 7HU London WC1V 7HU (GB)