초록 ▼

A ball valve for use in the pressure acid leaching of nickel ores is disclosed. The valve has a valve body and a ball centrally positioned in the valve body, which has a central passage rotatable in the valve body between open and closed positions. At least one seat is disposed between the ball and

A ball valve for use in the pressure acid leaching of nickel ores is disclosed. The valve has a valve body and a ball centrally positioned in the valve body, which has a central passage rotatable in the valve body between open and closed positions. At least one seat is disposed between the ball and the valve body. The ball and seat each comprise a titanium substrate and an ultrafine or nanostructured titania coating. The titania can include from 5 to 45 volume percent of a second phase material that is immiscible with the titania and exhibits corrosion resistance.

대표청구항 ▼

1. A ball valve for handling very corrosive fluids and abrasive solid particles in a pressure leaching process, comprising:a valve body;a ball centrally positioned in the valve body and having a central passage rotatable in the valve body between open and closed positions;at least one seat disposed

1. A ball valve for handling very corrosive fluids and abrasive solid particles in a pressure leaching process, comprising:a valve body;a ball centrally positioned in the valve body and having a central passage rotatable in the valve body between open and closed positions;at least one seat disposed between the ball and the valve body;wherein the ball and seat each comprise a titanium substrate and a titania coating;wherein the titania coating has a grain size of less than 500 nm. 2. The ball valve of claim 1 wherein the coating comprises a titania phase and a phase immiscible with the titania phase in a proportion effective to inhibit grain growth. 3. The ball valve of claim 2 wherein the immiscible phase comprises from 5 to 45 percent by volume of the coating. 4. The ball valve of claim 2 wherein the immiscible phase is selected from zirconia, tantalum oxide, boron carbide, silicon carbide, titanium carbide, diamond and combinations thereof. 5. The ball valve of claim 1 wherein the coating has a thickness from 100 to 500 microns. 6. The ball valve of claim 1 wherein the coating has a ground and polished surface. 7. The ball valve of claim 6 wherein the coating is deposited by thermal spray application of a powder comprising spherical agglomerates in a size range of from 10 to 45 microns comprising a mixture of ultrafine particles of less than 0.3 microns. 8. The ball valve of claim 7, wherein the titania coating has a uniform composition and is bonded directly to a pre-roughened surface of the titanium substrate. 9. The invention of claim 1 wherein the titania coating comprises nanostructured ultrafine particles. 10. The ball valve of claim 1 wherein the coating has a grain size less than 300 nm. 11. The ball valve of claim 10 wherein the coating comprises a titania phase and a phase immiscible with the titania phase in a proportion effective to inhibit grain growth. 12. The ball valve of claim 11 wherein the immiscible phase comprises from 5 to 45 percent by volume of the coating. 13. The ball valve of claim 11 wherein the immiscible phase is selected from zirconia, tantalum oxide, boron carbide, silicon carbide, titanium carbide, diamond and combinations thereof. 14. The ball valve of claim 10 wherein the coating has a thickness from 100 to 500 microns. 15. The ball valve of claim 10 wherein the coating has a ground and polished finish. 16. The ball valve of claim 15 wherein the coating is deposited by thermal spray application of a powder comprising spherical agglomerates in a size range from 10 to 45 microns comprising a mixture of ultrafine particles of less than 300 nm. 17. The ball valve of claim 1 wherein the coating has a grain size less than 100 nm. 18. The ball valve of claim 1, wherein the coating has a uniform composition. 19. The ball valve of claim 18, wherein the titania coating is bonded directly to the titanium substrate. 20. The ball valve of claim 18, wherein the titania coating is bonded to a roughened surface of the titanium substrate. 21. The ball valve of claim 20 wherein the roughened surface is grit blasted to 2-3 mils (50-80 microns). 22. The ball valve of claim 1, wherein the titania coating is bonded directly to the titanium substrate. 23. The ball valve of claim 1, wherein the titania coating is bonded to a roughened surface of the titanium substrate. 24. The ball valve of claim 23 wherein the roughened surface is grit blasted to 2-3 mils (50-80 microns). 25. A pressure acid leaching process comprising alternately opening and closing the ball valve of claim 1 to respectively allow and stop passage of an acid leach mixture comprising abrasive particles in a solution of sulfuric acid at a temperature above 250° C. and pressure above 4000 kPa. 26. The invention of claim 25 wherein the titania coating comprises nanostructured ultrafine particles. 27. The process of claim 25, wherein the solution is at least 98 percent sulfuric acid.