Sintered preparation

Up to 100 tons/hr for iron ore balls 200 tons/hr or more for sinter preparation 50 tons/hr for fertilizer granulation. 

Generally less than 10-15 tons/ hr, but much larger units are in use (e.g. 350 tons/hr fertilizer blunger, 300 tons/hr drum pugmill for sinter preparation)... 

For the sintered preparation, proper weights of high purity Nb and Sn powders are thoroughly mixed and compressed into a cylindrical pellet under 7000 kg/cm. The pressed powder compact is sealed under vacuum in a quartz ampule and heated to 1200°C for 2 h. After sintering the ampule is removed from the furnace and cooled in air. The porous and readily crumbled compact prepared by this method will contain over 4000 ppm oxygen owing to the oxygen content of the fine-powdered Nb and Sn. 

If preferred, the reaction mixture may be cooled, and the crude furil filtered through a sintered gla.ss funnel. The filtrate (containing the copper sulphate-pyridine mixture) is re-oxidised by passing oxygen tlirough it for about 15 hours. An excellent alternative method of preparation is provided by suitable adaptation of Section IV,126, Method 2. 

Prepare a solution of 41 g. of anhydrous palladium chloride (1) in 10 ml. of concentrated hydrochloric acid and 25 ml. of water (as in A). Add all at once 60 ml. of 6iV-sulphuric acid to a rapidly stirred, hot (80°) solution of 63 1 g. of A.R. crystallised barium hydroxide in 600 ml. of water contained in a 2-htre beaker. Add more 6iV-sulphuric acid to render the suspension just acid to htmus (5). Introduce the palladium chloride solution and 4 ml. of 37 per cent, formaldehyde solution into the hot mechanically stirred suspension of barium sulphate. Render the suspension slightly alkaline with 30 per cent, sodium hydroxide solution, continue the stirring for 5 minutes longer, and allow the catalyst to settle. Decant the clear supernatant hquid, replace it by water and resuspend the catalyst. Wash the catalyst by decantation 8-10 times and then collect it on a medium - porosity sintered glass funnel, wash it with five 25 ml. portions of water and suck as dry as possible. Dry the funnel and contents at 80°, powder the catalyst (48 g.), and store it in a tightly stoppered bottle. 

The solutions must be carefully prepared so as to be free of dust particles and other extraneous scatterers. Filtration through sintered glass or centrifugation is widely used to clarify solutions of particles which would compete with polymeric solutes. This concern for cleanliness also extends to glassware, especially scattering cells. A fingerprint on the viewing window is disastrous ... 

Sintering. The charge for sintering is prepared by blending selected concentrates, smelter by-products, returned sinter, flue dust, and when required, additional fuel such as coke bree2e. The blend is then peUeti2ed in preparation for sintering. 

Metalworking, such as swaging, drawing, rolling, etc, may also be performed on slabs or ingots of other metals prepared by any of the consoHdation and sintering techniques described. 

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