Kroll Betterton process

BETTERTON-KROLL PROCESS. A process for obtaining bismuth and purifying desilverized lead that contains bismuth. Metallic calcium or magnesium is added to the molten lead to cause formation of high-melting intennetaHic compounds with bismuth. These separate as a surface scum and are skimmed off. The excess calcium and magnesium are removed from the lead by use of chlorine gas as mixed molten chlorides of lead or zinc. Bismuth of 99.995% purity is produced in this way. 

Bismuth metal is usually separated from ores of other metals by the Betterton-Kroll process. Calcium or magnesium is added to the molten (melted) ore, forming an alloy with bismuth. Later, the bismuth can be separated from the calcium or magnesium to make the pure metal. 

Derivation Debismuthizing of lead bullion by (1) fractional crystallization (2) electrolytic (Betts) refining or (3) addition of calcium or magnesium (Betterton-Kroll process), which removes bismuth. 

Method of purification Desilvering (Parkes process), electrolytic refining (Betts process), pyrome-tallurgical refining (Harris process). Bismuth is removed by Betterton-Kroll process. 

Betterton-Kroll A metallurgical process for removing bismuth from lead. Metallic calcium and magnesium are added to the molten lead, causing precipitation of the sparingly soluble CaMgBi2. 

Betteron—Kroll process, 4 5 14 755. See also Kroll-Betterton debismuthizing process... 

Krieger-Dougherty equation, 21 717 KRIMZ reciprocating-plate column, 10 780 Krinovite, 6 4 7 It Kritchevsky amides, 2 453, 454 Kroll, Wilhelm J., 24 838 Kroll-Betterton debismuthizing process,... 

The bismuth that is found in the lead ore accompanies the lead through the smelting operation right up to the last refining steps. The removal of bismuth then requires special techniques, the most common being the Betterton-Kroll and the Betts processes (5). 

Metnod KroU-Betterton Kroll-Bettarton Process KroS-Betteiton... 

Oxidaticn Enrichment by Kroll-Betterton Process - I Remelting and Oxidation of Calciuni Magnesium Content... 

Pasminco s Kroll-Betterton antimony debismuthising plant has been in operation for almost 20 years and the process has been well documented. The upgrade was carried out simultaneously with the batch refinery stages. Modifications to kettle size, burner control systems, and equipment used to dissolve the calcium and magnesium reagents and to remove the bismuth crusts have all enhanced the ability of the plant to run at the design rate of up to 40 t/h, and remove bismuth fi om input bullion at 0.05-0.06% down to <0.005% Bi. 

The Kroll Betterton process is relatively expensive due to the cost of calcium and magnesium and the fact that they cannot be recovered. There is some flexibility in the relative amounts of calcium and magnesium used, providing some opportunity for cost optimisation. 

During smelting, calcium reports exclusively to slag, but is subsequently introduced into lead bullion as calcium metal additions during removal of bismuth by the Kroll Betterton process. The residual calcium is readily removed by oxidation in the final caustic refining step with the addition of sodium... 

Most electrolytic refineries were built before the successful application of the Kroll-Betterton process for bismuth removal as the only reasonable approach for bismuth removal. Since that time no new electrolytic refineries have been installed and the adverse economics are clearly indicated by... 

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