Zinc distillation

Muffe,/. muff (Tei h.) sleeve, etc, (see Muff). Muffel. /. muffle, -farbe, /, muffle color, -ofen, m, muffle furnace, -rostofen, m, muffle roaster, -verfahren, n. (Zinc) distillation process, retort process. 

Zinc melts at a fairly low temperature, 419°C, and boils at 918°C, below the temperature at which zinc oxide is reduced to zinc. If zinc had been smelted in the way described, the metal would have distilled when formed. To prevent its reoxidation when in the gaseous condition, the atmosphere of the furnace would have had to be kept free of oxygen so that the metal could cool and condense. The earliest available information on zinc distillation, however, is from as late as the twelfth century c.e. in India the suggested explanation advanced here does not, therefore, provide an answer as to how zinc was smelt before that time. 

The structural determination of aristolochic acid I (1) was first accomplished by Pailer et al. Aristolochic acid I(Ci7Hn07N) is easily soluble in alkali as well as sodium bicarbonate. It was esterified with diazomethane in dioxane to give a methyl ester (C,gHi307N), and the methyl ester was readily saponified to recover aristolochic acid I. Zinc distillation of 1 gave a phenanthrene (Scheme 6). Aristolochic acid I was decarboxylated with copper powder in quinoline to yield a nitro phenanthrene derivative (OjgHjjOjN.Sl). 

Zinc.—The chief ore of zinc is the sulphide. To convert it into the oxide, it is roasted on a flat hearth in a current of air 2ZnS + 302= 2ZnO + 2S02. The oxide is mixed with small coal (slack) and placed in cylindrical retorts of fireclay. These retorts have pipes of rolled sheet-iron luted to the open ends with fireclay they are packed into a furnace in tiers, and the temperature is raised to bright redness. The coal distils first, giving off coal-gas, which expels air from the retorts. When the temperature exceeds 1000% the zinc distils and condenses in the iron pipes. It happens that almost all zinc ores contain cadmium sulphide, which, like zinc sulphide, is converted into oxide by roasting and on distillation, the cadmium, which is the more volatile metal, distils over first and condenses in the outer portion of the tubes. These are untwisted and the metal removed with a chisel. 

Despite its comparatively high price, silicon carbide is a significant refractory product due to its exceptional properties, such as its high thermal conductivity, high hardness and mechanical strength. It is used in zinc distillation kilns and in the manufacture of muffles, capsules and kiln furniture for the clay ceramic industry (see Section 5.5.4.7.2). In recent years silicon carbide has also been used in the refractory linings of blast furnaces and utilization in other sectors of the steel producing industry is in evaluation. 

Six processes that are representative of those initially selected for evaluation in the PDPM Program are summarized below. Several of these processes are described in separate papers that are included in this Actinide Separations Symposium. A seventh process, the Zinc Distillation Process is described in greater detail. This process was selected as a reference process to meet the criteria for a proliferation-resistant exportable technology. 

Zinc Distillation Process ( 3, 4 ). A zinc distillation process was selected as a reference pyrochemical process that would have a sufficient degree of proliferation resistance that it could be used by nonweapons nations to reprocess spent fuel without significantly increasing their weapons production capability. The process has the inherent proliferation-resistant advantages of being a low decontamination process with limited plutonium enrichment in uranium-plutonium-zinc mixtures. The process chemistry flow sheet for this process is shown in Figure 1. 

The zinc distillation process consists of four basic operations to coprocess and recover uranium and plutonium containing fission products from spent FBR mixed-oxide fuels. These operations are ... 

Miles, K. M., Argonne National Laboratory, "The Pyrocivex Processes are Proliferation Resistant Pyrochemical Reprocessing Methods such as the Zinc Distillation or Modified Salt Transport Process," Private Communication, 1979. 

A method combining the two above-described processes is one in which zinc infiltration is followed by Coldstream crushing with a final zinc distillation step. 

The last part of the de-silverizing proeess is the removal of excess zinc from the lead bullion. This can be achieved in numerous ways, such as chlorination and oxidation, but the accepted practice by major primary smelters is vacuum distillation of the zinc from the bullion. The zinc-rich lead is heated to 600°C, and a vacuum is applied. Zinc distils from the lead and deposits in a solid crystalline state on a... 

The formation of a single product from zinc distillation and only one disulfonic acid by oxidation would follow if cassipourine were a bis-(disulfide) with the two halves symmetrically substituted, and a 1,2-structure was envisaged as the most rational. The X-ray analysis of a... 

Granulated Zinc Hydrochloric Acid. Solution of Chlorine. Carbonate of Zinc. Distilled Water. . ... 

Excessive zinc distillation times caused by high zinc levels in the feed, and high dross carryover in the feed... 

During continuous operation, a steady thermal gradient exists through the walls of the trays. The external surfaces of the trays may reach 1150 C, whereas the internal surfaces are maintained at 900°C by zinc distillation. Other stresses are caused by the introduction of the liquid zinc to be refined in the middle part of the column. The metal is introduced at a temperature varying between 500°C and 600°C within the column, so that several trays located under the zinc entrance are cooled (the normal distillation temperature is around 900°C), and their bottoms and chaimels are then submitted to an additional thermal gradients. 

In the lower part of the column, an analogous phenomenon of zinc impregnation is noted for the bottoms of the trays which are maintained at a relatively low temperature by zinc distillation. Chemical reactions and more intense oxidation of the zinc complicate the degradation process for the walls of the trays, the external surface of which is submitted to hi er temperatures in the combustion chamb. A high level of zinc oxide (ZnO) and the tridymite form of silica (Si02) are found on the external surfaces. Metallic zinc is still sometimes observed in the material. Here, however, the simultaneous presence of zinc and... 

Figure 7 - Schematic Representation of Zinc Distillation through a Nitrogen Atmosphere...

The most widely used reductive degradation methods are zinc distillation and sodium amalgam reduction. Fused aromatic structures (methyl substituted naphthalene, anthracene, pyrene, and perylene) are the major digest products of this reduction of humic substances. 

FIG.9 ZINC DISTILLATION FURNACE-ZAWAR CROSS SECTION... 

Zinc Distilled water 15 ppm mixture of calcium and zinc metaphosphates... 

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