Vacuum retorting

A vacuum-retort process (Pidgeon process) was used during World War II for the production of magnesium and calcium. SiHcon, in the form of ferrosihcon, was used as the reducing agent instead of carbon to avoid the problem of cooling magnesium vapor in the presence of carbon dioxide ... 

This process was operated briefly in vacuum retorts by Union Carbide in 1945 (51). 

Pidgeon A process for making magnesium metal by reducing dolomite with ferrosilicon at 1,200°C in a vacuum retort ... 

The FP-3 fission products are oxidized by MgCl2 or ZnCl2, are transferred to the salt phase, and are finally taken up by an acceptor alloy. The FP-4 elements are too inert to be oxidized by MgCl2 or ZnCl2 and remain with the donor alloy. The actinide elements are then separated from the FP-4 Fission products by salt transport to the acceptor alloy followed by vacuum retorting and conversion of metallic intermediates to suitable products. 

Another point of view when reducing fiuorides with sodium concerns the means of separating the salt from the cake. Vacuum separation at elevated temperature, while possible, would have to take place above 1200° C., which rules out the use of cheap iron vacuum retorts. Aqueous methods have the disadvantage that sodium fiuoride is but slightly soluble in water (about 4% at room temperature), but this might be adequate for practical purposes. 

This reaction occurs in a vacuum and the gaseous metal is condensed in a cooler part of the apparatus. AH strontium metal is produced commercially by the thermal reduction process in aUoy steel retorts. 

This continuous process is to be compared with a batch process, such as the Belgian retort process. In this, zinc oxide, free of lead or iron is reduced with carbon to produce zinc vapour, which is condensed in the cold section of the retort. The oxygen potential in this system is very much lower dran in the blast furnace, approximately at the C/CO equilibrium value. A vacuum-operated variant of dris level of reduction is caiTied out to produce zinc vapour which is subsequently converted to zinc oxide before condensation of the metal could take place. 

Use closed-loop systems for pickling regenerate and recover acids from spent pickling liquor using resin bed, retorting, or other regeneration methods such as vacuum crystallization of sulfuric acid baths. 

Therrtial Sterilization of Pouches of Beef. Methodology for food thermoprocessing in cylindrical metal containers assured food sterility in flexible packages. Beef slices (1.25 cm thick) were steam cooked to an internal temperature of 72°C and vacuum sealed in pouches to give a fill of 120 g. These pouches of beef were processed in a standard retort with complete water circulation and a superimposed air pressure of 1.7 X 105 Pa. The retort schedule—a 40-minute cook at 118°C plus come-up time followed by a 30-minute cooling time—achieved a F0 (lethality value) of 6. 

Briquettes of CaO with 5-20% excess powdered A1 are heated under vacuum to 1170°C in a Ni-Cr steel (15/28) retort in which the Ca vapor, produced by reduction of solid CaO by A1 vapor, is condensed in a zone at 680-740 C. Any Mg impurity is condensed in a zone at 275-350°C a mixture of the two metals condenses in an intermediate zone. The A1 content of the product can be reduced by passing the metal vapor, before it condenses, through a vessel filled with solid CaO. The adaptation of the FeSi thermal reduction process for Mg production (see 7.2.3.2.1) to Ca manufacture has also been described but is not economically viable in comparison with the above process. The thermal reduction of CaO with carbon has been proposed as for Mg production, however, the reversibility of the equilibrium ... 

Sample. Petroleum crude oil sample from Long Beach Field (TUMS Well C-331, API° 20), California, and shale oil obtained by retorting at 500°C the Green River Oil Shale (Anvil Point Mine) were studied. About 20 g of shale oil was dissolved in 200 ml of THF and then filtered. The sample was recovered by a rotary evaporator. Although the same procedure was done on the other samples, the percent ash was different for each sample. All the samples were evaporated to a constant weight in a vacuum oven at 50°C. 

---