Vacuum-retort process

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). 

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. 

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

The benefit of these closures is that they have two forms of tamper evidence a vacuum-indicating button and a plastic tamper-evident band. They are ideal for hot-fill, cold-fill and retorted processes, and generally are available in the smaller 40-51 mm size range. 

The furnace is sealed and heated under vacuum to a temperature over 700°C (1,300°F). Mercury that vaporizes from the waste is collected in the off-gas and condensed to a liquid. This liquid mercury is distilled to further purify the material. Off-gases are further treated to remove water vapor and traces of mercury (U.S. EPA, 1994 Bethlehem Resource Recovery Division). As an alternative to the batch process, mercury can be recovered in a continuous retort process utilizing a rotary kiln (AERC/MTI). 

The monolayer cast film and the multilayer cast film were measured and cut to produce prototype pouches for subsequent retort processing the dimensions of the pouches were 19.05 x 6.98 cm. The pouches were filled with distilled water and vacuum sealed to simulate the retortable MRE pouches which are filled with food products and retorted to sterilize the products inside. The retort machine used was the Validator 2000 Vertical Water and Steam Retort, which cooked the pouches for 30 minutes at 121°C. 

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. 

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 ... 

The silicothermic, or ferrosilicon, process involves mixing ground burned dolomite with ground ferrosilicon and fluorspar (eutectic) and pelletizing after which the pellets are charged into the furnace. High vacuum and heat (1170°C) are applied and the calcium oxide present in the burnt dolomite forms infusible calcium silicate that is removed from the retort. 

The 65 per cent peroxide, previously stabilized by adding a small amount of phosphoric acid, is introduced at the rate of 9001 per hr. into a second distillation unit, similar to the first, for re-distillation. Here the process is continuous a4 no solid substances accumulate in the retort. A temperature of 75 °C is njaintained at an absolute pressure of 40 mni Hg. When equilibrium has been reached, the concentration of the liquid in the retort will be about 80 per cent b.w. H2O2 and in the vapour phase will be about 44 per cent b.w. H202. The distilled vapour enters the rectifying column, from where a condensate containing 56 per cent b.w. H202 is continually returned into the retort. Uncondensed water vapour is liquefied in a tubular aluminium condenser connected to a vacuum pump. 

---