Molten salt bath

The principal use of AIF. is as a makeup ingredient in the molten cryoflte, Na.. AIF AI2O2, bath used in aluminum reduction cells in the HaH-Haroult process and in the electrolytic process for refining of aluminum metal in the Hoopes cell. A typical composition of the molten salt bath is 80—85%... 

Maintenance of isothermal conditions requires special care. Temperature differences should be minimised and heat-transfer coefficients and surface areas maximized. Electric heaters, steam jackets, or molten salt baths are often used for such purposes. Separate heating or cooling circuits and controls are used with inlet and oudet lines to minimize end effects. Pressure or thermal transients can result in longer Hved transients in the individual catalyst pellets, because concentration and temperature gradients within catalyst pores adjust slowly. 

Other techniques include oxidative, steam atmosphere (33), and molten salt (34) pyrolyses. In a partial-air atmosphere, mbber pyrolysis is an exothermic reaction. The reaction rate and ratio of pyrolytic filler to ok products are controlled by the oxygen flow rate. Pyrolysis in a steam atmosphere gives a cleaner char with a greater surface area than char pyroly2ed in an inert atmosphere however, the physical properties of the cured compounded mbber are inferior. Because of the greater surface area, this pyrolytic filler could be used as activated carbon, but production costs are prohibitive. Molten salt baths produce pyroly2ed char and ok products from tine chips. The product characteristics and quantities depend on the salt used. Recovery of char from the molten salt is difficult. 

Heat Treatment and Heat-Transfer Salts. Mixtures of sodium nitrite, sodium nitrate, and potassium nitrate are used to prepare molten salt baths and heat-transfer media. One of the most widely used eutectic mixtures uses 40% NaN02, 7% NaNO, and 53% KNO [7757-79-1] to give a... 

The reaction temperature of 500—600°C is much lower than that required for the reductive chlorination. The volatile chlorides evolve from the molten salt bath. The boiling points of NbCl, TaCl, and WOCl He between 228 and 248°C. These compounds must therefore be separated by means of a distillation column. The chlorination of ferroalloys produces very pure tantalum pentachloride in toimage quantities. The TaCl contains less than 5 )J.g Nb/g Ta, and other metallic impurities are only amount to 1—2 lg/g Ta. 

Titanium Silicides. The titanium—silicon system includes Ti Si, Ti Si, TiSi, and TiSi (154). Physical properties are summarized in Table 18. Direct synthesis by heating the elements in vacuo or in a protective atmosphere is possible. In the latter case, it is convenient to use titanium hydride instead of titanium metal. Other preparative methods include high temperature electrolysis of molten salt baths containing titanium dioxide and alkalifluorosiUcate (155) reaction of TiCl, SiCl, and H2 at ca 1150°C, using appropriate reactant quantities for both TiSi and TiSi2 (156) and, for Ti Si, reaction between titanium dioxide and calcium siUcide at ca 1200°C, followed by dissolution of excess lime and calcium siUcate in acetic acid. 

Cerous bromide [14457-87-5] CeBr, and praseodymium bromide [13536-53-3] PrBr, are claimed to be suitable for a molten salt bath used for the reduction of uranium oxide by magnesium (16). PrBr is claimed to be alight filter in a cathode ray tube (17). 

Electroplated Metals and Alloys. The metals electroplated on a commercial scale from specially formulated aqueous solutions iaclude cadmium, chromium, cobalt, copper, gold, iadium, iron, lead, nickel, platinum-group metals, silver, tin, and ziac. Although it is possible to electroplate some metals, such as aluminum, from nonaqueous solutions as well as some from molten salt baths, these processes appear to have achieved Httie commercial significance. 

Thermal stability increases with increasing atomic weight, as expected. Nitrates have been widely used as molten salt baths and heat transfer media, e.g. the 1 1 mixture LiNOs. KNOs melts at 125 C and the ternary mixture of 40% NaN02, 7% NaNOs and 53% KNO3 can be used from its mp 142 up to about 600 C. 

NaN02, in addition to its use with nitrates in heat-transfer molten-salt baths, is much used in the production of azo dyes and other organo-nitrogen compounds, as a corrosion inhibitor and in curing meats. 

As with the salts of other oxoacids, the thermal stability of nitrates varies markedly with the basicity of the metal, and the products of decomposition are equally varied/ Thus the nitrates of Group 1 and 2 metals find use as molten salt baths because of their thermal stability and low mp (especially as mixtures). Representative values of mp and the temperature (I d) at which the decomposition pressure of O2 reaches 1 atm are ... 

Fabricated articles are less commonly hot-dip aluminised now than in the past. Coatings are applied after cleaning the work, e.g. pickling in hydrochloric acid in the case of steel and then preheating. The work is then immersed in a molten salt bath, a flux or reducing atmosphere, prior to... 

The transport salt is usually eutectic NaCl-KCl but NaCl-CaC12 can also be used. As liquid plutonium metal builds up on the cathode it drips off into an annular channel surrounding the anode cup where it coalesces into a pool of metal and is recovered after the cell is cooled. The entire chemical process is performed in a molten salt bath. 

A pulse reactor system similar to that described by Brazdll, et al( ) was used to obtain the kinetic data. The reactor was a stainless-steel U-tube, composed of a l/S" x 6 preheat zone and a 3/8" X 6 reactor zone with a maximum catalyst volume of about 5.0 cm. The reactor was Immersed In a temperature controlled molten salt bath. 

Even relatively expensive salts such as RbNOj and CsNOj can be used because only a small amount of the salt is needed for investigation. (3) The temperature of the molten salt under investigation can be kept constant by a molten salt bath. 

The electrolyte is made by in situ chlorination of vanadium to vanadium dichloride in a molten salt bath. Higher valent chlorides are difficult to retain in the bath and thus are not preferred. The molten bath, which is formed by sodium chloride or an equimolar mixture of potassium chloride-sodium chloride or of potassium chloride-lithium chloride or of sodium chloride-calcium chloride, is contained in a graphite crucible. The crucible also serves as an anode. Electrolysis is conducted at a temperature about 50 °C above the melting point of the salt bath, using an iron or a molybdenum cathode and a cathode current density of 25 to 75 A dnT2. The overall electrochemical deposition reaction involves the formation and the discharge of the divalent ionic species, V2+ ... 

Oxidizing (or Kolene ). This removes scale using molten salt baths other than those containing sodium hydride. 

Salt bath descaling is the process of removing surface oxides or scale from a workpiece by immersion of the workpiece in a molten salt bath or a hot salt solution. The workpiece is immersed in the molten salt [temperatures range from 400°C to 540°C (750-1000°F)], quenched with water, and then dipped in acid. Oxidizing, reducing, and electrolytic baths are available, and the particular type needed depends on the oxide to be removed. 

One technique used in a number of facilities that utilize molten salt for metal surface treatment prior to pickling is to take advantage of the alkaline values generated in the molten salt bath in treating other wastes generated in the plant. When the bath is determined to be spent, it is in many instances manifested, hauled off-site, and land disposed. One technique is to take the solidified spent molten salt (molten salt is sold at ambient temperatures) and circulate acidic wastes generated in the facility over the material prior to entry into the waste treatment system. This in effect neutralizes the acid wastes and eliminates the requirements of manifesting and land disposal. 

The experiments were conducted batchwise in small stainless-steel pipe-bombs immersed in a molten-salt bath that was maintained at a desired, constant temperature. Pipe-bomb heat-up and quench times, on the order of 1 min each, were negligible compared with reaction times, which were on the order of 1 hr. The reagents used were obtained commercially all were of purity > 98% except for the A2-dialin which had a composition of ( 0)> 0 0 9 Q)) = 9 20, 64) mol%. The proportions of sub-... 

See Iron(III) oxide Aluminium, See other molten salt baths, thermite reactions... 

A mixture of the nitrite with sodium thiocyanate explodes on heating [1], Preparation of a molten salt bath from 0.45 kg of potassium thiocyanate (reducant) and 1.35 kg of sodium nitrite (oxidant) led to a violent explosion on melting, which... 

See METAL THIOCYANATES Oxidants, MOLTEN SALT BATHS See other REDOX REACTIONS... 

A rotary drum had been used previously to dry metal components which had been heat-treated in nitrate-nitrite molten salt baths, washed, then tumble dried with ground maize husks to absorb adhering water. When the drum was taken out of... 

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