Salt caking

The burning of the ligneous portion of the black Hquor produces sufficient heat in the furnace to sustain flash drying of residual moisture, salt-cake reduction, and chemical smelting. The heat in the gas passing through the furnace, boiler, and economi2er produces steam for power and process. 

Decomposition of Metal Chlorides by Acids. Two commercial processes employing the acidic decomposition of metal chlorides are the salt—sulfuric acid process and the Hargreaves process. Although these processes are declining in importance, they are used mainly because of the industrial demand for salt cake [7757-82-6] by the paper (qv) and glass (qv) industries. In the United States, however, Httle HCl is produced this way. 

Whereas at one time the name salt cake implied a low grade material, increasingly it is used as another name for both high and low grade Na2S04. 

Common names have been given to sodium sulfate as a result of manufacturiag methods. In rayon production, by-product sodium sulfate is separated from a slurry by filtration where a 7—10-cm cake forms over the filter media. Thus rayon cake was the term coiaed for this cake. Similarly, salt cake, chrome cake, phenol cake, and other sodium sulfate cakes were named. Historically, sulfate cakes were low purity, but demand for higher purity and controlled particle size has forced manufacturers either to produce higher quaUty or go out of busiaess. Sodium sulfate is mined commercially from three types of mineral evaporites thenardite, mirabilite, and high sulfate brine deposits (see Chemicals FROMBRINe). 

Sodium aluminum. sulfate. This product is now being successfully calcined in rotary Idlns. In this process, the salt cake is broken up just before it enters the Idln. Calcination is for the purpose of driving off the combined water (45 percent) and sulfuric acid (3 percent). Temperatures employed are approximately 800 K. 

Clay (see bentonite. Biller s earth, kaolin, and Salt cake, dry, coarse 85 D27... 

Flour, wheat. 35-40 A36K5 Sodium sulfate (see salt cake) ... 

FIG. 23-43 Reactors for solids, (a) Temperature profiles in a rotary cement lain, (h) A multiple hearth reactor, (c) Vertical lain for lime burning, 55 ton/d. (d) Five-stage fluidized bed lime burner, 4 by 14 m, 100 ton/d. (e) A fluidized bed for roasting iron sulfides. (/) Conditions in a vertical moving bed (blast furnace) for reduction of iron oxides, (g) A mechanical salt cake furnace. To convert ton/d to kg/h, multiply by 907. 

Hexafluoro-2-phenyl-2-propanol may be recovered from mother liquors, recovered solvent, and the KBr salt cake by extracting the mixture with aqueous base. Neutralization of the aqueous phase gives the alcohol (13-23 g.) which is purified by distillation. 

Commercially, hydrogen chloride is obtained either as a by-product in the manufacture of salt cake from sodium chloride, or by allowing chlorine produced as a by-product in electrolytic processes to react with hydrogen in the presence of activated charcoal. It is also formed as a byproduct in the manufacture of phenol. 

The action of cone H2SO4 on metal bromides or iodides (analogous to the salt-cake process of HCl) causes considerable oxidation of the product HX but cone H3PO4 is satisfactory. Dehydration of the aqueous acids with P2O5 is a viable alternative, DBr and DI are obtained by reaction of D2O on PBr3 and PI3 respectively. 

The classic salt-cake method was introduced with the Leblanc process towards the end of the eighteenth century and is still used to produce HCl where rock-salt mineral is cheaply available (as in the UK Cheshire deposits). The process is endothermic and takes place in two stages ... 

The Hargreaves process (late 19th C) is a variant of the salt-cake process in which NaCl is reacted with a gaseous mixture of SO2, air and H2O (i,e, H2SO4 ) in a self-sustaining exothermic reaction ... 

Antifoams to reduce the risk of carryover employed emulsions of castor oil and similar substances. Caustic embrittlement was avoided by the use of quebracho tannins, chile niter (sodium nitrate), and salt cake (sodium sulfate), which was later discredited as an inhibitor. 

In order to reuse the CaO CaCl2 salt cake, the CaO must be removed from the matrix, thus liberating fresh CaCl2 solvent. 

Rates also do not include a variety of special charges (i.e., bridge tolls) that are sometimes applicable. The chart for dry bulk commodities approximates cost of trucking items such as alum, calcium chloride,coal-tar pitch, phosphate, potash, soda ash, sodium silicate, salt cake and urea. 

Black ash One of the two processes comprising the Leblanc process for making sodium carbonate the other is the Salt-cake process. The heart of the process was a rotating kiln made of cast iron, known as a revolver. Invented by G. Elliot and W. Russel in St. Helens,... 

The addition of a small amount of nitric acid vapor or nitric oxide accelerates the process. Invented by J. Hargreaves and T. Robinson in Widnes in 1870, in order to provide sodium sulfate for the Leblanc process, circumventing the need for the sulfuric acid used in the salt-cake section of that process. Reportedly still in use in 1984. 

Leblanc (Also written LeBlanc and Le Blanc). An obsolete, two-stage process for making sodium carbonate from sodium chloride. In the first stage, the salt cake process, salt was heated with sulfuric acid, yielding sodium sulfate (salt cake) and gaseous hydrogen chloride ... 

Mannheim (1) A process for making hydrochloric acid by roasting sulfuric acid and sodium chloride together in a closed cast iron furnace equipped with a plough. The byproduct sodium sulfate, known as salt cake, may be reciystallized after neutralization and filtration, and used as a detergent ingredient. A potassium variant is used in those locations where native potassium chloride can be found. 

Salt-cake One of the two processes comprising the Leblanc process for making sodium carbonate. Salt-cake was the colloquial name for sodium sulfate. 

The checkers found it necessary to dislodge and break up the cake of magnesium salts that formed on the walls of the reaction flask. If this precaution was not observed, a substantial amount of product occluded in the salt cake was not recovered during the washing process. 

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