Hargreaves 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. 

The Hargreaves Process. This process, which follows the scheme given by equation 27, is exothermic. 

This process or a variation called the Hargreaves process is also used in areas where sulfuric acid is available as a by-product or where co-product HCl is needed for the production of other chemicals. 

This is called the Hargreavesprocess. Only a minor amount of sodium sulfate is made in the United States using the Hargreaves process, but both the Hargreaves and the Mannheim processes are used widely in the test of the wodd. Table 4 hsts U.S. producers and capacity information for natural and synthetic sulfate in 1992. 

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 ... 

Hargreaves process, of sodium sulfate production, 20 626 22 866-867, 868 Harmine, 2 92... 

Hydrochloric acid also is made by the Hargreaves process in which a mixture of salt, sulfur dioxide, oxygen, and water are heated at elevated temperatures, between 430 to 540°C. The reaction is exothermic and becomes self-sustaining ... 

In Hargreaves process, which is a slight variation of the Mannheim method, potassium sulfate is made by heating a mixture of potassium chloride, sulfur dioxide, air and water ... 

Sodium sulfate is synthesized by the Mannheim process or Hargreaves process. Manheim s process is based on GlaubePs reaction between sulfuric acid and sodium chloride ... 

Hargreaves process also was developed to produce hydrochloric acid. It is a variation of Mannheim s method. In this method, sulfur dioxide is used instead of sulfuric acid. The reaction is as follows ... 

By-product of chlorination of benz or other hydrocarbons b) By the action of sulfuric acid on common salt or c) By Hargreaves process which is described in Ref 3, p 585-R... 

Hargreaves process - pOTASSIUMCOMPOUNDS] (Vol 19) - [SODIUMCOMPOUNDS - SODIUM SULFATES] (Vol 22) -for hydrogen chloride [HYDROGEN CITLORIDE] (Vol 13)... 

HARGREAVES PROCESS. The manulacture of sodium. sulfate (salt cake t front sodium chloride and sulfur dioxide. A mixture of sulfur dioxide and air is passed over briquettes of sodium chloride in a countercurrent manner to produce sodium sullale and hydrogen chloride. This process accounts far only it small amount of the salt cake produced in the L.S. 

Sodium sulfate is produced from natural sources and as byproduct in a variety of processes including ascorbic acid, battery recycling, resorcinol, silica pigment, viscose rayon, and sodium bichromate. Other salt cake production processes are based on the reaction of sulfuric acid (Mannheim process) or S02 and air (Hargreaves process) with sodium chloride. The Mannheim process is no longer in use in the United States. U.S. Hargreaves capacity is very limited. However, both processes are used widely in the rest of the world. 

Sodium sulfate is also formed as a byproduct in the manufacture of hydrogen chloride by the reaction of sodium chloride with sulfuric acid at high temperatures (Mannheim process, Hargreaves process and the fluidized bed process). At the end of the I970 s the Mannheim process was used to produce about half of the sodium sulfate produced in Europe. However, these processes are hardly operated any more. 

The Hargreaves process produces K2SO4 directly from KCl by passing SO2, air, and water vapor through beds of KCl briquettes. 

Derivation (1) By treatment of potassium chloride either with sulfuric acid or with sulfur dioxide, air, and water (Hargreaves process) (2) by fractional crystallization of a natural sulfate ore (3) from salt-lake brines. 

Derivation (1) Purification of natural sodium sulfate from deposits or brines (2) by-product of hydrochloric acid manufacture from salt and sulfuric acid, 2NaCl + H,S04 2HC1 + Na,S04 (3) byproduct of phenol manufacture (caustic fusion process) (4) Hargreaves process. 

Hydrogen chloride is produced by a reaction analogous to Eq. (18) using NaCl as the source of chloride. Alternatively, sodium chloride may be treated with a mixture of sulfur dioxide, air, and water (the Hargreaves process) ... 

During the Industrial Revolution, demand for alkaline substances such as soda ash increased, and Nicolas Leblanc developed a new industrial-scale process for producing the soda ash. In the Leblanc process, salt was converted to soda ash, using sulfuric acid, limestone, and coal, giving hydrogen chloride as by-product. Initially, this gas was vented to air, but the Alkali Act of 1863 prohibited such release, so then soda ash producers absorbed the HCl waste gas in water, producing hydrochloric acid on an industrial scale. Later, the Hargreaves process was developed, which is similar to the Leblanc process... 

Production capacity for sodium sulfate, or salt cake, has remained fairly constant over the last decade, with the number of producing plants continuing to decline. Over half of the U.S. supply of Na2S04 is produced from natural brines. Most of the remainder is by-product derived from the production of viscose rayon, sodium dichromate, and sulfonation process phenol. Salt cake produced in the manufacture of HCl from salt by the action of sulfuric acid (Mannheim process), or SO2 and air (Hargreaves process), is on the decline. 

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