Glauber s salt crystallizer

Method 2 The dye liquor is made up with 10 to 15 per cent of Glauber s salt crystals and 3 to 5 per cent of acetic acid (30 per cent). The temperature is raised to 40°C (105°F) and the goods are entered and, if possible, run for 10 to 20 minutes to equalize their pH. The dye is then added and the liquor is raised to the boil over a period of 45 minutes. Boiling is continued, and after 40 to 45 minutes exhaustion may be completed by slowly adding a further 1 to 3 per cent of acetic acid (30 per cent), 1 per cent of sulphuric acid 168°Tw(98 per cent), or 1 per cent of formic acid (85 per cent). This method would be used for dyes of the type in Table 15.5 and, if further additions of dyestuffs of this class are necessary to correct the shade, the liquor should be cooled. 

If desired, Glauber s salt crystals can be substituted when, to allow for tlic water of crystallization, two pounds are required to replace each pound of common salt. 

This example ignores the entrainment of liquor with the solids removed from the system and any wash water or solution added to improve the separation. These are important questions in process design, as is the proper water balance in the crystallizer if the best results are desired. If the purpose of the Glauber s salt crystallizer is only to concentrate the sulfate purge stream, very high quality will not be as important. 

Many diaphragm plants operate triple-salt decomposers and Glauber s salt crystallizers. In some cases, this is simply an environmental measure designed to reduce... 

Example. Washed salt from the primary centrifuge (Stream 1) drops into a leaching tank. The composition of the salt depends on the processing conditions and the amount of sulfate in the cell liquor. Here, we assume that the centrifuge cake is about 96% sohds and the amount of Na2S04 precipitated is 2.8% of the total solids (dry basis). This tank will export clear liquor to the Glauber s salt crystallizer and slurry to a salt recovery system, for return to the brine plant. The leach tank also receives mother liquor from the crystallizer (Stream 3) and a small amount of evaporator condensate (Stream 2) to... 

Example Glauber s salt crystallizer Basis 1000 kg Na2S04 removed... 

Brine containing the dissolved sodium sulfate is separated from the salt crystals in a cyclone. The underflow returns to the leaching tank. The overflow is collected in the feed tank for the Glauber s salt crystallizer. Sodium sulfate is crystallized from the liquor in a continuous vacuum cooled crystallizer. 

Processing at Sead.es Lake, California, by North American Chemical is similar to that of Texas brines. Brine is cooled to 16°C to remove borax crystals, then cooled to 4°C which precipitates Glauber s salt. This salt is then separated from its mother Hquor, melted in multi-effect vacuum crystallizers to form anhydrous sodium sulfate, and dried. Both processes produce crystals that are 99.3—99.7% pure (9). 

In Texas, brine is pumped from underground deposits. Sodium chlodde is added to bring the brine near saturation. This solution is then chilled to —8°C to crystallize Glauber s salt (71). Anhydrous Na2S04 is recovered by artificially evaporating the Hquor formed by remelting the Glauber s salt. 

J. Reich 6 also patented a process based on the calcination of the alkali fluosilicate or fluoborate with an oxide of the alkaline earths. When the calcined mass is lixiviated with water, the alkali fluoride is obtained in soln. L. Schuch 6 made sodium fluoride by boiling finely powdered cryolite with a cone. soln. of sodium hydroxide—the alumina and silica pass into soln.—sodium fluoride crystallizes from the cooling soln. Sodium silicate can be used in place of the hydroxide. F. Jean made sodium fluoride by leaching a calcined mixture of fluorspar, limestone, Glauber s salt, and charcoal. 

Henry prepared sodium and potassium bromides by boiling ferrous bromide respectively with potassium or sodium carbonate until the precipitate is brown the clear liquid was then filtered and evaporated. J. Knobloch recommended treating a mixture of ferrous bromide with milk of lime, and then with potassium sulphate if potassium bromide is desired, or with Glauber s salt if sodium bromide is to be made. The mixture is then to be boiled, the precipitated iron oxide filtered off, and the soln. evaporated, for cubic crystals of potassium bromide. This is the principle of the method employed for manufacturing potassium bromide on a large scale ... 

A soln. of 22 parts of Glauber s salt in 10 parts of hot water is poured into a flask. The liquid is cooled and twice its volume of alcohol at 40°, and sp. gr. 0 835, is poured as a layer over the aq. soln. Crystals of the heptahydrated salt, free from the decahydrated sulphate, are formed as the alcohol mixes with the water. The crystalline product can be freed from the adherent liquid by press. 

However, the majority of sodium sulfate is now obtained directly from natural salt sources. Brines with 7 to 11% sodium sulfate are used and pumped through a salt deposit to lower the solubility of the sodium sulfate so that, upon cooling, the decahydrate (Glauber s salt) will crystallize and can be separated. Heating then forms the anhydrous salt cake. 

A similar process is practiced at Searles Lake. There the brine is first carbonated and chilled to remove sodium carbonate and borax. Further chilling crystallizes Na2S04 as the hydrate, Glauber s salt, and some remaining borax. The coarse crystals of Glauber s salt are separated from the fine crystals of borax in a hydraulic classifier. The sulfate fraction is then filtered, washed, dried, and evaporated to produce anhydrous Na2S04. 

The influence of the non-complex negative ion on the stability also becomes manifest in the anhydrous crystallization, for example, of the alkaline earth fluorides, but on the other hand sodium perchlorate is NaC104.H20 while the sulphate with the double-charged anion contains ioH20 (Glauber s salt). Here other factors play a part, since the perchlorate in question is hygroscopic and is also very readily soluble. 

Sodium sulfate crystallized from solution has an attraction for iron and iron compounds and for various organics. Glauber s salt does not show this attraction and in fact rejects most impurities. Thus higher quality Na2S04 is made from Glauber s salt. 

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