THE REFINING OF SEA SALT 



33 



/2 salt walls 



■ ■ .--i. ^ settling tanks 



Jj;'"S„ """', 635,000 gal eactt 



10,000 ga(^ cap. ' \ " 



Mixing tank 



^ Lime a 

 lioicfdOgal cop \ --| 



To 5 Alberger systems 



Stprasejonk \ --'^/^^^ / 



Jn General service 

 ' 1 V brine pumps 

 \f \500 gp.m. eactt 

 To grainers To vacuum \ 



pan Calcium carbonate 



magnesium hydroxide^ 

 To Alberger system--' 



FLOW DIAGRAM 

 ALBERGER PROCESS 

 DIAMOND CRYSTAL SALT DIVISION / 



I 



Faed 



trine 

 heater 



{Cotirtesy Food Industries) 



Fig. 3-3. Flow diagram of Alberger salt refining system. The Alberger process em- 

 ploys a pre-heater, three pressure heaters, two gravellers, three flash evaporators and an 

 open, figure-eight shaped evaporating pan. In the pressure heaters the brine increases in 

 temperature and pressure but does not boil. In the third pressure heater, the brine 

 reaches 290° F (143.3° C), the temperature at which optimum removal of calcium 

 sulfate is effected. The brine is then passed through the gravellers where the calcium 

 sulfate precipitates. The sulfate deposits on cobble stones placed in the unit for that 

 purpose. The purified brine from the gravellers is now cooled in a series of three flashers. 

 The critical crystallizing temperature is reached in the third flasher at 226° F ( 107.8° C). 

 At this point, about half of the yield of salt crystallizes spontaneously as microscopic 

 cubes. The crystal-seeded brine is ejected into the open evaporating pan, where surface 

 evaporation of the rapidly cooling brine results in the formation of delicate, hopper- 

 shaped, flake-like crystals. The settled crystals are drawn from the pan and separated 

 from the adhering brine in a basket-type centrifuge, preceding the high temperature 

 drying operation. The drying is completed in a steam-heated, rotary, counterflow air 

 dryer, which reduces the moisture content of the salt to less than 0.1 per cent. Steam 

 from the boilers at 210 psi pressure is used to heat air for the dryers, and the condensate 

 is returned to the boiler. 



