42 



MARINE PRODUCTS OF COMMERCE 



of the mixing converts the magnesium chloride into a rapidly settling, easily 

 filterable precipitate of magnesium hydroxide. 



The treated sea water flows by gravity through a concrete duct to the center 

 of large Dorr settling tanks or thickeners, each about 500 ft. in diameter. A Dorr 

 thickening mechanism in each quadrant of the tanks plows the thick magnesium 



(Courtesy Dow Chemical Co.) 



Fig. 4-3. The Dow Chemical Company's bromine plant at Freeport, Texas. In the 

 left foreground is the ethylene dibromide plant and storage tanks. Just beyond these 

 buildings is the flume leading in from the left through which sea water flows to the 

 bromine extraction units which are comprized in the two large brick buildings. These 

 buildings house the blowout towers where the chlorinated sea water is exposed to an 

 air-blast. The elaborate piping system used for dispersing the sea water can be seen 

 on the roofs of these buildings. Beyond them are the cylindrical absorption towers 

 where bromine is reclaimed from the air stream. The smaller structures which look 

 like dog houses surrounding these absorption towers are the entrainment separators or 

 filters through which the air stream finally passes into the atmosphere. The effluent sea 

 water passes out through a concrete flume which is visible beyond the intake flume. 

 The water in the upper left-hand comer is a portion of the Brazos River. 



hydroxide slurry to the center of the quadrant, whence it is pumped to a storage 

 tank. This first step removes approximately 98 per cent of the water and its com- 

 ponents and provides a slurry containing 12 per cent magnesium hydroxide and 

 practically all the magnesium and most of the calcium and bicarbonates (now 

 carbonates) of the sea water. The flow sheet (Fig. 4-4) graphically indicates the 

 various steps in the process. 



The crude magnesium hydroxide is then separated in Moore leaf-type filters. 

 When the filter cake is about 2 inches thick on the outside of the filter cloths, the 

 filter baskets are removed by a hoist from the filter pit. Air pressure is then ap- 



