Phosphates and fertilizers
Phosphates
The largest phospates producers are the USA and Morroco
The main uses of phosphates are:
Fertilizers
Animal feed
Detergents
The classic phosphate fertilizer used to be superphosphate but has been greatly replaced by more sophisticated phosphates. The world trend today is to pelleted phosphates and to soluble phosphates.
The phosphates that are recycled to nature in the form of plants or waste are very dilute, relative to the mined phosphates. Therefore, the phosphate mines will run out in time.
The production of phosphate fertilizer has high energy consumption.
Israel has a number of medium to low concentration phosphate fields in the Negev. A few of these fields have been mined out. In Israel we often have an oil shale layer under the phosphates layer. Most of the phosphate layers are not deep and surface mining can be employed. The overburden is removed first and then the phosphate layer is removed.
Concentration methods of the ore are:
Flotation
Grinding and sieving
Grinding, calcination, washing and sieving
Flash calcination
The calcination also removes the organic materials in the phosphates.
Phosphorous
The largest producers of phosphorous are the US and Russia
The production of phosphorous requires available cheap electricity.
Phosphoric acid
The common production method is by reaction of phosphates with sulfuric acid and filtration of the gypsum (Calcium sulfate) formed. The operating parameters
depend on the type of gypsum produced (anhydride, hemihydride, dihydride and mixtures)
Dihydride: P2O5 28-32% , 160-185 0F
Hemihydride: P2O5 38-42% , 200-275 0F
Hemihydride-dihydride: 200-220 0F
(extra acid and recrystallization. at 50-60 0F)
Anhydride: P2O5 42-50% , 110-240 0F
(98% sulfuric acid)
Uses of phosphoric acid:
Biological activity:
Fertilizers, food additives dor humans and cattle, soft drinks.
Chemical activity:
Baking powders. fire retardants, tooth paste.
Acidity:
Catalysts, metal cleaning and brightening. water softening, flotation.
Polarity:
Water treatment, deflocculation, detergents, plasticizers. Lubrication.
Important derivatives
Triple phosphate
Mono and di ammonium phosphate
Ammonium potassium phosphate
Ammonium polyphosphate
Fertilizers
Fertilizers are different combinations of NPK
The are sold as gross fertilizers, pellets or solutions.
The more important N fertilizers are ammonia and potassium nitrate