gypsum

详情

 Combined water  *9.9 min
Caso*2h2o                  *5 min
Cao                               *0.5 – *3%
So4                                *3.5 **6
Mgo                                 .1 max
Sio2                                  .*5 max
Al2o3=fe2o3                         .*5 max
Cl                                             .**8 max

General

Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4•2H2O. It is found in alabaster
Gypsum is moderately water-soluble (~2.0–2.5 g/L at *5 °C) and, in contrast to most other salts, it exhibits a retrograde solubility, becoming less soluble at higher temperatures. When the crystal lattice is heated it loses liquid water molecules to evaporation and thus gains solidity.
, Gypsum is hydrated calcium sulfate formed by the evaporation of brines , near to sea then hydration ,
- it have several kind :
*- gypsite : which is earth precipitate , not clear with soil .
*- selenite : which is the best in crystal form .
*- alabaster : sculptural use .
*- rocky gypsum .                   

treatment :
by calcinations plant , that the ore have some impurities like silica or sand , caco3 which can remove by crushing in two  steps low crushing and then hammer crushing to be in lenses size , after that grinding the ore to fine particles , then beneficiation by washing to remove the impurities which dissolved with remove organic impurities by flotation , then drying and in the end the kiln of  calcinations .

uses :
*- calcinated  gypsum is about *5 % of gypsum uses that we heat the gypsum to **0 degree which remove water and become hemi hydrated gypsum that called plaster of paris , it used in wall plaster , wall lining ,  plaster board , wall board , tiles for ceikings , partitions. Thermal isolation , regulator to moisture measurements .
*- add Uncalcined gypsum crushed from 3 to 6 % to produce Portland cement so solidification speed become low .
*- gypsum contain ****0 % sulfur produce ammonium sulfate which act as natural fertilizer .
*- glass industry to easily remove the gases .
*- fine gypsum use in resin industry , paper filler , in soil used in drilling petroleum well .
• by heating to ***3 degree , calcium sulfide form which produce sulfuric acid and lime .
• A binder in fast-dry tennis court clay.
• Plaster of Paris (surgical splints; casting moulds; modeling).
• A wood substitute in the ancient world; for example, when wood became scarce due to deforestation on Bronze Age Crete, gypsum was employed in building construction at locations where wood was previously used.[*9]
• A tofu (soy bean curd) coagulant, making it ultimately a major source of dietary calcium, especially in Asian cultures which traditionally use few dairy products.
• Adding hardness to water used for homebrewing.
•  A component of Portland cement used to prevent flash setting of concrete.
• Soil/water potential monitoring (soil moisture tension).
• A common ingredient in making mead.
• In the medieval period it was mixed, by scribes and illuminators, with lead carbonate (powdered white lead) to make gesso which was applied to illuminated letters and gilded with gold in illuminated manuscripts.
• In foot creams, shampoos and many other hair products.
• Impression plasters in dentistry