Deville process
Encyclopedia
The Deville process was the first industrial process used to produce alumina from bauxite
.
The Frenchman Henri Sainte-Claire Deville invented the process in 1859. It is sometimes called the Deville-Pechiney
process.
It is based on the extraction of alumina with sodium carbonate
.
The first stage is the calcination of the bauxite at 1200°C with sodium carbonate
and coke
. The alumina is converted in sodium aluminate
. Iron oxide remains unchanged and silica forms a polysilicate.
In the second stage sodium hydroxide solution is added, which dissolves the sodium aluminate, leaving the impurities as a solid residue. The amount of sodium hydroxide solution needed depends upon the amount of silica present in the raw material. The solution is filtered off; carbon dioxide
is bubbled through the solution, causing aluminium hydroxide
to precipitate, leaving a solution of sodium carbonate. The latter can be recovered and reused in the first stage.
The aluminium hydroxide is calcined to produce alumina.
The process was used in France at Saindres until 1923 and in Germany and Great Britain until the outbreak of the Second World War.
It has now been replaced by the Bayer process
.
Bauxite
Bauxite is an aluminium ore and is the main source of aluminium. This form of rock consists mostly of the minerals gibbsite Al3, boehmite γ-AlO, and diaspore α-AlO, in a mixture with the two iron oxides goethite and hematite, the clay mineral kaolinite, and small amounts of anatase TiO2...
.
The Frenchman Henri Sainte-Claire Deville invented the process in 1859. It is sometimes called the Deville-Pechiney
Pechiney
Pechiney SA was a major aluminium conglomerate based in France. The company was acquired in 2003 by the Alcan Corporation, headquartered in Canada...
process.
It is based on the extraction of alumina with sodium carbonate
Sodium carbonate
Sodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...
.
The first stage is the calcination of the bauxite at 1200°C with sodium carbonate
Sodium carbonate
Sodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...
and coke
Coke (fuel)
Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...
. The alumina is converted in sodium aluminate
Sodium aluminate
Sodium aluminate is an important commercial inorganic chemical. It works as an effective source of aluminium hydroxide for many industrial and technical applications. Pure sodium aluminate is a white crystalline solid having a formula variously given as NaAlO2, NaAl4 , Na2O·Al2O3, or Na2Al2O4...
. Iron oxide remains unchanged and silica forms a polysilicate.
In the second stage sodium hydroxide solution is added, which dissolves the sodium aluminate, leaving the impurities as a solid residue. The amount of sodium hydroxide solution needed depends upon the amount of silica present in the raw material. The solution is filtered off; carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
is bubbled through the solution, causing aluminium hydroxide
Aluminium hydroxide
Aluminium hydroxide, Al3, ATH, sometimes erroneously called Hydrate of alumina, is found in nature as the mineral gibbsite and its three, much more rare forms, polymorphs: bayerite, doyleite and nordstrandite. Closely related are aluminium oxide hydroxide, AlO, and aluminium oxide, Al2O3,...
to precipitate, leaving a solution of sodium carbonate. The latter can be recovered and reused in the first stage.
The aluminium hydroxide is calcined to produce alumina.
The process was used in France at Saindres until 1923 and in Germany and Great Britain until the outbreak of the Second World War.
It has now been replaced by the Bayer process
Bayer process
The Bayer process is the principal industrial means of refining bauxite to produce alumina .Bauxite, the most important ore of aluminium, contains only 30–54% alumina, Al2O3, the rest being a mixture of silica, various iron oxides, and titanium dioxide. The alumina must be purified before it can...
.