The Solvay process is the major industrial process for producing soda ash (sodium carbonate) from salt brine and limestone. It involves four main chemical reactions: 1) carbon dioxide and ammonia react to form sodium bicarbonate and ammonium chloride, 2) sodium bicarbonate is converted to sodium carbonate, 3) limestone is converted to calcium oxide and carbon dioxide, and 4) calcium oxide reacts with sodium chloride to regenerate the ammonia and produce calcium chloride and sodium carbonate. The principal byproducts are calcium chloride solution and residual calcium carbonate wastes.

2. • The Solvay process, also
referred to as the ammonia-
soda process, is the major
industrial process for the
production of soda ash (
sodium carbonate). The
ammonia-soda process was
developed into its modern form
by Ernest Solvay during the
1860s. The ingredients for this
process are readily available
and inexpensive: salt brine
(from inland sources or from
the sea) and limestone (from
mines).

3. The Solvay process results in soda ash (predominantly sodium carbonate
(Na2CO3)) from brine (as a source ofsodium chloride (NaCl)) and from
limestone (as a source of calcium carbonate (CaCO3)).[2] The overall process
is:
2 NaCl + CaCO3 → Na2CO3 + CaCl2
The actual implementation of this global, overall reaction is intricate. [3][4][5] A
simplified description can be given using the four different, interacting chemical
reactions illustrated in the figure. In the first step in the process,carbon dioxide
(CO2) passes through a concentrated aqueous solution of sodium chloride
(NaCl) and ammonia(NH3).
NaCl + CO2 + NH3 + H2O → NaHCO3 + NH4Cl

4. • Soda ash is used in many
industrial processes, and its
production is sometimes used as
an indicator of economic health.
The principal current uses include:
• Glass making: More than half the
worldwide production of soda ash
is used to make glass. Bottle and
window glass (Soda-lime glass) is
made by melting a mixture of
sodium carbonate, calcium
carbonate and silica sand (
silicon dioxide (SiO2)).
• Water treatment: Sodium
carbonate is used to soften water
(precipitates out Mg2+ and
Ca2+ carbonates). This is used
both industrially and domestically
(in some washing powders).

5. • The name "soda ash" is based on
the principal historical method of
obtaining alkali, which was by using
water to extract it from ashes.
Wood fires yielded potash and the
active ingredient
potassium carbonate
• The word "soda" (from the Middle
Latin) originally referred to certain
plants that grow in salt marshes; it
was discovered that the ashes of
these plants yielded the useful
alkali "soda ash."
.

6. • Variations in the Solvay • Variations in the Solvay
process have been process have been
proposed for carbon
sequestration. One idea proposed to convert
is to react carbon carbon dioxide
dioxide, produced emissions into sodium
perhaps by the carbonates, but carbon
combustion of coal, to
form solid carbonates sequestration by calcium
(such as sodium or magnesium
bicarbonate) that could carbonates appears
be permanently stored, more promising .
thus avoiding carbon
dioxide emission into
the atmosphere .

7. • The principal byproduct of the
Solvay process is
calcium chloride (CaCl2) in
aqueous solution. The process
has other waste and byproducts
as well. Not all of the limestone
that is calcined is converted to
quicklime and carbon dioxide (in
reaction II); the residual calcium
carbonate and other components
of the limestone become wastes.
In addition, the salt brine used by
the process is usually purified to
remove magnesium and calcium
ions, typically to form
carbonates; otherwise, these
impurities would lead to scale in
the various reaction vessels and
towers. These carbonates are
additional waste products.