Solvay process
The Solvay process or ammonia - soda process is a chemical process for the production of sodium carbonate ( Na2CO3). It was developed in 1865 by Ernest Solvay and replaced the previously used Leblanc process.
Worldwide most important producer is the chemical group Solvay with seven million tpa sodium carbonate ( 2010), which are mainly implemented on the main detergent ingredient sodium.
Material balance
The process goes from the cheap and available in large quantities raw materials Lime ( " calcium carbonate " ) and brine ( " sodium chloride " ), whose reaction to soda and calcium chloride
But not voluntarily takes longer since the back reaction on the starting materials, calcium carbonate and sodium chloride
Is thermodynamically favored. For realizing the forward reaction is therefore the Solvay process, a further substance, ammonia, brought into play, which then is omitted in the final mass balance again: For the Solvay process works as a chemical cycle process, in which the added ammonia in a closed loop remains and environmental impact of the order of Leblanc process can be avoided.
A disadvantage, however, also the Solvay process remains, namely that it consumes large amounts of water and per kilogram of soda still about 1 kilograms unverwendbares calcium chloride into drains, and thus into rivers and oceans, emits. Including about 1 million tons of calcium chloride, figurative three complete freight trains daily at 1 million tons of soda per year to 1000 tons.
The procedure in detail
The individual steps of the method are:
1 The lime is burnt:
2 carbon dioxide is introduced together with ammonia in a concentrated brine. Here, drops of sodium bicarbonate, which is separated from the resulting solution of ammonium chloride.
3 The sodium hydrogen carbonate is heated to about 200 ° C, whereby water and carbon dioxide to escape. What remains is then the product of soda. This process is referred to as calcination ( calcination ).
4 in the fourth step, the ammonia is recovered and supplied to step 2: