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Manufacturing processes

Soda ash is one of the most widely used large-scale products of basic chemistry. Nowadays more than two thirds of its output belong to ammonia (Solvay) process, which uses sodium chloride salt, limestone or chalk as raw materials, whereas is used as an auxiliary substance. The varieties of ammonia process applied today are as follows:

1) Primary traditional Solvay method with minor peculiarities. Ammonia remains in process cycle, being recovered with lime milk.
2) Less widely used is the Akzo Nobel method. As distinct from traditional Solvay, here ammonia is recovered with dry lime. In 1958–2009 this process was operable in the Netherlands. Now its application is limited to China and two Indian plants. The engineering of a soda ash plant built in Brazil since 1971 is based on this method.
3) Combined ammonia (ammonium chloride) process with simultaneously obtained commercial ammonium chloride. This process is widely used in China (45% of all soda ash capacities in 2008), partially used by Central Glass in Japan. Small plants exist in India (Japanese project) and in Germany (BASF). A large plant operating this process is under  construction in Indonesia since 1995 (Chinese project).

So called cyclic ammonia process using sold salt, with intermediate separation of solid ammonium chloride (New Asahi method), which is subsequently decomposed with lime milk, is not applied any more. Asahi Glass company that developed this process closed in 2003 its second (and the last) 350 000 tpa soda ash plant at Kitakyushu, Japan, where this process was operated since early 1970s.

About 30% of the world’s soda ash is produced from natural soda contained raw materials, significant stocks of which have only a limited number of countries. Large-scale extraction of natural soda ash takes place in USA, China, Turkey, Kenya, Botswana. Small-size facilities may be also found in Russia, Ethiopia, Nigeria, and Chad.

Some other processes exist that permit commercial manufacture of soda ash; in total they possess 1,5% of world output:

1) Complex processing of nepheline ore (Russia);
2) thermal treatment of caprolactam plant alkaline effluents;
3) carbonation of caustic soda (used rarely);
4) cross recovery of chemicals at some cellulose and paper plants where cellulose is simultaneously obtained by sulfate and sulfite processes.

The least expense of materials and utilities in manufacture of high quality soda ash (with reduced chloride content and increased apparent density) is found in USA where it is produced from natural soda-containing minerals.

According to NIOCHIM’s evaluation global soda ash manufacture output made 54 700 000 t in 2012.

1) Ammonia soda – 76%

  • Solvay Process – 47%
  • Hou Process – 27%
  • Dry Lime Process – 2%

2) Natural soda – 23%
3) Nepheline soda – 1%

China and USA are the leaders of soda ash production.

Structure of global soda ash production