Autopurification process

The differences between the individual iron-cyanide complex processes stem from the type of complex selected and the method of regeneration. In two processes, that of the Gesellschaft fur Kohlentechnik and the Fischer process, alkaline aqueous solutions of potassium ferricyanide and ferrocyanide are used, and regeneration is carried out by contact with air and electrolysis, respectively. The other two processes of this category, the Staatsmijnen-Otto and the Autopurification processes, employ suspensions of complexed ferric-ferro-cyanide compounds in alkaline solutions that are regenerated by air contact. The latter two processes are essentially identical, although they were developed independently in 1945 in the Netherlands and in England, respectively. 

The iron-cyanide processes have not been employed extensively on an industrial scale, and only a few publications describing their operation have appeared. The Fischer (1932) process has been described by Mueller (1931) and Thau (1932). The Staatsmijnen-Otto process has been discussed in detail, especially with respect to its complex chemistry, by Pieters and van Krevelen (1946). The operation of an Autopurification process plant has been reviewed by Graggs and Arnold (1947). 

Another shortcoming of the process was the large amount of air required for solution regeneration. The plant is equipped with a Uill regenerating tower, and an air volume equal to about 15% of the gas volume treated is required for adequate regeneration. However, the most serious finding of this study came from a comparative cost analysis which indicated that, at the time of the study, the Autopurification process was not competitive with dry-box purification. 

Autopurification A wet-scrubbing process for removing hydrodrogen sulfide from coke-oven gas. The scrubbing liquor was an ammoniacal suspension of ferric ammonium ferro-cyanide. The process was developed by ICI, Billingham, UK, in the 1930s and 40s, but was abandoned in 1947. 

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