Staatsmijnen-Otto process

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). 

Typical operating data for the Staatsmijnen-Otto process are presented in Table 9-3. These data were obtained at a plant operated by the Societe Carbochimique at Tertre, Belgium. The plant consists of two parallel installations, each composed of a contactor and regenerator, and one final-purification installation, also containing a contactor and regenerator. 

The sodium ferrite/ferrate solution is very alkaline and lends to absorb other acid gases such as HCN, CO2. and S02- HCN is a weak acid that reacts with the alkaline solution to form NaCN by a reversible acid/base reaction. Since it is not destroyed (as is H2S) the NaCN builds up in the solution until the vapor pressure of HCN over the solution is high enough to impede absorption. At this point most of the HCN in the feed gas leaves the absorber with the product gas. A small fraction of the HCN will react with solution components to form NaSCN and ferric ferrocyanide (Prussian blue). This fetrocyanide complex is identical to the oxygen carrier employed in the Staatsmijnen-Otto process, and contributes to the oxidation of hydrogen sulfide to elemental sulfur. 

Staatsmijnen-Otto Also known as the Pieters process, after the inventor, H.A.J. Pieters. A process for removing hydrogen sulfide from coal gas by scrubbing with an aqueous solution containing a suspension of iron cyanide complexes known as iron blue. The product is elemental sulfur, which separates as a froth and is purified by heating with water in an autoclave. Staatsmijnen is a Dutch producer of smokeless fuels, which has also given its name to a briquetting 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. 

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