Thomas flour

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Thomas flour ( Thomas posphat) is a phosphate-rich fertilizer that is produced as a by-product of iron and steel production .

Manufacturing

Together with his cousin, the chemist Percy Carlyle Gilchrist , Sidney Gilchrist Thomas invented a process for the production of iron and steel from phosphorus-rich iron ore in 1876/77 , the Thomas process named after him . Industrial steel production using this process was introduced in England in May 1879 and in Germany in September 1879.

In this now rarely used method for iron and steel production, to phosphorus pentoxide (P 2 O 5 oxidized) phosphorus -attached as a supplement limestone slagged ( "slag") and comes finely ground under the name Thomas flour or slag as phosphate fertilizers in the trade.

It has not been proven whether Sidney Thomas also patented the use of Thomas flour as a fertilizer . In Germany, at the end of the 1870s , Gerhard Hoyermann began attempts to break down the phosphorus-containing blast furnace slag from the Ilseder Hütte in order to obtain a phosphate fertilizer from it. When the Peiner Walzwerk introduced the Thomas process in 1882, Hoyermann, together with the plant, took over the grinding and sale of all the Thomas slag. Since 1884 he had been producing Thomas flour in his factory in large quantities, which he could easily sell because the demand for this phosphate fertilizer was constantly increasing and up until this point he was the only manufacturer who brought Thomas flour onto the market in Germany.

Structure and salary

Thomas flour is a Ca silico phosphate with the approximation formula Ca 3 (PO 4 ) 2 · (Ca 2 SiO 4 ) with 15% P 2 O 5 and 45% CaO, as well as additions of iron , manganese , magnesium and chromium .

application

Phosphorus is a major nutritional element in plant nutrition . Thomas phosphate has a less rapid initial effect than superphosphate , but is easy to mobilize. The best fertilizing effect unfolds with a slightly acidic soil pH . Since the steel industry now processes almost exclusively low-phosphate ores, the inexpensive Thomas flour has practically disappeared from the market. The contamination of Thomas flour with the heavy metal chromium is also problematic.

See also

literature

Web links

Individual evidence

  1. https://www.deutsche-biographie.de/gnd137637489.html#ndbcontent
  2. W. Triebel and R. Nowack: Manufacture of melt phosphate fertilizer with hygienic processing and destruction of urban waste . In: Ministry of Culture (Hrsg.): Research reports of the state of North Rhine-Westphalia . No. 858 . Westdeutscher Verlag, Cologne and Opladen 1960 ( limited preview in Google book search).
  3. Barbara Dittrich, Ralf Klose: Heavy metals in fertilizers. In: Series of publications by the Saxon State Agency for Agriculture. Number 3, 2008 ISSN  1861-5988