Rectisol method

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The Rectisol process is a physical gas cleaning process to remove unwanted (especially for downstream systems) gas components such as carbon dioxide , hydrogen sulfide , but also HCN, COS or ammonia from the raw gas produced with the aid of the washing medium methanol . The Rectisol process was developed independently by the Linde and Lurgi companies in the middle of the 20th century . However, patents and trademarks are used together today.

process

The Rectisol process usually consists of 3 to 4 process steps, namely the absorption of hydrogen sulfide, COS and HCN, the absorption of carbon dioxide, the desorption of carbon dioxide (coarse regeneration) and the desorption of the remaining absorbed gas components in the hot regeneration. The absorption takes place under a pressure of 30 to 60 bar and at around −40 ° C.

  • Absorption of hydrogen sulfide (also COS, HCN or ammonia): With the help of cold methanol, which is slightly loaded with carbon dioxide, these gas components are removed from the raw gas in a high scrubbing tower by absorption.
  • Absorption of carbon dioxide: With the help of regenerated, cold methanol, which is slightly loaded with carbon dioxide, carbon dioxide is removed from the raw gas by absorption in a tall scrubbing tower.
  • Desorption of carbon dioxide: The carbon dioxide is separated again from the loaded methanol over several stages, mainly by decompression and stripping gases. The desorption of the carbon dioxide cools the methanol further. The carbon dioxide is relatively pure and can be used in other chemical processes.
  • Heat regeneration: The gases dissolved in the methanol such as hydrogen sulfide, COS, HCN and ammonia, as well as the remaining carbon dioxide are separated again by heating in a distillation column . The exhaust gas containing hydrogen sulfide must be treated in a downstream Claus plant.

The heat generated during absorption must, for. B. be compensated by the use of a refrigeration system . The purified raw gas can, for. B. can be used as synthesis gas in other chemical processes.

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