| 摘要 |
<p>The present invention relates to a method for cleaning gas mixtures which might contain dust from a urea plant, especially off-gases from prilling towers or granulation units. In order to prevent precipitation and accretion in the cleaning unit, it is subjected to an aqueous washing solution to which formaldehyde is added before it is brought into contact with the gas mixture. Formaldehyde is preferably added in the form of formaline. The addition of formaline is regulated by the taking of pH-measurements in the washing solution; the pH being kept at pH = 6 - 8.5, preferably at pH = ca. 7, in order to obtain optimal removal of ammonia. The method is carried out in standard scrubbers in which aqueous washing solutions can be used.</p> |
