Ammonium Sulphate Production on Industrial Scale

A process for the production of crystalline ammonium sulfate in an industrial scale plant, wherein the plant comprises

• a Beckmann rearrangement reaction section,
• a neutralization section,
• a first liquid-liquid separation section,
• a first and a second extraction section,
• a first solvent recovery section,
• a first and a second evaporative type crystallization section, and
• a first liquid-solid separation section;
• wherein the method comprises the steps of:
• a) charging components
• (i) sulfuric acid and/or oleum;
• and
• (ii) cyclohexanone oxime
• to the Beckmann rearrangement reaction section and reacting the same to form a mixture comprising ε-caprolactam;
• b) discharging the resulting mixture comprising ε-caprolactam from the Beckmann rearrangement reaction section to the neutralization section;
• c) adding ammonia and water to the mixture comprising ε-caprolactam in the neutralization section, whereby a neutralized Beckmann rearrangement mixture is obtained that comprises a first aqueous ammonium sulfate phase and an aqueous ε-caprolactam phase, both of which comprise organic components as impurities;
• d) separating the first aqueous ammonium sulfate phase and the aqueous ε-caprolactam phase obtained in the neutralization section in the first liquid-liquid separation section;
• e) treating the first aqueous ammonium sulfate phase obtained in step d) by
• e.1) extracting the first aqueous ammonium sulfate phase with a first organic solvent in the first extraction section, whereby a phase comprising first organic solvent and ε-caprolactam, and an extracted first aqueous ammonium sulfate phase are obtained;
• e.2) charging the extracted first aqueous ammonium sulfate phase to the first solvent recovery section, wherein first organic solvent is recovered and a recovered first aqueous ammonium sulfate phase is obtained;
• e.3) charging the recovered first aqueous ammonium sulfate phase to the first evaporative type crystallization section and performing evaporative type crystallization therein to obtain crystalline ammonium sulfate and mother liquor in the first evaporative type crystallization section, wherein the mother liquor is an aqueous ammonium sulfate phase enriched in organic components compared to the recovered first aqueous ammonium sulfate phase entering the first evaporative type crystallization section;
• e.4) discharging mother liquor from the first evaporative type crystallization section;
• and
• e.5) discharging a slurry comprising crystalline ammonium sulfate from the first evaporative type crystallization section and charging it to the first liquid-solid separation section to recover crystalline ammonium sulfate;
• f) treating the aqueous ε-caprolactam phase obtained in step d) by
• f.1) extracting the aqueous ε-caprolactam phase in the second extraction section with a second organic solvent, whereby a phase comprising second organic solvent and ε-caprolactam, and a second aqueous ammonium sulfate phase comprising organic components are obtained;
• wherein
• the mother liquor that is discharged from the first evaporative type crystallization section in step e.4);
• and/or
• (ii) the second aqueous ammonium sulfate phase comprising organic components that is obtained in step f.1)
• are/is charged to the second evaporative type crystallization section, wherein evaporative type crystallization is performed so that a three-phase system occurs, which comprises the following phases:
• (1) a liquid oily phase comprising organic components;
• (2) a crystalline ammonium sulfate phase;
• and
• (3) a liquid aqueous ammonium sulfate comprising phase;
• (iii) recovering at least the liquid oily phase from said three-phase system.