Method and apparatus for preparing high-concentration alkali
AssigneesSulzer-Escher Wyss GmbH, Ube Industries, Ltd.
InventorsRobert Winkler, Siro Sala, Yakayuki Kobayashi, Shinjiro Yokota
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Abstract
A caustic alkali solution is concentrated to high density or high caustic alkali concentration by evaporation under high pressure at elevated temperature and expansion of the thus obtained concentrated caustic alkali solution to low pressure, preferably below atmospheric pressure. The pressure difference between the high pressure evaporator and the low pressure expansion vessel is absorbed gradually by a pressure difference absorber, preferably comprising a liquid column in a U-shaped siphon tube, so that corrosion and erosion are reduced considerably.
Claims5
A method of producing high-concentration of at least 94% caustic alkali by concentrating a caustic alkali solution by evaporation at an elevated temperature, comprising the steps of:
- concentrating the caustic alkali solution by evaporating water from the caustic alkali solution at a pressure of about 1.61 to about 2.22 bar above atmospheric pressure in a high pressure evaporation stage;
- expanding the thus obtained concentrated caustic alkali solution to a predetermined low pressure in a low pressure expansion stage;
- absorbing the pressure difference existing between said high pressure evaporation stage and said low pressure expansion stage by means of a pressure difference absorber of predetermined length;
- selecting as said pressure difference absorber of said predetermined length a liquid column disposed between said high pressure evaporation stage and said low pressure expansion stage;
- and
- maintaining a seal head to compensate for the pressure difference between the high pressure evaporation stage and the low pressure expansion stage.
Dependencies are inferred from the claim text.