• US 20100316553A1
  • Filed: 11/26/2008
  • Published: 12/16/2010
  • Est. Priority Date: 11/26/2007
  • Status: Active Grant
First Claim
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1. A method for extracting a highly purified ammonium salt and highly purified methanol from a secondary condensate containing an ammonia/ammonium-containing methanol/water mixture, comprising:

  • obtaining the methanol/water mixture from stripping a contaminated primary condensate derived from a digestion house during a delignification of lignocellulose material to cellulose pulp with an alkaline cooking liquor, and/or from evaporation of cooking waste liquor,acidifying the secondary condensate with an acid having an ability to form an ammonium salt with the ammonium contained in the secondary condensate, subjecting the mixture of the secondary condensate and acid to heat,expelling methanol and volatile sulphur-containing substances in gas form transferring the methanol and volatile sulphur-containing substances to a condenser,condensing the methanol while the volatile sulphur-containing substances remain in gas form, separately removing a liquid phase and a gas phase from the condenser,adding the acid to the mixture and circulating the mixture,while circulating the mixture, subjecting the mixture to heating to a temperature above a boiling point of the methanol but below a boiling point of both the added acid and water, the temperature being within a range of 70-105°

    C.,a re-circulation flow of the circulating mixture being at least 2-15 fold that of an inflow of the secondary condensate,passing the circulating mixture through an apparatus having an indirect heat exchanger combined with a storage volume fitted with a gas collection device,a net inflow of water via the secondary condensate and the addition of acid maintaining a concentration of ammonium salt at 1-20% below a level at which ammonium salt is precipitated,the re-circulation of the mixture optimizing the step of expelling the methanol and the volatile sulphur-containing substances from the mixture, withdrawing 5-50%, of the circulating mixture from the re-circulation flow, increasing a proportion of water in the mixture by at least 2-5 fold compared to a proportion of water in the incoming secondary condensate, for collection in a container,stirring and/or circulating the collected mixture with a high water content to expel at least 80% of a remaining methanol and at least 95% of remaining volatile sulphur-containing substancesadding an oxidizing agent to a recovered liquid methanol, andconverting remaining liquid soluble malodorous sulphur-containing substances to mainly odourless substances.

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