Methods for the production of ammonia from urea and/or biuret, and uses for NO.sub.x and/or particulate matter removal

  • US 6,077,491 A
  • Filed: 03/21/1997
  • Issued: 06/20/2000
  • Est. Priority Date: 03/21/1997
  • Status: Expired due to Term
First Claim
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1. In a method adapted to provide a pressurized gas stream useful for removing nitrogen oxides from a combustion gas stream by SNCR (Selective Non-Catalytic Reduction), or SCR (Selective Catalytic Reduction), or for particulate conditioning processes, the improvement which comprises:

  • a) feeding an aqueous solution of urea or mixtures of urea containing biuret and/or ammonium carbamate, having a concentration of about 1% to about 76% by weight of solids into a reactor and hydrolyzing the urea therein at temperatures of at least 110°

    C. up to about 300°

    C. and under pressures of about 20-500 psig, the temperature or pressure of the reaction mixture being controlled by the input of heat to the reactor to produce a gaseous product stream of ammonia, carbon dioxide and water at a rate sufficient for external use in step d), and a residual liquid phase reaction medium containing unreacted urea, biuret and/or ammonium carbamate;

    b) separating the gaseous product stream at a controlled pressure and flow rate;

    c) retaining the liquid phase reaction medium in the reactor for further conversion to gaseous ammonia and carbon dioxide, and/or recycling at least a portion of the reaction medium back into the reactor, a urea dissolver, or the feed solution to the reactor for further conversion; and

    d) withdrawing the gaseous ammonia and carbon dioxide-containing product stream and feeding it for external use at a controlled rate which is approximately the amount necessary to the demands of said external use in removing said nitrogen oxides or for particulate conditioning.

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