Method for removing ammonia from a gas comprising hydrogen cyanide, ammonia and water

• US 6,872,296 B2
• Filed: 07/30/2002
• Issued: 03/29/2005
• Est. Priority Date: 07/30/2002
• Status: Expired due to Fees

• Current Assignee: Invista North America Sarl (Invista)
• Original Assignee: Invista North America Sarl (Invista)
• Inventors: Kim, Tae Hoon
• Primary Examiner(s): Phasge, Arun S.
• Application Number:
  US10/209,258
• Publication Number:
  US 20040022709A1
• Time in Patent Office: 973 Days
• Field of Search: 205/687, 423/236, 423/238
• US Class Current: 205/687
• CPC Class Codes: C01C 1/12 Separation of ammonia from gases and vapours as part of the ammonia synthesis process C01C1/04
• CPC Class Codes: C01C 3/0295 Purification

Abstract

A method for removing ammonia from a gas comprising HCN, ammonia and water, by first contacting the gas with aqueous ammonium phosphate to remove ammonia from the gas, and then passing the resulting ammonium phosphate solution through an electrolyzer to convert oxalates and formates into hydrogen and carbon dioxide.

Claims

1. A method for removing ammonia from a gas comprising HCN, ammonia and water, comprising:

a. contacting the gas with a first aqueous ammonium phosphate solution having a first ammonium ion to phosphate ion molar ratio to produce a substantially ammonia-free HCN gas and a second aqueous ammonium phosphate solution having a second ammonium ion to phosphate ion molar ratio higher than the first ratio, said second aqueous ammonium phosphate solution comprising ammonium oxalate and ammonium formate;

b. distilling the second ammonium phosphate solution to produce ammonia gas and a third ammonium phosphate solution having a third ammonium ion to phosphate ion molar ratio less than the second ratio, said third aqueous ammonium phosphate solution comprising ammonium oxalate and ammonium formate;

c. cooling said third ammonium phosphate solution to produce a fourth ammonium phosphate solution;

d. passing said fourth ammonium phosphate solution between at least one pair of electrodes having a DC voltage across said at least one pair of electrodes, capable of generating a sufficient current to oxidize said oxalate and formate to produce an oxidation product comprising carbon dioxide and hydrogen and a fifth ammonium phosphate solution that is substantially free of oxalate and formate; and

e. separating the oxidation product from the fifth ammonium phosphate solution.