Process for recovery and recycle of ammonia from a vapor stream
First Claim
1. A process for the recovery of ammonia from a vaporous stream comprising contacting said stream with a first aqueous ammonium phosphate solution comprising ammonium dihydrogen phosphate and diammonium hydrogen phosphate, having a first ratio of ammonium ions (NH4+) to phosphate ions (PO4−
- 3), thereby absorbing ammonia from said stream and forming aqueous quench bottoms having increased ratio of (NH4+) to (PO4−
3) and a depleted vapor stream comprising residual ammonia;
contacting said depleted vapor stream with a second aqueous ammonium phosphate solution comprising ammonium dihydrogen phosphate and diammonium hydrogen phosphate, and having a second ratio of ammonium ions (NH4+) to phosphate ions (PO4−
3) that is lower than the first ratio, thereby absorbing substantially all of said residual ammonia from said vapor stream and forming said first aqueous ammonium phosphate solution;
heating said aqueous quench bottoms to an elevated temperature for a time sufficient to decompose at least a portion of the diammonium phosphate and generate a vaporous ammonia stream; and
separating the ammonia from the remaining components of said vaporous ammonia stream.
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Abstract
A process for the recovery of unreacted ammonia from the effluent from a reaction zone used to produce acrylonitrile or methacrylonitrile comprising quenching the reactor effluent with an aqueous solution of ammonium phosphate in at least two stages, thereby capturing the ammonia component of the effluent. The captured ammonia may be recovered by heating the aqueous ammonium phosphate, which then may be recycled. Contaminants present in the aqueous ammonium phosphate may be removed, for example by solvent extraction or wet oxidation, prior to recycle.
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Citations
23 Claims
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1. A process for the recovery of ammonia from a vaporous stream comprising contacting said stream with a first aqueous ammonium phosphate solution comprising ammonium dihydrogen phosphate and diammonium hydrogen phosphate, having a first ratio of ammonium ions (NH4+) to phosphate ions (PO4−
- 3), thereby absorbing ammonia from said stream and forming aqueous quench bottoms having increased ratio of (NH4+) to (PO4−
3) and a depleted vapor stream comprising residual ammonia;
contacting said depleted vapor stream with a second aqueous ammonium phosphate solution comprising ammonium dihydrogen phosphate and diammonium hydrogen phosphate, and having a second ratio of ammonium ions (NH4+) to phosphate ions (PO4−
3) that is lower than the first ratio, thereby absorbing substantially all of said residual ammonia from said vapor stream and forming said first aqueous ammonium phosphate solution;
heating said aqueous quench bottoms to an elevated temperature for a time sufficient to decompose at least a portion of the diammonium phosphate and generate a vaporous ammonia stream; and
separating the ammonia from the remaining components of said vaporous ammonia stream. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 22, 23)
- 3), thereby absorbing ammonia from said stream and forming aqueous quench bottoms having increased ratio of (NH4+) to (PO4−
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17. In a process for the recovery of unreacted ammonia from a reactor effluent obtained from an ammoxidation reaction zone for the production of an unsaturated nitrile, said process comprising the steps of quenching said reactor effluent with an aqueous ammonium phosphate solution, thereby absorbing unreacted ammonia present in the reactor effluent and forming an ammonia-enriched aqueous solution richer in ammonium ions than said aqueous ammonium phosphate solution;
- heating said ammonia-enriched aqueous solution to an elevated temperature sufficient to reduce the amount of ammonium ions, thereby regenerating said aqueous ammonium phosphate solution and generating a vaporous stream containing ammonia; and
recycling said vaporous stream to the ammoxidation reaction zone, the improvement comprising quenching said reactor effluent with a first aqueous ammonium phosphate solution comprising ammonium dihydrogen phosphate and diammonium hydrogen phosphate wherein the ratio of ammonium ions (NH4+) to phosphate ions (PO4−
3) is greater than 1.3, thereby absorbing greater than about 90% of the unreacted ammonia present in the reactor effluent and forming said ammonia-enriched solution and depleted effluent comprising residual ammonia; and
contacting said depleted effluent with a second aqueous ammonium phosphate solution comprising ammonium dihydrogen phosphate and diammonium hydrogen phosphate wherein the ratio of ammonium ions (NH4+) to phosphate ions (PO4−
3) is from about 0.7 to about 1.3, thereby absorbing said residual ammonia from said reactor effluent and forming said first aqueous ammonium phosphate solution. - View Dependent Claims (18, 19, 20, 21)
- heating said ammonia-enriched aqueous solution to an elevated temperature sufficient to reduce the amount of ammonium ions, thereby regenerating said aqueous ammonium phosphate solution and generating a vaporous stream containing ammonia; and
Specification