WO2025128151A1

WO2025128151A1 - Systems and methods for ammonia purification

Info

Publication number: WO2025128151A1
Application number: PCT/US2024/032613
Authority: WO
Inventors: Martin Taylor; Arlin PETERS; Charles Kimtantas
Original assignee: Bechtel Energy Technologies and Solutions Inc
Current assignee: Bechtel Energy Technologies and Solutions Inc
Priority date: 2024-06-05
Filing date: 2024-06-05
Publication date: 2025-06-19
Anticipated expiration: 2026-12-05
Also published as: EP4662177A1; WO2025128151A8

Abstract

Systems and methods for NH3 purification using a sour water feed stream with a higher concentration of NH3 than H2S to produce a purified acid gas stream, a purified NH3 vapor stream and an environmentally safe stripped water stream without adding more acid and/or base.

Description

SYSTEMS AND METHODS FOR AMMONIA PURIFICATION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application and U.S. Patent Nos. 10,022,650, 10,702,799, 10,850,226, 10,266,418, 10,456,735, 10,843,122, and 10,315,153, which are each incorporated herein by reference, are commonly assigned to Bechtel Energy Technologies and Solutions, Inc.

FIELD OF THE INVENTION

[0002] The present invention generally relates to systems and methods for ammonia purification. More particularly, the present invention relates to ammonia purification using a sour water feed stream with a higher concentration of ammonia (NH3) than hydrogen sulfide (H2S) to produce a purified acid gas stream, a purified NH3 vapor stream and an environmentally safe stripped water stream.

BACKGROUND OF THE INVENTION

[0003] Conventional technology separately recovers H2S and NH3 from sour water using an H2S stripper and an NH3 stripper, which is sometimes referred to as a two-column sour water stripping process. A two-column sour water stripping process typically includes four main processing stages: 1) degassing and feed preparation; 2) H2S stripping; 3) NH3 stripping; and 4) NH3 purification and liquefaction. This process yields acid gas (predominantly H2S and CO2) with less than 50 ppmw NH3, a purified gaseous and/or liquid NH3 product and stripped water that may be suitable for reuse or discharged to the environment if the pH of the sour water feed is near neutral. If, however, the pH of the sour water feed is not near neutral (i.e., the sour water feed has a higher concentration of NH3 than H2S), then significant amounts of other acids (e.g., hydrochloric, sulfurous, sulfuric, nitric and potentially other acids) must be added to the sour water stream before the H2S stripping stage to bind the NH3 and separate the H2S and CO2 from the sour water stream. Likewise, comparable amounts of other bases (e.g., sodium hydroxide, potassium hydroxide and potentially other bases) must be added during the NH3 stripping stage to bind the other acids added to tire sour water stream and release the NH3. After adding so much acid and base, the resulting stripped water is unsuitable for discharge to the environment because it contains a high concentration of salts.

[0004] Referring now⁷ to FIGS. 1A and IB, a schematic diagram of a conventional tw o-column sour w ater stripping system illustrates the four processing stages. The following pressures and temperatures are exemplary and only for purposes of illustration.

Degassing and Feed Preparation:

[0005] Sour water feeds 102 from a single or several sources are combined with a recycle stream 104 from the NH3 stripper 106, which are cooled and passed through a degasser 108 where dissolved hydrogen (H2), methane (CH4) and other light hydrocarbons are removed as a hydrocarbon vapor stream 105. The sour water feeds 102 include dissolved NH3 and H2S. The recycle stream 104 includes rich NH3, which helps keep acid gases in solution in the degasser 108, thereby minimizing the release of acid gas and possible air pollution. The degassed sour water stream 109 is sent to a deoiler 103, which removes free oil from the degassed sour water stream 109 to produce a degassed/deoiled sour water stream 107. The degassed/deoiled sour water stream 107 is pumped to a feed preparation tank 110, which serves to attenuate flow' rate and composition changes while also providing the opportunity to remove entrained oil and solids. The feed preparation tank 110 produces a processed sour w ater stream 111, which is pumped to a feed coalescer unit 112 that filters solids remaining in the processed sour water stream 111 and further separates entrained oil to produce a hydrocarbon liquid 113 and a deoiled sour water stream 115. The deoiled sour water stream 115 is sent to a feed/product exchanger 114, which acts as a heat exchanger to heat the deoiled sour water stream 115 and cool the NH3 stripper bottoms stream 132 to produce a heated deoiled sour water stream 116 and the stripped water stream 134. In this manner, the components comprising the NH3 stripper bottoms stream 132, stripped water stream 134 and the components comprising the deoiled sour water stream 115, heated deoiled sour water stream 116 are. respectively, the same but may have different concentrations and temperatures. The heated deoiled sour water stream 116 is then sent to an H2S stripper 118.

H2S Stripping:

[0006] The H2S stripper 118 contains trays or packing (not shown) that the heated deoiled sour water stream 116 flows through and around to separate H2S from the heated deoiled sour water stream 116. A cooled reflux water stream (e.g. water wash) 136 is used remove heat and suppress evolution of gaseous NH3 in the H2S stripper. A reboiler 137 acts as a heat exchanger to provide the energy required to i) heat the heated deoiled sour water stream 116 and the cooled reflux water stream 136 to a preferred temperature; and ii) strip out H2S from the heated deoiled sour water stream 116. The resulting H2S stripper overheads stream 120 is sent to a knock out drum 138 to substantially remove any entrained droplets and produce H2S stream 126. The H2S stream 126 is of high purity and is an excellent feed for a sulfur recovery unit (SRU) or a sulfuric acid plant. It contains a negligible amount of NH3 (less than 50 ppmw) and very little hydrocarbons since the sour water feeds 102 have been degassed. The H2S stream 126 is available at about 100-180 psig and 100-120°F. The resulting H2S stripper bottoms stream 130, which contains NH3 and some H2S, is sent directly to the NH3 stripper 106. NH3 Stripping:

[0007] The NH3 stripper 106 is a steam re-boiled, refluxed distillation column. In the NH3 stripper 106, essentially all NH3 and any remaining H2S are removed from the H2S stripper bottoms stream 130, which leaves the NH3 stripper 106 as an NH3 stripper bottoms stream 132. The NH3 stripper bottoms stream 132 is sent to the feed/product exchanger 114 where heat is exchanged with the deoiled sour water stream 115 and theNH3 stripper bottoms stream 132 is cooled to form the stripped water stream 134. The containment levels of H2S and NH3 in the stripped water stream 134 may be tailored to individual requirements and is typically 10-50 ppmw NH3 and 1-25 ppmw H2S. The stripped water stream 134 is available at about 100-200°F. In the NH3 stripper 106, essentially all NH3 and any remaining H2S are removed from the H2S stripper bottoms stream 130, which leaves the NH3 stripper 106 as an NH3 stripper overheads stream 133. The NH3 stripper overheads stream 133 is sent to an overhead condenser where it is converted to an NH3 vapor stream and an NH3 liquid stream. A knock out drum 139 separates the NH3 vapor stream 140 and the NH3 liquid stream 150. A portion of the NH3 liquid stream 150 is returned as reflux to the NH3 stripper 106 and another portion of the NH3 liquid stream 150 forms the recycle stream 104. A reboiler 141 acts as a heat exchanger to provide the energy required to remove NH3 and any remaining H2S. The NH3 vapor stream 140 is an NH3-rich gas, which may be processed in a variety of ways.

NH3 Purification and Liquefaction:

[0008] Referring now to FIG. IB, the NH3 vapor stream 140 is sent to a water wash 142 to remove residual amounts of H2S and some hydrocarbons. This step is also referred to as water scrubbing, which produces a scrubbed NH3 vapor stream 160. If NH3 recovery is not desired or economic, the scrubbed NH3 vapor stream 160 may be incinerated. In most cases, however, it is desirable to further purify the scrubbed NH3 vapor stream 160 to produce either an anhydrous liquid NH3 stream 170 or an aqueous NH3 stream 180 suitable for commercial use. In order to further purify the scrubbed NH3 vapor stream 160, the scrubbed NH3 vapor stream 160 is sent to a caustic wash 144 to remove residual contaminants including some hydrocarbons. This step is also referred to as caustic scrubbing, which produces a double scrubbed NH3 vapor stream 162 and may be necessary when problems are expected with process upsets, carbon dioxide, or complex sulfur compounds (e.g. mercaptans or disulfides). The double scrubbed NH3 vapor stream 162 may be sent to either a compressor 146 or a refrigeration unit 148 to produce the anhydrous liquid NH3 stream 170, which contains a negligible amount ofH2S (less than 5 ppmw). The anhydrous liquid NH3 stream 170 is available at about 200 psig and 100°F if liquefied by compression and at atmospheric pressure and about -26 F if liquefied by cooling. Cooling water and/or a refrigerant may be used to exchange heat with the double scrubbed NH3 vapor stream 162. The double scrubbed NH3 vapor stream 162 may also be sent to an NH3 absorber 149, which is essentially another water wash, to produce the aqueous NH3 stream 180, which contains a negligible amount of sulfur (no more than about 2ppmw). The aqueous NH3 stream 180 is available at about 35 psig and 100°F.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The detailed description is described below with reference to the accompanying drawings in which like elements are referenced with like numerals, and in which: [0010] FTGS. 1A-1B are schematic diagrams illustrating a conventional two- column sour water stripping system.

[0011] FIG. 2 is a schematic diagram illustrating one embodiment of an NH3 purification system capable of producing a purified acid gas stream, a purified NH3 vapor stream and an environmentally safe stripped water stream using a sour water feed stream with a higher concentration of NH3 than H2S.

[0012] FIG. 3 is a schematic diagram illustrating another embodiment of an NH3 purification system capable of producing a purified acid gas stream, a purified NH3 vapor stream and an environmentally safe stripped water stream using a sour water feed stream with a higher concentration of NH3 than H2S.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The subject matter of the present disclosure is described with specificity, however, the description itself is not intended to limit the scope of the disclosure. The subject matter thus might also be embodied in other ways, to include different structures, steps and/or combinations similar to and/or fewer than those described herein, in conjunction with other present or future technologies. Although the term “step’’ may be used herein to describe different elements of methods employed, the term should not be interpreted as implying any particular order among or between various steps herein disclosed unless otherwise expressly limited by the description to a particular order. Other features and advantages of the disclosed embodiments will be or will become apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional features and advantages be included within the scope of the disclosed embodiments. Further, the illustrated figures described herein are only exemplary and are not intended to assert or imply any limitation with regard to the environment, architecture, design, or process in which different embodiments may be implemented. To the extent that temperatures and/or pressures are referred to in the following description, those conditions are merely illustrative and are not meant to limit the disclosure. All streams described herein are carried by physical lines.

[0014] The systems and methods disclosed herein overcome the disadvantages encountered by conventional NH3 purification processes by using a sour water feed stream with a higher concentration of NH3 than H2S to produce a purified acid gas stream, a purified NH3 vapor stream and an environmentally safe stripped water stream without adding more acid and base.

[0015] In one embodiment, a system is disclosed for ammonia purification, which comprises: i) an ammonia stripper for separating a sour water feed stream comprising ammonia and hydrogen sulfide into an ammonia stripper vapor stream and an ammonia stripper liquid stream; ii) a first heat exchanger positioned upstream of the ammonia stripper and enclosing a portion of the sour water feed stream and a portion of the ammonia stripper liquid stream for heating the sour water feed stream and cooling the ammonia stripper liquid stream to produce a stripped water stream; iii) a second heat exchanger for converting the ammonia stripper vapor stream to a two-phase ammonia stream; iv) a knock-out drum for separating the two-phase ammonia stream into an ammonia vapor stream and an ammonia liquid stream; and v) a water wash for removing hydrogen sulfide and carbon dioxide from the ammonia vapor stream and producing a purified ammonia vapor stream and a rich water stream comprising hydrogen sulfide and carbon dioxide. [0016] In another embodiment, a method is disclosed for ammonia purification, which comprises: i) heating a sour water feed stream comprising ammonia and hydrogen sulfide in a heat exchanger using an ammonia stripper liquid stream to produce a heated sour water feed stream; ii) cooling the ammonia stripper liquid stream in the heat exchanger using the sour water feed stream to produce a stripped water stream; iii) separating the heated sour water feed stream into an ammonia stripper vapor stream and an ammonia stripper liquid stream; iv) converting the ammonia stripper vapor stream to a two-phase ammonia stream; v) separating the two-phase ammonia stream into an ammonia vapor stream and an ammonia liquid stream; and vi) removing hydrogen sulfide and carbon dioxide from the ammonia vapor stream to produce a purified ammonia vapor stream and a rich water stream comprising hydrogen sulfide and carbon dioxide.

[0017] In yet another embodiment, a system is disclosed for ammonia purification, which comprises: i) an ammonia stripper for separating a sour water feed stream comprising ammonia and hydrogen sulfide into an ammonia stripper vapor stream and an ammonia stripper liquid stream; ii) a first heat exchanger positioned upstream of the ammonia stripper and enclosing a portion of the sour water feed stream and a portion of the ammonia stripper liquid stream for heating the sour water feed stream and cooling the ammonia stripper liquid stream to produce a stripped water stream; iii) a cooler for cooling another ammonia stripper liquid stream withdrawn from the ammonia stripper above the ammonia stripper liquid stream; iv) a pump for pumping a portion of the another ammonia stripper liquid stream back to the ammonia stripper; and v) a water wash for removing hydrogen sulfide and carbon dioxide from the ammonia stripper vapor stream and producing a purified ammonia vapor stream and a rich water stream comprising hydrogen sulfide and carbon dioxide. [0018] In yet another embodiment, a method is disclosed for ammonia purification, which comprises: i) heating a sour water feed stream comprising ammonia and hydrogen sulfide in a heat exchanger using an ammonia stripper liquid stream to produce a heated sour water feed stream; ii) cooling the ammonia stripper liquid stream in the heat exchanger using the sour water feed stream to produce a stripped water stream; iii) separating the heated sour water feed stream in an ammonia stripper into an ammonia stripper vapor stream and an ammonia stripper liquid stream; iv) withdrawing another ammonia stripper liquid stream from the ammonia stripper; v) cooling the another ammonia stripper liquid stream; and vi) removing hydrogen sulfide and carbon dioxide from the ammonia stripper vapor stream to produce a purified ammonia vapor stream and a rich water stream comprising hydrogen sulfide and carbon dioxide.

[0019] Referring now to FIG. 2, a schematic diagram illustrates one embodiment of an NH3 purification system 200 capable of producing a purified acid gas stream 274, a purified NH3 vapor stream 242 and an environmentally safe stripped water stream 237 using a sour water feed stream 202 with a higher concentration of NH3 than H2S.

[0020] A sour water feed stream 202 is mixed with a cooled H2S stripper liquid stream 278 and, optionally, an NH3 liquid stream 230. The mixed stream is then passed through a degasser 208 where dissolved hydrogen (H2), methane (CH4), other light hydrocarbons, H2S and CO2 may be removed through a hydrocarbon vapor stream 205 to produce a degassed sour water feed stream 209. The degassed sour water feed stream 209 is sent to a deoiler 203, which removes free oil from the degassed sour water feed stream 209 to produce a degassed/deoiled sour water feed stream 207. The degassed/deoiled sour water feed stream 207 is sent by means of a first pump 206 to a feed preparation tank 210, which serves to attenuate flow rate and composition changes while also providing the opportunity to remove entrained oil and solids. The feed preparation tank 210 produces a processed sour water feed stream 211, which is sent to a feed coalescer unit 212 by means of a second pump 213. The feed coalescer unit 212 filters solids remaining in the processed sour water feed stream 211 and further separates entrained oil to produce a deoiled sour water feed stream 215. The deoiled sour water feed stream 215 is sent to a feed/product exchanger 214, which acts as a heat exchanger to heat the deoiled sour water feed stream 215 and cool an NH3 stripper liquid stream 232 to produce a heated/ deoiled sour water feed stream 216 and an environmentally safe stripped water stream 234 that may be further cooled by a first heat exchanger 235 using a coolant to produce a chilled stripped water stream 237. The chilled stripped water stream 237 may be discharged to the environment and/or reused. In this manner, the components comprising the NH3 stripper liquid stream 232 and the stripped water stream 234 are effectively the same but may have different pressures and/or temperatures. Likewise, the components comprising the deoiled sour water feed stream 215 and the heated/deoiled sour water feed stream 216 are effectively the same but may also have different pressures and/or temperatures. The heated/deoiled sour water feed stream 216 may be further processed by NH3 stripping.

[0021] The heated/deoiled sour water feed stream 216 may be sent to an NH3 stripper 218, which is a steam re-boiled, refluxed distillation column. Essentially all the NH3 and any remaining H2S and CO2 are separated from the heated/deoiled sour water feed stream 216 in the NH3 stripper 218, which produces the NH3 stripper liquid stream 232 and an NH3 stripper vapor stream 220. The NH3 stripper liquid stream 232 leaves the bottom of the NH3 stripper 218 and is sent to the feed/product exchanger 214. The contaminant levels of H2S, CO2 and NH3 in the stripped water stream 234 may be tailored to individual requirements and is typically 10-50 ppmw NH3, 1-25 ppmw H2S and essentially no CO2. The stripped water stream 234 is available at about 100-200°F. The

NH3 stripper vapor stream 220 leaves the top of the NH3 stripper 218 and is sent to a second heat exchanger 222 where a coolant is used to convert the NH3 stripper vapor stream 220 to a two phase NH3 stream 224 that is sent to a knock-out drum 226. The knock-out drum 226 separates the two phase NH3 stream 224 into an NH3 vapor stream 228 and the NH3 liquid stream 230. A portion of the NH3 liquid stream 230 is returned as reflux to the NH3 stripper 218 and another portion of the NH3 liquid stream 230 may be, optionally, recycled back to mix with the sour water feed stream 202 and the cooled H2S stripper liquid stream 278 using a third pump 236. A reboiler 238 acts as a heat exchanger to provide the energy required to remove NH3 and any remaining H2S. The NH3 vapor stream 228 is an NH3- rich gas, which is further processed.

[0022] The NH3 vapor stream 228 may be sent to a water wash 240 for purification and to preferentially remove residual amounts of H2S and some hydrocarbons. The water wash 240 produces a purified NH3 vapor stream 242 and a rich water stream 244 comprising H2S and CO2. The rich water stream 244 may be pumped using a fourth pump 246 i) through a third heat exchanger 262 back to the water wash 240 and/or ii) optionally through another feed/product exchanger 264 for further processing. The third heat exchanger 262 uses a coolant to chill the recycled rich water stream 244 pumped back to the water wash 240. Counterflow of the NH3 vapor stream 228 and the chilled stripped water stream 237 removes a majority of the H2S and CO2. The NH3 vapor stream 228, the chilled stripped water stream 237 and the rich water stream 244 entering the water wash 240 may each be divided into two or more streams that enter the water wash 240 at different locations for optimizing the counterflow and removing a majority of the H2S and CO2. The feed/product exchanger 264 acts as a heat exchanger to heat the rich water stream 244 and cool an H2S stripper liquid stream 276 to produce a heated rich water stream 248 and the cooled H2S stripper liquid stream 278.

[0023] The heated rich water stream 248 comprising NH3, H2S and CO2 may be sent to an H2S stripper 266 to separate the H2S and CO2 from the water. The heated rich water stream 248 that enters the H2S stripper may be divided into two or more streams that enter the H2S stripper 266 at different locations. The H2S stripper 266 contains trays or packing that the heated rich water stream 248 flows through and around to separate H2S and CO2 from the heated rich water stream 248. The chilled stripped water stream 237 may be used to remove NH3 from the exiting vapors. A reboiler 268 acts as a heat exchanger to provide the energy required to i) heat the heated rich water stream 248 and the chilled stripped water stream 237 to preferred temperatures; and ii) strip out H2S and CO2 from the heated rich water stream 248. The H2S stripper 266 produces an H2S stripper vapor stream 270, which is sent to a knock-out drum 272 to substantially remove any entrained droplets and produce a purified acid gas stream 274. Because the acid gas stream 274 contains negligible NH3 (less than 50 ppmw) and very little hydrocarbons, it is an excellent feed for a sulfur recovery unit (SRU) or a sulfuric acid plant. The acid gas stream 274 is available at about 50-200 psig and 100-120°F. The H2S stripper 266 also produces the H2S stripper liquid stream 276, which contains NH3, H2S and CO2 from the bottom of an H2S stripper 266.

[0024] Referring now to FIG. 3, a schematic diagram illustrates another embodiment of an NH3 purification system 300 capable of producing a purified acid gas stream 274, a purified NH3 vapor stream 242 and an environmentally safe stripped water stream 237 using a sour water feed stream 202 with a higher concentration of NH3 than H2S. [0025] The NH3 purification system 300 is a modification of the NH3 purification system 200 illustrated in FIG. 2 and, therefore, includes many of the same components. Alternatively, however, the NH3 stripper vapor stream 220 may be sent directly to the water wash 240 for purification in the same manner as the NH3 vapor stream 228 described in reference to FIG. 2. Additionally, a pump-around subsystem design may be used with the NH3 stripper 218 instead of the overhead condensing subsystem design illustrated in FIG. 2. The pump-around subsystem uses a third pump 302 to pump another NH3 stripper liquid stream 304 from the NH3 stripper 218 through a cooler 306 that produces a cooled NH3 stripper liquid stream 308. = The cooled NH3 stripper liquid stream 308 is recycled back to the NH3 stripper 218 and, optionally, to the cooled H2S stripper liquid stream 278 where it is mixed thus, forming a combined liquid stream 310 comprising NH3 and H2S. The sour water feed stream 202 may, therefore, be mixed with the cooled H2S stripper liquid stream 278 or, optionally, the combined liquid stream 310.

[0026] While the present disclosure has been described in connection with presently preferred embodiments, it will be understood by those skilled in the art that it is not intended to limit the disclosure of those embodiments. It is therefore, contemplated that various alternative embodiments and modifications may be made to the disclosed embodiments without departing from the spirit and scope of the disclosure defined by the appended claims and equivalents thereof.

Claims

1. A system for ammonia purification, which comprises: an ammonia stripper for separating a sour water feed stream comprising ammonia and hydrogen sulfide into an ammonia stripper vapor stream and an ammonia stripper liquid stream; a first heat exchanger positioned upstream of the ammonia stripper and enclosing a portion of the sour water feed stream and a portion of the ammonia stripper liquid stream for heating the sour water feed stream and cooling the ammonia stripper liquid stream to produce a stripped water stream; a second heat exchanger for converting the ammonia stripper vapor stream to a two- phase ammonia stream; a knock-out drum for separating the two-phase ammonia stream into an ammonia vapor stream and an ammonia liquid stream; and a water wash for removing hydrogen sulfide and carbon dioxide from the ammonia vapor stream and producing a purified ammonia vapor stream and a rich water stream comprising hydrogen sulfide and carbon dioxide.

2. The system of claim 1, wherein the sour water feed stream includes a higher concentration of the ammonia than the hydrogen sulfide.

3. The system of claim 1 , wherein a portion of the rich water stream is fluidly connected to a hydrogen sulfide stripper.

4. The system of claim 3, further comprising a third heat exchanger for chilling another portion of the rich water stream recycled back to the water wash.

5. The system of claim 4, further comprising a fourth heat exchanger for chilling the stripped water stream with a coolant to produce a chilled stripped water stream.

6. The system of claim 5, wherein the chilled stripped water stream is fluidly connected to at least one of the water wash and a hydrogen sulfide stripper.

7. The system of claim 6, wherein the hydrogen sulfide stripper is fluidly connected to the chilled stripped water stream for removing hydrogen sulfide and carbon dioxide from the portion of the rich water stream and producing a vapor stream comprising hydrogen sulfide and carbon dioxide, and a liquid stream comprising ammonia and residual hydrogen sulfide and carbon dioxide.

8. The system of claim 7. further comprising another knock-out drum for removing entrained droplets from the vapor stream and producing a purified acid gas stream.

9. The system of claim 7, wherein the liquid stream is in fluid communication with the sour water feed stream.

10. The system of claim 6, wherein the chilled stripped water stream is fluidly connected to the water wash and the ammonia vapor stream is fluidly connected to the water wash below the chilled stripped water stream and above the rich water stream.

11. The system of claim 1. wherein a portion of the ammonia liquid stream is fluidly connected to the ammonia stripper and another portion of the ammonia liquid stream is in fluid communication with the sour water feed stream.

12. A method for ammonia purification, which comprises: heating a sour water feed stream comprising ammonia and hydrogen sulfide in a heat exchanger using an ammonia stripper liquid stream to produce a heated sour water feed stream; cooling the ammonia stripper liquid stream in the heat exchanger using the sour water feed stream to produce a stripped water stream; separating the heated sour water feed stream in an ammonia stripper into an ammonia stripper vapor stream and the ammonia stripper liquid stream; converting the ammonia stripper vapor stream to a two-phase ammonia stream; separating the two-phase ammonia stream into an ammonia vapor stream and an ammonia liquid stream; and removing hydrogen sulfide and carbon dioxide from the ammonia vapor stream to produce a purified ammonia vapor stream and a rich water stream comprising hydrogen sulfide and carbon dioxide.

13. The method of claim 12, wherein the sour water feed stream includes a higher concentration of the ammonia than the hydrogen sulfide.

14. The method of claim 12, wherein the rich water stream is fluidly connected to at least one of the water wash and a hydrogen sulfide stripper.

15. The method of claim 14, further comprising chilling the rich water stream fluidly connected to the water wash.

16. The method of claim 15. further comprising chilling the stripped water stream with a coolant to produce a chilled stripped water stream.

17. The method of claim 16, wherein the chilled stripped water stream is fluidly connected to at least one of the water wash and a hydrogen sulfide stripper.

18. The method of claim 17, further comprising removing hydrogen sulfide and carbon dioxide from the rich water stream using the chilled stripped water stream to produce a vapor stream comprising hydrogen sulfide and carbon dioxide and a liquid stream comprising ammonia and residual hydrogen sulfide and carbon dioxide.

19. The method of claim 18, further comprising removing entrained droplets from the vapor stream and producing a purified acid gas stream.

20. The method of claim 18, wherein the liquid stream is in fluid communication with the sour water feed stream.

21. The method of claim 12, wherein the heated sour water feed stream is separated into the ammonia stripper vapor stream and the ammonia stripper liquid stream using the ammonia liquid stream.

22. A system for ammonia purification, which comprises: an ammonia stripper for separating a sour water feed stream comprising ammonia and hydrogen sulfide into an ammonia stripper vapor stream and an ammonia stripper liquid stream; a first heat exchanger positioned upstream of the ammonia stripper and enclosing a portion of the sour water feed stream and a portion of the ammonia stripper liquid stream for heating the sour water feed stream and cooling the ammonia stripper liquid stream to produce a stripped water stream; a cooler for cooling another ammonia stripper liquid stream withdrawn from the ammonia stripper above the ammonia stripper liquid stream; a pump for pumping a portion of the another ammonia stripper liquid stream back to the ammonia stripper; and a water wash for removing hydrogen sulfide and carbon dioxide from the ammonia stripper vapor stream and producing a purified ammonia vapor stream and a rich water stream comprising hydrogen sulfide and carbon dioxide.

23. The system of claim 22, wherein the sour water feed stream includes a higher concentration of the ammonia than the hydrogen sulfide.

24. The system of claim 22, wherein a portion of the rich water stream is fluidly connected to a hydrogen sulfide stripper.

25. The system of claim 24, further comprising a second heat exchanger for chilling another portion of the rich water stream recycled back to the water wash.

26. The system of claim 25, further comprising a third heat exchanger for chilling the stripped water stream with a coolant to produce a chilled stripped water stream.

27. The system of claim 26, wherein the chilled stripped water stream is fluidly connected to at least one of the water wash and a hydrogen sulfide stripper.

28. The system of claim 27, wherein the hydrogen sulfide stripper is fluidly connected to the rich water stream and the chilled stripped water stream for removing hydrogen sulfide and carbon dioxide from the portion of the rich water stream and producing a vapor stream comprising hydrogen sulfide and carbon dioxide, and a liquid stream comprising ammonia and residual hydrogen sulfide and carbon dioxide.

29. The system of claim 28, further comprising another knock-out drum for removing entrained droplets from the vapor stream and producing a purified acid gas stream.

30. The system of claim 28, wherein the liquid stream is in fluid communication with at least one of the sour water feed stream and another portion of the another ammonia stripper liquid stream.

31. The system of claim 27, wherein the chilled stripped water stream is fluidly connected to the water wash, the rich water stream is fluidly connected to the water was and the ammonia stripper vapor stream is fluidly connected to the water wash below the chilled stripped w ater stream and above the rich water stream.

32. A method for ammonia purification, which comprises: heating a sour water feed stream comprising ammonia and hydrogen sulfide in a heat exchanger using an ammonia stripper liquid stream to produce a heated sour w ater feed stream; cooling the ammonia stripper liquid stream in the heat exchanger using the sour water feed stream to produce a stripped water stream; separating the heated sour water feed stream in an ammonia stripper into an ammonia stripper vapor stream and an ammonia stripper liquid stream; withdrawing another ammonia stripper liquid stream from the ammonia stripper; cooling the another ammonia stripper liquid stream; and removing hydrogen sulfide and carbon dioxide from the ammonia stripper vapor stream to produce a purified ammonia vapor stream and a rich water stream comprising hydrogen sulfide and carbon dioxide.

33. The method of claim 32, wherein the sour water feed stream includes a higher concentration of the ammonia than the hydrogen sulfide.

34. The method of claim 32, wherein a portion of the rich water stream is fluidly connected to a hydrogen sulfide stripper.

35. The method of claim 34, further comprising chilling another portion of the rich water stream recycled back to the water wash.

36. The method of claim 35, further comprising chilling the stripped water stream with a coolant to produce a chilled stripped water stream.

37. The method of claim 36, wherein the chilled stripped water stream is fluidly connected to at least one of the water wash and a hydrogen sulfide stripper.

38. The method of claim 37, further comprising removing hydrogen sulfide and carbon dioxide from the portion of the rich water stream using the chilled stripped water stream to produce a vapor stream comprising hydrogen sulfide and carbon dioxide and a liquid stream comprising ammonia and residual hydrogen sulfide and carbon dioxide.

39. The method of claim 38, further comprising removing entrained droplets from the vapor stream and producing a purified acid gas stream.

40. The method of claim 38, wherein the liquid stream is in fluid communication with at least one of the sour water stream and a portion of the another ammonia stripper liquid stream.

41. The method of claim 40, wherein the heated sour water feed stream is separated into the ammonia stripper vapor stream and the ammonia stripper liquid stream using another portion of the another ammonia stripper liquid stream.