TECHNICAL FIELD
The present subject matter disclosed herein, in general, relates to a system and process for recovering ammonia from fluids and gas containing hydrogen sulfide (H2S) and ammonia (NH3). In particular, the subject matter relates to a low-pressure system and process for recovering anhydrous ammonia from sour gas. BACKGROUND
Sour water, containing H2S and NH3, is predominantly produced in refinery at various locations like primary units (CDU/VDU), secondary units (HCU/FCCU), hydro-processing units (DHDT/DHDS) and in bottom-up gradation units (DCU). The produced sour water is treated in sour water stripper units (SWSU) to produce sour gas containing H2S, NH3 and H2O. The treated sour water, containing H2S (<50 ppmw) and NH3 (<50 ppmw), called as stripped sour water, is routed back to units as wash water and to effluent treatment plants (ETPs).
Sour gases are treated in sulphur recovery unit (SRU) to recover sulphur from H2S and destruct NH3 into N2 and H2O. To facilitate the trouble-free treatment of sour gases in SRU, as NH3 forms salts with H2S and creates plugging problem in SRU, H2S and NH3 are stripped separately in SWSU. Sulphur is recovered from H2S rich sour gas and NH3 in NH3 rich sour gas is destructed into N2 and H2O.
There are various processes and systems for the recovery of ammonia from the sour gas for example, ammonia is absorbed by sulfuric acid in scrubbing stage and the end product is a concentrated salt solution which is mainly used as a liquid fertilizer However, use of sulphuric acid is calls for highly exotic metallurgy and chances of corrosion are also very high. Canadian patent application, CA 2829929 Al discloses a process for eliminating hydrogen sulfide from liquid ammonia. The process comprises contacting a first liquid stream, anhydrous or aqueous, comprising ammonia and hydrogen sulfide, with a solution comprising sulfur dioxide to convert the hydrogen sulfide to thiosulfate. However, the process has some constraints. For example, exotic metallurgy is required for the use of SO2, as SO2 is highly corrosive in presence of water. Further, congealing and plugging are the major issues if process aims for the production of salt (ammonium thiosulphate).
Canadian patent application, CA 1189682 discloses a process for removing sulfur compounds from a gas stream. In the process, the gas stream containing the sulfur compounds are passed through a mass of porous material that has a metal oxide deposited upon it, and an amine. Use of amine in the process is having some complications like deposit formation due

to corrosive amine compounds, foaming due to hydrocarbons and continuous erosion of metal oxide bed into the amine system.
Therefore, there is a need in the art to develop a system and a process for separating anhydrous ammonia from sour gas. The process/system is devoid of above limitations. SUMMARY OF THE INVENTION
The present invention discloses a process for separation of anhydrous ammonia from sour gas. The process comprises the following steps:
a) introducing NH3 rich sour gas (stream A) and wash water (stream B) and contacting them counter-currently in an absorption column;
b) cooling a stream C comprising sour gas leaving the absorption column in a cooler-1, wherein stream C has higher concentration of NH3 and lower concentration of H2S compared to stream A;
c) introducing a stream of gas-liquid mixture leaving the cooler-1 into a separator-1 to separate gas stream from liquid stream;
d) compressing a stream D comprising sour gas stream leaving separator-1 in a compressor followed by cooling in a cooler-2;
e) introducing a stream E comprising a stream of gas-liquid mixture leaving the cooler-2 into a separator-2 to separate gas stream from liquid stream; and
f) treating a stream F comprising gas stream leaving the separator-2 with an adsorbent bed, in an adsorbent column, to remove traces of H2S and to recover anhydrous ammonia.
The present invention also provides a system for recovering anhydrous ammonia from the sour gas. The system comprises an absorption column, one or more coolers, one or more separators, pumps, adsorbent bed and wash water flow circuit. BRIEF DESCRIPTION OF FIGURE(S)
FIG. 1 is an illustration of a system recovering anhydrous ammonia from sour gas according to an embodiment of the present disclosure. DETAILED DESCRIPTION
Disclosed herein are a system and a process for recovering anhydrous ammonia from a sour gas. The system comprises an absorption column, one or more coolers, one or more separators, pumps, adsorbent bed and wash water flow circuit.

FIG.l illustrates an exemplary system for recovering anhydrous ammonia from the sour gas. The exemplary system comprises an absorption column. The absorption column comprises a first inlet, preferably located at the bottom part of the absorption column, through which NH3 rich sour gas stream may be introduced, and a second inlet, preferably located at the top part of the absorption column, through which the wash water stream to be introduced. The absorption column defines a volume wherein said sour gas stream contacts the said wash water stream. The absorption column further comprises a first outlet, preferably located at the top part of the said absorption column, through which a sour gas stream containing high NH3 and less H2S compared to the sour gas stream that was introduced into the said absorption column, may leave; and a second outlet, preferably located at the bottom part of the said absorption column to discharge a liquid solution of sour water rich in H2S and NH3 to a stripper. The absorption column may be made of any material suitable for feeding wash water stream and NH3 rich sour gas. In certain embodiments, the concentration of NH3 in NH3 rich sour gas is about 30%V and above. In certain embodiments, the concentration of NH3 is from about 30%V to about 90%V. The absorption column may have low pressure drop internals to minimize the pressure drop resulting from the contacting of wash water and NH3 rich sour gas and to maximize the available contact area between the said two phases (wash water and NH3 rich sour gas). Internals, made from any suitable material, may be utilized within the volume of first absorption column. To maximize available contact area between the two phases, packaging materials made from either of ceramics, metals or plastics are used. Any number of packing materials with various size, shape and performance can be utilized. The packing materials may be dumped or random packing materials, structured packing materials, grid packing materials. In certain embodiments, the absorption column comprises low pressure packed beds and a structured packing for bed material which gives efficient mass transfer at a low pressure drop across the column. The structured packing may provide a surface area in the range of 125 m2/m3 to 350 m2/m3. The adsorption column is configured in a such a way that it acts as guard bed to ensure the content of H2S in the outlet gas is <10 ppmw.
In certain embodiments, the absorption column is typically connected to a first cooler (cooler-1), wherein the temperature of the NH3 rich sour gas may be reduced. The cooler-1 comprises an inlet coupled to the first outlet of the absorption column to receive the NH3 rich sour gas. It further comprises an outlet through which a cooled NH3 rich sour gas and a liquid

solution (condensed sour water) may leave. In certain embodiments, water or steam is added upstream of cooler-1 to increase the removal efficiency of H2S from the sour gas.
In certain embodiments, the cooler-1 is connected to a first gas-liquid separator (separator-1), where the NH3 rich sour gas is further extracted from the liquid solution. The separator-1 comprises an inlet through which the cooled NH3 rich sour gas leaving the outlet of the cooler-1 may be introduced. It further comprises a first outlet through which said extracted NH3 rich sour gas may leave and a second outlet, preferably located at the bottom part of the said separator, which is connected to the absorption column, preferably at top, to discharge the liquid solution. Any gas-liquid separator may be employed in the system. In certain embodiments, the gas-liquid separator is selected from a group comprising conventional gas-liquid separators, cyclones, oil-gas separators, knock-out drums and filter separators.
The first outlet of the separator-1 is further connected to a compressor, where the NH3 rich sour gas leaving the separator-1 is compressed. The compressor may be any compressor suitable for use in compressing the gas stream entering the compressor, which may be driven by electrical, hydraulic, mechanical or pneumatic means. The compressor may include any combination of the said compressors arranged in series, in parallel, or combinations thereof. In the compressor, the gas is compressed to a pressure required to meet the pressure requirement for production of anhydrous ammonia. The compressor comprises an outlet through which a compressed NH3 rich sour gas at an increased pressure and increased temperature, may leave. In certain embodiments, the pressure increase is at least about 1 kg/cm2. In certain embodiments, the temperature of gas after compression is more than 40 °C.
The compressor is further connected to a second cooler (cooler-2), wherein the temperature of the NH3 rich sour gas may be reduced. The cooler-2 comprises an inlet coupled to the outlet of the compressor to receive the compressed NH3 rich sour gas. It further comprises an outlet through which a cooled NH3 rich sour gas and a liquid solution (condensed sour water), at a reduced pressure and reduced temperature, may leave.
The cooler-2 is further connected to a second gas-liquid separator (separator-2), where the NH3 rich sour gas is further extracted from the liquid solution. The separator-2 comprises an inlet through which the cooled NH3 rich sour gas leaving the outlet of the cooler-2 may be introduced. It further comprises a first outlet through which said extracted NH3 rich sour gas may leave and and a second outlet, preferably located at the bottom part of the said separator,

which is connected to a stripper, to discharge the liquid solution. Any gas-liquid separator may be employed in the system. In certain embodiments, the gas-liquid separator is selected from a group comprising conventional gas-liquid separators, cyclones, oil-gas separators, knock-out drums and filter separators.
In certain embodiments, the first outlet of the separator-2 is further connected to an adsorption column, wherein the H2S in the NH3 rich sour gas stream is adsorbed on an adsorbent bed. The adsorbent may be of any material capable of adsorbing H2S from the NH3 rich sour gas. In a preferred embodiment, the adsorbent comprises: a waste from a refinery application wherein said waste from a refinery application comprises a transition metal embedded material; and an oxide of a trivalent metal selected from an oxide of a transition metal wherein said transition metal is selected from the group consisting of the elements of group VIII in the periodic table.
The said adsorption column further comprises a first inlet through which the NH3 rich sour gas to be introduced. The said adsorption column further comprises a first outlet, preferably located at the top part through which pure anhydrous ammonia or anhydrous ammonia having acceptable level of H2S may be extracted. A second inlet preferably located at the bottom through which air or oxygen stream may be introduced for adsorbent bed regeneration. In the regeneration of adsorbent bed, H2S is reacted with 02/air to form elemental sulphur and to liberate some H2S. The liberated H2S is then routed to SRU.
Also, disclosed herein is a low-pressure process for recovering anhydrous ammonia from sour gas. In the process, the NH3 rich sour gas is introduced into an absorber column. In this column, said NH3 rich sour gas is counter-currently contacted with stripped sour water (wash water stream) at a predetermined temperature. The absorption column may have low pressure drop internals to minimize the pressure drop resulting from the contacting of stripped sour water and NH3 rich sour gas and to maximize the available contact area between two phases (stripped sour water and NH3 rich sour gas), and to reduce the operating pressure of upstream NH3 stripper.
After the contact of the two phases (stripped sour water and NH3 rich sour gas), the sour gas leaves from the top of the absorption column and stripped sour water, through bottom of the absorption column, is discharged to SWSU to increase NH3 recovery. Mass transfer of H2S and NH3 from sour gas to stripped sour water occurs in the absorption column. The sour gas leaving the top has significantly higher concentration of NH3 and lower concentration of H2S, compared to the gas stream that was introduced into the said absorption

column. To get the desired mass transfer between the two phases, NH3 rich sour gas from SWSU is routed to absorber column at a pressure of < 0.8-0.9 kg/cm2g and at a temperature of about 40-90 °C, and stripped sour water is routed to absorber column at a temperature of about 40-90 °C. The sour gas leaving the top of the absorption column is directed to a cooler-1 wherein the stream (sour gas) is cooled. In certain embodiments, the sour gas leaving the top of the absorption column is cooled, in the cooler-1, at a temperature of about 40 °C. In certain embodiments, water or steam is added to increase the H2S removal efficiency from sour gas.
The cooled gas stream is then introduced into a first gas-liquid separator (separator-1) as described herein. Then, the condensed water is routed to the absorption column, preferably at top part of the absorption column, to increase recovery of NH3. Thereafter, sour gas stream is compressed in a compressor. Then the compressed gas is cooled in a cooler-2. The cooled gas stream is then introduced into a second gas-liquid separator (separator-2) as described herein. Then, the condensed water is routed to SWSU to increase recovery of NH3. Thereafter, sour gas stream is treated with an adsorbent bed, in an adsorption column, to adsorb H2S and to recover anhydrous ammonia. In certain embodiments, the predetermined temperature is about 40 °C. The adsorbent may be of any material capable of adsorbing H2S from the gas stream, as described above. The gas leaving the adsorbent bed typically contains H2S (<10 ppmv), NH3 (99.6%V) and water vapor at saturation.
In certain embodiments, the concentration of H2S in the sour gas stream that was introduced into the absorption column is a maximum of about 10 %V.
In certain embodiments, the concentration of NH3 in the sour gas stream that was introduced into the absorption column is from about 30%V to about 90%V.
The temperature of gas and liquid water leaving the absorber depends on the inlet temperature and composition of the feed to the absorber. In certain embodiments, the sour gas leaving the absorber column may be cooled, in a cooler, up to <50 °C. In some instances, the gas is cooled at about 40 °C. Further, in the cooler-1, the gas pressure drop is about < 0.3 kg/cm2. In further embodiments, the gas pressure drop in both the separators is about <0.02 kg/cm2.
In certain embodiments, by the reaction with Ch/Air most of the H2S adsorbed on the adsorbent bed is converted to elemental sulphur and the remaining is liberated as H2S and H2S, is routed to SRU. Further, the load on the adsorbent bed is significantly reduced and the H2S concentration, in the gas stream, at the inlet of the adsorbent bed is < 200 ppmv.

In certain embodiments, the sour gas leaving the absorber column may be cooled, in a cooler, to about 40 °C.
In certain embodiments, the system and the process are configured to recover at least 99.9% ammonia from the sour gas.
In certain embodiments, the concentration of H2S in the anhydrous ammonia leaving the adsorbent bed is about 10 ppmv.
Certain ranges are disclosed herein with numerical values being preceded by the term "about." The term "about" is used herein to provide literal support for the exact number that it precedes, as well as a number that is near to or approximately the number that the term precedes. In determining whether a number is near to or approximately a specifically recited number, the near or approximating unrecited number may be a number which, in the context in which it is presented, provides the substantial equivalent of the specifically recited number.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning and the meaning of such terms is independent at each occurrence thereof and is as commonly understood by one of skill in art to which the subject matter herein belongs.
The singular forms "a", "an" and "the" encompass plural references unless the context clearly indicates otherwise.
As used herein, the term "comprises" or "comprising" is generally used in the sense of include, that is to say permitting the presence of one or more features or components.
As used herein the term "wash water" refers to stripped sour water, DM water and/or steam condensate.
Each embodiment is provided by way of explanation of the disclosure and not by way of limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the system, and methods described herein without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment can be applied to another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure include such modifications and variations and their equivalents. Other objects, features and aspects of the present invention are disclosed in or are obvious from, the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not to be construed as limiting the broader aspects of the present disclosure.

The present disclosure is further described with reference to the following examples, which are only illustrative in nature and should not be construed to limit the scope of the present disclosure in any manner. EXAMPLES
The process was carried out in two plants having a capacity of 19TPD (Tons Per Day) and 31TPD. The process was described herein below. EXAMPLE 1 19TPD
In this example, NH3 rich sour gas having the following composition of H2S-2.61%V, NH3-65.17%V, H20-32.22%V was used. The total flow of the gas was 1282 kg/h. Wash water was stripped sour water having the composition of H2S-O.I7 kg/hr, NH3-O.85 kg/hr, H20-3399 kg/hr.
In the process, NH3 rich gas (Stream A) from Sour Water Stripper Unit (SWSU) was fed into bottom of an absorber column with a pressure and temperature of 0.9 kg/cm2g and 90 °C respectively. In the absorber column, NH3 rich gases was counter-currently contacted with stripped sour water (Stream B) and recycle water from separator 1 (Stream H). The sour water (Stream G) generated from bottom of absorber column was routed to existing sour water stripper unit for further processing. From the top of the absorber column, H2S lean gas (Stream C) leaves. Then, steam (stream K) at 165 deg C and 4.5 kg/cm2.g was added to the stream C. Stream C was cooled up to 40 °C in a cooler-1. The gas-liquid mixture leaving the cooler-1 was separated in a separator-1. Then, the gas leaving the separator-1 (Stream D) was compressed in a compressor to push the gas for further processing. The temperature raised during compression was removed in cooler-2 by cooling up to 40 °C. The gas-liquid mixture leaving the cooler-2 (Stream E) was separated a in separator-2. The liquid stream (Stream I) leaving the bottom of separator-2 is mixed with Stream G and was routed to existing sour water stripper unit for further processing. A recycle stream comprising of ammonia, H2S and water generating in sour water stripper unit (SWSU) will comprise of remaining part of stream A Thereafter, the process gas, Stream F, leaving the seperator-2 was processed in an adsorber column to remove traces of H2S impurity in the process gas. The process gas (Stream J) leaving the adsorber column contained H2S <10 ppmv and this has NH3 content 99.6 %Wt (min.). Then, adsorbent bed in adsorber column was regenerated by Ch/Air into elemental sulphur and H2S. The H2S was routed to SRU.

Impact on upstream unit: The operating pressure of the stripper can be brought back from existing 0.9 kg/cm2g to 0.7-0.8 Kg/cm2g. The process data was shown in table 1 below. EXAMPLE 2: 31 TPD
In this example, NH3 rich sour gas having the following composition of H2S-2.58%V, NH3-65.21%V, H20-32.21%V was used. The total flow of the gas was 2083 kg/h. Wash water was stripped sour water having the composition of H2S-O.275 kg/hr, NH3-I.38 kg/hr, H2O-5523.34 kg/hr.
NH3 rich gas (Stream A) from Sour Water Stripper Unit (SWSU) was fed into bottom of the absorber column with a pressure and temperature of 0.9 kg/cm2g and 90 °C, respectively. In the absorber column, NH3 rich gases was counter-currently contacted with stripped sour water (Stream B) and recycle water from separator-1 (Stream H). The sour water (Stream G) generated from bottom of absorber column was routed to existing sour water stripper unit for further processing. From the top of the absorber column, H2S lean gas (Stream C) leaves. Steam (stream K) at 165 °C and 4.5 kg/cimg is added to stream C. Stream C was cooled up to 40 °C in cooler-1. The gas-liquid mixture leaving the cooler-1 was separated in separator-1. The process gas leaving the separator 1 (Stream D) was compressed in a compressor to push the gas for further processing. The temperature raised during compression was removed in cooler-2 by cooling up to 40 °C. The gas-liquid mixture leaving the cooler-2 (Stream E) was separated in separator-2. The liquid stream (Stream I) leaving the bottom of separator-2 was mixed with Stream G and then routed to existing sour water stripper unit for further processing. A recycle stream comprising of ammonia, H2S and water generating in Sour water stripper unit (SWSU) will comprise of remaining part of stream A The process gas, Stream F, leaving the seperator-2 is processed in adsorber column to remove traces of H2S impurity in the process gas. The process gas (Stream J) leaving the adsorber column contained H2S <10 ppmv and this has NH3 content 99.6%Wt (min.). Then adsorbent bed in adsorber column was regenerated by Ch/Air into elemental sulphur and H2S. The H2S was routed to SRU.
Impact on upstream unit: The operating pressure of the stripper can be brought back from existing 0.9 kg/cm2g to 0.7-0.8 Kg/cm2g.
The process data of Example 1 and Example 2 was shown in Table 1 and Table 2 respectively, below:

Table 1: Process data of 19 TPD plant
Thus, in a continuous recycle of the process, stream A contains NH3: 794.5 Kg/hr; H2O: 55 kg/hr; and H2S: 2.66 kg/hr.

Table 2: Process data of 31 TPD plant
Thus, in a continuous recycle of the process, stream A contains, NH3: 1176.5 kg/hr; H2O: 100 kg/hr; and H2S: 4.2 kg/hr.

Notwithstanding the appended claims, the disclosure is also defined by the following clauses: 1. A system for recovering anhydrous ammonia from a sour gas, comprising: an absorption column defined by a volume integrated therewith for washing a sour fluid by introducing an absorbent to recover a stream of sour fluid containing high ammonia and less H2S and to discharge a liquid solution of sour water containing H2S and ammonia to a stripper
at least one first cooler in fluid communication with said absorption column, wherein the first cooler is configured to receive and condense the stream of sour fluid containing high ammonia and less hydrogen sulphide H2S;
at least one first separator in fluid communication with the first cooler to generate a stream of ammonia rich sour gas and less hydrogen sulphide H2S from the condensed stream of sour fluid containing high ammonia and less hydrogen sulphide H2S introduced in the first separator, and wherein the first separator is configured to discharge a portion of liquid solution of sour water containing H2S and ammonia to the absorption column.
one or more compressors in fluid communication with the separator to receive the stream of ammonia rich sour gas and less hydrogen sulphide H2S and to compress the stream of ammonia rich sour gas and less hydrogen sulphide H2S to a predetermined high (first) pressure and high (first) temperature stream of ammonia rich sour gas and less hydrogen sulphide;
at least one second cooler in fluid communication with the compressor, wherein the second cooler is configured to cool the high pressure and high temperature stream of ammonia rich sour gas and less hydrogen sulphide H2S;
at least one second separator in fluid communication with the second cooler to generate a stream of ammonia rich sour gas and less hydrogen sulphide H2S from the condensed stream of sour fluid containing high ammonia and less hydrogen sulphide H2S introduced in the second separator, and wherein the second separator is configured to discharge a portion of liquid solution of sour water containing H2S and ammonia to the stripper; and
an adsorption column in fluid communication with the second separator, wherein the adsorption column includes an adsorption bed to allow adsorption of H2S from the stream of ammonia rich sour gas and less hydrogen sulphide H2S thereby recovering anhydrous ammonia.

2. The system as defined in clause 1, wherein the absorption column has low pressure drop internals to minimize the pressure drop resulting from the contacting of stripped sour water and NH3 rich sour gas and to maximize available contact area between the phases.
3. The system as defined in clause 1, wherein the absorption column comprises a structured packing for bed material which gives efficient mass transfer at a low pressure drop across the column.
4. The process as defined in clause 3, wherein the structured packing provides a surface area in the range of 125 m2/m3 to 350 m2/m3.
5. The system as defined in clause 1, wherein the absorbent introduced in the absorption column is water wash steam and any other suitable material to wash the sour fluid.
6. The system as defined in clause 1, wherein the stream of absorbent flows in a counter flow direction to a flow direction of the sour fluid.
7. The system as defined in clause 1, wherein the first and the second separator are selected from the group consisting of gas-liquid separators, cyclones, oil-gas separators, knock-out drums and filter separators.
8. The system as defined in clause 1, wherein the compressor is driven at least one of electrical, hydraulic, mechanical or pneumatic means.
9. The system as defined in clause 1, wherein the adsorbent is any material capable to adsorb H2S from the ammonia rich sour gas.
10. A process for recovering anhydrous ammonia from a sour gas comprising:

a) introducing NH3 rich sour gas (stream A) and stripped sour water (stream B) into an absorber column and contacting them counter-currently;
b) adding water or steam to stream C and cooling said stream C comprising sour gas leaving the absorber column in a cooler-1, wherein stream C has higher concentration of NH3 and lower concentration of H2S compared to stream A;
c) introducing a stream of gas-liquid mixture leaving the cooler-1 into a separator-1 to separate gas stream from liquid stream;
d) compressing a stream D comprising sour gas stream leaving separator-1 in a compressor followed by cooling in a cooler-2;

e) introducing a stream E comprising a stream of gas-liquid mixture leaving the cooler-2 into a separator-2 to separate gas stream from liquid stream; and
f) treating a stream F comprising gas stream leaving the separator-2 with an adsorbent bed, in an adsorbent column, to remove traces of H2S and to recover anhydrous ammonia.

11. The process as defined in clause 10, wherein the absorption column has low pressure drop internals to minimize the pressure drop resulting from the contacting of stripped sour water and NH3 rich sour gas and to maximize available contact area between the phases.
12. The process as defined in clause 10, wherein the absorption column comprises a structured packing for bed material which gives efficient mass transfer at a low pressure drop across the column.
13. The process as defined in clause 12, wherein the structured packing provides a surface area in the range of 125 m2/m3 to 350 m2/m3.
14. The process as defined in clause 10, wherein concentration of H2S in the stream A is from about 30%v to about 90%v.
15. The process as defined in clause 10, wherein stream A is introduced into the absorber column at a pressure of 0.1-0.9 kg/cm2g and at temperature of about 40-90 °C.
16. The process as defined in clause 10, wherein stream A is introduced into the absorber column at a pressure of 0.9 kg/cm2g and at a temperature of about 90 °C.
17. The process as defined in clause 10, wherein stream B is introduced into the absorber column at a pressure of less than or equal to 0.1-4 kg/cm2g and at a temperature of about 40-90 °C.
18. The process as defined in clause 10, wherein stream B is introduced into the absorber column at a temperature of about 90 °C.
19. The process as defined in clause 10, wherein stream C leaving the absorber column has a pressure of about 0.5-0.85 kg/cm2g.
20. The process as defined in clause 10, wherein water or steam is added to stream C to increase the H2S removal efficiency.
21. The process as defined in clause 10, wherein stream D leaving the separator-1 has a pressure of about 0.3-0.85 kg/cm2g.

22. The process as defined in clause 10, wherein in step b) and d) the gas stream is cooled up to 40-45 °C.
23. The process as defined in clause 10, wherein the stream of gas-liquid mixture leaving the cooler has a pressure of about 0.5-0.8 kg/cm2g.
24. The process as defined in clause 10, wherein sour gas stream leaving the separator-1 has a pressure of about 0.8 kg/cm2g.
25. The process as defined in clause 10, further comprises discharging a stream G comprising sour water from the absorption column to sour water stripper unit for further processing.
26. The process as defined in clause 10, further comprises discharging a stream H comprising liquid stream from the separator-1 to sour water stripper unit for further processing.
27. The process as defined in clause 10, further comprises discharging a stream I comprising liquid stream from the separator-2 to sour water stripper unit for further processing.
28. The process as defined in clause 10, wherein gas (stream J) leaving the adsorption column contains <10ppmv H2S and 99.6% wt (min) NH3.
29. The process as defined in clause 10, wherein purity of anhydrous ammonia is >99.6% wt.
ADVANTAGES
• The process is useful for recovering valuable NH3 in anhydrous form
• The process is viable to reduce H2S impurity from 10%V to <10 PPMV and to increase NH3 purity from 30%V to at least 99.6%V.
• Use of low pressure drop internals will reduce the upstream stripper operating pressure.
• Adsorbed H2S in adsorbent bed can be regenerated by oxidation with air/02 to produce S and H2S. The H2S is routed to SRU.
• NH3 stripper can be operated at < 0.8 kg/cm2g. This results in steam savings in reb oiler.
• NOx and SOx emissions will reduce significantly.
• Increase in SRU capacity due to removal of NH3 from SRU feed gases.

We Claim:
1. A system for recovering anhydrous ammonia from a sour gas, comprising:
an absorption column defined by a volume integrated therewith for contacting NH3 rich sour gas counter-currently with wash water;
at least one cooler-1 in fluid communication with said absorption column, wherein the first cooler is configured to receive and condense a sour gas leaving the absorption column;
at least one first separator-1 in fluid communication with the first cooler to separate a stream of gas-liquid mixture leaving the cooler-1 into a gas stream and liquid stream;
one or more compressors in fluid communication with the separator-1 to receive and compress the gas stream leaving the cooler-1;
at least one second cooler-2 in fluid communication with the compressor, wherein the second cooler is configured to cool and condense the gas stream leaving the compressor;
at least one second separator-2 in fluid communication with the second cooler to separate a stream of gas-liquid mixture leaving the cooler-2 into a gas stream and liquid stream; and
an adsorption column in fluid communication with the second separator-2, wherein the gas stream leaving the second separator-2 is contacted with an adsorbent bed to remove traces of H2S from the said gas stream and to recover anhydrous ammonia.
2. The system as claimed in claim 1, wherein the absorption column comprises low pressure drop internals to minimize the pressure drop resulting from the contacting of wash water and NH3 rich sour gas and to maximize available contact area between said stripped sour water and NH3 rich sour gas.
3. The system as claimed in claim 1, wherein the absorption column comprises a bed and a structured packing for the bed material.
4. The process as claimed in claim 3, wherein the structured packing provides a surface area in the range of 125 m2/m3 to 350 m2/m3.

5. The system as claimed in claim 1, wherein the first and the second separator are selected from a group comprising gas-liquid separators, cyclones, oil-gas separators, knock-out drums and filter separators.
6. The system as claimed in claim 1, wherein the compressor is driven at least one of electrical, hydraulic, mechanical or pneumatic means.
7. The system as claimed in claim 1, wherein the adsorbent is any material capable to adsorb H2S from the ammonia rich sour gas.
8. A process for recovering anhydrous ammonia from a sour gas comprising:
a) introducing NH3 rich sour gas (stream A) and wash water (stream B) and contacting them counter-currently in an absorber column;
b) cooling a stream C comprising sour gas leaving the absorber column in a cooler-1, wherein stream C has higher concentration of NH3 and lower concentration of H2S compared to stream A;
c) introducing a stream of gas-liquid mixture leaving the cooler-1 into a separator-1 to separate gas stream from liquid stream;
d) compressing a stream D comprising sour gas stream leaving separator-1 in a compressor followed by cooling in a cooler-2;
e) introducing a stream E comprising a stream of gas-liquid mixture leaving the cooler-2 into a separator-2 to separate gas stream from liquid stream; and
f) treating a stream F comprising gas stream leaving the separator-2 with an adsorbent bed, in an adsorbent column, to remove traces of H2S and to recover anhydrous ammonia.

9. The process as claimed in claim 8, wherein the absorption column has low pressure drop internals to minimize the pressure drop resulting from the contacting of the wash water and NH3 rich sour gas and to maximize available contact area between the phases.
10. The process as claimed in claim 8, wherein the absorption column comprises a structured packing for bed material which gives efficient mass transfer at a low pressure drop across the column.
11. The process as claimed in claim 10, wherein the structured packing provides a surface area in the range of 125 m2/m3 to 350 m2/m3.

12. The process as claimed in claim 8, wherein concentration of ammonia in the stream A is from about 30%v to about 90%v, and concentration of H2S in stream A is maximum of about 10%v
13. The process as claimed in claim 8, wherein stream A is introduced at a pressure of 0.1-0.9 kg/cm2g and at temperature of about 40-90 °C.
14. The process as claimed in claim 8, wherein stream B is introduced at a pressure of less than or equal to 0.1-4 kg/cm2g and at temperature of about 40-90 °C.
15. The process as claimed in claim 8, wherein in step b) and d) the gas stream is cooled up to 45 °C.
16. The process as claimed in claim 8, wherein recovery of ammonia from the sour gas is at least 99.9%.
17. The process as claimed in claim 8, wherein purity of recovered anhydrous ammonia is >99.6% wt.
18. The process as claimed in claim 8, wherein H2S content in the recovered anhydrous ammonia is less than 10 PPMV.